Differentiation and diversification of the follicular cells in flies: Insight from the studies of the lower brachycerans' ovaries

Abstract

Although all dipteran species have ovaries of the same meroistic-polytrophic type, the structure of individual ovarian follicles (egg chambers) as well as the course of oogenesis in major dipteran taxa are highly diversified and often significantly different from the widely known Drosophila model. In this report we present results of the morphological studies of the ovary structure in the representatives of three families of lower brachycerans (Orthorrhapha) and compare them with the present knowledge of the processes that lead to the formation of a mature egg cell in the model dipteran, the cyclorrhaphan fruit fly, Drosophila melanogaster. The most conspicuous and developmentally significant differences between Drosophila and lower brachycerans were found in the events that accompany the differentiation and diversification of somatic follicular cells. Our observations indicate that the directed migrations of some follicular cells within the egg chamber and the ability of border cells to invade the nurse cell compartment can be considered as evolutionary novelties that evolved in the ancestors of higher brachycerans.

Follicular cell differentiation in polytrophic ovaries of a moth midge, Tinearia alternata

“…In contrast, in the egg chambers of lower brachycerans, the border cells migration is facilitated by the progressive degradation of the nurse cell complex. No other translocations of FCs have been described in lower brachycerans (Kubrakiewicz et al, 2003, Tworzydlo et al, 2005. Their FCs neither stretch nor migrate centripetally, but rather maintain their position within the epithelium throughout oogenesis.…”

“…Detailed comparative observations clearly indicate that the major dipteran subgroups may significantly differ in the mode of their FC differentiation. The essential difference relates to the migratory abilities of FCs within the egg chamber (Kubrakiewicz et al, 2003;Kubrakiewicz, 2005, Tworzydlo et al, 2005). The "invasive" migrations, but also extensive planar movements of FCs appeared to be specific only for the representatives of evolutionarily advanced true flies (Cyclorrhapha), including Drosophila.…”

“…In order to gain insight into the evolution of mechanisms of FCs to FCs' differentiation within Brachycera (Kubrakiewicz et al, 2003;Tworzydlo et al, 2005 (Oosterbroek and Courtney, 1995). Within the Nematocera four distinct evolutionary lineages are distinguished: (Tanyderomorpha + Psychodomorpha), Neoneura, Polyneura and Anisoneura (Krzeminski and Krzeminska, 2003).…”

Ovarian Development of House Fly (Musca domestica L.) (Diptera: Muscidae)

“…Investigation of reproductive system of insect female is imperative founded on the point that such organs as the ovary goal to precisely yield several progeny in every generation in the somewhat short life time of adult insects. Previous investigation has been showed to examine the ultrastructure insect ovaries in various species (Cochliomyia hominivora) [17]; the snipe fly(Rhagio lineola) [18]; (Tinearia altemata) [19]; dragon fly [20]; Apis mellifera [21] and Haemato pinssuis [22].…”

OVARIAN ULTRASTRUCTURE AND DEVELOPMENT OF THE BLOW FLY, Chrysomya megacephala (DIPTERA: CALLIPHORIDAE)

“…Prior research has been conducted to investigate the ultrastructure of ovaries in many insects. Species investigated include the blow flies (Diptera: Calliphoridae), Chrysomya bezziana [13], C. megacephala [11], Cochliomyia hominivorax [14], and Calliphora erythrocephala [15]; the decapitating fly Pseudacteon wasmanni (Diptera: Phoridae) [16]; the snipe fly Rhagio lineola (Diptera: Rhagionidae) [17]; the moth midge Tinearia alternata (Diptera: Psychodidae) [18]; the dragonfly Libellula depressa [19]; the honey bee Apis mellifera [20], and the pig louse Haematopinus suis [21]. As for C. megacephala, only photomicrographs of its ovary have already been produced from light microscopy (LM) [11].…”