Ryan Mohammed

The freshwater fish of Tobago were reported by a number of researchers between 1910 and 1998, with differing species richness and diversity being listed by each. Results of the recent survey reported here serve to update this baseline. Surveys were conducted at 81 sites in Tobago over the time period 2004 to 2015, with observations being conducted both nocturnally and diurnally. The most widespread species was Sicydium punctatum (Gobiidae). The species with the highest abundance was Poecilia reticulate (Poeciliidae), and the rarest species was Gobiesox nudus (Gobiesocidae). Micropoecilia picta (Poeciliidae), Ctenogobius boleosoma (Gobiidae), and Synbranchus mamoratus (Synbranchidae) were documented for the first time for Tobago. The ichthyofaunal richness for the survey now stands at 13 species. The drainage with the greatest species richness was Roxborough River, with 9 species noted.

In June 2012 and March 2013 fieldwork in Tobago was conducted, investigating the presence and distribution of terrestrial and freshwater molluscs. During these visits several species that have not been previously recorded from the island were observed and one species that has not been recorded within at least the last three decades was observed. Tobago has a fairly depauperate gastropod molluscan fauna when it comes to the land and freshwater ecosystems with approximately nineteen species from ten families for the terrestrial snails (Robinson et al. 2004) and ten species from seven families for the freshwater species (Bass 2003). In this note we report on six new records representing five new species (Figure) and two new families. The Helicinidae snail Helicina nemoralis Guppy, 1866 is known from Trinidad and northern Venezuela but is rarely encountered as it is thought to be arboreal (

Ectotherms depend on the environmental temperature for thermoregulation and exploit thermal regimes that optimise physiological functioning. They may also frequent warmer conditions to up-regulate their immune response against parasite infection and/or impede parasite development. This adaptive response, known as 'behavioural fever', has been documented in various taxa including insects, reptiles and fish, but only in response to endoparasite infections. Here, a choice chamber experiment was used to investigate the thermal preferences of a tropical freshwater fish, the Trinidadian guppy (Poecilia reticulata), when infected with a common helminth ectoparasite Gyrodactylus turnbulli, in female-only and mixed-sex shoals. The temperature tolerance of G. turnbulli was also investigated by monitoring parasite population trajectories on guppies maintained at a continuous 18, 24 or 32 °C. Regardless of shoal composition, infected fish frequented the 32 °C choice chamber more often t...

SUMMARY The enemy release hypothesis proposes that in parasite depleted habitats, populations will experience relaxed selection and become more susceptible (or less tolerant) to pathogenic infections. Here, we focus on a population of guppies (Poecilia reticulata) that are found in an extreme environment (the Pitch Lake, Trinidad) and examine whether this habitat represents a refuge from parasites. We investigated the efficacy of pitch in preventing microbial infections in Pitch Lake guppies, by exposing them to dechlorinated water, and reducing gyrodactylid infections on non-Pitch Lake guppies by transferring them to Pitch Lake water. We show that (i) natural prevalence of ectoparasites in the Pitch Lake is low compared to reference populations, (ii) Pitch Lake guppies transferred into aquarium water develop microbial infections, and (iii) experimentally infected guppies are cured of their gyrodactylid infections both by natural Pitch Lake water and by dechlorinated water containing solid pitch. These results indicate a role for Pitch Lake water in the defence of guppies from their parasites and suggest that Pitch Lake guppies might have undergone enemy release in this extreme environment. The Pitch Lake provides an ideal ecosystem for studies on immune gene evolution in the absence of parasites and long-term evolutionary implications of hydrocarbon pollution for vertebrates.

To facilitate research and conservation of ocelots (Leopardus pardalis) in Trinidad, data was compiled in January 2014 and April 2015 on previous and current individuals housed at the Emperor Valley Zoo in Port of Spain as well as on maintenance and housing conditions. Historical records (genetic, spatial and temporal) had been destroyed by water, but interviews with zoo managers and employees produced considerable data. Ocelot breeding at the zoo is currently unmanaged because of a lack of staff. The genetics and geographic origin of the current housed ocelots is unknown. It is suggested that a structured breeding programme would maximise the breeding success of the current population at the zoo. This way the viability of the captive ocelots would be enhanced by increased genetic diversity obtained through the success of ocelot breeding and survival of kittens either for release into the wild or for display animals in the zoo.

Estuaries are highly productive aquatic systems. Five rivers in Guayaguayare Bay were sampled for fish and decapods by seining. During the survey, 33 species in 27 families representing nine orders were collected or observed. The most abundant species Mugil curema accounted for 54% of total catch. For the majority of species encountered, the size-frequency distributions revealed populations comprised largely of subadults and juveniles. Populations found within each small estuarine habitat are maintained over the entire coastline by a series of incompletely independent populations, which together can be termed metapopulations.

Abstract Our understanding of the evolution of genes of the major histocompatibility complex (MHC) is rapidly increasing, but there are still enigmatic questions remaining, particularly regarding the maintenance of high levels of MHC polymorphisms in small, isolated populations. Here, we analyze the genetic variation at eight microsatellite loci and sequence variation at exon 2 of the MHC class IIB (DAB) genes in two wild populations of the Trinidadian guppy, Poecilia reticulata. We compare the genetic variation of a small (Ne∼ 100) and relatively isolated upland population to that of its much larger (Ne∼ 2400) downstream counterpart. As predicted, microsatellite diversity in the upland population is significantly lower and highly differentiated from the population further downstream. Surprisingly, however, these guppy populations are not differentiated by MHC genetic variation and show very similar levels of allelic richness. Computer simulations indicate that the observed level of genetic variation can be maintained with overdominant selection acting at three DAB loci. The selection coefficients differ dramatically between the upland (s 0.2) and lowland (s≤ 0.01) populations. Parasitological analysis on wild-caught fish shows that parasite load is significantly higher on upland than on lowland fish, which suggests that large differences in selection intensity may indeed exist between populations. Based on the infection intensity, a substantial proportion of the upland fish would have suffered direct or indirect fitness consequences as a result of their high parasite loads. Selection by parasites plays a particularly important role in the evolution of guppies in the upland habitat, which has resulted in high levels of MHC diversity being maintained in this population despite considerable genetic drift.