Conjugate Spermatozoa of the North American Opossum

Abstract

IN 1887 Emil Selenka1 published a monograph describing the reproductive processes, and the embryology, of the North American opossum (Didelphys marsupialis L.). One of the many observations made on a colony of these animals, which Selenka maintained in Erlangen, Germany, was that the semen, recovered from the vagina of females shortly after coitus, contained many spermatozoa which swam in closely coupled pairs. Selenka referred to these paired cells as “copulating” spermatozoa, and the drawings which he published showed clearly that these paired spermatozoa are associated in a specifically oriented manner. In 1902. von Korph2 showed that the paired spermatozoa occurred in the epididymis, but not in the testes. This observation was confirmed later by Retzius3, Jordan4, and finally by Duesberg5 in 1920. Since that time the phenomenon has been briefly referred to only by Wilson6, in 1928, who recommended the phrase ‘conjugate spermatozoa’ instead of ‘copulating spermatozoa’, and by McGrady7 in 1938. In the past quarter of a century the phenomenon has been ignored, and is a notable omission from, contemporary reviews on spermatozoa.