Calliaster childreni, Gray 1840

Mah, Christopher L., 2018, New genera, species and occurrence records of Goniasteridae (Asteroidea; Echinodermata) from the Indian Ocean, Zootaxa 4539 (1), pp. 1-116 : 86-87

Stellaster childreni Gray 1840

Figure 34 A–F

Gray 1840: 278; A.M.Clark 1993: 285; Hassan et al. 2017: 1 (as Stellaster childreni ) Retzius 1805 (as Asterias equestris , but see A.M. Clark 1993 for suppression of Stellaster equestris ) Stellaster equestris Retzius 1805: 12 ; Müller & Troschel 1842: 62, 128; Goto 1914: 411; Livingstone 1932: 246; Döderlein,

1935: 91; Koehler 1910: 79; Jangoux in Guille & Jangoux 1978: 53; Imaoka et al. 1991: 64; A.M. Clark 1993:

285(checklist); Liao & Clark 1995: 95; Shin & Rho 1996: 321, plate 15;Sastry 1998: 474; Marsh 2000: 24; Putchakarn &

Sonchaeng 2004: 420; Sastry 2005: 31; Sakthivel & Fernando: 1; Chamundeeswari et al. 2013: 2,4 (as Stellaster equestris ) Anthenea pentagonula James D.B. 1996: 133 –135, plates 1D (misidentified as “small size” A. pentagonula ), 2D.

Diagnosis. Stellate body (approximately R/r=2.2–2.5), disk thick, stout with triangular, strongly tapering arms, rounded, strongly convex disk ( Fig. 34A ). Abactinal, marginal, and actinal surface covered by granule-invested integument. Conical, pointed spines or tubercles variably present or absent on primary disk and carinal arm plates. Superomarginal plates convex, forming wide boundary around disk, abutted on distal arm region ( Fig. 34B ). Round, paddle-shaped spines on actinolateral edge along inferomarginal plates ( Fig. 34C ). Flattened, large spine present on each adambulacral plate, few to absent subambulacral accessories. Pedicellariae present or absent. Furrow spines four to five ( Fig. 34D ), sit on subactinal ledge in ambulacral groove.

Comments. Treatment herein follows A.M. Clark’s (1993: 285) suppression of “ Asterias (= Stellaster) equestris ” in favor of Stellaster childreni Gray 1840 in order to avoid the instability resulting from synonymy of the widely used Hippasteria phrygiana .

Stellaster childreni is a variable, widely occurring species as reflected by the approximately 13 subspecies or formae documented by Döderlein (1935). Although A.M. Clark (1993) lists these as synonyms, she also noted that these forms require re-evaluation, especially so in light of ongoing discoveries of cryptic species as molecular data.

In addition to Stellaster childreni, Stellaster includes five other species, Stellaster convexus from the Philippines Stellaster tuberculosus from “ China,”, and three species, Stellaster inspinosus, Stellaster princeps and Stellaster squamulosus primarily from the Indian Ocean coast of Australia. A.M. Clark’s (1993) checklist noted that the last major treatment of this group by Döderlein (1935) was “unsatisfactory.” Species boundaries between the six species of Stellaster, especially accounting for the high variation observed in Stellaster childreni , are poorly established and further review is necessary.

Functional Morphology & Gut Contents. Stellaster childreni is unusual among the Goniasteridae in that its complete adambulacral and oral spination is recessed below the plane of the actinal surface. The subambulacral spination for both the tube foot groove and the oral plate regions is composed of two to three enlarged, flattened paddle-like spines along the edge of actinal surface just above the recessed furrow spines ( Fig. 34D ). The flattened, paddle-like spines present on the inferomarginal plates ( Fig. 34C ) of this species are identical in shape to the subambulacral spines, but appear to be larger and directed at a different angle. These characters are interpreted as the primary digging apparatus for this species, which is known to occur on unconsolidated sediment bottoms, specifically on “compact sand.” Examination of gut contents in the individuals herein showed that those with strongly arched disks had stomachs filled with fine, dark sediment, including gastropod shells, worm tubes, hydroids and other organic debris ( Fig. 34F ). Approximately 1000 grains were measured along a 1.0 cm line. This species is contrasted with the similar Ogmaster capella , which is morphologically similar and is often found with coarse sediment in its gut (see account herein).

This is consistent with results from Hassan et al. (2017) who sampled Stellaster childreni from muddy and sandy bottoms. Prey items included mollusks, including gastropods, bivalves, and scaphopod mollusks, as well as seagrass and benthic foraminifera.

Color variation in Life. Deck shots of this species from Madagascar show it to be of light rose color with darker mottled patches interradially on the abactinal surface. The actinal intermediate areas form dark rose to purple triangular regions proximally bounded by a white border around the distal edges. The marginal plates are each colored with a light pink/purple and bounded by white. Chamundeeswari et al. (2013) documented this species from southeast India and noted its color as “purplish” on the aboral side and “purplish with creamy white” on the oral side, but with an image that appeared brown in their figure.

Coleman (2007) showed two color morphs of Australian Stellaster equestris (now Stellaster childreni ), a white and grey individual with a red spot on the disk and a solid brown individual with darker plates and a white actinal surface with brown proximal plates from the Northern Territories and Western Australia, respectively. The latter brown color variant showing the white actinal surface with brown proximal plates corresponds to the colors of “ Stellaster incei ” (a synonym of Stellaster childreni ) as described by H.L. Clark (1938).

Hassan et al. (2107) documented Stellaster childreni in Borneo with a light brown abactinal surface with a white actinal surface and dark grey spots on the actinal plates adjacent to the adambulacral furrow.

Deck images of this species from Japan and Korea (Imaoka et al. 1990, Shin & Rho 1996) show individuals with a solid brown to orange abactinal surface with a lighter white to tan actinal surface, with no actinal pattern. Images of this species from Singapore show it light brown to grey with dark arm bands and white spines.

These observations do not agree with the image of Stellaster childreni as shown by Gosliner et al. (1996). Subsequent review of their image indicates that their figured species is almost certainly Stellasteropsis rather than Stellaster, which would show the spines on the lateral sides.

Occurrence. Southern China and Japan, southern Asia region, Gulf of Thailand, Singapore, Borneo, Philippines, Indonesia, northern and western Australia (Montebello Islands), Sri Lanka region, southeast India, Red Sea, Arabia, East Africa, Madagascar. 0–600 m (depth range extended)

Material Examined. IE-2007-1011 Madagascar, 15° 48.39’S, 44°44.37’E, 50 m. Coll. Bouchet & Kantor , MIRIKY aboard N/ O Miriky, 9 July 2009, 2 wet specs. R=2.6, r=0.9, R=1.4, r=0.4; IE 2007 -4005 Sud-Ouest Pointe Barrow , Madagascar, 25°03'S, 44°00'E, 132– 153 m. Coll. Atimo Vatae, 2 wet specs. R=5.3, r=2.4; R=5, 0r=2.9 . IE- 2007-1057 West of Nosy-Bé, Madagascar 13°24’S, 47°57’E, 435–600 m, Coll. Bouchet et al . MIRIKY, 1 wet spec. R=>4.0, r=1.8, arms broken; IE-2007-1065 Madagascar 13°25’S, 47°57’E, 158 m, Coll. Bouchet et al . MIRIKY, 1 wet spec. R=4.5, r=1.8; IE-2007-4996 , Madagascar, 49– 52 m. Coll . ATIMO VATAE TP 11 . 4 wet specs. R=6.5 r=2.6; R=6.2 r=2.6; R=5.2 r=2.1; R=4.9 r=1.9 . IE-2007-4003 , Madagascar, 25°03’S 41°00’E, 135 m. Coll . ATIMO VATAE, N/O Nosy Be II, DW 3588 . R=5.3 r=2.1; R=5.2 r=2.1; R=4.6 r=1.9; R=3.4 r=1.2 .

Figures

FIGURE 34. Stellaster childreni Specimen IE-2007-1065.R=4.5, r=1.8 cm. A. Abactinal surface. Scale bar=1.0 cm. B. Closeup of abactinal surface showing interradial paired plates and superomarginals. Scale bar=0.5 cm. C. Lateral view showing paddle-shaped inferomarginal spines. Scale bar=0.3 cm. D. Closeup of furrow and adambulacral spination. E. Actinal surface. Scale bar=1.0 cm. F. Gut contents containing fine mud.