Isolation of polymorphic tetranucleotide microsatellite markers for the ornate nursery frog Cophixalus ornatus

We have isolated 18 polymorphic microsatellite loci for Cophixalus ornatus from genomic libraries enriched for (AAAG)_n, (AACC)_n and (AAGG)_n repetitive elements. The number of alleles ranges from five to 22 per locus with the observed heterozygosity ranging from 0.10 to 0.92. These markers will be useful for the analysis of population structure in C. ornatus and testing alternative models of speciation.     

Elektronenmikroskopische Untersuchungen an der Froschlunge

Zusammenfassung Das Alveolarepithel der Froschlunge weist nur einen einzigen Zelltyp auf. Die Zellkörper sitzen in den Nischen zwischen den Kapillaren, die sie mit Zytoplasmaausläufern überdecken. Die Epithelzellen enthalten große Zytosomen mit osmiophilen Lamellen mit einer Periode von 40–42 Å. Sie sind den Typ II-Pneumozyten der Säugerlunge vergleichbar.Das Alveolarepithel der Froschlunge ist mit einer Grenzschicht bedeckt, die in Abhängigkeit von der Fixierung eine 40–42 Å-Periode aufweist oder aus einer oder mehreren Doppelmembranen zusammengesetzt ist. Gittermuster und Myelinfiguren sind vorhanden. Das bedeutet, daß Surfactant in der Froschlunge in gleicher Weise wie in der Säugerlunge dargestellt werden kann.

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Electron microscopic studies on the lung of the frogI. Demonstration of the alveolar lining layer (surfactant)

Summary The alveolar epithelium of the frog exhibits only one type of cells. The cell-bodies are situated in the spaces among the capillaries, which they cover with cytoplasmic extensions. The epithelial cells contain large bodies (cytosomes) with osmiophilic lamellae having a period of 40–42 Å. The alveolar cells are considered to be similar to the type II-pneumocytes of mammalian lungs.The alveolar epithelium of the lung of the frog is covered with a lining layer, which depending on the method of fixation consists of periods of 40–42 Å or of one or more double membranes. Lattice formations and myelin figures are seen. This means that the surfactant in the lung of the frog can be demonstrated in the same way as in mammalian lungs.

     

An electron microscopic study of stellate cells and cavities in the pars distalis of frog pituitary

Stellate cells in the pars distalis of adult Rana ridibunda were observed electron microscopically under normal and experimental conditions (TRH injection). The stellate cells have lengthy processes extending into the intercellular spaces between the secretory cells and scanty cytoplasm surrounding the nucleus. Occasional desmosomes link stellate cells to adjacent secretory cells. In the pars distalis of animals injected with thyrotropic-releasing hormone (TRH), the stellate cells form large cavities (2-6 mum) filled with heterogeneous material. Their cytoplasm contains well-developed Golgi complexes and some lysosomes; these are the principal morphological alterations as compared to those observed in control animals. It is suggested that stellate cells could play an active role in addition to providing a structural framework for the pars distalis.     

Toe pad morphology and mechanisms of sticking in frogs

Sticking ability in frogs was measured on a series of different substrates. Analysis of performance suggests that frogs use two sticking mechanisms: interlocking on rough surfaces and capillarity on smooth surfaces. There is a correlation between morphological specializations of the toe pad and sticking ability, but these morphological features are not unique to arboreal species. Terrestrial species that use leaves as resting sites during times of inactivity have many of the same morphological specializations and stick as well as the strictly arboreal species.     

Patterns of parental care in Neotropical glassfrogs: fieldwork alters hypotheses of sex‐role evolution

Many animals provide parental care to offspring. Parental sex‐roles vary extensively across taxa, and such patterns are considered well documented. However, information on amphibians is lacking relative to other vertebrate groups. We combine natural history observations with functional and historical analyses to examine the evolution of egg care in glassfrogs (Centrolenidae). Parental care was considered rare and predominately provided by males. Our field observations of 40 species revealed that care occurs throughout the family, and the caregiving sex changes across lineages. We discovered that a brief period of maternal care is widespread and occurs in species previously thought to lack care. Using a combination of female‐removal experiments, prey‐choice tests with egg‐eating katydids, and parental disturbance‐tolerance assays, we confirm the adaptive benefits of short‐term maternal care in wild Cochranella granulosa and Teratohyla pulverata. To examine historical transitions between caregiving sexes, we assembled a molecular phylogeny and estimated ancestral care states using our data and the literature. We assessed patterns indicative of sex‐specific constraints by testing whether transitions between the sexes are associated with changes in care levels. Our analyses support that male‐only care evolved 2–3 times from female‐only care, and this change is associated with substantial increases in care levels – a pattern supporting the hypothesis that male‐only care evolved via constraints on maternal expenditure. Many groups of amphibians remain poorly studied, with emerging evidence indicating that care patterns are more diverse than currently appreciated. Natural history remains fundamental to uncovering this diversity and generating testable hypotheses of sex‐role evolution.     

Oviduct histochemistry and site of synthesis of a 29.7 kDa jelly coat glycoprotein in the anuran Lepidobatrachus laevis

The oviduct of the anuran Lepidobatrachus laevis contains three morphological regions, each of which contains a histochemically distinct luminal mucosa. In the pars recta, the most anterior portion of the oviduct, there are periodic acid-Schiff base (PAS)-positive simple glands and epithelia. In the pars convoluta, there are alcian blue-positive, combined alcian blue- and PAS-positive and PAS-positive gland types. The most posterior region, the pars uterina, contains alcian blue-positive and alcian blue-negative epithelial cells. Previous work has shown that solubilized egg jelly contains a major 29.7 kDa glycoprotein subunit that was detected in oviduct tissue extracts from the pars convoluta in the present study. Rabbit antisera to the 29.7 kDa egg jelly glycoprotein of L. laevis reacted with the major pars convoluta glycoprotein and there were no immunoreactive components in the pars uterina. The slight immunoreactivity detected at 29.0–37.0 kDa in pars recta extracts is not believed to be the jelly molecule, based on low immunoreactivity and subunit molecular weight measurements. We conclude that the synthesis of the 29.7 kDa egg jelly glycoprotein is restricted to the pars convoluta region of the oviduct.     

Single-file diffusion through K+ channels in frog skin epithelium

Summary The ratio between the unidirectional fluxes of K⁺ across the frog skin with K-permeable outer membranes was determined in the absence of Na⁺ in the apical solutions. The experiments were performed under presteady-state conditions to be able to separate the flux ratio for K⁺ through the cells from contributions to the fluxes through extracellular leaks. The cellular flux ratio deviated strongly from the value calculated from the flux ratio for electrodiffusion. The experiments can be explained if the passive K transport through the epithelial cells proceeds through specific channels by single-file diffusion with a flux ratio exponent of about 2.5.