The effect of peritrich ciliates on the production of Acartia hudsonica in Long Island Sound

Abstract

We studied the effects of attached peritrich ciliates on the fitness of natural populations of Acartia hudsonica (Pinhey) in Stony Brook Harbor, Long Island Sound. Ciliate infection occurred during late spring, and ciliate load (No. ind.-') was not related to copepod age, stage, or body size. Simulated in situ experiments conducted throughout the period of abundance of A. hudsonica showed that egg production rate (No. d-l) was positively correlated to ambient water temperature, but negatively correlated to ciliate load. Salinity and the concentration of total or >8-10 pm Chl a were not significant in explaining the variation in egg production rate. Egg hatching success (O/o) was not influenced by the infection status (presence or absence) of the female. Infected nauplii had lower survival rates (d-l) compared to uninfected nauplii, but their developmental rates (molts d -I) were not significantly different. Significantly slower average sinking rates were found for infected adults compared to uninfected adults. Slower sinking rates for infected copepods may have been due to an increase in surface area which increased drag. Infected adults with slower sinking rates may be more susceptible to predation. Our findings show that peritrich ciliates can play a role in the seasonal decline and future recruitment of A. hudsonica.

Manipulation of Host Density Affects Infestation of a Peritrich Ciliate (Epistylis lacustris) on a Calanoid Copepod (Leptodiaptomus minutus) in Crystal Lake, Wisconsin, USA

“…This was not the case for the ciliate Rhabdostyla sp. which was more abundant on adult Acartia hudsonica than on the copepodites (Weissman et al 1993). Likewise, the ciliate Vorticelia microstoma exhibited higher infestation rates on longer Scapholeberis kingi, which was attributed to the fact that younger individuals grew and molted at a faster rate than older individuals (Henebry and Ridgeway 1979).…”

“…Herman and Mihursky (1964) reported that Acartia tonsa carried 25-200 Zoothaminium sp., and Weissman (1993) reported that Acartia hudsonica adults carried 1-300 Rhabdostyla sp., while copepodites and nauplii carried 1-100 ciliates per individual.…”

“…Infestation of copepods by these ciliates can affect copepod population dynamics in a variety of ways. For example, ciliate infestation can result in the production of lesions in copepod exoskeletons and can also increase a copepod's vulnerability to predators (Herman and Mihursky 1964, Turner et al 1979, Nagasawa 1988, Weissman et al 1993. Basic questions remain about this phenomenon, and it is unclear whether infestation by ciliates varies systematically with age, size, or density of the host species.…”

“…on the calanoid copepod Centropages abdominalis was low when the abundance of the copepod was high. Weissman et al (1993) found that ciliate load (number of ciliates per individual copepod) for the ciliate Rhabdostyla sp. was not proportional to age, stage, or body size of the calanoid copepod Acartia hudsonica, yet the proportion of individuals infested by the ciliate was positively related with copepod stage.…”

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“…Antifouling mechanisms should be beneficial if they reduce otherwise adverse effects by fouling organisms, e.g. increased energy expense for locomotion, damage of the body surface with increasing risk of infections, lower egg production, disruption of the moulting cycle (Glynn, 1970;Turner et al, 1979;Nagasawa, 1987;Xu & Burns, 1991;Weissmann et al, 1993).…”