Metazoan parasites and food composition of juvenile <Emphasis Type="Italic">Etmopterus spinax</Emphasis> (L., 1758) (Dalatiidae,Squaliformes) from the Norwegian Deep

A total of 37 juvenile Etmopterus spinax from the Norwegian Deep were examined for stomach contents and metazoan ecto- and endoparasites. These squaliform elasmobranchs were caught by benthopelagic net in May 2001 at a depth of 194-214 m. The euphausiid Meganyctiphanes norvegica and the teleost Maurolicus muelleri were the principal prey organisms. With increasing total length of E. spinax, the frequency of Meganyctiphanes norvegica prey decreased and that of M. muelleri increased. Seven different metazoan parasite species were found: adult Monogenea (2), larval and adult Cestoda (3), and larval Nematoda (2). The predominant parasites were an unidentified monocotylid monogenean and the cestode Aporhynchus norvegicus, with respective prevalences of infestation of 83.8% and 81.1%. The sites of infestation were the gills ( Squalonchocotyle spinacis, Monogenea), nasal cavities (Monocotylidae indet.), body cavity ( Lacistorhynchus tenuis, Cestoda), stomach wall and organs of the body cavity ( Anisakis simplex, Nematoda), and stomach and spiral valve ( A. norvegicus and Pseudophyllidea indet., Cestoda; Hysterothylacium aduncum, Nematoda). No other metazoan parasite taxa were found, and the musculature was free of parasites. Five new host and three new locality records were established. M. muelleri seems to be an important intermediate host for the endoparasitic nematodes which were found, with E. spinax serving as a paratenic host. E. spinax also serves as an intermediate host for the trypanorhynch cestode L. tenuis, and as the definitive host for the two monogeneans and the trypanorhynch A. norvegicus. The latter uses Meganyctiphanes norvegica as the second intermediate host in the Norwegian Deep. The relationship between the feeding ecology, habitat, and vagility of E. spinax and the resulting parasite fauna is discussed.     

Records ofIxodes vespertilionis,I. simplex andArgas vespertilionis (Ixodoidea: Ixodidae,Argasidae) from German bats (Chiroptera)

An investigation of the tick fauna of bats in the Federal Republic of Germany revealed three species:Ixodes vespertilionis, I. simplex andArgas vespertilionis. I. simplex was recorded for the first time in Germany. The occurrence ofI. vespertilionis andI. simplex in Germany is compared with the distribution of their host species.     

The role of pelagic swarm fish (Myctophidae: Teleostei) in the oceanic life cycle of <Emphasis Type="Italic">Anisakis</Emphasis> sibling species at the Mid-Atlantic Ridge,Central Atlantic

First information is provided on the parasitation and feeding ecology of the myctophid fish species Myctophum punctatum and Notoscopelus kroyeri from the Mid-Atlantic Ridge (MAR), Central Atlantic. Four different parasite species were found in both fish with a similar high prevalence and intensity of infestation. The digeneans Gonocerca phycidis and Lethadena sp. were isolated as adults from the stomach, larval tetraphyllidean cestodes (Scolex pleuronectis) from the intestine, and genetically identified larval anisakid nematodes of Anisakis simplex (s.s.) from the body cavity. No further Anisakis sibling species could be identified. Both myctophids had small pelagic crustaceans, mainly copepods and hyperiids, within their stomach contents. Ostracods, euphausiids, decapods, and amphipods were minor food components, demonstrating the pelagic environment for both fish. The recorded parasites including the anisakid A. simplex (s.s.) perform pelagic life cycles within the region, benefiting from extensive diurnal vertical migrations of their fish hosts. Comparison of the host range among the anisakis sibling species suggests that the A. simplex complex has low host specificity, infecting toothed and baleen whales on their extensive oceanic migrations. This contrasts the Anisakis physeteris complex that is restricted to toothed whales of the families Kogiidae and Physeteridae. Specificity in the teleost intermediate hosts for both complexes seems to be low, and sympatric occurrence of different siblings within the same intermediate hosts is likely. Myctophid swarm fish as important copepod feeders at the MAR significantly contribute to the oceanic anisakid nematode life cycle, especially considering the 100% prevalence and high intensity of infestation. Further genetic identification of Anisakis nematodes is needed in order to understand the sibling species distribution, along the MAR and within other oceanic environments.     

Four-year monitoring of parasite communities in gobiid fishes of the south-western Baltic

The parasite infracommunity of five goby species (Pomatoschistus minutus, P. pictus, P.microps, Gobiusculus flavescens, Gobius niger) from the south-western Baltic was investigated during spring, summer and autumn of the years 1997–2000. The mean parasite species number in single hosts was high, ranging between 1.1 (P. minutus), 2.1 (P. pictus) to even 3.3 (P. microps). Gobius niger is the only host which lives longer than a year and is infested by almost identical parasites for longer times, i.e. the parasite species composition has greater homogeneity. Most intensity of infestation values peaked in summer and were lowest in autumn; only a few exceptions were found in spring or autumn. Only the Digenea Podocotyle atomon and Cryptocotyle concavum were abundant enough to show a clear seasonal fluctuation in Pomatoschistus minutus, P. pictus and Gobiusculus flavescens. Aphalloides timmi and Apatemon gracilis (Digenea) also attained high intensities in P. microps. These four parasite species and, additionally, Cryptocotyle lingua (Digenea), and Hysterothylacium sp. (Nematoda) can be strongly accumulated from either prey or free-swimming larvae and, thus, decisively influence the structure of the infracommunities. Due to selection by filter mechanisms, rare parasites settle rather by chance after competition with other species. The number of parasite species usually increased significantly with host growth. As many as four parasite species were found at the same time in the intestinal tract microhabitat of Gobius niger and P. minutus; at most three parasite species were present on the skin and fins or in the body cavity. The level of infection is due to the respective life history patterns and the kinds of prey, which harbour different parasites as intermediate hosts. Additionally, it depends on the time of appearance of goby offspring in the course of the year.     

Distribution of whaleworm (Anisakis simplex,Nematoda, Ascaridoidea) L3 larvae in three species of marine fish; saithe (Pollachius virens (L.)), cod (Gadus morhua L.) and redfish (Sebastes marinus (L.)) from Norwegian waters

The frequency distribution of Anisakis simplex L3 larvae between host tissues was investigated in three host species: saithe, cod and redfish. Fish were sampled from Norwegian coastal waters and examined for the presence of A. simplex in muscle and viscera. In all three of the host species, A. simplex larvae were most frequently detected in the viscera; the percentages of total infection for saithe, cod and redfish were 99.6%, 97.8% and 88.0%, respectively. In general, the distribution patterns of A. simplex L3 between muscle and viscera were not significantly affected by host size. The observations that distributions vary between species and are not affected by host size do not support an earlier hypothesis which states that A. simplex L3 distributions are determined by an optimal pre-encapsulation migratory distance within host tissues. In contrast, it is suggested that A. simplex L3 distributions are governed by the conditions encountered within host tissues, and are possibly related to the availability of nutrients. Received: 9 July 1997 / Accepted: 15 September 1997     

Seven new microsporidian parasites of springtails (Collembola) in the Federal Republic of Germany

Three new species ofNosema (N. lepidocyrti, N. onychiurus andN. petrosa), oneEncephalitozoon (E. flavescens) two species ofThelohania (T. bomboschi andT. collembolae) and a new genusAuraspora n.g. withA. canningae were described from Collembola in soil samples of Lower Saxony, Federal Republic of Germany.

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Sieben neue Mikrosporidien-Arten der Springschwänze (Collembola) aus der Bundesrepublik Deutschland

Zusammenfassung Obwohl die Springschwänze (Collembola) als wichtige Streuzersetzer seit langem Gegenstand bodenbiologischer Forschung sind, gab es bisher keine Hinweise auf das Vorkommen pathogener Protozoen als Parasiten dieser Insekten. Im Rahmen einer vergleichenden Bodentieruntersuchung in verschiedenen Waldstandorten Niedersachsens wurden 1320 Collembolen auf Parasitierung durch pathogene Protozoen geprüft. Dabei konnten erstmals Mikrosporidien (Microsporida, Protozoa) als Krankheitserreger von Collembolen festgestellt werden. Sie werden neu beschrieben:Nosema lepidocyrti sp.n. inLepidocyrtus lignorum Tullberg (Tomoceridae),Nosema onychiurus sp.n. inOnychiurus quadriocellatus Gisin (Onychiuridae),Nosema petrosa sp.n. inLepidocyrtus cyaneus Tullberg (Tomoceridae),Thelohania bomboschi sp.n. inTomocerus flavescens Tullberg (Tomoceridae),Thelohania collembolae sp.n. inL. lignorum undT. flavescens, Encephalitozoon flavescens sp.n. inT. flavescens.Eine Art ist keinem bekannten Genus zuzuordnen:Auraspora gen.n.canningae sp.n. inL. lignorum.Der nachgewiesene Mikrosporidienbefall betrug beiO. quadriocellatus 3% (n=220),L. lignorum 7% (n=130),T. flavescens 8%(n=193) andL. cyaneus 6% (n=63).

     

Seasonal occurrence of the tapeworm<Emphasis Type="Italic"> Proteocephalus longicollis</Emphasis> and its transmission from copepod intermediate host to fish

Seasonal occurrence in terms of prevalence, intensity of infection, abundance and density of the tapeworm Proteocephalus longicollis (Zeder, 1800) and its transmission between its intermediate host (Cyclops abyssorum prealpinus) and definitive host (common whitefish, Coregonus lavaretus) in Lake Annecy, an oligotrophic lake in the western part of the Alps, France, were studied in the period of 1998–2000. A copepod Cyclops abyssorum prealpinus (Kiefer, 1939), the dominant species among planktonic crustaceans in the lake, served as the only intermediate host for this parasite. Infection with plerocercoids was higher in adult copepods (predominantly females) than in copepodite stages IV and V. The prevalence rate of 25% found in C. abyssorum prealpinus females in June 1998 represents a unique infection rate of intermediate hosts with fish tapeworms in natural conditions. The final host, the common whitefish Coregonus lavaretus (L.), was heavily infected with P. longicollis throughout the year (prevalence 90%; mean abundance 40.3; maximum intensity of infection more than 500 tapeworms per fish); immature tapeworms predominated in all samples (P<0.01). Transmission of tapeworm larvae from copepods to the common whitefish took place most intensively in summer and autumn, and depended on seasonal changes in the density of the C. abyssorum prealpinus population, infection of this copepod with plerocercoids and their density in the lake. In addition, transmission efficiency also seems to be determined by the longevity of tapeworm larvae in the intermediate host, timing of predation of the fish host and rapid development of the parasite within this host during the summer period. Overall transmission potential of P. longicollis was low, with only about 9% of juvenile specimens reaching maturity in common whitefish.     

Four-year monitoring of parasite communities in gobiid fishes of the south-western Baltic

The parasite communities of goby species (Teleostei, Percomorphi) from the south-western Baltic Sea were investigated from 1997 to 2000 in three different seasons. In total, 30 parasite species were found in the guild of four goby spp. from Dahmeshöved (Lübeck Bight). The component community of Pomatoschistus minutus comprised 22, Pomatoschistus pictus 20, Gobiusculus flavescens 18 and Gobius niger 14 parasite species, whereas Pomatoschistus microps from the Salzhaff (Mecklenburg Bight) harboured 24 species. The digenean Podocotyle atomon (ingested with prey) and Cryptocotyle concavum (active penetration) were the most common parasites. Cryptocotyle lingua and the nematode Hysterothylacium sp. in Gobius niger as well as the specialists Aphalloides timmi and Apatemon gracilis (Digenea) in Pomatoschistus microps were also very abundant. There were large changes in the parasite communities within the years as well as between the seasons of a year; only Gobius niger presented rather homogeneous communities. The ratio of core parasite species in the hosts was at most 28% (Gobiusculus flavescens) and at least 9% (Gobius niger). The core species can attain their maximum values at different seasons, which is not only influenced by the parasite but also by the host species. It is concluded that the composition of parasite communities was predominantly determined by the ways of life of the host as well as of the parasite species. Another important factor is the population density of intermediate hosts.     

The experimental receptivity ofHelicella (Helicella) itala andCepaea nemoralis (Mollusca,Helicidae) to larvae ofMuellerius sp. andNeostrongylus linearis (Nematoda,Protostrongylidae) from chamois (Rupicapra rupicapra)

Two batches ofHelicella (H.) itala (adult specimens) and two ofCepaea nemoralis (adult and young specimens) were experimentally infected with larvae I (L-I) ofMuellerius sp. andNeostrongylus linearis obtained from the lungs and faeces ofRupicapra rupicapra. In assess larval development, the number and percentage of the total number of larvae (L-I+L-II+L-III) per mollusc were studied, together with the number and percentage of L-III per snail and the days on which the different larval stages were reached. The development ofMuellerius sp. andN. linearis was greater in larvae from faeces. For both species of molluscs, the values for the percentages of the total number of larvae and L-III were higher inN. linearis than inMuellerius sp., but there were no notable differences in the days on which the various larval stages were reached. Both nematodes achieved a greater degree of development in young specimens ofC. nemoralis than in adults. Whether the larvae came from facces or the lungs,H. (H.) itala was a better intermediate host thanC. nemoralis forMuellerius sp. andN. linearis.     

Interactions related to non-host snails in the host-finding process of<Emphasis Type="Italic"> Euparyphium albuferensis</Emphasis> and<Emphasis Type="Italic"> Echinostoma friedi</Emphasis> (Trematoda: Echinostomatidae) miracidia

In order to determine whether the miracidia of Euparyphium albuferensis and Echinostoma friedi are sensitive to their host snail (HS) and capable of discriminating between HS and non-host snails (NHS), or whether these NHS can interfere and thus reduce the infection rates (decoy effect), a total of three experiments were conducted with HS, NHS and snail-conditioned water (SCW). Gyraulus chinensis is the HS for E. albuferensis miracidia, while Physa acuta, Radix peregra and Lymnaea fuscus are considered NHS. For E. friedi miracidia R. peregra, G. chinensis and L. fuscus are the HS, while P. acuta is the NHS. The NHS R. peregra produces the greatest decoy effect on Euparyphium albuferensis miracidia, while R. peregra, as the HS of Echinostoma friedi miracidia, is always subject to a NHS decoy effect. However, an increase in E. friedi miracidia infectivity is observed in its HS G. chinensis, in the presence of SCW of P. acuta. These experimental results might explain the low prevalence of snails infected with E. albuferensis miracidia in their natural habitat.     

An Extended Study of Seroprevalence of Anti‐Anisakis simplex IgE Antibodies in Norwegian Blood Donors

During the last decade, cases of the fish parasite Anisakis simplex infection and allergy in human have increased in countries with high fish consumption. Our aim was to perform an extended seroprevalence study of anti‐IgE antibodies against this parasite in Norway, one of the high fish‐consuming countries. At the Department of Immunology and Transfusion Medicine and the Laboratory of Clinical Biochemistry, Haukeland University Hospital, Bergen, Norway, two main groups of anonymized serum samples were collected; the first (n = 993) from recently recruited blood donors (designated ‘BDO’) and the second (n = 414) from patient with total IgE levels ≥1000 kU/l (designated ‘IGE+’). The sera were analysed by the ImmunoCAP^® method for total IgE and IgE antibodies against A. simplex, house dust mite (HDM), shrimp, cod, crab, brine shrimp and shrimp tropomyosin. The A. simplex positive sera were further tested by an enzyme‐linked immunosorbent assay (ELISA) method, which uses 2 recombinant (r) major allergens, rAni s 1 and rAni s 7 as target antigens. SDS‐PAGE and Western immunoblotting analyses were also performed. Whereas the prevalences by ImmunoCAP^® were 0.4% and 16.2% in the BDO and IGE+ groups, respectively, analyses with recombinant allergens showed only 0.0% and 0.2%. Cross‐reactivity and immunoblotting analyses suggested that most of the ImmunoCAP^® positive sera were probably false‐positive due to cross‐sensitization to shrimp and HDM. However, positivity due to other A. simplex antigens should also be considered. Compared with other high fish‐consuming countries, we observed a very low seroprevalence of anti‐Anisakis IgE antibodies in a Norwegian population.     

Occurrence of anisakid nematodes in Atlantic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) and Greenland cod (<Emphasis Type="Italic">Gadus ogac</Emphasis>), West Greenland

Anisakid nematodes commonly infect gadids, and are of economic and aesthetic importance to the commercial fishing industry in Greenland as some species are pathogenic to humans. However, very little is known about the occurrence of these parasites and their impact on the hosts in Greenland waters. During a survey in 2005, stomach sample of 227 Atlantic cod (Gadus morhua) and 64 Greenland cod (Gadus ogac) was collected in Godthaab and Sisimiut fiord systems in West Greenland waters. All cod were dissected for stomach contents and anisakid nematodes were removed from the visceral cavity. Third stage larvae (L3) of three anisakid species were found, including Contracaecum osculatum (Rudolphi, 1802), Anisakis simplex (Rudolphi, 1809) and Hysterothylacium aduncum (Rudolphi, 1802). Molecular identification by PCR-RFLP indicated the presence of A. simplex s.s. and the sibling species C. osculatum B and C. The prevalence of infection by C. osculatum was higher in Greenland cod (84.3%) than in Atlantic cod (73.9%) whereas the prevalence of A. simplex showed an opposite pattern (Greenland cod 8.3%; Atlantic cod 24.2%). Only one G. morhua (1.0%) was infected by H. aduncum. No gender specific difference in both nematode species regarding prevalence of infection and mean infection intensity was evident, and there was no relationship between fish condition and the intensity of nematode infections. Standardised for size, capelin-eating cod were in better condition and more heavily infected than fish subsisting on alternative prey at the point of collection. Hence, nematode infections in the two gadids seem governed in part by feeding behaviour, and capelin appears a significant source of larval anisakids.     

Association of positional and functional candidate genes<Emphasis Type="Italic"> FGF1</Emphasis>,<Emphasis Type="Italic"> FBN2</Emphasis>, and<Emphasis Type="Italic"> LOX</Emphasis> on 5q31 with intracranial aneurysm

We previously performed a genome-wide linkage study of intracranial aneurysm (IA) and found positive evidence of linkage at chromosomes 5q22–31, 7q11, and 14q22. In the present study, we focus on 5q31, where three candidate genes, fibroblast growth factor 1 (FGF1), fibrillin 2 (FBN2), and lysyl oxidase gene (LOX) lie, and evaluate associations with IA. Genomic DNAs were obtained from 172 IA patients and 192 controls. Association analysis was performed with ten, five, and four single-nucleotide polymorphisms (SNPs) identified in FGF1, FBN2, and LOX, respectively. A difference in allelic frequency was observed for only the SNP at intron 4 in FGF1 (χ²=4.44, df=1, P=0.035). Although a haplotype association was observed with the combination of ten SNPs in FGF1 (χ²=16.04, df=1, P=0.00006), significant haplotype associations were not observed when haplotypes were constructed with the three, two, and four SNPs in FGF1 according to the linkage disequilibrium structure. No associations of FBN2 and LOX with IA were detected in the present study.     

Seasonal dynamics of<Emphasis Type="Italic"> Posthodiplostomum cuticola</Emphasis> (Digenea,Diplostomatidae) metacercariae and parasite-enhanced growth of juvenile host fish

The seasonal dynamics of Posthodiplostomum cuticola metacercariae in 0+ juvenile fish, Rutilus rutilus, Scardinius erythrophthalmus and Abramis bjoerkna, was studied on the floodplain of the Dyje River, Czech Republic. Prevalence and mean abundance of P. cuticola were significantly higher in R. rutilus than in S. erythrophthalmus or A. bjoerkna. A seasonal pattern of parasite infection with maximum values in autumn was evident in all three species. No effect of overwintering on the P. cuticola infection was detected. Parasite-induced growth was found for all three fish species investigated; the fish standard length and body weight of parasitized individuals were significantly higher than those of unparasitized fish from July to October. In April, no difference was found. The maximum enhanced growth of parasitized fish was found in months with low zooplankton densities, while the difference was lower when food was abundant.     

<Emphasis Type="Italic">Anisakis simplex</Emphasis> only provokes allergic symptoms when the worm parasitises the gastrointestinal tract

We analysed patients with allergic or digestive symptoms after seafood ingestion in order to assess a correct diet in Anisakis simplex sensitised individuals. A total of 120 patients who suffered allergic and/or digestive symptoms after marine food ingestion were studied. We performed skin prick tests for A. simplex and seafood, total serum and specific serum immunoglobulin E to A. simplex in the acute stage and 1 month later. A gastroscopy was carried out to find larvae in those patients with persistent abdominal pain. A challenge with non-infective larvae was performed to assess a correct diet. Some 96 patients were sensitised to A. simplex. Gastroscopy was performed in 47 and we detected larvae in 24. We compared symptoms, skin tests, total and specific IgE and the latency of appearance of symptoms in patients positive for Anisakis larvae, patients without larvae at gastroscopy and patients without digestive symptoms. There was no difference among the groups. We challenged 22 patients with frozen A. simplex larvae. After allowing deep-frozen seafood in the diet for more than 2 years, no patient suffered a reaction. At this time, we allowed all our patients well-frozen seafood without any allergic reaction occurring. Allergic symptoms are the most frequent manifestation of A. simplex parasitism. We could not find any patient allergic to the thermostable proteins of parasite.     

The karyotype of four Trichinella species

Karyological studies ofTrichinella spiralis, T. pseudospiralis, T. nativa andT. nelsoni were undertaken. Comparison of the karyotypes of theseTrichinella species showed that the chromosome number of all four species is 2n=6 for female specimens and 2n=5 for males. The differences found in the relative chromosome lengths of the individualTrichinella species are not significant.Centromeric index data indicate thatT. nativa andT. spiralis have similar centromere dispositions and differ from the other two species by the disposition of the centromere of the first submetacentric chromosome pair. InT. nativa andT. nelsoni the univalent sex chromosome is the second in size. It is a slightly submetacentric chromosome, while inT. spiralis andT. pseudospiralis it is the third metacentric chromosome. The data from the karyological investigations may be used as additional karyosystematic characteristics when differentiating theTrichinella species studied.     

Transmission experiments on the host specificity ofHeterophyes species in 16 potential definitive hosts

Sixteen different species of piscivorous mammals and birds were tried as experimental definitive hosts forHeterophyes heterophyes, H. aequalis andH. dispar. The hosts were classified in four categories, by fluke longevity, recovery and size, and the number of uterine eggs (embryonated/unembryonated): (1) Canidae and the cat were highly susceptible hosts for all three species ofHeterophyes; (2) several mammals and herons showed a reduced susceptibility to infection (H. aequalis, 6 species;H. dispar, 1 species;H. heterophyes, 0 species); (3) In a group of hosts specific to each trematode, flukes were recovered up to 14 days post infection, but their uterine eggs did not become embryonated; (4) In a fourth category of hosts, chiefly Mustelidae, flukes could not be recovered. Taking also the literature into account it is concluded that man is a highly susceptible host forH. heterophyes, and that probablyH. aequalis andH. dispar may reach reproductive maturity in humans also. The described wide host range ofH. aequalis appears to be more typical for Heterophyidae than the comparably narrow host range ofH. heterophyes.     

Helminths of Antarctic fishes: Life cycle biology, specificity and geographical distribution

Bony fishes (Teleostei) play an important role in the completion of life cycles of helminth parasites in the Antarctica. These fishes may be definitive, second intermediate or paratenic hosts of the helminths. The most species-rich taxon is Digenea. Virtually all of these digeneans use teleosts as definitive hosts. Only one species, Otodistomum cestoides, occurs as the adult stage in skates (Chondrichthyes), with teleosts as its second intermediate host. Among 14 cestode species maturing in fishes only one, Parabothriocephalus johnstoni, occurs in a bony fish, Macrourus whitsoni, whereas the others are parasites of Chondrichthyes (cartilaginous fishes). Antarctic Chondrichthyes are not infected with nematode and acanthocephalan species. Specificity to the intermediate and/or paratenic hosts of the majority of Antarctic helminths is wide, whereas that for definitive hosts is often narrower, restricted to one order or sometimes even to one or two host species. Almost all of 73 helminth species maturing in Antarctic fishes are endemics. Only 4 digenean and one nematode species are cosmopolitan or bipolar.     

Ségrégation biologique et écologique de deux espèces jumelles sympatriques de Trématodes (Trematoda,Gymnophallidae)

Gymnophallus fossarum andG. nereicola are sympatric sibling species. These two gymnophallids have the same morphological and anatomical features. Nevertheless, the identification of both species is possible due to some small differences. Among the factors distinguishing these two closely related species from each other, the biological and ecological mechanisms are very important. Biological Factors. The life cycle is different for these two species. The first intermediate host ofG. fossarum is onlyScrobicularia plana, the one ofG. nereicola is exclusivelyAbra ovata. At this stage in their life cycle,G. fossarum andG. nereicola show a high level of host specificity.G. fossarum uses various bivalves as its second intermediate hosts;G. nereicola uses only one species, an annelid,Nereis diversicolor. Cercariae ofG. fossarum cannot enter the annelids; those ofG. nereicola cannot develop into metacercariae in pelecypods. Adult flukes ofG. fossarum are parasites ofHaematopus ostralegus, the oyster-catcher; those ofG. nereicola are found in a number of charadriid and lariid birds. Ecological Factors. Gymnophallus fossarum andG. nereicola have different endemiotops. The one ofG. fossarum is confined to the peripheral shallow area of lagoons, where the marine water salinity is low. The endemiotop ofG. nereicola is limited to the shallow area covered withZostera nana in marine lagoons or withRuppia maritima in brakish ponds. The transmission area ofG. fossarum is not large whereas the one ofG. nereicola is very extensive. Altogether, these mechanisms maintain the segregation between the two sympatric sibling species.     

Differentiation of the “Ascochyta complex” fungi of pea by biochemical and molecular markers

Isolates of three closely related pea pathogens,Ascochyta pisi, Ascochyta pinodes (teleomorphMycosphaerella pinodes) andPhoma medicaginis var. pinodella, were compared by means of isozyme analysis and restriction fragment length polymorphisms (RFLP) of amplified rDNA spacers. Three enzyme systems differentiatedA. pisi fromM. pinodes andP. m. pinodella. The internal transcribed spacers (ITSs) of the three fungi showed no intraspecific and very little interspecific variation after digestion with 12 endonucleases. Digestion of the intergenic spacer (IGS) withHinfI, andSau3A revealed uniformity inA. pisi patterns which consistently differed from those ofM. pinodes andP. m. pinodella. No clear distinction could be made between the latter two fungi which both showed intraspecific variability. Both biochemical and molecular markers thus discriminated between twoAscochyta species. The results also indicated a closer relationship between two organisms belonging to different genera (Ascochyta andPhoma) than between two species of the same genus (Ascochyta).