Morphogenesis of the ovarian follicular epithelium during initial stages of embryogenesis of the viviparous earwig, Hemimerus talpoides

Abstract

Representatives of the highly specialized earwig family Hemimeridae are epizoic and viviparous. Their embryos develop inside terminal ovarian follicles (termed also embryonic follicles) and rely solely on nutrients transferred from mother tissues. In this report, we present results of ultrastructural and histochemical studies of the initial stage of Hemimerus talpoides development. Our results show that the follicular cells surrounding fully grown oocyte of Hemimerus do not degenerate after initiation of embryogenesis, but transform and gradually form the wall of the incubation chamber in which the embryo develops. We also show that amniotic cells of the early embryo remain in direct contact with transformed follicular cells. In the region of contact, short outgrowths of the amniotic cells associate with irregular surface specializations of the transformed follicular cells. We suggest that extended “postfertilization” activity of hemimerid follicular cells represents an adaptation to viviparity and matrotrophy in this insect lineage.

Adaptations for matrotrophy in the female reproductive system in the pseudoscorpion Chelifer cancroides (Chelicerata: Pseudoscorpiones, Cheliferidae)

“…For example, in basal groups of scorpions (referred to as apoikogenic type) the nutrients originate from hemolymph (Farley, 1998), while in advanced scorpions (katoikogenic type) they come from the hepatopancreas (Farley, 1999;Mathew, 1956;Polis & Sissom, 1990). Placenta-like organs provide nutritive material in apoikogenic scorpions from the family Vaejovidae (Farley, 1996(Farley, , 1998 and hemimerid insects (Bilinski, Sekula, & Tworzydlo, 2020). In turn, in pseudoscorpions, production of the nutritive fluid occurs in the female reproductive system.…”

Spectacular alterations in the female reproductive system during the ovarian cycle and adaptations for matrotrophy in chernetid pseudoscorpions (Pseudoscorpiones: Chernetidae)

“…In arthropods lecithotrophy predominates, however, the occurrence of extraembryonic nutrition has been evidenced in both subphyla, that is, Mandibulata (Myriapoda and Pancrustacea) and Chelicerata. In the former group, matrotrophy occurs in several insect orders, e.g., Dermaptera, Strepsiptera, Diptera, and some crustaceans e.g., Isopoda and Decapoda 1 , 6 – 9 . In extant chelicerates, matrotrophy has been described in pseudoscorpions and scorpions, and 2 genera of mites 10 , 11 .…”