ORIGINAL PAPER

New family of sea anemones (Actiniaria, Acontiaria)from deep polar seas

Estefanıa Rodrıguez Æ Pablo J. Lopez-Gonzalez ÆMarymegan Daly

Received: 2 October 2008 / Revised: 13 December 2008 / Accepted: 15 December 2008 / Published online: 14 January 2009

� Springer-Verlag 2009

Abstract We describe and illustrate two new species from

polar deep seas that belong to a new genus and family.

Antipodactidae fam. nov. is characterized by acontia with

macrobasic p-amastigophores; this type of nematocyst has

never been reported from acontia. Antipodactis gen. nov. is

characterized by a column with a distinct scapus and

scapulus, cuticle-bearing tenaculi on the scapus, more mes-

enteries proximally than distally, mesenteries regularly

arranged, restricted and reniform retractor musculature, and

macrobasic p-amastigophores in the acontia. Antipodactis

scotiae sp. nov. and A. awii sp. nov. differ in number of

mesenteries, retractor and parietobasilar muscles, cnidae,

and geographic distribution. We discuss the familial and

generic characters of Antipodactis gen. nov. and its rela-

tionship to other families of acontiarian sea anemones: it

most closely resembles members of Kadosactidae in terms of

anatomy and some aspects of cnidom, and has a cnidom

identical to that of Diadumenidae in terms of the types of

nematocysts. Because the morphology of nematocysts is

critical to the diagnosis of this family, we review and com-

ment on the nomenclature of mastigophores. The macrobasic

p-amastigophores of Antipodactidae fam. nov. conform to

England’s (Hydrobiologia 216/217:691–697, 1991) defini-

tion rather than that of Mariscal (Coelenterate Biology.

Academic Press, New York, pp 129–178, 1974).

Keywords Antipodactidae � Antipodactis � Acontiaria �Deep sea � Antarctica � Arctic � Bipolar

Introduction

Bipolar distributions—‘‘an interrupted distribution of

identical or closely related taxa in polar, temperate or

subtropical zones of both hemispheres, characterized by

their absence in the tropics’’ (Bergh 1947; Stepanjants et al.

1996, 1997)—have been known for more than 150 years.

There are several explanations for the phenomenon, most

prominently independent or convergent origins of appar-

ently bipolar taxa, migration through deep- and on cold-

water currents, or relictual distributions shaped by glacial

periods (see review by Stepanjants et al. 2006). This pat-

tern has been observed in many marine invertebrate taxa

(Malyutina and Brandt 2007).

Although bipolarity is well studied in medusozoan cni-

darians (Stepanjants et al. 2006), it is not well documented

for members of their sister group, Anthozoa. The antho-

zoan order Actiniaria includes seven families (*15% of

total family level diversity) that have members with a

bipolar distribution: Actinostolidae Carlgren, 1893; Hal-

campidae Andres, 1883; Kadosactidae Stephenson, 1920;

Limnactiniidae Carlgren, 1921; Liponematidae Hertwig,

1882, Octineonidae Fowler, 1894; Bathyphellidae Carl-

gren, 1932; (see Fautin 2008). At the genus level, the

number of taxa with a bipolar distribution increases (e.g.,

Actinernus Verrill, 1879; Bolocera Gosse, 1860; Capnea

Forbes, 1841; Kadosactis Danielssen, 1891; Protanthea

Carlgren, 1891; etc.; see Dunn 1982; Cairns et al. 2007),

although this represents a smaller fraction of taxonomic

diversity at this rank. In addition to these strictly bipolar

taxa, other actiniarian genera and families are found at high

E. Rodrıguez (&) � M. Daly

Department Evolution, Ecology and Organismal Biology,

Ohio State University, 1315 Kinnear Rd.,

Columbus, OH 43212, USA

e-mail: fani@us.es; rodriguez.292@osu.edu

E. Rodrıguez � P. J. Lopez-Gonzalez

Departamento de Fisiologıa y Zoologıa, Facultad de Biologıa,

Universidad de Sevilla, Reina Mercedes 6, 41012 Sevilla, Spain

123

Polar Biol (2009) 32:703–717

DOI 10.1007/s00300-008-0575-0

latitudes and in deep tropical seas; according to Stepanjants

et al. (2006), these taxa should also be considered bipolar,

or ‘‘bipolar taxa with an equatorial submergence’’ (type 2

bipolar distribution). This biogeographic category recog-

nizes the ecological similarity of these cold, dark,

thermally stable, oligotrophic habitats.

Although it represents the largest inhabitable environ-

ment in this world, the deep sea and its fauna are very poorly

known (Brandt et al. 2004). Some deep-sea areas in Ant-

arctica, such the Scotia and the Weddell seas, are among the

least studied parts of the world (Clarke and Johnston 2003).

Despite recent international efforts to survey the deep sea

benthos of the polar seas (e.g., Andeep, CedaMar, etc.), and

notable progress in many groups (e.g., Brandt et al. 2007a, b),

basic diversity remains poorly known for many taxa,

including actiniarians. The absence of information about the

inhabitants of the deep polar seas complicates the discern-

ment of broader patterns of distribution.

We describe two new species of sea anemones from

polar seas, Antipodactis scotiae sp. nov. and A. awii sp.

nov. from 13 specimens in the Scotia Sea (Antarctica) and

21 specimens from the Norwegian Sea (Arctic), respec-

tively. Antipodactidae fam. nov. is the eighth bipolar

family of sea anemones. These new species belong to a

new genus and family characterized by macrobasic

p-amastigophores sensu England (1991) in the acontia.

Materials and methods

The material studied was collected on the Polarstern

cruises ANT XIX/3 (ANDEEP-I) and ARK XX/1

sponsored by the Alfred-Wegener-Institut fur Polar-und

Meeresforschung, Bremerhaven, during the austral sum-

mer of 2002 to the Scotia Sea and the summer of 2004 to

the Arctic Ocean, respectively (Figs. 1, 2). Additional

material deposited at the Smithsonian was collected by

the USARP ELTANIN 9 cruise in 1974 to the Scotia Sea

(Antarctica).

Sea anemones collected in 2002 in Antarctica were

relaxed on board using menthol crystals and subsequently

fixed in 10% sea–water formalin; Arctic specimens were

not relaxed prior to fixation in 10% sea–water formalin.

Preserved specimens were examined whole, in dissection,

and as serial sections. Fragments of several specimens were

dehydrated in butanol (Johansen 1940), and embedded in

paraffin, or dehydrated in graded ethanol series and then

embedded in paraffin. Histological sections 7–10 lm thick

were stained with Ramon y Cajal’s Triple Stain (Gabe

1968) or Masson’s trichrome (Presnell and Schreibman

1997).

Measurements of cnidae were made from preserved

material; small pieces of tissue were smeared on slides and

examined using DIC microscopy at 1,0009 magnification.

We scanned through the slides and haphazardly measured

20 capsules of each type (when possible) to generate a

range: frequencies given are subjective impressions based

on all the cnidae seen on the slides. For each type, a mean

and standard deviation has been provided to give an idea of

the distribution of sizes; these are not statistically signifi-

cant (see Williams 1998, 2000 for minimal requirements

for statistical significance in cnida sizes) but provide some

qualitative information about variability in capsule size for

each type of nematocyst.

Fig. 1 Geographic distribution of A. scotiae sp. nov. A star marks the type locality, a circle additional localities

704 Polar Biol (2009) 32:703–717

123

Cnida terminology generally follows Mariscal (1974);

however, we considered macrobasic p-amastigophores

sensu England (1991) (see discussion). We followed

Carlgren (1940) and Mariscal (1974) in distinguishing

between microbasic p-mastigophores and p-amastigo-

phores for the cnidae of the acontia because this distinction

has been traditionally used to differentiate taxa in this the

group (Carlgren 1949). The term p-amastigophore refers to

all capsules that are either apparently devoid of a terminal

tubule or have a vestigial one. Confusion and inconsistency

in reports of these types of nematocysts are common (e.g.,

Fautin et al. 1988; England 1990). Although undischarged

‘‘amastigophores’’ appear not to have a terminal tubule, a

tubule is visible under SEM for at least some amastigo-

phores (Ostman 2000). The kind of spines on the proximal

tubule and the way these are packed appears to be a more

consistent difference between these types of nematocysts

(Ostman 2000, A. Reft, personal communication); how-

ever, these features are not accessible for the undischarged

capsules of formalin-fixed material. In our discussion, we

rely on bibliographic records to distinguish these

nematocysts in the acontia when comparing families, but

note that the reliability of these records is not clear. The

types of cnidae in the acontia need to be critically re-

evaluated to properly assign the various nematocysts to

morphologically meaningful categories and assess the

taxonomic and phylogenetic value of this feature.

The studied material has been deposited in the American

Museum of Natural History in New York (AMNH), the

collection of the research group ‘‘Biodiversidad y Ecologıa

de Invertebrados Marinos’’ at the University of Seville in

Spain (BEIM), the National Museum of Natural History,

the Smithsonian Institution in Washington (USMN), and

the Zoologisches Institut und Zoologisches Museum in

Hamburg (ZMH).

Results

Order Actiniaria Hertwig, 1882

Suborder Nynantheae Carlgren, 1899

Family Antipodactidae fam. nov.

Diagnosis

Nynantheae with basilar musculature. Mesogleal marginal

sphincter muscle. One tentacle communicating with each

endo- and exo-coel. Mesenteries regularly arranged, not

differentiated into macro- and micro-cnemes. Acontia with

macrobasic p-amastigophores and basitrichs. Cnidom:

spirocysts, basitrichs, holotrichs, microbasic p-mastigo-

phores, and macrobasic p-amastigophores.

Genus Antipodactis gen. nov.

Diagnosis

Antipodactidae with elongated body and slightly rounded

aboral end. Column divisible into scapus and scapulus;

scapus bears tenaculi with cuticle. Scapulus with cinclides

irregularly arrayed. Tentacles not numerous: about as many

tentacles as mesenteries at the margin. Longitudinal mus-

cles of tentacles and radial muscles of oral disc ectodermal.

Strong mesogleal marginal sphincter muscle. Mesenteries

regularly arranged, not differentiated into macro- and

micro-cnemes, first three cycles fertile. More mesenteries

proximally than distally. At least 12 pairs of perfect mes-

enteries at mid-column; two pairs of fertile directives each

attached to a siphonoglyph. Retractor muscles of older

mesenteries strong, restricted. Parietobasilar muscles well

developed. Acontia with macrobasic p-amastigophores and

basitrichs. Cnidom: Spirocysts, basitrichs, holotrichs, micro-

basic p-mastigophores, and macrobasic p-amastigophores.

Fig 2 Geographic distribution of A. awii sp. nov. A star marks the

type locality

Polar Biol (2009) 32:703–717 705

123

Type species

Antipodactis scotiae sp. nov., by original designation.

Etymology

From the Greek word ‘‘antipodes’’ (anti-: ‘‘opposed’’ and

pous: ‘‘foot’’), referring to places that are on opposite sides

of the globe. It is combined with the Greek ‘‘–actis,’’

meaning ray, a common suffix in sea anemone generic

names. Gender feminine.

Antipodactis scotiae sp. nov. (Figs. 1, 3, 4, 5; Table 1).

Type material

Holotype: ZMH (C 11718), Polarstern ANT XIX/3, stn.

PS61/114-10, Scotia Sea (Antarctica), 61�43.700S60�42.620W, 2,852.9–2,856.2 m depth, 19 February 2002,

Agassiz trawl. Paratypes: AMNH, three specimens; ZMH

(C 11719), four specimens; same data as the holotype for

all lots of material.

Additional material

BEIM (CRA-0010), four specimens, Polarstern ANT XIX/

3, stn. PS61/114-10, Scotia Sea (Antarctica), 61�43.700S60�42.620W, 2,852.9–2,856.2 m depth, 19 February 2002,

Agassiz trawl; USMN (1121703), one specimen, USARP-

Eltanin cruise 9, st. 722, Scotia Sea (Antarctica), 56�040S–

56�000S 33�590W–33�570W, 3,138–3,239 m depth,

8 September 1963, 50 Blake trawl.

Description

External anatomy

Body elongate (Fig. 3a, b), column of preserved specimens

to 13 mm diameter and 36 mm height. Proximal end

poorly differentiated, more or less rounded, without a

strong limbus (Fig. 3a, b). Cuticle of scapus lost in most

specimens (Fig. 3b); tenaculi cuticulate, small, with

adherent sand grains; cuticle thick, stratified. Scapulus

smooth (Fig. 3b), with numerous cinclides easily appre-

ciable in fully extended specimens (Fig. 4e); several

cinclides per stronger endocoel, up to 50 per specimen.

Oral disc of slightly contracted preserved specimens

smaller in diameter than proximal end. Tentacles about 48,

longer than diameter of oral disc (to 5 mm) in slightly

contracted preserved specimens.

Internal anatomy

Mesenteries hexamerously arranged in four cycles. First and

second cycle perfect; third with both perfect and imperfect

members, fourth cycle imperfect (Fig. 4b). First, second, and

third cycles present throughout column, fertile; fourth cycle

only present proximally, sterile. Retractor muscles of first

and second cycles of mesenteries strongly restricted, reni-

form (Fig. 4b). Mesenteries of third cycle differentially

developed: some pairs with slightly restricted retractor

muscles and some with poorly developed retractor muscles.

Mesenteries of fourth cycle very poorly developed (Fig. 4d).

Gonochoric; specimens collected in February and Septem-

ber with gametogenic tissue well developed (oocytes 30–

110 lm and spermatic vesicles 80–330 lm in diameter,

respectively). Parietobasilar muscles strong, differentiated

on all mesenteries (Figs. 4b, c); muscle fibers on broad,

branched mesogleal base. Basilar muscles poorly developed,

differentiated but not strong (Fig. 4f). Acontia present.

Mesogleal marginal sphincter muscle moderately strong

and long (Fig. 4a); distal part reticulate and broad, proximal

part alveolate. Muscles fibers in mesoglea closer to gastro-

dermis than to epidermis. Longitudinal muscles of tentacles

and radial muscles of oral disc ectodermal (Fig. 4g). Column

wall of similar thickness entire length: epidermis 0.20–

0.40 mm; mesoglea 0.11–0.13 mm thick, and gastrodermis

0.24–0.30 mm thick at level of actinopharynx.

Cnidom

Robust and gracile spirocysts, basitrichs, holotrichs, micro-

basic p-mastigophores, and macrobasic p-amastigophores

(Fig. 5). See Table 1 for size and distribution.

Color

Column of living specimens pinkish; tentacles salmon or

orange at base, fading to white distally; scapus dark

brownish color due to cuticle. Preserved material uniform

pink to peach.

Fig. 3 External anatomy of A. scotiae sp. nov. a Lateral view of

living specimens; note smooth scapulus (arrow); b Lateral view of

partially contracted living specimen. Scale bars a, b 20 mm

706 Polar Biol (2009) 32:703–717

123

Etymology

The specific epithet refers to the place where specimens

have been collected.

Geographic and bathymetric distribution

Antipodactis scotiae sp. nov. has been collected from

abyssal waters (2,852–3,239 m) in the Scotia Sea, off the

South Shetland and South Sandwich Islands (see Fig. 1).

Antipodactis awii sp. nov. (Figs. 2, 6, 7, 8; Table 1).

Type material

Holotype: ZMH (C 11720), Polarstern ARK XX/1, stn.

PS66/118-1, Arctic Ocean, Hausgarten IV, 79�09.750N03�52.20E, 2,377.2 m depth, 9 July 2004, Agassiz trawl.

Paratypes: AMNH, five specimens; USNM (1121702), five

specimens; ZMH (C 11721), five specimens; same data as

the holotype for all lots of material.

Fig. 4 Internal anatomy of

A. scotiae sp. nov. a Marginal

sphincter muscle; b Cross

section of the column through

the mesenteries at the level of

the actinopharynx showing the

cycles of mesenteries; c Detail

of the directive mesenteries;

d Cross section of the proximal

column showing the fourth

cycle of mesenteries; e Detail of

the marginal column showing a

cinclide; f Basilar muscles;

g Cross section of a tentacle

showing the ectodermal

longitudinal muscles (arrow).

Numbers between pairs indicate

the cycle of mesenteries.

ep epidermis, ga gastrodermis, ssiphonoglyph. Scale barsa 1 mm; b 5 mm; c 1 mm;

d, e 0.5 mm; f 0.1 mm;

g 0.05 mm

Polar Biol (2009) 32:703–717 707

123

Additional material

BEIM (CRA-0011), five specimens, Polarstern ARK XX/1,

stn. PS66/118-1, Arctic Ocean, Hausgarten IV, 79�09.750N03�52.20E, 2,377.2 m depth, 9 July 2004, Agassiz trawl.

Description

External anatomy

Body elongate (Fig. 6), column of preserved specimens to

10 mm diameter and to 25 mm height. Proximal end

broader than distal end, well differentiated with distinct

limbus (Fig. 6a, b, d). Scapus with strong, cuticulate ten-

aculi to which sand grains and small stones adhere; cuticle

thick, stratified. Scapulus smooth (Fig. 6a, b), with cinc-

lides appreciable in some fully extended specimens

(Fig. 7e); several cinclides per endo- and exo-coel, up to 20

per specimen.

Oral disc of slightly contracted preserved specimens

smaller in diameter than proximal end. Tentacles to about

70, longer than diameter of oral disc (to 4 mm) in slightly

contracted preserved specimens.

Internal anatomy

Mesenteries hexamerously arranged in six cycles

(Fig. 7b). First and second cycles perfect; third with both

perfect and imperfect members, fourth, fifth, and sixth

cycles imperfect, latter two incomplete and only present

proximally (only few pairs of sixth cycle present). First,

second, and third cycles present throughout column, fer-

tile; fourth, fifth, and sixth cycles sterile. Retractor

muscles of first and second cycles of mesenteries strongly

restricted, reniform (Fig. 7b, d). Mesenteries of third

cycle differentially developed: some pairs with slightly

restricted retractor muscles and some with poorly devel-

oped retractor muscles. Mesenteries of fourth and fifth

cycles very poorly developed (Fig. 7b, c). Gonochoric;

specimens collected in July with gametogenic tissue well

developed (oocytes 75–200 lm in diameter). Parietobas-

ilar muscles strong, differentiated on all mesenteries

(Fig. 7b, c); muscle fibers on broad, almost triangular

mesogleal base branched only at the side closer to coe-

lenteron. Basilar muscles differentiated, but not strongly

developed (Fig. 7g). Acontia present.

Mesogleal marginal sphincter muscle moderately strong

and long (Fig. 7a); distal part reticulate and broad, proxi-

mal part alveolate. Muscles fibers in mesoglea closer to

gastrodermis than to epidermis. Longitudinal muscles of

tentacles and radial muscles of oral disc ectodermal

(Fig. 7f). Column wall of similar thickness entire length:

epidermis 0.15–0.40 mm; mesoglea 0.20–0.56 mm thick,

and gastrodermis 0.21–0.33 mm thick at level of

actinopharynx.

Cnidom

Robust and gracile spirocysts, basitrichs, holotrichs, micro-

basic p-mastigophores, and macrobasic p-amastigophores

(Fig. 8). See Table 1 for size and distribution.

Color

Scapus of preserved specimens dark brown due to cuticle,

scapulus and tentacles pale pink to white.

Fig. 5 Cnidae of A. scotiae sp. nov. a Basitrich 1; b Basitrich 2;

c Microbasic p-mastigophore; d Basitrich 1; e Basitrich 2;

f Microbasic p-mastigophore; g Holotrich; h Basitrich 1; i Basitrich

2; j Microbasic p-mastigophore; k Holotrich; l Robust spirocyst;

m Basitrich 1; n Basitrich 2; o Microbasic p-mastigophore;

p Basitrich 1; q Basitrich 2; r Microbasic p-mastigophore;

s Basitrich; t Microbasic p-mastigophore 1; u Microbasic p-mastig-

ophore 2; v Basitrich 1; w Basitrich 2; x Macrobasic p-amastigophore

708 Polar Biol (2009) 32:703–717

123

Table 1 Size ranges of the cnidae of A. scotiae sp. nov. and A. awii sp. nov.

Categories Range of length and

width of capsules

(lm) A. scotiae

�X ± SD S N F Range of length and

width of capsules (lm)

A. awii

�X ± SD S N F

Base

Basitrichs 1 (10.1–16.0) 9 (1.8–4.0) 12.7 ± 1.2 9 2.6 ± 0.4 3/3 46 ?? (11.3–15.3) 9 (2.1–3.3) 13.4 ± 1.1 9 2.8 ± 0.3 4/4 50 ??/???

Basitrichs 2 (17.4–29.0) 9 (3.1–5.0) 22.6 ± 2.8 9 3.9 ± 0.4 2/3 43 ?/?? (20.3–29.9) 9 (3.1–5.0) 25.4 ± 2.0 9 4.0 ± 0.4 4/4 50 ??

M p-mastigophores (14.1–22.9) 9 (4.2–5.7) 19.0 ± 2.6 9 4.9 ± 0.4* 2/3 22 ?/?? (20.1–35.3) 9 (4.0–6.0) 27.5 ± 4.0 9 5.2 ± 0.5 4/4 45 ?/??

Holotrichs – 0/3 (16.4–23.2) 9 (6.8–7.2) Contamination?? 1/4 2 —

Scapus

Basitrichs 1 (9.2–15.2) 9 (1.6–2.9) 12.6 ± 1.2 9 2.5 ± 0.3 4/4 45 ??? (10.5–16.1) 9 (1.8–3.3) 13.3 ± 1.3 9 2.6 ± 0.4 4/4 50 ??

Basitrichs 2 (20.0–26.9) 9 (2.9–4.2) 23.3 ± 1.7 9 3.7 ± 0.3 4/4 45 ?/?? (19.1–27.9) 9 (2.5–4.7) 23.7 ± 2.2 9 3.9 ± 0.4 4/4 50 ??/???

M p-mastigophores (17.8–25.6) 9 (3.8–6.4) 21.1 ± 1.6 9 4.8 ± 0.6 4/4 41 ?/?? (23.8–37.4) 9 (4.4–5.5) 29.3 ± 6.0 9 5.0 ± 0.4* 3/4 9 ;

Holotrichs (16.4–24.0) 9 (4.4–6.1) 19.5 ± 2.1 9 5.2 ± 0.5* 2/4 10 ; (19.0–25.6) 9 (5.9–7.9) 22.3 ± 1.9 9 7.2 ± 0.6* 2/4 17 ;

Scapulus

Basitrichs 1 (9.9–15.6) 9 (2.1–3.0) 12.5 ± 1.4 9 2.7 ± 0.3* 4/4 30 ?/?? (11.4–15.6) 9 (2.1–3.3) 13.4 ± 1.3 9 2.8 ± 0.4* 4/4 21 ?/??

Basitrichs 2 (18.2–27.6) 9 (3.1–4.6) 21.3 ± 2.5 9 3.9 ± 0.3 4/4 44 ?? (18.6–25.6) 9 (3.1–4.4) 22.8 ± 1.7 9 3.6 ± 0.3* 3/4 23 ;

M p-mastigophores (24.5–35.1) 9 (4.1–7.2) 28.4 ± 2.6 9 5.6 ± 0.7 4/4 46 ?? (24.4–33.9) 9 (4.6–6.6) 30.5 ± 1.8 9 5.5 ± 0.5 4/4 45 ?/??

Holotrichs (15.4–19.8) 9 (6.1–7.6) 17.4 ± 1.8 9 6.7 ± 0.6* 2/4 5 — (18.2–29.6) 9 (6.2–9.3) 23.8 ± 4.7 x 7.5 ± 1.0* 3/4 7 ;

Tentacles

Spirocysts (20.5–47.3) 9 (3.5–8.2) 29.6 ± 6.4 9 5.5 ± 1.3 4/4 50 ??/??? (23.0–43.5) 9 (3.5–9.6) 35.2 ± 5.0 9 5.9 ± 1.7 4/4 51 ???

Basitrichs 1 (10.0–21.3) 9 (2.0–3.2) 15.0 ± 3.0 9 2.7 ± 0.3* 4/4 27 ?/?? – 0/4

Basitrichs 2 (22.4–36.3) 9 (2.6–4.4) 29.9 ± 3.6 9 3.6 ± 0.4 4/4 48 ?/?? (22.3–31.3) 9 (3.0–4.7) 27.0 ± 2.6 9 3.7 ± 0.5* 3/4 23 ?/??

M p-mastigophores (23.0–49.9) 9 (4.6–7.5) 38.9 ± 8.3 9 5.7 ± 0.6 4/4 50 ??/??? (36.1–50.0) 9 (5.1–7.6) 42.1 ± 2.4 9 6.1 ± 0.6 4/4 51 ??/???

Actinopharynx

Basitrichs 1 (12.0–22.0) 9 (1.7–3.0) 15.2 ± 2.1 9 2.9 ± 0.3 4/4 50 ??/??? (12.8–23.2) 9 (2.0–4.1) 15.6 ± 1.9 9 2.9 ± 0.4 3/3 44 ?/??

Basitrichs 2 (27.0–36.1) 9 (3.0–5.0) 31.5 ± 2.2 9 4.1 ± 0.4 4/4 45 ??/??? (28.5–44.1) 9 (3.6–5.3) 37.5 ± 3.4 9 4.5 ± 0.4 3/3 50 ??/???

M p-mastigophores (30.0–49.6) 9 (4.4–8.0) 34.6 ± 3.3 9 5.6 ± 0.8 4/4 42 ??/??? (34.4–48.0) 9 (4.8–6.5) 41.6 ± 3.1 9 5.8 ± 0.4 3/3 45 ??/???

Filaments

Basitrichs (11.4–22.3) 9 (2.0–4.1) 14.8 ± 2.6 9 2.8 ± 0.5 4/5 40 ?/?? (12.8–19.1) 9 (2.0–3.3) 15.6 ± 1.4 9 2.7 ± 0.3 4/4 50 ??/???

M p-mastigophores 1 (14.0–22.5) 9 (3.2–6.0) 17.1 ± 2.1 9 4.7 ± 0.6 5/5 47 ??/??? (12.9–22.6) 9 (3.2–5.5) 18.2 ± 1.7 9 4.3 ± 0.6 4/4 45 ?/??

M p-mastigophores 2 (32.0–43.4) 9 (5.0–7.3) 38.3 ± 3.1 9 5.8 ± 0.6 5/5 47 ??/??? (33.6–47.3) 9 (4.9–7.0) 41.0 ± 2.6 9 5.8 ± 0.4 4/4 45 ?/??

Acontia

Basitrichs 1 (13.0–24.8) 9 (2.0–3.3) 17.8 ± 2.9 9 3.0 ± 0.1 6/6 66 ??/??? (12.6–24.1) 9 (2.0–3.6) 18.0 ± 2.6 9 2.9 ± 0.4 4/4 50 ??/???

Basitrichs 2 (35.0–53.5) 9 (3.0–5.0) 45.3 ± 3.6 9 4.3 ± 0.6 6/6 69 ??/??? (40.3–49.9) 9 (3.1–5.3) 44.9 ± 2.4 9 4.3 ± 0.5 4/4 51 ??/???

MA p-amastigophores (58.0–77.5) 9 (5.0–11.0) 66.7 ± 4.6 9 7.9 ± 1.2 6/6 57 ??/??? (64.2–78.0) 9 (6.4–8.8) 70.4 ± 3.2 9 7.4 ± 0.6 4/4 46 ??/???

Mean values marked with an asterisk are based on fewer than 40 capsules. Values from pooled samples

�X: mean length by mean width of capsules, SD standard deviation, S ratio of number of specimens in which each cnidae was found to number of specimens examined, N total number of capsules

measured, F frequency, ??? very common, ?? common, ? rather common, – sporadic, M microbasic, MA macrobasic

Po

larB

iol

(20

09

)3

2:7

03

–7

17

70

9

123

Etymology

The specific epithet honours the Alfred Wegener Institut

(AWI), Bremerhaven (Germany), which is dedicated to

polar research. Both species of Antipodactis gen. nov. were

collected during cruises sponsored by AWI.

Geographic and bathymetric distribution

Antipodactis awii sp. nov. has been collected from abyssal

waters (2,377 m) in the Arctic Ocean, in the eastern Fram

Strait (See Fig. 2).

Discussion

Differential diagnosis of Antipodactis species

Antipodactis scotiae sp. nov. and A. awii sp. nov. are dis-

tinguishable by internal anatomy, cnidae, and geographic

distribution. Although it is generally larger (36 vs. 25 mm

column height, respectively), A. scotiae sp. nov. has only

four cycles of mesenteries, whereas in A. awii sp. nov.,

a fifth and a partial sixth cycle are present. Similarly, A. awii

sp. nov. has more tentacles than A. scotiae sp. nov. (about

66 vs. 48, respectively). The retractor muscles of the per-

fect mesenteries differ: in A. scotiae sp. nov., the retractors

are more reniform and the fibers are approximately equal in

size and very densely packed (Fig. 4c); those of A. awii sp.

nov. are lobate, with more loosely packed fibers of variable

size (Fig. 7d). The parietobasilar muscles also differ: in

A. scotiae sp. nov. they are short and broad, equally

developed on both sides of the mesentery, and strongly

restricted (Fig. 4c, d); in A. awii sp. nov., the parietobasilar

muscles are long, and diffuse, with relatively few mesogleal

processes (Fig. 7c, d).

The types and size ranges of cnida are very similar in

the species of Antipodactis gen. nov. (Table 1; Figs. 5,

8). However, there are slight differences between the

species: we found holotrichs in the base of A. awii sp.

nov.; these are absent in A. scotiae sp. nov. However,

this difference may be an artifact of specimen condition:

holotrichs are not very abundant in A. awii sp. nov. and

the area where they are found is fairly eroded in most

specimens of A. scotiae sp. nov. Despite the overlap in

size ranges for most types of nematocysts, the micro-

basic p-mastigophores of the scapus are notably smaller

in A. scotiae sp. nov. than in A. awii sp. nov. Basitrichs

in the tentacles of A. scotiae sp. nov. can be differen-

tiated into a smaller and a larger category, however,

A. awii sp. nov. only has the larger category of basitrichs

in the tentacles. Finally, basitrichs in the actinopharynx

of A. scotiae sp. nov. are generally smaller (although

the range overlaps) than those in the actinopharynx of

A. awii sp. nov.

Antipodactis scotiae sp. nov. has been found in deep

Antarctic seas; A. awii sp. nov. has been found in the deep

Arctic seas. Both species have been collected in soft bot-

toms with or at the same locality as members of the genus

Kadosactis: A. scotiae sp. nov. with K. antarctica (Carlgren,

1928) and A. awii sp. nov. with K. rosea Danielssen, 1890.

As is true for A. awii sp. nov. and A. scotiae sp. nov., the

differences between the cnidae of K. rosea and K. antarc-

tica are very small (Rodrıguez and Lopez-Gonzalez 2005).

This is also the case for other deep-sea bipolar species

of actiniarians (e.g., Bolocera, see Riemann-Zurneck 1986),

Fig. 6 External anatomy of A.awii sp. nov. a Lateral view of

partly contracted specimen;

notice cuticulate tenaculi

(arrow) on scapus; b Lateral

view of expanded preserved

specimen; c Lateral view of

contracted preserved specimen;

d Lateral view of expanded

preserved specimen; notice

marked pedal disc. Scale barsa–d 10 mm

710 Polar Biol (2009) 32:703–717

123

suggesting that cnida size is not under strong selective

pressure in deep and polar seas.

Genera resembling Antipodactis gen. nov. in some

aspects are found in two families of acontiate actiniarians:

Kadosactis (Kadosactidae) and Sagartiogeton Carlgren,

1924 (Sagartiidae Gosse, 1858). Kadosactis and Sagarti-

ogeton share with Antipodactis gen. nov. a column divided

into scapus and scapulus the former usually with tenaculi,

cinclides, fertile stronger mesenteries, and acontia with two

size range of basitrichs and long p-amastigophores

(Kadosactis). Both include deep-sea distributed species.

Nevertheless, Antipodactis gen. nov. clearly differs from

both of them. Kadosactis is a very homogeneous genus

including three species that are very similar (Rodrıguez and

Lopez-Gonzalez 2005). In Kadosactis, the aboral bases of

the outer tentacles have thickened mesoglea, there is a

Fig. 7 Internal anatomy of

A. awii sp. nov. a Marginal

sphincter muscle; note

cuticulate tenaculi in the scapus

(arrow); b Cross section of the

column through the mesenteries

at the actinopharynx, showing

the cycles of mesenteries;

c Detail of parietobasilar

muscles and last cycles of

mesenteries; d Detail of the

directive mesenteries; e Detail

of the marginal column showing

a cinclide; f Cross section of a

tentacle showing the ectodermal

longitudinal muscles (arrow);

g Basilar muscles. Numbers

between pairs indicate the cycle

of mesenteries. ep epidermis; gagastrodermis; s siphonoglyph.

Scale bars a, c 1 mm;

b, d, e 2 mm; f, g 0.1 mm

Polar Biol (2009) 32:703–717 711

123

distal row of 22 endocoelic cinclides between the scapus

and scapulus, the number of mesenteries is similar distally

and proximally, only the first two of the three cycles of

mesenteries are perfect, retractor muscles are diffuse, and

parietobasilar muscles are weak. However, in Antipodactis

gen. nov. the aboral bases of the tentacles are not thick-

ened; cinclides are numerous (more than one per endocoel)

and they are not confined between the scapus and the

scapulus but are distributed along the scapulus only; mes-

enteries are more numerous proximally than distally and

more than three cycles are present; at least some of the

mesenteries of the third cycle are perfect; the retractor

muscles are restricted, and parietobasilar muscles are

differentiated and strong. Sagartiogeton is a heterogenous

genus including some abyssal species: S. abyssorum Carl-

gren, 1942; S. flexibilis (Danielssen, 1890); S. ingolfi

Carlgren, 1928, and S. verrilli Carlgren, 1942 (see Carlgren

1949). These species resemble those of Antipodactis gen.

nov. because they have long p-amastigophores and basi-

trichs in the acontia (see Carlgren 1942), but none of these

species has more than 12 pairs of perfect mesenteries, and

only in S. flexibilis are cinclides situated only in the

scapulus (Carlgren 1942).

Systematics of Antipodactidae

The acontiarian sea anemones (Carlgren 1949; Fautin

2008, see Table 2) are easily recognizable because of their

acontia. They are considered by some authors to be the

most complex and highly evolved group of sea anemones,

with the most diverse cnidom and remarkable structures

such as catch tentacles (Hand 1956). However, according

to others (e.g., Schmidt 1974), endomyarians are the more

highly derived group, having, in general, a more complex

cnidom. From the standpoint of molecular phylogenetics,

each of these groups are equally derived, being major

constituents of reciprocally monophyletic sister clades

within Actiniaria (Daly et al. 2008).

Despite having a straightforward diagnostic feature, the

acontiate actiniarians do not seem to form an exclusive

monophyletic group (Daly et al. 2008). Acontia are inter-

preted to have been lost several times, and are therefore a

shared primitive attribute of those taxa that bear them

(Daly et al. 2008). Although Carlgren’s (1949) classifica-

tion of acontiarians based on the nematocysts of their

acontia was pragmatic and not intended to be phylogenetic,

Hand (1956) proposed that cnidom of the acontia had

phylogenetic value and anticipated that these distinctions

would accord with phylogeny. According to Schmidt

(1969), p-mastigophores (p-amastigophores) have impor-

tant systematic value. However, classification and

ultrastructure features of actiniarian cnidae are not yet clear

enough to address phylogenetic questions. Molecular

evidence does not unambiguously support the value of

p-mastigophores (p-amastigophores) as a phylogenetic

character, at least in the acontia: both the parsimony and

likelihood phylogenetic trees of Daly et al. (2008), suggest

that the ancestral cnidom of acontiarian actiniarians

included both basitrichs and p-mastigophores (p-amastigo-

phores), and that one or both of these types have been lost

several times.

Acontia and their nematocysts are the principal

character distinguishing the eighteen families with acontia

(Carlgren 1949; Fautin 2008): one group of families

has both basitrichs and microbasic p-mastigophores (mic-

robasic p-amastigophores) in the acontia; others have only

Fig. 8 Cnidae of A. awii sp. nov. a Basitrich 1; b Basitrich 2;

c Microbasic p-mastigophore; d Basitrich 1; e Basitrich 2; f Microbasic

p-mastigophore; g Holotrich; h Basitrich; i Basitrich 2; j Microbasic

p-mastigophore; k Holotrich; l Robust spirocyst; m Basitrich;

n Microbasic p-mastigophore; o Basitrich 1; p Basitrich 2; q Microbasic

p-mastigophore; r Basitrich; s Microbasic p-mastigophore 1; t Micro-

basic p-mastigophore 2; u Basitrich 1; v Basitrich 2; w Macrobasic

p-amastigophore

712 Polar Biol (2009) 32:703–717

123

microbasic p-mastigophores (microbasic p-amastigophores)

or basitrichs. Antipodactidae fam. nov. is unique among

acontiate actiniarians in having macrobasic p-amastigo-

phores in the acontia (Figs. 5, 8, 9, 10); their acontia also

contain two morphologies of basitrichs (Figs. 5, 8). Antip-

odactidae fam. nov. is also distinctive in its combination

of anatomical features (Table 2). For instance, it shares a

column divided into scapus and scapulus, cinclides, and

mesenteries not divisible into macro- and micro-cnemes with

Aiptasiomorphidae Carlgren, 1949, Diadumenidae Stephen-

son, 1920, Haliplanellidae Hand, 1956 (considered a

synonym of Diadumenidae by Manuel (1981)), Kadosactidae,

Metridiidae Carlgren, 1893, and Sagartiidae. However, some

of these families are characterized as having a smooth

column (e.g., Aiptasiomorphidae, Diadumenidae, Halipla-

nellidae); others have a variable number of perfect

mesenteries (e.g., Metridiidae).

Based on traditional taxonomic characters, Antipodac-

tidae fam. nov. most closely resembles Kadosactidae (see

Table 2), differing primarily in the nematocysts of the

acontia. Although Rodrıguez and Lopez-Gonzalez (2005)

defined the microbasic mastigophores of the acontia in

Kadosactis antarctica as microbasic p-mastigophores

because they observed a distal tubule in discharged

Table 2 Tabular key of characteristics of acontiate families

Family Regions Cinclides Column Sphincter Basilar

muscles

Mesenteries Perfect

mesenteries

Fertile

mesenteries

Nematocyst of

acontia

Octineonidae Fowler, 1894 SS A C M A D 8 AF bs

Mimetridiidae Fautin, Eppard

and Mead, 1988

SS P S A P D 6 AF 2 bs, 2 ma

Diadumenidae Stephenson,

1920 (2)

SS P S A P N C6 AF bs, mp

Haliplanellidae Hand, 1956 (2) SS P S A P N 6 AF bs, ma, mp

Aiptasiomorphidae Carlgren,

1949

SS P S A/E P N 6 AF bs, mp

Metridiidae Carlgren, 1893 SS P S M P N V FS bs, ma, mb

Bathyphelliidae Carlgren, 1932 SS P S/Te M P D 6-12 AF 2 bs

Andvakidae Danielssen, 1890 SS P S/Te M A D 6 AF bs, ma

Hormathiidae Carlgren, 1932 SS P S/Tu/C M P N 6-12 V 2 bs

Kadosactidae Riemann-

Zurneck, 1991

SS P Tu/Te M P N 12 AF 2 bs, ma

Antipodactidae fam. nov SS P Te M P N C12 AF 2 bs, MA

Sagartiidae Gosse, 1858 SS/NR P S/Su/Te M P N V V bs, ma

Isophelliidae Stephenson, 1935 SS/NR P S/Te M P D 6-12 AF bs, ma

Sagartiomorphidae Carlgren,

1934

NR A S M P N 12 FSS ma

Nemanthidae Carlgren, 1940 NR A S M P N 6–12 FSS bs, mp

Haliactiidae Carlgren, 1949 NR A S/Su A A D 6 AF bs, ma

Aiptasiidae Carlgren, 1924 NR P S M P N 6 AF bs, mp

Acontiophoridae Carlgren, 1938 NR P S A P D C12 AF bs, 2 ma (1)

Ramireziidae Fautin, Eppard

and Mead, 1988 (3)

NR P S/Ve A P D 12 FS bs, ma (1)

Data obtained from familial diagnosis and species descriptions; accuracy of reports not re-examined. See Stephenson (1928) and Carlgren (1949)

for an explanation of the features

Column: S = smooth; Tu = with tubercles; Te = with tenaculi; Ve = with verrucae; Su = with suckers; C = with cuticle. Column regions

distinguishable: SS = scapus and scapulus/capitulum; NR = not regionated. Cinclides: P = present; A = absent. Sphincter: A = absent;

M = mesogleal; E = weak-diffuse endodermal. Basilar musculature: P = present; A = absent. Mesenteries: D = divisible into macro- and

micro-cnemes; N = not divisible into macro- and micro-cnemes. Nematocyst of acontia: bs = basitrichs; ma = microbasic amastigophores;

mb = microbasic b-mastigophores, mp = microbasic p-mastigophores; MA = macrobasic p-amastigophores; 2 = at least two ranges the

specified type of nematocyst (this might no represent all the diversity of the group). Perfect mesenteries: 6 = 6 pairs; C6 = at least 6 pairs,

usually more; 8 = 8 pairs; 6–12 = 6–12 pairs; C12 = at least 12 pairs; 12 = 12 pairs; V = number variable. Fertile mesenteries: AF = all or

all stronger mesenteries fertile; FS = at least first cycle of mesenteries sterile; FSS = first and second cycles of mesenteries sterile;

V = variable. (1) According to England (1990). (2) Sensu Carlgren (1949), according to Manuel (1981) Haliplanellidae is united within

Diadumenidae. (3) Some diagnostic characters of the type species doubtful; the family is probably a synonym of Diadumenidae according to

England (1990)

Polar Biol (2009) 32:703–717 713

123

capsules, this was short (ER, personal observation) and

thus can be interpreted as a vestigial tubule; furthermore,

the shape of the capsule and spination pattern corresponds

more closely to nematocysts correctly classified as

microbasic p-amastigophores. Thus, Kadosactidae is char-

acterized as having two morphologies of basitrichs and

microbasic p-amastigophores in the acontia. The micro-

basic p-amastigophores of Kadosactidae are similar to the

macrobasic p-amastigophores of Antipodactidae fam. nov.:

both have a slender, elongate capsule and a very wide,

strongly forked shaft. The shaft of the acontial microbasic

p-amastigophores in Kadosactidae is nearly as long as the

capsule, and thus only slightly shorter than those of the

macrobasic p-amastigophores of Antipodactidae fam. nov.

The cnidom of Diadumenidae is identical to that of An-

tipodactidae fam. nov. in terms of the types of nematocysts.

However, the morphology of the capsules varies consid-

erably in terms of the shape of the capsule and the

morphology of the undischarged tubule (Fig. 10). Fur-

thermore, the two families differ in basic anatomy

(Table 2).

We think it likely that Antipodactidae fam. nov. is more

closely related to Kadosactidae than to Diadumenidae, and

hypothesize that Kadosactidae and Antipodactidae fam.

nov. may be sister taxa. However, as both Kadosactidae

and Antipodactidae fam. nov. are exclusively deep or polar

in distribution (in contrast to Diadumenidae, whose

members are temperate, tropical, and shallow in their

distribution), the similarities we perceive between these

taxa may be the result of convergence. Because Antipo-

dactidae fam. nov. has a unique cnidom, particularly for the

acontia, we prefer to recognize it as a distinct family.

Cnidom of the acontia is critical for family level taxonomy

of the acontiate actiniarians (see Carlgren 1949). It is

possible that the macrobasic p-amastigophores of Antipo-

dactidae fam. nov. are modified from (or were modified

into) the microbasic p-amastigophores of Kadosactidae.

However, this is likely to be the case for the cnidom of

most taxa, as the various morphologies of nematocysts are

expected to have some historical relationship to one

another. Based on current taxonomic practice, the differ-

ences between species belonging to Kadosactis and to

Fig. 9 Macrobasic

p-amastigophores from the

acontia of Antipodactis gen.

nov. a and b Shafts from

macrobasic p-amastigophore

broken capsules; note the

differentiation between the

proximal and distal part of the

shaft (arrows); c Discharged

capsule of macrobasic

p-amastigophore; note

differences between ‘‘wrinkled’’

proximal part of the shaft

(labeled 1, see also inset) and

the ‘‘smooth’’ distal part of the

shaft (labeled 2, see also inset);

d detail of the transition

between the two different areas

of the shaft. Scale barsa–c 20 lm; d 10 lm

714 Polar Biol (2009) 32:703–717

123

Antipodactis gen. nov., warrant recognition of two families

rather than the broadening of Kadosactidae to include

Antipodactis gen. nov.

Macrobasic mastigophores

Macrobasic mastigophores occur in relatively few taxa; the

species that have them are not closely related and bear

these nematocysts in different structures. Cutress (1955)

hypothesized that macrobasic mastigophores were a relic

of an ancestral cnidom that has been modified in most

taxa. Nevertheless, capsule shape and inverted tubule

morphology can be very different (Fig. 10). The macro-

basic p-amastigophores of endomyarian actiniarians have a

rounded capsule and the tubule is clearly not isodiametric,

whereas those of acontiarians have a longer, more ovoid

capsule with a more isodiametric tubule. The macrobasic

p-amastigophores of aliciids have the longest tubule, which

seems differentiated into three parts (Fig. 10b, c). The

contention that macrobasic p-amastigophores are a primi-

tive nematocyst (e.g., Cutress 1955) is not conclusively

refuted by plotting the occurrence of macrobasic p-amas-

tigophores on the phylogeny of Daly et al. (2008) (Fig. 10).

Macrobasic p-amastigophores are not known to character-

ize a clade containing more than a single genus (or possibly

a group of genera, in the case of Aliciidae Duerden, 1895),

and so have either arisen multiple times or have been lost

repeatedly; losses would have to have occurred many more

times than gains, based on current phylogenetic hypothe-

ses. Nematocysts similar in shape of capsule and diameter

of shaft are present in closely related taxa (see above dis-

cussion of Kadosactidae and Antipodactidae fam. nov.),

Fig. 10 Variability of macrobasic p-amastigophores in a phylogentic

context. Exemplar macrobasic p-amastigophores are associated with

the clade to which their bearer belongs; capsules were all photo-

graphed at the same magnification (1,0009); tree is a consensus of the

likelihood and parsimony trees of Daly et al. (2008). Note that not all

members of the clade labeled ‘‘Acontiaria’’ have acontia; some

members are inferred to have lost these structures (see Daly et al.

2008). a Macrobasic p-amastigophore from the column of

Isoaulactinia hespervolita Daly, 2004. Those of other endomyarians

(Heteractis aurora) are similar; b Macrobasic p-amastigophore from

the pseudotentales vesicles of Lebrunia sp.; c Macrobasic p-amastig-

ophore from the column vesicles of Alicia mirabilis Johnson, 1861.

Those of other aliciids (e.g., Triactis spp.) are similar; d Macrobasic

p-amastigophore of Diadumene sp.; e Macrobasic p-amastigophore of

A. awii sp. nov. B ? A, Boloceroididae plus Aliciidae; MesoMesomyaria, Ed Edwardsiidae

Polar Biol (2009) 32:703–717 715

123

suggesting that an elongation of the tubule in a microbasic

p-amastigophore lead to the distinctive morphology of

macrobasic p-amastigophores, and that each morphotype of

macrobasic p-amastigophore evolved independently.

In the context of the diversity of acontiate actiniarians,

the most remarkable characteristic of Antipodactidae fam.

nov. is the macrobasic p-amastigophores in the acontia

(Table 2; Figs. 5, 8, 9). This type of nematocyst is not seen

in many actiniarian taxa (Carlgren 1945), and this is the

first time that this type of large and conspicuous nemato-

cyst has been reported in acontia. They have been reported

from other tissues in some members of only four families:

Aliciidae (in the column vesicles of Alicia Johnson, 1861

and Triactis Kunzinger, 1877, and in the pseudotentacles of

Lebrunia Duchassaing and Michelotti, 1860), Diadumeni-

dae (in the tentacles of some species of Diadumene

Stephenson, 1920), and Actiniidae Rafinesque, 1815 (in the

tentacles and the column vesicles of Isoaulactinia Belem,

Herrera and Schlenz, 1996) (Carlgren 1940, 1945; Belem

et al. 1996; Daly 2004; Daly and den Hartog 2004). Eng-

land (1988) reported macrobasic p-amastigophores from

the tentacles, column, actinopharynx, and filaments of

Heteractis aurora (Quoy and Gaimard, 1833); he consid-

ered the presence of this type of nematocyst important

enough to redefine and separate Heteractis Milne Edwards

and Haime, 1851 from other endomyarian genera and

reinstated the family Heteractidae Andres, 1883. Since no

further reliable revisions have been published apart from

that of England (1988) and a neotype of the type species

was designated, we consider the family Heteractidae valid.

Like Antipodactidae fam. nov., Heteractidae is diagnosed

by the occurrence of macrobasic p-amastigophores, rather

than a suite of unique anatomical attributes.

Weill (1934) distinguished macrobasic p-amastigo-

phores by the greater length (at least four times longer than

the capsule) of the thickened proximal shaft (part of the

inverted tubule, see Watson and Wood 1988) and also by

its special armature. Schmidt (1969) emphasized this last

feature to relate some microbasic p-mastigophores in

Bunodeopsis Andres, 1881 and Boloceroides Carlgren,

1899 to the macrobasic p-amastigophores of Alicia and to

relate the macrobasic p-amastigophores in the tentacles of

some Diadumene to microbasic p-mastigophores. Because

he stressed armature over the relative length of the shaft,

Schmidt (1969) did not recognize Weill’s (1934) distinc-

tion between macro- and micro-basic nematocysts.

England (1991) tried to reconcile Weill’s and Schmidt’s

(1969) classifications. England (1991) interpreted ‘‘mac-

robasic’’ mastigophores as having a long, differentiated

basal part of the shaft that coils within the undischarged

capsule; he did not consider, as Weill did, that the actual

length of the shaft must be at least four times longer than

the capsule.

Based on Weill’s definition, the macrobasic p-amastig-

ophores reported for the endomyarian taxa Heteractis and

Isoaulactinia probably cannot be considered macrobasic

(their shaft appears not to be four times longer than the

capsule, see England 1988, Daly 2004 or Fig. 10a). How-

ever, actually measuring the tubule of nematocysts is not

possible for most species because only formalin-fixed

material is available. Nonetheless, these capsules have a

distinct appearance, and conform to the definition England

(1991) formulated for undischarged macrobasic mas-

tigophores, and so we designate them as such here.

Nonetheless, we recognize that a comprehensive study of

the ultrastructure of this kind of nematocyst is necessary.

A discharged macrobasic p-amastigophore of Antipodactis

gen. nov. (Fig. 9) has a shaft about two and half times

longer than the capsule, and is apparently devoid of a

terminal tubule. The shaft is differentiated, as required by

England’s (1991) definition: the spination of the proximal

part of the shaft is distinct from that of the distal shaft

(observed as a more wrinkled proximal part vs. a more

smooth distal part, see Fig. 9). The wrinkled proximal part

of the shaft is shorter than the distal smooth part, usually

about the same length of the capsule.

Acknowledgments Special thanks to Dr. Joseph Maria Gili (Insti-

tuto de Ciencias del Mar, Barcelona), Prof. Wolf Arntz (Alfred

Wegener Institute, Bremerhaven), and Prof. Angelika Brandt (Zoo-

logical Institut and Zoological Museum, Hamburg), for making

possible the participation of ER and PJLG in the Antarctic cruises.

Thanks to Mercedes Conradi (Universidad de Sevilla) who collected

the Antarctic material that started this manuscript, and to Melanie

Bergmann (AWI), who provided the material of A. awii sp. nov. We

gratefully acknowledge the officers and crew of the R/V Polarstern,

and many colleagues on board during the ANDEEP-I cruise for their

valuable assistance. Abby Reft (Ohio State University, Columbus) is

thanked for her useful comments on cnidae. Thanks to the reviewers

Daphne Fautin, Verena Haussermann, and Nadya Sanamyan whose

comments greatly improved this manuscript. Support was provided by

a MCT-CSIC grant (I3P-BPD2001-1) to ER, and Spanish CICYT

projects: REN2003-04236, REN2001-4269-E, and CGL2004-20141-

E. Additional support was provided by NSF EF-0531763 to MD. This

is ANDEEP publication number 112.

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