SPERMATOGENESIS OF THE BLACK-CLAWED CRAB, LOPHOPANOPEUS BELLUS (STIMPSON) RATHBUN

Abstract

1. During the latter part of June and early portion of July the testis of Lophopanopeus bellus (Stimpson) Rathbun is in the best condition for the study of the spermatogenesis process.2. Primary and secondary spermatogonial divisions can be distinguished. The spermatogonial chromosomes are univalent and probably number around 124.3. Large nutritive cells are frequently associated with spermatogonial strips in tubules where there are mature spermatozoa. These have irregular nuclei, and are, undoubtedly, produced from primary spermatogonia which have failed to mature.4. The primary spermatocyte undergoes growth, parasynapsis, tetrad-formation and reduction division. There are 62 bivalent chromosomes seen in polar views of the metaphase stages of this division.5. During the growth period a chromatoid body appears in the cytoplasm, and when the reduction division takes place this wanders undivided to one of the poles of the cell, resulting in the formation of two kinds of secondary spermatocytes, one which possesses the structure and the other which is devoid of it.6. There is no rest period between the primary and secondary spermatocytes. The division of the latter is equational and produces two types of spermatids, one having a chromatoid body and the other which is minus such a structure. This last type is about three times as numerous as the former one.7. At an early stage, the chromatoid body is expelled from the spermatids which contain it, and from then on all the spermatids undergo similar complicated transformations. These changes bring about the formation of the radial spermatozoa which are packed away in single spermatophores within the vas deferent ducts.8. Four kinds of mature spermatozoa may be distinguished, namely, three-, four-, five- and six-rayed types. The four- and five-rayed spermatozoa are the ones which are encountered most frequently.