When toads (Rhinella) are threatened they inflate their lungs and tilt the body towards the predator, exposing their parotoid macroglands. Venom discharge, however, needs a mechanical pressure onto the parotoids exerted by the bite of the predator. The structure of Rhinella jimi parotoids was described before and after manual compression onto the macroglands mimicking a predator attack. Parotoids are formed by honeycomb-like collagenous alveoli. Each alveolus contains a syncytial gland enveloped by a myoepithelium and is provided with a duct surrounded by differentiated glands. The epithelium lining the duct is very thick and practically obstructs the ductal lumen, leaving only a narrow slit in the centre. After mechanical compression the venom is expelled as a thin jet and the venom glands are entirely emptied. The force applied by a bite of a potential predator may increase alveolar pressure, forcing the venom to be expelled as a thin jet through the narrow ductal slit. We suggest that the mechanism for venom discharge within all bufonids is possibly similar to that described herein for Rhinella jimi and that parotoids should be considered as cutaneous organs separate from the rest of the skin specially evolved for an efficient passive defence.

Although the initial growth and development of most multicellular animals depends on the provision of yolk, there are many varied contrivances by which animals provide additional or alternative investment in their offspring. Providing offspring with additional nutrition should be favoured by natural selection when the consequent increased fitness of the young offsets any corresponding reduction in fecundity. Alternative forms of nutrition may allow parents to delay and potentially redirect their investment. Here we report a remarkable form of parental care and mechanism of parent-offspring nutrient transfer in a caecilian amphibian. Boulengerula taitanus is a direct-developing, oviparous caecilian, the skin of which is transformed in brooding females to provide a rich supply of nutrients for the developing offspring. Young animals are equipped with a specialized dentition, which they use to peel and eat the outer layer of their mother's modified skin. This new form of parental care provides a plausible intermediate stage in the evolution of viviparity in caecilians. At independence, offspring of viviparous and of oviparous dermatotrophic caecilians are relatively large despite being provided with relatively little yolk. The specialized dentition of skin-feeding (dermatophagous) caecilians may constitute a preadaptation to the fetal feeding on the oviduct lining of viviparous caecilians.

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The skin of the aquatic pipid frog, Xenopus laevis, was examined for specific biomechanical features: 1) thickness, 2) maximal strain at break (epsilon f), 3) tensile strength (sigma m), 4) modulus of elasticity (E, stiffness), and 5) the area under the stress-strain curve (W) (breaking energy, toughness). Skin freshly removed from dorsal, ventral, and lateral areas of the body was subjected to uniaxial tension. In both sexes, the dorsal skin is thicker than the ventral. The skin of male frogs was consistently thinner in all body regions than that of females. Most biomechanical parameters showed a considerable range of values in both males (epsilon f = 59-63%, sigma m = 15-16.5 MPa, E = 33.5-38.4 MPa, W = 3.8-4.5 MJ/m3) and females (epsilon f = 102-126%, sigma m = 11.5 MPa, E = 10.4-12 MPa, W = 5.2-6.7 MJ/m3). The disparate epsilon f values in males (low) and females (high) might reflect sexual dimorphism. Static stress-strain curves were typically J-shaped; with the exception of a "toe," the curves rose approximately linearly with increasing strain. The skin of X.laevis, although heterogeneous in structure, possesses features similar to those found in tissues with aligned collagen fibers such as tendons or fish skin. However, in anurans, the skin seems to play a more passive mechanical role during locomotion than in fish.

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Variation of abundance, dominance and diversity of tardigrades were studied over a period of 54 months in a carpet of the moss Rhytidiadelphus squarrosus that covered a lawn in the Black Forest (Germany). Altogether 19,909 individuals belonging to 24 species were extracted from the moss. Macrobiotus hufelandi (56%), Macrobiotus richtersi (18%) and Diphascon pingue (12%) were the most abundant and dominant species. Dominances of the other species varied between 0.01 to 2.15%. Generally, species diversity (Shannon-Index and evenness) was highest during the winter. A temporal variation in numbers with a decline in winter and an increase in spring until fall was seen in M. hufelandi, D. pingue and less clear in M. richtersi. Three species (Diphascon rugosum, Hypsibius dujardini, Hypsibius cfr. convergens) showed a cyclic variation with clear peaks in wintertime. The moist season favoured species that were considered as hygrophilous in the literature, whereas the relatively dry sunny seasons promoted the relative increase of euryhygric species. The composition of the tardigrade community was strikingly robust over the years. Fourteen species were always present during the entire period of investigation. However, changes in the species composition over the years, and cyclical temporal presence of certain species stress the significance of long-term studies to estimate species richness in a given habitat. Application of the Spearman rank correlation test to the data set of the whole study period showed different correlations between the mean number of tardigrades as well as the mean number of individuals of selected species (dominance >1) and rainfall, humidity and temperature. Correlations confirmed some of the ecological dependences of tardigrade species known from literature. Conflicting classifications suggest dependence from other variables or perhaps presence of ecotypes

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