Ovarian control of oostegite formation in the terrestrial isopod, Armadillidium vulgare (Malacostraca, Crustacea)

Histological studies on the marsupium of two terrestrial isopods (Crustacea, Isopoda, Oniscidea)

The marsupium, a brood pouch in peracarid crustaceans (Crustacea, Malacostraca) has evolved in terrestrial environment for providing nutrition and optimal conditions for embryogenesis. In the present study we give details on the histology and ultrastructure of its constituting elements such as oostegites and cotyledons. Marsupia of two different eco-morphological types of woodlice, namely the non-conglobating species Trachelipusrathkii Brandt, 1833 and the conglobating species Cylisticusconvexus De Geer, 1778 were investigated. Light microscopic (LM) studies showed some differences in the main structure of the two species' brood pouch: in Trachelipusrathkii, a 'clinger' type woodlice, the oostegites bend outwards during brood incubation as growing offspring require more space, while in Cylisticusconvexus, a 'roller' type isopod, the sternites arch into the body cavity to ensure space for developing offspring and still allowing conglobation of the gravid females. The quantitative analysis of the oostegites' cuticle proved that the outer part is about 2.5 - 3 times thicker compared to the inner part in both species. Electron microscopic (TEM) examinations show only small histological differences in the oostegites and cotyledon structure of the two species. Cellular elements and moderately electron dense fleecy precipitate are found in the hemolymph space between the two cuticles of oostegites. The cells contain PAS positive polysaccharide areas. TEM studies revealed some differences in the cotyledon ultrastructure of the two species. Cotyledons of Trachelipusrathkii consist of cells with cristate mitochondria and granular endoplasmic reticulum with cisterns. Cotyledons of Cylisticusconvexus consist of cells with densely cristate mitochondria and ribosomes attached to vesicular membrane structures. In both species cells with electron dense bodies were observed. We conclude that - besides the differences in marsupial shapes - the fine structure of the oostegites and cotyledons is hardly affected by the eco-morphological type, specifically the conglobating or non-conglobating character of the studied species.

Androgenic gland hormone is a sex-reversing factor but cannot be a sex-determining factor in the female crustacean isopods Armadillidium vulgare

Sex reversal of female isopods, Armadillidium vulgare, has been induced by implantation of the androgenic gland (AG) into individuals after the initiation of morphological sex differentiation. The focus of the present study is to examine whether female gonads are reversed by the androgenic gland hormone (AGH) during the sexually undifferentiated period through postembryonic development in A. vulgare. Instead of injections of AGH, three AGs were implanted into each genetic female at various developmental stages to induce sex reversal. Before implantation fresh AGs were treated with ethanol to stop AGH synthesis, but then still contained AGH. These AGs have been referred to as ethanol-treated AGs (t-AGs). Development of a testis was used as an indicator of gonadal sex reversal. The gonads of genetic females were transformed into testes by implantations of t-AGs during the sex differentiation period. However, when genetic females received implants at sexually undifferentiated stages, development of their gonads was not reversed in the male direction. These results suggest that after the onset of gonadal sex differentiation, AGH is a sex-reversing factor that can turn a female gonad into a male gonad. AGH cannot be a sex-determining factor in female A. vulgare, as undifferentiated gonads of genetic females are not sex reversed by the hormone.

Sex reversal by implantations of ethanol-treated androgenic glands of female isopods, Armadillidium vulgare (Malacostraca, crustacea)

The androgenic glands (AGs) of malacostracan crustaceans are responsible for differentiation of male sexual characteristics, and sex reversal is readily obtained by implantation of AGs in female crustaceans. In order to induce sex reversal, we implanted inactive AGs (dead cells) into young females of Armadillidium vulgare. Before implantation fresh AGs (living cells) were treated twice with 80% ethanol for 3 min and kept in crustacean physiological saline for 30 s. We refer to these AGs as ethanol-treated AGs (t-AGs). Stage 6 females were used as recipients of t-AG implantation. They received an implant of three t-AGs (3 t-AGs) three times, once each week. Testis formation in recipients was used as an indicator of the masculinized levels of female gonads. Female sexual characteristics were masculinized in proportion to the number of 3 t-AG implantations. Three implantations (total number of t-AGs, nine glands) induced development of testes, penes, and male copulatory organs in the recipient females. Furthermore, they could produce progeny. These results show that t-AG implantations are capable of inducing masculinization of female sexual characteristics. The procedure of three implantations with 3 t-AGs at stage 6 is enough to transform the sex from a genetic female into a functional male. If t-AGs are used to implant instead of fresh AGs, we can detect the effects induced by newly formed AGs of recipient females, not by implanted donor's AGs. The present method may be useful for examining the regulatory mechanism of sex differentiation of female A. vulgare.

Sexual bipotentiality of developing ovaries in the terrestrial isopod Armadillidium vulgare (Malacostraca, Crustacea)

The androgenic glands (AG) of crustaceans are responsible for differentiation of male sexual characters. The process of gonadal differentiation in females was studied morphologically in Armadillidium vulgare given a masculinizing AG implant. Gonadal masculinization was induced by implantation of an AG into females at various stages of postembryonic development. Functional sex reversal always occurred when an AG was implanted into females that were in stages 5 and 6 of development. Partial formation of testes was induced after implantation of an AG into stage 7 and 8 females. When an AG was implanted into a stage 9 female, development of a functional testis was not observed, but the ovaries were partially masculinized. These results show that after the onset of sex differentiation female gonads retain sexual bipotentiality through several stages of postembryonic development. Implantation of one AG into a female is enough to induce gonadal masculinization and sex reversal in this species. The AG implant up to stage 6 (3.4 mm in body length) is an experimental procedure certain to transform a genetic female into a functional male. The process of gonadal development in female A. vulgare is discussed.