The infection dynamics and dispersion pattern of Lernaeocera branchialis L. on 0+ whiting (Merlangius merlangus L.) in the Oosterschelde (SW Netherlands)

Abstract

Size and structure of the Lernaeocera branchialis population infecting O+ whiting in the Oosterschelde were studied during 1989. Two periods of successful transmission were distinguished. The first transmission wave occurs in late spring when the post-larval whiting enter the Oosterschelde. A second wave occurs in autumn. This pattern in the infection dynamics is possibly related to seasonal variations in spatial overlap of the intermediate (Platichthysflesus) and the final host (Merlangius merlangus). The dispersion pattern of Lernaeocera branchialis within the whiting population can bedescribed by the Poisson distribution. Possibleexplanations for the observed dispersion pattern are given. Evidence is presented that the rejection of pennella larvae is a key mechanism determining the abundance of L. branchialis in whiting. The potential impact of parasite-induced host mortality on population size and dispersion pattern of the parasite is discussed.

The population dynamics ofLernaeocera lusci andL. branchialis on intermediate hosts

“…It is highly probable that the whiting 1Vlerlangius merlangus fulfills this role in the Oosterschelde. Van Damme & Hamerlynck (1992) observed that more than 50 % of the 0+ whitings in this area are infected with L. branchialis. In offshore areas, other gadids such as cod Gadus morhua may also play a significant role.…”

“…His hypothesis is corroborated in the present study: the highest abundance of L. branchialis in the Oosterschelde was found in April and the adult females left the intermediate host en masse after June (Table 3). First-year whiting which enter the Dutch delta in early spring probably act as definitive host for the female L. branchialis which detach from flounders (Van Damme & Hamerlynck, 1992), Thus, L. branchiafis probably has only one generation each year: recruitment of infective stages (copepodites) on flounders probably occurs in winter, whereas transmission to the definitive host occurs in summer. Similar observations were made by Kabata (1958)…”

“…In the southern North Sea, the typical definitive host species are bib (for L. lusci) and whiting (for L. branchiafis). The population dynamics of both parasites on their definitive host species were recently studied in the Dutch coastal area (Van Damme & Hamerlynck, 1992;Van Damme et al, 1996).…”

The population dynamics of the parasitic copepodeLernaeocera lusci (Bassett-Smith, 1896) on its definitive host

“…The adult females of L. lusci were classified according to a nomenclature proposed by Van Damme & Hamerlynck (1992), which is a modification of the staging system initially proposed by Sproston & Hartley (1941). Table 1 summarizes the diagnostic characters of the substages.…”

The role of Callionymus lyra and C. reticulates in the life cycle of Lernaeocera lusci in Belgian coastal waters (Southern Bight of the North Sea)

“…The skin, mouth cavity and gill cavity of the fish were checked for crustacean parasites. The staging of the adult female L. lusci on the hosts was based on the nomenclature of Van Damme & Hamerlynck-(1992), which is a modification of the staging system ofSproston & Hartley (1941). A summary of the diagnostic characters of each substage is given in Table I.…”