Heterometra schlegelii (AH Clark, 1908b )

Goh, Shawne, Quek, Randolph Z. B., Foo, Sze Hui, Tay, Teresa Stephanie, Messing, Charles G. & Huang, Danwei, 2023, Phylogeny and morphology of Himerometroidea (Echinodermata: Crinoidea) feather stars in Singapore, Raffles Bulletin of Zoology 71, pp. 92-105 : 99

Heterometra schlegelii (AH Clark, 1908b)

( Fig. 4 )

Himerometra schlegelii AH Clark, 1908b: 223 .

Amphimetra schlegelii, AH Clark, 1909a: 7 .

Antedon schlegelii, AH Clark, 1909e: 117 .

Holotype. ZMC CRI-41 .

Material examined. Sta. DR 1, Raffles Lighthouse, start 01°10.125′N, 103°45.419′E, end 01°10.211′N, 103°45.517′E, 38.5– 38.3 m, 20 May 2013, (n = 1; SS-0395, ZRC. ECH.0353); sta. DR125, Sister’s Island , start 01°12.416′N, 103°49.858′E, end 01°12.433′N, 103°49.817′E, 30.8– 25.3 m, 30 May 2013 (n = 4; SS-3643-1, ZRC.ECH.1970; SS-3643-2, ZRC.ECH.1971; SS-3643-3, ZRC.ECH.1972; SS-3643-5, ZRC.ECH.1974); sta. SUB07 , SE of St. John’s Island, start 01°12.671′N, 103°51.232′E, end 01°12.607′N, 103°51.145′E, 53.7– 34.8 m, 19 April 2016 (n = 8; TR0318aii, ZRC.ECH.1659; TR0320i, ZRC.ECH.1660; TR0320ii, ZRC. ECH.1661; TR0324i, ZRC.ECH.1652; TR0326ai, ZRC. ECH.1662; TR0326aii, ZRC.ECH.1653; TR0328ii, ZRC. ECH.1654; TR0328ii, ZRC.ECH.1671); sta. SUB16 , SW of St. John’s Island, start 01°12.646′N, 103°50.650′E, end 01°12.612′N, 103°50.495′E, 42.6– 25.9 m, 27 May 2016 (n = 3; TR0657bi, ZRC.ECH.1647; TR0657bii, ZRC. ECH.1672; TR0730, ZRC.ECH.1667); sta. SUB18 , SE of St. John’s Island, start 01°12.682′N, 103°51.222′E, end 01°12.646′N, 103°51.135′E, 59.9– 45.2 m, 2 June 2016 (n = 3; TR0971, ZRC.ECH.1651; TR0982, ZRC.ECH.1655; TR0985, ZRC.ECH.1658); SUB36 , SW of St. John’s Island, start 01°12.649′N, 103°50.659′E, end 01°12.617′N; 103°50.613′E, 40.6– 38.3 m, 30 June 2016 (n = 18; TR2135, ZRC.ECH.1663; TR 2136i, ZRC.ECH.1650; TR 2136ii, ZRC.ECH.1664; TR2139, ZRC.ECH.1649; TR 2144ii, ZRC.ECH.1668; TR2145, ZRC.ECH.1648; TR2146, ZRC. ECH.1673; TR2147b, ZRC.ECH.1657; TR2148ai, ZRC. ECH.1669; TR2148aii, ZRC.ECH.1646; TR2150a, ZRC. ECH.1656; TR2152, ZRC.ECH.1665; TR 2154i, ZRC. ECH.1674; TR 2154ii, ZRC.ECH.1670; TR2161, ZRC. ECH.1675; TR2162, ZRC.ECH.1676; TR 2164i, ZRC. ECH.1666; TR 2164ii, ZRC.ECH.1677); sta. TB16, Outside Eastern Boarding Ground A, start 01°13.537′N, 103°53.793′E, end 01°13.437′N, 103°53.556′E, 98– 89.5 m, 21 May 2013 (n = 1; SS-0408, ZRC.ECH.0362); sta. TB28, Singapore Port Limit, start 01°13.036′N, 103°52.820′E, end 01°13.058′N, 103°52.746′E, 97.6– 94.3 m, 22 May 2013 (n = 1; SS-1085, ZRC.ECH.0389); sta. TB142, Eastern Bunkering A, start 01°17.838′N, 104°04.157′E, end 01°17.851′N, 104°03.953′E, 28.8– 28.7 m, 31 May 2013 (n = 1; SS-4304, ZRC.ECH.1969) .

Diagnosis. IIIBr absent; distal brachials exceedingly short, discoidal; distal margins of middle brachials everted ( Fig. 4A ); brachials laterally flattened; cirri ~ 20 mm long with usually 30–35 cirrals; longest cirrals as long as broad in adults; aboral cirral spines sharp; between 10 and 14 arms (possibly up to 20), usually 70–80 mm long in adults, but can be as short as 45 mm in some adults and 16 mm in juveniles; proximal pinnules have prominent thin carinate extensions on the side towards the arm tip ( Fig. 4E ) (modified from Messing & Tay, 2016).

Description. Centrodorsal hemispherical to discoidal with flat aboral apex, with one juvenile having a marginal row of beads on aboral apex (SS-4304, ZRC.ECH.1969); radials beaded in juveniles, while adults show variation in smooth and beaded radials with combination of both on one specimen (SS-3643-3, ZRC.ECH.1972); cirri XV (XI–XXI in local specimens), arranged in 1–3 irregular rows; number of cirrals in local specimens 13–33; in juveniles, longest cirrals can be longer than broad, and distal cirrals possess weak carinations ( Fig. 4D ), triangular carinate projections (red and yellow arrows, Fig. 4C : carina broad, usually distally directed), or spines (white arrow, Fig. 4C ; carina narrow, usually aborally directed); some aboral cirral spines begin as triangular carinate projections proximally but become progressively narrower and aborally directed distally ( Fig. 4C ); in adults, middle to distal cirrals bear distally-directed spines or blunt tubercles on aboral surface. IIBr sometimes IIBr2, mostly IIBr4(3+4); brachials plain ( Fig. 4B ) or everted; proximal pinnules with thin carination on basal segments, absent in one juvenile (SS-1085, ZRC.ECH.0389) ( Fig. 4H ); P 1 almost always shortest and most slender, except P 1 wider than P 2 in one specimen (SS-0408, ZRC.ECH.0362); distal edge of proximal pinnules sometimes ornamented with small spines on both interior and exterior lateral edges ( Fig. 4G ); carination at middle pinnulars in one adult specimen transitions from outer to inner ridge ( Fig. 4F ).

Remarks. Messing & Tay (2016) noted that Singapore specimens may have more arms, up to 19 or 20. The carinate extensions on proximal pinnules are absent on the holotype. Depth range in Singapore 103– 27 m, inhabiting rocky, sandy substrates or laterite gravel.

Figures

Fig. 4. Heterometra schlegelii morphological characters. A, distal margins of middle brachials everted in adults (red arrows); B, middle brachials of distal margins in juveniles, plain and not inverted (red arrows); C, middle cirrals of some juveniles bearing distally directed triangular projections near the distal margin of the cirral (red arrow) with projection gradually moving away from the distal edge in more distal cirrals (yellow arrow). Distal cirrals have sharp, aborally directed triangular projections or spines (white arrow); D, other juveniles have weak carinations on distal cirrals (red arrow); E, thin carinate extensions on basal segments of proximal pinnules (red arrows); F, extensions transition at middle pinnulars from facing arm tip (red arrows) to facing away from arm tip (yellow arrows) in adults; G, distal edge of distal pinnulars on proximal pinnules showing spinular side projection (yellow arrow) and premature rim of serration (white arrow); H, basal segments of proximal pinnules of one juvenile (SS-1085, ZRC.ECH.0389) bearing very weak carinate extensions on basal segments.