Comparison of a Manual and an Automated Method to Estimate the Number of Uterine Eggs in Anisakid Nematodes: To Coulter or Not to Coulter. Is That the Question?

Abstract

Studies reporting numbers of eggs in vagina and utero in nematodes often give little information of the technique used for the estimations. This situation hampers comparison among studies, because, so far, differences in estimations provided by different techniques have not been assessed. This note examines whether a manual method based on visual counts in aliquots and an automated method using a Coulter counter yield equivalent estimations of egg numbers in vagina and utero of 3 anisakid nematode species (Anisakis simplex, Pseudoterranova decipiens, and Contracaecum osculatum). The number of eggs from 50 females per nematode species was estimated using both techniques. The automated and manual methods yielded similar egg counts (correlation coefficients >0.9 in the 3 species), but the methods were not always statistically equivalent. The automated method was more precise and seemed less dependent on egg density, whereas the manual method was less time-consuming (contrary to previous perceptions) and less expensive. Despite the higher precision of automated counts, the manual technique seemed to produce similar estimates; thus, it may be particularly useful in developing countries where nematode parasitism is prevalent in humans and domestic animals, but scientific resources are limited.

Benefits of fidelity: does host specialization impact nematode parasite life history and fecundity?

“…As a measure of fecundity, we chose to restrict our analysis to nematode species with published values of eggs/female/day. Because intra-uterine egg counts are far more common, this placed a constraint on the number of species available for inclusion in our study; however, egg counts represent point estimates of egg production in time and may not necessarily accurately reflect lifetime fecundity (Herreras et al 2007 a ). With this restriction in mind, we were able to obtain our desired fecundity measure for 24 different nematode species (see Table 1 and references therein), 21 for which DNA sequence data could also be obtained to generate a phylogeny.…”

Phenotypic tradeoffs between egg number and egg size in three parasitic anisakid nematodes

“…Fifty females of three anisakid species ( A. simplex, P. decipiens and C. osculatum ) each were used in the present study. The three species differ in the number of eggs produced, ranging from tens of thousands (in C. osculatum ) to a few millions (in A. simplex ) (Herreras et al 2007). The specimens, preserved in 70% ethanol, were obtained from the authors’ collections: A. simplex was originally collected from nine harbour porpoises, Phocoena phocoena, off Denmark (Herreras et al 1997), and P. decipiens and C. osculatum from 22 grey seals, Halichoerus grypus, from the Gulf of St. Lawrence (Canada) (Marcogliese et al 1996).…”

“…Egg number in the vagina and uterus, mean egg volume and clutch volume (as proxies of egg mass and clutch mass, respectively) were used as descriptors of female reproductive output in all subsequent analyses. The number of eggs of each individual was estimated with a Coulter Counter as described in Herreras et al (2007). Egg volumes were calculated from digital microphotographs (80×magnification) taken at two uterine regions (proximal and distal) in each worm.…”