The parasites of Pacific halibut (Hippoglossus stenolepis) in the eastern North Pacific: host-level influences

Abstract

Fifty-nine metazoan parasite taxa were identified from 536 Pacific halibut (Hippoglossus stenolepis) of three size classes (recruits (<10 cm), juveniles (10-55 cm), and subadults/adults (55-102 cm)). Pacific halibut harbor parasite communities that are among the richest and most abundant found in those marine fishes studied to date. The parasites are largely host generalists, being found in a wide variety of marine fishes. These three features appear to be due, in part, to the interplay of the large size, wide diet, extensive mobility, and long life-span of halibut, plus the lack of specificity in the marine system and the ability of marine parasites to be transferred trophically from prey fishes to piscivorous fishes. The parasite community in halibut is more similar to those in other flatfishes than to those in ecological analogs, suggesting that phylogeny is an important determinant as well. There are no differences in infections due to host sex. Recruits harbor few parasites, but parasite species and particularly individuals accumulate with host age and length and reflect the shift from a crustacean to a fish diet. Growth rate influences the number of parasite individuals in a given fish, probably reflecting food intake. The smallest fish in the 5-, 6-, and 7-year age-classes have more parasite individuals than slightly larger fish in the same age-class and weigh less than expected for their size; they may be debilitated by parasites.Résumé : Cinquante-neuf taxons de métazoaires parasites ont été identifiés chez 536 Flétans du Pacifique (Hippoglossus stenolepis) de trois classes de taille (recrues (<10 cm), juvéniles (10-55 cm), et subadultes/adultes (55-102 cm)). De tous les poissons marins étudiés à ce jour, les Flétans du Pacifique supportent l'une des communautés les plus riches et les plus abondantes de parasites. Les parasites identifiés sont en grande partie des généralistes trouvés chez une grande variété de poissons marins. Cette situation semble en partie attribuable à l'interaction de la grande taille, du régime alimentaire généraliste, de la mobilité importante et de la longévité particulièrement grande du flétan, en plus de l'absence de spécificité dans le système marin et de la transmission des parasites le long de la chaîne trophique, des poissons proies aux poissons piscivores. La communauté de parasites du flétan est plus semblable à celles des autres poissons plats qu'à celles de ses analogues écologiques, ce qui semble indiquer que la phylogénie joue aussi un rôle déterminant. Les infections ne sont pas reliées au sexe de l'hôte. Les recrues portent peu de parasites, mais le nombre d'espèces et encore plus le nombre d'individus augmentent avec l'âge et la longueur de l'hôte et reflètent le passage d'un régime alimentaire de crustacés à un régime constitué de poissons. Le taux de croissance influence le nombre de parasites chez un poisson donné, probablement en fonction de la quantité de nourriture consommée. Les petits poissons des classes d'âge 5, 6, et 7 ans portent un plus grand nombre d...

Pseudopecoelus mccauleyi n. sp. and Podocotyle sp. (Digenea: Opecoelidae) from the deep waters off Oregon and British Columbia with an updated key to the species of Pseudopecoelus von Wicklen, 1946 and checklist of parasites from Lycodes cortezianus (Perciformes: Zoarcidae)

“…possesses vitelline follicles that do not extend anterior to the ventral sucker (follicles extend as far as the posterior margin of the ventral sucker), a long, slender body (neither fusiform nor wide), no papillae on the lips of the ventral sucker, lobed testes, and vitelline follicles that are interrupted opposite the gonads. With these features, the new species is closest to Pseudopecoelus nossamani, described from the Pacific halibut, Hippoglossus stenolepis Schmidt, 1904 (Pleuronectidae), from the Bering Sea (Kruse 1977; see also Blaylock et al 1998), and to Pseudopecoelus holocentri Nahhas and Cable, 1964, described from the squirrelfish, Holocentrus adscensionis (Osbeck, 1765) (Holocentridae), from off Curaçao in the Caribbean Sea (Nahhas and Cable 1964) (see our Table I, couplet #31 in key of Madhavi and Lakshmi 2010). While the new species has a sucker ratio that overlaps that of P. nossamani and P. holocentri (1:1.62-2.83 vs 1:1.72 and 1:2.00-2.15), the egg size of P. macauleyi n. sp.…”

Tracking the assembly of nested parasite communities: Using β‐diversity to understand variation in parasite richness and composition over time and scale

“…For example, within parasite community ecology, the use of multiple, alternative sets of terminologies to describe assembly have led to both confusion and a disconnect from community ecology generally. For instance, parasitologists may refer to parasites as being limited by ‘encounter filters’ or ‘compatibility filters’ (Combes, 2001) or evaluate the role of ‘host‐level’ processes such as host age, sex or body size in driving community composition (Blaylock, Holmes, & Margolis, 2011). Yet mechanistically such traits can affect community composition through dispersal (e.g.…”

Mesopredatory fishes from the subtropical upwelling region off NW-Africa characterised by their parasite fauna

“…The larval tetraphyllidean cestode morphotaxon Scolex pleuronectis was previously recorded, but no peer-reviewed parasitological studies on N. tripes have been published. The bile ducts and gall bladder as sites of infection for tetraphyllidean cestode larvae have been observed in other fish species (e.g., Hippoglossus stenolepis , Blaylock, Holmes & Margolis, 1998 ) and are identified in N. tripes for the first time. Many aspects of the life-cycle of tetraphyllidean cestodes are still unknown, but most species have elasmobranch definitive hosts ( Marcogliese, 1995 ).…”