Cladocroce spatula

Cladocroce spatula (Lundbeck, 1902) (Figure 3, Table 2) Original description: Chalina spatula Lundbeck, 1902: 11, Pl. II, Fig. 3, Pl. VIII, Fig. 8–9. Synonyms: Haliclona spatula (Lundbeck, 1902) Material Examined Gulf of St. Lawrence: IML 11893, 49.1467N, 63.2727W, 241 m depth. Additional collected specimens are noted in Table 2. External appearance (Figure 3 A–C) Cladocroce spatula (Lundbeck, 1902) is stalked and spatulate with one or more flat, leaf-shaped lobes extending out from a central stalk. Specimens can reach 35 cm in height and more than 20 cm in width at the widest breadth of the fan. The sponge is light brown in colour, though the sponge holds a substantial amount of water which may drain after collection causing the sponge to appear lighter in colour. Many large, round, raised oscula up to 0.3 cm in diameter run along the fan and stalk. There is sometimes a large visible osculum on the distal portion of a lobe in situ, but this collapses after collection. The consistency is elastic and soft. The axial skeleton beneath the ectosome forms dense, stringy fibres which result in a sponge that is difficult to tear. The stalk is more or less cylindrical and flares out at the base to form roots. The periphery of the lobes appear slightly hispid, but remains soft to the touch. The interior of the fan or lobes is hollow, though the sponge is always flattened. Epibionts and mud are common on the lower stalk. Spicules and skeleton (Figure 3 D–E) The spicules are oxeas 245– 228 –326 x 15– 18 – 20 µm that are slightly bent. Some spicules may be thin, but these are less common and may represent developmental forms. The ends of the oxeas are sharply pointed near the distal portion, though in thinner spicules the point begins to taper closer to the centre. Stylote modifications and blunt ends are common. The skeleton is chalinid, a mostly anisotropic reticulation of multiple primary axial tracts of 2–3 spicules that run towards the surface in a slightly recurved, rib-like manner. The primary tracts are joined by single spicules forming a mostly square mesh. Primary tracts and nodes where single spicules join the primary skeleton are joined by spongin. There is no obvious ectosomal skeleton. Distribution and ecology Few specimens of Cladocroce spatula (Lundbeck, 1902) have been reported in the literature. The species is very common in the Gulf of St. Lawrence from 20–365 m while most specimens were collected above 100 m on shallow shelves in the southern Gulf of St. Lawrence. The species was observed during an ROV dive in the northern Laurentian Channel south of Anticosti Island. It was on soft sediment bottom attached to a rock. A single specimen was collected in the North Labrador Sea. A further record was identified from a preserved specimen ZMA.POR.20373 from Scotland (56.8066N, 7.4317W) by R.W.M. Van Soest in 2006. The species was also reported from Korshavn, Norway (NHMUK 1938.8.18.7). The type specimen (Lundbeck, 1902) was collected on the west Greenland Shelf, east of Cumberland Sound (65.2833N, 54.2833W). Remarks This is the first record of this species from the Gulf of St. Lawrence. Although the species is not often reported, it was the most common sponge collected during the 2018 CCGS Teleost survey in the southern Gulf of St. Lawrence. The specimens fit the description by Lundbeck (1902), except that spicules are slightly thicker. This species is most easily distinguished by the flabellate form with large oscula. The form described by Lundbeck was similar to some specimens collected in the Gulf of St. Lawrence (Fig. 3B), but other collected individuals grew into much larger elaborate fans or lobes (Fig. 3A,C). Cladocroce ventilabrum (Fristedt, 1887) was apparently collected along the Scotian Shelf near Muscongus Bay, but no museum specimens exist from those collections (OBIS, 2019). C. ventilabrum has slightly longer spicules that are 250 µm in length and the sponge itself is described as being ventilabriform. The specimens collected in the Gulf of St. Lawrence resemble the congeneric Cladocroce kiska Lehnert & Stone 2013 from the Aleutian Islands, but C. kiska has sigmas and longer oxeas. The consistency and arrangement of oscula in C. spatula is reminiscent of Haliclona (Haliclona) oculata (Linnaeus, 1759), although H. (H.) oculata forms many long finger-like extensions rather than the spatulate form of this species, and H. (H.) oculata has smaller spicules. Cladocroce spatula is often confused with Isodictya palmata (Ellis & Solander, 1786) in the Gulf of St. Lawrence due to the similar shape and presence of many large oscula, although I. palmata may grow much more pronounced, digitate branches. C. spatula differs from I. palmata in lacking chelae, but the oxeas of the two species overlap in size. It should be noted that the skeletal architecture of C. spatula is similar to that of I. palmata (Hajdu et al. 1994), even though the sponges are classified in different sponge orders. I. palmata was not identified from specimens collected from the Gulf of St. Lawrence in the survey year 2017–2018, but the species was collected in the North Labrador sea during the AQVIQ cruise. I. palmata specimens were much thicker than the predominantly flat C. spatula specimens, and the chelae are very distinct in spicule preparations. I. deichmannae (de Laubenfels 1949) was also collected from the Bay of Fundy, but that species has styles and chelae.

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