Description

Description: The holotype is a fragile, lace-like, encrusting sponge, attached to a rock. It was originally 15 cm long, 6 cm wide and 3 – 4 mm in height. It has a very smooth surface, with five scattered oscules each approximately 3 mm in diameter. The aquiferous channels radiating from the oscules are clearly visible through the transparent ectosome (Fig. 4 A). The circular ostia are 0.3 mm in diameter and form rows / chains on the surface between the oscular-fed aquiferous channels (Fig. 4 B). The external morphology resembles the common cloacal zooid formation on the ascidian Botrylloides. The sponge is white and translucent on deck and after preservation. Skeleton: The ectosomal skeleton is composed of tangential styles, arranged in a multispicular reticulated pattern around the circular ostia. The small diancistras (II) and some of the large diancistras (I) occur on the underside of the ectosomal layer. The choanosomal skeleton consists of bundles of ascending styles supporting the ectosomal layer (Fig. 4 C). The large diancistras form rosettes around the supporting bundles (Fig. 4 D). Spicules: The megascleres are styles, which are abundant, fusiform, straight, sharply pointed, and thickest in the centre. The blunt end is much narrower than the middle and has a rounded style end. They measure 301 – (428) – 489 x 7.4 – (12.2) – 17.4 μm, n = 30 (Fig. 4 H, I). The large diancistras (I) are common, with a subtle shaft twisted at the most 45 o, the thin sharp fimbriae running most of the length of the inner surface except for the middle quarter and around the notch (Fig. 4 E). They measure 109 – (127) – 141 x 5.9 – (8.2) – 12.3 μm, n = 39. The smaller thin diancistras (II) are less common, with the shaft twisted 90 o and bent in the centre (Fig. 4 F). They have an almost incomplete ala, but with the fimbriae being extensive along the shaft. They measure 33.8 – (46.2) – 64.6 x 1.2 – (2.1) – 5.8 μm, n = 35. The rare toxas are larger than the diancistras, and similar in length to the styles and measure 266 – (298) – 350 x 3.0 – (4.5) – 5.7 μm, n = 5 (Fig. 4 G).

Common Names

Taxonomic Hierarchy

Kingdom: Animalia

Phylum: Porifera

Class: Demospongiae

Order: Merliida

Family: Hamacanthidae

Genus: Hamacantha

Species: Hamacantha melliflura Ekins & Hooper, 2023