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Assessing the in situ fertilization status of two marine copepod species, Temora longicornis and Eurytemora herdmani; how common are unfertilized eggs in nature?

Lasley-Rasher RS, Kramer AM, Burdett-Coutts V, Yen J - PLoS ONE (2014)

Bottom Line: This may be a result of the asymmetrical costs associated with carrying vs. spawning unfertilized eggs.T. longicornis fertilization was negatively associated with chlorophyll concentration and positively associated with population density in their local habitat.The fertilization status of E. herdmani egg sacs was high throughout the season, but the proportion of ovigerous females was negatively associated with an interaction between predators and the proportion of females in the population.

View Article: PubMed Central - PubMed

Affiliation: School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America.

ABSTRACT
We utilized an egg staining technique to measure the in situ fertilization success of two marine copepod species, Temora longicornis and Eurytemora herdmani from May to October 2008 in coastal Maine and correlated fertilization success with environmental conditions in their habitat. T. longicornis is a free spawning species that releases eggs into the ambient seawater after mating. In contrast, E. herdmani carries eggs in an egg sac until they hatch. The proportion of fertilized eggs within E. herdmani egg sacs was significantly higher than the freely spawned clutches of T. longicornis. This may be a result of the asymmetrical costs associated with carrying vs. spawning unfertilized eggs. T. longicornis frequently laid both fertilized and unfertilized eggs within their clutch. T. longicornis fertilization was negatively associated with chlorophyll concentration and positively associated with population density in their local habitat. The fertilization status of E. herdmani egg sacs was high throughout the season, but the proportion of ovigerous females was negatively associated with an interaction between predators and the proportion of females in the population. This study emphasizes that, in addition to population level processes, community and ecosystem level processes strongly influence the fertilization success and subsequent productivity of copepods.

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The proportion of fertilized eggs within the clutches of Eurytemora herdmani and Temora longicornis females (mean ± SE).Females were captured from the field and their clutches stained with a nuclei specific probe (n = 68 and n = 83 for E. herdmani and T. longicornis, respectively). Proportion of fertilized eggs were compared using a generalized linear model with a quasibinomial distribution and logit-link function (F1,150 = 109, p<0.001).
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pone-0112920-g001: The proportion of fertilized eggs within the clutches of Eurytemora herdmani and Temora longicornis females (mean ± SE).Females were captured from the field and their clutches stained with a nuclei specific probe (n = 68 and n = 83 for E. herdmani and T. longicornis, respectively). Proportion of fertilized eggs were compared using a generalized linear model with a quasibinomial distribution and logit-link function (F1,150 = 109, p<0.001).

Mentions: Freely spawned clutches of T. longicornis contained a significantly lower proportion of fertilized eggs when compared to E. herdmani egg sacs (Fig. 1, F1,150 = 109, p<0.001, GLM quasibinomial distribution). Results from our field survey indicated that T. longicornis fertilization was negatively associated with chlorophyll concentration (Fig. 2, Table 2, p = 0.002, GLMM binomial distribution) and positively associated with population density (Fig. 2, Table 2, p = 0.03, GLMM binomial distribution). However, no significant correlation between chlorophyll concentration and population density was detected (Pearson’s correlation test, r = 0.13, df = 81, p = 0.24). Chlorophyll concentrations ranged from 1.4 to 6.2 µg carbon L−1 with minimum and maximum values observed in September and August respectively (Fig. 2B). The zero-inflated Poisson regression model predicting the number of eggs produced by T. longicornis in 6 h from chlorophyll concentration values showed a significant positive association between egg production and chlorophyll concentration (X2 = 19.4, df = 2, p<0.001). Monthly average population densities of T. longicornis ranged from 8 to 51 individuals m−3 with minimum densities observed in May and maximum densities observed in June and July (Fig. 2C). There was no significant effect of sex ratio on T. longicornis fertilization success (Table 2). The proportion of females within T. longicornis populations were not significantly different than 0.5 (equality of sex ratio) during any month in our survey except October when the population was significantly male skewed (one sample t-test, t = 6.2, df = 4, p<0.05).


Assessing the in situ fertilization status of two marine copepod species, Temora longicornis and Eurytemora herdmani; how common are unfertilized eggs in nature?

Lasley-Rasher RS, Kramer AM, Burdett-Coutts V, Yen J - PLoS ONE (2014)

The proportion of fertilized eggs within the clutches of Eurytemora herdmani and Temora longicornis females (mean ± SE).Females were captured from the field and their clutches stained with a nuclei specific probe (n = 68 and n = 83 for E. herdmani and T. longicornis, respectively). Proportion of fertilized eggs were compared using a generalized linear model with a quasibinomial distribution and logit-link function (F1,150 = 109, p<0.001).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4232583&req=5

pone-0112920-g001: The proportion of fertilized eggs within the clutches of Eurytemora herdmani and Temora longicornis females (mean ± SE).Females were captured from the field and their clutches stained with a nuclei specific probe (n = 68 and n = 83 for E. herdmani and T. longicornis, respectively). Proportion of fertilized eggs were compared using a generalized linear model with a quasibinomial distribution and logit-link function (F1,150 = 109, p<0.001).
Mentions: Freely spawned clutches of T. longicornis contained a significantly lower proportion of fertilized eggs when compared to E. herdmani egg sacs (Fig. 1, F1,150 = 109, p<0.001, GLM quasibinomial distribution). Results from our field survey indicated that T. longicornis fertilization was negatively associated with chlorophyll concentration (Fig. 2, Table 2, p = 0.002, GLMM binomial distribution) and positively associated with population density (Fig. 2, Table 2, p = 0.03, GLMM binomial distribution). However, no significant correlation between chlorophyll concentration and population density was detected (Pearson’s correlation test, r = 0.13, df = 81, p = 0.24). Chlorophyll concentrations ranged from 1.4 to 6.2 µg carbon L−1 with minimum and maximum values observed in September and August respectively (Fig. 2B). The zero-inflated Poisson regression model predicting the number of eggs produced by T. longicornis in 6 h from chlorophyll concentration values showed a significant positive association between egg production and chlorophyll concentration (X2 = 19.4, df = 2, p<0.001). Monthly average population densities of T. longicornis ranged from 8 to 51 individuals m−3 with minimum densities observed in May and maximum densities observed in June and July (Fig. 2C). There was no significant effect of sex ratio on T. longicornis fertilization success (Table 2). The proportion of females within T. longicornis populations were not significantly different than 0.5 (equality of sex ratio) during any month in our survey except October when the population was significantly male skewed (one sample t-test, t = 6.2, df = 4, p<0.05).

Bottom Line: This may be a result of the asymmetrical costs associated with carrying vs. spawning unfertilized eggs.T. longicornis fertilization was negatively associated with chlorophyll concentration and positively associated with population density in their local habitat.The fertilization status of E. herdmani egg sacs was high throughout the season, but the proportion of ovigerous females was negatively associated with an interaction between predators and the proportion of females in the population.

View Article: PubMed Central - PubMed

Affiliation: School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America.

ABSTRACT
We utilized an egg staining technique to measure the in situ fertilization success of two marine copepod species, Temora longicornis and Eurytemora herdmani from May to October 2008 in coastal Maine and correlated fertilization success with environmental conditions in their habitat. T. longicornis is a free spawning species that releases eggs into the ambient seawater after mating. In contrast, E. herdmani carries eggs in an egg sac until they hatch. The proportion of fertilized eggs within E. herdmani egg sacs was significantly higher than the freely spawned clutches of T. longicornis. This may be a result of the asymmetrical costs associated with carrying vs. spawning unfertilized eggs. T. longicornis frequently laid both fertilized and unfertilized eggs within their clutch. T. longicornis fertilization was negatively associated with chlorophyll concentration and positively associated with population density in their local habitat. The fertilization status of E. herdmani egg sacs was high throughout the season, but the proportion of ovigerous females was negatively associated with an interaction between predators and the proportion of females in the population. This study emphasizes that, in addition to population level processes, community and ecosystem level processes strongly influence the fertilization success and subsequent productivity of copepods.

Show MeSH
Related in: MedlinePlus