Does temperature affect the occurrence of penaeid spermatophore melanization related to successive manual extrusions? A case study with the closed thelycum Farfantepenaeus paulensis

Spermatophore successive manual extrusions are often employed in hatcheries, but it causes melanin deposition, decreasing sperm quality via cell degeneration. Melanization (brown or black spots) is an indicator of the moment to discard males. The evaluation of more efficient strategies is required to avoid it, increasing males’ lifespan. The effects of two temperatures (26 and 30 °C) on closed thelycum Farfantepenaeus paulensis spermatophore melanization and sperm quality after successive manual extrusions were evaluated. Wild-caught males were acclimated to laboratory conditions for 1 week and fed commercial broodstock feed and fresh-frozen food items ad libitum four times a day. Later, a 35-day trial was conducted with 24 males (26.05 ± 2.4 g) randomly distributed into eight 200-L tanks (4.3 shrimps m −2 ). Temperature was gradually increased from 23 to 26 °C or 30 °C. Only males showing a formed spermatophore and in the intermolt period were submitted to four consecutive manual extrusions every 11 days. Melanization was visually examined in extruded spermatophores, which were weighed. Spermatozoa were released in saline solution and observed in a hemacytometer under a light microscope. Morphological abnormalities (main body or spike malformations) were identified. Total and abnormal spermatozoa were counted in five fields of the hemacytometer to calculate sperm count and abnormal sperm rate. No significant differences were found on sperm quality among extrusions, but from the second extrusion onwards, an increase of melanization was evident. On the other hand, temperature did not affect the occurrence of spermatophore melanization related to successive extrusions.