A new species of Microcancilla from the southwestern Atlantic and notes on Microcancilla brasiliensis comb. nov. (Gastropoda, Cancellariidae)

Abstract Microcancilla phoenix sp. nov., collected from the Southeast and South coast of Brazil represents the southernmost record of the genus in the Atlantic Ocean. The new species differs from the other congeners of the Atlantic mainly by the presence of microscopic pustules covering the whole shell and by dimensions of the protoconch. Axelella brasiliensis Verhecken, 1991, known from the Northeast to South coast of Brazil, is transferred to Microcancilla based on a similar sculpture of microscopic pustules on the protoconch and on other features of the teleoconch discussed in the present study.

A new species of Microcancilla from the southwestern Atlantic and notes on Microcancilla brasiliensis comb. nov. (Gastropoda, Cancellariidae)

Abstract Microcancilla phoenix sp. nov., collected from the Southeast and South coast of Brazil represents the southernmost record of the genus in the Atlantic Ocean. The new species differs from the other congeners of the Atlantic mainly by the presence of microscopic pustules covering the whole shell and by dimensions of the protoconch. "Axelella brasiliensis" Verhecken, 1991, known from the Northeast to South coast of Brazil, is transferred to Microcancilla based on a similar sculpture of microscopic pustules on the protoconch and on other features of the teleoconch discussed in the present study.

A new species of Microcancilla from the southwestern Atlantic and notes on Microcancilla brasiliensis comb. nov. (Gastropoda, Cancellariidae)

Microcancilla phoenixsp. nov., collected from the Southeast and South coast of Brazil represents the southernmost record of the genus in the Atlantic Ocean. The new species differs from the other congeners of the Atlantic mainly by the presence of microscopic pustules covering the whole shell and by dimensions of the protoconch. “Axelella brasiliensis” Verhecken, 1991, known from the Northeast to South coast of Brazil, is transferred to Microcancilla based on a similar sculpture of microscopic pustules on the protoconch and on other features of the teleoconch discussed in the present study.(AU)

Shell morphology of the freshwater snail Gundlachia ticaga (Gastropoda: Ancylidae) from four sites in Ilha Grande, southeastern Brazil

The freshwater snail Gundlachia ticaga (Marcus & Marcus, 1962) is widely distributed in Brazil, but its morphology has been poorly studied. We compared the shell morphology of samples from four sites (Vila do Abraão, Vila de Provetá, Parnaioca and Praia do Sul) in Ilha Grande (Angra dos Reis, state of Rio de Janeiro) in order to evaluate differences within and among four populations. We used nine morphometric characters representing shell size and shape. To analyze shell morphology we considered aperture shape, sculpture of teleoconch, apex carving and position. The resulting dataset was correlated by Pearson´s linear correlation and shell differences among populations were tested using ANOVA and Discriminant Function Analysis. The results showed that there is significant variation among populations concerning shell shape and morphology. Shells from preserved localities (Praia do Sul and Parnaioca) and shells from highly modified environments (Vila do Abraão and Vila de Provetá) were the most similar to each other. Results from the visual assessment and from the discriminant analysis were almost identical. The shell indices are the most important variables in the differentiation of samples. The observed variation corroborates the hypothesis that G. ticaga displays phenotypic plasticity, which may lead to wrong identifications. Narrower shells with an elongate aperture could be misidentified as Ferrissia Walker, 1903 and, broader shells with a roundish aperture could be wrongly identified as Burnupia Walker, 1912. We confirmed that the absence of radial lines is not a good diagnostic character for G. ticaga. The analysis of the apical micro-sculpture and soft parts is essential for a correct identification.

Shell morphology of the freshwater snail Gundlachia ticaga (Gastropoda: Ancylidae) from four sites in Ilha Grande, southeastern Brazil

The freshwater snail Gundlachia ticaga (Marcus & Marcus, 1962) is widely distributed in Brazil, but its morphology has been poorly studied. We compared the shell morphology of samples from four sites (Vila do Abraão, Vila de Provetá, Parnaioca and Praia do Sul) in Ilha Grande (Angra dos Reis, state of Rio de Janeiro) in order to evaluate differences within and among four populations. We used nine morphometric characters representing shell size and shape. To analyze shell morphology we considered aperture shape, sculpture of teleoconch, apex carving and position. The resulting dataset was correlated by Pearson´s linear correlation and shell differences among populations were tested using ANOVA and Discriminant Function Analysis. The results showed that there is significant variation among populations concerning shell shape and morphology. Shells from preserved localities (Praia do Sul and Parnaioca) and shells from highly modified environments (Vila do Abraão and Vila de Provetá) were the most similar to each other. Results from the visual assessment and from the discriminant analysis were almost identical. The shell indices are the most important variables in the differentiation of samples. The observed variation corroborates the hypothesis that G. ticaga displays phenotypic plasticity, which may lead to wrong identifications. Narrower shells with an elongate aperture could be misidentified as Ferrissia Walker, 1903 and, broader shells with a roundish aperture could be wrongly identified as Burnupia Walker, 1912. We confirmed that the absence of radial lines is not a good diagnostic character for G. ticaga. The analysis of the apical micro-sculpture and soft parts is essential for a correct identification.

Shell morphology of the freshwater snail Gundlachia ticaga (Gastropoda: Ancylidae) from four sites in Ilha Grande, southeastern Brazil

The freshwater snail Gundlachia ticaga (Marcus & Marcus, 1962) is widely distributed in Brazil, but its morphology has been poorly studied. We compared the shell morphology of samples from four sites (Vila do Abraão, Vila de Provetá, Parnaioca and Praia do Sul) in Ilha Grande (Angra dos Reis, state of Rio de Janeiro) in order to evaluate differences within and among four populations. We used nine morphometric characters representing shell size and shape. To analyze shell morphology we considered aperture shape, sculpture of teleoconch, apex carving and position. The resulting dataset was correlated by Pearson´s linear correlation and shell differences among populations were tested using ANOVA and Discriminant Function Analysis. The results showed that there is significant variation among populations concerning shell shape and morphology. Shells from preserved localities (Praia do Sul and Parnaioca) and shells from highly modified environments (Vila do Abraão and Vila de Provetá) were the most similar to each other. Results from the visual assessment and from the discriminant analysis were almost identical. The shell indices are the most important variables in the differentiation of samples. The observed variation corroborates the hypothesis that G. ticaga displays phenotypic plasticity, which may lead to wrong identifications. Narrower shells with an elongate aperture could be misidentified as Ferrissia Walker, 1903 and, broader shells with a roundish aperture could be wrongly identified as Burnupia Walker, 1912. We confirmed that the absence of radial lines is not a good diagnostic character for G. ticaga. The analysis of the apical micro-sculpture and soft parts is essential for a correct identification.

Morphology of the larval shell of three oyster species of the genus Crassostrea Sacco, 1897 (Bivalvia: Ostreidae) / Morfologia de conchas larvais de três espécies de ostras do gênero Crassostrea Sacco, 1897 (Bivalvia: Ostreidae)

In this study we describe the morphology of the larval shell of three oyster species of Crassostrea genus. Two species, C. rhizophorae and C. brasiliana, are native to the Brazilian coast, and C. gigas is an introduced species. Samples of laboratory reared larvae, obtained through artificial fertilisation, were collected at intervals during the cultivation process for analysis using Scanning Electron Microscopy (SEM). Prodissoconch morphology was observed in relation to the presence, position, form and number of teeth in the three larval stages: D-shaped larva, umbo larva and pediveliger. Characteristic of D-shaped larvae of C. rhizophorae was the total absence of teeth in the provinculum area while C. brasiliana and C. gigas had two anterior and two posterior teeth in each valve. In the umbo larval phase, the three species had the same number of teeth in each valve: two posterior and two anterior teeth in the right valve and three posterior and three anterior in the left valve. In the pediveliger stage the three species could be differentiated by the number of anterior teeth of the right valve: C. rhizophorae had two teeth, C. brasiliana one tooth and C. gigas three teeth.(AU)

Neste estudo, foi descrita a morfologia das conchas larvais de três espécies de ostras do gênero Crassostrea. Duas espécies, C. rhizophorae e C. brasiliana, são nativas da costa brasileira e C. gigas é uma espécie introduzida. Amostras de larvas produzidas em laboratório através de fertilização artificial foram coletadas em intervalos durante o processo de cultivo para análises dos número de dentes nos três estágios larvais: larva D, umbo e pediveliger. As larvas D de C. rhizophorae caracterizaram-se pela total ausência de dentes na área do provinculum, enquanto C. brasiliana e C. gigas apresentaram dois dentes anteriores e dois posteriores em cada valva. Na fase umbo, as três espécies apresentaram o mesmo número de dentes em cada valva: dois dentes anteriores e dois posteriores na valva direita; e três dentes posteriores e três anteriores na valva esquerda. Na fase pediveliger, as três espécies se diferenciaram pelo número de dentes anteriores na valva direita: C. rhizophorae apresentou dois dentes; C. brasiliana, um dente; e C. gigas, três dentes.(AU)