Effects of cryoprotectants and low temperatures on hatching and abnormal embryo development of Prochilodus lineatus (Characiformes: Prochilodontidae)

This study evaluated the effect of the cryoprotectants and the low temperatures on the embryonic development of Prochilodus lineatus, describing their main morphological alterations. On chilling sensitivity test, the survival rates at the twenty somites stage (20S) were 53.6% at 0ºC, and 100% in 5ºC. To test toxicity, the embryos were exposed to a graded series of 1,2-Propanediol (PROP), dimethyl sulfoxide (Me2SO4) and glycerol (GLY), terminating in a solution of high osmolarity. There was no significant difference in the embryos survival of toxicity test between series of PROP and Me2SO4 in the 6S and 20S. In the cooling protocols, were evaluated the effects of low temperature associated with cryoprotectants. At 5ºC, PROP showed survival rates above 75% in the gastrula stage (G) and above 90% in the 6S and 20S stages. High rates of abnormalities were observed, and the most recurrent were: small bodies, fins presenting uncontrolled cell growth, membrane rupture, and retraction. These results demonstrate the need to use cryoprotectant solutions, even when there is no ice nucleation, and, on the other hand, shows that high cryoprotectant concentrations promote numerous morphological lesions, compromising normal embryonic development.(AU)

Este estudo avaliou os efeitos dos crioprotetores e das baixas temperaturas no desenvolvimento embrionário de Prochilodus lineatus, descrevendo suas principais alterações morfológicas. Nos testes de sensibilidade ao frio, as taxas de sobrevivência, no estágio de vinte somitos (20S), foram de 53,6% a 0ºC e 100% a 5ºC. Nos testes de toxicidade, os embriões foram expostos a uma série graduada dos crioprotetores: 1,2-Propanediol (PROP), dimetilsulfóxido (Me2SO4) e glicerol (GLY), terminando em uma combinação de alta osmolaridade. Não houve diferença significativa na sobrevivência dos embriões nas séries do PROP e Me2SO4 nos estágios de 6S e 20S. Nos protocolos de resfriamento, foram avaliados os efeitos da baixa temperatura associados as séries crioprotetoras. A 5ºC, o PROP apresentou taxas de sobrevivência acima de 75% no estádio de gástrula (G) e acima de 90% nos estádios 6S e 20S. Foram observadas altas taxas de anormalidades sendo as mais recorrentes: corpos pequenos, nadadeiras apresentando crescimento celular descontrolado, ruptura da membrana e retração vitelínica. Estes resultados demonstram a necessidade do uso das soluções crioprotetoras, mesmo não havendo nucleação de gelo e, em contrapartida, demonstra que as elevadas concentrações crioprotetoras promovem numerosas lesões morfológicas, comprometendo o desenvolvimento embrionário.(AU)

Cytogenetic characterization of the strongly electric Amazonian eel, Electrophorus electricus (Teleostei, Gymnotiformes), from the Brazilian rivers Amazon and Araguaia

A karyotype analysis of the electric eel, Electrophorus electricus (Teleostei, Gymnotiformes), a strongly electric fish from northern South America, is presented. Two female specimens were analyzed, one from the Amazon River and one from the Araguaia River. The specimens had a chromosomal number of 2n = 52 (42M-SM + 10A). C-bands were present in a centromeric and pericentromeric position on part of the chromosomes; some interstitial C-bands were also present. Heteromorphic nucleolus organizer regions (NORs) were detected in two chromosome pairs of the specimen from the Amazon River. The chromosome number and karyotype characteristics are similar to those of other Gymnotidae species. The genera Electrophorus and Gymnotus are positioned as the basal lineages in the Gymnotiformes phylogeny.