Livebearing fish genus revised


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The poeciliid livebearer genus Phalloptychus has been revised and the number of valid species has been raised to three.

Brazilian ichthyologist Paulo Lucinda of the Laboratorio de Ictiologia Sistematica, at the Universidade Federal do Tocantins, undertook a study of the poeciliine fishes and has just reported his findings in the Sociedade Brasileira de Ictiologia journal, Neotropical Ichthyology.

Prior to the study, the general opinion was that the genus held just two species: Phalloptychus eigenmanni and P. januarius, which are small molly-like livebearers.

However, Lucinda's work has revealed that P. iheringii, which was previously considered a synonym of P. januarius, is actually a species in its own right and he's elevated the fish to specific status once again.

Lucinda found that the two fish have slightly different morphology and a totally different colour pattern.

He says: "Phalloptychus iheringii and P. januarius can be distinguished by the number of epipleural ribs, number of gonopodial rays, and a significantly different number of vertical bars along body side in females."

Each of the three species has been redescribed to take the new evidence into account and Lucinda has produced a new key to help other scientists identify which species they are looking at.

Lucinda says that ichthyological studies of the Phalloptychus genus are extremely rare, and consist almost entirely of the original species descriptions, so very little is known about the biology of the fishes.

For more details on the genus see the paper: Lucinda, PHF (2005) - Systematics and biogeography of the genus Phalloptychus Eigenmann, 1907

(Cyprinodontiformes: Poeciliidae: Poeciliinae). Neotropical Ichthyology, 3(3):373-382, 2005.