New doradid placed in new genus

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Scientists have placed a newly discovered doradid catfish from Brazil in a genus of its own.

Horacio Higuchi, Jose Birindelli, Leandro Sousa and Heraldo Britski named the new species Merodoras nheco in a paper in the systematics journal Zootaxa.

The species appears to be small, with all specimens examined measuring just 23-54mm in length.

The genus is believed to be a close relative of Amblydoras, with which it shares a number of morphological features.

The authors wrote: "Merodoras nheco, new species, is distinguished from other doradids by the unique combination of the following characteristics: 1) tips of retrorse spines on the midlateral scutes ventrally oriented in adults; 2) incomplete lateral line, with only a few midlateral scutes anteriorly; 3) pectoral girdle entirely exposed ventrally, with the opening of the arrector ventralis inferior reduced to a small fossae on the anterior edge of the coracoid; 4) caudal fin truncate; 5) dorsal-fin spine smooth, without serrae on both faces; 5) lacrimal serrated; 6) lateral ethmoid serrated."

AstrodoradinaeThe authors also placed Merodoras nheco in a newly erected subfamily called the Astrodoradinae, which includes Amblydoras, Anadoras, Astrodoras, Merodoras, Hypodoras, Physopyxis and Scorpiodoras.

The subfamily is diagnosed by a number of features, including the presence of simple barbels, the lack of a nuchal foramina and an abbreviated cordiform shape to the swimbladder.

Available nameThe new species was discovered by Heraldo Britski during his studies of the Pantanal region of western Brazil, where it lives in the flooded Pantanal Matogrossense area.

During his PhD in 1992, Horacio Higuchi applied the name Merodoras nheco to Britski's find.

However, the name couldn't be formally recognised, as the work was not published, so although it was used in subsequent papers by other experts on the Doradidae it remained unavailable.

This formal description sees the name become available for formal use in the literature.

The species name nheco refers to the town of Nhecolandia, where the fish was discovered.

Reptile parasitesMost specimens of Merodoras nheco were found to be carrying pentastomid parasites in their swimbladders, where they live between the inner walls and internal structures called pleura.

The parasites eventually go on to infect reptiles, so the fish are believed only to be an intermediate host.

The authors believe that Southern caiman crocodiles, Caiman crocodilus yacare feed on the catfish when they still lakes they inhabit dry up in the winter, making the prey easy to capture.

For more information see the paper: Higuchi H, Birindelli JLO, Sousa LM, Britski HA (2007) - Merodoras nheco, new genus and species from Rio Paraguay basin, Brazil (Siluriformes, Doradidae), and nomination of the new subfamily Astrodoradinae. Zootaxa 1446: 31-42 (2007).