Distribution and importance of wax esters in marine copepods and other zooplankton

Deep-Sea Research, 1971, Vol. 18, pp. 1147 to 1165. Pergamon Press. Printed in Great Britain.

Distribution and importance of wax esters in marine eopepods and other zooplankton*

RICHARD F. LEE,I" JED HIROTA a n d ARTHUR M. BARNETT

(Received 21 June 1971 ; accepted 23 June 1971)

Abstract--Zooplankton were captured for detailed lipid analyses from known depth intervals in opening-closing nets and in midwater trawls to 2500m at a station in the subtropical Pacific. Copepods were also collected from the upper 500 m of a second subtropical and a temperate station in the Pacific, and a station in the Arctic.

At the subtropical station wax esters were a minor part of the total lipid (less than 107o) and triglycerides were the most important lipid of many copepods inhabiting the upper 325 m, whereas wax esters were the main lipid constituent (over 50 70 of the lipid) and triglycerides were a minor lipid component for all copepods examined from depths below 625 m. The 325-625 m depth interval appeared to be a transition zone. Wax esters also comprised over 40 70 of the lipid in most of the temperate and polar calanoids examined. Triglycerides tended to be replaced by wax esters as the main lipid component in copepods from deep water or cold water.

All genera examined belonging to the families CalanJdae, Euchaetidae, Lucicutiidae, Hetero- rhabdidae, and Augaptilidae had greater than 20 ~ of their lipid as wax esters. The genera examined from these families generally occur in deep water or near-surface cold waters. Members of the families Candaciidae and Pontellidae contained less than 10 70 wax ester. They are primarily found at shallow depths from tropical to temperate waters. The families Eucalanidae, Aetideidae, Scolecithtricidae, and Metridiidae contained genera with varying amounts of wax esters. These families have both genera and species which inhabit various depth and temperature ranges.

Experiments on the rate of lipid utilization for periods up to one week generally showed a slow decrease in the percentage lipid of the dry weight. Detailed lipid analyses of Gaussia princeps during starvation showed triglyceride was utilized while wax esters remained relatively unchanged.

The depth and latitudinal distribution of lipid in marine copepods may generally be explained on the basis of temperature or the temporal distribution, relative abundance, and rate of supply of food. However, there are some exceptions, and the importance of taxonomic affinity cannot be ignored.

I N T R O D U C T I O N

THE BIOCHEMICAL composition of surface-living zooplankton has been investigated by a number of workers (ACKMAN and EATON, 1967; CORNER and COWEY, 1968; CLrLmN and MORRIS, 1969, 1970; FISCHER, 1962; JEFFREY, BOTTINO and R~ISER, 1966; LINFORD, 1965; LIa~rLEPAGE, 1964; RAgOUt, AUSTIN and LINFORD, 1964, 1966a; RAYMOrCr, and CONOV~, 1961 ; RAYMONT, SRI~aVASAGAM and RAYMOr~% 1969; REEVE, RAYMOrCr and RAYMOrCr, 1970; SIPOS and ACKMAN, 1968 ; VINOGRADOVA, 1960; YAMADA, 1964). Little information is available for mesopelagic zooplankton (CULgIN and MORRIS, 1969; RAYMONT, AUSTIN and LINFORD, 1966b; RAYMONT, SFJmVASAGAM and RAYMONT 1969), and none is available for bathypelagic forms.

Previous studies of lipids in marine food webs showed that wax esters are an important lipid component of the copepods Calanus helgolandicus and Gaussia princeps (LEE, NEVENZEL and PAFFENI-I/JFER, 1970, 1971). Triglycerides are the usual reserve lipid in most vertebrates and invertebrates which have previously been examined (BARTLEV, BIRT and BANKS, 1968; GtrNSTONE, 1967). Notable exceptions are toothed whales, certain mesopelagic fish, and a few marine invertebrates which

*Contribution from the Scripps Institution of Oceanography. tS6Tipps Institution of Oceanography, La Jolla, California 92037

1147

1148 RICHARD F. LEE, JED HIROTA and ARTHUR M. BARNETT

have large amounts of wax esters (NEVENZEL, 1970). In order to extend our knowledge of the distribution of wax esters in marine organisms, we have collected and analyzed material from several depth intervals down to 2500 m. This work yielded information on both the composition and rate of utilization of lipid by calanoid copepods collected from different depths and locations. In addition some lipid measurements on fish and zooplankton other than copepods are given. We attempt to relate the amount and composition of lipid in organisms to their vertical and latitudinal distributions.

METHODS

Zooplankton samples from several depth intervals were collected using open and closing bongo nets of 0.333 mm mesh (McGOWAN and BROWN, 1966) and a 3-m Isaacs-Kidd midwater trawl of 0.505 mm mesh cod-end on two cruises of the R.V. Melville (Dec. 15-19, 1969 and Mar. 25-29, 1970). The cod-end pieces of bongo nets were non-filtering plastic cups which assisted in the retrieval of live animals. The samples were taken in the Valero Basin, about 450 km southwest of San Diego beyond the continental shelf (31°N, 119°W). Bongo nets were used to sample during both day and night from the surface to 1000 m in about 200 m intervals, while 500 or 1000 m intervals were used to sample from 1000-2500 m. A 2500 m time-depth recorder was used to determine the depth interval sampled. The terminology used here for pelagic depth zones are those described by HEDGEPETH (1957): epipelagic, 0-250 m; mesopelagic, 250-1000 m; bathypelagic, 1000-4000 m.

Only live organisms longer than 2 mm were chosen for analysis. They were sorted from the plankton samples into homogeneous groups as to species and stage or sex as soon as possible after capture. Ordinarily, sorting required less than about 6 hr. Some individuals of each group were preserved for identification, the remainder were used for lipid extraction. References used for identification of copepods were BRODSKII (1950), (;RICE (1963), HULSEMANN (1966), MORI (1964), ROSE (1933), and SEWELL (1947).

Several specimens of large bathypelagic copepods (Megacalanus longicornis, Gaussiaprinceps and Gaetanus brevicornis) were maintained in the laboratory at sea to study the rate of lipid utilization during conditions o f ' starvation '. These copepods were kept in about 10 liters of surface seawater passed through 35/z nitex mesh and cooled to 5°C. It was assumed that the fraction of particulate organic matter passing through 35 /~ nitex was unimportant to these large carnivorous copepods. All experiments were carried out in the dark. Successive groups of each species were removed at appropriate time intervals for lipid analysis. All lipid components were measured for one group of Gaussia princeps females while only the total lipid was determined for the other groups.

Lipid extraction was in chloroform-methanol (2: 1 v/v). After extraction of the lipid, all work was carried out under nitrogen. The lipid was weighed, and for those experimental groups from which more than 6 mg of lipid was available, the lipid was fractionated on a silicic acid column, eluting the different lipid classes with solvents of increasing polarity as described by NEVENZEL, RODEGKER and MEAD, (1965), and then weighed. The procedure for analyzing the five different lipid fractions (hydrocarbons, wax esters, triglycerides, phospholipids, and polar lipids) by gas chromatography is given in a previous paper (LEE, NEVENZEL and PAFFENHOFER, 1971). Hydrogenation of

Distribution and importance of wax esters in marine copepods and other zooplankton 1149

fatty acid mixtures was carried out to verify identifications. When less than 6 mg of total lipid was available, the lipids were separated by thin-layer chromatography and the amounts of wax esters and triglycerides were determined spectrophotometrically by the procedure of ARMENTA (1964) using dichromate digestion and measurement at 350 mt~.

In addition to these samples, copepods were collected with plankton nets from depths less than 500 m in waters off San Diego, California; Vancouver, British Columbia; and Arctic Ice Sta. T-3. Treatment and analysis of the organisms were similar to that described above, except that the arctic copepods were frozen before lipid extraction and analysis.

RESULTS

Distribution of lipids The vertical distributions of calanoid copepod genera for which there were lipid

determinations were obtained from a single daytime and four night-time bongo net tows (Table 1). Where more than one species of a genus were present, the distribution of only those species analyzed are given, and they are distinguished by name or body length. The night sample data indicated the minimum depths inhabited by the organisms while the day sample showed which organisms always remained in the upper 250 m.

Table 1. Vertical distribution of copepods* taken during Melville II.

Time-depth 0-250 m 0-250 rn 250-400 m 425-750 m 800-950 m

Genus Day Night Night Night Night (Number of copepods per 1600 m 3)

Present in upper 250 m both day and night Calanus > 400 > 800 6 1 0 Eucalanus > 800 >8000 > 500 > 100 16 Rhincalanus ~> 800 >4000 24 18 8 Euchirella (rostrata) 8 2 0 0 0 Candacia > 600 12 0 1 0 Present in upper 250 m at night, generally absent during the day Euchirella (galeata and 0 25 18 6 0

pulchra) Chirundina 0 1 0 0 0 Undeuchaeta 0 20 5 9 4 Pseudochirella 0 1 0 1 1 Scottocalanus 0 36 2 4 1 Pleuromamma 16 > 800 130 49 21 Gaussia 0 10 1 12 15 Absent from upper 250 m both day and night Megacatanus 0 0 0 1 0 Bathycalanus 0 0 0 1 1 Gaetanus (unicornis) 0 0 6 6 7 Paraeuchaeta 0 0 50 42 18 Amallothrix 0 0 3 0 0 Metridia (longicornis and 0 0 33 19 4

princeps) Lucicutia > 4 m m 0 0 0 2 33 Disseta > 5 m m 0 0 8 33 34 Heterorhabdus > 5 m m 0 0 0 54 22 Euaugaptilus 0 0 9 33 27

*Only the adult copepods greater than 2 m m which were analyzed for lipid content are shown.

Tabl

e 2.

L

ipid

com

posi

tion

of c

alan

oM c

opep

ods

from

var

ious

dep

th i

nter

vals

col

lect

ed d

urin

g tw

o cr

uise

s of

the

R.V

. M

elvi

lle.

Spec

ies

Lip

id p

er

indi

vidu

al

Lip

id

Trig

lyce

ride

W

ax e

ster

(m

g)

Day

~nig

ht

(% d

ry w

eigh

t)

(% t

otal

lip

id)

(% t

otal

lip

id)

Sam

ple

dept

h in

terv

al:

1-10

m

Cal

anus

gra

cilis

~

0.08

ni

ght

26

17

21

Cal

anus

rob

ustio

r f~

0-

03

nigh

t 8

3 21

U

ndeu

chae

ta b

ispi

nosa

~-

0.16

ni

ght

21

30

1 U

ndeu

chae

ta b

ispi

nosa

~

O. 1

4 ni

ght

19

33

0 C

anda

cia

curt

a f~

0-

01

nigh

t 3

10

4 C

anda

cia

aeth

iopi

ca f

~ 0.

02

nigh

t 9

11

1 Sa

mpl

e de

pth

inte

rval

: 0-

250

m

Rhi

ncal

anus

nas

utus

~-

O. 1

2 da

y 42

9

69

Euc

hire

lla r

ostr

ata

9, ~

0-

14

day

21

37

abse

nt

Euc

hire

lla s

p. 3

~

0.13

ni

ght

15

28

abse

nt

Scot

toca

lanu

sper

seca

ns ~

0-

10

nigh

t 8

24

abse

nt

Sam

ple

dept

h in

terv

al:

250-

500

m

Euc

alan

us s

p. 1

(~,

C-V

) 0.

08

day

31

42

1 G

aeta

nus

unic

orni

s ~

0-21

ni

ght

16

27

11

Euc

hire

lla g

alea

ta f

~ 0.

06

nigh

t 4

14

abse

nt

Euc

hire

lla p

ulch

ra ~

0.

05

day

12

18

2 E

uchi

rella

spp

. (C

-V)

0.16

da

y 18

26

1

Scot

toea

lanu

s sp

. 1

¢ 0.

11

day

12

32

4 Sc

otto

cala

nus

spp.

c?

O

" 11

day

16

36

2 M

etri

diap

rinc

eps

~ 0.

10

nigh

t 12

4

41

Ple

urom

amm

a ab

dom

inal

is

~ 0-

03

day

16

27

2 P

leur

omam

ma

quad

rung

ulat

a (c

~, C

-V)

0.09

da

y 36

39

3

Ple

urom

amm

a sp

p.

~ 0"

03

day

16

31

3 P

ieur

omam

ma

xiph

ias

~ 0.

06

day

16

22

14

Ple

urom

amm

a xi

phia

s ~-

0"

06

day

14

25

4 P

leur

omam

ma

xiph

ias

~ O

. 13

day

30

31

2 D

isse

ta m

axim

a ~

1.30

ni

ght

45

10

67

Dis

seta

sp.

2 ~

0.

10

nigh

t 10

7

20

Sam

ple

dept

h in

terv

al:

325-

625

m

Gae

tanu

s sp

p. ~

0.

43

day

23

29

49

Euc

hire

lla g

alea

ta ~

- 0.

38

day

20

41

abse

nt

Euc

hire

lla s

pp.

(C-V

) 0-

31

day

31

55

9

Chi

rund

ina

stre

etsi

~-

O" 1

2 da

y 12

23

C

hiru

ndin

a st

reet

si 6

0-

16

day

17

35

Und

euch

aeta

bis

pino

sa ~

0"

11

day

18

38

Par

aeuc

haet

a sp

p. ~

0"

71

day

42

12

Par

aeuc

haet

a sp

p. ¢

, 6'

1.

13

day

45

4 P

arae

ucha

eta

spp.

(C

-V)

0"65

da

y 46

2

Met

ridi

apri

ncep

s ~-

0.

38

day

27

12

Met

ridi

a pr

ince

ps

6'

0" 1

4 da

y 18

4

Met

ridi

a sp

p. 6

0.

28

day

35

2 M

etri

dia

spp.

~

0-39

da

y 40

5

Sam

ple

dept

h in

terv

al:

325-

625

mm

P

leur

omam

ma

xiph

ias

c~

0"08

da

y 19

32

G

auss

ia p

rinc

eps

(C-I

ll)

0"30

da

y 22

6

Gau

ssia

pri

ncep

s (C

-IV

) 0.

80

day

53

17

Dis

seta

max

ima

~-

0.44

da

y 29

4

Het

eror

habd

idae

spp

. 6'

0-

84

day

39

5 E

uaug

aptil

us s

p. ~

0'

30

day

50

2 S

ampl

e de

pth

inte

rval

: 62

5-75

0 m

P

arae

ucha

eta

rubr

a? (

C-V

) 0-

29

day

43

5 P

arae

ucha

eta

rubr

a ?

(C-I

V)

0-17

da

y 60

3

Met

ridi

a pr

ince

ps

~-

0-30

da

y 24

5

Luci

cuti

a bi

corn

utum

~-

O

" 14

day

31

12

Dis

seta

max

ima

~-

0"20

da

y 27

4

Dis

seta

spp

. 6'

0"

22

day

39

1 D

isse

ta s

pp.

6'

0"63

da

y 36

2

Sam

ple

dept

h in

terv

al:

750-

1600

m

Bat

hyca

lanu

s br

adyi

~-

31 "1

0 ni

ght

59

11

Gae

tanu

s sp

p. (

C-I

II)

0"13

ni

ght

59

1 H

eter

orha

bdus

sp.

1 ~

0.

11

nigh

t 61

1

Aug

apti

lida

e sp

p. ~

, 6'

0.

15

nigh

t 32

1

Aug

apti

lida

e sp

p. ~

0.

63

nigh

t 40

1

Sam

ple

dept

h in

terv

al:

1300

-250

0 m

G

aeta

nus

spp.

~

--

nigh

t 47

4

Luci

cuti

a sp

p. ~

, 6'

0"

07

nigh

t 15

1

Sam

ple

dept

h in

terv

al:

0-19

00 m

(Is

aacs

-Kid

d M

idw

ater

Tra

wl)

M

egac

alan

us lo

ngic

orni

s ~,

~

2"70

M

egac

alan

us p

rinc

eps

9~

2.60

G

aidi

us s

p. 1

~

2"50

G

aeta

nus

brev

icor

nis

~ 1"

10

Euc

hire

lla s

p. 1

~,

6 0"

75

36

39

49

30

20

2 5 16 6 31

abse

nt

7 14

70

70

68

44

22

63

66 2 72

52

51

59

59

67

82

72

63

69

63

78

77

80

82

61

72

62

50

49

51

51

44

abse

nt

t~r 4 8 Q

O

Tab

le 2

. L

ipid

com

posi

tion

of

cala

noid

cop

epod

s fr

om

var

ious

dep

th i

nter

vals

col

lect

ed d

urin

g tw

o cr

uise

s o

f th

e R

.V.

Mel

vil

le.-

--co

nt.

Lipi

d pe

r in

divi

dual

Li

pid

Trig

lyce

ride

W

ax e

ster

Sp

ecie

s (n

ag)

Day

~nig

ht

(~o

dry

wei

ght)

(~

to

tal

lipi

d)

(~

tota

l li

pid)

Pse

udoc

hire

lla sp

. 1

~ 0.

13

6 19

4

Par

aeuc

haet

a ba

rbat

a ~

1"90

47

6

61

Par

aeuc

haet

a ru

bra

~ 1

"60

57

11

65

Val

divi

ella

sp.

1 ~

2"20

53

7

63

Val

divi

ella

sp.

2 ~

3.10

56

9

59

Val

divi

ella

sp.

3 $

3-40

54

11

60

A

mal

loth

rix

spp.

~

7.30

59

8

71

Gau

ssia

pri

ncep

s ~?

1 "

30

26

18

49

Luci

cutia

aur

ita?

~-

0.58

47

12

52

Lu

cicu

tia s

p. 1

$

0"90

52

14

50

D

isse

ta s

p. 1

~

0-12

47

2

71

Eua

ugap

tilus

sp.

1 9

0-

36

53

18

51

Eua

ugap

tilus

sp.

2 $

2.

10

52

2 68

to

0 ).


The data for adult copepods appeared to generate three patterns: (1) members of five genera were found at relatively high abundance in the epipelagic zone both day and night, (2) copepods from seven genera apparently migrated into this zone at night and (3) copepods from ten genera were never in this zone. Pleuromamma was con- sidered in the group which migrated out of the surface during the day, their numbers decreasing approximately 50-fold. There were a few genera placed into respective groups on the basis of very few specimens. They are: Chirundina, Pseudoehirella, Megacalanus, Bathycalanus, and Amallothrix. However, the depth distribution in the literature for these genera (BRODSKn, 1950; SZWELL, 1947) are consistent with our groupings.

The amount of total lipid and the proportion of triglyceride and wax esters from copepods captured on the two cruises of the R.V. Melville are given in Table 2. The taxa are listed according to the depth of capture. The depths from which the organisms in the midwater trawl tows were taken are unknown because the sampler had no closing device. The vertical distribution of these copepods must be inferred from the bongo net tows and from the literature.

The lipids ranged from 3 ~ of the body dry weight in Candacia curta, a near- surface copepod, to 61 ~ in Heterorhabdus sp. 1, a deeper-living form. Triglycerides comprised from 1 ~o of the total lipid in many lower mesopelagic (525-1000 m) and bathypelagic forms to over 40~o in Euchirella and Eucalanus, which usually inhabit shallower depth. Wax esters were absent or low in most copepods captured above 500 m. A transition occurred between 325 and 625 m where the percentage of wax esters was highly variable. Below 625 m wax esters comprised well over 50 ~ of the lipid. The differences in lipid composition were more apparent when the copepods were divided into three groups based on the depths which they inhabited (Tables 1 and 3). The larger copepods belonging to the genera Gaidius and Valdiviella were captured by the midwater trawl but not by the bongo net, therefore they were not included in the statistical analyses described below. The median value of the lipid as a percentage of dry weight in Group 3 was over twice either median in Groups 1 or 2. The median value of triglyceride as a percentage of total lipid doubled from Group 1 to Group 2 and then decreased sevenfold from Group 2 to Group 3. The median value of wax ester as a percentage of total lipid was the same in Groups 1 and 2 but increased over 25-fold in Group 3. In all three lipid categories, only the median of Group 3 was significantly different from those of Groups 1 and 2 (probability of no significant difference less than 0.05, by a multiple comparison test for unequal sample sizes; NEMENYI, 1963). For wax esters or triglycerides as a percentage of body dry weight, the results of the same statistical tests were similar except that the median of triglyceride in Group 3 was not significantly different from that of Group 1. This indicated that most of the increase of lipid with increased depth was due to the addition of wax esters. Thus, it is apparent that the lipid and wax esters are higher and triglycerides are lower in deeper-living copepods.

The lipid composition of copepods from other areas indicated that those organisms from higher latitudes have a greater percentage of total lipid and wax esters than those copepods from lower latitudes (Table 4). The high content of wax esters in copepods from the Arctic should especially be noted.

A pattern emerges from the vertical (Table 2 and 3) and latitudinal (Table 4) distributions of the copepods which were analyzed. All genera belonging to the

Tab

le 3

. T

he m

edia

ns a

nd r

ange

s o

f th

e li

pid,

tri

glyc

erid

es,

and

wa

x es

ters

in

cope

pods

fro

m d

iffe

rent

dep

th i

nter

vals

.

Lipi

d Tr

igly

ceri

de

Wax

est

er

Gen

era

Gro

up

( % o

f dr

y w

eigh

t)

( % o

f li

pid)

( %

of

lipi

d)

exam

ined

F

amily

1.

Nea

r-su

rfac

e co

pepo

ds

0-25

0 m

, da

y-ni

ght

8 gr

oups

ana

lyze

d

III.

II.

Mig

rati

ng c

opep

ods

0-25

0 m

, ni

ght

only

; 25

gro

ups

anal

yzed

Dee

p-li

ving

cop

epod

s ab

sent

in

0-25

0 m

. 40

gro

ups

anal

yzed

med

ian

18

14

2' 5

C

alan

us

Euc

alan

us

rang

e 3-

42

3-42

0-

69

Rhi

ncal

anus

E

uchi

rella

C

anda

cia

med

ian

18

29

2.5

Euc

hire

lla

Chi

rund

ina

rang

e 4-

53

6-55

0-

72

Un

deu

cha

eta

P

seud

ochi

rella

Sc

otto

cala

nus

Ple

urom

amm

a G

auss

ia

med

ian

40

4 63

rang

e 10

-61

1-29

11

-82

Meg

acal

anus

B

athy

cala

nus

Gae

tanu

s P

arae

ucha

eta

Am

allo

thri

x M

etri

dia

Luci

cutia

D

isse

ta

Het

eror

habd

us

Eua

ttgap

tilus

Cal

anid

ae

Euc

alan

idae

E

ucal

anid

ae

Aet

idei

dae

Can

daci

idae

Aet

idei

dae

Aet

idei

dae

Aet

idei

dae

Aet

idei

dae

S¢o

leci

thri

cida

e M

etri

diid

ae

Met

ridi

idae

Cal

anid

ae

Cal

andi

ae

Aet

idei

dae

Euc

haet

idae

S

cole

cith

rici

dae

Met

ridi

idae

L

ucic

utid

ae

Het

eror

habd

idae

H

eter

orha

bdid

ae

Aug

apti

lida

e

4x

m

Z

Tab

le 4

. T

he l

ipid

com

posi

tion

and

wei

ght

of

cala

noid

cop

epod

s fr

om

sub

-tro

pica

l,

tem

pera

te a

nd a

rcti

c re

gion

s.

Lipi

d pe

r an

imal

Li

pid

Trig

lyce

ride

(m

g)

(% o

f dr

y w

eigh

t)

(% o

f li

pid)

W

ax e

ster

(%

of

lipi

d)

I.

Sub

trop

ical

lat

itud

es

La

Joll

a, C

alif

orni

a (3

3°N

, 11

7°W

; up

per

50 m

) V

aler

o B

asin

(31

°N,

l19°

W;

uppe

r 25

0 m

) C

alan

us g

raci

lis ~

0'

08

26

17

21

Cal

amus

hel

gola

mdi

cus*

~

0.04

14

4

33

Cal

amus

robu

stio

r ~-

0'

03

8 3

21

Euc

alam

us sp

. 1

~,

~ 0"

08

31

42

1 R

hinc

alan

us n

asut

us*

~-

0'06

37

1

46

Euc

hire

lla r

ostr

ata

~-

O" 1

4 21

37

0

Euc

hire

lla s

p. 3

~

0.13

15

28

0

Euc

haet

a ac

uta

? ~

t --

8

37

Euc

haet

a m

edia

* ~

--

--

6 42

C

anda

cia

curt

a ?

0"01

3

10

4 C

anda

cia

aeth

iopi

ca ~

- 0"

02

9 11

I

Labi

doce

ra t

risp

inos

a ~

0"03

14

17

2

II.

Tem

pera

te l

atit

udes

V

anco

uver

, B

riti

sh C

olum

bia

(50°

N,

123~

W;

uppe

r 20

0 in

) C

alam

us p

lum

chru

s ~

0.41

59

7

86

Gae

tanu

s in

term

ediu

s ~

0"06

25

21

5

Euc

haet

a ja

poni

ca ~

0.

44

41

18

54

III.

P

olar

lat

itud

es

Arc

tic

Sta

. T

-3 (

84°N

, 10

6°W

; up

per

500

m)

Cal

anus

finm

arch

icus

~-

0.

22

50

11

63

Cal

anus

hyp

erbo

reus

$

5-90

73

2

92

Euc

haet

a sp

. (C

-V)

0"16

31

4

61

Met

ridi

a lo

nga

~ 0.

06

34

2 62

O"

¢)

0 ga,

S 0 0 ~r

0

*Cop

epod

s de

scri

bed

as b

orea

l sp

ecie

s by

BR

OD

SKII

(195

0) a

nd

Ros

e (1

933)

. ~

Not

ana

lyze

d.


copepod families Calanidae, Euchaetidae, Lucicutiidae, Heterorhabdidae, and Augaptilidae contained appreciable amounts of wax esters (that is, more than 20 70 of the total lipid). The genera examined from these families generally occur in deep waters or in near-surface cold waters (exceptions: Calanus gracilis and C. robustior, which occur in near-surface warm and temperate waters). All genera examined from the families Candaciidae and Pontellidae, were low in wax ester content (that is, less than 10 ~o of the total lipid). These copepods are found primarily at shallower depths from tropical to temperate waters. The families Eucalanidae, Aetideidae, Scolcith- ricidae, and Metridiidae contained genera with varying amounts of wax esters. These families have both genera and species which exhibit a relatively greater variability in their vertical and latitudinal distributions.

Within a genus, all species usually have over 20 ~ or less than 10 ~ of wax esters (exceptions: Gaetanus, Undeuchaeta, Pleuromamma).

Lipid composition data

The percentage of each lipid type was about the same for each of four species (Table 5). Wax esters were the dominant lipid type by a factor of about three for each

Table 5. Lipid composition of four species of copepods.

Gaetanus Gaussia Rhincalanus Lipid fraction brevicornus Amallothrix sp. princeps nasutus

(Weight ~ )

Hydrocarbons 3 2 1 6 Wax esters 58 74 49 69 Triglycerides 13 13 18 9 Polar lipids 9 3 15 5

(includes mainly sterols with some free fatty acids and pigments)

Phospholipids 17 8 17 11 Total lipid 30 59 26 42

(per cent of dry weight)

species. Neutral lipids (wax esters and triglycerides) accounted for approximately 70 700 of the total lipid, while the structural lipids (phospholipids and sterols) amounted to less than 25 ~ of the lipid. Most of the hydrocarbons found were pristane and a series of saturated, straight-chain hydrocarbons both of which had previously been reported by BLUMER, MULLIN and THOMAS (1964). However, the relatively high proportion of hydrocarbon in Rhincalanus nasutus was due to the presence of 21 : 6 hydrocarbon, a lipid not found in the other three copepods. This near-surface herbivore may be linked more closely with phytoplankton, whose major hydrocarbon is the 21:6 compound (BLUMER, MULLIN and GUILLARD, 1970; LEE and LOEBLICH, 1971; LEE, NEVENZEL, PAFFENH/JFER, BENSON, PATTON and KAVANAGH, 1970).

The fatty acid composition of wax esters, triglycerides, and phospholipids showed that the most abundant homologs were 16: 0, 16: 1, 18: 1, 20: 5 and 22: 6. The 16: 0 fatty acid appeared to be more abundant in triglycerides and phospholipids than in wax esters, whereas 16:1 and 18:1 were more abundant in wax esters and triglycerides


e~

h

.% ~a

~6

c-I

. - , 6

e n ¢',1

( ' q q n t 'q c q

~D

c-I

o cb *-'

r . l . ~ ¢-,I I"-

,"~ O O t"q ,,~t- ee~ ,et"

O tt~

~D ee~ t"q

~ e q oo~,D ¢ ' - I ~

O

1158 RICHARD F. LEE, JEO HIROTA and ARTHUR M. BARNETT

than in phospholipids. The 20: 5 fatty acids were over 5 % of the total in each lipid class for all copepods except Amallothrix, and they tended to be highest in the phospholipids. The 22:6 fatty acid in phospholipids of all species was 17-49 %. The other polyunsaturated fatty acids contributed less than 5 % of the total of any one lipid class in all species. Rhincalanus nasutus had a composition most different from the other three species, especially in the 14: 0, 15:1, 16: 0, 16: 1, and 16: 3 fatty acids.

In contrast to the relatively high occurrence of polyunsaturation in fatty acids, the main alcohol constituents of wax esters were saturated or mono-unsaturated. The most abundant alcohol of all copepods (except in Amallothrix, for which there was no analysis) was 1-hexadecanol (16:0 alcohol, 45-55 %). The 18:1 alcohol was important in Gaussia princeps (12 %) and Gaetanus brevicornis (11%), but only a trace was found in Rhincalanus nasutus. The difference between the fatty acid and alcohol composition of R. nasutus and those of the deeper-living Gaetanus brevicornis and Gaussia princeps is probably a result of the phytoplankton in the diet of Rhincalanus nasutus (LEE, N~VENZEL and P.~a~F~NHrFER, 1970).

Utilization o f lipid during starvation

There was a very slow decrease in the lipids of each of the copepod groups for one to eight days of starvation (Table 7). The percentage of the starting lipid lost per unit

Table 7. Lipid utilization rates* o f unfed mesopelagic and bathypelagic calanoid copepods.

Lipid loss (% decrease of that found at

Duration of the beginning Starvation Lipid of each Lipid loss

Species (hr) (~o dry weight) time interval) (~o hr -1)

Gaussia princeps 0 26.3 - - - - (females) 48 23.1 12.2 0"25

84 21.9 16.7 0.20 0 29.3 - -

120 23.1 21.2 0.18 198 21.2 27.6 0.14

Gaussia princeps 0 28.0 - - - - (males) 120 17.0 32-1 0.27

198 16.1 35-3 0.18 Gaussia princeps 0 36.8 - - - -

(copepodite V) 84 34.4 6-6 0.08 0 41 "7 - - - -

120 35.5 14.8 0"12 198 34-2 18.0 0.09

Megacalanus 0 34.2 - - - - longicornis 48 27.7 19"0 0.40 (females) 0 34.8 - - - - !

30 28.1 19.2 0-64 Gaetanus brevicornis 0 33"3 - - - -

(females) 30 22.9 31.2 1-04

*All values represent means of a group of copepods sacrificed at each time interval.


time decreased with increasing duration of starvation (Table 7, last column). Gaussia princeps copepodite V lost lipid at about half the rate of the adults. Gaetanus brevicornis had the most rapid loss followed by Megacalanus longicornis. Only triglycerides of the various lipid types were used by G. princeps during the starvation experiment (Table 8).

Table 8. Changes in the lipid composition, total lipid, and dry weight of adult Gaussia princeps during starvation (tzg).

Duration of the experiment (hr) 0 80 120

Hydrocarbons 13 12 24 Wax esters 637 768 732 Triglycerides 234 108 24 Polar lipids 195 120 276 Phospholipids 221 192 144 Total lipid per copepod 1300 1200 1200 Dry weight per copepod 4900 5500 5200

Lipids of other zooplankton

Analyses of zooplankton other than copepods captured in tows taken to 2500 m showed the presence of appreciable amounts of wax esters in organisms from diverse phyla (Table 9). The two species of chaetognaths (Eukrohnia spp. ?) which we collected

Table 9. Various zooplankton and micronekton taken in a 3-m Isaacs-Kidd midwater trawl from 2500 m.

Triglycerides Wax ester Lipid (% of total ( % of total

Taxonomic group (% of dry weight) lipid) lipid)

Alciopidae sp. 55 11 76 (Polychaeta) Gammaridae sp. 57 13 73 (Amphipoda) Hyperiidae sp. 7 17 21 (Amphipoda) Gnathophausia sp. 42 12 69 (Mysidacea) Gennadas sp. 2l 35 10 (Decapoda) Chaetognatha sp. 1 38 12 34 Chaetognatha sp. 2 40 11 71 pteropod 5 8 absent Oegopsidae sp. 23 6 27 (Cephalopoda) Argyropelecus sp. - - 7 22 (Stemoptychidae) Stomias atriventer - - 32 9 (Stomiatidae) Cyclothone sp. 1 22 16 53 (Gonostomatidae) Cyclothone sp. 2 13 22 18


both possessed orange pigments that are characteristic of deep water chaetognaths (HARDY, 1958).

A study of the gut contents of several fish in the families Myctophidae, Sternopty- chidae, Stomiatidae and Gonostomatidae showed that copepods such as Calanus, Rhincalanus, and Metridia comprised part of their food.

DISCUSSION

It must be emphasized here that all interpretations and conclusions are based on results derived from analyses of copepods and other organisms longer than about 2 mm. Whether similar patterns exist in the smaller size fractions of zooplankton is not known at this time.

The effect of seasonal variations in lipid content on our results is unknown. It seems to be important for polar organisms (LITTLEPAGE, 1964). No substantial differences were noted in our studies of the lipid composition of the same copepod species examined in December 1969 and the following March.

Studies of crustaceans and chaetognaths have suggested that protein may have an important energy reserve function in addition to lipid (RAVMONT, AUSTIN and LINEORD,

1966a; RAYMONT, SRINIVASAGAM and RAYMONT, 1969 ; REEVE, RAYMONT and RAYMONT, 1970). Since we did not carry out protein analyses we have no way of evaluating its relative importance in the copepods. However, lower mesopelagic and bathypelagic copepods were so rich in lipid that most of their protein probably had an enzymatic, supportive, or locomotive function.

Vertical distribution

Although the vertical distribution of copepods described in this study were based on evidence from only one bongo net series, they were in agreement with the findings of other workers. GUEREDRAT (1969) noted the depth of capture of Paraeuchaeta hanseni, Metridia princeps and Gaussia princeps using a midwater trawl. He found that G. princeps was always absent from the upper 300 m and often from the upper 650 m in the daytime. Pareuchaeta hanseni and Metridia princeps were never found in the upper 380 m. Our data also show that Gaussia princeps was absent in the upper 250 m during the day, while Pareuchaeta spp. and Metridia princeps were always found below 250 m. The other distributions noted by us are within those ranges described for the same groups by BRODSKII (1950), HARDY and GUNTHER (1936), ROSE (1933) and TANAKA (1963).

Results of the vertical distribution and lipid studies suggest that the mesopelagic zone is inhabited by two groups of copepods, those which migrate into the surface waters and those which do not. Members of the former group generally have low amounts of total lipid, low wax ester percentages, and high triglyceride fractions; the latter group exhibits the opposite attributes. Our calanoids conform more to the three groups of copepods described by BRODSKII (1950) on the basis of seasonal vertical distributions. His first group includes 'surface-dwelling' species which usually inhabit the upper 50 m but could range down to 400 m; they migrate little or not at all. The second group consists of ' bathypelagic' species, which perform large diel migrations and often reach the surface. Their maximum depths range from 400-3000 m and overlap the third, 'abyssal ', or 'deep-dwelling' group of species. Members of the latter group are rarely found at the surface and range from 1000-4000 m. Our


division between 'migrating' and 'deep-dwelling' copepods seems to fall between copepods captured above and below about 600 m rather than at 1000 m. Copepods from bongo nets towed through the depth interval 325-625 m had the greatest variability in lipid content.

CULKIN and Mogms (1969) noted the absence of wax esters in a euphausiid (Euphausia brevis), six species of mesopelagic decapods (Gennadas valens was one of these), and eight species of squid. We found that the decapods Gennadas sp., the mysid Gnathophausia sp., and deep-sea oegopsid squid contained 10, 69 and 27 ~ wax esters respectively. The deepest trawl by Culkin and Morris was to 1000 m, and most of the crustaceans were from shallower trawls. Our trawls were to actual fishing depths of 2500 m, so that we suspect that the organisms in our study may be from deeper waters.

Wax esters as reserve lipids

NEVENZEL (1970) has suggested three possible functions for the wax esters in marine organisms: (1) buoyancy, (2) thermal insulation and (3) reserve energy storage. A fourth function might be to provide support. LITTLEPAGE (1964) presented a convincing argument against the possibility that lipids are of major importance as flotation mechanisms. LEE, NEVENZEL, PAFFENHOFER and BENSON (1970) suggest that phospholipids and cholesterols have a structural function whereas the triglycerides and wax esters serve as energy storages. In our study Gaussia princeps used only triglycerides during 120 hr of starvation. However, the duration of the experiment was too short to demonstrate that wax esters are a reserve lipid. Recently, Lee and Barnes (unpublished data) conducted a preliminary long-term starvation experiment which showed complete utilization of triglycerides and a decrease of wax esters from 67 to 25 ~ of the total lipid in G. princeps that were still active after 5 weeks of starvation. Thus, wax esters in ' migrating ' and ' deep-living' copepods probably serve as energy reserves. However the possibility of an insulation function cannot be ignored.

It may be that the paucity of food for 'deep-living' copepods favored the adoption of a secondary reserve lipid to aid survival during long periods of food deprivation. An unanswered question is why wax esters replace triglycerides as the main lipid component in ' deep-living' copepods or those inhabiting the colder waters of higher latitudes. Three important areas for further study on the replacement of triglycerides by wax esters in copepods are the investigation of: (1) the effects of temperature on lipid composition, (2) the compressibility and molar volumes of wax esters and triglycerides and (3) the control mechanisms for the lipase activities of wax esters and triglycerides. An indication of how feedback inhibition may work in the control of wax ester lipase activity is given by the recent work of MATTSON, VOLPENHEIN and BENJAMIN (1970). They showed that long chain alcohols (a breakdown product of wax esters) inhibit the activity of pancreatic lipase. Preliminary work on the lipid metabolism of G. princeps indicated a preferential catabolism of triglyceride over wax ester. The wax esters were consumed slowly after the triglyceride supply was exhausted. These results suggest the importance of enzymatic control to allow preferential utilization of different lipid substrates.

Large amounts of wax esters have now been found in deep-living members of the fish families Gonostomatidae, Sternoptychidae, Myctophidae and Gempylidae (NEVENZEL, 1970 and Table 9). The results of our gut content studies on three of the four families indicate that the large amounts of wax esters in these fish may be coming


from their foods, which included copepods such as Rh&calanus. There is a similarity of the alcohol and fatty acid composition in wax esters for mesopelagic copepods such as Gaetanus brevicornis and Gaussia princeps (Table 6) and the myctophids examined by NEVENZEL, RODEGKER, ROBINSON and KAYAMA (1969). The occurrence of large amounts of wax esters in the giant squid and sperm whale (HANSE and Cr~EOH, 1969; TATEISHI, FUJIWARA and SAKIRAI, 1958) suggests that these lipids are also important in the higher order carnivores which feed in deep water.

It has been shown for the groups of copepods analyzed that two conditions exist: (1) for copepods in the epipelagic and upper mesopelagic zones, the total lipid and wax esters are higher in those from polar or temperate regions than those in lower latitudes and (2) the copepods from lower mesopelagic or bathypelagic zones of lower latitudes resemble shallower-living forms from the polar regions. One may generally account for the distribution of lipids in marine copepods on the basis of the temporal distribution, relative abundance, and rate of supply of food.

Polar and boreal epipelagic communities are generally thought to exhibit lower turnover rates, higher fluctuations in population abundances (lower stability), and higher biomasses relative to those of tropical and subtropical communities. In high latitudes much of the annual production occurs in short bursts during a few spring and summer months (ANDERSON, 1964; ENGLISH, 1961 ; McALLISTER, 1969 ; MCLAREN, 1969; RAYMONT, 1963). Zooplankton must feed and store energy in preparation for winter months of lower production and food abundance. When the supply of food is inhomogeneously distributed seasonally and is abundant for only certain periods, it would be advantageous for organisms to be able to store large energy reserves to sustain their metabolic needs (LITTLEPAGE, 1964). In contrast to this marked seasonal variation, zooplankton in tropical and sub-tropical regions have a more constant supply of food (RYTHER, 1963). Although the standing stock of food is low, the rate of supply of food is presumed to be relatively constant and high. Under these conditions the opportunity for feeding may be continuous throughout the year, and large energy reserves would not be necessary. Therefore it appears reasonable that near-surface zooplankton living in high latitudes store more energy as lipid relative to those in low latitudes.

The mesopelagic and bathypelagic communities also occur in a stable environment but the standing stock of zooplankton is low (VINOGRADOV, 1961). The downward transport of available food from the epipelagic waters is thought to be due primarily to vertical migration, as indicated by the increase of predators and decrease of filter feeders (V1NOGRADOV, 1962). The higher occurrence of a carnivorous mode of feeding in the deep-sea plankton relative to the epipelagic plankton is probably the result of adaptation to infrequent encounters with other large organisms. If most deep-living organisms do in fact feed infrequently because of very low concentrations of prey, it would be advantageous for the predator to have: (1) an efficient digestive system, (2) a low average metabolic rate and (3) large energy reserves. Hence, in comparison to the epipelagic zooplankton, which generally have a higher concentration of food and probably a higher rate of supply as well, the mesopelagic and bathypelagic groups ought to contain higher amounts of energy stored as lipid than the epipelagic groups. This explanation cannot account for all cases. As shown above, some near-surface copepods captured in subtropical latitudes contain a moderate amount of lipid and wax esters (i.e. Calanus helgolandicus, Rhincalanus nasutus and Euchaeta media). These


exceptions may be attributed to a southern extension of the distribution of these boreal copepods by the California Current and the ability to persist in cool surface waters near the coast due to upwelling.

An alternative interpretation may be presented. The frequent occurrence of wax esters and high percentages of lipid in marine copepods from cold waters suggests that temperature might be the cause of the distribution of lipids. In spite of both ex- planations, the results appear to be influenced by the effects of taxonomic affinity. It was noted above that members of most genera contained either high or very low percentages of wax esters. All species examined of the genera Calanus and Euchaeta tended to contain large or moderate amounts of wax esters regardless of their latitudinal distribution, although the wax esters decreased with decreasing latitude (Table 4). These cases perhaps arise because of evolutionary processes which have enabled closely related species to live in very different habitats and yet retain a degree of similarity in their lipid composition. Further studies are needed to determine the relative effects of trophic ecology, temperature, and taxonomic affinity on the lipid composition of marine copepods.

Acknowledgements--The authors are grateful to A. FLEMINGER, D. C. JUDKINS, and R. WISNER for their assistance in the identification of copepods, decapods, and fish, respectively. The assistance and interest of H. GORDON in sampling and identification of fish is also appreciated. We thank H. KOBAYASHI and J. L. MOHR for providing copepods from the Arctic Sta. T-3 (Supported by ONR- NR 307-270; Contract No. N00014-67-A-0269-0013) and thank C. L. HUBBS and A. A. BENSON for providing shiptime. Our thanks are due to A. A. BENSON, A. FLEMINGER, M. M. MULLIN and J. C. NEVENZEL for reviewing the manuscript and making helpful suggestions. This work was supported by NSF Contract GB-24834, Institute of Marine Resources General Funds, and Marine Life Research General Funds.

R E F E R E N C E S

ACKMAN R. G. and C. A. EATON (1967) Fatty acid composition of the decapod shrimp, Pandalus borealis, in relation to that of the euphausid, Meganyctiphanes norvegica. J. Fish. Res. Bd Can., 24, 467-471.

ANDERSON G. C. (1964) The seasonal and geographic distribution of primary productivity off the Washington and Oregon coast. Limnol. Oceanogr., 9, 284-302.

ARMENTA J. S. (1964) A rapid chemical method for quantification of lipids separated by thin-layer chromatography. J. Lipid Res., 5, 270-272.

BARTLEY W., L. M. BIRT and P. BANKS (1968) The biochemistry of tissues. John Wiley, 375 pp. BEUMER M., M. M. MULLIN and R. R. L. GUILLARD (1970) A polyunsaturated hydrocarbon

(3, 6, 9, 12, 15, 18-heneicosahexaene) in the marine food web. Mar. Biol., 6, 226-235. BLUMER M., M. M. MULLIN and D. W. THOMAS (1964) Pristane in the marine environment.

Helgoliinder wiss. Meeresunters, 10, 187-201. BRODSKII K. A. (1950) Calanoida of the far eastern seas and polar basin of the USSR. (In

Russian). Opredel. Fauni SSSR. Zool. Inst. Akad. Nauk SSSR, 35, 441 pp. Translation: Program for Scientific Translations, 440 pp.

CORNER E. D. S. and C. B. COWEr (1968) Biochemical studies on the production of marine zooplankton. Biol. Rev., 43, 393-426.

CULKIN F. and R. J. MORRIS (1969) The fatty acids of some marine crustaceans. Deep-Sea Res., 16, 109-116.

CULKIN F. and R. J. MORRIS (1970) The fatty acids of some cephalopods. Deep-Sea Res., 17, 171-174.

ENGLISH T. S. (1961) Some biological oceanographic observations in the central North Polar Sea, Drift Station Alpha, 1957-58. Res. Pap. Arctic Inst. N. Am., 13, 80 pp.

FISHER L. R. (1962) The total lipid material in some species of marine zooplankton. Rapp. P.-v. R~un. Cons. perm. int. Explor. Mer, 153, 129-136.

GRICE G. D. 0963) A revision of the genus Candacia (Copepoda:Calanoida) with an annotated list of the species and a key for their identification. ZoSl. Meded., Leiden, 3, 171-194.


GUEREDRAT J. A. (1969) Distribution de quatre esp~ces de cop6podes bathyprlagiques dans l'ouest du Pacifique equatorial et tropical sud. Deep-Sea Res., 16, 361-375.

GUNSTONE F. D. (1967) An introduction to the chemistry and biochemistry of fatty acids and their glycerides. Chapman and Hall, 209 pp.

HANSE I. A. and C. C. CHEOH (1969) Related dietary and tissue lipids of the sperm whale. Comp. Biochem PhysioL, 31, 757-761.

HARDY A. (1958) The open sea: the world of plankton. Collins, 335 pp. HARDY A. C. and E. R. GUNTHER (1936) Plankton of the South Georgia whaling grounds and

adjacent waters, 1926-1927. Discovery Rept., 11, 1--456. HEDGPETH J. W. (1957) Marine biogeography. Mere. geoL Soc. Am., 67, 17-28. Hi3LSEMANN K. (1966) Revision of the genus Lueicutia (Copepoda:Calanoida) with a key to

its species. Bull. mar. Sci., 16, 702-747. JEFFREY L. M., N. R. BOTrlNO and R. REISER (1966) The distribution of fatty acid classes in

lipids of antarctic euphausids. Antarctic J., 1, 209. LEE R. F. and A. R. LOEBLICrI, III (1971) Distribution of 21:6 hydrocarbon and its relation-

ship to 22:6 fatty acid in algae. Phytochem., 10, 593-602. LEE R. F., J. C. NEVENZEL and G. A. PAFFENH()FER (1970) Wax esters in marine copepods.

Science, N.Y. 167, 1510-1511. LEE R. F., J. C. NEVENZEL and G. A. PAFFENHOFER (1971) Importance of wax esters and other,

lipids in the marine food chain: phytoplankton and copepods. Mar. BioL, 9 (2), 99-108. LEE R. F., J. C. NEVENZEL, G. A. PAFFENHrFER and A. A. BENSON (1970) The metabolism of

wax esters and other lipids by the marine copepod, Calanus helgolandicus. J. Lipid Res., 11, 237-240.

LEE R. F., J. C. NEVENZEL, G. A. PAFFENarFFR, A. A. BENSON, S. PATTON and T. KAVANAGH (1970) A unique hexaene hydrocarbon from a diatom. Biochem. Biophys. Acta, 202 386--388.

L1NrORD E. (1965) Biochemical studies on marine zooplankton--II. Variations in the lipid content of some Mysidacea. J. Cons. perm. int. Explor. Mer, 30, 16--27.

LITTLEPAGE J. L. (1964) Seasonal variation in lipid content of two Antarctic marine Crustacea. Actual. scient, ind., 1312, 463-470.

MATTSON F. H., R. A. VOLPENHEIN and L. BENJAMIN (1970) Inhibition of lipolysis by normal alcohols. J. biol. Chem., 245, 5335-5340.

MCALLISTER C. D. (1969) Aspects of estimating zooplankton production from phytoplankton production. J. Fish. Res. Bd Can., 26, 199-220.

McGOWAN J. A. and D. M. BROWN (1966) A new open-closing paired zooplankton net. Scripps Inst. Oceanogr. Ref 66-23, 56 pp. (Unpublished manuscript).

MCLAREN I. A. (•969) Population and production ecology of zooplankton in Ogac Lake, a landlocked fiord on Baffin Island. J. Fish. Res. Bd Can., 26, 1485-1559.

MOR1 T. (1964) The pelagic Copepoda from the neighbouring waters of Japan. Soyo, 150 pp. NEMENYJ P. (1963) Distribution-free multiple comparisons. Ph.D. Dissertation, Princeton

Univ. NEVErqZEL J. C. (1970) Occurrence, function, and biosynthesis of wax esters in marine

organisms. Lipids, 5, 308-319. NEVENZEL J. C., W. RODEGKER and J. F. MEAD (1965) The lipids of Ruvettus pretiosus

muscle and liver. Biochem., 4, 1589-1594. NEVENZEL J. C., W. RODEGKER, J. S. ROBINSON and M. KAYAMA (1969) The lipids of some

lantern fishes (family Myctophidae). Comp. Biochem. PhysioL, 31, 25-36. RAYMONT J. E. G. (1963) Plankton and productivity in the oceans. Pergamon Press, 660 pp. RAYMONT, J. E. G., J. AUSTIN and E. LINFORD (1964) Biochemical studies on marine zooplank-

ton--I. The biochemical composition of Neomysis integer. J. Cons. perm. int. Explor. Mer, 26, 354-363.

RAYMONT J. E. G., J. AUSTIN and E. LINFORD (1966a) Biochemical studies on marine zooplankton. IlL Seasonal variation in the biochemical composition of Neomysis integer. In: Some contempory studies in marine science, H. BARNES, editor, Allen and Unwin, 597-605.

RAYMONT J. E. G., J. AUSTIN and E. LINFORD (1966b) Biochemical composition of certain oceanic decapods. Deep-Sea l~es., 14, 113-115.

RAYMONT J. E. G., and R. J. CONOVER (1961) Further investigations on the carbohydrate content of marine zooplankton. Limnol. Oceanogr., 6, 154-164.

RAYMONT J. E. G., R. T. SRINIVASAGAM and J. K. B. RAYMONT (1969) Biochemical studies on marine zooplankton--VI. Investigations on Meganyctiphanes norvegica (M. Sars). Deep-Sea Res., 16, 141-156.


REEVE M. R., J. E. G. RAYMONT and J. K. B. RAYMONT (1970) Seasonal biochemical composition and energy sources of Sagitta hispida. Mar. Biol., 6, 357-364.

Rose M. (1933) Cop6podes p61agiques. Faune de France, P. Lechevalier, 26, 374 pp. RYTHER J. H. (1963) Geographic variations in productivity. In: The sea, M. N. HILL, editor,

Interscience, 347-380. SEWELL R. B. S. (1947) The free-swimming planktonic Copepoda. Sci. Rept., John Murray

Exped. 1933-34. 8, 1-303. S1Pos J. C. and R. G. ACKMAN (1968) Jellyfish (Cyanea capillata) lipids; fatty acid compo-

sition. J. Fish. Res. Bd Can., 25, 1561-1569. TANAKA O. (1963) The pelagic copepods of the Izu region, middle Japan. Systematic account

--IX. Families Centropagidae, Pseudodiaptomidae, Temoridae, Metridiidae, and Lucicutiidae. Pubis. Seto. mar. biol. Lab., 11, 7-35.

TATEISHI T., M. FUJIWARA and H. SAKURAI (1958) Separation of sperm blubber oil into wax and glyceride by elution chromatography. Kogyo Kagaku Zasshi, 61, 1580-1582.

VINOGRADOV M. E. (1961) Quantitative distribution of deep-sea plankton in the western Pacific and its relation to deep-water circulation. Deep-Sea Res., 8, 215-258.

VINOGRADOV M. E. (1962) The feeding of deep-sea zooplankton. Rapp. P.-v. Rdun. Cons. perm. int. Explor. Met, 153, 114-120.

VINOGRADOVA Z. A. (1960) Study of the biochemical composition of Antarctic krill (Euphausia superba Dana). (In Russian) Dokl. Akad. Nauk SSSR, 133, 680-682.

YAMADA M. (1964) The lipid in plankton. Bull. Jap. Soc. Scient. Fish., 30, 673-681.

Documents

Distribution and importance of wax esters in marine copepods and other zooplankton