Strobiligera, Dall, 1924

Fernandes, Maurício Romulo & Pimenta, Alexandre Dias, 2019, Taxonomic review of Inella and Strobiligera (Gastropoda: Triphoridae) from Brazil, Zootaxa 4613 (1), pp. 1-52 : 46-48

Strobiligera sp.

Figure 27

Material examined. Brazil: off Rio de Janeiro state: MNRJ 26140 , REVIZEE-Sul sta. 6753 [approximately 100 larvae and post-larvae and two pieces of biogenic substrata] .

Remarks. An egg laying of a Strobiligera species was sampled by the Expedition ‘REVIZEE-Sulʹ in southeast- ern Brazil. This spawn includes nearly 100 larvae and post-larvae associated with two fragments of hard biogenic substrata ( Fig. 27 ). The major fragment measures 18.3 mm in length and is mainly dominated by an encrusted sponge. The minor fragment measures 5.6 mm x 3.2 mm and is composed of a bryozoan colony partly covered by encrusted sponges, especially on its underside.

A few post-larvae were still associated with the substrata when photographed ( Fig. 27 C–D, F), but the majority were detached and many exhibited distinct spicules adhering to the shell, indicating a moderately loose attachment (i.e., post-larvae were not embedded in the sponge). The light brown protoconch has usually 2.5 whorls, and the white teleoconch reaches one complete whorl. The protoconch is 0.61–0.70 mm long, 0.42–0.48 mm wide on the first, smooth and inflated whorl, 0.51–0.56 mm wide on the last whorl. Two smooth spiral cords are present on the last protoconch whorl, the adapical one situated at 41–44% of whorl height, the abapical one at 68–79%; minute axial marks are present below the suture. The spiral cords of protoconch originate the nodulose median and abapical cords of teleoconch, with the adapical cord of teleoconch emerging immediately after metamorphosis.

The most probable identity of this spawn is Strobiligera campista sp. nov., because of protoconch color, similar dimensions and positioning of spiral cords at the larval shell, in addition to being a moderately common species in the lower continental shelf of the sampled locality. The present findings shed light on the larval development of the genus, in this case not a lecithotrophic development with a short demersal stage, but a probable example of intracapsular metamorphosis, which suggests a restricted geographical range of this species. The egg laying in sponges is similar to previous observations in Cerithiopsidae ( Nützel 1998; Collin 2004) and Newtoniellidae ( Schiaparelli et al. 2003) , constituting the second observed spawning of a Triphoridae species, after Pelseneer (1926): he described the spawning of a species related to the “ Triphora perversa ” complex ( Bouchet & Guillemot 1978) in a bivalve shell from France.

Figures

FIGURE 27. Spawn of Strobiligera sp., MNRJ 26140. A–F. Biogenic substrata; white arrows in figures C–D, F indicate postlarvae adhered to the substrata. G–L. Post-larvae. Scale bars: A, 10 mm; B–F, 1 mm; G–L, 500 µm.