Lecithaster Gibbosus Research Articles

The helminthofauna of the pink salmon <i>Oncorhynchus gorbuscha</i> (Walbaum, 1792) of south-east Sakhalin according to the results of many years of research

The purpose of the research is to describe and analyze the qualitative and quantitative composition of pink salmon helminths of southeastern Sakhalin.Materials and methods. Standard parasitological methods of collecting material were used. At the autopsy, the ureters, eyeballs, gill petals and arches, and the brain of fish were not examined. The method of collecting salmon parasites in the laboratory has been unchanged since 1992. Collections of representatives of monogenetic suckers were not carried out. Parasitological studies of pink salmon of southeastern Sakhalin were carried out from 1992 to 2022, a total of 4163 fish specimens were examined. The fish is caught in the estuaries of rivers and the sea coast.Results and discussion. According to the results of their own research and literature data, the pink salmon helminth fauna of southeastern Sakhalin is represented by 23 species: Dibothriocephalus nihonkaiensis pl., Eubothrium salvelini, Eu. crassum, Nybelinia surmenicola pl., Pelichnibothrium speciosum pl., Tetraphyllidea gen. sp., Brachyphallus crenatus, Cryptocotyle sp. mtc., Hemiurus levinseni, Lecithaster gibbosus, Prosorhynchoides gracilescens, Parahemiurus merus, Derogenes varicus, Capiatestes thyrsitae, Corynosoma strumosum l., Echinorhynchus gadi, Bolbosoma caenoforme juv., B. bobrovoi juv., Rhadinorhynchus trachuri, Anisakis simplex l., Ascarophis pacifica, Ascarophis skrjabini, Hysterothylacium aduncum. The qualitative composition of the helminth fauna is currently undergoing minor changes, while the quantitative characteristics of some helminths are significantly reduced. Thus, the infection of pink salmon with Bolbosoma sp. juv scrapers. decreased to 0.61±0.18.

Lecithaster (Lecithasteridae, Digenea) in the White Sea: an unnoticed guest from the Pacific?

Morphological discrimination of species is problematic in many digenean taxa. Parasites of marine fish from the genus Lecithaster Lühe, 1901 are a good example of this. Our goal was to understand which species of Lecithaster infect fish in the White Sea, and reveal their life cycles. We collected specimens of maritae from nine fish species, analysed their morphology and sequenced 28S ribosomal DNA and internal transcribed spacer 2 (ITS2). Contrary to previous accounts, all of them belong to a single species, Lecithaster salmonis Yamaguti, 1934, which was previously only recorded from the Pacific. Morphologically, our maritae specimens were highly variable, sharing characters of L. salmonis, Lecithaster confusus Odhner, 1905 and Lecithaster gibbosus (Rudolphi, 1802) Lühe, 1901. This variability did not correlate with the moderate differences in ITS2 among the specimens, and neither did the fish host species. Members of the subfamily Salmoninae appear to be the best suited definitive hosts, judging from the intensity rates. The intermediate hosts were also discovered: the first is Cryptonatica affinis (Gmelin, 1791) and the second are planktonic copepods. These lifecycle data from the White Sea are consistent with L. salmonis species identification and with the distribution of this species in the North Pacific. The geographical range of L. salmonis seems to be interrupted, and we discuss possible ways of L. salmonis expansion.

Endoparasitic Helminths of the European Sprat, Sprattus sprattus (Linnaeus, 1758) from the gulf of Gdańsk (the Southern Baltic Sea) with a checklist of its parasites

Sprat Sprattus sprattus is a common fish across the European seas. It is of great importance for fishing industry, also in the southern Baltic Sea. Although parasitic fauna of the species has already been a subject of interest, it is still not very well explored in the southern Baltic Sea. In 2009 and 2011, 187 specimens of the European sprat from the Gulf of Gdansk (26 ICES subdivision) were examined for the presence of parasites. The parasites found represented Digenea: Lecithaster gibbosus (Rudolphi, 1802) and Nematoda: Hysterothylacium aduncum (Rudolphi, 1802) and Contracaecum spp. The overall prevalence was 3.2% with the mean intensity of 1.0 and abundance of 0.005. The parasite fauna of the European sprat from the southern Baltic Sea is poorly diversified and infection rates are low in comparison to other European seas. A checklist of parasites in European sprat world-wide is also provided.

Five Trophically-transmitted Parasites from Adult Arctic Lampreys Lethenteron camtschaticum (Petromyzontiformes: Petromyzontidae): Biological Indicators of the Host's Marine Life as a Predator

Five species of helminth endoparasite (two digeneans, Brachyphallus crenatus (Rudolphi, 1802) and Lecithaster gibbosus (Rudolphi, 1802); two cestodes, plerocercoids of Nybelinia surmenicola (Okada in Dollfus, 1929) and a tetraphyllidean; and an acanthocephalan, post-cystacanths of Bolbosoma sp.) were found in adults of Arctic lampreys Lethenteron camtschaticum (Tilesius, 1811) arriving in the lower part of the middle reaches of a river in Hokkaido, Japan, for spawning after a period of growth in the sea. These parasites are all common species previously reported from various marine fishes in the North Pacific and all have complex life-cycles involving host-to-host transmission via a predator-prey relationship. To have become infected with these food-borne parasites, Arctic lampreys need to have ingested various body parts of infected prey fishes at sea. Consequently, the endoparasites recovered suggest that the Arctic lamprey has a role as a predator in marine ecosystems.

Annual and spatial variability in endo- and ectoparasite infections of North Sea cod (Gadus morhua Linnaeus, 1758) larvae, post-larvae and juveniles.

A parasitological investigation was performed on a total of 5380 Atlantic cod larvae, post-larvae and small juveniles sampled from the North Sea during a period of five years. The copepod Caligus elongatus (Von Nordmann, 1832) and the nematode Hysterothylacium aduncum (Rudolphi, 1802) were found at a relatively high prevalence of infection (4.6% and 5.2%, respectively). The infection by both parasites showed annual and spatial variability. C. elongatus showed a higher prevalence in 1992 compared to the following years, whereas the prevalence of H. aduncum increased from 1992 to 2001.We observed a relation between parasite distribution and parameters such as latitude and water depth. Adult digeneans (Lecithaster gibbosus and Derogenes varicus) and larval cestodes were also found with lower infection rates. Since changes of infection levels coincided with increasing North Sea water temperature in the studied period, it is hypothesized that temperature may affect parasite population levels. However, it is likely that other environmental factors may contribute to the observed variations. Absence of infection intensities higher than one nematode per fish in small larvae and post-larvae suggests that host survival may be affected by a high infection pressure. The relatively high levels of infection in the younger stages of cod, and the annual/spatial variability of these infections should be considered in the understanding of the early life dynamics of the species.

Boreogadus saida (Lepechin) (Gadidae): a review of its metazoan parasite fauna from Greenland, eastern Canada, Alaska and the Russian Arctic

The metazoan parasite fauna of 50 specimens of Boreogadus saida (Lepechin) (Gadidae) from eastern Greenland is very similar to those of previous studies of the parasite fauna of B. saida from Greenland, eastern Canada, Alaska and the Russian Arctic. The digeneans Hemiurus levinseni, Derogenes varicus and Lecithaster gibbosus and cestode larvae were found at most stations. Single specimens of the nematode larvae Anisakis simplex were found at four stations. A comparison of the distribution of the larvae of Contracaecum sp. and Hysterothylacium sp. is difficult due to a possible confusion of the two genera. Most of the metazoan parasites of B. saida are generalist species found in several fish families. Boreogadus saida acquires most of its endoparasites by eating pelagic crustaceans, mainly copepods and amphipods. It plays an important role in the arctic ecosystem and its parasites are transferred to predatory fish, birds and mammals through the food web.

The parasite fauna of Arctogadus glacialis (Peters) (Gadidae) from western and eastern Greenland

In all 155 specimens of the high Arctic codfish Arctogadus glacialis examined for metazoan parasites, 55 specimens were from southern and northern Baffin Bay, western Greenland, and 100 specimens from north-eastern Greenland and Scoresby Sound. A total of 20 parasite taxa were recorded. A new myxozoan Gadimyxa arctica was found in southern Baffin Bay and Scoresby Sound. The gadid myxozoan Zschokkella hildae, the digeneans Gonocerca phycidis and Lecithaster gibbosus, the gill copepod Haemobaphes cyclopterina and third-stage larvae of the nematodes Anisakis simplex and Hysterothylacium aduncum were found in Scoresby Sound only. The digenean Hemiurus levinseni and third-stage larvae of the nematode Contracaecum sp. were found at all four stations. The nematodes Ascarophis spp. were found at three stations. The parasite fauna of A. glacialis from Scoresby Sound was very similar to that of 50 specimens of the closely related Boreogadus saida from the same area.

Influence of a Thermal Discharge on Parasites of a Cold-Water Flatfish, Pleuronectes americanus, as a Bioindicator of Subtle Environmental Change

A study was conducted to ascertain the influence of a thermal discharge on the health and parasites of a coastal cold-water flatfish, the winter flounder (Pleuronectes americanus), a species sensitive to environmental change. Flounder were sampled in spring 1998 and 1999 beneath the plume and at reference sites north and south up to 1 km from the discharge. Species diversity and estimates of abundance of macroscopic algae, invertebrates, and fish were also recorded. After capture by scuba divers, a comparison of condition factor, organ indices, blood values, histology, and parasites was made between groups of fish from the discharge and reference sites. Diversity and abundance of algae, invertebrates, and fish were considerably greater beneath the plume than at the reference sites. The thermal water had no apparent effect on flounder taken beneath the plume, but it affected both its ecto- and endoparasites. Prevalence and mean abundance of Cryptocotyle lingua metacercariae were significantly greater, whereas Trichodina jadranica and Gyrodactylus pleuronecti were less on the gills of fish sampled beneath the plume than at the reference sites. Four endoparasites, i.e., Ceratomyxa drepanopsettae, Steringophorus furciger, Macvicarius soleae, and Lecithaster gibbosus were significantly more abundant in the reference samples. These results suggest that environmental change affected transmission of the parasites of winter flounder exposed to the thermal effluent.

HELMINTH COMMUNITIES OF THE LESSER SANDEEL AMMODYTES TOBIANUS L. OFF THE WEST COAST OF IRELAND

The helminth parasites present in 412 lesser sandeels (Ammodytes tobianus) taken from June 1996 to May 1997 from the Aran Islands on the west coast of Ireland were examined. Ten helminth parasite species were recorded, and more than 92% of the sandeels were infected with at least 1 helminth species. Seven of the species were digeneans, including Brachyphallus crenatus, Hemiurus communis, Derogenes varicus, Lecithaster gibbosus, Opechona bacillaris, Cryptocotyle lingua, and Galactosomum lacteum; 2 nematodes, including Hysterothylacium sp. and Contracaecum sp.; and 1 cestode, Scolex pleuronectis. Three of the 7 digenean species were either larvae or immature. Only 2 species, the digeneans G. lacteum and H. communis, had prevalences greater than 50%. The dominant species was G. lacteum, accounting for 67% of all parasites present. The relationship between spawned groups, host length, and season versus the abundance, prevalence, species richness, and the total number of parasites in the infracommunities was investigated. No difference was found between the parasite communities of the 2 spawning races of the host population. Mean abundance and prevalence of the different parasite species showed seasonal variation. Numbers of parasite species and numbers of parasites increased with fish length. The role of A. tobianus as an intermediate host for helminths was assessed; it was determined that most were infectious to birds or mammals, with the majority of the parasite species being autogenic (infectious to fish). The mean number of parasites per fish was nearly a quarter of the value recorded for A. tobianus in the North Sea, where a much higher intensity of infection was recorded.

Parasites of herring (Clupea harengusL.) larvae from a local Norwegian fjord stock

A parasitological examination was performed on 2444 juvenile herring Clupea harengus (11-54 mm) trawled from Osterfjorden, west Norway in May 2000. Most (99.3%) were larvae (<40 mm), whereas 18 fish were at transition stage or metamorphosed. We found five endoparasite species: Lecithaster gibbosus (Digenea), a juvenile didymozoid (Digenea), tetraphyllidean and pseudophyllidean cestode larvae and Hysterothylacium aduncum (Nematoda) larvae. The only ectoparasite detected was a Caligus elongatus (Copepoda) chalimus larva. Lecithaster gibbosus, Hysterothylacium aduncum and Caligus elongatus larvae have previously been shown to kill cultured herring larvae by causing mechanical damage. The rarity of metazoan parasites in herring larvae from this locality suggests that these are not a significant cause of natural mortality in this area.

Parasites of herring ( Clupea harengus L.) larvae from a local Norwegian fjord stock

A parasitological examination was performed on 2444 juvenile herring Clupea harengus (11-54 mm) trawled from Osterfjorden, west Norway in May 2000. Most (99.3%) were larvae (<40 mm), whereas 18 fish were at transition stage or metamorphosed. We found five endoparasite species: Lecithaster gibbosus (Digenea), a juvenile didymozoid (Digenea), tetraphyllidean and pseudophyllidean cestode larvae and Hysterothylacium aduncum (Nematoda) larvae. The only ectoparasite detected was a Caligus elongatus (Copepoda) chalimus larva. Lecithaster gibbosus, Hysterothylacium aduncum and Caligus elongatus larvae have previously been shown to kill cultured herring larvae by causing mechanical damage. The rarity of metazoan parasites in herring larvae from this locality suggests that these are not a significant cause of natural mortality in this area.

Parasites of capelin (Mallotus villosus) in the St. Lawrence estuary and gulf

A survey of the parasites of capelin (Mallotus villosus) caught on the spawning grounds at five localities in the estuary of the St. Lawrence River and the Gulf of St. Lawrence, Canada, was conducted in 1994. From examination of 125 fish, a total of 21 parasite taxa was identified (2 Protista, 3 Monogenea, 4 Digenea, 4 Cestoda, 7 Nematoda, and 1 Acanthocephala). Seven new host records are reported for this fish (Trichodina sp., Brachyphallus crenatus, Bothrimonus sturionis, Ascarophis sp., Pseudoterranova decipiens larva, Spirurida gen.sp. larva, and Echinorhynchus laurentianus). The parasite fauna of capelin is comparatively depauperate. It is characterized by the relative abundance of a few species showing a high level of host specificity (Microsporidium sp., Trichodina sp., Gyrodactyloides andriaschewi, G. petruschewskii, Laminiscus gussevi, and Eubothrium parvum) that mature on or in capelin, several ubiquitous adult digeneans (e.g., B. crenatus, Derogenes various, Hemiurus levinseni, and Lecithaster gibbosus), and a number of species that use capelin as intermediate or transport hosts (e.g., Scolex pleuronectis plerocercoid, Anisakis simplex larva, Contracaecinea gen.sp. larva, and Hysterothylacium aduncum larva).

Metazoan parasite infections in landlocked and anadromous Arctic charr (Salvelinus alpinus Linnaeus), and their use as indicators of movement to sea in young anadromous charr

Eighteen genera of metazoan parasites (Monogenea, 1; Digenea, 7; Cestoda, 4; Nematoda, 4; Acanthocephala, 1; Copepoda, 1) were collected from 172 landlocked and anadromous Arctic charr (Salvelinus alpinus Linnaeus) in northern Labrador. Four species (Lecithaster gibbosus, Diphyllobothrium dendriticum, Diphyllobothrium ditremum, and Salmincola carpionis) and one genus (Tetraonchus) have not previously been reported from Arctic charr in Labrador. The dominant parasites in the landlocked charr were Diplostomum sp., Crepidostomum farionis, and Diphyllobothrium ditremum. In the sea-run charr, Bothrimonus sturionis and Brachyphallus crenatus were dominant. Regression analyses indicated that the numbers of parasites were significantly correlated with host age (P &lt; 0.001) for these species. All landlocked charr sampled were infected with parasites by age 1+ years whereas all sea-run charr were infected by age 3+. At 1+ years, 43% of the Arctic charr collected in the Ikarut River were infected with marine or brackish-water parasites, suggesting that some young charr, not yet ready for the annual seaward migration, may make short feeding excursions into salt water.

Parasites in European eelAnguilla Anguilla(L.) from Danish Freshwater, Brackishand Marine Localities

Abstract The parasite fauna of 370 specimens of European eel, Anguilla anguilla(L.), (35–55 cm long) caught in three lakes in Denmark, three brackish localities and in the western Kattegat, was examined. A total of 46 species of parasites were found, the highest number (27) was found in a lake, and the lowest (10) in the western Kattegat. Myxidium giardi and Myxobolus sp. were found at all seven localities. Pseudodactylogyrus anguillae, Diplostomum sp. metacercariae, Bothriocephalus clauiceps, Proteocephalus macrocephalus, Raphidascaris acus, Anguillicola crassus and Ergasilus gibbus were found in both freshwater and brackish localities. Podocotyle atomon, Deropristis inflate, Hemiurus communis, Brachyphallus crenatus, Derogenes varicus, Lecithaster gibbosus, Lecithochinum rufotnride and Cryptocotyle lingua metacercariae occurred in brackish or marine localities. Gyrodactylus spp., tetraphyllidean larvae and Hysterothylacium aduncum occurred in brackish localities. The freshwater dracunculoid nematodes Ph...

A survey of the parasites of nonanadromous and anadromous brook charr (Salvelinus fontinalis) in the Tabusintac River, New Brunswick, Canada

A parasite survey of 1146 brook charr (Salvelinus fontinalis) was conducted between January 1981 and December 1982 in the Tabusintac River, New Brunswick, Canada. A total of 36 parasite species were recovered, of which 18 (one Myxosporea, two Monogenea, three Digenea, three Cestoidea, five Nematoda, one Acanthocephala, one Hirudinoidea, one Crustacea, and a Dermocystidium sp.) were freshwater and 18 (two Monogenea, seven Digenea, two Cestoidea, two Nematoda, two Acanthocephala, and three Crustacea) were marine. Anadronomous charr were differentiated from nonanadromous charr in fresh water by the presence of marine parasites. Charr in the estuary and lagoon were all considered to be anadromous; however, first-time anadromous charr or smolts were differentiated by the absence of marine parasites and infection with freshwater parasites only. New host records include Lecithaster gibbosus, Zoogonus lasius, Podocotyle angulata, Cryptocotyle lingua (metacercariae), Stephanostomum tenue (metacercariae, adults), Eubothrium crassum, Tetraphyllidea gen. sp. (plerocercoids), Eustrongylides sp. (larvae), Hysterothylacium aduncum (larvae, adults), Corynosoma magdaleni (juveniles), Argulus alosae, and Ergasilus labracis. Zoogonus lasius and Stephanostomum tenue represent new Canadian records, and Chloromyxum truttae and Truttaedacnitis truttae are reported for the first time from New Brunswick. Bulbodacnitis alpinus, previously reported only from the Arctic charr (Salvelinus alpinus), is considered to be a synonym of T. truttae.

Potential of Parasites for Use as Biological Indicators of Migration, Feeding, and Spawning Behavior of Northwestern Atlantic Herring (Clupea harengus)

A parasite survey of Atlantic herring, Clupea harengus, collected from the Bay of Fundy, Nova Scotian Shelf, and Gulf of St. Lawrence, was conducted from May 1981 to November 1983. A total of 2380 herring were examined and 18 parasite species identified. These included the acanthocephalan Echinorhynchus gadi previously unreported from herring in the northwestern Atlantic and the monogenean Gyrodactyloides andriaschewski herein described from herring for the first time. The geographic distributions of the parasites, their seasonal dynamics, and relation to size of herring were recorded to determine whether they could be used as biological indicators, both to differentiate between individual herring populations and to determine their movements. Seven of the 18 species identified showed varying degrees of potential as biological indicators. Although no single parasite species was found which could clearly differentiate one population of herring from another, the differential prevalences and intensities of Anisakis simplex, Hysterothylacium aduncum, Derogenes varicus, Lecithaster gibbosus, Cryptocotyle lingua, Scolex pleuronectis, and Eimeria sardinae all provided valuable contributions to the knowledge already accumulated on herring migration, feeding, and spawning behavior. Parasite indicators, used in conjunction with other data and techniques, could eventually be used to distinguish between individual populations of herring.

Digenean (Trematoda) populations in winter flounder (Pseudopleuronectes americanus) from Passamaquoddy Bay, New Brunswick, Canada

Examination of monthly samples of winter flounder (Pseudopleuronectes americanus) from Passamaquoddy Bay revealed seven digenean parasites (Genolinea laticauda, Podocotyle atomon, Stenakron vetustum, Fellodistomum furcigerum, Derogenes varicus, Lecithaster gibbosus, and Steganoderma formosum) in the alimentary tract and two metacercariae (Stephanostomum baccatum and Cryptocotyle lingua) in the body surface tissues and gills. Prevalence of alimentary tract parasites ranged from 0.2 in S. formosum to 39.8 in P. atomon and intensity ranged from 1.5 for D. varicus to 7.0 for S. formosum (one fish). Monthly and seasonal levels of prevalence varied: high in spring and autumn and low in summer and winter for most species. Prevalence and length-frequency distributions of the parasites did not support differential migration by size group or diminishing feeding activity from spring to winter in winter flounder, as proposed in other studies.

Digenetic trematodes fromGadus morhuaL. (Osteichthyes, Gadidae) from Danish and adjacent waters, with special reference to their life-histories

Abstract A total of 890 specimens of the Atlantic cod Gadus morhua L. (Osteichthyes, Gadidae) have been examined for infestations with digenetic trematodes. The cods were caught at 15 sampling stations in Danish and adjacent waters with salinities ranging from 8‰ (the Baltic off Bornholm) to 35‰ (the North Sea and the Atlantic Ocean off the Faroes), and from shallow water down to a depth of 230 m. 18 species (metacercariae and adults) were found. The following species were found in the alimentary tract: Prosorhynchus squamatus Odhner, 1905 (Bucephalidae), Podocotyle atomon (Rudolphi, 1802), P. reflexa (Creplin, 1825) (Opecoelidae), Lepidapedon elongatum (Lebour, 1908), L. rachion (Cobbold, 1858), Opechona bacillaris (Molin, 1859) (Lepocreadiidae), Stephanostomum pristis (Deslongchamps, 1824) (Acanthocolpidae), Derogenes varicus (Muller & 1784), Lecithaster gibbosus (Rudolphi, 1802), Brachyphallus crenatus (Rudolphi, 1802), Hemiurus communis Odhner, 1905, H. luehei Odhner, 1905, H. levinseni Odhner, 1905, ...

Incidence of Trematode Parasites of American Plaice (Hippoglossoides platessoides) of the Scotian Shelf and Gulf of St. Lawrence in Relation to Fish Length and Food

The following digenetic trematodes were found in the alimentary tract of American plaice (Hippoglossoides platessoides) from the Scotian Shelf and Gulf of St. Lawrence: Derogenes varicus, Fellodistomum furcigerum, Lecithaster gibbosus, Stenakron vetustum, Steringotrema ovacutum, Zoogonoides viviparus, Hemiurus levinseni, Otodistomum veliporum (larvae), Podocotyle atomon, Prosorhyncus squamatus.The incidence of several trematode species changed with length of fish and associated changes in the fish’s diet. Incidence of D. varicus and S. vetustum decreased with increase of host length, whereas incidence of R. ovacutum and Z. viviparus increased. Lecithaster gibbosus and S. furciger showed little change in incidence. Correlations between parasite incidence and frequency of occurrence of food items indicated that small crustaceans may be intermediate hosts for S. vetustum and D. varicus; sea urchins may be intermediate hosts for R. ovacutum and brittle stars for Z. viviparus.

Changes in the parasite fauna of whiting Odontogadus merlangus L. with age and sex of host, season, and from different areas in the vicinity of the Isle of Man

Infestation of whiting with the helminths Derogenes varicus Müller, Hemiurus communis Odhner, Grillotia erinaceus Van Beneden (plerocercoids) and Contracaecum clavatum Rudolphi, and the copepod Lernaeocera branchialis L., increased with the age of the fish but infestation with the helminths Lecithaster gibbosus Rudolphi, Stephanostomum pristis Looss and Podocotyleatomon and the copepod Clavella uncinata Müller decreased as the fish aged. Infestation with the gill monogenean Diclidophora merlangi Kuhn remained at much the same level in fish 1–5+ years old. Derogenes, Hemiurus, Lecithaster, Cotracaecum and Stephanostomum showed seasonal fluctuations in the levels of their populations in whiting. In all cases the parasites reached a main peak in the summer and early autumn, a time when juvenile digeneans were most apparent.Whiting from Morecambe Bay were less infested with Clavella than whiting taken from other areas. Experimental evidence suggests that the lower salinity of Morecambe Bay may be responsible; however, this could not account for the lower infestation of Morecambe Bay whiting by Diclidophora which appeared to be unaffected by a lowered salinity. Whiting from the east side of the Isle of Man were more infested with Lernaeocera but less infested with Diclidophora than fish from the west side of the island. The myxosporidian Myxobolus aeglefini Auerbach was externally visible in the sclera of whiting from the east side of the island but absent from the sclera of whiting from the west side of the island. It is, therefore, suggested that whiting to the east of the Isle of Man form a separate sub‐stock from those to the west of the island.