Inbreeding depression in sperm quality in a critically endangered amphibian

Small, isolated populations often experience increased inbreeding and decreased heterozygosity, which increases the potential risk of inbreeding depression. The relationship between inbreeding and sperm health is well-documented in a variety of taxa, but has yet to be explored in amphibians. The dusky gopher frog, Lithobates sevosus, is a critically endangered species with years of documented inbreeding and low genetic variability as a consequence of isolation and population size reduction. This study investigated the effects of inbreeding on sperm quality in captive L. sevosus using an outbred, sister species (Lithobates pipiens) as a standard for comparison. We found L. sevosus to have severely reduced sperm quality in terms of total motility, forward progressive motility, concentration, and viability. Additionally, we observed a significant, negative relationship between total sperm motility and mean kinship within captive-bred individuals. These data serve to enhance our understanding of the role inbreeding plays in amphibians, and to provide valuable insight into new risk factors declining amphibian populations may face.     

Evaluating Habitat Quality for the Dusky Flycatcher

Abstract: We studied the dusky flycatcher (Empidonax oberholseri) at 8 sites in central Idaho, USA, in 2002 and 2003 to examine relationships among vegetation cover, density of breeding conspecifics, and indicators of habitat quality. Number of breeding territories and number of fledglings per hectare were positively associated, suggesting that the dusky flycatcher experienced increased reproductive success where it bred at the highest densities. However, the relationships between nesting success, annual reproductive success, number of fledglings per hectare, and amount of understory cover showed substantial annual variation. Nesting success did not differ significantly across sites or between years. Both reproductive success, expressed as young produced per hectare (range: 0.34–3.09 in 2002 and 0.79–3.82 in 2003) and young produced per nesting attempt (range: 0.71–2.78 in 2002 and 1.11–3.10 in 2003), differed across study sites in each year. Mean clutch size did not differ significantly among sites or years. Mean egg weight showed significant variation across some sites within years and was associated negatively with the 3 measures of reproductive success in 2002, although small sample sizes prevented reliable inference about the appropriateness of this measure as an indicator of habitat quality. Mean clutch size and mean egg weight were not associated with vegetation cover variables. Thus, dusky flycatcher reproductive success showed inconsistencies with individual vegetation measurements at the site scale. Forest managers who use vegetation treatments to increase amounts of understory shrub cover (e.g., by removing portions of the overstory conifer canopy) should increase densities of this species and, in turn, increase number of fledglings produced, but these responses appear to be better measured at the territory or nest scales than at the stand or site scales.     

Size matters: extraordinary rodent abundance on an Australian tropical flood plain

Abstract: Published estimates of the total biomass of natural populations of mammalian herbivores generally have ignored small‐bodied taxa (especially, rodents). Including such taxa may dramatically change our understanding of total biomass and energy flow in such systems. Dusky rats (Rattus colletti) are small (up to 210 g) native Australian mammals, and our 5‐year mark‐recapture study on a tropical flood plain (Adelaide River, Northern Territory) revealed that rat biomass can reach extraordinary levels (up to 4.7 t km^?2). Because their small body size results in high mass‐specific metabolic rates, a given biomass of rodents has a several‐fold higher total energy requirement than the same mass of large‐bodied herbivores. Accordingly, during some years dusky rat biomass can be double that estimated for large herbivores on the world's most productive savannas in eastern and southern Africa. The huge rodent biomass strongly suggests that the Adelaide River flood plain must be an incredibly productive habitat. Considering the immense biological importance of these productive ecosystems, flood plain conservation must be placed high on the priority list of habitats that require immediate protection.     

Migrating Birds as Dispersal Vehicles for West Nile Virus

Whereas migrating birds have been implicated in the spread of West Nile virus (WNV), there is no direct evidence of birds actively migrating while infectious. The role of birds in WNV dispersal is difficult to assess in the field. However, this role can be evaluated experimentally because birds in migratory disposition display increased locomotor activity or restlessness under captive conditions. We tested the following hypotheses: (1) migrating passerine birds continue to exhibit migratory activity while infectious with WNV and (2) the migratory state of the individual affects the magnitude of viremia. We examined the migratory activity of two neoarctic-neotropical passerine migrants, Swainson’s thrush (Catharus ustulatus) and gray catbird (Dumetella carolinensis), during acute WNV infection. All gray catbirds and six of nine Swainson’s thrushes exhibited migratory activity while infectious. Moreover, migratory status did not appear to influence viremia titers, as might be expected if individuals were immunosuppressed during migration. Therefore, we demonstrate that migrating passerine birds are potential dispersal vehicles for WNV.     

First record of pughead deformity in Myrichthys ocellatus (Ophichthidae) and Ephinephelus marginatus (Epinephelidae)

Pugheadness has being recorded in a wide variety of fish families on both natural and non-natural environments, though encountering pughead fish in wild population is rare. Here, we present two new records of pugheadness in the wild, for Myrichthys ocellatus (Ophichthidae), and for Epinephelus marginatus (Epinephelidae). An up to date compilation of the 39 published pugheadness in fish is presented. We believe that with the advancement of information and communication technology in social networks, more records of deformities in fish species will show up through the lenses of citizen science.     

SKIN SWABBING FOR GENETIC ANALYSIS: APPLICATION TO DUSKY DOLPHINS (LAGENORHYNCHUS OBSCURUS)

Exfoliated skin was collected from bowriding dolphins with the use of a sterilized nylon scrub pad affixed to a wooden dowel. Initial tests of the effectiveness of the technique and dolphin behavioral responses were conducted on dusky dolphins off Kaikoura, New Zealand. During 14 sampling days, 128 contacts using this procedure were made with bowriding dolphins, of which 114 showed behavioral response. Responses during sampling were mild, with 11% of contacted individuals showing no visible response, and 66% of individuals which could be monitored for 30 sec after contact returning to bowride within 30 sec. Mean return time was 10 sec postcontact and did not vary significantly for groups of different sizes. Behavioral controls suggest that a proportion of responses could be explained by typical dolphin behavior in the presence of boats. Seventy-eight percent of contacts resulted in successful collection of tissue samples. Sample time was three minutes on average. Size of group and behavioral state did not appear to influence sample time. Preliminary genetic analyses revealed that tissue collected by this technique was suitable for amplification and sequencing of mitochondrial DNA (mtDNA) via PCR. Comparisons of mtDNA control region sequences with those from known L. obscurus and other delphinid samples verified that this technique was robust against contamination from elements in sea water.