Havelockia ferali andamanensis, Thandar, 2017

Thandar, Ahmed S., 2017, Two new subfamilies, three new species and a new subspecies of dendrochirotid sea cucumbers (Echinodermata: Holothuroidea), Zootaxa 4365 (4), pp. 410-420 : 412-414

Havelockia ferali andamanensis n. subsp. Figure 1

Etymology. This subspecies takes its name from its type locality in Mergui Archipelago, Andaman Sea.

Diagnosis. A cylindrical, slightly ‘U’-shaped subspecies of H. ferali , up to 22 mm in length; colour in alcohol yellowish to off-white. Tube feet small, non-retractile. Anal teeth absent, anal papillae sometimes evident. Tentacles 10, in 8 + 2 arrangement. Radial and interradial plates of calcareous ring unfragmented, broadly joined; posterior processes of radial plates fragmented, of approximately same length as radial plates; most radial plates slightly prolonged before bifurcation. Polian vesicle single; stone canal short, suspended in dorsal mesentery; madreporite ‘bean’-shaped. Ossicles of body wall comprise only tables, with irregular, elongated or quadrangular or circular disc, 57–97 µm, perforated by numerous holes. Spire of two pillars, sometimes arched, sometimes terminally bifurcate, with few teeth, sometimes reduced to knobs on surface of disc, crowns non-perforate. Supporting tables of tube feet with curved disc and spire ending in couple of teeth; end-plates present. Introvert with tables with disc smaller than that of body wall tables, 47–73 µm; spire ending in few to many teeth. Tentacle deposits as open rosettes, 15–43 µm.

Holotype. NHMUK 1886.2.2.21, “Palour Bay, Margui” (locality not clearly legible on label but according to the accession record supplied by the curator at NHMUK, it should read Palaw Bay, Mergui, Myanmar, on the Andaman Sea); received by NHMUK from the Indian Museum.

Paratypes. NHMUK 1886.2.2.22-24, other data as for holotype, 6 specimens.

Description. All specimens cylindrical, slightly ‘U’-shaped, colour in alcohol yellowish to off-white. Largest specimen (holotype) 22 mm in length, 5 mm in breadth in mid-body ( Figure 1 Aa). Smallest specimen contracted, 10 mm in length and 7 mm in breadth. Calcareous ring and tentacles lost except in holotype and in all but one 20 mm paratype (NHMUK 1886.2.2.22), where it is extruded but still attached to body.

Holotype ( Figure 1 Aa)

Length 22 mm. Tube feet small, non-retractile, scattered, some serial arrangement visible, more numerous ventrally. Suckers more or less of equal diameter as tube feet. Anal teeth absent, anal papillae sometimes evident. Tentacles 10, well branched, whitish, in 8 + 2 arrangement, longest 5 mm, mid-ventral two approximately one third length of others.

Calcareous ring complex ( Figure 1G ), radial and interradial plates not fused but broadly joined by a membrane; radial plates anteriorly bifurcate, some slightly prolonged posteriorly before bifurcation into paired processes of approximately same length as radial plates; interradial plates anteriorly pointed, posteriorly slightly concave. All plates intact, non-fragmented but radial processes broken up into a series of fragments. Polian vesicle single, slightly elongated; stone canal short, mid-dorsal, attached in dorsal mesentery; madreporic body ‘bean’- shaped. Respiratory trees short, well branched, very transparent, left slightly longer than right, but not reaching end of calcareous ring. Gonad in two tufts of short ‘banana’-shaped tubules, apparently immature or spent in holotype (and all dissected specimens). Longitudinal muscles thin, thread-like. Retractor muscles thicker, more so anteriorly where they insert on the anterior tips of the radial plates, ventral retractors originating more posteriorly at approximately one third body length from posterior end.

Ossicles of body wall comprise tables only ( Figure 1E ), with variously-shaped disc, either elongated, quadrangular or circular, perforated by numerous holes, rarely any difference between the four central holes and others. Margin of disc smooth; spire of two pillars of moderate height, sometimes arched, sometimes terminally bifurcate, with few teeth, often reduced to knobs on surface of disc; disc size 57–97 µm (mean 77 µm). Supporting tables of tube feet ( Figure 1F ) with curved disc and two-pillared spire ending in couple of teeth, spire often triangular; disc perforated by a few central holes and one or two terminal holes; end-plates present, with no regular arrangement of holes except in some plates in which medial holes are smaller. Disc of anal tables 53–87 µm (mean 65 µm) ( Figure 1C ). Introvert deposits comprise only tables ( Figure 1D ) with disc smaller than that of body wall tables, 47–73 µm (mean 64 µm), spire two-pillared, ending in few to numerous teeth, top of spire sometimes perforated. Tentacle deposits comprise only open rosettes of a variety of form ( Figure 1B ), 15–43 µm in length (mean 29 µm), mostly concentrated in the stalk, few and scattered elsewhere.

Remarks. In colour, size and form of the ossicles, the current specimens come very close to H. ferali Cherbonnier, 1988 described from Madagascar but I am inclined to consider the Palaw Bay material as representing a new subspecies. Cherbonnier’s holotype of H. ferali came from Tuléar, and his paratypes from Nosy Bay. Cherbonnier states that his description is valid for the holotype only. There are slight variations between the Madagascar and the current Palaw Bay material. These variations are here described as it is suspected that they may reflect geographic rather than specific differences. Cherbonnier describes the tube feet as being long with some radial seriation. In the Palaw Bay material the tube feet are short and appear to be mostly scattered. The calcareous ring described by Cherbonnier, while definitely of the sclerodactylid type, shows the radial plates as being enlarged before bifurcation and the posterior processes arise at the level of the posterior end of the interradial plates. In the two Palaw Bay specimens in which the calcareous ring is present, one (paratype NHMUK 1886.2.2.22) does show some fragmentation of the plates but both in this specimen and the holotype, there is no enlargement of the radial plates before bifurcation. The writer examined some extant type material of H. ferali (EcHh 7077, 7076 and 3591) at the MNHN and found that in paratype 7077, the calcareous ring is slightly fragmented, the interradial plates are in a single series and the radial plates into two series, but there was no convincing evidence that this was due to preservation. In specimen numbered 7076, the originally dissected one, also shows a similar calcareous ring and in specimen 3591, the interradials have incipient subdivisions and the radials are deeply cleft with a double series of plates. The body wall and introvert ossicles of the extant type material are identical to those illustrated by Cherbonnier (1988). Although fragmentation is present in the type material as well as in one of the current specimens, the ring of both subspecies ( H. ferali ferali and H. ferali andamensis ) appears clearly of the sclerodactylid type. The ossicles of the current material are similar to those of the type illustrated by Cherbonnier except that the spire tops are not as dentate and those of the anal region are not perforated. Hence a comparative study of both the Madagascar and the Palaw Bay material indicates that there are some differences which are here regarded as geographic variations in distantly separated populations. It is for this reason that the Palaw Bay material is here described as a new subspecies of H. ferali .

Family Thyonidae Panning, 1949

Subfamily Thyonininae n. subfam.

Diagnosis. A subfamily of the family Thyonidae with body wall ossicles comprising mostly slender curved rods perforated by usually a single or few holes at each end.

Type genus. Thyonina Thandar, 1990 (here designated).

Type species. Thyone articulata Vaney, 1908 (designated by Thandar 1990).

Remarks. This genus was erected by Thandar (1990) for the southern African Thyone articulata Vaney, 1908 , which remained monotypic since then and was thought to be strictly a southern African genus. The two new species described below are now referred to this genus which after all is not monotypic anymore.

Figures

FIGURE 1. Havelockia ferali andamanensis n. subsp. A. Specimens entire (a: holotype, NHMUK 1886.2.2.21; b: paratype, NHMUK1986.2.2.22-24); B. Tentacle ossicles; C. Anal ossicles; D.Introvert ossicles;E.Body wall tables; F. Tube feet tables; G. Part of calcareous ring (dorsal). (B–F drawn to same scale).