Anatomia dei genitali interni e modalità di inseminazione in alcuni Coleotteri Anticidi

Abstract

ANATOMY OF THE INTERNAL GENITALIA AND INSEMINATION MODALITIES IN SOME ANTHICIDS (COLEOPTERA)

Throughout the examination of 23 species of Anthicids, a comparative study is made of the internal genitalia in both males and females. The insemination strategies in this family are discussed on the basis of the anatomical data.

In most species, the male insemination device includes a powerful ejaculatory pump, of which three structural types can be divided. Two of these types exhibit the property of increasing their own muscular mass during the imaginal life, as long as the individual attains its own reproductive maturity. A further male evolutionary trend affects the ejaculatory duct length, which can be even 6 times as long as the insect body. A conspicuous equipment of male accessory glands occurs both Notoxinae and Microhoriini; it is related to the production of the abundant gelatinous sperm fraction. A pair of additional seminal vesicles is a characteristic feature of two species, Cordicomus instabilis and Formicomus pedestris.

Spermatheca of most species includes a membranous receptaculum, which is able to swell whilst it is filled with sperm. Filling does probably occur during the copulation, due to the pressure produced by the male ejaculatory pump.

Microhoriini exhibit a second type of spermatheca, which is lacking in its gland. Female genita- lia in this tribe do retain their ancestral bursa copulatrix, where one or more spermathophores are built during the copulation. Likely, the receptaculum filling is delayed (after spermathophores are dissolved) and it is probably accomplished by the musculature of the female genitalia.

Key words: Coleoptera, Anthicidae, internal genitalia, comparative anatomy, insemination.

Viene studiata la variabilità anatomica dei genitali interni maschili e femminili in 23 specie di Anticidi.

Nel maschio si individuano due tendenze evolutive: (a) potenziamento dell’ampolla eiaculatrice, (b) allungamento del dotto eiaculatore. Nella femmina, si individua la tendenza al possesso di un ricettacolo spermatecale capace di rigonfiarsi durante il riempimento.

I dati anatomici, coordinati con osservazioni su consistenza e localizzazione dello sperma, indicano due modalità di inseminazione: (I) uso di sperma libero, direttamente pompato dal maschio all’interno del ricettacolo della spermateca; (II) fabbricazione di spermatofori all’interno della borsa copulatrice e trasferimento dilazionato dello sperma nel ricettacolo per azione muscolare delle vie genitali femminili.

Parole chiave: Coleoptera, Anthicidae, genitali interni, anatomia comparata, inseminazione.