Understanding amphidromy in Hawai'i: 'O'opu nākea (Awaous stamineus)

Hawai'i is home to 'o'opu nākea (Awaous stamineus), a culturally significant, endemic, goby that exhibits an amphidromous life cycle characterized by a marine larval stage followed by post-larval recruitment to streams, where they live to become reproductive adults. However, it was recently suggested that their migration to the ocean might not be obligatory, as originally thought. Despite their importance in Hawaiian traditions and the ecology of Hawaiian freshwater ecosystems, we still lack a full understanding of their migratory patterns and life history due to the difficulties in determining the environmental migratory cues that set the timing and location of their migratory paths. This study examined environmental factors, such as mean annual rainfall, streamflow, and water chemistry, to determine if they play a role in whether A. stamineus spend their larval period in the ocean or their entire life cycle in freshwater streams. We sampled A. stamineus (n = 90) from three streams (Kahana, Kahalu'u, and Waimānalo) on the island of O'ahu, Hawai'i that represented the range of hydroclimatic gradient in wet-habitat conditions on the windward side of the island and characterized their migratory pattern using elemental analysis of sagittae, the largest pair of otoliths (calcareous ear structures). Based on otolith strontium:calcium and barium:calcium ratios, we determined if individuals spent their larval period in the ocean or the stream. We found that 100% of individuals displayed clear evidence of marine residence during their larval phase, regardless of the environmental factors the fish experienced. This study highlights the necessity of stream-ocean connectivity for the survival of A. stamineus and emphasizes the importance of stream-mouth conservation and management as it is a critical transition zone in stream-ocean-stream migratory pathways.

Predicting the impacts of sea level rise in sea turtle nesting habitat on Bioko Island, Equatorial Guinea

Sea level is expected to rise 44 to 74 cm by the year 2100, which may have critical, previously un-investigated implications for sea turtle nesting habitat on Bioko Island, Equatorial Guinea. This study investigates how nesting habitat will likely be lost and altered with various increases in sea level, using global sea level rise (SLR) predictions from the Intergovernmental Panel on Climate Change. Beach profiling datasets from Bioko's five southern nesting beaches were used in GIS to create models to estimate habitat loss with predicted increases in sea level by years 2046-2065 and 2081-2100. The models indicate that an average of 62% of Bioko's current nesting habitat could be lost by 2046-2065 and 87% by the years 2081-2100. Our results show that different study beaches showed different levels of vulnerability to increases in SLR. In addition, on two beaches erosion and tall vegetation berms have been documented, causing green turtles to nest uncharacteristically in front of the vegetation line. We also report that development plans are currently underway on the beach least susceptible to future increases in sea level, highlighting how anthropogenic encroachment combined with SLR can be particularly detrimental to nesting turtle populations. Identified habitat sensitivities to SLR will be used to inform the government of Equatorial Guinea to consider the vulnerability of their resident turtle populations and projected climate change implications when planning for future development. To our knowledge this is the first study to predict the impacts of SLR on a sea turtle nesting habitat in Africa.

Migratory corridor linking Atlantic green turtle, Chelonia mydas, nesting site on Bioko Island, Equatorial Guinea to Ghanaian foraging grounds

This study uses satellite telemetry to track post-nesting movements of endangered green turtles (Chelonia mydas) (n = 6) in the Gulf of Guinea. It identifies a migratory corridor linking breeding grounds of Atlantic green turtles nesting on Bioko Island, Equatorial Guinea, to foraging grounds in the coastal waters of Accra, Ghana. Track lengths of 20–198 days were analyzed, for a total of 536 movement days for the six turtles. Migratory pathways and foraging grounds were identified by applying a switching state space model to locational data, which provides daily position estimates to identify shifts between migrating and foraging behavior. Turtles exhibited a combination of coastal and oceanic migrations pathways that ranged from 957 km to 1,131 km. Of the six turtles, five completed their migration and maintained residency at the same foraging ground near the coastal waters of Accra, Ghana until transmission was lost. These five resident turtles inhabit heavily fished waters and are vulnerable to a variety of anthropogenic threats. The identification of these foraging grounds highlights the importance of these coastal waters for the protection of the endangered Atlantic green turtle.

Long-Term Urban Market Dynamics Reveal Increased Bushmeat Carcass Volume despite Economic Growth and Proactive Environmental Legislation on Bioko Island, Equatorial Guinea

Bushmeat hunting is extensive in west and central Africa as both a means for subsistence and for commercial gain. Commercial hunting represents one of the primary threats to wildlife in the region, and confounding factors have made it challenging to examine how external factors influence the commercial bushmeat trade. Bioko Island, Equatorial Guinea is a small island with large tracts of intact forest that support sizeable populations of commercially valuable vertebrates, especially endemic primates. The island also has a low human population and has experienced dramatic economic growth and rapid development since the mid-1990's. From October 1997 - September 2010, we monitored the largest bushmeat market on Bioko in Malabo, recording over 197,000 carcasses for sale. We used these data to analyze the dynamics of the market in relation to political events, environmental legislation, and rapid economic growth. Our findings suggest that bushmeat hunting and availability increased in parallel with the growth of Equatorial Guinea's GDP and disposable income of its citizens. During this 13-year study, the predominant mode of capture shifted from trapping to shotguns. Consequently, carcass volume and rates of taxa typically captured with shotguns increased significantly, most notably including intensified hunting of Bioko's unique and endangered monkey fauna. Attempts to limit bushmeat sales, including a 2007 ban on primate hunting and trade, were only transiently effective. The hunting ban was not enforced, and was quickly followed by a marked increase in bushmeat hunting compared to hunting rates prior to the ban. Our results emphasize the negative impact that rapid development and unenforced legislation have had on Bioko's wildlife, and demonstrate the need for strong governmental support if conservation strategies are to be successful at preventing extinctions of tropical wildlife.

Genetic signatures of a demographic collapse in a large-bodied forest dwelling primate (Mandrillus leucophaeus)

It is difficult to predict how current climate change will affect wildlife species adapted to a tropical rainforest environment. Understanding how population dynamics fluctuated in such species throughout periods of past climatic change can provide insight into this issue. The drill (Mandrillus leucophaeus) is a large-bodied rainforest adapted mammal found in West Central Africa. In the middle of this endangered monkey's geographic range is Lake Barombi Mbo, which has a well-documented palynological record of environmental change that dates to the Late Pleistocene. We used a Bayesian coalescent-based framework to analyze 2,076 base pairs of mitochondrial DNA across wild drill populations to infer past changes in female effective population size since the Late Pleistocene. Our results suggest that the drill underwent a nearly 15-fold demographic collapse in female effective population size that was most prominent during the Mid Holocene (approximately 3-5 Ka). This time period coincides with a period of increased dryness and seasonality across Africa and a dramatic reduction in forest coverage at Lake Barombi Mbo. We believe that these changes in climate and forest coverage were the driving forces behind the drill population decline. Furthermore, the warm temperatures and increased aridity of the Mid Holocene are potentially analogous to current and future conditions faced by many tropical rainforest communities. In order to prevent future declines in population size in rainforest-adapted species such as the drill, large tracts of forest should be protected to both preserve habitat and prevent forest loss through aridification.

Island biogeography reveals the deep history of SIV

Simian immunodeficiency virus (SIV) lineages have been identified that are endemic to Bioko Island. The time the island formed offers a geological time scale calibration point for dating the most recent common ancestor of SIV. The Bioko viruses cover the whole range of SIV genetic diversity, and each Bioko SIV clade is most closely related to viruses circulating in hosts of the same genus on the African mainland rather than to SIVs of other Bioko species. Our phylogeographic approach establishes that SIV is ancient and at least 32,000 years old. Our conservative calibration point and analyses of gene sequence saturation and dating bias suggest it may be much older.

Effects of post-session injections of anisomycin on the extinction of a spatial preference and on the acquisition of a spatial reversal preference

Four experiments with C57BL/6 mice examined the effects of protein synthesis inhibition on extinction of spatial preferences in the Morris water maze. The protein synthesis inhibitor anisomycin was injected systemically immediately after spatial reversal sessions, which consisted of eight, two, or one reversal trials. Anisomycin had no effect on extinction of a spatial preference with eight reversal trials per session. When only two reversal trials were administered per session, anisomycin slowed extinction initially, although full extinction occurred with further training even in the presence of anisomycin. In both cases, anisomycin blocked acquisition of the reversal preference. When anisomycin injections followed a single simple extinction trial, performance was not disrupted. These findings suggest that acquisition and extinction may involve different molecular processes, and they do not support the idea that brief extinction trials induce a protein synthesis-dependent reconsolidation phase of spatial memory.

Phase variation of the 987P-like CS18 fimbriae of human enterotoxigenic Escherichia coli is regulated by site-specific recombinases

The gene cluster of the CS18 (PCFO20) fimbriae of human enterotoxigenic Escherichia coli (ETEC) was found to include seven genes (fotA to fotG) that are similar to each of the seven structural and export proteins of the 987P fimbriae. However, no analogous gene to the fasH regulatory gene, which is located at the 3' end of the 987P gene cluster and encodes an AraC-like activator of transcription, could be detected. Surprisingly, two novel genes (fotS and fotT) encoding proteins similar to the site-specific recombinases of the type 1 fimbriae (FimB and FimE) were identified at the 5' end of the fot gene cluster. These genes were shown to be required for the catalysis of a 312 bp-inversion just upstream of fotA. The inversion determines CS18 fimbrial phase variation. FotS participates in inverting the 312 bp-segment in both the ON and OFF orientation, whereas FotT has a bias for the OFF oriented recombination. Similar regulators of fimbriation by phase variation were described in uropathogenic and commensal Enterobacteriaceae. In contrast, only AraC-like transcriptional activators were previously described as regulators of the intestinal colonization factors of human ETEC isolates. Thus, the CS18 and 987P gene clusters encode similar components for fimbrial biogenesis but different types of regulators for fimbriation. The combination of blocks of genes encoding similar structural products but different regulatory proteins underlines how modular DNA rearrangements can evolve by serving pathogen diversification. Acquisition of a phase variation module to regulate fimbrial genes is proposed to be beneficial for the adaptation and transmission of pathogens.