Morphological aspects of cell reabsorption in laying queens and workers of Apis mellifera (Hymenoptera, Apidae)

Abstract

ABSTRACT. The occurrence of cell reabsorption in the ovaries of queens in several rates of laying eggs, artificially impeded of laying, and in nurse workers, of Apis mellifera (Linnaeus, 1758), was studied with light (LM) and transmission electron microscopy (TEM). Two types of structures were described and named by analogy with vertebrates ovarian structures, as corpus luteus, when resulting from the reabsorption of the follicular cells after ovulation, and corpus atresicus when resulting from total follicular reabsorption at any oocyte developmental stage. These structures have the same morphological characteristics and physiological signification in both castes. The corpus luteus occurrence indicates ovulation and its number is correspondent to the queen's rates of oviposition. The presence of this structure in nurse workers ovarioles shows that this caste may lay eggs. The incidence of corpus atresicus in queens decay with the increasing of the oviposition indicating that the inhibition of the normal sequence of oocyte maturation in the ovaries is deleterious. Both, corpus luteus and corpus atresicus incidence may be influenced by environmental factors. KEYWORDS. corpus luteus, corpus atresicus, oviposition, histology, ultrastructure.RESUMO. Aspectos morfológicos da reabsorção celular em rainhas em postura e operárias de Apis mellifera (Hymenoptera, Apidae). A ocorrência de reabsorção celular nos ovários de Apis mellifera (Linnaeus, 1758) foi estudada em operárias, em rainhas artificialmente impedidas de se acasalarem e em rainhas em postura utilizando microscopia de luz (LM) e eletrônica de transmissão (MET). São descritos dois tipos de estruturas morfológicas, indicativas da ocorrência de reabsorção. Estas estruturas foram denominadas por analogia com estruturas correspondentes presentes nos ovários dos vertebrados. As resultantes de reabsorção das células foliculares depois da ovulação foram denominadas corpos lúteos e as resultantes da reabsorção de todo o folículo, em qualquer fase do desenvolvimento do ovócito, de corpos atrésicos. As estruturas representativas da reabsorção têm as mesmas características morfológicas e significado fisiológico em ambas as castas. A presença de corpo lúteo indica prévia ovulação e seu número corresponde à taxa de postura da rainha e sua presença nas operárias nutridoras mostra que esta casta pode por ovos nesta fase. A incidência de corpos atrésicos em rainhas diminue com o aumento da taxa de postura indicando que a inibição da sequência normal de maturação de ovócitos no ovário é deletéria. Tanto a incidência do corpo lúteo, como do corpo atrésico pode ser influenciada por fatores ambientais.

Histomorphological description of the reproductive system in mated honey bee queens

“…Within each follicle, the trophocytes (nurse cells) (Figure 3A-4) are attached by intercellular bridges and connected to the oocyte by the trophic stalk (a narrow opening) (Figure 3A-3) which allows the transport of nutrients, RNA, and ribonucleoproteins from the trophocytes to the ovum during maturation (Figure 3A-1) as described in previous studies (Berger & da Cruz-Landim, 2009;Bili nski & Jaglarz, 1999;Cruz-Landim & Patr ıcio, 2010;Snodgrass, 1985;Tanaka et al, 2006). After transferring their cytoplasmic contents to the developing ovum, the trophocytes undergo programmed cell death (apoptosis) (Figure 3A-7) as found in earlier studies (Mpakou et al, 2006;Patr ıcio & Cruz-Landim, 2008). Thus, the oocytes in the proximal vitellarium are small, followed by an organized cluster of trophocytes (Figure 3A circle), whereas the oocytes in the distal vitellarium are greater in size, followed by apoptotic/degenerating trophocytes (Figure 3A-7), as described by Snodgrass, 1985.…”

“…The ovaries are composed of ovarioles divided into four regions (i.e. terminal filament, germarium, vitellarium, and ovariole pedicle) based on morphological differentiation (Patr ıcio & Cruz- Landim, 2002Landim, , 2008. The stem cells (terminal filament) differentiate into germinal cells forming rosette-like clusters (germarium); subsequently, each rosette produces a single oocyte and accompanying trophocytes which together comprise a follicle (vitellarium) (Martins et al, 2011;Patr ıcio & Cruz-Landim, 2002Snodgrass, 1985;Tanaka & Hartfelder, 2004), as illustrated in the present study (Figure 2A-C).…”

Effect of Cadmium on Worker Ovary Morphology of Bombus morio (Hymenoptera: Bombini)

“…1A-E). Although not shown in the present work, follicular abortion and the corpus luteum were also observed, which is a normal condition in the ovarian development of this and other species of bees; this morphology is found mainly in queens but can also be observed in egg-laying workers Patrício and Cruz-Landim, 2008;Tanaka et al, 2009).…”

Viruses Associated with Ovarian Degeneration in Apis mellifera L. Queens

“…In our study, such cellular death patterns were evidenced by propidium iodide staining, both in the terminal filament and in the germinal part of the ovary ( Figure 1D and 1E ) but, according to their large distribution in tissues, may rather result from a pathological problem. Programmed cellular death seems also to be involved in oocyte resorption when environmental conditions are limiting the egg production of the queens [35] . However, the samples examined here were collected in spring during the warm season and consequently should not normally correspond to such environmentally induced oocyte resorption.…”