Paternal energetic investments in copepods

Abstract

Copepod mating is a complex behavioral interplay between males and females. But successful mating also requires a physiological component in terms of egg-and spermatophore production. In striking contrast to the extensive literature on copepod egg production, costs of spermatophore production has largely been ignored. This article explores the energetic demands in male copepod reproduction, testing how food and predation risk influence spermatophore production. Moreover, we analyse swimming behavior to test if predation risk and food act on reproductive investments via behavioral responses. We found that spermatophore production depends strongly on food availability. The copepods increased grazing rates with predation risk when food was limited, and video analyses revealed that males spend less time swimming in presence of a risk cue. A review of the few available spermatophore production rates suggests that food limits spermatophore production for copepods at large. Apparently, potential encounter rates with mates or predators did not influence spermatophore production. However, the reduced activity indicates a trade-off between risk avoidance and mate encounter, potentially influencing mating rates. This study shows that males invest considerable resources in each spermatophore, with implications for mating strategies and population dynamics in copepods, the most abundant metazoans on earth.

Motile behavior and predation risk in planktonic copepods

“…The magnitude of the difference varies among the three main feeding strategies (Kiørboe ): A non‐motile ambush feeder cannot feed and search mates simultaneously, and the males therefore intermittently sacrifice feeding to engage in fast swimming to search for females with an expected higher predation risk in males than in females (Kiørboe ). In active feeding copepods, on the other hand, males swim and feed simultaneously (Bjaerke et al ) and the conflict between feeding and mate‐finding is less as is the expected difference in predation risk between genders (Van Duren and Videler ; Kiørboe ).…”

Saving for the future: Pre‐winter uptake of algal lipids supports copepod egg production in spring

“…The costs of reproduction are not limited to oocyte development, and recent evidence suggests that spermatophore production may require considerable resource investment in copepods (Bjaerke et al, 2015;Burris & Dam, 2015). Although the typical astaxanthin content of spermatophores is not known, our recent results suggest that it might be coupled to FA allocation (Schneider et al, 2016).…”

Salinisation and warming disrupt predator-induced drift behaviour in aquatic predator-prey interactions

“…This has, e.g., been observed in mayfly larvae that exhibited only increased short-term drifting behaviour in response to predators (Culp et al, 1991). In fact, many prey animals balance the costs of predator-induced behaviour against other fitness-related activities such as foraging and mating (Bjærke et al, 2016; Lima and Dill, 1990; Sih, 1980). This trade-off often limits the duration of predator-induced behaviour.…”

“…Previous studies showed that predation typically results in reduced activity across most taxa (Åbjörnsson et al, 1997;Ahlgren et al, 2011;Gall and Brodie, 2009;Huryn and Chivers, 1999;Kasumyan, 2022;Schäffer et al, 2013;Williams and Moore, 1982;Wisenden et al, 1997), although some, particularly Baetidae, also exhibited increased drift and movement (Culp et al, 1991;Lancaster, 1990;Poff et al, 1991). Similarly, studies found microcrustaceans either decreasing their activity (Bjaerke et al, 2016;Heuschele et al, 2020) or seeking refuge through vertical and horizontal migration (Jack et al, 2006;Lauridsen and Lodge, 1996;Pasternak et al, 2006;Zaret and Suffern, 1976). However, many of these studies focused on only a few select taxa with limited numbers of individuals, potentially obscuring density and biotic interaction effects (Peacor and Werner, 1997;Tollrian et al, 2015).…”