No abstract

Annual fishes, which inhabit temporary pools with extremely limited habitat complexity and niche availability, display remarkable sexual dimorphism, rapid growth, and enormous investment into reproduction, all traits associated with high energy requirement. This study tests three hypotheses for two syntopic annual fishes (Austrolebias minuano and Cynopoecilus fulgens) found in six wetlands of southern Brazil: (i) considerable morphological differences result in low dietary overlap, (ii) sexual dimorphism in both species leads to intraspecific diet segregation, and (iii) dietary richness increases during ontogenetic development, and is narrower in C. fulgens than A. minuano due to morphological limitations imposed by reduced size. The diet of 82 A. minuano and 211 C. fulgens individuals was analyzed over two annual cycles. The morphology was characterized by 26 measurements covering the entire body of both species. There was no evidence of morphological specialization related to food competition and the diet of A. minuano and C. fulgens showed high overlap. High food availability, high predator abundance, and high connectivity of adjacent wetlands are likely the main mechanisms allowing coexistence of both species. Within species, sexual dimorphism did not result in a decrease in dietary overlap, which reinforces the idea that morphological differences between the sexes did not evolve as a mechanism to decrease food competition. Large A. minuano did not have a more diverse diet than the smaller C. fulgens; however, increase in body size allowed both species to ingest larger prey. Morphological variability in both species was mainly related to ontogenetic development and reproduction.

Parasitic nematodes can infect both wild and cultivated fish species and may be the source of many diseases. The consumption of raw fish meat in many countries has been the responsible of nematode related zoonosis. Knowing the risk of consumption of contaminated fish by the local communities, the main goal of this paper is to quantify and report the presence of larvae with zoonotic potential of Contracaecum spp. and Eustrongylides spp. found in two exotic fish species from the Tramandaí River Basin in southern Brazil. The sample sites were two lagoons of the basin, the Itapeva lagoon and Palmital lagoon, sampled in the period of April 2018. Forty specimens of Acestrorhynchus pantaneiro and twenty specimens of Trachelyopterus lucenai were examined. A. pantaneiro presented a 58% and 4% prevalence and a mean intensity of 3.17 and 1 for Contracaecum spp. and Eustrongylides spp., respectively. Meanwhile T. lucenai presented a prevalence of 70% and 5% and a mean intensity of 1.92 and 1 of Contracaecum spp. larvae and Eustrongylides spp. larvae, respectively. Although larvae of Contracaeucum spp. are reported only in the literature in experimental infections, they were able to complete their biological cycle in some mammals with certain pathogeneses. However, larvae of Eustrongylides spp. infect humans, as reported in the literature, causing severe damage to the intestinal tract. Knowing that local populations may be at risk, we recommend that all prophylactic measures be taken in relation to fish consumption. This study also contributes to the knowledge concerning the parasitic fauna of the host species studied.

A new species of Pareiorhaphis is described from the upper Rio Doce basin. The description is based on a series of specimens recently collected in small headwater tributaries to the Rio Guanhães, a tributary of the Rio Santo Antonio, left bank of the Rio Doce in Minas Gerais State, eastern Brazil. Pareiorhaphis vetula, new species, is a small loricariid catfish with dark brown spots irregularly scattered over a brown background on the dorsal surface of body and along flanks. The new species differs from all other Pareiorhaphis species by having the maxillary barbel completely adnate to the lower lip and by adult males possessing a particularly elongate, sharply pointed, conical urogenital papilla. In addition, Pareiorhaphis vetula is further distinguished from most congeners by having a shorter pelvic-fin spine, or by possessing more numerous premaxillary teeth, and by lacking a dorsal-fin spinelet. A comparison with congeners P. nasuta, P. scutula and P. proskynita, which also occur in headwater streams of the Rio Doce basin is also presented.

Pareiorhaphis garapia, new species, is described based on specimens collected in the headwaters of the Arroio Garapiá, Rio Maquiné basin, a coastal drainage of Rio Grande do Sul State, southern Brazil. The new species is distinguished from all other Pareiorhaphis species in having the nuchal plate covered by thick skin, the exposed posterior process of the cleithrum comparatively narrow, and the last segment of the preopercular ramus of the latero-sensory canal reduced to an ossified tubule. The absence of a dorsal-fin spinelet, the reduced number of plates in the dorsal and mid-dorsal series of lateral plates, and morphometric traits also distinguish the new species from its congeners. The restricted geographic distribution of P. garapia, endemic to a headwater stream of the Rio Maquiné basin, and the syntopic occurrence of P. nudulus are discussed.