Agelas cerebrum Assmann

Parra-Velandia, Fernando J., Zea, Sven & Van Soest, Rob W. M., 2014, Reef sponges of the genus Agelas (Porifera: Demospongiae) from the Greater Caribbean, Zootaxa 3794 (3), pp. 301-343 : 325-327

Agelas cerebrum Assmann , van Soest & Köck, 2001

Fig. 10

Etymology from Latin, meaning brain; brain-like appearance.

Agelas cerebrum Assmann, 2000: 37 , pl. 2; Assmann et al., 2001: 361, Fig. 1 ; Zea et al., 2009. Agelas conifera ; Alcolado, 2002: 61 (in part).

[Non: Agelas conifera ( Schmidt, 1870) (a valid species)]

Material and distribution. Holotype examined at the Zoölogisch Museum Amsterdam ( ZMA – POR 15603), collected at the deep reef slope of Chub Cay, Bahamas, 32 m. The material reviewed here (INV– POR 925, 937) was also collected in the Bahamas.

This species seems restricted to the Bahamas area (see also Assmann 2000; Zea et al. 2009) and Cuba ( Alcolado 2002). Therefore, we consider it as a Bahamian-Greater Antilles species. Our specimens were found from 12 to 18 m in depth, abundant at 14– 15 m.

Description. Shape as robust tubes, often as thick as barrels or vases, single or in groups, sometimes laterally fused. Height up to 25–35 cm, diameter up to 12–16 cm (single tube, Fig 10 A) or 22–30 cm (fused tubes, Fig 10 B). Pseudoscula 3–6 cm in diameter, collared by a narrow (5–8 mm, Fig 10 C) membrane, opening into atria with a rather constant diameter throughout its depth. The external colour can be salmon to light reddish brown; internal colour orange to brownish orange; when dry the colour becomes light reddish brown. Pinacoderm sustained by tracts of spicules protruding from main fibres.

The external surface is rough and characteristically convoluted throughout the surface ( Fig 10 D); the convolutions are 2–8 cm long, 2–3 cm wide and 4–5 cm deep, longer when connected to each other; isolated ones with a key-hole or kidney aspect; internal wall of the convolutions is lined by a thick bright membrane similar to the internal membrane of the atrium. The surface is even in a ring around pseudoscula. Oscules 0.5–1.5 cm in diameter, scattered along the atrium internal walls. The central area of the external convolutions have scattered tiny round oscules (<1.2 mm) conspicuous in dry specimens. Consistency in life is strongly spongy but tough, almost incompressible; when dry it becomes harder. Choanosome is dense with channels 5–10 mm in diameter.

Skeleton composed of echinated and heavily cored (5–9 spicules per cross section) primary fibres (80–170 µm in diameter), echinated and not cored secondary fibres (50–90 µm in diameter) and rarely echinated tertiary fibres (30–60 µm in diameter). The acanthostyles are straight with 5–7 spines per whorl; length 72–167 (115±21.9) µm, width 3–10 (7±1.4) µm and 8–20 (13±2.5) whorls per spicule. Detailed lengths, widths and average number of whorls are shown in Table 2.

Remarks. This species usually grows in deep exposed areas. Dr. P.M. Alcolado (pers. comm.; Alcolado 2002) believes that A. conifera , A. tubulata and A. cerebrum are variations of the same species (vis. A. conifera ). However, here we keep these species separate from predominant morphological characteristics which can be ascertained when one compares in the field co-existing individuals. In the Bahamas, A. cerebrum is easily identified underwater by its notable salmon colour (different from the other local Agelas ) and remarkably convoluted aspect of the external surface. At San Andres Island, some rather thick tubes of A. tubulata have portions of the surface with deep crevasses, which resemble those of A. cerebrum . A. tubulata can be distinguished by its brownish to orange colour, longer spicules, and by the absence of small round oscules in the interconvolution areas, when these occur. Perhaps these convolutions are simply the result of growth adjustments when body walls thicken, in order to maintain enough irrigation through the aquiferous system (P.M. Alcolado, pers. comm.). However, the absence of small round oscules in thick, crevassed specimens of A. tubulata argues against this. P.M. Alcolado (pers. comm.) has found A. cerebrum in Cuba as robust, single or laterally fused tubes, or large single or grouped cones fused at the base (with a large oscule on the top), at depths of about 15 to 20 m; colour, medium brown.

We compared the holotype of A. cerebrum and our material with the holotype A. conifera , and although spicule sizes slightly overlap (also mentioned by Assman et al. 2001), the distinctive shape of A. cerebrum (barrel/vaselike tubes plus deep grooves and convolutions) separate it from A. conifera (branch with cones wider than taller). Whether these differences are ecological or species specific, remains to be determined. The record of Assmann (2000) gives photos of this species but not a description; being an unpublished thesis from which the complete description was made, it is not taxonomically valid as to have priority.

Figures

FIGURE 1. SEM images of Agelas. A) Spicules of A. conifera holotype. B) Spicules of A. clathrodes holotype. C) to D) Fibre skeleton with primary and secondary fibre echination, in A. citrina (C), A. dispar (D, curved fibres) and A. conifera (E). F) Detail of the skeleton of A. conifera showing coring spicules in a broken primary fibre. G) Detail of the skeleton of A. citrina with its long spicules.

FIGURE 10. Photographs of Agelas cerebrum from the Bahamas. A) Holotype at ZMA; single tube. B) Three tubes and a lower left additional bud. C) Close up view of a pseudosculum; note the rough surface aspect between grooves. D) Close up view of the side; note the salmon color and the oscules in between grooves.