Calthropella Pachataxa lithistina (Schmidt, 1880)

Van Soest, Rob W. M., Beglinger, Elly J. & De Voogd, Nicole J., 2010, Skeletons in confusion: a review of astrophorid sponges with (dicho-) calthrops as structural megascleres (Porifera, Demospongiae, Astrophorida), ZooKeys 68, pp. 1-88 : 57-58

Calthropella Pachataxa lithistina (Schmidt, 1880) Figs 28 A–D29A–E

Pachastrella lithistina Schmidt 1880: 68, pl. 9 fig. 3; Topsent 1923: 6, fig. 1.

Pachataxa lithistina ; de Laubenfels 1936: 179; Van Soest and Hooper 2002: 133, fig. 2E.

Material examined.

Holotype MCZ 6384, Blake Exped. 1878-79, Grenada, 160 m. Further type material: schizoholotype fragment MZUS P0095 (not examined) and two type slides in ZMB, nr. 6870 (not examined).

Description.

Thick plate (Fig. 28), size 9 × 6 cm, thickness 2 cm. Surface different on both sides, oscular side (Fig. 28B) with irregularly scattered oscules of 1-2 mm diameter each elevated on small hillocks; the poral side (Fig. 28C) with numerous small openings irregularly arranged in groups separated by areas without such openings. Edges of the plate smooth, without pores or oscules. Colour of the dried specimen pale yellow with a pinkish brown tinge. Consistency hard, slightly crumbly (dry condition). In cross section (Fig. 28D), there is a dense interior yellow-white mass, riddled with thin canals; at the periphery there are subdermal spaces underneath a 1 mm thick crust.

Skeleton: a confused mass of calthrops with at the periphery a dense mass of ataxasters, which are also strewn in the interior.

Spicules: calthrops, spheroxyasters, ataxasters.

Calthrops (Fig. 29 A–B), highly variable in size, cladi conical and straight, occasionally the fourth cladus is lacking or underdeveloped, rarely one of the cladi is longer, 78 –315.5– 705 × 14 –46.1– 94 µm, cladome 144 –460.2– 990 µm.

Spheroxyasters (Fig. 29C), with thick center and smooth conical rays of unequal length, some appear undeveloped, many are broken; diameter (including the rays) 7 –9.7– 12 µm.

Ataxasters, of many different shapes and sizes (Fig. 29 D–E) from simple elongate-ovate rhabds to complicated forms looking as if two or more rhabds are fused, surface uniformly microspined; size (length of longest axis × length of shortest axis) 9 –28.7– 48 × 4 –18.1– 34 µm.

Habitat.

Deep water, 160 m.

Distribution.

Only known from the type locality, off Grenada.

Remarks.

The type material was assigned by Van Soest and Hooper (2002) to a lectotype in the Strasbourg Museum and a paralectotype in the Museum of Comparative Zoology, Cambridge, USA, but it is virtually certain that both are fragments of a single specimen. Thus, both the alleged lectotype and paralectotype are now assigned to the same holotype as schizoholotypes. Calthropella (Pachataxa) lithistina differs from both other Pachataxa species in the shape (large plate with different oscular and poral surfaces) and in the large variations in ataxaster shapes and sizes.