RESUMO
Development of Pomacea canaliculata from the gastrula stage until the first day after hatching is described. Trochophore embryos are developed after gastrulation, showing the prototroch as a crown of ciliated orange-brownish cells. However, no true veliger embryos are formed, since the prototroch does not fully develop into a velum. Afterward, the connection between the fore- and midgut is permeated and the midgut becomes full of the pink-reddish albumen, which is stored into a central archenteron's lake, from where it is accumulated into the large cells forming the midgut wall ("giant cells"). Electron microscopy of giant cells in late embryos showed that albumen is engulfed by large endocytic vesicles formed between the irregular microvilli at the top of these cells. By the end of intracapsular development, giant cells become gradually replaced by two new epithelial cell types which are similar to those found in the adult midgut gland: the pre-columnar and the pre-pyramidal cells. Pre-columnar cells have inconspicuous basal nuclei and are crowned by stereocilia, between which small endocytic vesicles are formed. Pre-pyramidal cells have large nuclei with 2-3 nucleoli and show a striking development of the rough endoplasmic reticulum. The genesis of the three cell lineages (giant, pre-columnar and pre-pyramidal cells) is hypothetically attributed to epithelial streaks that occur at both sides of the midgut since early stages of development.
Assuntos
Sistema Digestório/embriologia , Gastrópodes/embriologia , Gástrula/embriologia , Organogênese/fisiologia , Animais , Gastrópodes/citologia , Gastrópodes/ultraestrutura , Gástrula/citologiaRESUMO
Development of Pomacea canaliculata from the gastrula stage until the first day after hatching is described. Trochophore embryos are developed after gastrulation, showing the prototroch as a crown of ciliated orange-brownish cells. However, no true veliger embryos are formed, since the prototroch does not fully develop into a velum. Afterward, the connection between the fore- and midgut is permeated and the midgut becomes full of the pink-reddish albumen, which is stored into a central archenterons lake, from where it is accumulated into the large cells forming the midgut wall ("giant cells"). Electron microscopy of giant cells in late embryos showed that albumen is engulfed by large endocytic vesicles formed between the irregular microvilli at the top of these cells. By the end of intracapsular development, giant cells become gradually replaced by two new epithelial cell types which are similar to those found in the adult midgut gland: the pre-columnar and the pre-pyramidal cells. Pre-columnar cells have inconspicuous basal nuclei and are crowned by stereocilia, between which small endocytic vesicles are formed. Pre-pyramidal cells have large nuclei with 2-3 nucleoli and show a striking development of the rough endoplasmic reticulum. The genesis of the three cell lineages (giant, pre-columnar and pre-pyramidal cells) is hypothetically attributed to epithelial streaks that occur at both sides of the midgut since early stages of development.(AU)
Assuntos
Animais , Sistema Digestório/embriologia , Caramujos/citologia , Caramujos/embriologia , Caramujos/ultraestrutura , Gástrula/citologia , Organogênese/fisiologiaRESUMO
Development of Pomacea canaliculata from the gastrula stage until the first day after hatching is described. Trochophore embryos are developed after gastrulation, showing the prototroch as a crown of ciliated orange-brownish cells. However, no true veliger embryos are formed, since the prototroch does not fully develop into a velum. Afterward, the connection between the fore- and midgut is permeated and the midgut becomes full of the pink-reddish albumen, which is stored into a central archenteron's lake, from where it is accumulated into the large cells forming the midgut wall ("giant cells"). Electron microscopy of giant cells in late embryos showed that albumen is engulfed by large endocytic vesicles formed between the irregular microvilli at the top of these cells. By the end of intracapsular development, giant cells become gradually replaced by two new epithelial cell types which are similar to those found in the adult midgut gland: the pre-columnar and the pre-pyramidal cells. Pre-columnar cells have inconspicuous basal nuclei and are crowned by stereocilia, between which small endocytic vesicles are formed. Pre-pyramidal cells have large nuclei with 2-3 nucleoli and show a striking development of the rough endoplasmic reticulum. The genesis of the three cell lineages (giant, pre-columnar and pre-pyramidal cells) is hypothetically attributed to epithelial streaks that occur at both sides of the midgut since early stages of development.
Assuntos
Animais , Caramujos/citologia , Caramujos/embriologia , Caramujos/ultraestrutura , Gástrula/citologia , Organogênese/fisiologia , Sistema Digestório/embriologiaAssuntos
Gastrópodes/anatomia & histologia , Pênis/anatomia & histologia , Pênis/fisiologia , Filogenia , Testículo/anatomia & histologia , Testículo/fisiologia , Animais , Copulação/fisiologia , Masculino , Pênis/citologia , Pênis/inervação , Processos de Determinação Sexual , Diferenciação Sexual , Espermatogênese/fisiologia , Testículo/citologia , Testículo/inervaçãoRESUMO
A new species of cyclopoid copepod, Ozmana huarpium, is described as a symbiont to Pomacea canaliculata (Lamarck 1822) (Caenogastropoda, Ampullariidae). Rather large numbers (about one hundred copepods per snail) were found, although there was no evidence of harm to the host. To our knowledge, O. haemophila (symbiont to P. maculata), and the currently described species, O. huarpium, are the only copepod species ever recorded as endosymbionts to freshwater invertebrates. While O. haemophila is restricted to the haemocoel of its host, O. huarpium predominate in the penis sheath, the ctenidium and the mantle cavity, figuring in these pallial organs 63-65% of total mature forms. The sex ratio of the symbiont is skewed to the female side in these organs, specially in male hosts. The hypothesis that a special female tropism for the male host's pallial organs might ensure interindividual transmission of the symbiont was tested, with indications that the symbiont is mainly transmitted during copulation.
Assuntos
Copépodes/anatomia & histologia , Copépodes/classificação , Copépodes/fisiologia , Caramujos/fisiologia , Simbiose , Animais , Argentina , Feminino , Interações Hospedeiro-Parasita , Masculino , Pênis/parasitologia , Densidade Demográfica , Razão de Masculinidade , Caramujos/parasitologiaRESUMO
A new species of cyclopoid copepod, Ozmana huarpium, is described as a symbiont to Pomacea canaliculata (Lamarck 1822) (Caenogastropoda, Ampullariidae). Rather large numbers (about one hundred copepods per snail) were found, although there was no evidence of harm to the host. To our knowledge, O. haemophila (symbiont to P. maculata), and the currently described species, O. huarpium, are the only copepod species ever recorded as endosymbionts to freshwater invertebrates. While O. haemophila is restricted to the haemocoel of its host, O. huarpium predominate in the penis sheath, the ctenidium and the mantle cavity, figuring in these pallial organs 63-65
of total mature forms. The sex ratio of the symbiont is skewed to the female side in these organs, specially in male hosts. The hypothesis that a special female tropism for the male hosts pallial organs might ensure interindividual transmission of the symbiont was tested, with indications that the symbiont is mainly transmitted during copulation.
Assuntos
Animais , Caramujos , Sistema Digestório , Especificidade da Espécie , Microscopia Eletrônica , Nitrogênio/metabolismo , Caramujos , SimbioseRESUMO
As the corn mouse, Calomys musculinus, has a short luteal phase (2-3 days) that is not prolonged after copulation, it was hypothesized that (i) implantation would occur at the end of this phase, that is, earlier than it occurs in most murid species that have been studied, and (ii) a lactational embryonic diapause would not occur during the luteal phase. These hypotheses were tested in females that had copulated during postpartum oestrus and were either lactating or not lactating. Data were recorded from day 3 to day 5 of pregnancy (day 1 = day after coitus), at both 03:00-05:00 h and 17:00-19:00 h. Evidence of implantation in both non-lactating and lactating animals was apparent at 03:00-05:00 h on day 4 (endometrial 'blue reaction' in all cases and failure to recover free uterine embryos in some cases) and implantation swellings appeared within 24 h in both groups. In another experiment, the increase in duration of interbirth intervals in continuously mated females and their correlation with the number of suckling young were compared among C. musculinus, C. laucha, Akodon molinae (South American murid species) and Peromyscus maniculatus (a North American murid in which a lactational embryonic diapause has been shown). The results were indicative of a lactational embryonic diapause in the North American species, but not in the South American species. It was concluded that in C. musculinus (i) implantation occurs at the end of the spontaneous luteal phase, and (ii) that a lactational embryonic diapause does not occur: the absence of a lactational embryonic diapause may be common to other South American murid rodents.
Assuntos
Implantação do Embrião , Lactação , Fase Luteal , Muridae/fisiologia , Animais , Copulação , Estro , Feminino , Idade Gestacional , Masculino , Período Pós-Parto , Gravidez , América do Sul , Especificidade da Espécie , Fatores de TempoRESUMO
Most Muridae display a short luteal phase that becomes functional as a consequence of the prolactin release induced by the stimulation of copulation and/or lactation. The corn mouse also shows a short luteal phase, and we wanted to know whether copulation and/or lactation would release prolactin and maintain progesterone secretion in this species. Females in postpartum estrus were either allowed to copulate with an intact male or not, and either to lactate their young or not. Afterward, plasma progesterone was elevated over the baseline level only in females that had copulated and were bearing growing embryos (whether or not they were lactating), while prolactin was elevated only in lactating females. In another experiment, endometrial scratching induced decidualization both in females that had copulated with a vasectomized male and in those that had not copulated; sham operations had no effect in either case. Progesterone levels were elevated in decidualized animals as compared with their sham-operated controls. Results indicate that the initiation of the progestational phase in the corn mouse is not dependent on prolactin release. A short luteal phase during which nidation may occur has not yet been described in any other mammal.
Assuntos
Estro/fisiologia , Muridae/fisiologia , Animais , Copulação/fisiologia , Decídua/fisiologia , Estradiol/sangue , Feminino , Masculino , Tamanho do Órgão/fisiologia , Gravidez , Progesterona/sangue , Prolactina/sangue , Radioimunoensaio , VasectomiaRESUMO
Two sets of behaviors relevant for the construction of shelters, nest building and digging, were studied in three con-generic species of South American cricetid rodents. Significant differences were observed among the three species in both sets of behaviors, but not between sexes within the same species. Calomys musculinus built the largest nests, C. laucha showed the highest number of digging bouts and the shortest digging latency, and C. venustus scored low in both nesting and digging behaviors. In general, these observations are consistent with the few, anecdotal records of the shelters used by these species in the field. The low nesting and digging scores of C. venustus are correlated with that species' low thermal conductance, but the marked differences in the nesting and digging scores of C. musculinus and C. laucha cannot be accounted for by differences in their basal metabolic rates or thermal conductances.
Assuntos
Arvicolinae/psicologia , Atividade Motora , Comportamento de Nidação , Comportamento Estereotipado , Animais , Argentina , Feminino , Masculino , Meio Social , Especificidade da EspécieRESUMO
We describe the copulatory behavior and the morphology of the male genital tract of a member of a tribe (Akodontini) for which no information on copulatory behavior has been available. Copulation in Akodon molinae is characterized by multiple intromissions with no intravaginal thrusting, a single ejaculation, and a brief lock with the deposit of a plug. This pattern is unusual because of the combination of locking with both multiple intromissions and plugs. The latter combination, and similar standard measures of copulatory behavior, have been reported for Acomys cahirinus, a murid that frequently shows more than 1 ejaculation. Also, the standard measures of copulation in A. molinae resemble those of Calomys callosus, another South American cricetid, which shows intravaginal thrusting and infrequent locks. The functional significance and the anatomical correlates of locking and plug deposition in this species are discussed.