Population Biology of Camallanus oxycephalus Ward and Magath, 1916 (Nematoda: Camallanidae) in White Bass in Western Lake Erie

Abstract

The distribution and abundance of the nematode Camallanus oxycephalus infecting white bass, Morone chrysops, in western Lake Erie was studied for over 2 years. Infection was generally more frequent and of higher intensity in large fish. The frequency distributions of nematode abundance in all segments of the fish population followed the negative binomial distribution. The data show seasonal cycles in population structure, site selection, intensity of infection, maturation, and reproduction. Infection occurs during July and August with a resulting peak in population density; during late summer and autumn, mortality, probably density-dependent, reduces the population by 30 to 60%; surviving worms are eliminated at 1 year of age. Growth and development of female worms is arrested from November to April, then proceeds at a rapid rate until the worms release their larvae and die. This growth pattern is probably related to temperature but may also involve host hormone cycles. The dispersal period of the nematode coincides with the annual maximum density of the intermediate host, a cyclopoid copepod,and is interpreted as an adaptation which increases the probability of successful transmission. Because the number of larvae produced by each female worm is a function of body volume, natural selection has favored rapid spring growth and attainment of large body size relative to the male worm. Both seasonal timing in the life cycle and the number of larvae produced are important factors in determining the abundance of this and perhaps other parasites. Evidence is presented suggesting that fluctuations of environmental parameters may disrupt the timing of transmission and alter the distribution and abundance of the parasite. It is hypothesized that the magnitude of such changes in parasite abundance may be related to the complexity of the host-parasite system.

Camallanus maculatus n. sp. (Nematoda: Camallanidae) in an ornamental fish Xiphophorus maculatus (Osteichthyes: Poeciliidae) cultivated in São Paulo State, Brazil

“…The high prevalence rate from this study was similar to Camallanus oxycephalus Ward andMagath, 1916 (Stromberg andCrites, 1975), Camallanus sp. (Lyan and Seng, 1979), Camallanus corderoi Torres, Teuber andMiranda, 1990 (Torres et al, 1990) and Camallanus cotti Fujita, 1927 (Font andTate, 1994;Rigby et al, 1997;Kim et al, 2002).…”

Population Dynamics of Fasciola gigantica in Cattle Slaughtered in Uyo, Nigeria

“…A number of natural host^parasite systems exhibit such high variance/mean ratios (Fuller, 1996;Opara, 2002). According to Stromberg and Crites (1975), environmental £uctuations that produce small shifts in the temporal or spatial overlap of host and parasite might exert a regulatory e¡ect upon the parasite population and so alter the parasite's abundance in the de¢nitive host. Owing to the public health and economic importance of fasciolosis, there is a need for more practical approaches to its control to alleviate the burden of this disease on its cattle host and reduce economic losses.…”

The role of zooplankton in the transmission of helminth parasites to fish

“…Aggregation of infected copepods may enhance transmission to fish. Maximum densities of cyclopoid intermediate hosts often occur synchronously with eestode and nematode reproduction in fishes (Stromberg and Crites, 1975a;Riggs and Esch, 1987).…”