EFFECTS OF SPERM CONCENTRATION, SPERM AGING, AND OTHER VARIABLES ON FERTILIZATION IN THE HORSESHOE CRAB, LIMULUS POLYPHEMUS L

¹ Department of Zoology and Entomology, Iowa State University, Ames, Iowa 50010
² Duke University Marine Laboratory, Beaufort, North Carolina 28516

The horseshoe crab, Limulus polyphemus, is an excellent species for fertilization studies since viable gametes can be easily obtained on a year around basis.

In reference to methodology for Limulus fertilization studies, the following prove to be adequate: collection of gametes by electrical stimulation, unwashed or washed spermatozoa (free of seminal fluid), and 5 to 10 minutes duration for sperm-egg mixing.

The aging of a 10% sperm concentration at 5° C for three or four days increases the per cent of embryonic development. This increase may be due to the death of abnormal spermatozoa.

Higher sperm concentrations definitely enhance higher per cent of development. With the dilution of sperm concentration, the per cent of development was drastically reduced even though several hundred spermatozoa per egg were present. The significance of the high number of spermatozoa is speculated as a necessity for (1) the chance penetration of a special site, (2) the release of sperm enzymes causing a chemical lysis in the egg envelope, or, more favorably, (3) a selection mechanism determined by the egg envelope for special genetical spermatozoa.

The number of spermatozoa per egg is calculated for each sperm concentration. In addition, a method for calculating the number of spermatozoa actually attaching to each egg is formulated.

Finally, some speculations on the evolution of such a system as found in Limulus are presented.

This article has been cited by other articles:

				M. E. Williams and M. G. Bentley Fertilization Success in Marine Invertebrates: The Influence of Gamete Age Biol. Bull., February 1, 2002; 202(1): 34 - 42. [Abstract] [Full Text] [PDF]