XIII.—The Cytology of a Diploid Bisexual Spider Beetle, Ptinus clavipes Panzer and its Triploid Gynogenetic form mobilis Moore

Abstract

SynopsisThe chromosome constitution of the bisexual beetle Ptinus clavipes Panzer (2n = 18) and of its gynogenetic form P. clavipes f. mobilis Moore (3n = 27) have been investigated. The triploid mobilis lives in close association with the bisexual species and mates freely with the males. Eggs from virgin females never pass beyond the metaphase stage and successful completion of maturation is dependent on the presence of sperm. An endomitotic split is apparent in prophase chromosomes and leads to the formation of twenty-seven pseudobivalents which undergo a pseudomeiotic division. Only one maturation division has been observed. Although the fate of the activating sperm has not been resolved it is thought that sperm nuclei give rise to isolated haploid nuclei in some eggs and interfere with normal cleavage in others. Since the triploid form may also mate with males of Ptinus pusillus Sturm and P. fur. L. with reduced numbers of progeny the affinities of the gynogenetic form is discussed. This is the only known case of gynogenesis in Coleoptera.

Cytological investigations of parthenogenesis in gall wasps (Cynipidae, Hymenoptera)

“…sawflies. Rudimentary parthenogenetic development found in eggs of virgin females of B. pallida resembles the abnormal nuclear behaviour found in eggs of the unmated gynogenetic spider beetle Ptinus clavipes f. mobilis (Sanderson, 1960). It is possible therefore that in gall-wasps the sperm may only activate.…”

“…mobilis Moore, the triploid weevil Listroderes costirostris Schon. and sawflies (Sanderson, 1960(Sanderson, , 1970(Sanderson, and 1973, all of which tolerate a high degree of chromosomal irregularity. Diploid nuclei are common in somatic cells of haploid gall wasp males as in other Hymenoptera and, where less than the haploid number of chromosomes appear as in loose spermatocyte cells, the loss can usually be attributed to breakage of the nuclear membrane.…”

“…has an enigmatic bouquet stage comparable to pachytene with the thirty chromosomes forming a haploid number of loops apparently by tandem linkage in threes, but reappearing after the diffuse stage as thirty univalents (Sanderson, 1973) which undergo a non-reductional maturation division. The triploid gynogenetic Ptinus clavipes f. mobilis Moore has a bouquet stage with the triploid number of loops (Sanderson, 1960) and therefore may be classed as pseudomeiotic. In the triploid cynipid Diplolepis eglanteriae there are no detectable synaptic phenomena and here parthenogenesis is ameiotic.…”

Significance of Parthenogenesis in the Evolution of Insects

“…Coleoptera: Ptinidae-Ptinus clavipes Panzer f. mobilis Moore [San derson (58)]. The parthenogenesis is pseudogamy; the egg does not de velop without the entering of a sperm cell of diploid bisexual Ptinus cla vipes; Curculionidae-Thelytokous species and races [Suomalainen (92,93,95,96,98,99,100) ; Seiler (75); Mikulska (40 to 43) ; Takenouchi (104)].…”

Parthenogenesis in Hexapoda: holometabolous insects

“…Thelytoky is also supposed in European Batrisodes unisexualis Besuchet, (Pselaphidae; Besuchet, ) and in a triploid member of the genus Cantabrogeus Salgado, 2000 (Leiodidae; Angus, Edwards, Luque, & Labrada, ). In addition, pseudogamy, a form of sperm‐dependent parthenogenesis, sometimes also termed gynogenesis (in the Glossary to our previous paper [Vershinina & Kuznetsova, ; ] gynogenesis was erroneously equaled to automixis) was detected in the triploid parthenogenetic form of Ptinus latro Fabricius, 1775 (= P. mobilis Moore, 1957) from the family Anobiidae (Sanderson, ).…”