Parasitism at the ecosystem level in the Baltic Sea.

The Baltic Sea is characterized by organisms that can tolerate brackish water. Because of the Sea's history during glacial times, its flora and fauna (and also their parasites) can be traced to marine, freshwater and genuine brackish elements beside glacial relics. Snails, planktonic copepods, benthic amphipods and isopods are important intermediate hosts of diverse helminths; in addition polychaetes, bivalves and fishes may also act as final hosts. The most important final hosts, beside fishes, were seals and birds; these were able to disperse the parasites over the whole of the Baltic. Decreasing salinity from west to east limits the distribution of many parasites. Several marine and genuine brackish water species have almost spread over the whole Baltic. Freshwater species, however, have a lower tolerance than marine species and are only rarely found in the western part. A serious problem in the Baltic is eutrophication which can lead to massive abundances of generalist parasites, in host populations as well as host individuals. The final stage of this influence can cause a general decrease of host abundance and, as a consequence, of all kinds of parasites, due to oxygen deficiency. In comparison with the species spectrum of other brackish waters in Europe, the Baltic presents some endemic parasites as well as sharing parasite species with the Mediterranean and even the Black Sea.

Parasite communities of the Salzhaff (Northwest Mecklenburg, Baltic Sea) II. Guild communities, with special regard to snails, benthic crustaceans, and small-sized fish.

Metazoan parasites of guilds of benthic snails and crustaceans and of four fish families--Gobiidae, Gasterosteidae, Syngnathidae, and Zoarcidae--were investigated off the brackish Salzhaff area (Southwest Baltic) in the semienclosed Salzhaff and the near Rerik Riff in the free Baltic. Comparisons revealed greater similarities in parasite populations and communities within the fish guilds than between them. According to an evaluation of the core-/satellite-species concept using abundance values, the most important parasites of fish were some generalists, such as Cryptocotyle spp., Podocotyle atomon, and Diplostomum spathaceum, as well as some specialists, such as Acanthostomum balthicum, Thersitina gasterostei, and Aphalloides timmi. These specialists revealed high degrees of prevalence in their main hosts and lower degrees in one or two by-hosts. Additional importance is assigned to parasites that cause harm to their hosts due to their large size, e.g., Schistocephalus spp., or via massive infestation, e.g., several digenean metacercariae. Because specialists were more prominent in snails and fish from the Rerik Riff, the correlation of host numbers with prevalence resulted in only a slight increase instead of a more rapid rise in regression among crustaceans and fish from the entire Salzhaff, where the generalists were more prevalent. The selected host guilds demonstrated the entire life cycles of three digeneans (P. atomon, A. balthicum, A. timmi), one acanthocephalan (Echinorhynchus gadi), and one nematode (Hysterothylacium sp.). The prevalence increased in these cycles from host level to host level and attained relatively high values in all guilds. The parasite fauna of the Salzhaff area is influenced by eutrophication stress, which leads to a high level of productivity and, consequently, to great densities in primary consumers such as snails and crustaceans. These are attractive for several secondary consumers such as fish and birds, which is the reason for the existence of at least 24 autogenic and 20 allogenic parasite species at this locality. The slight surplus of the first category indicates a yet-balanced environment in the investigation area.

Parasite communities of the Salzhaff (Northwest Mecklenburg, Baltic Sea). I. Structure and dynamics of communities of littoral fish, especially small-sized fish.

The parasites of ten fish species, including four Gobiidae, three Gasterosteidae, two Syngnathidae, and one Zoarcidae from the Salzhaff region, Northwest Mecklenburg, Baltic Sea, were investigated in 1995 and 1996. As many as 36 parasite species, represented by diverse groups of helminths and protozoans as well as annelids and copepods, are found during 4 seasons in these hosts. By far the most abundant group is represented by digeneans, comprising 15 species, followed by 7 cestodans and 6 nematodes. With regard to component communities, 8 host-parasite combinations are core and secondary species with more than 40% prevalence in which generalists such as the digeneans Podocotyle atomon and Cryptocotyle concavum (in 3 hosts). C. lingua, Diplostomum spathaceum, and Acanthostomum balthicum, and the nematode Hysterothylacium are involved. Also, specialists such as Aphalloides timmi in Pomatoschistus microps as well as Magnibursatus caudofilamentosa and Thersitina gasterostei in Gasterosteus aculeatus attain high levels of prevalence. A comparison of different investigations reveals greater prevalence of allogenic and autogenic parasite species with 3 host cycles in the Rerik-Riff (free Baltic) and higher levels of prevalence of autogenic parasite species with 1 or 2 host cycles in the entire Salzhaff. The component communities of gobies from Dahmeshöved, Lübeck Bight, attain generally lower degrees of prevalence than those of the Salzhaff region. The infracommunities consist mostly of 1-3 parasite species per host specimen; this value is surpassed on occasion in P. microps (maximum 7 species) and in G. aculeatus (maximum 9 species, which may compete for 5 microhabitats in a host specimen). In this context the theory of empty niches propagated by some parasitologists is critically discussed and substituted by the assumption of variable niche widths. The seasonality of the more abundant parasites is either unclear--as in the case of C. concavum--or evident--as in the case of P. atomon, which prevail in early spring and summer, or A. timmi, which dominate in late summer, as do M. caudofilamentosa, which is absent in spring. The main causes of the infestation of fish hosts may be their ages and the availability of parasites due to the presence of intermediate hosts.

[The parasitization of Gadus morhua in the southern Baltic Sea]. / Zur Parasitierung von Gadus morhua in der südlichen Ostsee.

During a survey of the working group 25 of BMB in the south of the Baltic Sea in October 1991 105 cod (Gadus morhua L.) were investigated for parasites (ICES Subdivision Areas 22, 24, 25 and 26). They were parasitized by 15 species. With increasing salinity (from east to west) and in the higher size groups more parasite species were present. Eimeria spec. in the liver and Schistocephalus spec. in the body cavity were registered for the first time in cod.

Parasites of Merluccius capensis and M. paradoxus from the coast of Namibia.

84 specimens of the sea hake Merluccius capensis and 60 of M. paradoxus were investigated parasitologically along the coast of Namibia in 1988. Between both fish species there was a high coincidence. 18 species of parasites could be stated. Distinction is remarkable between the north and south parts of the investigation area with a boundary at about 25 degrees 30' south. Southern to this border line of probably different fish stocks Brachiella merluccii is absent and the prevalence of Scolex pleuronectis and Leptotheca spec. is significantly higher. In M. capensis parasitation by Leptotheca spec., Anthocotyle merluccii and Anisakis spec. 1. is increasing with higher age groups. In M. paradoxus parasitation by Leptotheca spec. and Anthocotyle merluccii is decreasing with higher age groups and that of Clestobothrium crassiceps remains the same level.

[Capillaria merluccii spec. nov. from the sea hake Merluccius capensis and M. paradoxus from the coastal waters of Namibia]. / Capillaria merluccii spec. nov. aus den Seehechten Merluccius capensis und M. paradoxus von Küstengewässern Namibias.

The new nematode species was located in the rectum. It is described and especially compared with Capillaria gracilis (BELLINGHAM, 1844). Its position in the subgenera of the genus Capillaria ZEDER, 1800, proposed by MORAVEC (1987), is discussed.

[Acanthocolpidae (Digenea) from fish from the coast of Mozambique]. / Acanthocolpidae (Digenea) aus Fischen der Küste von Moçambique.

From the southern region of the coast of the People's Republic of Moçambique 5 new species of the family Acanthocolpidae (Digenea) out of Teleostei have been described [Monostephanostomum krusei nov. spec., Stephanostomum jesseni nov. spec., Stephanostomum keilbachi nov. spec., Stephanostomum casum (Linton, 1910) McFarlane, 1934 and S. ditrematis (Yamaguti, 1939) Manter, 1947] have been stated. In the flesh of teleostei 4 different types of metacercariae of the genus Stephanostomum Looss, 1899 were discovered. The author has summarized the known species of the genus Stephanostomum from the Indian Ocean and the species of the genus Tormopsolus Poche, 1926.

[Lepocreadiidae (Digenea) from fish on the coast of Mozambique]. / Lepocreadiidae (Digenea) aus Fischen der Küste von Moçambique.

In the Indian teleostian fishes from the coast of Moçambique were parasitized during investigations in 1980 by 7 species of the family Lepocreadiidae (ODHNER, 1905) NICOLL, 1935, (Digenea). 6 of them had not been observed in this area before. 4 species respectively one genus are described for the first time: Lepidauchen mocambiquensis nov. spec. from Abalistes stellaris, Diploproctodaeoides soleaticus nov. gen, nov. spec. from Abalistes stellaris, Bianium abalistidis nov. spec. from Abalistes stellaris, Pseudolepidapedon laticaecale nov. spec. from Lophoides mutilus.

[Demonstration of the comparative relationship of the fish genus Merluccius on the basis of parasite infestation]. / Zur Darstellung der Verwandtschaftsverhältnisse der Fischgattung Merluccius auf Grund des Parasitenbefalls.

Continuing the discussion on the theory of SZIDAT (1961) on the development and propagation of the genus Merluccius Cuvier & Rafinesque proved by infestation of parasites the digenean species Elythrophalloides merlucci SZIDAT, 1955 was investigated and declared as a synonym of Elythrophallus (Parahemirus) oatesi (leiper & Atkinson, 1914), together with Elytrophallus (P.) australis (Woolcock, 1935) and E. (P.) lovettiae (Crowcroft, 1947). Probably this species was distributed on the Pacific Coast of Gondwana. The far distances of to day distribution are to be proved by the continental drift. In favour of a northatlantic centre of development the point of view of SZIDAT is declined according to Ho (1974).

[Larvae of the order Trypanorhyncha (Cestoda) from teleosts of the Indian Ocean]. / Larven der Ordnung Trypanorhyncha (Cestoda) aus Teleostiern des Indischen Ozeans.

In the Gulf of Bengal and in the Gulf of Aden 8 species of larvae belonging to the older Trypanorhyncha (Cestoda) were found in teleosita. 3 species of the genus Nybelinia and 1 of the genus Diplootobothrium are described for the first time.

[Description of the female of a new Didymoizoidae: Gonapodasmius microovatus spec. nov]. / Beschreibung des Weibschens eines neuen Didymozoiden: Gonapodasmius microovatus spec. nov.

In Megalaspis cordyla (L.) (Perciformes, Carangidae) from the Gulf of Aden Gonapodasmius microovatus spec. nov., a trematode of the family Didymozoidae is parasitizing in the body cavity. The only preserved specimen is a mature female. Description and differential diagnose is given together with a key of determination for the genus, also a review of the geographical distribution and the fish hosts of the species of the genus Gonapodasmius.

[Metacercaria in the invertebrates of the Madras coast]. / Metazerkarien in Wirbellosen der Küste von Madras

In planktonic and benthic invertebrates of the Madras coast, Bay of Bengal, six Metacercariae have been reported. Four species are from planktonic intermediate hosts. They were found in Ctenophora, Leptomedusa and the gastropod Janthina. They belong to the Hemiurate, Fellodistomatidae and Lepocreadiidae. Two species are from benthic molluscs and belong to the family Monorchiidae respectively to the subfamily Halipeginae. We can expect that the adults of three species are not described.