Yelloweye Pearlfish

description

Conservation. Austrolebias ephemerus was recorded in small pools within private properties that are generally used for cattle farming. Since the discovery of the species in 2015, one third of the six pools with occurrence of the species were lost owing to their conversion to pasture areas. The species presents a low population density, occurring in small and isolated pools that, combined, have an area less than 1 hectare and in a region under strong pressure from livestock husbandry. Austrolebias ephemerus presents a reduced (AOO <10,000 m ²) and severely fragmented (a) area of occurrence and is experiencing continued decline (b) in the area of occupancy (ii) and in the quality of habitat (iii). In accordance with the IUCN (2011) criteria, A. ephemerus should be considered a “ Critically Endangered ” species under the category CR B 2 ab (ii, iii), and as such, the species should be included in future lists of the endangered fauna from Brazil.

Austrolebias ephemerus (Cyprinodontiformes: Rivulidae), a new annual fish from the upper Rio Paraguai basin, Brazilian Chaco

description

Description. Morphometric and meristic data of the holotype and paratypes are presented in Table 1. Males larger than females, largest male examined 31.7 mm SL, largest female 28.1 mm SL. Dorsal profile slightly concave on head, convex from nape to end of dorsal fin base, straight on caudal peduncle. Ventral profile convex from lower jaw to origin of anal fin base, nearly straight on caudal peduncle. Greatest body depth at dorsal fin origin. Body deep and compressed. Snout blunt and jaws short. Dorsal fin rays in males 24 – 25; in females 18 – 20. Tip of dorsal fin rounded. Dorsal fin origin at vertical through 1 st and 4 th anal-fin rays in males and through 2 nd and 5 th anal-fin rays in females. Origin of dorsal fin at vertical through neural spines of 7 th and 9 th vertebrae in males and through neural spines of 9 th and 12 th vertebrae in females. Anal-fin rays in males 27 – 30; in females 23 – 28. Tip of anal fin rounded in males. Anteromedian rays of anal fin of females lengthened, resulting in nearly triangular anal fin shape. Origin of anal fin at vertical through pleural ribs of 6 th and 9 th vertebrae in males and in females through pleural ribs of 8 th – 11 th vertebrae

Austrolebias ephemerus (Cyprinodontiformes: Rivulidae), a new annual fish from the upper Rio Paraguai basin, Brazilian Chaco

diagnosis

Diagnosis. Austrolebias ephemerus can be distinguished from all species belonging to the A. bellottii species group by presenting pectoral fin posterior margin on vertical between base of 5 th and 7 th anal fin rays in females (vs. between pelvic fin origin and base of 2 nd anal fin ray), and by presenting a greater number of gill rakers in the first branchial arch (4 – 5 + 14 – 15 vs. 3 – 4 + 10 – 12; except in A. vandenbergi). It is distinguished from all species of the A. bellottii species group, except A. accorsii and A. queguay, by having a lower head width in males (55.3 – 61.1 % SL vs. 61.9 – 72.6 % SL) and females (58.4 – 62.8 % SL vs. 63.4 – 73.2 % SL). Austrolebias ephemerus also differs from all species of the A. bellottii species group, except A. melanoorus and A. queguay, by having fewer neuromasts in the preopercular series (16 – 23 vs. 24 – 29). In addition, the following characters are useful for diagnosing A. ephemerus from the other species of the A. bellottii group: from A. accorsii by having urogenital papilla attached to anal fin (vs. not attached), more scale rows in transversal series (13 – 14 vs. 12), position of dorsal fin origin in relation to the neural s

Austrolebias ephemerus (Cyprinodontiformes: Rivulidae), a new annual fish from the upper Rio Paraguai basin, Brazilian Chaco

distribution

Distribution (Fig. 5). Known only from six small temporary pools on the left bank of the Rio Paraguai basin, between the left bank of the Rio Amonguijá and the right bank of the Córrego Progresso, municipality of Porto Murtinho, Mato Grosso do Sul state, Brazil.

Austrolebias ephemerus (Cyprinodontiformes: Rivulidae), a new annual fish from the upper Rio Paraguai basin, Brazilian Chaco