Acute exposure to hyperosmotic conditions reduces sperm activation by urine in the yellowtail tetra Astyanax altiparanae, a freshwater teleost fish

Nathalia Alcântara Rocha; Gabriel Marra Schade; Álvaro de Miranda Alves; Claudia de Souza Silva; Jacqueline Megumi Nakirimoto; Liura Sanchez Lauri; Lucca Gobatto Campos; Marcelo Galvão dos Santos; Nicole Nascimento Mesquita; Rachel Sordi Relvas; Rafaella Fernandes Carnevale; Se Yoon Oh; Victoria Portela Diniz Gaia; Vivian Renata Kida; Eneiva Carla Carvalho Celeghini; Mayra Elena Ortiz D´'Ávila Assumpção; José Augusto Senhorini; Hatus de Oliveira Siqueira; Nivaldo Ferreira Nascimento; Luciano Andrade Silva; Talita Maria Lázaro; José Antonio Visintin; Paulo Sérgio Monzani; George Shigueki Yasui

Acute exposure to hyperosmotic conditions reduces sperm activation by urine in the yellowtail tetra Astyanax altiparanae, a freshwater teleost fish

2020

In freshwater fish with external fertilization, sperm sampling can be contaminated with urine, which triggers motility and gives rise to decreased fertilization success. The maintenance of freshwater fish in hyperosmotic conditions may reduce urine production and improve sperm quality. Thus, the aim of this work was to verify if acute exposure to various NaCl concentrations improves sperm quality in the yellowtail tetra Astyanax altiparanae. Spermiation was induced using a single dose of carp pituitary gland (5 mg kg-1) and the males were maintained at various NaCl concentrations: NaCl 0.00% (control), NaCl 0.45% (hypoosmotic), NaCl 0.9% (isosmotic) and NaCl 1.0% (hyperosmotic) for 6 h at 26 °C. Sperm was collected and verified for activation by urine and motility traits. At 0.00%, 0.45%, and 0.90%, the sperm was motile just after sampling, indicating activation by urine. Surprisingly, at hyperosmotic conditions, no activation was observed. Other sperm and motility parameters did not show any statistical differences, including sperm viability (P = 0.7083), concentration (P = 0.9030), total motility (P = 0.6149), VCL (curvilinear velocity; P = 0.1216), VAP (average path velocity; P = 0.1231) and VSL (straight-line velocity; P = 0.1340). Our results indicate that acute maintenance at hyperosmotic conditions eliminates sperm activation by urine and maintains sperm quality. Such a new procedure is interesting for both basic and applied sciences, including reproductive practice in fish.

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