Proportions of eggs laid by Aedes aegypti on different substrates within an ovitrap in Trinidad, West Indies

Abstract. Ovitraps were exposed outdoors during wet and dry seasons in Trinidad to determine the proportions of eggs laid on three substrates: the widely-used hardboard 'paddle' (P), the water surface (W) and the inside surface of the ovitrap wall (S) in three types of blackened ovitrap: round, glass (RG), round, plastic (RP) and rectangular, plastic (SP). Of the 3556 eggs obtained, most (86.4%) were laid during the wet season when statistically significant differences were detected between substrates but not between ovitrap types. Most eggs (>80%) were laid on P, significantly fewer ( P < 0.005) on W, on S and on W + S, thus confirming the superiority of the paddle as a device for monitoring oviposition activity. Implications of these findings for the interpretation of Aedes studies using ovitraps are discussed.     

Correlates of reproductive success in a Caribbean village

Genealogical, demographic, and economic data collected in a rural Trinidadian village indicate that: (1) individuals with more land have more offspring, (2) males with more land have higher mating success, (3) young adults with parents resident in the village have higher reproductive success, and (4) the residence of father has a strong effect on young adult male reproductive success, but apparently has no effect on young adult female reproductive success, suggesting a gender bias in nepotism. The results indicate that there are important gender differences in the effect of resources on reproduction and in patterns of parent-offspring interaction.     

The Onychophora of Trinidad, Tobago and the Lesser Antilles

This paper brings together the scattered literature on the Onychophora from Trinidad, Tobago and the Lesser Antilles. The 11 known species from this area are described, incorporating new material collected by the author. Scanning electron micrographs of the dorsal integument are presented for all but one species. Parthenogenesis is reported in a population of Epiperipatus imthurni from Trinidad.     

The Cissia confusa species-group in Costa Rica and Trinidad (Lepidoptera: Satyrinae)

The generic names Euptychia, Cissia and Argyreuplychia are reviewed in relation to the Cissia confusa species-group in Costa Rica and Trinidad, for which the generic name Cissia Doubleday is formally resurrected. Three new species of Cissia are described, C. confusa itself is resurrected from synonymy, three neotypes and three lectotypes are designated, and six new combinations established. On the basis of early instar morphology three subgroups are recognized and the general biology of the confusa species-group is summarized. A key to species in Costa Rica is provided and the ecology of the adults is reviewed.     

The cyprinodont fish Rivulus (Aplocheiloidei: Rivulidae) in Trinidad and Tobago: molecular evidence for marine dispersal, genetic isolation and local differentiation

Mitochondrial DNA sequences (756 bp) were obtained from the cytochrome b gene of 36 Rivulus individuals collected from 10 sites in Trinidad and one site in Tobago. Eight haplotypes were identified. Low genetic divergence (0.5%) between one western Trinidad (Blue Basin) haplotype and Rivulus hartii from north-western Venezuela (Paria peninsula) and high genetic divergence ( c. 11%) between these and the remaining other Trinidad and Tobago haplotypes suggests that the islands were colonized by two lineages. The commoner haplotype is distributed throughout lowland Trinidad, possibly a reflection of flooding of the Orinoco River leading to high dispersal between watersheds. Rivulus from higher altitude (Northern Range) localities that would not have been affected by such flooding show high genetic divergence between sites. The genetic differentiation between northern and southern watersheds suggests isolation between some of these drainages.     

A bat (Chiroptera) survey of Mora rainforest in Trinidad's Victoria-Mayaro Forest Reserve

The bat fauna of the Mora excelsa-dominated rainforest in the Victoria-Mayaro Forest Reserve (VMFR) in south-east Trinidad was assessed over a six-week period. Trapping effort totaled 271 mist net hours and caught 143 bats of 22 species at a rate of one bat every two net-hours. Simpsons diversity index (1/D) was 1.28 for primary Mora forest and extrapolation using Chaos' estimator, a non-parametric method, estimated the total number of species as 39. Phyllostomid bats of the subfamilies Phyllostominae and Stenodermatinae were well represented, and frugivores predominated in number, accounting for 77% of all captures in primary forest. The most abundant bat, the ground-storey frugivore, Carollia perspicillata, accounted for 43% of all captures in primary forest and, in contrast to most bats, was also abundant on man-made paths through the forest. Four species not previously recorded from the reserve, Tonatia bidens, Trachops cirrhosus, a Myotis sp., and the rare Phylloderma stenops, were captured, bringing the total number of bats species known from the reserve to 35. Thus, over half (52%) of Trinidad's 67 bat species occur in this one forest reserve, making it a high priority area for effective protection and management.     

Efficacy of sticky and standard ovitraps for Aedes aegypti in Trinidad,West Indies

The double sticky trap (DST) is described for the first time and is evaluated along with standard ovitraps and sticky traps (STs) to determine population densities of Ae. aegypti in the urban township of St. Augustine and the rural community of Tamana, Trinidad, West Indies. Ten houses were selected at each study site. At each of the ten houses, one ovitrap, one ST, and one DST were placed using the criteria established for placement of ovitraps. The results showed the three trapping methods successfully collected Ae. aegypti mosquitoes. All three traps collected significantly more adults or eggs in St. Augustine than in Tamana. DSTs collected 2,286 adults from St. Augustine vs 316 adults from Tamana (p<0.002), STs collected 1,480 and 220 adults, respectively (p<0.01), and the ovitraps collected 2,735 and 517 eggs, respectively from St. Augustine and Tamana (p<0.002). Based on these results, the DSTs collected significantly (P<0.02) more adults than the STs. The DSTs and STs collected both adult and immature stages which can be used for toxicology, virology, and PCR studies and are suitable alternative Ae. aegypti surveillance tools for the Caribbean and Latin American region.     

Seasonal abundance, biting cycle and parity of the mosquito Haemagogus leucocelaenus in Trinidad, West Indies

Adult female populations of Haemagogus leucocelaenus (Dyar and Shannon), the sylvan vector of yellow fever, were monitored weekly during 1981–82 by human collectors on the ground at Point Gourde in Chaguaramas Forest, 16 km west of Port of Spain, Trinidad.
Hg.leucocelaenus showed only diurnal landing activity, from 06.00 to 18.00 hours (sunrise to sunset, universal time), with a single peak of activity between 10.00 and 14.00 hours.
Densities of Hg.leucocelaenus during the wet season (May–November) were about double the level recorded during the dry season (December–April).
Monthly parous rates averaged 53.9% (range 25–90%) and some females were up to five-pars. Retained eggs (range 2–6, mean 4/female) were found in the ovaries of 0.34% of landing females, all of which had stage 1 ovarian follicles for the next gonotrophic cycle. Therefore blood-feeding is not inhibited by egg retention. Hg. leucocelaenus vector potential is reappraised in the light of these findings.     

Environmental factors influencing adult sex ratio in Poecilia reticulata: laboratory experiments

The potential causes of adult sex ratio variation in guppies Poecilia reticulata were tested in laboratory experiments that evaluated the mortality rates of male and female P. reticulata exposed to potential predators (Hart's rivulus Rivulus hartii and freshwater prawns Macrobrachium crenulatum) and to different resource levels. Poecilia reticulata mortality increased in the presence of R. hartii and M. crenulatum, and low resource levels had an effect on mortality only in the presence of M. crenulatum. Rivulus hartii preyed more often on male than on female P. reticulata, and this sex-biased predation was not simply the result of males being smaller than females. In contrast, no sex-biased mortality was attributable to M. crenulatum or low resource levels.