Triptolemma endolithicum, Van, Rob W. M., 2009

Van, Rob W. M., 2009, New sciophilous sponges from the Caribbean (Porifera: Demospongiae), Zootaxa 2107, pp. 1-40 : 4-6

Triptolemma endolithicum n. sp.

( Figs 1 A–G)

Holotype. ZMA Por. 21062, Colombia, Cartagena area, Islas del Rosario, Isla Pavitos, 10.1275 N - 75.7688 W, 25 m, 25-10-1990, coll. M. Kielman #S141.

Description. Sponge insinuating inside two fragments, 1 x 1 x 2 cm and 1 x 1 x 0.5 cm, of an original single piece of coral covered on the outside by Diplastrella megastellata ( Hechtel, 1965) ( Hadromerida , Spirastrellidae ). No traces of the sponge were detected on the upper/outer side of the coral, but inside it several corridors and holes of approx. 1 mm diameter and 5–10 mm long are filled with tissues of the new species. Live color not noted, beige colored in alcohol. Consistency soft.

Skeleton. Confused, no apparent organization.

Spicules. Mesotriaenes (dichomesotriaenes, mesocalthrops), small amphitriaenes, oxea-like spicules, amphiasters, microrhabds. Measurements presented here are based on 10 spicules instead of 25, due to large variability of shape and sizes of the various types.

Mesotriaenes( Figs 1 A–B), predominantly dichomesotriaenes, large size differences among spicules, but no clear size categories, protocladi 48- 148.4 -302 x 12 - 27.6 -48 µm, deuterocladi 12- 33.2 - 72 x 6 - 10.5 -20 µm, tritocladi 6- 23.5 - 60 x 5–7 µm; rhabdomes, conical, sharp-pointed, 24- 45.9 - 62 x 20-25 µm; cladomes up to 400 µm.

Mesocalthrops ( Fig. 1 C), rare, long cladi up to 108 x 10 µm, short cladi 15–62 µm.

Oxea-like spicules ( Figs 1 D–E), usually with cladose ends, rarely symmetrically sharply pointed, 186- 267.0 - 372 x 10 - 17.0 -28 µm.

Small amphitriaenes, rare, rhabd 15 x 2 µm, cladi 15 x 2 µm.

Amphiasters ( Fig. 1 F), with short rhabd and long rugose or lightly spined rays, 9- 11.4 -13 µm, rays 3–4 µm long.

Microrhabds ( Figs 1 G–H), in two distinct size categories, short relatively fat, 14- 15.8 - 18 x 2 - 2.9 -4 µm, long, slim, slightly sinuous, densely spined, 32- 33.7 - 37 x 0.5 µm.

Ecology. Insinuating in dead coral material, at 25 m depth.

Etymology. The name refers to the endolithic habit, occupying spaces within dead coral fragments.

Remarks. This is the first record of the genus Triptolemma from the tropical western Atlantic. The genus so far numbers four accepted species ( Maldonado, 2002; van Soest et al. 2008 on line): T. cladosum ( Sollas, 1888 as Triptolemus ) from deep water (250 m) off the Kai Islands, Indonesia, T. intextum ( Carter, 1876 as Pachastrella ) from deep water (674 m) off the SW coast of Portugal, T. incertum ( Kirkpatrick, 1903 as Triptolemus ) from deep water (150–180 m) off the east coast of South Africa, and T. simplex ( Sarà, 1959 as Triptolemus ) from a shallow cave (0–1 m) in the Mediterranean. A fifth species, T. parasiticum ( Carter, 1876 as Pachastrella ) from unknown origin is considered a junior synonym of T. intextum , although the proof for this is still wanting. The description by Carter (twice, in 1876: 410, pl. XVI fig. 50, and 1880: 60, as Samus ) remains uncritical with respect to the other species. The material is considered lost, so we will remain in doubt over its true affinities. The name Samus parasiticus was also used for a specimen occupying spaces within calcareous algae in the Gulf of Mannaar, India, which possibly is conspecific with T. cladosum (but again this remains undecided). Samaai (2006), without explanation, referred Triptolemma incertum to the genus Dercitus Gray (1867b) , but Kirkpatrick's description leaves no doubt that it belongs to Triptolemma .

The genus is predominantly of deep-water occurrence, but the present new species and T. simplex share a sciophilous shallow-water habitat.

Maldonado (2002) in his re-description of the type species refers to the spined microrhabds as sanidasters, but this appears incorrect; both Sollas' and Sarà's description use the term microrhabd and Maldonado's own drawing (l.c. p. 159, fig. 14D) makes it clear that this cannot be considered a sanidaster. Similarly, the streptaster microscleres are not metasters, but amphiasters or spirasters as they clearly show a (short) rhabd. The alleged presence of small smooth oxeas in T. cladosum and T. incertum is drawn into doubt by Maldonado (l.c.) and we concur with this, as the endolithic habit of the sponges makes it virtually impossible to avoid contaminations with spicules of neighbouring sponges. Still, we report the presence of large oxeas in the same size range and thickness as the triaenes, which are certainly proper to the sponge, but may be interpreted as reduced triaenes.

The new species differs from T. cladosum in the generally more robust, larger and thicker triaenes (protocladi of T. cladosum only up to 52 x 21 µm, against up to 300 x 48 µm in our new species); other features appear generally similar, with long microrhabds somewhat smaller (up to 27.6 µm) than T. endolithicum n. sp. (up 37 µm). It differs from T. intextum (which is not fully described by Carter) in the smaller mesotriaenes (figured spicule has a cladome of approx. 140 µm) and its deep-water East Atlantic occurrence make conspecificity with our new species unlikely; by proxy, we assume the same for T. parasiticum . T. incertum differs in the shape of the long spined microrhabds. These were not mentioned by Kirkpatrick, but subsequently described by Maldonado as present; the longer catergory is depicted (l.c. p. 159, fig. 14G) as oxea-like with pointed ends, wheras those of our new species are clearly strongylote. Other features including spicules sizes appear closely similar. The deep-water occurrence in East Africa makes conspecificity with our new species unlikely. T. simplex has smaller triaenes (cladome of the largest mesotriaenes up to 245 µm) and possibly has a second category of amphiasters/spirasters (but these could be contaminations). In summary, the new species has (1) larger upper size of the mesotriaenes than any other Triptolemma , (2) clearly separated categories of small fat microrhabds and long curved or sinuous microrhabds, both blunt-ending, shared with at least T. simplex , and (3) fat smooth oxeas often with cladose endings.

Figures

FIGURE 1. Triptolemma endolithicun n. sp., SEM images of spicules (Holotype ZMA Por. 21062). A – C. Various sizes and forms of mesotriaenes; D – E. oxea and detail of one of the proliferated apices; F. Amphiaster; G – H. Acanthose microrhabds in two size categories, G- 1 and H- 1 in the same magnification, G- 2 and H- 2 showing details of surface.