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Biomedical subjects

J J Gilbert

Publications and source records attributed to J J Gilbert.

At least 91 records · Page 5Linked to original sources
PubMed1976

Sex-specific cannibalism in the rotifer Asplanchna sieboldi.

In one clone, large-morphotype females rarely exhibit tactile feeding responses to their ingestible, male clonemates but readily attack small-morphotype female clonemates and males of another, taxonomically distinct, clone. In the latter clone, cannibal females lack such selectivity, but their males are well protected from capture by very large, lateral body-wall outgrowths.

Animals↗
PubMed1976

Polymorphism in the rotifer Asplanchna sieboldi. Fine structure of saccate, cruciform and campanulate females.

The morphology of saccate, cruciform, and campanulate females of Asplanchna sieboldi was analyzed by light and electron microscopy. No major qualitative variations were observed in the ultrastructure of the hypodermis, gastric gland and yolk gland of females from the different morphotypes. Campanulate females did, however, possess larger secretory granules in their gastric gland as well as larger and more numerous nuclei in their gastric and yolk glands than both saccate and cruciform females. The structure of the secretory elements in the gastric gland varied between the two clones investigated.

Animals↗
PubMed1976

Sex reversal in a freshwater sponge.

Spongilla lacustris exhibits a type of alternative hermaphroditism, new to the phylum, in which a sponge may be exclusively male or female during the period of sexual reproduction one year and the opposite sex the next year. This form of sexuality may facilitate larva production and thus dispersal following colonization of a new habitat. Gametogenesis occurs shortly after gemmule hatching in both males and females but slightly later in males.

Animals↗
PubMed1976

Selective cannibalism in the rotifer asplanchna sieboldi: contact recognition of morphotype and clone.

Populations of A. sieboldi reproduce primarily by diploid femal parthenogenesis. Females may exhibit a pronounced, nongenetic polymorphism which is controlled by the diet. The cruciform and especially the campanulate morphotypes are larger than the saccate morphotype and are cannibalistic. Direct observations of various predator-prey interactions between the different morphotypes of two taxonomically distinct clones show that the feeding responses of cannibals after actual prey contact are predictable and extremely selective. Companulates from clone B respond regularly to saccate but only rarely to cruciform or campanulate clonemates; the same predators typically respond to cruciforms and campanulates from clone C. Cruciforms from clone C rarely respond to saccate and cruciform clonemates but readily attack all morphotypes from clone B. In contrast, campanulates from clone C show no selectivity. Morphotype- and clone-specific recognition responses, which are mediated by coronal contact chemoreceptors, permit efficient prey discrimination and protection withotu involving prey handling or development of energy-demanding, defensive structures, such as the body-wall outgrowths of the cruciform morphotype. Selective feeding of cannibals may increase the fitness of a clone, both by effecting a more adaptive distribution of its morphotypes and by enhancing its ability to compete directly and indirectly with cooccurring clones. The magnitude of cannibalism in this rotifer may be dependent upon a complex suite of heterogeneous predator-prey interactions and greatly affected by shifting densities and distributions of different clones and female morphotypes.

Age Factors↗
PubMed1975

Dietary tocopherol and sexual reproduction in the rotifers Brachionus calyciflorus and Asplanchna sieboldi.

Brachionus calyciflorus contained no detectable tocopherol (vitamin E) when cultured for long periods on the yeast Rhodotorula glutinis. Using a spectrofluorometric assay and the Asplanchna body-wall-outgrowth response bioassay the limits of detection were 6.4 ng and 3.78 pg alpha-tocopherol per g dry weight Brachionus, respectively. These tocopherol-free Brachionus reproduced normally both parthenogenetically and sexually, producing active and potent males and fertilized resting eggs which developed into viable young rotifers. The apparent lack of a tocopherol requirement for male fertility in B. calyciflorus probably also applies to Asplanchna sieboldi and A. brightwell -- rotifers whose male-producing (mictic) females are induced by dietary tocopherol and whose males therefore are never tocopherol-deficient. The adaptive significance of the tocopherol requirement for the initiation of sexual reproduction in Asplanchna sieboldi--formerly hypothesized to be the result of a tocopherol requirement for male fertility--is now thought to be related to the role of tocopherol in controlling female polymorphism in this species.

Animals↗