Megapogon crispatus Jenkin 1908

• Main Authors: Alvizu, Adriana, Xavier, Joana R., Rapp, Hans Tore
• Format: Other/Unknown Material
• Language: unknown
• Published: 2019
• Subjects: Biodiversity; Taxonomy; Animalia; Porifera; Calcarea; Leucosolenida; Achramorphidae; Megapogon; Megapogon crispatus; Antarctic; Burton; Winter Quarters Bay; Antarc*
• Online Access: https://zenodo.org/record/5584079; https://doi.org/10.5281/zenodo.5584079

Megapogon crispatus Jenkin, 1908 (Figs 17 A–H; Table 13) Original description. Jenkin 1908, p. 41, pl. XXVII and XXXVIII, figs 131–136. Type locality. Winter Quarters Bay, Antarctic. Synonym and citations. Megapogon crispatus, Brønsted 1931, p. 32; M. crispatus, Burton 1963, p. 93. Material examined. Holotype: BMNH-1907.8.6.131, (two specimens and slides). Winter Quarters, Antarctic, National Antarctic Expedition (HMS Discovery). Morphology. Vase-shaped without fringe but with a well-developed oscular collar. Colour whitish in ethanol. Surface villose due to long diactines that cross the surface (Fig 17 A–B). Size of the fragment 2.4–3.1 mm long, 1.5–1.8 mm wide and 0.1 mm thick. Aquiferous system is leuconoid with spherical choanocyte chambers of similar size than inhalant cavities (Fig 17C). Skeleton. Skeleton inarticulated and composed of diactines, microdiactines, triactines and chiactines. Tetractines are found only in the oscular area (Figs 17B, 17D). Cortical skeleton composed of tangential triactines (Fig 17E) and of large projecting diactines which are bent towards the proximal end (Figs 17 B–E, 17G). Two types of microdiactines with spines are placed irregularly on the surface (Fig 17E). These microdiactines are also present amongst the atrial spicules, and around the choanocyte chambers (Figs 17F). Chiactines and few triactines form the atrial skeleton, with their unpaired actines pointing to the surface, and the paired actines giving support to the atrial wall. Tri- and tetractines of the same size, laid tangentially with the unpaired actines pointing downwards, are forming the oscular collar (Fig 17D). The oscular fringe is mainly composed of slightly shorter diactines, and by diactines similar to those found in the cortical skeleton but longer and thinner. It was not possible to measure the spicules from the oscular region, because they were broken or not easily visible in the sections. Spicules. Diactines: large and curved towards the distal end which has a knob. Proximal end hastate (Figs 17 A–B, ...