Lernaeocera Lusci Research Articles

Lipid classes and fatty acid composition in two parasitic copepods Peroderma cylindricum and Lernaeocera lusci and their respective fish hosts Sardina pilchardus and Merluccius merluccius from the Tunisian waters

The present study investigates the detailed lipid classes and their fatty acid (FA) compositions from two parasitic copepods Lernaeocera lusci and Peroderma cylindricum and their respective fish host species Merluccius merluccius and Sardina pilchardus. The lipid classes, including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), triacylglycerol (TAG), wax ester/cholesterol ester (WE/CE), mono-diacylglycerol (MDG), and free fatty acids (FFA) were separated by thin layer chromatography. The results revealed that TAG and PC were the major lipid classes in parasites; while WE/CE and PS were the most abundant in hosts. As for FA composition, C16:0, C18:0, C18:1n-9, C20:5n-3, and C22:6n-3 were recurrently found to be dominant in all lipid classes of the different organisms studied. However, some differences concerning the abundance and the distribution of several FAs were observed. Overall, the obtained results highlighted that despite the quite strong trophic connection between the parasites and their respective hosts, the parasites could be distinguished by specific lipid profiles.

Polar and neutral lipid composition of the copepod Lernaeocera lusci and its host Merluccius merluccius in relationship with the parasite intensity.

Parasitic copepod Lernaeocera lusci is a common mesoparasite of the hake Merluccius merluccius. Although widely distributed throughout the Mediterranean, little is known about this pathogen. The current study was designed to assess the impact of different L. lusci infection loads on lipid classes and their fatty acid (FA) composition in both parasite and the host organs (gills, liver, and muscle). Results showed a significant decrease in total lipid, neutral lipid (NL), and polar lipid (PL) contents in all analyzed host's organs in relationship with parasite intensity. Gills appeared to be the most impacted organ under the lowest parasite intensity (loss of 50% of NL and PL amounts). At the highest parasitic infection, a loss of about 80% of lipid moieties was recorded in all analyzed organs. Simultaneously, no significant differences were found for the parasite reflecting its ability to sustain an appropriate lipid amount required for its survival and development. Significant changes in the FA composition were recorded in both host and parasite. Particularly, we have noticed that for L. lusci, the intraspecific competition has resulted in an increased level of some essential FA such as C22:6n-3 (docosahexaenoic acid, DHA), C20:5n-3 (eicosapentaenoic acid, EPA), and C20:4n-6 (arachidonic acid, ARA). This probably reflects that in addition to a direct host FA diversion, L. Lusci can modulate its FA composition by increasing the activity of desaturation. Within the host, liver PL appeared to be the less impacted fraction which may mirror an adaptive strategy adopted by the host to preserve the structural and functional integrity of this vital organ.

To what extent are hake fat and its oil quality affected by the parasite <em>Lernaeocera lusci</em>?

The copepod Lernaeosera lusci is a common ectoparasite of the hake Merluccius merluccius, which constitutes its definitive host. The present study is the first to investigate the impact of L. lusci and its infection intensity on the fatty acid (FA) composition and oil quality of its host. The results revealed a substantial decrease in the total FA content, which dropped by 50, 70 and 83% when fish was infected by one (L1), two (L2) and three (L3) parasites, respectively. The lipid profile showed a tendency for a significant decrease in the saturated fatty acid (SFA), monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) levels in all parasitized groups and in a parasite load dependant manner (p < 0.05). The same tendency was observed for the most commonly analysed FA and in particular for essential FA, such as e arachidonic (ARA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, which showed smaller amounts associated with L. lusci co-infection. From a nutritional standpoint, our findings revealed that L. lusci is able to cause severe deterioration in the nutritional quality of its host oil. In addition to the increase in the thrombogenicity index (IT) and the high atherogenicity index (IA) values, the low hypocholesterolemic / hypercholesterolemic fatty acid ratio (H/H) and the modest amount of DHA+EPA (20 and 10 mg/100g) recorded at heavy infection levels make the parasitized fish inadequate sources of these PUFA and unsuitable for consumers with special dietary needs.

English

The examination of 415 specimen belonging to twelve species of Teleostean fish and 339 specimen belonging to seven species of Chondrichthyan fish collected from the Tunisian coasts, it enabled us to identify 10 species of parasitic copepods: Lernaeopoda galei, Lernaeocera lusci, Neobrachiella merluccii, Hatschekia mulli, Caligus elongatus, Caligus pageti, Neobrachiella mugilis, Clavellotis fallax, Clavelissa pagri and Clavelissa scombri. The distribution of copepods identified, varies from one host species to another. Merluccius merluccius and Liza saliens present the important number of copepods species. The copepod Hatschekia mulli is the most abundant. The presence of Lernaeopoda galei on Scyliorhinus canicula, Mustelus mustelus and Mustelus punctalatus was reported for the first time in the southern banks of the Mediterranean. Key words: Copepods, Teleost fish, Chondrichthyan fish, Tunisian coasts, parasitic indices.

The egg string attachment mechanism of selected pennellid copepods

The anatomy of the hook apparatus that attaches egg strings to the fish parasites Haemobaphes cyclopterina, Lernaeocera branchialis, Lernaeocera lusci, Lernaeenicus sprattae, Sarcotretes scopeli and Pennella balaenoptera (Copepoda: Pennellida) is described and illustrated. The hook rises from a cupulate base, extending posteriorly and anteriorly in the body cavity. The suspension of the apparatus in the trunk of the different species differs, but the function is similar. The hook tip enters the genital antrum, nearly penetrates the proximal end of the egg string, and continues into a notch on the antrum wall. The apex of the egg string acquires a concave depression like the finger end of a glove. In this way the string is mechanically attached inside the female genital segment. The mobile ectoparasites Lepeophtheirus salmonis and Hatschekia hippoglossi have hooks which function similarly, but perforate the strings.

The suprapopulation dynamics ofLernaeocera branchialisandL. lusciin the Oosterschelde: seasonal abundance on three definitive host species

Quantitative samples of the demersal fish fauna of the Oosterschelde were taken between May 1988 and July 1989. The instantaneous mortality rates of the 1988 year classes of whiting (Merlangius merlangus L.), sand goby (Pomatoschistus minutus Pallas) and bib (Trisopterus luscus L.) were estimated at 0.017 d −1 , 0.014 d −1 and 0.018 d −1 , respectively. These three species were examined for the presence of mesoparasitic pennellid copepods. Combination of host population densities and parasite infection intensities allowed for estimation of parasite population densities. Whiting were infected with Lernaeocera branchialis shortly after their arrival (April-May) in the Oosterschelde. By the end of the year approximately 80% of the first year class whiting were infected. Spawning sand gobies were infected with Lernaeocera lusci in May and June. Though the prevalence of L. lusci on juvenile sand gobies in autumn was low, the parasite population density in this period was high. First year class bib were mainly infected by L. lusci after their transition from a pelagic to a demersal behaviour in August. It is suggested that L. branchialis has one generation each year, whereas L. lusci has two. A biological model of the life cycle of both parasite species is presented.

The distribution and abundance of Lernaeocera lusci (Copepoda) on hake ( Merluccius merluccius) and bid ( Trisopterus luscus) (Teleostei)

Distribution patterns, mean intensity and prevalence of Lernaeocera lusci (Copepoda, Pennellidae) in its 2 hosts Trisopterus luscus (Teleostei, Gadidae) and Merluccius merluccius (Teleostei, Merlucciidae) were examined, together with parasitic abundance and aggregation in relation to the size of the host. The mean parasite abundance and the variance to mean abundance ratio increased with host size, suggesting that the accumulation of this parasite had no noticeable impact on the structure of either host population. Merluccius merluccius being a newly colonized host in the Mediterranean, these results are discussed in relation to current ideas on the evolution of pathogenicity in heterospecific associations.

Morphological and morphometric study of crustacean parasites within the genus Lernaeocera

Two species of Lernaeocera are present in the southeastern North Sea. Lernaeocera lusci infects bib Trisopterus luscus, dragonet Callionymus lyra and sand goby Pomatoschistus minutus. L. Minuta is a junior synonym of L. lusci. The second valid species, L. branchialis, infects whiting Merlangius merlangus. The two species can be morphologically separated by the antennary processes, which are present in L. lusci and absent in L. branchialis. Discriminant functions allow complete separation between L. lusci and L. branchialis. There is high intraspecific, host-dependent variability within L. lusci. Length of L. lusci is significantly influenced by host size, and body form is influenced by the site of attachment of L. lusci on at least one host (bib). It is suggested that L. lusci consists of 3 forms: f. lusci, f. minuta and f. lyra.

Infection dynamics of Lemaeocera lusci on sand goby Pomatoschistus minutus in the Oosterschelde (The Netherlands)

Male and female sand gobies Pomatoschistus minutus (Pallas) from the Oosterschelde (The Netherlands) were examined for the crustacean mesoparasite Lernaeocera lusci (Bassett-Smith) from Apnl to July 1992. Prevalence increased steeply from 4 % in Apnl to 80% (females) and 57 % (males) in June. The peak abundance of recently attached infective stages (pennella larvae) on sand gobies was found in May. By June, about 70% of parasites were in the post-metamorphosis stage and possessed egg strings. Significant differences in abundance between males and females were found in June but not in May. This may be due to sex-specific differences in behaviour during spawning time. The majority of post-spawning fish probably d ~ e d in July. Fish of the new year class which were captured in July harboured no parasites.

Pathogenicity of Lernaeocera lusci and L. branchialis in bib and whiting in the North Sea

Pathogenicity of Lernaeocera lusci and L. branchialis in bib and whiting in the North Sea

Biodiversity and biogeography in heterospecific teleostean (Gadidae) – copepod (Lernaeocera) associations

This genetic study confirms the validity of two controversial parasite species, Lernaeocera branchialis and Lernaeocera lusci (Copepoda, Pennellidae). These species cohabit throughout a large sector of the North Sea and the Atlantic Ocean, parasitizing Merlangius merlangus and Trisopterus luscus (Teleostei, Gadidae), respectively. In the Mediterranean Sea, it was L. branchialis that was described initially. We have shown, however, that it is L. lusci that parasitizes T. luscus and Merluccius merluccius in this geographical area. The distribution of L. lusci, as well as that of its host, T. luscus, must extend into the Mediterranean. Lernaeocera lusci has colonized a phylogenetically distant host (Merluccius merluccius) in the Mediterranean and our results show that this species has become the preferred host for the maturation of L. lusci in this region. In addition, we have demonstrated the existence of genetic differentiation between T. luscus from the Atlantic and from the western Mediterranean. Thus, it is possible that the specialization of L. lusci in a new resource (M. merluccius) in the Mediterranean might be related to biological changes undergone by this copepod's original host, Trisopterus luscus. In contrast to other parasite groups such as the Monogenea, the specialization of species of the genus Lernaeocera would appear to depend more on ecological parameters (relative abundance and availability of resources) than on phylogenetic constraints. The relationships within these host–parasite systems are therefore compared with the predator–prey relationships.

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)

A survey of the dragonet Callionymus lyra and the reticulated dragonet C. reticulatus from Belgian coastal waters (Southern Bight of the North Sea) in June 1991 revealed 34% of dragonets infected with 1–7 Lernaeocera lusci. This same parasite infected 9% of the reticulated dragonets (mean intensity =1). Parasite size is host‐size‐dependent. Of the parasites collected from C, lyra 64% were gravid adults (substage X), and a significant positive relationship between the number of eggs and axial length of the parasite was found. The parasites were overdispersed within the dragonet population (s2/m=1.67)

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

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

Some aspects of the infection of bib, Trisopterus luscus (L.), by the parasitic copepod Lernaeocera lusci (Basset‐Smith, 1896) in Portuguese waters

Winter samples totalling 2308 specimens of Trisopterus luscus (total length range: 13–36 cm) caught in northern Portugal were examined for infections with Lernaeocera lusci. Infection prevalence was of 42%, and infection intensity was 1.7 copepods per infected fish. Individual infection varied between 1 and 9 copepods per infected specimen; 30.6% of the fish had bilateral parasitosis. There was a significant correlation (P<0.01) between fish length and prevalence. Length‐weight relationships of uninfected and infected fish were not significantly different (P > 0.05) and thus provide evidence that L. lusci has no effect on the condition of T. luscus in all the examined 1–cm size classes.