The copepod Centropages abdominalis as a carrier of the stalked ciliate Zoothamnium

Abstract

Adult specimens of the calanoid copepod Centropages abdominalis collected from February through April 1986 in Shinhamako, a saline lake connected to Tokyo Bay, were heavily infested with the stalked ciliate Zoothamnium. The number of copepods and those infested varied during the infestation period; in February when the copepod population was large, the incidence of infestation was low, whereas in March when the copepod population was small, copepods infested with Zoothamnium were proportionally more abundant. Numerical variations of infested copepods may correspond to changes in the Zoothamnium population. No specimens of Acartia omorii, which coexists with C. abdominalis, were infested in 1986, although a small number of A. omorii were infested with peritrich ciliates in 1985. Some shrimp larvae were also covered with the same peritrichs as copepods. Nevertheless, as a whole, the relationship between the phoront and its carrier seems to be specific. The highest incidence of infested copepods was approximately 30% similar to that in 1985. The sex ratio of C. abdominalis changed on each sampling date but in general females were more numerous than males. The percentage of infested males was higher than that of infested females, suggesting that the former can be attached to more easily than the latter.

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

“…This suggests that the ciliate can more easily locate and attach to its carriers at high L. Minutus density than when host copepods are lower in abundance. Our results differ from those of Nagasawa (1988) who reported that in saline Shinhamako Lake, the infestation rate of the stalked ciliate Zoothamnium sp. on the calanoid copepod Centropages abdominalis was low when the population density of the copepod in the lake was high.…”

“…Likewise, Zoothamnium sp. was found almost exclusively on the copepod Centropages abdominalis in Shinharnako (Nagasawa 1986(Nagasawa , 1988. The ciliate Vorticella microstoma was found exclusively on the cladoceran Scapholeberis kingi, although cladocerans Chydorous sphean'cus and Pleuroxis denticulatus were available as potential hosts in about equal numbers; a t the same time, a different ciliate, Epistylis plicatilis, was found on several copepod species, namely Eucyclops agilis, Cyclops vernalis, and C. bicuspida&s (~e n e b r~ and ICidgeway 1979).…”

“…Colonial or solitary stalked peritrich ciliates have been found living on the external surfaces of a wide variety of aquatic crustaceans in both marine (Herman and Mihursky 1964, Henebry and Ridgeway 1979, Turner et al 1979, Nagasawa 1988) and fresh waters (Weissman et al 1993, Threlkeld andWilley 1993). Infestation of copepods by these ciliates can affect copepod population dynamics in a variety of ways.…”

“…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.…”

“…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. Nagasawa (1988) reported that the infestation rate of the ciliate Zoothamnium sp. on the calanoid copepod Centropages abdominalis was low when the abundance of the copepod was high.…”