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Changes in Sperm Quality of Silver (hypophthalmichthys Molitrix) and Bighead Carps (hypophthalmichthys Nobilis) During the Spawning Season

MD. MOFIZUR RAHMAN
Department of Fisheries and Marine Science, Noakhali Science and Technology University, Sonapur, Noakhali-3814, Bangladesh

MOHAMMAD SHAMSUR RAHMAN
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh

MAHMUD HASAN
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

This study investigated the changes in spermatological parameters and biochemical composition of the seminal plasma of silver carp Hypophthalmichthys molitrix and bighead carp Hypophthalmichthys nobilis across three spawning seasons (early, mid and late). While silver carp had similar levels of motile sperm in early and mid seasons (early: 96±1%; mid: 95±1%), highest motile sperm in bighead carp was found only in the early season (95±1%). Sperm concentration in the three spawning seasons were 3.15±0.02 ×10⁹mL^-1 (early); 2.91±0.04 ×10⁹ mL^-1 (mid); 2.60±0.14 ×10⁹ mL^-1 (late) in silver carp and 2.96±0.03 ×10⁹ mL^-1 (early); 2.79±0.02 ×10⁹ mL^-1 (mid); 2.65±0.12 ×10⁹ mL^-1 (late) in bighead carp. In silver carp, fertilization rate observed across spawning seasons were 75±3% (early); 61±1% (mid); 61±2% (late). However, drastic changes in fertilizability was observed in bighead carp (early: 79±3%; mid: 60±3% and late: 25±2%). Of the seminal plasma components, chloride and total protein levels were significantly changed in both fishes over seasons. The results of this study have implications in improving the quality of fish seed by improving the quality of fish sperm.

Keywords: Sperm Quality, Hypophthalmichthys molitrix, Hypophthalmichthys nobilis, Spawning Season

Location: Gazipur, Bangladesh

Start Date: 00-04-2009

End Date: 00-09-2009

Program Area: Variety and Species

Commodity: Carp fish

Objectives:

To investigate the changes of sperm quality, and physical and biochemical characteristics, of silver and bighead carps’ semen across three spawning seasons in Bangladesh.

Methodology:

Experimental Fishes: Silver (57.9±2.2 cm; 2.2±0.2 kg; mean ± SEM) and bighead carps (61.9±0.6 cm; 2.8±0.2 kg; mean ± SEM) broods of Bangladesh Rural Advance Committee (BRAC, an NGO ) Fish and Prawn Hatchery, Rajendrapur, Gazipur, Bangladesh were used as the experimental fishes. A total of 50 (25 male and 25 female) fishes were used as the stock animal. This study was undertaken during the commercial operation of this hatchery between April and September 2009 dividing the spawning season of silver and bighead carps into three seasons as early (April to May), middle (June to July ) and late (August to September). Conditioning and hormonal induction of brood fishes: Selected brood fishes were conditioned by holding them in 1,600 L flow-through-tank system for a period of 6 hr prior to induction by hormone. Male and female broods were held in different holding tanks and given mechanical aeration. Hormonal solution was prepared and applied to the brood fishes following standard protocols. Human chorionic gonadotropin (HCG; Fuda Hormone Factory, Xiamen, China) and the extract of the commercially available pituitary gland (PG; Ducamar Company, Cantabria, Spain) were used as stimulating agents. Female fishes were given a single dose of 200 IU HCG.kg^-1 body weight (BW) as stimulating dose and 500 IU HCG + 3 mg PG.kg^-1 BW as the resolving dose. In males, 2 mg PG.kg^-1 BW was applied. Milt and egg collection: Milt samples were collected from sexually matured males in sterilized plastic vials by pressing gently on the abdomen. Samples were drawn every week during the entire study period with three replicates. Males were used repeatedly across all three seasons. However, eggs were collected from matured female broods into a plastic bowl by stripping immediately after ovulation and mixed with milt for fertilization. Rate of fertilization was measured 8 hr after fertilization by examining a minimum of 150 eggs per replicate. Detection of sperm motility (%): Sperm motility was determined immediately after collection of fresh milt sample. Freshly collected milt sample was diluted with 0.3% NaCl (activating solution) at 10:1 ratio (10 mL activation solution and 1 mL milt sample). Diluted samples (4-5 μL) was placed on a slide covered by a cover slip (22×22 mm) and sperm motility was determined using a microscope (biomicroscope, XSZ21-5DN, China) connected with a laptop (DELL, Germany) at 1600x magnification and expressed as percentage. Determination of sperm concentration (× 10⁹ mL^-1): Sperm concentration was determined using improved Neubauer counting chamber (area 1 mm² and depth 0.1 mm) (Germany). Milt sample was diluted with 0.3% NaCl solution at 1000:1 ratio. The diluted sample was placed on the counting cells of a Neubauer chamber with a cover slip and was left for approximately 10 min to allow the sperm cells to be settled on the counting chamber. The sperm cells were counted by a compound light microscope (LABOMED CXRII, USA) at 160x magnification connected to a CCD camera (Unican, HV-2616, Japan) and picture was displayed on a monitor (Samsung 17 inch CRT monitor, Japan) through a TV card (PERPECT Smart Power, China). Sperm concentration was calculated. Seminal plasma assay: Milt samples were centrifuged (REMI RM12C, Laboratory Centrifuge, Germany) for 10 min at room temperature at 8,000 g to separate the seminal plasma and preserved at -20 ºC until analysis. While seminal pH was measured using standard pH electrodes after 30 min of sampling, mineral and organic components (Na⁺, K⁺, Cl^-, Ca²⁺, total protein, albumin and cholesterol) were measured. Data Analysis: All percent data were transformed into square root before statistical analysis, while sperm concentration data were transformed into natural log. Data were analyzed using ANOVA followed by Tukey’s HSD post hoc for multiple comparisons. Data have been presented as mean ± SEM and analyzed by using the statistical software SPSS version 10.0 with the level of significance at p<0.05.

Source of Information: Asian Fisheries Science 24 (2011):413-425

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The quality of sperm changes in both species as the spawning seasons progressed. No single factor is responsible for change in sperm quality. However, age and size of the breeders, repeated use of the same breeder over seasons, nutritional requirement, stocking density, hormonal manipulation and environmental changes together or individually may affect the sperm quality that changes between spawning seasons.

Knowledge Management: Journal