Prove della partenogenesi in femmine di Acritus nigricornis (Hoffman) raccolte in Sud Italia (Coleoptera Histeridae)

Abstract

EVIDENCE FOR PARTHENOGENESIS OF Acritus nigricornis (HOFFMAN) FEMALES FROM SOUTHERN ITALY (COLEOPTERA HISTERIDAE)

Preliminary observations showed population of Acritus nigricornis (Hoffman) in Bari province (Apulia, Southern Italy) to be apparently composed by females only. Supposed parthenogenesis was tested in the laboratory by feeding in small jars as many as 123 individuals. These were collected in their reproductive period (August-September) from masses of plant debris of agricultural origin.

Larvae were obtained in 20 jars (out of 41), each containing 3 adults. Adults kept from the “positive” jars were examined by dissecting them in saline. No male was found throughout, and every female was found to lack sperm in its spermatheca.

Because a similar population feature (females only in the field) was previously known in the outskirts of Madrid, author supposes A. nigricornis to be an instance of “geographical parthenogenesis”. Although males of this species are reported in the taxonomic literature, they seem to be lacking or (it may be) very rare in Bari province; anyhow, they do not attend reproduction in this territory.

Attraverso una sperimentazione di laboratorio viene provata per Acritus nigricornis (Hoffman) la capacità di riprodursi per partenogenesi. Le prove provengono dalla constatata assenza di spermatozoi nella spermateca di femmine provenienti da terrarï dove si era manifestata la comparsa di larve.

Dalla dissezione di numerosi adulti, raccolti in detriti vegetali di origine agricola in provincia di Bari, risulta l’assenza dei maschi nella zona, salvo la possibilità che essi siano molto rari. Ciò si rapporta con quanto è già noto in letteratura, in merito al reperimento di sole femmine nei dintorni di Madrid.

Poichè la letteratura tassonomica attesta l’indubbia esistenza dei maschi di A. nigricornis, l’autore ritiene che questa specie sia soggetta a un fenomeno di “partenogenesi geografica”.

Parole-chiave: genitali interni, femmine, spanandria, partenogenesi geografica.