Lack of seasonal variation in the life-history strategies of the trematode Coitocaecum parvum: no apparent environmental effect

Department of Zoology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.
Parasitology (Impact Factor: 2.35). 10/2008; 135(10):1243-51. DOI: 10.1017/S0031182008004782
Source: PubMed

ABSTRACT Parasites with complex life cycles have developed numerous and very diverse adaptations to increase the likelihood of completing this cycle. For example, some parasites can abbreviate their life cycles by skipping the definitive host and reproducing inside their intermediate host. The resulting shorter life cycle is clearly advantageous when definitive hosts are absent or rare. In species where life-cycle abbreviation is facultative, this strategy should be adopted in response to seasonally variable environmental conditions. The hermaphroditic trematode Coitocaecum parvum is able to mature precociously (progenesis), and produce eggs by selfing while still inside its amphipod second intermediate host. Several environmental factors such as fish definitive host density and water temperature are known to influence the life-history strategy adopted by laboratory raised C. parvum. Here we document the seasonal variation of environmental parameters and its association with the proportion of progenetic individuals in a parasite population in its natural environment. We found obvious seasonal patterns in both water temperature and C. parvum host densities. However, despite being temporally variable, the proportion of progenetic C. parvum individuals was not correlated with any single parameter. The results show that C. parvum life-history strategy is not as flexible as previously thought. It is possible that the parasite's natural environment contains so many layers of heterogeneity that C. parvum does not possess the ability to adjust its life-history strategy to accurately match the current conditions.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: For conspecific parasites sharing the same host, kin recognition can be advantageous when the fitness of one individual depends on what another does; yet, evidence of kin recognition among parasites remains limited. Some trematodes, like Coitocaecum parvum, have plastic life cycles including two alternative life-history strategies. The parasite can wait for its intermediate host to be eaten by a fish definitive host, thus completing the classical three-host life cycle, or mature precociously and produce eggs while still inside its intermediate host as a facultative shortcut. Two different amphipod species are used as intermediate hosts by C. parvum, one small and highly mobile and the other larger, sedentary, and burrow dwelling. Amphipods often harbour two or more C. parvum individuals, all capable of using one or the other developmental strategy, thus creating potential conflicts or cooperation opportunities over transmission routes. This model was used to test the kin recognition hypothesis according to which cooperation between two conspecific individuals relies on the individuals' ability to evaluate their degree of genetic similarity. First, data showed that levels of intrahost genetic similarity between co-infecting C. parvum individuals differed between host species. Second, genetic similarity between parasites sharing the same host was strongly linked to their likelihood of adopting identical developmental strategies. Two nonexclusive hypotheses that could explain this pattern are discussed: kin recognition and cooperation between genetically similar parasites and/or matching genotypes involving parasite genotype-host compatibility filters.
    Journal of Evolutionary Biology 05/2014; DOI:10.1111/jeb.12413 · 3.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Anthropogenic stressors such as pollutants can modulate levels of parasitic infections in aquatic animals by suppressing host immunity or through some other mechanisms. One such mechanism could involve increases in either the quantity or quality of infective stages produced by parasites. We investigated the effect of exposure of infected snails, Potamopyrgus antipodarum, to different concentrations of the widely-used herbicide glyphosate, on (i) the production of infective cercariae by three trematode species, Coitocaecum parvum, Apatemon sp. and an undescribed renicolid, and (ii) the survival of cercariae of the latter species. For all three trematode species, infected snails exposed over a month to low (0.36 mg a.i. L−1) or medium (3.6 mg a.i. L−1) formulated glyphosate concentrations released between 1.5 and 3 times more cercariae per day than snails under control conditions. The similar pattern seen in all trematodes suggests a general weakening of the host benefiting any of its parasites rather than some parasite species-specific mechanism. In addition, the survival of renicolid cercariae improved with increasing glyphosate concentrations, with cercariae living about 50% longer in the medium concentration (3.6 mg a.i. L−1) than in control conditions. Our results demonstrate a clear interaction between glyphosate pollution and parasitism by trematodes in freshwater systems, occurring at glyphosate concentrations recorded in aquatic habitats, and within the environmental exposure limit allowed in New Zealand freshwaters. Future risk assessments and toxicity tests need to consider indirect impacts resulting from infections to invertebrate and vertebrate species penetrated by cercariae and serving as second intermediate hosts of trematodes.
    12/2012; 1:13–18. DOI:10.1016/j.ijppaw.2012.10.002
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Two new species of the microphallid genus Maritrema (Maritrema) Nicoll, 1907 are described from freshwaters in the South Island of New Zealand. Maritrema deblocki n. sp. occurs as an adult in the mallard Anas platyrhynchos (L.); Maritrema poulini n. sp. is found as sporocysts/cercariae in Potamopyrgus antipodarum (Gray) and as metacercariae in two species of amphipod and two species of isopod. We use morphological and molecular characterisation to distinguish between the two species, and compare them to their four morphologically closest congeners. M. deblocki n. sp. and M. poulini n. sp. are distinguished from each other by the relative sucker size, the positions of the genital pore and ovary, the convergence of the vitelline ribbons, and overall size. With the aid of molecular data, we matched life cycle stages of M. poulini n. sp. and assessed its use of multiple second intermediate hosts. Phylogenetic analyses included sequences for the two new species and the available microphallid sequences for the large ribosomal subunit and the internal transcribed spacer 1 of the ribosomal RNA gene. Closer to each other than to any other species, the sister species together with Maritrema novaezealandense Martorelli, Fredensborg, Mouritsen & Poulin, 2004, Maritrema heardi (Kinsella & Deblock, 1994), Maritrema eroliae Yamaguti, 1939 and Maritrema oocysta (Lebour, 1907) formed a well-supported clade. In addition, we clarify the taxonomic identity of several unidentified Microphallus spp. in the recent ecological literature from New Zealand and propose corrected spellings for a number of Maritrema species epithets.
    Parasitology Research 02/2014; 113(5). DOI:10.1007/s00436-014-3809-9 · 2.33 Impact Factor

Full-text (2 Sources)

Available from
May 21, 2014