Fertilization Success in Crustaceans from the Male Perspective: Sperm Ultrastructure and Sperm Economy

The morphology and ultrastructure of spermatozoa are very diverse among the classes of the Crustacea, but how this diversity relates to sperm production and sperm economy has been little studied. A brief description of major forms and shapes of crustacean spermatozoa is provided and an overview of sperm ultrastructure is updated. Spermatogenesis is a costly process for males, as it requires considerable energy and time to achieve the required quality and quantity to guarantee success in fertilizing the eggs of females. Sperm are embedded in seminal fluids to preserve stored sperm and/or counteract the risk of sperm competition, which contributes significantly to the energy budget and sperm economy. In general, sperm are transferred in spermatophores of very diverse sizes and shapes within the different crustacean groups. Strategies related to sperm economy depend on the physical size of the partner, mating history, and perception of future mating opportunities. The mechanics involved in spermatogenesis and production of seminal fluids vary among the different crustacean classes and between different taxa. Sperm economy has direct links to sperm limitation in several male-centered fisheries. To better understand the evolutionary processes and to design suitable applied strategies (e.g., fisheries management or aquaculture), better knowledge is required about sperm histochemistry and functional morphology; furthermore, a wider taxonomic coverage is recommended by including commercial and non-commercial crustaceans beyond the decapods.

Optimization of artificial fertilization in the stinging catfish Heteropneustes fossilis (Bloch)

SummaryDetermination of optimum sperm requirement in artificial breeding helps to improve the fertilization efficiency, sperm economy and minimize the sacrificing of males for milt. Quantification of sperm cells was done by spectrophotometer at 420 nm followed by haemocytometer counting. Best correlation (r2 = 0.97) was recorded. The minimum number of sperm required for optimal fertilization success in Heteropneustes fossilis was determined. An average fertilization success of 78–93% was recorded at 8 × 103 to 8 × 107 sperm per egg. The optimum contact duration of gametes was 5 minutes. The highest fertilization rate of 98.18% was recorded at 8 × 107 spermatozoa.egg−1.