Cryptasterina hystera, Dartnall, Alan J., Byrne, Maria, Collins, John & Hart, Michael W, 2003

Dartnall, Alan J., Byrne, Maria, Collins, John & Hart, Michael W, 2003, A new viviparous species of asterinid (Echinodermata, Asteroidea, Asterinidae) and a new genus to accommodate the species of pantropical exiguoid sea stars, Zootaxa 359, pp. 1-14 : 4-7

Cryptasterina hystera sp. nov. Dartnall and Byrne

Synonymy:

Patiriella pseudoexigua Dartnall, 1971 in part Patiriella pseudoexigua Byrne in Prestedge, 1998 Patiriella pseudoexigua Byrne et al., 1999

Etymology: The species name (Gk hystera = womb) refers to the viviparous habit of this animal and maintains the reproductive metaphor ( vivipara , parvivipara ) used in naming other exiguoid species

Diagnosis. An exiguoid species of Asterinidae ; abactinal plates of the papular areas mostly bi­lobed accommodating a single papula; few secondary abactinal plates present; hermaphrodite, viviparous, intragonadal brooder.

Holotype: MTQ collection number G2205, alcohol preserved specimen with part emergent juvenile, R = 10.2 mm collected 0 6.01.2003, S and R McKillup.

Type locality: Statue Bay, central Queensland, Australia, lat. 23°09'.997 S, long. 150° 46'.492 E.(fig. 3b) Beach number 1367 ( Short, 2000). Habitat: mid intertidal under small rocks on mud and muddy sand (McKillup pers. com.)

Paratypes: collection data as for holotype; MTQ G2206 (3 specimens: R 9.5 mm, 9 mm, 10.5 mm); NMV F96255 (3 specimens: R 10 mm, 10.7 mm, 10.1 mm); TM 2987 (3 specimens: R 10 mm, 10.7 m, 10 mm).

Other material examined. 10 specimens, data as for types; four specimens, Statue Bay, Queensland, coll. S McKillup, September, 2000 (authors' collection). One specimen Bargara, Queensland, Beach number 1502 ( Short, 2000), coll R. Endean 10.1.1953, British Museum Natural History number 1953.5.18.8

Description

Up to 12 mm R; rays five (one specimen with 4 rays; n=24), form pentagonal to subpentagonal, R:r from 1.22–1.7); body thick, flat orally, flattened dome aborally, acute angle at margin; small subtriangular madreporite (about 1 m across at R = 11.5 mm).

Abactinal surface with papulate areas more extensive than non­papulate areas; few secondary plates; abactinal plates closely imbricate, rarely with more than one papular pore associated with each papular space; projecting proximal edges of plates mostly crescentic, lobed; metapaxillar ridge low, not prominent; disc not distinct; proximal interradial areas papulate similar to radial areas; distal interradial areas apapulate; abactinal spinelets granular, about 150 m long, broader at base with constricted waist and capitate tip, terminally spinous; carinal and disc plates carry 7–12 spinelets in an irregular double row; distal interradial plates with a cluster of 5–7 spinelets; superomarginal plates elongate in the radial axis carrying a double row of up to eight spinelets; inferomarginal plates with a projecting flange of about seven webbed spinelets form the margin to the disc.

Actinal plates and spines in regular series from furrow to margin; first complete series runs from the third ambulacral plate distal to the mouth plates and comprises eight plates at R = 11.5 mm; interradial area proximal to the mouth plates carrying 2–5 loosely imbricate plates often aspinous; other actinal plates with a tapered conical spinelet up to 650 m long: a very few plates may carry two spines close to the edge of the disc. Adambulacral plates with one subambulacral spine (occasionally two) 500 m long proximally, reducing distally; furrow spines commonly in webbed pairs, occasional triplets near the mouth and unpredictably along the furrow and singletons distally; furrow index 1.6 –1.85. Five oral spines on each oral plate and one suboral spine on the actinal surface of the plate.

Intragonadal brooder; viviparous; no evidence of fissiparity; pedicellariae absent.

Colour: In life dark olive green above and paler green underneath (MB personal observation; Fig. 3a ).

Distribution: Currently known only to these authors from the type locality and Bargara and Kinka Beaches, central Queensland, despite extensive searches northward along the Queensland coast.

Developmental biology: Cryptasterina hystera sp.nov. had ovotestes with oogenic and spermatogenic regions and the gonads are gravid from September to November. The gonads contained juveniles ( Fig. 3 ) in December and January. This sea star has large buoyant eggs (440 µm diameter; SE= 6.0 µm, n=8) that are a gold/orange colour with a dark vegetal pole.

Developing embryos and brachiolaria larvae were interspersed with gametes in the gonad. The larvae are highly buoyant with a well developed brachiolar complex of 3 brachia and an adhesive disc. In the laboratory the larvae exhibited typical settlement behaviour exploring the substratum and adhered to the substratum with their brachia and adhesive disc.

Newly settled juveniles were an amber colour due to the presence of yolk reserves. It took three weeks for the mouth opening to develop and by this time these juveniles had a well developed skeleton.

In aquaria, juveniles (800 µm diameter, SE=6.3, n=10) with two pairs of tube feet in each radius emerged from the gonopore on the aboral surface of the adults. These juveniles had a mouth opening, a functional digestive tract and a well­developed skeleton. Newly released juveniles were white, due to the colour of the skeleton and appeared to lack residual maternal nutrients.

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Figures

FIGURE 3. a) Colour in life Cryptasterina hystera n. sp. (at left) and Cryptasterina pentagona (at right) Photograph. M Byrne. b) Statue Bay, central Queensland. Boulder and cobble beach. Type locality for C. hystera n. sp. Photograph. S McKillup.