The histopathology of infection by Lepeophtheirus pectoralis (Müller) (Copepoda: Caligidae)

The histology of the pectoral fin of the flounder, Platichthys flesus. (L.), is described and the presence of eosinophilic granule cells in the epidermis was noted. The histopathological effects of infection by L. pectoralis result from the attachment and feeding activity of the parasite. Although the damage inflicted by L. pectoralis is usually confined to the epidermis the lesions caused by sessile life cycle stages, adult females and chalimus larvae, often extend into the dermis. In the dermis the inflammatory response comprised fibroplasia and cellular infiltration which resulted in the formation of a dense fibrous granulation tissue.     

A model for studying isolation mechanisms in parasite populations: the genus Lepeophtheirus (Copepoda, Caligidae)

In the Mediterranean, the parasitic copepod Lepeophtheirus thompsoni Baird, 1850 specifically infests turbot (Psetta maxima L., 1758), whereas L. europaensis Zeddam, Berrebi, Renaud, Raibaut, and Gabrion, 1988 infests brill (Scophthalmus rhombus L., 1758) and flounder (Platichthys flesus L., 1758). Experimental infestation of turbot by copepods from each of the three fish species showed an absence of any physiological incompatibility preventing natural development of the two parasite species, at least on one host species, i.e., the turbot. Moreover, interspecific hybrids were obtained experimentally, which implies that 1) there is no strict genetic barrier between the two species and 2) the natural prezygotic isolation results from a choice of the most favorable habitat. We discuss the origin and possible consequences of the presence, in the Mediterranean, of L. europaensis on brill and flounder, two hosts separated by their taxonomic status and ecobiology.     

The settlement and attachment of early stages of the salmon louse, Lepeophtheirus salmonis (Copepoda: Caligidae) on the salmon host, Salmo salar

A study was undertaken of the settlement and attachment of larvae of Lepeophtheirus salmonis (Krøyer, 1837) on a salmonid host Salmo salar Linnaeus, 1758. Preferred settlement sites were the fins and other protected areas. Initial, reversible settlement was followed by attachment with the hooked second antennae. The filament used for subsequent attachment was found to comprise three distinct regions; basal plate, stem and external lamina. The filament was secured to the epithelial basement membrane by the basal plate which was formed by secretion down the axial duct from the posterior A-group of cells. The stem was fibrous and carried the axial duct along its length. A thin external lamina covered the stem and was apparently continuous with the chalimus cuticle. A number of filament-associated organs are also described, comprising cell groups A-C although only the function of A was characterized.     

Exocrine glands of Lepeophtheirus salmonis (Copepoda: Caligidae): Distribution,developmental appearance,and site of secretion

Exocrine glands of blood‐feeding parasitic copepods are believed to be important in host immune response modulation and inhibition of host blood coagulation, but also in the production of substances for integument lubrication and antifouling. In this study, we aimed to characterize the distribution of different types of salmon louse (Lepeophtheirus salmonis) exocrine glands and their site of secretion. The developmental appearance of each gland type was mapped and genes specifically expressed by glands were identified. Three types of tegumental (teg 1–3) glands and one labial gland type were found. The first glands to appear during development were teg 1 and teg 2 glands. They have ducts extending both dorsally and ventrally suggested to be important in lubricating the integument. Teg 1 glands were found to express two astacin metallopeptidases and a gene with fibronectin II domains, while teg 2 glands express a heme peroxidase. The labial glands were first identified in planktonic copepodids, with reservoirs that allows for storage of glandular products. The last gland type to appear during development was named teg 3 and was not seen before the preadult I stage when the lice become more virulent. Teg 3 glands have ducts ending ventrally at the host‐parasite contact area, and may secrete substances important for the salmon lice virulence. Salmon lice teg 3 and labial glands are thus likely to be especially important in the host‐parasite interaction. Proteins secreted from the salmon louse glands to its salmonid host skin or blood represents a potential interface where the host immune system can meet and elicit effective responses to sea lice antigens. The present study thus represents a fundamental basis for further functional studies and identification of possible vaccine candidates. J. Morphol. 277:1616–1630, 2016. © 2016 Wiley Periodicals, Inc.     

New insights into the larval development of Macandrevia cranium (Müller, 1776) (Brachiopoda: Rhynchonelliformea)

The terebratulid Macandrevia cranium (Müller, 1776) is a representative of articulate brachiopods. However, little is known about its embryology and larval development. In order to obtain reproducible results we used a strict protocol of artificial fertilization under controlled temperature conditions as a basis for our morphological study. Sampling of embryos or developing larvae at frequent intervals led to the most comprehensive collection of preserved developmental stages, ranging from early zygotes to late three-lobed stage larvae. SEM studies of all these stages showed that the development of M. cranium is similar to that of other terebratulid brachiopods. This includes the presence of four bundles of larval setae in three-lobed stage larvae. Our results contradict earlier observations on the development of M. cranium and show that this species exhibits more typical features of articulate brachiopod development than previously thought.     

The discovery of Lepeophtheirus lichiae Barnard, 1948 (Copepoda: Caligidae) parasitic on leerfish,Lichia amia (Linnaeus) in the Mediterranean Sea

Systematic Parasitology - Lepeophtheirus lichiae Barnard, 1948 (Copepoda: Caligidae), a very rare and poorly known sea louse, is redescribed based on a single newly collected female. The specimen...     

Host specificity of Lepeophtheirus crassus (Wilson and Bere) (Copepoda: Caligidae) parasitic on the marlin sucker Remora osteochir (Cuvier) in the Atlantic Ocean

Three species of remoras--Remora brachyptera (Lowe), Remora osteochir (Cuvier), and Remora remora (Linnaeus)--were collected from 4 species of billfishes--Istiophorus platypterus (Shaw), Makaira nigricans Lacepéde, Tetrapturus albidus Poey, and Tetrapturus pfluegeri Robins and de Sylva--on board a Japanese long-liner Shoyo Maru during her cruise in 2002 across the Atlantic. However, only the marlin sucker (R. osteochir) was found to carry a parasitic copepod, Lepeophtheirus crassus (Wilson and Bere, 1936). Although 12 species of parasitic copepods have been reported from billfishes around the world ocean, none of them is L. crassus. Thus, L. crassus is considered a parasite specific to the marlin sucker.     

Two new species of Lepeophtheirus (Copepoda: Caligidae) parasitic on fishes from southern California waters.

Two new species of Lepeophtheirus are described and illustrated based on a collection from the Orange County sewer outfall, California. They are: L. remiopsis sp.nov. from the branchial cavities and external body surfaces of Parophrys vetulus Girard, Hippoglossina stomata Eigenmann & Eigenmann, Pleuronichthys verticalis (Jordan & Gilbert), Chitonotus pugetensis (Steindachner), and Porichthys notatus (Girard); and L. rotundipes sp.nov. from the external body surfaces and occasionally the gill cavities of Scorpaena guttata (Girard) and Citharichthys stigmaeus Jordan & Gilbert.     

Seasonal dynamics of the acanthocephalan Pomphorhynchm laevis (Müller, 1776) in its intermediate and preferred definitive hosts

No seasonal cycle was found in either the prevalence or the intensity of natural Pomphorhynchus laevis infections in Leuciscus cephalus . There was a slight seasonal change in female maturity distribution but only irregular fluctuations in the size structure of the adult parasite population throughout the year. Cystacanths were available in all seasons. Rates of parasite growth, maturation and mortality, but not establishment, increased with water temperature (or factors indirectly associated with elevated water temperature) in laboratory-infected Salmo gairdneri . Increased rates of parasite growth and maturation mask any marked shifts in the size and maturity structure of the adult parasite population which might otherwise be due to the higher turnover of adult parasites in the summer months.     

The occurrence of Lepeophtheirus salmonis and Caligus clemensi (Copepoda: Caligidae) on three-spine stickleback Gasterosteus aculeatus in coastal British Columbia

Infections with sea lice species belonging to Lepeophtheirus and Caligus are reported from examinations of 1,309 three-spine sticklebacks collected in coastal British Columbia. Over 97% of the 19,960 Lepeophtheirus specimens and nearly 96% of the 2,340 Caligus specimens were in the copepodid and chalimus developmental stages. The parasites were identified as Lepeophtheirus salmonis and Caligus clemensi based on morphology of adult stages. Between 1,763 and 1,766 base pairs (bp) of 18S rDNA from adult specimens collected from sticklebacks and salmon differed from the GenBank L. salmonis reference sequence by a single bp and were distinct from those of 2 other Lepeophtheirus species. A 530-bp region of 18S rDNA from chalimus stages of Lepeophtheirus obtained from sticklebacks and salmon was identical to that of the L. salmonis reference sequence. The three-spine stickleback is a new host record for L. salmonis. The prevalence of L. salmonis was 83.6% and that of C. clemensi was 42.8%. The intensities of these infections were 18.3 and 4.2, respectively. There was no significant relationship between sea lice abundance and stickleback condition factor. Significant spatial and temporal variations both in abundance of sea lice and surface seawater salinities were measured. The abundance of both sea lice species was lowest in zones in which surface seawater salinity was also lowest. Sticklebacks appear to serve as temporary hosts, suggesting a role of this host in the epizootiology of L. salmonis. The stickleback may be a useful sentinel species with which to monitor spatial and temporal changes in the abundance of L. salmonis and C. clemensi.     

Observations on the distribution, specificity and pathogenicity of the acanthocephalan Pomphorhynchus laevis (Müller)

The distribution, specificity and pathogenicity of the acanthocephalan Pomphorhynchus laevis (Müller) were studied in the River Avon, Hampshire. The parasite occurred in every fish species, but three categories of hosts could be distinguished. Using growth and maturation as criteria of specificity, only chub Leuciscus cephalus (L.) and barbel Barbus barbus (L.) were recognized as its preferred hosts. Parasites occasionally matured in trout Salmo trutta (L.) and dace Leuciscus leuciscus (L.), but none grew or matured in other host species. Changes in the abundance of P. laevis along the river were related to changes in the abundance of both the intermediate host, Gammarus pulex , and the preferred hosts, and its occurrence in fish to the importance of G. pulex in their diet. In the upper reaches of the River Avon and in other localities populations could be maintained at a low level by parasites maturing in trout, and presence and abundance at any site depended upon the presence and abundance of both intermediate and definitive hosts especially and upon the dietary preferences of the latter. The absence of P. laevis from many parts of Britain is nevertheless still inexplicable. The parasite caused local damage to the intestinal wall of fish, the extent of which varied from species to species, but did not affect host growth rate or cause direct mortality and P. laevis cannot be regarded as an important pathogen in the River Avon or any other British River.     

Annual changes in the population size of the salmon louse Lepeophtheirus salmonis (Copepoda: Caligidae) on high-seas Pacific Salmon (Oncorhynchus spp.), and relationship to host abundance

The population size of the salmon louse, Lepeophtheirus salmonis, was monitored annually in the summers of 1991–1997 by examining six species of Pacific salmon (Oncorhynchus spp.) caught by surface long-lines in oceanic offshore waters of the North Pacific Ocean and Bering Sea. The annual copepod population size on all salmonids caught was estimated by combining the calculated number of copepods carrying on each salmonid species. The copepod population fluctuated markedly from year to year, which resulted largely from marked annual changes in abundance of pink salmon (O. gorbuscha). Since pink salmon were most frequently and heavily infected and since their abundance changed every year, the copepod population was high in the years when this salmonid species was abundant, but low when it was rare. On the contrary, chum salmon (O. keta) did not show high prevalence and intensity of infection, but the annual abundance of this host species was consistently high, i.e. chum salmon carried many copepods every year. Copepods on other salmonid species (sockeye salmon O. nerka, coho salmon O. kisutch, chinook salmon O. tshawytscha, and steelhead trout O. mykiss) constantly formed a small percentage of the total copepod population. Both chum and pink salmon are the most important hosts in terms of their substantial contribution to support the copepod population, but the importance as hosts of each species is definitely different between the species. Chum salmon is a stable important host supporting the copepod population at a relatively high level every year, while the number of copepods on pink salmon annually exhibits marked fluctuations, and this salmonid species is regarded as an unstable important host.     

The osmotic response of salmon louse,Lepeophtheirus salmonis (Copepoda: Caligidae), during the transition from sea water to fresh water

Summary The osmotic changes in haemolymph and body tissues of the ectoparasitic salmon louse,Lepeophtheirus salmonis, have been studied upon transfer from sea water (SW) to dilute sea water (37% SW), and then to fresh water (FW). The parasite shows osmoconformity in SW but hyperosmotic regulation in 37% SW regardless of whether it is attached to the salmon host or free swimming in the water. The same conclusion is reached by haemolymph Cl^– measurements. In FW, the osmotic tolerance and response of attached and free swimming parasites differ: Attached animals maintain steady haemolymph osmolality and Cl^– concentration and survive for at least 1 week, while free swimming parasites quickly become diluted and start to die within 8 h.Acclimation to 37% SW is accompanied by changes in body tissue water content and in the content of ninhydrin positive substances and specific amino acids which suggest the presence of cell volume regulation. Glycine is the dominating free amino acid in the cephalothorax tissues but alanine, proline and taurine also occur in high amounts. Lysine is found to increase significantly during FW acclimation of attached parasites. A breakdown of cell volume regulation is suggested to limit the survival of attached salmon louse in fresh water.Abbreviations FW fresh water - NPS ninhydrin positive substances - SW sea water     

The abundance and distribution of Lepeophtheirus salmonis (Copepoda: Caligidae) on pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon in coastal British Columbia

In total, 23,750 specimens of the salmon louse, Lepeophtheirus salmonis, were collected from 3,907 juvenile pink and 3,941 chum salmon caught within the Broughton Archipelago during a 2-yr survey. The prevalence on pink salmon was significantly higher than on chum salmon in 2004 (62.3% and 58.6%, respectively) and in 2005 (26.4% and 23.1%, respectively). The mean abundance on chum salmon was significantly higher than on pink salmon in 2004 (7.0 +/- 0.3 and 2.8 +/- 0.2, respectively), whereas in 2005 the mean abundance did not differ between species (0.6 +/- 0.1 and 0.5 +/- 0.0, respectively). The mean intensity on chum salmon was significantly higher than on pink salmon in 2004 (12.0 +/- 0.4 and 4.5 +/- 0.2, respectively) and in 2005 (2.5 +/- 0.2 and 1.7 +/- 0.1, respectively). The prevalence, intensity, and abundance of L. salmonis were significantly higher on salmon belonging to both host species in 2004 compared with 2005. In both years, a majority of pink and chum salmon had 2 or fewer lice. In general, a decline in abundance of L. salmonis over the 3 collection periods in each year coincided with an increased percentage of motile developmental stages. The abundance was lowest on fish collected from zones in which the seawater surface salinity was also lowest. Seawater surface temperature was higher and salinity was lower in 2004 compared with 2005. The spatial and temporal trends in the abundance of L. salmonis in relation to host size, infestation rates, and seawater salinity and temperature, evident in both years, must be considered in future studies assessing the role of farmed salmon in the epizootiology of this parasite on juvenile salmon in this area.     

Aerobic scaling and resting metabolism in oviferous and post-spawning Barents Sea capelin Mallotus villosus villosus (Müller, 1776)

As part of the quantitative investigations into the bioenergetic relationships of the Barents Sea capelin, Mallotus villosus villosus (Müller, 1776), resting metabolic rates were examined in the oviferous and post-spawning fish in order to provide insights to aerobic scaling and the basal energetic costs associated with reproduction. Aerobic scaling of the different categories of sexually mature fish (body weight, W=13-54 g) could be expressed as: Q_O2=0.106W^1.049 (oviferous fish; N=11), Q_O2=0.411W^0.430 (post-spawning females; N=9), and Q_O2=0.075W^1.012 (post-spawning males; N=14), where Q_O2 is the oxygen consumption (ml O₂ h⁻¹) per fish. The weight specific oxygen consumption of oviferous capelin was about 30% higher (∼125 ml O₂ kg⁻¹ h⁻¹) compared to those of the post-spawning fish (79-87 ml O₂ kg⁻¹ h⁻¹). The results are discussed in context with other empirical studies on the aerobic scaling and metabolic costs involved with the build-up of roe in the fish.     

Genetic heterogeneity within populations of Lepeophtheirus europaensis (Copepoda: Caligidae) parasitic on two host species

, and 1992. Genetic heterogeneity within populations of Lepeophtheirus europaensis (Copepoda: Caligidae) parasitic on two host species. International Journal for Parasitology 22: 1179–1181. The ectoparasitic copepod Lepeophtheirus europaensis exploits two different species of Mediterranean flat fishes: the brill (a marine fish) and the flounder (found in lagoons). Analysis of the genetic structure of these parasite populations revealed that migration is reduced between the two hosts. Moreover, an adaptive polymorphism was found when the survival of the eggs and free larvae of these copepods was studied at different salinities. The results are discussed and interpreted as signs of a probable speciation process currently occurring within this parasite taxon.