Goezia bangladeshi n. sp. (Nematoda: Anisakidae) from an anadromous fish Tenualosa ilisha (Clupeidae)

A total of 1432 hilsa shad, Tenualosa ilisha (=Hilsa ilisha) from 11 fresh water, brackish water and marine localities in Bangladesh yielded 13 adult Goezia bangladeshi n. sp., all specimens being found in the intestine of a single fish host caught in the lower Ganges. A total of 2372 Goezia juveniles were recovered from 490 infected fish (prevalence 34.2%). This is the first Goezia species recorded from Bangladesh, and it differs from other valid species by the number of caudal papillae (pre 7-9, para 3, post 6); encircled by tiny spines, the position of double papillae, the arrangement of body spines, and the length ratio of the intestinal caecum and the ventricular appendix (1: 3.33-4.72). Juveniles were free in the gut, embedded in the gut wall and encapsulated in mesenteries. Tenualosa ilisha serves as the definitive host, but the predominance of juveniles may indicate that piscivorous hosts may also serve as such. A list of the nominal Goezia species with important characters is provided.     

A comparative study of the egg morphology in four species of Eubothrium (Cestoda: Pseudophyllidea) with comments on their early development

Abstract. Freshly released eggs from four species of the cestode Eubothrium ( Eubothrium crassum, Eubothrium fragile, Eubothrium rugosum , and Eubothrium salvelini ) were subjected to morphological and morphometric analysis. The eggs of the two freshwater species, E. rugosum and E. salvelini , were ovoid with a lobed embryophore whereas the eggs of the two marine species, E. crassum and E. fragile , were more circular with a smooth embryophore. However, the morphological differences between species were not readily evident to permit their clear distinction from one another. To discriminate species, a forward stepwise linear discriminant analysis, using six of the seven measured metric characters made on the eggs, was used, which gave 100% correct classification of two species, E. rugosum and E. salvelini , and a high proportion of correct classification for E. crassum (98%) and E. fragile (83%). Of the latter two species, one specimen of E . crassum and five specimens of E. fragile were misclassified between the respective groups. The principal characters used in the classification of the species were the width of the egg, the length of the mediolateral hooks, and the width of the oncosphere. To provide more information on the life cycle of each species, the eggs were used in a series of infection trials to identify appropriate intermediate hosts. Experimental infections with freshwater copepods were successful when exposed to the eggs of E . salvelini , partially successful when exposed to the eggs of marine E. crassum with 10% of the copepods becoming infected, but no infections were obtained when the eggs of E. fragile were used.     

Helminth parasites in ringed seals (Pusa hispida) from Svalbard, Norway with special emphasis on nematodes: variation with age, sex, diet, and location of host

Complete gastrointestinal tracts from 257 ringed seals (Pusa hispida) from Svalbard, Norway, were examined for helminth parasites. Three different helminth groups were recorded (acanthocephalans 61.1%; nematodes 38%; cestodes 0.9%). Acanthocephalans (Polymorphidae) and cestodes (Anophryocephalus and Diphyllobothrium sp(p)., as well as unidentified species, were confined to the intestines. The anisakid nematodes Phocascaris phocae, Pseudoterranova sp(p)., Anisakis sp(p)., and Phocascaris/Contracaecum sp(p). were recorded in both stomachs and the anterior part of the small intestines. The abundance of nematodes and acanthocephalans varied significantly with sampling location of the seal hosts. This is likely due to the relative prevalence of Arctic versus Atlantic water in the different fjord systems, which strongly influences the age class and species of fish available as prey for the seals. Adult male ringed seals had significantly higher abundances of nematodes than did adult females or juveniles. Adult males also had significantly higher abundances of acanthocephalans than did adult females, but were not significantly different from juveniles in this regard. Nematode abundance increased significantly with age of male hosts, but this trend was lacking in female seals. Infection parameters appeared to be related to differences in the age of polar cod (Boreogadus saida) exploited by male, female, and juvenile seals.     

Migration behaviour of twaite shad Alosa fallax assessed by otolith Sr:Ca and Ba:Ca profiles

Individual migration behaviour during the juvenile and adult life phase of the anadromous twaite shad Alosa fallax in the Elbe estuary was examined using otolith Sr:Ca and Ba:Ca profiles. Between hatching and the end of the first year of life, juveniles showed two migration patterns. Pattern one exhibited a single downstream migration from fresh water to the sea with no return into fresh water. In contrast, pattern two showed a first migration into the sea, then a return into fresh water and, finally, a second downstream migration into marine water. This first report of migration plasticity for A. fallax points to different exposure times to estuarine threats depending on the migration strategy. In adults, high Sr:Ca and low Ba:Ca in the majority of individuals confirmed prior reports of a primarily marine habitat use. Patterns reflecting spawning migrations were rarely observed on otoliths, possibly due to the short duration of visits to fresh water.     

Developmental and environmental regulation of chloride cells in young American shad, Alosa sapidissima

Location, abundance, and morphology of gill chloride cells were quantified during changes in osmoregulatory physiology accompanying early development in American shad, Alosa sapidissima. During the larval-juvenile transition of shad, gill chloride cells increased 3.5-fold in abundance coincident with gill formation, increased seawater tolerance, and increased Na(+),K(+)-ATPase activity. Chloride cells were found on both the primary filament and secondary lamellae in pre-migratory juveniles. Chloride cells on both the primary filament and secondary lamellae increased in abundance (1.5- to 2-fold) and size (2- to 2.5-fold) in juveniles held in fresh water from August 31 to December 1 (the period of downstream migration) under declining temperature. This proliferation of chloride cells was correlated with physiological changes associated with migration (decreased hyperosmoregulatory ability and increased gill Na(+),K(+)-ATPase activity). Increases in chloride cell size and number of fish in fresh water were delayed and of a lower magnitude when shad were maintained at constant temperature (24 degrees C). When juveniles were acclimated to seawater, chloride cell abundance on the primary filament did not (though size increased 1.5- to 2-fold), but cells on the secondary lamellae disappeared. Na(+),K(+)-ATPase was immunolocalized to chloride cells in both fresh water and seawater acclimated fish. The disappearance of chloride cells on the secondary lamellae upon seawater acclimation is evidence that their role is confined to fresh water. The proliferation of chloride cells in fresh water during the migratory-associated loss of hyperosmoregulatory ability is likely to be a compensatory mechanism for increasing ion uptake. J. Exp. Zool. 290:73-87, 2001.     

Movement into floodplain habitats by gizzard shad (<Emphasis Type="Italic">Dorosoma cepedianum</Emphasis>) revealed by dietary and stable isotope analyses

Floodplain habitats have been inferred to provide a variety of functions for aquatic organisms, yet few studies have documented movement between channel and aquatic floodplain habitats. We exploited spatial variation in stable isotope ratios of gizzard shad (Dorosoma cepedianum) to document movement between floodplain lakes and the main river channel of the Brazos River, Texas, during a period of frequent hydrologic connectivity. Additionally, we examined stomach contents of shad to determine if ontogenetic diet shifts or faunal exchange best explained variation in isotopic ratios. Regression analysis indicated significant relationships between gizzard shad size and isotopic ratios in oxbow lakes, whereas these relationships were not significant for the main channel. Plots of individual fish in each habitat suggested that adult shad migrated into oxbow lakes during floods whereas juveniles assimilated material produced in oxbows. Some adults in oxbows had signatures similar to juveniles, and these individuals were probably long-term oxbow residents. The proportion of adults with a “river” signature was greater in the oxbow with the shortest flood recurrence interval where opportunities for faunal exchange were more frequent. Analysis of stomach contents indicated almost total overlap between adult and juvenile diets indicating that movement between habitats having different isotopic ratios of basal resources rather than ontogenetic dietary shifts best explained patterns of isotopic variation in Brazos River gizzard shad.     

长江口水域鱼卵、仔稚鱼种类组成和数量的分布与变化

根据2005年4和11月、2006年4和9月在长江河口水域进行的鱼卵、仔稚鱼种类和数量调查,并结合1990年9月和1991年3月的历史数据,对该水域的鱼卵、仔稚鱼群落结构的种类组成和数量的季节变化作了研究,其结果共发现鱼卵、仔稚鱼36种(类),以海洋鱼类种类最多。秋季航次鱼卵、仔稚鱼的平均种类数和丰度均高于春季。河口咸淡水区鱼卵总数显著高于淡水区,而仔稚鱼总数略低于淡水区。与1990—1991年数据相比,2005—2006年春、秋季的鱼卵和仔稚鱼丰度均有所增加。1990、2006年秋季(9月)鱼卵、仔稚鱼种类组成差异较大,特别是翘嘴红鲌和太湖新银鱼丰度差异较大。这些都说明近20年来,长江河口水域鱼卵、仔稚鱼种类组成和数量均发生了明显的改变。     

Hatching strategies in monogenean (platyhelminth) parasites that facilitate host infection

In parasites, environmental cues may influence hatching of eggs and enhance the success of infections. The two major endoparasitic groups of parasitic platyhelminths, cestodes (tapeworms) and digeneans (flukes), typically have high fecundity, infect more than one host species, and transmit trophically. Monogeneans are parasitic flatworms that are among the most host specific of all parasites. Most are ectoparasites with relatively low fecundity and direct life cycles tied to water. They infect a single host species, usually a fish, although some are endoparasites of amphibians and aquatic chelonian reptiles. Monogenean eggs have strong shells and mostly release ciliated larvae, which, against all odds, must find, identify, and infect a suitable specific host. Some monogeneans increase their chances of finding a host by greatly extending the hatching period (possible bet-hedging). Others respond to cues for hatching such as shadows, chemicals, mechanical disturbance, and osmotic changes, most of which may be generated by the host. Hatching may be rhythmical, larvae emerging at times when the host is more vulnerable to invasion, and this may be combined with responses to other environmental cues. Different monogenean species that infect the same host species may adopt different strategies of hatching, indicating that tactics may be more complex than first thought. Control of egg assembly and egg-laying, possibly by host hormones, has permitted colonization of frogs and toads by polystomatid monogeneans. Some monogeneans further improve the chances of infection by attaching eggs to the host or by retaining eggs on, or in, the body of the parasite. The latter adaptation has led ultimately to viviparity in gyrodactylid monogeneans.     

Ultrastructure of oncospheral envelopes in Hymenolepidids (Cestoda) with aquatic life cycles

The ultrastructure of the oncospheral envelopes of five species of hymenolepidid cestodes, namely, Fimbriaria fasciolaris, Dicranotaenia coronula, Sobolevicanthus gracilis, Diorchis elisae and Diorchis ovofurcata are described. These cestodes are parasites of aquatic hosts and utilise aquatic invertebrates as intermediate hosts. The ultrastructure of the oncospheral envelopes was essentially similar among these species. However, the structure of the components of the inner oncospheral envelopes displayed significant structural variation among the five species examined. The small eggs of D. coronula and S. gracilis have a thin embryophore and oncospheral membrane. The eggs of these species settle at the bottom of the water body and are eaten by benthic crustaceans. Eggs of F. fasciolaris, D. elisae and D. ovofurcata have thick multilayered embryophores with specific ornamentation. Moreover, in Diorchis species the eggs are elongate, and the oncospheral membrane is thick and striated. Zones of electron-dense aggregates penetrate the polar filaments in these species. Eggs of F. fasciolaris float passively in water whereas those of Diorchis species are attached by long filaments to aquatic plants and are eaten by crustaceans in the littoral zone. The interrelationships among the ultrastructure of the oncospheral envelopes, cestode life cycles and habitat of crustacean intermediate hosts are drawn and discussed.     

Assessing the influence of the entomopathogenic nematode Heterorhabditis baujardi LPP7 (Rhabiditina) on embryogenesis and hatching of the plant-parasitic nematode Meloidogyne mayaguensis (Tylenchina)

Two assays were conducted to assess the influence of infective juveniles (IJs) of Heterorhabditis baujardi LPP7 on the embryogenesis and hatching of Meloidogyne mayaguensis. In the first assay, eggs were incubated in water alone or in the presence of infective juveniles, and completion of embryogenesis was evaluated 14 days later. In the second assay, unhatched second-stage juveniles were incubated in distilled water alone or in the presence of infective juveniles. Cumulative hatching was compared at various time intervals. Embryogenesis was not affected, whereas second-stage juveniles hatching was delayed probably because of the eggs permeability to noxious metabolites released by Photorhabdus luminescens, which is the bacterial symbiont of H. baujardi.     

Helminth parasites found in faecal samples of phocids from the Antarctic Peninsula

Information on helminth parasites in Antarctic phocids is scarce and fragmented. Anisakidae nematodes and Diphyllobothriidae cestodes have been reported in Antarctic and subantarctic phocids, although the prevalence and health significance remain unclear. In the present study, the presence of helminth parasites in faeces of Leptonychotes weddellii, Hydrurga leptonyx and Mirounga leonina has been investigated. Faecal samples were collected from different locations of the Antarctic Peninsula. Macroscopical inspection and standard flotation and migration techniques were used for faecal examination. Eggs, larvae and adult parasites of nematodes and cestodes were found in 76.9 % of samples analysed. Positive samples were recorded from all locations surveyed and species investigated. The prevalence was 71.3 % for M. leonina, 95.4 % for L. weddellii and 100 % for H. leptonyx. Anisakidae (eggs and worms), Metastrongyloidea (larvae) and Diphyllobothriidae (eggs) were identified in M. leonina and L. weddellii. Metastrongyloidea (larvae) and Diphyllobothriidae (eggs) were found in H. leptonyx. Molecular characterisation of some of the adult parasites found was useful for the identification of Anisakis simplex and Pseudoterranova sp. in M. leonina, and Contracaecum sp., Contracaecum osculatum, and Pseudoterranova sp. in L. weddellii.     

Morphometric analysis of four species of Eubothrium (Cestoda: Pseudophyllidea) parasites of salmonid fish: an interspecific and intraspecific comparison

Four species of the genus Eubothrium (E. crassum, E. fragile, E. rugosum and E. salvelini) were subjected to morphometric comparison. Discriminant analysis was conducted utilising 17 characters measured on the scolex and strobila of 101 specimens. Univariate statistics were first used to detect features that were useful for separating individual Eubothrium species and two different host populations of E. salvelini. Subsequent multivariate discriminant analysis, combining all the measured variables, made it possible to separate all four species. A comparison of the four taxa revealed that (1) E. fragile is the most distinct species, possessing a much smaller scolex than the other congeners, and its similarity with the other marine species E. crassum is not proven; (2) the two freshwater taxa, E. rugosum and E. salvelini are the most similar; (3) the characters most suitable for species differentiation are the length of the scolex, the width of the apical disc, the width of the neck and its area, the width of eggs and the number of testes; (4) the width of the apical disc was confirmed to be the most stable character at the intraspecific level (within E. salvelini host populations) and is therefore considered to be a trait of the highest discriminative power in the subset of four Eubothrium species.     

The diet of juvenile and adult twaite shad Alosa fallax fallax (lacépède) from the rivers Severn and Wye (Britain)

The diet of juvenile and adult twaite shad was studied at a number of freshwater and estuarine sites in the rivers Severn and Wye and in the coastal waters of Cardigan Bay (West Wales). In the Severn estuary and in the freshwater reaches of the Severn and Wye, adult twaite shad consumed little during their pre-spawning migration. In the Severn Estuary post-spawning adults were present during the summer months where they fed actively on mysids, gammarids and shrimps. Mysids dominated the diet of the adults caught in coastal waters during the autumn. The diet of one year old twaite shad was studied in the Severn Estuary. In May the one year olds from the lower estuary consumed mainly gammarids. During the summer months, this age-class moved into the inner estuary where they fed predominantly on mysids.The larvae and juveniles (age 0⁺) fed mainly on chironomid larvae and pupae and Simuliidae larvae, while in fresh water. In the estuary copepods, cladocerans and mysids dominated the diet of the juveniles. There was some suggestion of an increase in prey size during their period of residency in the estuary. The contrasting distribution of the juveniles in two river systems is discussed in relation to the effects of channelization.     

The phylogeny of the Gregarinia (Sporozoa)

The Gregarinia, all parasitic in invertebrates have appeared in marine hosts (Polychaeta). The most primitive are the Archigregarinida (Selenidium) which are intestinal parasites. The Eugreganida (intestinal or coelomic) are found in various marine invertebrates as well as in terrestrial or fresh water arthropods. The Neogregarinida which parasitize only insects have a very reduced number of spores compensated by a schizogony (merogony). The Gregarinia constitute a perfect example of a concomitant evolution between a group of parasites and their hosts.     

Parasite fauna of bream Abramis brama and roach Rutilus rutilus from a man-made waterway and a freshwater habitat in northern Germany

Fifty specimens each of bream Abramis brama and roach Rutilus rutilus were examined for metazoan parasite fauna and trichodinid ciliates; 25 specimens of each species were collected from the Kiel Canal, a man-made waterway, and a nearby freshwater lake, the Dieksee. This is the first detailed parasitological examination of A. brama and R. rutilus at these locations: 30 parasite species were found, comprising 4 protozoans, 4 myxozoans, 5 digeneans, 3 monogeneans, 2 cestodes, 6 nematodes, 2 acanthocephalans, 3 crustaceans and 1 hirudinean. The crustacean Caligus lacustris occurred in both habitats while 2 other crustacean species, 2 acanthocephalans and 1 hirudinean were recorded exclusively for the lake habitat. Larval as well as adult stages of the different parasite species were found, indicating that both fish species act as intermediate and final hosts in both habitats. The Kiel Canal (total of 17 parasite species) showed a lower parasite species richness for A. brama and R. rutilus (14 and 10 parasite species, respectively) than the lake (25 parasite species). A. brama had a higher parasite richness (22 species) than R. rutilus (16 species) in the lake habitat. Most parasites collected were of freshwater origin. Consequently, the observed infection pattern of both fish species in the waterway is mainly influenced by the limited salinity tolerance of freshwater parasites, which are negatively affected even by a salinity of 2.3 to 4.5. In the central Kiel Canal, neither fish species was infected with marine parasites of low host specifity. These parasites are either limited by the low salinity at this sampling site (<4.5 to 6.0) or they cannot enter the canal due to the environmental conditions prevailing in this artificial brackish water habitat. Thus, the canal may comprise a natural barrier preventing the distribution of North Sea parasites into the Baltic Sea. However, the brackish water Baltic Sea nematodes Paracuaria adunca and Cosmocephalus obvelatus were found in R. rutilus from the canal, demonstrating the ability of some parasite species to invade and extend their range of distribution through this man-made shipping route from the Baltic to the North Sea.     

In Vitro Cultivation of Cymatocarpus solearis (Brachycoeliidae) Metacercariae to Obtain the Adult Stage without the Marine Turtle Definitive Host

In vitro cultivation of trematodes would assist studies on the basic biology of the parasites and their hosts. This is the first study to use the yolk of unfertilized chicken eggs as a simple and successful method of ovocultivation and the first time to obtain the adult-stage of the trematode Cymatocarpus solearis Braun, 1899 (Digenea: Brachycoeliidae). Chicken eggs were inoculated with metacercariae from the muscle of the spiny lobster, Panulirus argus (Latreille, 1804). The metacercariae were excysted and incubated for 576 hr (24 days) at 38℃ to obtain the adult stage. Eggs in utero were normal in shape and light brown color. The metacercariae developed into mature parasites that have been identified as the adult-stage found in marine turtles. The adult lobsters collected in Quintana Roo State, Mexico, showed the prevalence of 49.4% and the mean intensity of 26.0 per host (n = 87). A statistical study was performed to determine that no parasitic preference was detected for male versus female parasitized lobsters. Morphometric measurements of the adult-stage of C. solearis obtained in our study have been deposited in the National Helminths Collection of the Institute of Biology of the National Autonomous University of Mexico. This study is significant because it is the first time that a digenean of the family Brachycoeliidae has been demonstrated to develop in vitro from metacercariae into adults capable of producing eggs using the yolk of unfertilized chicken eggs. Secondly, this technique allows to obtain the adult stage of C. solearis without the presence of its marine turtle host, allows us to describe the mature parasites, and thus contribute to our understanding of the biology of C. solearis.     

Is the elusive Gymnothorax polyuranodon really a freshwater moray?

Analysis of 36 records of the rarely encountered moray Gymnothorax polyuranodon indicate that juveniles and adults inhabit fresh and mildly brackish habitats (salinity < 5) in streams of the Australian Wet Tropics Eighty-one per cent of these records were from freshwater streams and collectively demonstrate that this species inhabits fresh water throughout all seasons. A survey of fish researchers, each with at least 100 h of field experience in Australia's Wet Tropics, revealed that 33% of researchers working in fresh waters (nine of 27 researchers) had encountered the species and 15% of researchers with substantial experience working in estuaries (two of 13 researchers) had encountered the species. The species was not sampled or observed in the nearshore marine environment. The only record of an elver of this species was, however, found in an estuary at a salinity of 33·4. This preliminary evidence suggests adult G. polyuranodon occupy freshwater habitats, but further research is required to understand the complete life cycle, including movements, habitat use and reproductive ecology of the species.     

Drought tolerance in eggs and juveniles of the Iberian slug, <Emphasis Type="Italic">Arion lusitanicus</Emphasis>

The spread of invasive species is an increasing problem world wide. The invasive slug Arion lusitanicus has spread to most parts of Europe, where it often is considered as a serious pest. There is a need for better knowledge of its ecophysiology to be able to predict the effect of climatic factors, such as temperature and humidity on the population dynamics and abundance. The aim of the present study was to assemble data on the water balance and drought tolerance of eggs and juveniles of A. lusitanicus. Both eggs and juveniles had little capacity to prevent evaporative water loss and lost water when the ambient humidity fell below 99.8 and 99.5%, respectively. The water conductance of the cuticle of juveniles was 242 μg cm⁻² h⁻¹ mmHg⁻¹ and resembles that of other slug species. Both eggs and juveniles of A. lusitanicus tolerate a substantial water loss. There was no difference in water loss resistance between eggs and juveniles, but the eggs were slightly more tolerant to water loss than the juveniles. The percent water loss causing 50% mortality was 72% for the juveniles and 81% for the eggs. Despite A. lusitanicus’ tolerance of substantial water loss, its survival depends on humid habitats.