Austrolebias cheradophilus (Vaz-Ferreira, Sierra de Soriano & Scaglia de Paulete, 1965)

Lanés, Luis Esteban Krause, Gonçalves, Ândrio Cardozo & Volcan, Matheus Vieira, 2014, Discovery of endangered annual killifish Austrolebias cheradophilus (Aplocheiloidei: Rivulidae) in Brazil, with comments on habitat, population structure and conservation status, Neotropical Ichthyology 12 (1), pp. 117-124 : 120-121

Two populations of

A. cheradophilus

( Fig. 1 )

were discovered in southern Brazil, Jaguarão town, associated with a small tributary stream located in lowlands of Jaguarão River drainage, Patos-Mirim Lagoon hydrographic system ( Fig. 2 ). This study provides the first record of the species in Brazil, extending its distribution 150 km northwards ( Fig. 2 ) and constitutes the first citation of Megalebias subgenus in Jaguarão River basin.

Both populations (Site 1 and Site 2) were found in similar environments, represented by small (<1 km 2) and shallow (<30 cm) temporary palustrine ponds (represented by small ground depressions) located in grassland areas of private farms surrounding Jaguarão town ( Fig. 3 ). The two newly-discovered localities inhabited by A. cheradophilus are hydrologically isolated and separated by ca. 750 meters. Soil preparation activities for exotic pasture culture were observed on the surrounding areas after the species discovery. There are a local road, small groves of eucalyptus, houses and pastures for cows and horses between the two identified locations. The sites are not covered by protected areas. Wetland vegetation was dense and abundant, composed mostly of emergent macrophytes; mainly Eryngium sp. and floating rooted ( Echinodorus spp. , Leersia hexandra , Luziola peruviana , Ludwigia peploides , L. grandflora , Marsilea spp. , Myriophyllum aquaticum , Nymphoides indica , Regnellidium diphyllum , Polygonum hydropiperoides ) and submerged plants ( Scirpus submersus, Urtricularia gibb ), forming multispecific stands. The only other fish species found in co-occurrence with A. cheradophilus were the non-annual fishes Cheirodon interruptus (Jenyns) , Callichthys callichthys (Linnaeus) and Phalloceros caudimaculatus (Hensel) . Details of environmental and water characterization of each sampling site are shown in Table 1.

A total of 26 specimens of A. cheradophilus (8 males and 18 females) were sampled throughout the study. The specimens were found only in shallow areas (mean ± S.E. = 10 ± 1.30 cm) of the ponds. The total CPUA of populations was 0.86 fish/m 2. There was a variation of CPUA values among sampling sites, being higher in the site 1 (1.2 vs. 0.6 fish/m 2 in site 2) ( Table 2 ). The SL of males ranged between 32.14 and 49.17 mm (mean ± S.E. = 39.27 ± 2.41 mm) and of females between 25.11 and 41.6 mm (mean ± S.E. = 35.06 ± 1.29 mm). Even though the larger caught fish were males, there were no significant differences in SL between the sexes (t -test = - 1.678; P = 0.105). The Chi-squared test demonstrated marginal significant differences in proportions of sexes (2.25:1; χ2=3.846; P = 0.07). Information about variations in the number of sampled specimens, CPUA, and SL range, in each sampling site for each sex are given in Table 2 .

Length-weight relationship of A. cheradophilus (r 2 = 0.961; P = 0.0001) in the form of a regression equation was estimated as log W = - 2.596 + 3.083 log SL and the allometric coefficient “ b ” of the LWR was slightly hyperallometric (b = 3.08; CI 95% = 2.348 to 3.519). The condition factor of the specimens ranged from 1.84 to 2.42 (mean ± S.E. = 2.12 ± 0.04).

In accordance with application of IUCN criteria, Austrolebias cheradophilus was considered as “Critically Endangered” species in Brazil, being included in the criteria CR B2ab (ii, iii). The species presents reduced area of occupancy (AOO less than 10 km²), populations severely fragmented (a) and continued decline (b) in area of occupancy (ii) and quality of habitat (iii).

Figures

Fig. 1. Austrolebias cheradophilus sampled in Jaguarão Riv- er, Patos-Mirim Lagoon system, southern Brazil: (A) Male, 49.2 mm SL, (B) variation in color pattern of males (41.3 mm and 49.2 mm SL) and (C) female, 41.2 mm SL. Photos by Matheus Volcan.

Fig. 2. (A) Occurrence of Austrolebias cheradophilus in Jaguarão River basin, Patos-Mirim Lagoon system, southern Brazil (asterisc), and previous record of the species closest to Brazil (Black square). (B) Map detailing the occurrence of the species in lower Jaguarão River, Patos-Mirim Lagoon system, southern Brazil.

Fig.3.Temporary ponds(Site 1 aboveandSite 2 below)inhabited by Austrolebias cheradophilus in lowlands of Jaguarão River basin, southern Brazil.