Clathria (Axosuberites) nidificata

Clathria (Axosuberites) nidificata (Kirkpatrick, 1907)

Figure 4

Material examined. Two specimens (MSNG N° 59506, MACN IN- 41004) collected at station 1 (54°29.07’ S; 62°10.76’ W) at 306 meters depth (labeled during the cruise as NBP 05/08 TB 1 #7). Collection date: April 2008. Collector: Laura Schejter.

Description. Specimens are more or less globular, with digitiform, cylindrical outgrowths and about 4 cm long (Figure 4 A). The base is constricted, probably to stay attached to the substrate. The living specimens were light brown, and got slightly red when dried. Spicules are two categories of styles and toxas. The styles I (Figure 4 B) are larger, straight, smooth and thick, 1175–(1273±88)– 1400 x 40–(45±7)–50 µm, while the other category, styles II (Figure 4 C), are straight, curved or sinuous, and thinner, 560–(679±120)– 1120 x 7.5–(19±10)–30 µm. Toxas are variable in length 130–(365±179)–670 x 10 µm, with prominent and narrow central curve; smaller toxas are entirely smooth (Figure 4 D), while larger ones have spinulated tips (Figure 4 E, F).

Distribution and habit. This species has been recorded from Antarctic waters and South Georgia Islands (Kirkpatrick,1908; Koltun 1964; Ríos et al. 2004). Burton (1940) also identified this species for Argentine waters off Mar del Plata and Miramar, from samples collected in 1925 and 1928; however, he did not provide images or measurements of the identified specimens. Since no other records were found in Argentina until present, this would be the third record of the species in Argentina, and also the first record for the Burdwood Bank area.

Remarks. Desqueyroux (1975), Koltun (1976) and Hooper (1996) considered this species to possess a high morphological variability, and synonymized Clathria (Axosuberites) nidificata (Kirkpatrick), C. (A.) flabellata (Topsent), and C. (A.) ramea (Koltun). Other authors (Ríos et al. 2004; Campos et al. 2007) considered that at least C. (A.) flabellata and C. (A.) nidificata were different taxa. Pansini et al. (1994) tested by means of a morphometric spicular analysis the “laminar” (flabellate) and the “ramose” (ramea) morphotypes, arriving at a significant difference, although they concluded that a genetic analysis was needed to confirm a specific separation of these morphs. Ríos (2007) again considered C. (A) flabellata and C. (A.) nidificata as different species based on their general morphology, spicule categories and sizes. Subsequently, Van Soest et al. (2016) listed the three taxa as separated (and valid) species. In this regard, considering the description provided, the re-analysis of the holotype made by Hooper (1996), in which the toxas with the spined tips were found (overlooked in the original description), and that the species was also recorded in Argentina, we assigned the specimens described here to C. (A.) nidificata. Compared to our specimens, the Antarctic ones described by Ríos (2007) are slightly different regarding the general morphology, despite the fact that our specimens are also smaller, and had smaller spicule sizes in general, with no spinulation in the toxas I. On the other hand, the Antarctic specimens described by Campos et al. (2007) as C. (A) nidificata presented a more similar morphology, having also spinulated toxas I and similar spicule sizes. In this case, however, styles of the Antarctic specimens reached bigger sizes than in Burdwood bank specimens. In this sense, C. (A.) nidificata apparently may show a wide variety of body morphologies and spicule sizes that could be related to different habitats found from its recorded distributional range.