Eunapius fragilis (Leidy, 1851)

(Figure 8)

Spongilla fragilis Leidy, 1851: 278; Potts 1887: 197.

Spongilla (Eunapius) fragilis, Bonetto & Ezcurra de Drago 1967a: 332, Ezcurra de Drago 1974b: 249. For other synonyms, see Muricy et al. (2011).

Material studied. UFPEPOR972, 973, 974, coll. G. Nicacio, 12.xii.2009, UFPEPOR1344, 1345, coll. U Pinheiro, 23.v.2012, Pirangi River, Jaqueira, Pernambuco, Brazil, 08°44'53,0"S 35°48'51,1"W. UFPEPOR1133, 1134, São Francisco River (III), Petrolândia, Brazil, 09°08'37.1"S 38°17'48.9"W, coll. E. L. R. Lima, 19.v.2010.

General morphology. Encrusting sponge measuring 20cm in diameter and 5mm thickness (Fig. 8 a). Consistency of live sponge moderately soft, spongin abundant. Colour white, green or grey. Spicules. Megascleres oxeas (195–291/9–18µm), smooth, fusiform, straight or slightly curved (Fig. 8 b). Microscleres absent. Gemmuloscleres stout spined oxeas (90–138/6–9µm), almost straight, sharp tips (Fig. 8 c). Gemmules irregular hemispherical shaped averaging 450µm in diameter, single or grouped, scattered in the sponge body. Gemmuloscleres tangentially embedded and pneumatic layer thick with regular lines of polygonal chambers trabeculae-like of compact spongin (Fig. 8 d,e).

Distribution and ecological notes. Brazil (Muricy et al. 2011); Cosmopolitan (Manconi & Pronzato 2008). Specimens were found on rocky substrate in shallow running waters.

So far records of Eunapius fragilis indicate that this species is the most cosmopolitan spongillid species, and furthermore the most widely distributed throughout all regions. However, there are issues on the systematics and biogeographical distribution of this species, since most records suggest an existence of a species-complex. Potts (1887) redescribed this species and emended its diagnosis, providing additional morphotraits to help with species’ identifications, but there is still a paucity of morphological characters to unequivocally identify E. fragilis. This difficulty is further confused whereby most records describe this species with two types of gemmuloscleres (oxeas and strongyles), but many other records describe specimens with only one type. This may be the main problematic point about the taxonomy of E. fragilis, which can lead to misinterpretation of its alleged cosmopolitanism.

Remarks. Penney & Racek (1968) made an extensive revision with E. fragilis specimens from many regions worldwide, except from South America. The authors aimed to elucidate some issues about systematics and distribution of this species. They also synonymized many records previously assigned to this species and reallocated them to other genera. Although that work recognizes remarkable morphological divergences, it was not possible to describe new species from these specimens, but authors were aware of the variability as trends of speciation in disjunct populations, and endorsed the need to review some new material to clarify the specific status of this species. Moreover, records of Neotropical E. fragilis require attention and revision, because most lack any suitable morphological descriptions or illustrations (Ezcurra de Drago 1974b, Volkmer-Ribeiro et al. 1975, Volkmer-Ribeiro 1981, Volkmer-Ribeiro & Grosser 1981, De Rosa Barbosa 1984, Ezcurra de Drago 1993, Batista & Volkmer-Ribeiro 2002).