The midgut epithelium of bees is formed by the digestive cells, responsible for enzyme secretion and nutrient absorption and for small regenerative cells that are placed in nests scattered among the digestive cells. During metamorphosis, the larval midgut epithelium degenerates and a new adult midgut epithelium is built during larval differentiation of regenerative cells. The present work focuses on the midgut epithelial modifications during the post-embryonic development of the stingless bee Melipona quadrifasciata anthidioides worker and the occurrence of regenerative cell proliferation during midgut metamorphosis in order to test the hypothesis that adult midgut epithelium of worker bees results from regenerative cell proliferation during the pupal stage. Regenerative cell proliferation was detected during larval lifespan. Larval aging is followed by an increase in the number and the size of the nests of regenerative cells. Larval epithelium degeneration begins 2 days after the start of defecation process and in this period the nests of regenerative cells are in contact by means of cytoplasmic extension which have many septate desmosomes and gap junctions. The BrdU immunoreactive regenerative cells were found in the prepupae 12 h after BrdU injection, suggesting that regenerative cell population increase during this larval period. Regenerative cell proliferation results in the increase of the regenerative cell population and not in the formation of new digestive cells because the proliferation of regenerative cells would not be enough to reestablish the nests of regenerative cells and at the same time form new adult digestive cells. In this sense the hypothesis that digestive adult cells originate from regenerative cell proliferation during midgut metamorphosis in M. quadrifasciata anthidioides was rejected.

-The objective of this work was to study the morphologic development and the swimming and feeding behaviors of piracanjuba larvae, Brycon orbignyanus Valenciennes (1849) (Characiformes, Characidae, Bryconinae), during the period from zero to 172 hours after hatching (standard length = 3.62 -11.94 mm). The morphological analyses were accomplished by using a trinocular stereo microscope, while the behavioral analyses were performed through periodic observations. In 28 hours after hatching, the larvae (standard length = 6.25 ± 0.13 mm) showed the following structural and behavioral characteristics that made them become active predators able to overcome a larval critical phase, the beginning of exogenous feeding: presence of pigmented eyes, terminal and wide mouth, developed oral dentition, developing digestive tube, yolk sac reduction, fins and swim bladder formation, horizontal swimming, cannibalism, and predation.Intense cannibalism among larvae was verified from 26 to 72 hours. At the end of the metamorphosis -172 hours after hatching -the larvae measuring 11.94 + 0.80 mm in standard length presented a flexed notochord, caudal fin bifurcation, dorsal and anal fin formation, synchronized movements, and formation of shoals, characteristics that together allow enhanced perception and locomotio in exploration of the environment, determining the best moment for transfering to the fishponds. New studies can contribute to commercial fish farming by improving feeding management, performance, survival, and productivity of this species.Key Words: behavior, Brycon orbignyanus, Characiformes, first feeding, morphology, ontogenyDesenvolvimento morfológico e comportamental de larvas de piracanjuba RESUMO -Objetivou-se estudar o desenvolvimento morfológico e os comportamentos natatório e alimentar de larvas de piracanjuba, Brycon orbignyanus Valenciennes (1849) (Characiformes, Characidae, Bryconinae) no período de 0 a 172 horas após a eclosão (comprimento-padrão = 3,62 -11,94 mm). As análises morfológicas foram realizadas com auxílio de um microscópio estereoscópico trinocular e as comportamentais, por meio de observações periódicas. Com 28 horas após a eclosão, as larvas (6,25 ± 0,13 mm) apresentaram características estruturais e comportamentais que as tornavam predadoras ativas, capazes de superar a etapa crítica da fase larval, o início da alimentação exógena: presença de olhos pigmentados, boca terminal e ampla, dentes desenvolvidos, tubo digestivo em desenvolvimento, saco vitelino em redução, nadadeiras e bexiga gasosa em formação, nado horizontal, canibalismo e predação. Canibalismo intenso entre as larvas foi verificado das 26 às 72 horas. No final da metamorfose, às 172 horas pós-eclosão, medindo 11, 94 + 0,80 mm de comprimento padrão, as larvas apresentaram notocorda flexionada, nadadeira caudal em bifurcação e nadadeiras dorsal e anal em formação, movimentos sincronizados e formação de cardumes, características que, em conjunto, permitem melhor percepção e locomoção na exploração do ambiente e determinam o m...

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Brontocoris tabidus (Signoret) (Heteroptera: Pentatomidae) is an obligate zoophytophagous predator because its population can be maintained in the laboratory when fed on both prey and plants. We evaluated ultrastructural changes in the midgut digestive cells of adult B. tabidus, subjected to different treatments (starvation or feeding on plant material and prey) for different periods. Their midguts were dissected, divided into anterior, medium and posterior sections, processed, and analyzed with light and transmission electron microscopy. The anterior region of the midgut of B. tabidus, starved or fed on eucalyptus leaves, contained no glycogen. B. tabidus fed on plant material showed multivesicular bodies in this region, and spherocrystals after 6 h of feeding on prey. The microvilli of the medium midgut were longer than those of the anterior and posterior midgut. The posterior midgut differed from the other two regions by an abundance of mitochondria, rough endoplasmatic reticulum and double membrane vesicles in the apical region, 6 h after feeding. The ultrastructural features of the digestive cells in the anterior, medium and posterior regions of the midgut suggest that they play a role in digestive enzyme synthesis, ion and nutrient absorption, and storage and excretion of substances.

The Aedes aegypti midgut is restructured during metamorphosis; its epithelium is renewed by replacing the digestive and endocrine cells through stem or regenerative cell differentiation. Shortly after pupation (white pupae) begins, the larval digestive cells are histolized and show signs of degeneration, such as autophagic vacuoles and disintegrating microvilli. Simultaneously, differentiating cells derived from larval stem cells form an electron-dense layer that is visible 24h after pupation begins. Forty-eight hours after pupation onset, the differentiating cells yield an electron-lucent cytoplasm rich in microvilli and organelles. Dividing stem cells were observed in the fourth instar larvae and during the first 24h of pupation, which suggests that stem cells proliferate at the end of the larval period and during pupation. This study discusses various aspects of the changes during midgut remodeling for pupating A. aegypti.