M. Nokhbatolfoghahai

The surface ciliation of anuran amphibian embryos and early larvae: Patterns, timing differences and functions

Embryonic and early larval surface ciliation patterns are described stage by stage, using scanning electron microscopy and live specimen observations, in 20 species of anuran amphibians from six families including the first detailed description of surface ciliation in a direct‐developing eleutherodactylid: four species are from temperate regions and 16 are tropical. The study asks whether differences in pattern relate to ciliation functions, or show any phylogenetic features, or demonstrate heterochrony. It also asks whether the timing of ciliated cell regression is fixed or can vary with the environment. Respiration appears to be the main function of surface ciliation, both pre‐ and post‐hatching, regressing when internal gills become functional. Substratum gliding after hatching may also be a valuable role. Late stage persistence of ciliation around the external nares suggests a sensory function. Localized early regression of ciliated cells is linked to lateral line development. Dramatic changes in ciliated cell shape are described, though functions are unclear. Ciliation patterns, density and duration vary considerably between species, with no obvious phylogenetic or environmental correlates, nor is there a clear relationship with egg size or hatching stage. Ciliation patterns also vary with body region, with density and duration consistently highest round the nostrils and adhesive glands (when present) compared to other body regions.

The external gills of anuran amphibians: Comparative morphology and ultrastructure

The external gills of anuran amphibians are transient structures, covered by the development of the operculum and regressing soon afterwards. Their functional role has been regarded as equivocal. However, detailed morphological analysis has been limited. Analysis of 21 species from six families using scanning and transmission electron microscopy revealed diversity at the anatomical and cellular levels in extent and length of gill filaments, numbers of surface ciliated cells, width of water‐blood barrier distance, and evidence of gill motility. The most highly developed external gills were found in species with delayed hatching, such as Phyllomedusa trinitatis, or in species in which hatchlings hang from the surface film of temporary ponds, such as Phrynohyas venulosa in which gills added 26–38% to body surface area. In one family, the bufonids, all four species examined had poorly developed gills, but in other families where we examined several species, the hylids and leptodactylids, there was considerable diversity of external gills, suggesting flexible adaptation to incubation and hatching environment. J. Morphol., 2008.

First scientific record of two cases of partial twinning in the chick embryo, Gallus gallus domesticus

Bicephalia is one of the scarcest malformations reported in birds and needs to be fully investigated in chick embryos. Among 1500 fertilised eggs used to examine the primordial germ cells in 2-day and 5.5-day chick embryos Gallus gallus domesticus, bicephalia was found and the condition of the heads, the heart and other parts of the body was fully described. Each twin had its own head; hearts were not completely separated from each other and the rest of the bodies were externally unique. This investigation urges others including poultry farms to share their data on a bigger scale. It may also encourage the monitoring of abnormalities randomly seen during early chick embryogenesis and consideration of environmental factors when poultry farms are faced with high percentages of unsuccessful hatching. The report can shed some light on developmental processes and may also help to clarify why bicephalia is not more common.