Variability of the female genital system morphology and of sperm storage in terrestrial isopods (Isopoda, Oniscidea)

Abstract

In females of Isopoda Oniscidea, the genital system displays a remarkable variability of its morphological and functional organization as possible adaptation to different strategies of sperm storage. In all the oniscidean species, the sperm received from the male during mating are temporarily stored in the bursa copulatrix, a chitinous pouch of the oviduct. In 27 of the 32 species we studied, the sperm that remain in the bursa copulatrix after the fertilization of eggs of the first oviposition are transferred into the seminal receptacle, where they can be stored for a variable time. In these species, the seminal receptacle is a small kidney-shaped cup, localized at the insertion of the oviduct into the ovary. Only in two species of the genus Trichoniscus, in which the oviduct is very short, is the bursa copulatrix modified to form a large lateral diverticle.Instead, in three species of the family Halophilosciidae, Halophiloscia couchii, Halophiloscia hirsuta and Stenophiloscia glarearum, the ovary is consistently shorter, while the seminal receptacle is greater; after mating, both seminal receptacle and ovary appear completely filled with sperm. Finally, in two species of the family Tylidae, Tylos europaeus and Helleria brevicornis, the female genital system lacks specialized structures for sperm storage, and every oviposition requires a mating for the eggs fertilization.The authors present some hypotheses to explain the variability of the female genital system morphology and the sperm storage strategies.

Egg envelopes ofArmadillidium vulgare(Latreille, 1804) (Crustacea, Isopoda Oniscidea): Ultrastructure and lectins binding

“…The female genital system of the oniscidean isopods has been the object of numerous researches (Besse, ; De Luca et al, ; Legrand and Vandel, ; Longo and Trovato, ; Longo et al, ; Mazzei et al, ; Suzuki and Ziegler, ; Vandel, ; Warburg, ; Wägele ).…”

“…For the evaluation of the general characteristics of the female genital system some sexually mature and mated females were killed by decapitation and dissected in Ringer's saline solution modified for land isopods according to Legrand (Besse, ). The female genital system, after removal, was observed and photographed with the aid of a stereo‐microscope Wild M400, both fresh and after a brief fixation in 2.5% glutaraldehyde in 0.1 M phosphate buffer, pH 7.3; some specimens were in toto stained with Sudan black B (saturated solution in isopropyl alcohol) method that, as demonstrated in previous papers, clearly highlights the general organization of female genital system (Longo et al, ).…”

“…Ultrastructural Observations The female genital system of the oniscidean isopods has been the object of numerous researches (Besse, 1976;De Luca et al, 1987;Legrand and Vandel, 1948;Longo and Trovato, 2008;Longo et al, 1998Longo et al, , 2011Mazzei et al, 2014;Ziegler, 2005, 2014;Vandel, 1925;Warburg, 2012;W€ agele 1992).…”

Testis follicles ultrastructure of three species of terrestrial isopods (Crustacea, Isopoda Oniscidea)

“…In all the three species examined the male genital apparatus is characterized by a basic morphological organization similar to that described for other species of terrestrial isopods (Vandel, 1925;Becker and Mann, 1938;Wägele, 1992); some degree of variability concerns only the location of the testis follicle on the cranial extremity of the seminal vesicle, that in T. alexandrae are inserted closely near to each other, and the genital tract that in H. hirsuta is longer so as to allow a greater accumulation of spermatozoa to be transferred with the mating inside the seminal receptacle female (Longo et al, 2011). The testis follicles are spindle-shaped but their size and their morphology varies notably according to the phase of spermatogenesis that in each of the three follicles is realized in a chronologically scalar mode.…”

Systematic and palaeoecological significance of the first record of Pygocephalomorpha females bearing oöstegites (Malacostraca, Peracarida) from the lower Permian of southern Brazil

“…Whilst some female isopods have both oöstegites and seminal receptacles (Longo et al . ), the latter are microscopic and would hardly preserve in fossils. Schram () suggested that the large opening on the eighth thoracic segment is a male genital cone, akin to that seen in the Order Tanaidacea (Peracarida); we agree.…”