J.R. Downie

Thermal conditions in nests of loggerhead turtles: further evidence suggesting female skewed sex ratios of hatchling production in the Mediterranean

Ž. Temperature was recorded in 23 nests of the loggerhead turtle Caretta caretta and control Ž XX . sites of nest depth at Alagadi 35833 N, 33847 E , Northern Cyprus, eastern Mediterranean. Control site sand temperature was found to be highly correlated with mean daily air temperature and mean nest temperature. Mean temperature in nests ranged from 29.58C to 33.28C, with mean temperature in the middle third of incubation ranging from 29.38C to 33.78C. Hatching success was significantly correlated with incubation temperature, with nests experiencing very high temperatures exhibiting low hatching success. All nests demonstrated regular diel variation in temperature with mean daily fluctuations ranging from 0.38C to 1.48C. Increase in temperature above that of the prevailing sand temperature attributed to metabolic heating was clearly demonstrated in 14 of 15 clutches, with the mean level of metabolic heating of all nests being 0.48C. However, the level of metabolic heating varied markedly throughout the incubation period with levels being significantly higher in the final third of incubation. Incubation duration was found to be significantly correlated to both the mean temperature of nests throughout the incubation period and during the middle third of incubation. The relationship between incubation duration and mean incubation temperature was used to estimate mean incubation temperatures at

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.

Survival of Larval Leptodactylus fuscus (Anura: Leptodactylidae) out of Water: Developmental Differences and Interspecific Comparisons

Abstract Hatchlings of Leptodactylus fuscus can survive up to several weeks in their foam nests. Field observations showed that later-stage tadpoles could survive several days under leaves or rocks if their pool dried out. Laboratory experiments investigated the basis of these different out of water survival capacities and compared them to three other species. Recently hatched groups of tadpoles of L. fuscus on a damp substrate generated foam whose quality varied with the level of hydration of the substrate: at high hydration, the mucus of the foam drew water from the substrate, but at low hydration, water was drawn from the tadpoles. When such tadpoles remained longer in the foam nest, their ability to generate foam declined. Individual recently hatched tadpoles did not make foam out of water but did absorb water from wetter substrates. Later stage tadpoles of L. fuscus survived well out of water for at least six days but lost water gradually to the substrate (the drier, the faster). The dendrobatid Mannophryne trinitatis showed similar out of water survival to L. fuscus, but the leptodactylid Physalaemus pustulosus was much more limited, and the bufonid Bufo beebei had very little out of water survival ability. Tadpoles of L. fuscus lost water to the substrate proportionately more from the gut than from other organs, suggesting some regulatory capacity. Recently hatched tadpoles of L. fuscus showed better water retention when in groups in foam than when single on a damp substrate.

A new species of Megaselia (Diptera, Phoridae) whose larvae prey upon the eggs of Leptodactylus fuscus (Anura, Leptodactylidae)

Megaselia nidanurae Disney sp. nov. is described from a series of males and females reared from larvae preying on the eggs of the foam-nesting frog Leptodactylus fuscus (Schneider) in Trinidad. The general biology of the association suggests that this is an obligate relationship for the fly. This is the first description of a ‘frogfly’ attacking foam-nests hidden in burrows.

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.

Are there costs to extended larval transport in the Trinidadian stream frog, Mannophryne trinitatis (Dendrobatidae)?

Previous work has shown that male Mannophryne trinitatis (Dendrobatidae) carry their larvae on their backs for up to 4 days in search of a predator‐free pool in which to deposit them. The experiments reported here investigated whether costs to the larvae or to the adults limit transport duration. We simulated transport durations of 0, 4, 8, and 12 days for larvae, but found no deterioration in terms of ability to grow to metamorphosis; indeed, 12‐day larvae grew better than all the others. After 8 days of simulated transport, larvae had used up all their yolk reserves and begun to lose dry weight. Larvae on wet substrates gained wet weight and length but on drier substrates merely maintained weight, suggesting that dehydration could be a problem on the males back. In a trial of locomotor performance (mean jump length; number of jumps to traverse a runway), females performed best with calling males not significantly different from transporting males, despite an average larval load equivalent to 15–20% of the frogs mass. Assessment of gut contents showed that females foraged more than males, but that transporting males foraged as much as did calling males. We found no differences between the three classes of adult frogs in fat body weight.

The Golden Tree Frog of Trinidad, Phyllodytes auratus (Anura: Hylidae): systematic and conservation status

Analyses of mitochondrial 12S and 16S rDNA sequences lead us to propose that the Neotropical hylid genus Phyllodytes is paraphyletic. The level of divergence between the Trinidadian endemic P. auratus and the two Brazilian Phyllodytes included in the analyses (Phyllodytes sp. and P. luteolus) is greater than that of inter‐generic distances within the Lophiohylini. The molecular evidence here reported, behavioural differences and restriction to a single host plant in a geographically limited area differentiates Phyllodytes auratus from other supposed Phyllodytes evidencing its unique taxonomic status. We therefore propose a new genus, Phytotriades gen. nov., for Phyllodytes auratus. P. auratus mitochondrial cytochrome b sequences obtained from one locality (seven individuals) contained two haplotypes, one individual differing by a single transition. The other locality (one individual) had the commoner haplotype. The low genetic divergence between the two populations suggests recent isolation at these two localities.

Tadpole deposition behaviour in male stream frogs Mannophryne trinitatis (Anura: Dendrobatidae)

Male Mannophryne trinitatis transport their larvae on their backs to predator‐free pools and deposit them there. The experiments reported here investigated M. trinitatis male deposition behaviour in containers placed near a heavily fish‐populated stream at Mount Saint Benedict, northern Trinidad. Choice of deposition site was not related to height above or distance from the stream. The low mean number of tadpoles deposited in each container in the field and in a laboratory experiment indicated that most males tended not to deposit complete clutches in single pools. Deposition experiments in the laboratory with a choice of different‐sized containers showed that deposition was pool size dependent, with more tadpoles deposited in larger containers. Deposition behaviour when given a choice of containers with leaf litter (a source of food and shelter) and with no leaf litter showed no significant preference. Tadpoles grown in different water volumes with different food sources revealed that tadpole growth was best in larger water volumes containing leaf litter. Regular tadpole inspections at a pool in the field established that most tadpoles present were the result of downstream movement.

Variability in escape trajectory in the Trinidadian stream frog and two treefrogs at different life-history stages

Most studies investigating anuran jumping behaviour have examined the relationship between body size and parameters such as jump distance, velocity, and force; however, few have investigated jump trajectory. We constructed an arena to determine escape trajectories in relation to the direction of an artificial stimulus in the aromobatid Mannophryne trinitatis (Garman, 1888) and two treefrogs, Trachycephalus venulosus (Laurenti, 1768) and Hypsiboas geographicus (Spix, 1824). Three categories of M. trinitatis (i.e., tadpole-transporting males, nontransporting males, and females) and three ontogenetic stages of the treefrogs were compared. Mannophryne trinitatis escaped in a broadly predictable trajectory away from the stimulus, although jump trajectories were highly variable, suggesting a degree of unpredictability. No systematic differences were found between categories of M. trinitatis, adding to the findings of previous studies that larval transport incurs no measurable locomotor costs on antipredatory ju...