Leptinaria unilamellata (d’Orbigny, 1838)

Leptinaria unilamellata (d’Orbigny, 1838) View in CoL

( Figures 3 (D–G), 13)

Records in PNM da Cidade sta. 3, 5 April 2022 [2 spm, MNRJ 23834 View Materials ]; sta . 3, 5 May 2022 [2 spm, MNRJ 22771 View Materials ]; sta . 3, 10 September 2022 [1 sh]; sta. 5, 17 September 2023 [1 sh, MNRJ 36402 View Materials ]; sta . 14, 17 September 2023 [1 spm, MNRJ 61527 View Materials ]; sta . 14, 2 July 2024 [1 spm, MNRJ 61770 View Materials ] .

Description of radula (MNRJ 23834)

Formula 20 + 13 + 1 + 13 + 20; central tooth with a rectangular basal shaft and distal portion cordiform, much reduced, reaching 8 µm long; inner lateral teeth with a rectangular/squared basal shaft and distal portion with a wide basal plate, a major cusp 1 and a minor cusp 2, with L1 and L2 sometimes with a third, near obsolete cusp in its innermost portion; the pointed cusps of inner lateral teeth (especially L1) gradually become longer and lanceolate (achieving their acme in L7/L8), but outer lateral teeth have a reduced cusp 1, gradually assuming a nearly rectangular shape; L1 up to 24 µm long, 16 µm wide, L7/L8 up to 32 µm long, 10 µm wide, L13 up to 21 µm long, 6 µm wide; marginal teeth without discernible cusps (despite some irregularities at the distal border in inner teeth), gradually progressing from rectangular in M1 to square or trapezoidal, short, in outer teeth; M1 up to 19 µm long, 6 µm wide, M20 up to 9 µm long.

Description of radula (MNRJ 61527)

Formula 15 + 13 + 1 + 13 + 15; central tooth with a rectangular basal shaft and distal portion cordiform, much reduced, reaching 9 µm long; inner lateral teeth with a rectangular/squared basal shaft and distal portion with a wide basal plate, a major cusp 1 and a minor cusp 2, with L1 and L2 sometimes with a third, near obsolete cusp in its innermost portion; the pointed cusps of inner lateral teeth (especially L1) gradually become longer and lanceolate (achieving their acme in L7/L8), but outer lateral teeth have a reduced cusp 1, gradually assuming a nearly rectangular shape; L1 up to 21 µm long, 15 µm wide, L7/L8 up to 28 µm long, 10 µm wide, L13 up to 22 µm long, 8 µm wide; marginal teeth without main cusps but with many (up to 10–12) minute, often united, thread-like irregularities at the distal border (mainly in the outer teeth), teeth gradually progress from sub-rectangular in M1 to brush-like in outer teeth; M1 up to 19 µm long, 7 µm wide, M15 up to 13 µm long.

Remarks

This is an ovoviviparous species ( Carvalho et al. 2009), and one adult (10 mm long) had seven embryos in the uterus ( Figure 3 (E)), reaching up to 0.9 mm long. The number of embryos per adult is similar to those recorded by Dutra (1988) – up to eight embryos – and Carvalho et al. (2009), with a mean of 6.7 embryos (but up to 11 or more embryos).

Araújo and Keller (1993) studied some anatomical features of L. unilamellata , but not its radula. After a bibliographic search comprising this name and its most cited synonym, Leptinaria lamellata (Potiez and Michaud, 1838) , the single description of a radula on this widespread species seems to be by Fischer and Crosse (1894) – and reproduced by Pilsbry (1906) – showing many similarities to the radulae illustrated here ( Figure 13). Despite the gradual morphological transition from innermost lateral teeth to outer marginal teeth, we opted to define lateral teeth as those having one or two (asymmetrical) pointed cusps, and marginal teeth as those without main cusps.

Prior to this study, a single COI sequence of this species was available at GenBank, belonging to a specimen identified as L. lamellata (synonym of L. unillamelata ) by Fontanilla et al. (2017), from the Botanical Garden of Rio de Janeiro (specimen not illustrated). Despite nearly identical shells ( Figure 3 (D,F,G)) and radulae ( Figure 13), one of the two specimens sequenced in the present study matched 100% with the specimen from the Botanical Garden, whereas the other specimen had a great COI divergence (p-distance: 9.5%, for 650 nt) ( Table 2 View Table 2 ). Apparently, the widespread L. unillamelata is currently composed of a species complex, demanding further studies in order to precisely define the geographic boundaries of each lineage.

Geographic distribution Widespread in Central/South America ( Simone 2006), including Brazil ( Araújo and Keller 1993; Simone 2006) and the city of Rio de Janeiro (eg Alexandre et al. 2017; Rangel et al. 2021). It has been introduced in French Polynesia and Europe ( Lima et al. 2021).