Trimuricea reticulata ( Thomson & Simpson, 1909 )

Samimi-Namin, Kaveh & Van Ofwegen, Leen P., 2016, A revision of Trimuricea Gordon, 1926 (Cnidaria: Octocorallia: Plexauridae) with the description of six new species, Zootaxa 4105 (1), pp. 1-44 : 32

Trimuricea reticulata ( Thomson & Simpson, 1909)

( Figs. 21 c, 24–25)

Echinomuricea reticulata Thomson & Simpson, 1909: 206 .

Trimuricea reticulata ; Gordon 1926: 516, fig. 3; Grasshoff 1999: 48, fig. 80. Not T. aff. reticulata ; Samimi-Namin & van Ofwegen 2009a: 43. (= Trimuricea persica n. sp.).

Material: Syntypes BMNH 1933.3.13.18Andamans, “Investigator", coll. Sir J.A. Thomson. The jar was painted as a type specimen and has a pencil written label at the bottom which has in addition to the above: L.M. Macfadyen 1922; BMNH 1933.5.3.103, same data but labelled as a young colony; BMNH 1925.11.24.44, same data, tiny fragment.

Description (colony shape after Thomson & Simpson 1909). Grasshoff (1999: 48) mentioned he reexamined the holotype, but Thomson & Simpson never designated a holotype. In the British Museum three specimens labelled Echinomuricea reticulata are present; one specimen stored under BMNH 1933.5.3.103, labelled as being a young colony, with the same data as the fragment examined by us (BMNH 1933.3.13.18; Figure 21 c); and BMNH 1925.11.24.44, a tiny fragment. The main part of the material of this species is stored in the Indian Museum in Kolkata and unavailable for study. Thomson and Simpson described one specimen that is 20 cm high and 16 cm wide, and another 18 cm high and 11 cm wide. Both are branched in one plane and have a holdfast. In the larger colony the stem measures 2.5 mm at the base and tapers gradually to 1.5 mm near the tip. The diameter of the branches is almost uniform throughout. Abundant anastomoses are present. Polyps are closely set to each other, and situated all around the branches. The calyces are dome shaped, up to 0.5 mm in height and 1 mm in diameter. A young pearl oyster is attached to one of the branches of the smaller specimen and there is a cirripede gall overgrown by polyp-bearing coenenchyme on the larger specimen, which also bears a young crinoid.

The points have triradiates ( Fig. 24 a), along with curved, hockeystick or boot-shaped sclerites, or spindles ( Fig. 24 b), 0.10–0.30 mm long. The upper ray of the triradiates and upper part of the spindles is slightly echinulate or smooth for up to 0.23 mm. The collaret spindles are 0.20–0.44 mm long ( Fig. 24 c); the middle of the sclerites has very few tubercles as do the ends. A few tentacle scales are present, up to 0.10 mm long ( Fig. 24 d).

The calyces have thornscales, 0.10–0.38 mm long, with one long smooth or slightly echinulate thorn up to 0.23 mm long; the base of the thornscales has sparse, simple tubercles ( Fig. 24 e, 25a).

The coenenchyme has narrow spindles, 0.15–0.65 mm long, with simple tubercles ( Fig. 25 b); some of these spindles are triradiate or have a side branch.

Colour. The preserved colony is light brown. All sclerites are colourless. There is no information about the colour of live colony and polyps.

Remarks. Gordon’s description of the specimen she identified as Trimuricea reticulata does not agree with the description of T. reticulata by Thomson & Simpson (1909). Gordon’s specimen has smaller spindles in the coenenchyme (up to 0.5 mm long versus 0.65 mm for Thomson & Simpson’s material), and smaller polyp sclerites (up to 0.32 mm long versus 0.7 mm for Thomson & Simpson’s material). However, we found polyp sclerites of intermediate length (up to 0.44 mm long) and consider the measurements of the polyp sclerites by Thomson & Simpson incorrect and that Gordon’s measurements were correct. Noteworthy, in the original description of Echinomuricea reticulata is that Thomson & Simpson mentioned the presence of “irregular clubs”, which actually are thornscales upside down.

It is not possible to tie the two colonies of the original description to the fragment we examined because Thomson & Simpson did not show any image and also the colony sizes they mentioned do not agree with what we re-examined. We can only assume we re-examined part of one of those two colonies.

This species mostly resembles Trimuricea bicolor , T. inermis ( Nutting, 1910) , and T. omanensis as these species have sclerites with only simple tubercles. T. reticulata differs in having a much longer, more or less smooth, thorn on the thornscales (up to 0.23 mm long for T. reticulata compared to up to 0.15 mm long for the other three species), which also have a more complex base.

Figures

FIGURE 21. Holotype colonies: a, T. persica n. sp., RMNH Coel. 38785; b, T. spinosa n. sp., RMNH Coel. 39317; c, T. reticulata (Thomson & Simpson, 1909), BMNH 1933.3.13.18; d, T. tuberculosa n. sp., RMNH Coel. 39318.

FIGURE 24. Sclerites of T. reticulata (Thomson & Simpson, 1909), BMNH 1933.3.13.18: a, point triradiates; b, point spindles; c, collaret spindles; d, tentacle scales; e, calicular thornscales.

FIGURE 25. Sclerites of T. reticulata (Thomson & Simpson, 1909), BMNH 1933.3.13.18: a, calicular thornscales; b, coenchymal spindles.