Pachastrella pacoi, Van Soest & Meesters & Becking, 2014

Van Soest, Rob W. M., Meesters, Erik H. W. G. & Becking, Leontine E., 2014, Deep-water sponges (Porifera) from Bonaire and Klein Curaçao, Southern Caribbean, Zootaxa 3878 (5), pp. 401-443 : 407-410

Pachastrella pacoi new species

Figures 4a–d , 5a–g

? Pachastrella abyssi sensu Van Soest & Stentoft, 1988: 34 , pl. 5 figs. 3–6, text-fig. 15 (not: Schmidt, 1870, based on Cárdenas & Rapp, 2012: 18, Fig. 9 )

Material examined. Holotype: RMNH Por. 9255, Caribbean Netherlands, Bonaire, locality Cargill (Dive 4), 112.08°N 68.2938°W, depth 232 m, on a limestone rockwall, coll. L.E. Becking & E. Meesters, field nr. BON4/ BDR064 , 1 June 2013 . Paratype: RMNH Por. 9248, Caribbean Netherlands, Bonaire, locality Curoil Dock (Dive 3), 112.137°N 68.286°W, depth 159 m, in the sand at the base of a limestone rockwall, coll. L.E. Becking & E. Meesters, field nr. BON3 / BDR033 , 31 May 2013 .

Additional fragment: RMNH Por. 9246 Caribbean Netherlands, Bonaire, locality Curoil Dock (Dive 3), 112.137°N 68.286°W, depth 203 m, coll. L.E. Becking & E. Meesters, field nr. BON3/ BDR028 , 31 May 2013 .

For comparison: Pachastrella abyssi sensu Van Soest & Stentoft, 1988 , ZMA Por. 05301, 05312, Barbados, off Paynes Bay , 153 m , 1978.

Description. Variable in shape ( Figs. 4a–d ), but rather persistently shallow cup-shaped, bumpy-irregular outside, optically smooth inside. Largest size in situ (the paratype, Figs. 4c–d ) up to 16 cm in diameter, 15 cm high, of which a fragment of 4 x 2.5 x 2.5 cm was retrieved. The holotype ( Figs. 4a–b ) is about half the size of the paratype, and two fragments were preserved, each of which is 2 x 2 x 2 cm in size. If the Barbados material is indeed conspecific then size may be up to 20 cm high. Surface rough to the touch, consistency hard, incompressible, somewhat crumbly. Oscules not apparent, but in the cup-bottom of the paratype a cluster of small openings is visible. Colour alive greyish white, on deck and in preservation light beige.

Skeleton. Ectosome consisting of a dense layer of oval microrhabds, pierced here and there by the cladi of subectosomal calthrops. Choanosomal skeleton thoroughly confused, without radiate architecture. Calthrops of all sizes are strewn randomly in the interior, separated by few canals and open spaces. Microscleres abundantly present throughout the choanosome.

Spicules ( Fig. 5a ) Calthrops/short-shafted triaenes, oxeas, amphiasters, microrhabds.

Short shafted calthrops-like triaenes ( Fig. 5a–b ) in an extreme size range, with smooth, conical cladi, often slight curved at the apices, rarely bifid at one of the cladi, but no dichotriaenes were detected, size range extreme, perhaps divisible arbitrarily in a larger size, cladi 348– 825 –1260 x 50– 143 – 204 µm, and a smaller size, 66– 168 –252 x 10– 23 – 32 µm; overall range 66– 1260 x 10 –204 µm.

Oxeas ( Fig. 5c ), long, straight, relatively thin, sharply pointed, invariably broken in the slides, reconstructed to be up to 3 mm long, 24–30 µm in diameter; short, probably foreign oxeas present in most slides, 150–200 x 5–6 µm.

Amphiasters ( Fig. 5d ) in a single uniform size and shape, 14– 15 – 17 µm, with 10–18 rays.

Microrhabds/microstrongyles in three distinct categories, (1) short fat oval rhabds ( Fig. 5e ), rather coarsely spined, vaguely centrotylote, forming a thick layer at the surface and abundantly present throughout the choanosome, 9– 13 –15 x 5.5– 6 – 7 µm, (2) rather rare longer ( Fig. 5f ), more finely spined rhabds, 18–24 x 5–6 µm, (3) thin, long, somewhat curved, occasionally wavy rhabds ( Fig. 5g ), with spines frequently bearing secondary spines (named microrhabdose streptaster by Cardenas & Rapp, 2012), 28– 34 – 42 µm.

Ecology and distribution. On limestone rockwalls and in the sand at their base, depth range 153–232 m. Bonaire, Barbados.

Etymology. The name honors Dr Paco Cárdenas, in acknowledgement for his great efforts to make sense of the phylogeny and classification of tetractinellid sponges.

Remarks. Our material is close to but apparently not the same species as the holotype of P. abyssi Schmidt, 1870 , redescribed recently by Cárdenas & Rapp (2012). Aside from the usual Pachastrella complement, this has rare dichotriaenes and more robust amphiasters and also spiraster-like amphiasters, unlike our specimens. Furthermore, the diversity of microrhabds in P. abyssi is larger with fat curved and elongate microstrongylote forms added to the oval ones. It is likely but not entirely certain that our material is the same species as the Barbados material of Van Soest & Stentoft (1988). In the Barbados specimens the microrhabdose streptasters, which were only rarely observed in our specimens, are quite common and thicker. The oval microrhabds/ microstrongyles of the Barbados specimens are thinner and more centrotylote, and the largest calthrops have smaller cladi than in the present material. According to Cárdenas & Rapp (2012) the variability of specimens of Pachastrella is unusually large making delimitation of closely similar species difficult, so for the time being we assume the Bonaire and Barbados specimens to be conspecific. Molecular research may be helpful in determining species diversity in the Caribbean Pachastrella . Cárdenas & Rapp (2012) insist that Pachastrella abyssi has a complement of small smooth oxeas, suggested to have been overlooked by Van Soest & Stentoft (1988). However, many of such oxeas are likely foreign as they appear typically haplosclerid in shape and size. Part of our present material also possessed lots of such small oxeas, 150–200 x 6–10 µm, but this is attributed to a green-yellow thin crust seen to grow over part of the specimens in photos made of them on deck.

Figures

FIGURE 4. Pachastrella pacoi n. sp., habits in situ and on deck, a–b. Holotype RMNH Por. 9255, c–d. Paratype RMNH Por. 9246.

FIGURE 5. Pachastrella pacoi s.p., SEM images of spicules of the holotype RMNH Por. 9255, a. overview of spicules, b. calthrops of various sizes, c. oxea, d. amphiaster, e. oval microrhabd, f. elongate oval microrhabd, g. thin long microrhabd with complicated spines.

FIGURE 9. Caminus carmabi n. sp., a. habit in situ of the paratype RMNH Por. 9249, b. habit on deck of holotype RMNH Por. 9245, c–g. SEM images of the spicules of the holotype RMNH Por. 9245, c. calthrops, c1. detail of cladus of calthrops, d. strongyle, d1. details of strongyle, e. sterraster, e1. juvenile sterraster, e2. detail of surface of sterraster, f. spherules, g. oxyasters.