Brachypopomus gauderio is not the only electric knifefish recently described from South America, U.S. researchers John P. Sullivan* and Carl D. Hopkins** have described another member of the genus Brachyhypopomus and given it the name Brachyhypopomus bullocki.

This new species is named in honour of Theodore Holmes Bullock, a renowned neurobiologist who died in 2005. Bullock was a pioneer of the comparative neurobiology of both invertebrates and vertebrates and is credited with the first physiological recordings from an electroreceptor and for championing electric fishes as a model system in neurobiology. The electric organ discharge waveform of Brachyhypopomus bullocki is biphasic, 0.9–1.6 milliseconds in duration, and the pulse rate varies from 20–80 Hz.

Brachyhypopomus bullocki is found throughout the Orinoco Basin in Venezuela and
Colombia. It can also be encountered in the in the Rio Branco drainage of Guyana and the Roraima State of Brazil, as well as in the upper part of Rio Negro near the mouth of Rio Branco.

Brachyhypopomus bullocki appears to prefer clear, shallow, standing water in open savannah, or savannah mixed with stands of Mauritia palm. It has also been collected among plants growing along the banks of small pools fed by streams. In Rio Negro, a specimen was found amongst palm leaf litter near the outlet of a black water stream.

Brachyhypopomus bullocki distinguishes itself from its close relatives by having larger eyes (comparative to the head), a short abdomen, and distally enlarged poorly ossified third and fourth branchiostegal rays.

The paper can be downloaded from Cornell University.

* John P. Sullivan, Department of Ichthyology, The Academy of Natural Sciences, Philadelphia. Email: sullivan@ansp.org

** Carl D. Hopkins, Department of Neurobiology and Behavior, Cornell University, New York. Email: cdh8@cornell.edu

The cichlid genus Crenicichla now has two new described members: Crenicichla tesay and Crenicichla mandelburgeri.

Crenicichla tesay

Crenicichla tesay lives in the Paraná River drainage and was described by Argentinian ichthyologists Jorge Casciotta and Adriana Almirón. The fish was caught in the Iguazú River upstream of Iguazú falls in Argentina, an environment characterized by falls and pools with clear and rapidly flowing water. The bottom in this habitat consists of stones, mud and sand.

The name Crenicichla tesay is derived from the Guaraní word for tears; the fish displays a tear-shaped suborbital stripe. You can distinguish Crenicichla tesay from its close relatives by the existence of a serrated posterior preopercle border, the number of scales on the E1 row, the length of the snout, and the colour pattern which consists of a suborbital stripe, 4–6 dark blotches and numerous irregularly scattered dots on the sides of the body.

The description has been published in the journal Revue Suisse de Zoologie[1]. For more information, see the paper: Casciotta, J and A Almirón (2008) Crenicichla tesay, a new species of cichlid (Perciformes: Labroidei) from the río Iguazú basin in Argentina. Revue Suisse de Zoologie 115, pp. 651–660.

Crenicichla mandelburgeri

Just like Crenicichla tesay, this newly described cichlid hails from the Paraná River drainage. It was described by Swedish ichthyologist Sven Kullander and named Crenicichla mandelburgeri in honour of Paraguayan ichthyologist Darío Mandelburger.

The Crenicichla mandelburgeri specimens were collected from two different environments. Some lived in the rapids of a large stream (5-10 meters wide and up to 1 meter deep) with turbid, brownish water. Others lived in a much smaller stream (up to 3 meters wide) with shallower brown water where both velocity and transparency fluctuated. In this environment, the bottom consisted of stones and sand and was generally without any plants.

Young Crenicichla mandelburgeri cichlids feature numerous narrow vertical bars along the side, which changes into an irregular dark horizontal band as the fish matures. You can also distinguish Crenicichla mandelburgeri from other crenicichlas by the distinct caudal blotch, the number of scales in the lateral row and in the E1 row, the lower jaw (which is longer than the upper), and the serrated preopercular margin.

For more information, see the paper: Kullander, SO (2009) Crenicichla mandelburgeri, a new species of cichlid fish (Teleostei: Cichlidae) from the Paraná river drainage in Paraguay. You can find it in Zootaxa 2006: 41–50.[2]

Crenicichla

Crenicichla is the cichlid genus where you can find the largest number of described species, about 75 species. They live on the South American continent where they inhabit freshwater rivers, streams, pools and lakes. The richest variation of species is encountered in the Amazon region, but you can find Crenicichla cichlids as far north as Guyana, Venezuela and Colombia and as far south as Uruguay and central Argentina where the water can become fairly cold in the winter.