Volume 13, Issue 2, 08 November 2007
Volume 13, Issue 2 – 08 November 2007
Flávio C. T. Lima, Heraldo A. Britski and Francisco A. Machado: A new Moenkhausia (Characiformes: Characidae) from central Brazil, with comments on the area relationship between the upper rio Tapajós and upper rio Paraguai systems, pp. 45-54
A new species of Moenkhausia is described from the rio Juba, tributary of the rio Sepotuba (upper rio Paraguai basin), the rio Juruena and its tributary, the rio Papagaio (upper rio Tapajós basin), Mato Grosso state, Brazil. The new species’ most remarkable feature is a unique colour pattern in live specimens, which combines eyes that are bright blue on the lower half and bright green (with a bright golden tinge) on the upper half, red pigmentation on the upper lip and a transparent opercle which allows a view of the pinkish red gill laments. The new species is apparently related to the group containing Moenkhausia oligolepis and M. sanctaefilomenae, which is also hypothesized to include M. pyrophthalma, M. diktyota and M. cotinho. The occurrence of Moenkhausia cosmops in both the headwaters of the upper rio Juruena (rio Tapajós basin) and upper rio Paraguai is congruent with other fish taxa and is indicative that a river capture has recently taken place in the area.
Type locality of Moenkhausia cosmops: Córrego Vinte e Cinco de Maio, Sapezal, Mato Grosso, Brazil. Photo by F. C. T. Lima
Wilson J. E. M. Costa: Five new species of the aplocheiloid killifish genus Rivulus, subgenus Melanorivulus, from the middle Araguaia River basin, central Brazil (Teleostei: Cyprinodontiformes: Rivulidae), pp. 55-68
Five new species of the genus Rivulus, subgenus Melanorivulus, are described from the middle Araguaia River basin: R. salmonicaudus n. sp., from streams and swamps directly associated with the main Araguaia River channel; R. rubromarginatus n. sp., from the Peixe River drainage; R. crixas new species, from the Crixás Açu River drainage; R. javahe n. sp., from the Verde River and Crixás Açu River drainages and, R. karaja n. sp., from the Formoso
River drainage. All new species are members of the clade referred to here as the R. zygonectes species group.
This group is diagnosed by the presence of a diffuse dark grey stripe between the postorbital region and caudal-fin
base, in which each included species is diagnosed by the unique colour patterns on the caudal fin in males.
Rivulus rubromarginatus, UFRJ 6474, male, holotype, 25.2 mm SL (one day after collection); Brazil: Estado de Goiás: stream tributary to rio Espingarda. Photo by W. J. E. M. Costa
Richard Winterbottom and Laura Southcott: Two new species of the genus Trimma (Percomorpha: Gobiidae) from western Thailand, pp. 69-76
Two new species of the genus Trimma are described. Trimma fucatum is characterized by the presence of predorsal scales, two opercular scales (one ctenoid, one cycloid), an interorbital and a slight postorbital trench, no elongate dorsal spines, and one dichotomous branch in the fifth pelvic-fin ray. When alive, T. fucatum has three to four diffuse rows of orange to yellow blotches, smaller yellow spots on the caudal fin, and a distinctive narrow red bar on the preopercle. Preserved specimens have straw-yellow blotches on a brown background. Trimma sanguinellus is characterized by a lack of predorsal and opercular scales, the presence of interorbital trenches, a slightly elongate second dorsal spine, a fleshy ridge on the predorsal midline, and an unbranched fifth pelvic-fin ray. Freshly-caught specimens are uniformly red-orange. Specimens preserved in ethanol are straw-yellow. Both new species are currently known only from the eastern margin of the Indian Ocean.
Trimma fucatum, 21.0 mm SL male paratype, Phuket, Thailand, ROM 68098. Photo by R. Winterbottom
Ricardo Jorge Casaux and Cecilia Yanina Di Prinzio: The diet of the large puyén Galaxias platei (Galaxiidae) at Rosario Lake, Patagonia, Argentina, pp. 77-86
In total, 1,355 large puyén (Galaxias platei) specimens were caught using trammel-nets laid on the bottom of Rosario Lake, Argentina. This fish was the most numerous species in the catches, followed by the Patagonian silverside (Odontesthes hatchery) and the rainbow trout (Oncorhynchus mykiss). The analysis of 333 stomach contents indicated that G. platei is a generalist and opportunistic feeder, preying mainly on benthic organisms. The amphipod Hyalella araucana was the main prey, followed by the chironomids Ablabesmyia sp. and Polypodilum sp. Hyalella araucana predominated in the diet of fish of all sizes and was almost the only prey item in larger individuals, whereas chironomids were important alimentary items in smaller specimens. Galaxias platei preyed intensively on H. araucanathroughout the year but seemed to take advantage of alternative prey species, such as chironomids, when they were available and abundant. The results are compared with previous studies carried out in Patagonia.
Aquarium photograph of a large puyén (Galaxias platei). Photo by C. Y. Di Prinzio