Fissurella itapema ( Ihering, 1927 )

Simone, Luiz Ricardo L., 2024, New species, misidentifications and problematic taxonomy of some Atlantic South American marine mollusks: a review, Papéis Avulsos de Zoologia 64, pp. 1-104 : 6-8

Fissurella itapema ( Ihering, 1927) revalidated, new combination ( Fig. 4 A-G)

Lucapina itapema Ihering, 1927: 102-103 (pl. 6, fig. 5-8); Rios, 1970: 20, 1975: 18, 1985: 17, 1994: 27, 2009: 35 (these in syn of F.rosea ).

Fissurella (Cremides) clenchi Farfante, 1943: 11-12 (pl. 3, figs. 8-11) (new synonym); Métivier, 1970: 119, 1972: 406; Abbott, 1974: 28; Rios, 1975: 18 (pl. 4, fig. 34), 1985: 16 (pl. 8, fig. 63), 1994: 26 (pl. 7, fig. 61), 2009: 34 (fig. 70).

Lucapinella itapema : Morretes, 1949: 56.

Fissurella chenchi : Rios, 1970: 20 (pl. 2); Vermeij & Porter, 1971: 445, 447, 451; Calvo, 1987: 53 (fig. 17); Simone, 2008: 292, 303 MolluscaBase, 2023.

Fissurella rosea : Righi, 1963: 263-264; Rios, 1970: 20 (pl. 2), 1975: 18 (pl. 4, fig. 36), 1985: 16-17 (pl. 8, fig. 65), 1994: 27 (pl. 7, fig. 63), 2009: 35 (fig. 72); Métivier, 1972: 406 (part); Calvo, 1987: 53, 57 (fig. 19); Leal, 1991: 34-35 (part); Longo et al., 2014: 3, 8 (fig. 2N) (non Gmelin, 1789).

Types: F. itapema : holotype Senckenberg Mus. 3278 ( Fig. 4 A-C); F.clenchi : MCZ 124730 ( Fig. 4 D-G) .

Type localities: Itapema , Santa Catarina, Brasilien (in holotype label) ; F. clenchi : Nova Almeida [−20.056568° −40.196843° (Datum: WGS84 )], Espirito Santo, Brazil .

Remarks: In the time of description of Fissurella mesoatlantica Simone, 2008 , endemic from São Pedro e São Paulo Archipelago, a remote Brazilian oceanic island, a comparison with coastal congener samples was performed, a study ( Simone, 2008) that remains largely unpublished. It was observed that the entire Brazilian coast bear a single species of Fissurella , occurring intertidally. Some shells with a red tone were identified as F. rosea , while others as F. clenchi . This identification was mostly induced by some references (e.g., Rios, 1994, 2009), showing the color and details of the orifice as key characters. However, the Brazilian Fissurella species exhibit significant variability in shell features, including color and in orifice aspects; more trustable are the anatomical characteristics ( Simone, 2008). These characteristics were primarily employed to distinguish the insular species. Fissurella rosea actually is a valid species, but does not occur in Brazil. It is a Caribbean species, with shell larger and much more sculptured, with scales and nodes more developed than the Brazilian population ( Farfante, 1943).The southmost range of F.rosea appears to be Venezuela. Fissurella clenchi , on the other hand, seems to be endemic from Brazil, with confirmed north limit in Ceará and extending up to Rio Grande do Sul.Due to confusion with F. rosea in the southern Caribbean, the distinction between both species remains unclear, as some reports in French Guyana are documented ( Farfante, 1943).

Lucapina itapema , formerly, was so far considered a synonym of F. rosea . The species was described based on a broken shell, in which the tip of it was amputated ( Fig. 4 A-C). Consequently, the shell took on the appearance of having a very wide orifice, simulating genera with this characteristic. This led to its first classification in Lucapina Gray in Sowerby, 1835 ( Ihering, 1927) and a combination to Lucapinella Pilsbry, 1890 ( Morretes,1949) (in fact these genera do not have such large orifice, a more accurate classification would be Fissurellidea d′Orbigny, 1839 ).As L.itapema already sets up on F.rosea synonymy (see synonymic list above) the generic mistake and the shell breakage were noted by previous authors.

Despite Ihering (1927) not reporting a type locality in the original description of L. itapema , the specific epithet, the justifications of other species described with this same name in that paper, and the information of the holotype′s label, leave no doubt that the type locality is Itapema, a city of the coast of Santa Catarina, Brazil (~ 27°05′S 48°36′W). This locality is significantly distant from the true geographic distribution of F. rosea in the Caribbean. Conversely, L. itapema is, in fact, synonym of F.clenchi . However, as that name was described 16 years earlier, it takes precedence and must be considered valid. Despite being more comprehensively described, possessing complete types ( Fig. 4 D-G), and being more widely utilized, F. clenchi must be considered a synonym.

There is a prevailing belief among collectors and local taxonomists, as explained above, that, in Brazilian Fissurella , the reddish toned shells belong to F. rosea , while those with brownish are F. clenchi . Looking inside, the Brazilian Fissurella usually have a colorful halo surrounding the orifice. Sometimes it is red, thus implicating it is a presumed F. rosea , sometimes it is blue, thus implicating a F. clenchi . There are, however, a myriad of other variations, including brown, both (red and blue) and even absence (white – Fig. 4F ). This demonstrates that the color is not a good taxonomical parameter for this group. Most possibly, the red tone was the responsible for considering L. itapema a F. rosea synonym. Observing both holotypes ( L. itapema in Fig. 4 A-C and F. clenchi in Fig. 4 D-G), it is evident that they belong to the same species, as the sculpture and color pattern are similar, and they differ from any other regional species. The orifice conformation, highlighted by some authors as a distinguishing feature between F.rosea and F.clenchi (e.g., Farfante, 1943), is also variable in the local Fissurella . This variation results from the gradual reabsorption of the shell tip during growth, a process described by Simone (2008) and references therein, and it is not uniform. The edges can vary, e.g., the holotype itself, has the outer edge trilobed ( Fig. 4D, G ), but it is elliptic inside ( Fig. 4F ).

Figures

Figure4.Fissurellaitapemashelloftypes:(A-C)holotypeSenckenbergMus.3278(L13.3mm),dorsal,ventral andleftviews(CourtesySenckenbergMuseum);(D-G)holotype Fissurella clenchi, MCZ 124730 (courtesy MCZ); (D) dorsal view; (E) left view; (F) ventral view; (G) detail of apex,dorsal view, scale: = 1 mm; (H-K) Cranopsis watsoni shellof lectotype USNM95146 inSEM (L 3.1 mm) (courtesy USNM);(H) right view;(I) dorsal view;(J) left view;(K) detail of apex,right view,scale:= 200µm.