Metacercariae of Diplostomum spathaceum in the eyes of fishes from Yellowstone Lake, Wyoming

Fish were collected from Yellowstone Lake, Wyoming (USA). Metacercariae of Diplostomum spathaceum was found in the lens of 11 of 12 longnose suckers (Catostomus catostomus). The mean number of metacercariae per sucker was 59 and the average age of the fish was 11.6 yr. There was no correlation between age and intensity of parasites (r = 0.24). Of 10 cutthroat trout (Salmo clarki) examined, there were metacercariae present in six. The metacercariae were found outside of the lens tissue in the trout; they occurred in the vitreous humor and the retina. These may be a different species from those found in the suckers.     

On the development of body-wall musculature Diplostomum chromatophorum metacercariae (Trematoda: Diplostomidae)

The body-wall musculature of invasive cercariae and metacercariae of Diplostomum chromatophorum at different intervals after the penetration into the experimental intermediate host Cyprinus carpio (1, 3, 5, 6, 7, 10, 12, 20, 34, 40 days) has been investigated with the help of TEM technique. During the first 10 days after the invasion (in conditions of our experiment), the cercarial subtegumental muscle fibres degenerate. These muscles are replaced by newly formed ones. Mass differentiation of myoblasts beneath the tegument was observed in 7-10-day-old metacercariae. Obtained data indicate the metamorphosis of body-wall musculature during the morphogenesis in Diplostomum chromatophorum metacercariae.     

Toxicity of cadmium and zinc to Diplostomum spathaceum (Trematoda: Diplostomidae) cercarial survival

The toxicity of cadmium and zinc at concentrations ranging from 0.1 to 10000 microg/l was investigated with cercariae of Diplostomum spathaceum at three temperatures (12, 20, 25 degrees C) and three levels of water hardness (distilled water, soft water, hard water). Under most environmental conditions survival of cercariae was reduced by increasing metal concentration. Increasing water hardness and decreasing water temperature caused an increase in the survival of both control and metal exposed cercariae. However, with decreasing temperature increased survival of metal-exposed cercariae above the control occurred at a number of low metal concentrations. Differences in the relative toxicity of cadmium and zinc to cercariae was dependent on the environmental conditions of exposure. The two heavy metals demonstrated little toxicity to cercariae during the period of maximum cercarial infectivity (0-5 h).The mechanisms of metal toxicity and their effects on cercarial survival are discussed.     

Carassotrema koreanum Park, 1938 (Trematoda, Waretrematidae) and a new species of this genus from fresh water fishes of North Vietnam]

In freshwater fishes of North Viet-Nam were found representatives of the family Waretrematidae, Carassotrema koreanum and a new species of this genus, C. ginezinskajae sp. n., close to C. koreanum and differing from it in the structure and extent of yolk glands, relatively larger sizes of the pharynx and suckers, the location of spines and body shape. The described species differs from the other species of this genus, C. mugilicola, in the shape and location of testis, structure and location of yolk glands, intestine extent, size of suckers and pharynx, presence of cirrus, location of spines on the body and in other characters. Asymphylodora pavlovskajae Ha Ky, 1969 and Asymphylodora ginezinskajae Ha Ky, 1969 are reduced to synonyms of Carassotrema koreanum and C. ginezinskajae sp. n.     

Genetic divergence among morphotypes of Lake Tana (Ethiopia) barbs

The genus Barbus is a paraphyletic assemblage that includes three different ploidy levels: diploid, tetraploid and hexaploid. 'B.' intermedins , which inhabits Lake Tana (Ethiopia), is a hexaploid taxon that forms a 'species flock' consisting of at least 14 morphotypes. Thirty-one presumptive allozymic loci were analysed in a large sample of 'B.' intermedius. No diagnostic loci were observed between the morphotypes, but substantial differences in allele frequencies were found. One morphotype, Acute, differs significantly from the others. The presence of this genetic differentiation within the lake strongly suggests that the morphotypes are diverging lineages. Because of some parallel characteristics with cichlid species flocks, we put forward the hypothesis that the morphotypes of barbs in Lake Tana represent a species flock that originated via sympatric speciation with more rapid morphological than molecular differentiation. If the differentiation and the reproductive isolation are real, it is probable that the morphotypes already are or will soon reach the status of species.     

Spawning migrations of the endemic Labeobarbus (Cyprinidae, Teleostei) species of Lake Tana, Ethiopia: status and threats

The reproductive biology of the only known intact species flock of large cyprinids, the 16 Labeobarbus species of Lake Tana (Ethiopia), has been extensively studied for the past two decades. Seven species of Labeobarbus are known to migrate >50 km upstream into tributary rivers for spawning during the rainy season (July to October), whereas eight other species are absent from these rivers and probably developed a new strategy of lacustrine spawning (macro-spatial segregation). One species (L. intermedius) probably spawns in the lake as well as in the rivers. Between the early 1990s and 2000s, the riverine spawners showed a decline of 75% in both biomass and number in both fishery independent surveys and in commercial catches. Reproductive migration makes fishes vulnerable to fisheries and other threats like habitat modifications. Lacustrine spawners are probably more resilient as they are not known to form spawning aggregations that can easily be exploited by fishermen. In addition, upstream rivers and catchments around Lake Tana are highly degraded by erosion and recently subjected to intensive habitat modification for irrigation and hydroelectric power generation. This article reviews results of field studies on the Labeobarbus spawning migration from Lake Tana to spawning rivers, giving emphasis on segregation and homing. It also summarizes existing and emerging threats which form potential causes for the decline of the migratory Labeobarbus species. Knowledge gaps on the reproductive biology are identified for further investigation.     

A new oribatid mite species of the genus Protoribates (Acari,Oribatida, Haplozetidae) from Ethiopia

A new oribatid mite species, Protoribates aethiopicus sp. n., from Ethiopia is described. This species is morphologically similar to Protoribates dentatus (Berlese, 1883), but differs from it in the longer lamellae and notogastral setae, shorter adanal setae ad ₁ and smaller notogastral porous areas, as well as in the presence of two claws on all legs.     

Shallow genetic divergence and species delineations in the endemic Labeobarbus species flock of Lake Tana,Ethiopia

To assess whether the species distinctions of Lake Tana's Labeobarbus spp. are supported by genetic information, microsatellite markers were used. A total of 376 Labeobarbus spp., belonging to 24 populations of 11 species from three regions of the lake (north, south and east), were sampled. Eight microsatellite markers were analysed. In general, differences between conspecific populations were smaller than differences between populations of different species. For six species, conspecific populations from different regions in the lake were consistently more similar than populations of other species from the same region. For four species this was not the case, while for one species two populations were similar, but different from the third population. River‐spawning species appeared to be more distinct than presumed lake spawners. On the species level, there was a significant correlation between genetic and morphological differentiation, especially in morphological aspects associated with ecological functioning. This suggests that genetic differentiation arose together with adaptive radiation, although the overall genetic differentiation among the Lake Tana Labeobarbus spp. is small.     

Trematode metacercariae from the cranial cavity of African catfish Clarias gariepinus (Burchell, 1822) from Lake Tana,Ethiopia

Metacercariae of two species of trematodes from the fam. Diplostomidae from the cranial cavity of the African catfish Clarias gariepinus are described. The metacercaria Tylodelphys grandis n. sp. is described for the first time. Data are presented on the infection rate of catfishes in Lake Tana.     

A new genus and species of Macroderoididae, and other digeneans from fishes of Lake Malawi, Africa

Malawitrema staufferi n. gen., n. sp., an unusual digenean, is described from Clarias mossambicus (type host) and Bagrus meridionalis from Lake Malawi. It has a small, pyriform body, with a spinous tegument. The ceca are relative short, not reaching to the testes. The 2 testes are symmetrical in the middle hind body. The cirrus sac is long and narrow, reaching into hind body. The genital pore is median, immediately anterior to the ventral sucker. The ovary is pretesticular, and a canalicular seminal vesicle and Laurer's canal are present. The uterus usually reaches distinctly posteriorly to testes. The eggs are small. The follicular vitellarium is in 2 small fields just anterior to testes. The ventrally subterminal excretory pore leads to a claviform vesicle. This species does not fit clearly into any known family of digeneans and is placed in the Macroderoididae as a temporary measure. Other digeneans reported from Lake Malawi include Haplorchoides cahirinus (Looss, 1896) in C. mossambicus and B. meridionalis; Astiotrema turneri Bray, van Oosterhout, Blais & Cable, 2006 in Protomelas annectens, P. cf. taeniolatus, Labeotropheus fuelleborni, Ctenopharynx (Otopharynx) pictus, and Pseudotropheus zebra; Glossidium pedatum Looss, 1899 in C. mossambicus and B. meridionalis; and an unidentifiable sanguinicolid from Bathyclarias nyasensis.     

Systematic analysis of the Diplostomidae and Strigeidae (Trematoda)

A systematic analysis of the genera in the Diplostomidae and Strigeidae was made using the Proterodiplostomidae as the outgroup. The Proterodiplostomidae was the family with the greatest preponderance of primitive characters and its monophyly was supported by the unique paraprostate gland. However, no character state supported the monophyly of the Diplostomidae sensu Dubois, 1970. That paraphyletic taxon was composed of 3 monophyletic groups: the pseudosuckerless Neodiplostomidae n. fam. had the most primitive character states of the 3 and its monophyly was based on characters in the neascus/neodiplostomulum metacercariae; the Bolbophoridae n. fam., with pseudosuckers, had its monophyly supported by characters present in the newly named prodiplostomulum metacercaria; and the emended Diplostomidae, also with pseudosuckers, had the most derived states and its monophyly was supported by characters present in the diplostomulum. The presence of pseudosuckers united the Bolbophoridae n. fam., the emended Diplostomidae, and the Strigeidae as a monophyletic assemblage. The Strigeidae had the most derived characters of these 3 taxa and its monophyly was supported by characters in the tetracotyle and the cup-shaped forebody and bilobed tribocytic organ of the adult. In general, the adult stages of these strigeoid families showed very conserved morphology and it was the metacercariae that possessed the innovations. The conserved adult morphology was typical of what one might expect if the intramolluscan stages were analyzed. Thus, the data were concordant with the view that the mollusc and vertebrate definitive host were the original hosts to the Digenea and that the second intermediate host and metacercaria were more recently intercalated. More specifically, the phylogeny of these groups suggested that ancestral bisegmented strigeoids originally infected reptiles, they subsequently radiated into birds with which they coevolved extensively, and on 5 separate occasions they radiated into mammals. The radiations into mammals were, by all available evidence, preceded by second intermediate host shifts from fish to amphibians.     

Species affiliation of metacercaria of the genus Metorchis (Trematoda, Opisthorchidae) from fishes in Western Siberia

Two larval species of the genus Metorchis, M. bilis and M. xanthosomus, are reported from fishes of West Siberia. Larvae of the first species can develop into adult forms in birds (terns, gulls, ducks) and in mammals (cats, golden hamsters, white mice). Larvae of the second species developed only in ducks. Experimental infection of golden hamsters, white mice and black terns with M. xanthosomus failed. On the results of the experimental infection and literary data the synonyms, M. bilis and M. xanthosomus, are given.