Assessing the In Situ Fertilization Status of Two Marine Copepod Species, Temora longicornis and Eurytemora herdmani; How Common Are Unfertilized Eggs in Nature?

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.

Paternal energetic investments in copepods

“…The known spermatophore production rates are low, around 1 spermatophore male −1 d −1 , and decreasing with age (Sichlau and Kiørboe ; Burris and Dam ). The observed fraction of fertilized females in the field is lower than what mate encounter rates predict (Ceballos and Kiørboe ; Lasley‐Rasher et al ), as copepods have efficient ways to enhance mate encounters (e.g., Tsuda and Miller ; Bagøien and Kiørboe ). Thus, spermatophore production might limit mating rates in the wild (Titelman et al ).…”