Aaptos pernucleata ( Carter, 1870 )

Rützler, Klaus, Piantoni, Carla, Van, Rob W. M. & Díaz, Cristina, 2014, Diversity of sponges (Porifera) from cryptic habitats on the Belize barrier reef near Carrie Bow Cay, Zootaxa 3805 (1), pp. 1-129 : 40

Aaptos pernucleata ( Carter, 1870)

( Figure 22 )

Synonymy and references. Aaptos aaptos (Schmidt, 1864) : Wilson (1902): 338; Storr (1964): 42, tab. 9; Kelly-Borges and Bergquist (1994): 304, fig. 2, pl. Ia; van Soest (2002a): 228, fig.1 (including synonymy). Trachya pernucleata Carter (1870) : Kelly-Borges & Bergquist (1994): 316: fig. 7.

Material. USNM 1191320, Reef flat East of Carrie Bow Cay, 0.5 m, underside of corrugated roofing tile; K. Ruetzler, col. 1 May 1974. USNM 1228969, 1228970, Curlew Bank, forereef slope (wall), 50-150 cm inside framework cave, ceiling, 20 m; C. Piantoni & M. Parrish, col. 22 Aug 2012. USNM 1228971, Curlew Bank, forereef slope (wall), framework cave, 18 m; C. Piantoni & M. Parrish, col. 25 Aug 2012.

Comparative material from the subtropical-tropical western Atlantic (Table 1).

External morphology. Encrusting to irregularly cushion-shaped with orange-yellow, blueish gray, to brownish surface, whitish, yellow, to ochre choanosome. Some overgrown in part by other encrusting sponges (for instance, Plakinastrella onkodes ). Surface smooth to warty and hispid, interior porous, consistency firm but elastic (stone hard when dry).

Skeleton structure. Larger spicules (strongyloxeas) radiate in bundles from the interior toward the surface where they end brush-like. Ectosome solidified by palisades of smaller styles that fill the space between the brushes of the larger spicules.

Spicules. There are three size classes of monactines (for measurements see Table 1). Large strongyloxeas (I), robust, slightly curved, thickest in the middle and tapering toward one pointed and one thinly rounded end; medium-size strongyloxeas (II), many modified to typical styles but widest in the center or lower third (toward pointed end); a third (ectosomal) spicule type are small styles (III), some modified to subtylostyles, straight or curved.

Ecology. Found near Carrie Bow Cay on the lower surfaces of platy coral rock and similar substrates in the subtidal zone (0.5 m) of the reef flat and in small caves to 20m on the forereef slope; partially encrusted by other sponges, for instance, Phorbas amaranthus , Plakinastrella onkodes . Elsewhere (Gulf of Mexico, in particular) the species was also collected in shallow reef caves and in dredge hauls from 30 to over 50 m depth.

Distribution. The material reviewed for this study suggests a distribution ranging from East off Georgia and Florida to western Florida and the entire Gulf of Mexico and Caribbean Sea. Specimens, in addition to the present material from Belize and the eastern Gulf of Mexico, were reported from the upper (northern) Florida Keys ( Storr, 1964), Puerto Rico ( Wilson, 1902) and Bonaire, Netherlands Antilles (Kobluk & van Soest, 1989), and of course the type locality, Veracruz, Mexico ( Carter, 1870).

Comments. Based on external appearance and spicule types (large strongyloxeas, medium-sized strongyloxeas and styles, and small styles and subtylostyles), this species seems close to the Mediterranean Aaptos aaptos . Dimensions of the strongyloxeas, however, allow us to separate three species that occur in the subtropicaltropical western Atlantic (Table 1). A. pernucleata stands out with the most distinctive strongyloxea shape, thick center and slim rounded end, very similar to those of A. aaptos but only about 70% of their mean length (roughly 1100 versus 1500 µm, on average). A. bergmanni de Laubenfels (1950), described from Bermuda and also found in the upper Florida Keys ( Storr, 1964) and a cave in the Bahamas, has much shorter and slimmer (about half the diameter) strongyloxea than A. pernucleata and transitions to styles are more common. A. lithophaga ( Wiedenmayer, 1977) , found in the Bahamas and in one cave in Bermuda, was synonymized with A. pernucleata by van Soest et al. (2013b) but from our review it seems closer to A. bergmanni , except for the longer type I strongyloxeas. A possible fourth species in the region, A. duchassaingi (Topsent, 1889) from the Banc de Campêche, needs to be reexamined because only the maximum dimensions of its spicules were reported (800 x 25 µm), not enough to assign it to or separate it from any of the other species. More material, live observations, and molecular methods will be needed to further clarify the taxonomy of Aaptos in the western central Atlantic.

Figures

FIGURE 22. Aaptos pernucleata, spicules (drawn from light and scanning electron micrographs): a, strongyloxeas / styloids I; b, strongyloxeas / styloids II; c, styles / subtylostyles (III); d, magnified rounded ends of styles / subtylostyles III.