Tuesday, August 27, 2013

[Ichthyology • 2013] Akawaio penak • a new genus and species of Neotropical electric fish (Gymnotiformes, Hypopomidae) endemic to the upper Mazaruni River in the Guiana Shield

Akawaio penak Maldonado-Ocampo, López-Fernández, Taphorn, Bernard, Crampton & Lovejoy 2013

Akawaio penak, a new genus and species, is described from the upper Mazaruni River, Guyana. The new species is diagnosed from all other species of Hypopomidae by several anatomical traits. The phylogenetic affinities of the new genus were inferred using data from one nuclear (rag2) and two mitochondrial (COI and cyt b) genes. The phylogenetic analyses indicate that Akawaio is the sister taxon of a clade that includes Brachyhypopomus, Hypopomus, Microsternarchus and Racenisia. These results provide evidence for the phylogenetic composition of Hypopomidae supported by previous molecular studies and support the position of the Steatogenini (Hypopygus + Steatogenys) as the sister group of Rhamphichthys + Gymnorhamphichthys. The description of this new electric knifefish increases the total number of endemic genera and species in the upper Mazaruni, a region that is suffering freshwater habitat degradation as consequence of gold-mining activities.

Akawaio gen. n
Akawaio penak sp. n. 

Holotype: CSBD 1654 (208 mm TL), Guyana, Zone 7, Kamarang, Mazaruni River.

Etymology: This genus is named in honour of the Akawaio Amerindians that populate the region of the upper Mazaruni and to recognize their valuable help while studying the fishes of their lands. To be regarded as a masculine noun. The species name is from the Akawaio name ‘penak’, which is apparently used unambiguously for this species. To be regarded as a masculine noun in apposition.

Ecological notes: Akawaio penak was captured both in the main channel and in tributaries of the upper Mazaruni River. Specimens from the Mazaruni River main channel and from Membaru Creek were captured at night on beaches resulting from artificial accumulation of sand and pebbles that are the by-product of gold-mining dredging. These individuals were captured at depths of no more than 1 m and were presumably feeding. In contrast, the Waruma River specimens were captured during the day in hiding places in the banks of a shallow backwater pool. Specimens in the main channel were exposed to slow current in a relatively calm but open beach without structure, whereas the Membaru and Waruma specimens were found in habitats with structure consisting of some submerged woody debris and vegetation. In all three localities where the species was found, the water was black to reddish black with pH ranging from 4.4 to 4.8, temperature of 22–23.5 °C and conductivity <10 μS.

Distribution: Akawaio penak is presently known only from the main channel of the upper Mazaruni River, the mouth of the Kamarang River and Waruma Creek: a small tributary of the Kako River, which in turn is a major tributary of the upper Mazaruni. This disjunct distribution suggests that A. penak has a broader distribution within the upper Mazaruni drainage, but further collections are necessary to ascertain how widespread the species is.

Javier A. Maldonado-Ocampo, Hernán López-Fernández, Donald C. Taphorn, Calvin R. Bernard, William G. R. Crampton and Nathan R. Lovejoy. 2013. Akawaio penak, a new genus and species of Neotropical electric fish (Gymnotiformes, Hypopomidae) endemic to the upper Mazaruni River in the Guiana Shield. Zoologica Scripta. DOI: dx.doi.org/10.1111/zsc.12035