Hymedesmia (Hymedesmia) prostrata Thiele 1903

• Main Authors: Van, Rob W. M., Kaiser, Kirstie L., Syoc, Robert Van
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2011
• Subjects: Biodiversity; Taxonomy; Animalia; Porifera; Demospongiae; Poecilosclerida; Hymedesmiidae; Hymedesmia; Hymedesmia prostrata; North Atlantic
• Online Access: https://doi.org/10.5281/zenodo.5623665; http://treatment.plazi.org/id/0D0987D3FFF5FFD420A615F1EAEEFE3D

Hymedesmia (Hymedesmia) prostrata Thiele, 1903 (Figs 9 A–E) Hymedesmia prostrata Thiele, 1903: 955, fig. 20. Material examined. MNHN DCL 4042–B, Jean-Louis Etienne Expédition Clipperton 2005, station 18, 55 m, on dead corals, 20–01–2005, 1 specimen. MNHN DCL 4049–A, Jean-Louis Etienne Expédition Clipperton 2005, station 42, 8 m, on dead corals, 31–01– 2005, 1 specimen. Description. Thinly encrusting (Fig. 9 A), microhispid, covering areas of several cm2. No apparent oscules or porefields. Consistency soft, easily damaged. Skeleton. Megascleres are arrenged erect on the substrate (hymedesmioid), loose bundles or single tornotes at the surface. Spicules. Anisotornotes, acanthostyles and arcuate isochelae. Tornotes (Fig. 9 B) with one end mucronate and slightly swollen, the other end tapering evenly rounded, 114– 137.3 –156 x 1.5–2.5 µm. Large acanthostyles (Fig. 9 C) densely spined at the head, more sparingly spined towards the pointed end, 149– 186.2 –233 x 7 – 8.4 –10 µm. Small acanthostyles (Fig. 9 D) heavily spined all over, 57– 65.3 – 78 x 4 – 5.6 –6 µm. Arcuate isochelae (Fig. 9 E) in a large size range but not divisible in categories, alae frequently somewhat irregular or partially split, 12– 17.5 –21 µm. Ecology and distribution . Encrusting undersides of corals over a wide depth range; reported from Île Clipperton, Ternate and Aldabra. Remarks. The identification with Thiele’s Ternate species is made on the basis of generally similar spicular characters, although the tornotes of Thiele’s specimen were slightly longer (200 µm). Sizes of acanthostyles (240 and 90 µm) are close and particularly the aniso-condition of the tornotes is similar to our specimen. Hymedesmia records from shallow Indo-Pacific waters are few. Sponges of the genus Hymedesmia are typical deep-water / cold-water species, with relatively few known from shallow-water and even fewer from shallow coral reef environments. Most species have been described from the North Atlantic, and only half a dozen were recorded from the Pacific and none ...