Search

Understanding the effects of environmental factors on sperm motility characteristics can increase artificial reproduction efficiency in species that do not spawn naturally in captivity, such as Megaleporinus obtusidens. This study evaluated the effects of the osmolality (25, 85, 145, 205, 265, and 325 mOsm kg -1 ) and composition of activating solutions (NaCl, KCl, or fructose) on the percentage of motile sperm, and the swimming velocity and path straightness of M. obtusidens spermatozoa. The concentrations of major ions in the seminal fluid were also assessed and Na + (74.46 mmol L -1 ), K + (37.24 mmol L -1 ), and Cl - (114.29 mmol L -1 ) were the most abundant. When the activating solution was hypertonic (325 mOsm kg -1 ) compared to the seminal fluid (293 mOsm kg -1 ), sperm motility was completely inhibited. A wide range of osmolalities that initiated sperm motility were identified for all three solutions. Both, the percentage of motile sperm and the motility duration were reduced (P < .05) at extreme osmolalities. At 145 mOsm kg -1 , the percentage of motile sperm remained high (>50%) up to 40 s after activation and the motile phase lasted for >50 s, regardless of the activating solution composition. Over the postactivation time, the curvilinear velocity and straightness were similar (P > .05) for fructose and NaCl solutions, whereas KCl solutions induced a higher (P < .05) curvilinear velocity, lower (P < .05) straight-line velocity, and a circular swimming motion in spermatozoa. Our results suggest that a reduction in osmolality, using both non-electrolyte and electrolyte solutions, is the main trigger for the onset of spermatic movement in M. obtusidens sperm., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Use of carp pituitary extract (CPE) as a hormone inducer for Leporinus obtusidens is cost-prohibitive; moreover, CPE contains unknown concentrations of gonadotropins. We evaluated the efficacy of gonadorelin as a substitute by analyzing its effect on sperm characteristics of L. obtusidens and cost-effectiveness (20, 40, 60, 80, and 100μgkg -1 ). Untreated and CPE-treated (4mgkg -1 ) fish were used as negative and positive controls, respectively. Following a single intramuscular dose of hormones, semen was collected at 200°-h. At doses from 60μgkg -1 , all fish produced higher milt volume (P<0.05) than the negative control (0.2-0.8mLkg -1 ), equal (P>0.05) to the positive control (3.52±0.97mLkg -1 ). Gonadorelin did not affect sperm concentration (P>0.05). The percentage of morphologically normal spermatozoa was >64% in all treatments. The number of spermatozoa with intact membrane (70%-85%) was equal (P>0.05) to that in the controls. Relative to the negative control, gonadorelin did not affect the motility rate (P>0.05). Curvilinear velocity was equal (P>0.05) to that in both controls. The sperm swimming path was linear (0.9) 10s after activation and was not (P>0.05) dose-dependent. Considering the response rate of gonadorelin-induced fish and the similarity of semen quality compared to controls, the lowest effective dose to produce a higher volume of semen in L. obtusidens is 60μgkg -1 , and the cost to induce 1kg of L. obtusidens is 14.0% lower than that with CPE., (Copyright © 2017 Elsevier B.V. All rights reserved.)