Control of Metamorphosis in Flatfish - UGent · after metamorphosis has started - T4 more impt initially? 3. Window of opportunity 18-20 mm size (pre-pro metamorphosis) 4. Photoperiod

K. Pittman*, J. Solbakken1 & K. Hamre2

*Dept of Fisheries and Marine Biology,University of Bergen, Norway1. Austevoll Mariculture Station, Inst of Marine Research, Bergen

2. Division of Nutrition, Directorate of Fisheries, Bergen. Austevoll

Control of Metamorphosis in Flatfish

Directorate of FisheriesInst of Marine Research

Austevoll Mariculture Station

University of Bergen

Farmed Flatfish juveniles exhibit:

Pigment abnormalitiesLack of eye migrationSkeletal abnormalitiesWeaning mortality

Fundamental common factor?

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DAYS

STAGE

Control of metamorphosis

= control of juvenile quality

Experiments

1. Natural zooplankton vs standard enriched Artemia1 egg batch 4 groups

2. Exogenous T4 continuously and at Pre-, Pro, Climax & PC Metam

3. Photoperiod 24 hrs light or 12L:12Dat 22 days and at 12, 21, 30 and 42 DPF

Feeding with Artemia or Zooplankton

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SIZ

E (

mm

SL Artemia-fedMH Artemia-fedSL Zooplankton-fedMH Zooplankton-fed

Malpigmentation: Artemia 93% Zooplankton 32%Lack of Eye migration: 90 12Dorsal fin “comb”: 82 33

ZooplanktonArtemia

Days post firstfeeding

Dry

wei

ght (

mg)

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From: Hamre, Opstad, Espe, Solbakken, Hemre & Pittman, submitted


LFZ

LFA


From Solbakken et al. submitted

FATTY ACIDS IN PREY

Artemia Zooplankton

ARA (20:4 n-6) 2.1±0.1a 0.7±0.2b

EPA (20:5 n-3) 4.9±0.3a 18.6±3.2b

DHA (22:6 n-3) 6.3±0.9a 28.5±4.8b

Σ Saturated 21.3±1.2 22.5±1.0

Σ Monoenes 27.3±0.2a 10.4±4.0b

Σ n-3 34.5±0.4a 55.9±4.8b

Σ n-6 8.1±0.4 4.3±3.3

DHA/EPA 1.3±0.1 1.6±0.4

EPA/ARA 2.3±0.0a 29±10 b


(In prey)Wild zooplankton Artemia

Iodine (ug g dw-1) 350 +/- 19 (n=5) 0.5+/-0 (n=4)***

Selenium (ug g dw-1) 2 +/- 0.2 (5) 2.2 +/-0.1 (4)

Phenylalanine (mg g protein-1) 32+/- 2 (5) 39 +/- 1 (4)

Tyrosine (mg g protein-1) 37 +/- 3 (5) 37 +/- 1 (4)

from: Solbakken, Berntssen, Norberg, Pittman & Hamre (submitted)

Feeding with Artemia or Zooplankton(In larvae)

From Solbakken et al. and Hamre et al. (2001) submitted


From Solbakken et al. and Hamre et al. (2001) submitted

A**

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***

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Iod

ine

(ug

g d

w-1

)

LFC

LFA


From: Solbakken, Berntssen, Norberg, Pittman & Hamre submitted


Window of metamorphosis

critical size about 18 mm for halibut?

17.99 mm SL

Foto: Ø. Sæle

Exogenous Thyroxine - continuous

Co

rtis

ol (

ng

/larv

a)

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ControlExogenous T4

Standard length (mm)

Eye

mig

rati

on

ind

ex

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Exogenous T4 and FDFControl and FDFExogenous T4Control

T4

(ng

/larv

a)

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ControlExogenous T4

Standard length (mm)

T3

(ng

/larv

a)

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ControlExogenous T4

Solbakken et al. (subm.)

Exogenous Thyroxine - stages

Age

(DPF)

SL (mm) Stage MH (mm)

15 15.3 ±

0.6

Pre-M –

Pro-M

1.7 ± 0.4

37 18.2 ±

1.9

Pro-M -

MC

4.4 ± 1.1

62 29.3 ±

4.2

Late MC

- JUV

7.2 ± 1.1

Exogenous Thyroxine - stages

DPF SL (mm)

Exogenous

T4

Controls

15 15.3 ± 0.1 (40)

22 16.3 ± 0.1 (60) 15.6 ± 0.1 (55) ***

29 17.3 ± 0.2 (49) 16.4 ± 0.2 (40) ***

37 18.2 ± 0.3 (30)

44 22.2 ± 0.2 (56) 22.7 ± 0.2 (47)

51 24.8 ± 0.4 (56) 25.1 ± 0.4 (48)

62 29.3 ± 0.8 (28)

69 32.4 ± 0.5 (56) 32.7 ± 0.6 (48)

76 38.0 ± 0.9 (56) 36.6 ± 1.2 (28)

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EM

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yoto

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Size (mm)

Fre

e F

in (

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mo

glo

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Photoperiod

Continuous 22DPF

Photoperiod - continuous

Normal Ambi Pseudo

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larv

ae

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Photoperiod - ages

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Sta

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LD12

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Solbakken et al. (in prep.)

Photoperiod - ages

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EMI/S

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LLLD 12LD 21LD 30LD 41

Solbakken et al. (in prep.)

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Standard length

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Photoperiod

size vs age

ages

Age vs Size: example from diet expt

18217,39

Dag 564-13,91

143-15,62

65-14,76

74-13,74

183-13,69

135-16,26

144-14,01

Dag 14 Dag 21

173-19,16

Dag 25

221-18,8

203-16,8

202-14,9

S

M

L

Ø. Sæle

Hypothalamus-pituitary-thyroid axis

TSH

T3 Bound T4

TRH

T3 T4

T3 T4Deiodination

photoperiod

melatonin

thyroid Diet (+iodine?)

Diet (+selenium)

Thyroid follicle

Plasma

TissueReceptors

Up or down regulation DNA

Development Growth ReproductionFig: Ø. Sæle

iodinephenylalanine 4-monooxygenase

tyrosine 3-monooxygenase

Monophenol monooxygenase

Monophenolmonooxygenase

Deiodinases withselenocystein

(types 1& 3 ID)(type 2 ID)

Deiodinases(type 1 & 3 ID)

phenylalanine (essential a.a.)

tyrosine thyroxin (T4)

melanin

dopa

dopaquinone

triiodothyronine (T3)

Proposed pathway to pigmentation and settlementdiet

diet (& seawater)

diet

neural + skeletal changepigmentation

Aseasonal Reproduction

Artemia

24

0Jan June Dec

Conclusions1. Dietary micronutrients important for endocrine control

of metamorphosis (iodine & selenium)

2. Peak deiodinase activity in 24-26 mm size, after metamorphosis has started - T4 more impt initially?

3. Window of opportunity 18-20 mm size (pre-pro metamorphosis)

4. Photoperiod induces heterochrony of eye migration,hemoglobin and pigmentation effects

5. Exogenous thyroid has positive effect on skeletal growth at pre-pro metamorphosis, among other effects

Conclusions

6. Order of metamorphic events is i) neural ii) growth and skeletal change iii) circulation changes iv) pigmentation finally established

7. Heterochrony is more related to age than size

8. Stage dependent response to photoperiod-melatonin-thyroidstimulation?

Future: effects on immunology (IgM), TRs, TRIPs

Documents

Control of Metamorphosis in Flatfish - UGent · after metamorphosis has started - T4 more impt initially? 3. Window of opportunity 18-20 mm size (pre-pro metamorphosis) 4. Photoperiod