Life cycle of a sea louse, Caligus elongatus von Nordmann, 1832 (Copepoda, Siphonostomatoida, Caligidae)

Abstract

Caligus elongatus, known as a sea louse, is a very important pathogen of sea-farmed Atlantic salmon (Salmo salar). The life cycle of C. elongatus was examined under laboratory conditions. The observations were made at 10 °C, with ambient photoperiod. Small Arctic char (Salvelinus alpinus) kept in full-salinity seawater were used as experimental host fish. They were infected individually by offspring of several C. elongatus females. The hosts were killed at consecutive time periods after infection and developmental stages of the parasite were recovered. The life cycle consists of 8 stages: 2 nauplii, 1 copepodid, 4 chalimi, and adult. A separate preadult stage does not occur. The copepodid is infective and all subsequent stages live on fish. The time at which a particular stage is attained by 50% of individuals in a cohort (T50) was as follows: chalimus I, 7.1 days post infection (dpi); chalimus II, 11.4 dpi; chalimus III, 14.0 dpi; chalimus IV, 17.6 dpi; adult, 24.7 dpi. The generation time was 43.3 days. The females can lay eggs at least twice. The males die after copulation (38–54 days after hatching). Overwintering females show signs of diapause.

Diseases, prophylaxis and treatment of the Atlantic halibut Hippoglossus hippoglossus: a review

“…The most extensively studied species is C. elongatus, a species with a broad range of hosts, which has been reported from more than 80 different species (Kabata 1979). The lifecycle of C. elongatus is similar to L. salmonis with the exception that C. elongatus lacks the pre-adult stages (Piaseki & McKinnon 1995). Kabata (1979) listed Atlantic halibut as one of the hosts for C. curtus but, so far, this species has not been recorded on farmed halibut.…”

Ectoparasitic sea lice (Lepeophtheirus salmonis and Caligus elongatus) infestations of wild, adult, one sea-winter Atlantic salmon Salmo salar returning to Scotland

“…Initially, Caligus elongatus was the only major pest caligid to the Atlantic salmon farming industry in E Canada (Piasecki & MacKinnon 1995), and Hogans & Trudeau (1989) reported C. elongatus at prevalences up to 100%, compared to Lepeophtheirus salmonis at a maximum of only 8%. In recent years, however, L. salmonis has become the primary pest species, just as it is in the Atlantic salmon farming industry in both Europe (e.g.…”

“…= 0.835 to 0.948), indicating a marked differential longevity of males and females on wild fish. Piasecki & MacKinnon (1995) found that male C. elongatus (infesting experimental char Salvelinus alpinus) die soon after copulation. None of the independents here analyzed by stepwise regression (Table 2) correlated significantly with variation in the proportion of female C. elongatus amongst individual fish; but if male postcopulatory death is typical of C. elongatus on wild salmon, then this alone could explain the extreme female bias.…”

“…Wild post-smolt Salmo salar can acquire chalimi within days of first entering seawater (Finstad et al 2000), but the adult lice burdens of return migrant 1SW and 2SW salmon, captured some 12+ or 24+ mo later, are most unlikely to be survivors of initial infestation (Todd et al 2000). Post-settlement development from the infective, planktonic copepodid larva to the final sessile (chalimus C IV) larval stage can take up to 270 degree-days post infection (ddpi) for Caligus elongatus (Piasecki & MacKinnon 1995) or 350 ddpi for L. salmonis (Johnson & Albright 1991). At oceanic spring/early summer temperatures, our fish carrying pre-adult L. salmonis will have been most recently infected 4 to 6 wk before capture.…”

An Annotated Species List of Parasites Found in European Smelt Osmerus Eperlanus (L.)

“…Males die after copulation. Females overwinter [Piasecki and MacKinnon, 1995]. Two mitochondrial genotypes have been described for Caligus elongatus Nordman in Norway [Øines and Heuch, 2007].…”