Spatial distribution of epibionts on olive ridley sea turtles at Playa Ostional, Costa Rica.

There is a wealth of published information on the epibiont communities of sea turtles, yet many of these studies have exclusively sampled epibionts found only on the carapace. Considering that epibionts may be found on almost all body-surfaces and that it is highly plausible to expect different regions of the body to host distinct epibiont taxa, there is a need for quantitative information on the spatial variation of epibiont communities on turtles. To achieve this, we measured how total epibiont abundance and biomass on olive ridley turtles Lepidochelys olivacea varies among four body-areas of the hosts (n = 30). We showed that epibiont loads on olive ridleys are higher, both in terms of number and biomass, on the skin than they are on the carapace or plastron. This contrasts with previous findings for other hard-shelled sea turtles, where epibionts are usually more abundant on the carapace or plastron. Moreover, the arguably most ubiquitous epibiont taxon for other hard-shelled sea turtles, the barnacle Chelonibia spp., only occurred in relatively low numbers on olive ridleys and the barnacles Stomatolepas elegans and Platylepas hexastylos are far more abundant. We postulate that these differences between the epibiont communities of different sea turtle taxa could indicate that the carapaces of olive ridley turtles provide a more challenging substratum for epibionts than do the hard shells of other sea turtles. In addition, we conclude that it is important to conduct full body surveys when attempting to produce a holistic qualitative or quantitative characterization of the epibiont communities of sea turtles.

Epibiotic Diatoms Are Universally Present on All Sea Turtle Species.

The macro-epibiotic communities of sea turtles have been subject to growing interest in recent years, yet their micro-epibiotic counterparts are almost entirely unknown. Here, we provide the first evidence that diatoms are epibionts for all seven extant species of sea turtle. Using Scanning Electron Microscopy, we inspected superficial carapace or skin samples from a single representative of each turtle species. We distinguished 18 diatom taxa from these seven individuals, with each sea turtle species hosting at least two diatom taxa. We recommend that future research is undertaken to confirm whether diatom communities vary between sea turtle species and whether these diatom taxa are facultative or obligate commensals.

Relict snakes of North America and their relationships within Caenophidia, using likelihood-based Bayesian methods on mitochondrial sequences.

This paper focuses on the phylogenetic relationships of eight North American caenophidian snake species (Carphophis amoena, Contia tenuis, Diadophis punctatus, Farancia abacura, Farancia erytrogramma, Heterodon nasicus, Heterodon platyrhinos, and Heterodon simus) whose phylogenetic relationships remain controversial. Past studies have referred to these "relict" North American snakes either as colubrid, or as Neotropical dipsadids and/or xenodontids. Based on mitochondrial DNA ribosomal gene sequences and a likelihood-based Bayesian analysis, our study suggests that these North American snakes are not monophyletic and are nested within a group (Dipsadoidea) that contains the Dipsadidae, Xenodontidae, and Natricidae. In addition, we use the relationships proposed here to highlight putative examples of parallel evolution of hemipenial morphology among snake clades.

Temporal changes in the frequency of colicinogeny in Escherichia coli from house mice.

Escherichia coli was isolated from feral house mice (Mus domesticus) during the course of a mouse plague in the state of Victoria, Australia. The isolates were characterized for the production of colicins and their resistance to the co-occurring colicins. Of the 447 isolates examined, 59% were found to be colicinogenic. Phenotypic and PCR-based genotypic methods were used to determine the types of colicins being produced. Colicin E2 was the most common, representing 27% of the colicin-producing isolates. Colicin Ia was produced by 3% of the colicinogenic isolates. The remaining colicins could not be identified, but phenotypic and PCR data argue that at least nine different colicin types are present in this collection of E. coli. The frequency of colicinogenic isolates declined from 71% to 43% over the 7 months of the study. All colicin types appeared to decline in frequency. Concurrently, the resistance of isolates to colicin E2 increased from about 50% to 70%. Two hypotheses are proposed to explain the decline in the frequency of colicinogeny in this population of E. coli. The first relates to the within-host interactions occurring among colicinogenic, colicin-susceptible and colicin-resistant populations within a host. The second relates to the among-host interactions between susceptible and colicinogenic populations and the effect of host population densities on these interactions.