Schellencandona cf. insueta (Klie, 1938)

Schellencandona cf. insueta

( Figure 4 View FIGURE 4 )

A single adult female specimen (MZUF730) of the genus Schellencandona was found in a sample collected on 3 July 2018 (MCB coll.) from the interstitial zone of the Po River, near the locality of Martiniana Po (Cuneo, Italy; latitude 44°39′16” N, longitude 7°19′27” E, 351 m a.s.l.). The specimen’s left valve was severely damaged prior to dissection, making it unsuitable for the taxonomic description. RV ( Figures 1H–J View FIGURE 1 ) with straight dorsal margin slightly tapering towards posterior end. Evenly rounded anterior margin distinctly broader than posterior one, the latter gently tapering towards ventral corner. Surface covered by reticulate pattern organized in polygonal meshes, with weakly calcified muri and smooth fossae. The specimen shows notable similarity to Schellencandona insueta (Klie 1938) (see Figure 11, page 13 in Klie 1938a). The valves are also very similar in size (L= 0.47 mm and 0.46 mm, H/L 0.51 and 0.52 in the specimen studied here and in S. insueta , respectively). In Klie (1938a, 1938b), the valves of S. insueta are described as smooth and hairy, but no mention is made of a reticulate pattern, which is instead evident in the specimen from the Po River also when observed in transmitted light.

Regarding the soft parts of the female of S. insueta, Klie (1938a) only published drawings of the cleaning leg and the furcal ramus. In the specimen examined here, the ratio between seta h1 and seta g of the cleaning leg is approximately 2:1 ( Figure 4A View FIGURE 4 ), whereas in S. insueta the two setae are of similar lengths ( Klie 1938a; Figure 15, page 14). Particularly interesting is the presence in the Po River specimen of two denticles and two rows of setulae on each of the two terminal claws of the furcal ramus ( Figure 4B View FIGURE 4 ), similar to what is illustrated by Klie (1938a; Figure 16, page 14) for S. insueta . Notably, this feature is not detectable in any other known species of the genus Schellencandona .

The studied specimen contained bundles of sperm inside the carapace, indicating the presence of males at the sampling site.

Since only one specimen from the Po River was available and its preservation was insufficient, along with the lack of highly diagnostic male sexual characteristics, it seems advisable to refrain from fully confirming its specific status at this stage, despite the observed similarities to S. insueta . A more definitive verification will require the potential acquisition of additional material .