A review of the Pachypanchax killifish of Madagascar has seen the description of four new species and the redescription of two others.
The study by Paul Loiselle of the New York Aquarium sees Pachypanchax omalonotus and P. sakaramyi joined by four new species, which have been named P. varatraza, P. patriciae, P. sparksorum and P. arnoulti.
Loiselle's paper, which has just been published in the systematics journal Zootaxa, looks at the history of the Malagasy Pachypanchax and their diagnostic characters.
It says that five characteristics, four skeletal and one based on the scales, unambiguously place all but one of Madagascar's aplocheilid killifish in the genus Pachypanchax.
The oddball of the group, Pachypanchax nuchimaculata, is only tentatively placed in the genus. This fish is known from just a single specimen and displays several peculiar features which don't fit correctly within the confines of Pachypanchax, says Loiselle.
New PachypanchaxPachypanchax varatraza was discovered in a number of small creeks in the Ampanobe, Menambery and Fanambama drainages. The species, which is described as "robust", reaches 8cm/3" and exists in a pale green morph in the Menambery drainage and a red morph in the Ampanobe drainage.
Introduced Channa maculata have already wiped out Pachypanchax varatraza in the lower reaches of the Menambery, Fanamabana and Ampanobe drainages.
Following the World Conservation Union criteria, Loiselle classified the species as one of special concern, with a status that needs to be monitored on a regular basis.
Pachypanchax patriciae, which is named after fish conservationist Patricia Yagzi, is characterised by male colour polymorphism and exists in red and blue morphs. The species was discovered in the Ampandra River, an oxbow lake of the Ifasy River and in a creek attached to the Mahavavy du Nord River. It is believed to be vulnerable according to World Conservation Union criteria.
Pachypanchax sparksorum, which is named after John Sparks and Karen Riseng Sparks who collected much of the type series, was found in the Ankofia drainage. Males are a deep red colour with a black edge to the anal fin. It has been classified as endangered using World Conservation Union criteria.
Pachypanchax arnoulti occurs in the Betsiboka, Boinakely and Andranomavo drainages and is named in honour of Jacques Arnoult. It is relatively drab in comparison to the other species, being predominantly coppery with metallic scales. Most reports since 1950 that refer to Pachypanchax omalonotus actually refer to arnoulti.
It is found over a wide area and its conservation status varies. Loiselle says that the fish is classified as a species of special concern.
Loiselle says that a further three Malagasy species have been discovered recently and are awaiting description.
For more details see the paper: Loiselle PV (2006) - A new of the Malagasy Pachypanchax (Teleostei: Cyprinodontiformes, Aplocheilidae) with descriptions of four new species. Zootaxa 1366: 1-44.