Abstract
The species composition and infection levels were determined for helminth parasites in the mole crab, Emerita rathbunae, collected from seven sandy beaches from Guerrero and Michoacan, Mexico. A total of 494 crabs were collected between August and December of 2009. The number of crabs that were examined from each beach varied from 40 in Lazaro Cardenas to 114 in El Revolcadero. The cephalothorax length varied significantly between the sampled beaches, from 32.9 ± 5.5 mm (Ixtapa) to 40.5 ±1.7 mm(Las Trancas). Four species of larval parasites were identified: 1 metacercaria (Microphallus nicolli), 1 cystacanth (Profilicollis sp.), 1 cestode (Trypanorhyncha) and 1 nematode (Proleptus sp.). Infection levels (prevalence and mean abundance) varied significantly between beaches, due to possible differences in the availability of final or intermediate hosts in beaches visited by tourist and those beaches not visited by tourists, as well as the size of individual hosts. Helminth communities, at levels of component and infracommunity, were characterized by a low number of species (3 to 4) and a high dominance by the metacercaria of M. nicolli. The body size of the hosts was positively correlated with the number of parasites and species richness of helminths, indicating that larger crabs accumulate a higher number of parasites during the lifetime, and that they harbor a higher number of species of helminth than smaller crabs.
Highlights
In natural populations of free living organisms, the infection levels of parasites differ among localities and seasons, providing a strong indication that the recruitment of parasites by the population of hosts is variable in time and in space [1]-[3]
Four species of larval helminth were identified in the samples from the seven beaches: Microphallus nicolli, Profilicollis sp., Trypanorhyncha, and Proleptus sp
Mean abundance ranged from 0.19 ± 0.10 (Revolcadero) to 1.32 ± 0.74 (Barra Vieja) (Figure 2), this difference was not significant among beaches (χ2 = 7.2, P > 0.05)
Summary
In natural populations of free living organisms, the infection levels of parasites differ among localities and seasons, providing a strong indication that the recruitment of parasites by the population of hosts is variable in time and in space [1]-[3]. Most of the studies carried out to date on temporal and spatial variation have been focused mainly on the population dynamics of trematodes. Those studies suggest that the variation in the infections levels of parasites is a consequence of several factors, such as host movement, population density, life history, susceptibility to infection and to the dispersion and behavior of the parasites [2] [4]-[7]. The spatial heterogeneity in the parasite distribution observed among populations of intermediate hosts, has been attributed both to the higher mobility of the definitive hosts and to associated behavior patterns [2] [5] [6] [9]
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