Structure of parasite component communities of didelphid marsupials: insights from a comparative study

The parasite fauna of the gray four-eyed opossum, Philander opossum (Linnaeus, 1758), and the common opossum, Didelphis marsupialis Linnaeus, 1758, in Camp du Tigre, French Guiana, is characterized. Nine species from the gastrointestinal system were recovered from both species, which shared 80% of their parasites. The parasite fauna comprised several monoxenous species (63%) and was dominated by Aspidodera raillieti Travassos, 1914, which exhibited high levels of prevalence and abundance in both communities. Only 2 species (Moennigia sp. and Spirura guianensis) had been recorded in other species of mammals. Both species richness and taxonomic composition at the level of component communities from this locality were compared against 11 communities present in the Virginia ( Didelphis virginiana ), white-bellied (Didelphis albiventris), and common opossum from Argentina, Brazil, Mexico, and the United States. Neither host phylogeny nor taxonomy accounted for statistical differences in species richness. There was no statistical difference among species richness values among the 9 localities studied. Taxonomic similarity was analyzed by means of the Jaccard's similarity index, including all, and only common species (occurring in prevalence >10%). The results suggest that sympatric species of marsupials share more species of parasites than parasite communities occurring in conspecific marsupials from different localities. As a consequence, taxonomic composition of these parasite communities varied depending on the locality. Probably, marsupials of the monophyletic Didelphini offer the same compatibility toward their parasites, by presenting them with similar habitats. Subtle differences in lifestyles of the marsupials may determine the chance of encounter between the symbionts and prevent some parasites from completing their life cycles. Further and more rigorous tests are necessary to determine the roles of encounter and compatibility filters, as well as the role of chance, in the structuring of parasite communities in marsupials.     

Predicting the similarity of parasite communities in freshwater fishes using the phylogeny,ecology and proximity of hosts

Parasite communities tend to be dissimilar in hosts that are geographically, phylogenetically, ecologically and developmentally distant from one another. The decay of community similarity is a powerful and increasingly common method of studying parasite beta diversity, but most studies have examined only a single type of distance. Here, we evaluate distances based on the phylogeny, ecology, spatial proximity and size of hosts, as predictors of the similarity of parasite communities in individual hosts, host populations and host species. We surveyed parasites in six species of fish collected simultaneously from six localities in the St. Lawrence River, Canada, and species in a common group of larval parasites were discriminated using DNA sequences from barcode region of cytochrome c oxidase I. Distances based on the habitat use patterns of host species were good predictors of short‐term, ecological similarity of parasite communities, such as that operating at the scale of the individual host. The genetic distance between host species was associated with almost all types of similarity at all scales, particularly qualitative and phylogenetic similarity of parasite communities at the level of populations and meta‐populations of hosts. The trophic level, diet, spatial proximity and size of hosts were poor predictors of parasite community similarity. The increased taxonomic resolution provided by molecular data increased the explanatory power of regression models, and different factors were implicated when parasite species were distinguished with DNA barcodes than when larval parasites were lumped into morphospecies, as is commonly practiced.     

长江中下游三个湖泊中鳜消化道寄生蠕虫群落的组成与多样性

鱼类在食物网中的营养位置对其消化道寄生蠕虫的群落结构有重要作用。本研究调查了梁子湖、洞庭湖、鄱阳湖中鳜(Siniperca chuatsi)消化道寄生蠕虫群落的组成和多样性。在3个湖泊中共发现11种寄生蠕虫, 优势种均为范尼道佛吸虫(Dollfustrema vaneyi), 频率分布中感染有12种寄生虫的样本占65%, 单个样本中最大物种数为6。3个湖泊中平均物种丰富度为1.532.13, Brillouin多样性指数为0.120.33, 其中鄱阳湖中的多样性最高。梁子湖和洞庭湖之间的Jaccard相似度和百分比相似指数最高。通过比较食物网中不同营养位置鱼类的消化道寄生蠕虫群落结构, 发现鳜的消化道寄生虫群落的物种丰富度与多样性水平都高于植食性和杂食性鱼类。研究还讨论了宿主食物组成对消化道寄生蠕虫群落结构的影响。       

Parasites of forage fishes in the vicinity of Steller sea lion (Eumetopias jubatus) habitat in Alaska

Fish serve as intermediate hosts for a number of larval parasites that have the potential of maturing in marine mammals such as Steller sea lions (Eumetopias jubatus). We examined the prevalence of parasites from 229 fish collected between March and July 2002 near two islands used by Steller sea lions in Southeast Alaska and island habitats in the Aleutian Islands. Sea lion populations have remained steady in Southeast Alaska but have been declining over the last 30 yr in the Aleutian Islands. Even though the fish samples near the Southeast Alaska haul-outs were composed of numerous small species of fish and the Aleutian Islands catch was dominated by juveniles of commercially harvested species, the parasite fauna was similar at all locations. Eleven of the 20 parasite taxa identified were in their larval stage in the fish hosts, several of which have been described from mammalian final hosts. Four species of parasite were more prevalent in Southeast Alaska fish samples, and seven parasite species, including several larval forms capable of infecting marine mammals, were more prevalent in fish from the Aleutian Islands. Nevertheless, parasites available to Steller sea lions from common fish prey are not likely to be a major factor in the decline of this marine mammal species.     

Peculiarities of the parasitofauna of Atlantic salmon parr (Salmo salar L.), brown trout (Salmo truttae L.), and char (Salvelinus alpinus L.) in the Utsjoki River system (Northern Finland)

Data on the parasite diversity in Salmonidae fish parr from different parts of the Utsjoki River obtained during 1993-1995 and 2006-2007 are presented. Three fish species, Salmo salar L., S. truttae L., and Salvelinus alpinus L., were examined on the presence of helminthes. Twenty species of salmon parasites were found, the majority of which are the parasites with complicated life cycles. Infusorians C apriniana piscium, myxosporidia Chloromyxum januaricus and Myxobolus neurobius, metacercaria of the genera Diplostomum and Apatemon, and the nematode Raphidascaris acus larvae were the most numerous in salmon parasite fauna. Brown trout had the most number of specific parasite species, whereas char was infested by protozoan parasites only.     

Parasites as biological tags for Eleginops maclovinus (Teleostei: Eleginopidae) around the Falkland Islands

This is the first study of the parasite fauna of Eleginops maclovinus in the Falkland Islands. It was undertaken to catalogue the parasite fauna of E. maclovinus in order to provide a baseline for future studies and to determine whether parasites might be used as biological tags. Between 21 January and 17 March 2002 samples were taken from three stations, Teal Creek (30 fish), Port Louis (30 fish) and Camilla Creek (10 fish), all in East Falkland, and examined for protozoan and metazoan parasites. Twenty-four parasite taxa were recorded, of which three were possible new species, two new host records and five new geographical records. Because of the small number of fish in the Camilla Creek sample it was excluded from further analyses. E. maclovinus is a protandrous hermaphrodite and all fish greater than 53 cm total length were found to be female, so these too were excluded from further analyses. The parasite data from the remaining fish were analysed by an agglomerative hierarchical cluster analysis using an average linkage and a Jaccard measure of similarity, followed by a linear discriminant function analysis (LDA). Both analyses misclassified only one fish from Port Louis as being from Teal Creek, with the LDA giving an overall correct classification of 97.5% (39/40). The results support mechanical tagging data in suggesting that smaller male E. maclovinus are resident in the creeks in which they are caught, and that at this stage of their lives they tend not to migrate over long distances.     

Parasite fauna of seabass (Lates calcarifer) under mariculture conditions in Lampung Bay, Indonesia

Fish parasites have been repeatedly reported to be a major threat to the developing industry of finfish mariculture in Indonesia, due to severe parasite and disease outbreaks. The aim of this study was to identify the metazoan parasite fauna and trichodinid ciliates that infect Lates calcarifer in a representative mariculture farm in Indonesia. Examined were 105 L. calcarifer (seabass) for the metazoan parasite fauna and trichodinid ciliates. Thirty‐five specimens each from the net cages of the National Sea Farming Development Centre (Balai Budidaya Laut, BBL) in Lampung Bay, South Sumatra, Indonesia were investigated in three consecutive seasons (two dry and one rainy season from 2002 to 2003). Nineteen parasite species were identified; all fish specimens were infected with two to 10 parasite species, demonstrating a species‐rich parasite fauna. Protozoans (1 species), myxozoans (1), digeneans (3), monogeneans (5), cestodes (3), nematodes (5) and acanthocephalans (1) were found, including 11 new host records in cultured L. calcarifer from Indonesia. Larval and adult parasite stages were isolated, demonstrating that this fish species, although kept inside the net cages, still functions as an intermediate and final host for marine fish parasites. During all seasons, the six detected monoxenous (single host life cycle) parasite species showed a higher prevalence than the 13 heteroxenous (multiple hosts) species. Most abundant were the fish pathogenic monogeneans Pseudorhabdosynochus epinepheli, Pseudorhabdosynochus lantauensis, Benedenia epinepheli and Neobenedenia melleni with a high prevalence. Most heteroxenous parasites (Digenea, Cestoda, Nematoda and Acanthocephala) occurred with a low prevalence below 26%, caused by the specific culture conditions. Diversity of the heteroxenous parasites was higher in the dry seasons than in the rainy season. Though some seasonality could be observed for the fish pathogenic monogeneans, severe disease outbreaks of these ectoparasites cannot be excluded in either the dry or rainy season.     

Some remarks on parasitic infections of the invasive Neogobius spp. (Pisces) in the Hungarian reaches of the Danube River, with a description of Goussia szekelyi sp. n. (Apicomplexa: Eimeriidae)

During a survey of the parasite fauna Neogobius spp., which only recently invaded Hungarian reaches of the Danube River upstream from Budapest, it was found that Neogobius melanostomus and N. fluviatilis had become common species. Neogobius kessleri was less frequent and the previously widespread Proterorhinus marmoratus was drastically reduced. The parasite fauna of the newcomer fish species was characterized by ubiquitous parasites of a wide host range, such as the trematode Nicolla skrjabini, the metacercariae of Metagonimus yokogawai and Apatemon cobitidis, the larval stages of the acanthocephalan Pomphorhynchus laevis and the nematode Rhaphidascaris acus, the glochidia of an Anodonta sp. (Mollusca) and the ciliophoran Ichthyophthirius multifiliis. The specific parasites of Neogobius spp. were represented by three intestinal coccidia: Eimeria daviesae, Goussia kessleri, and a new species described here as Goussia szekelyi sp. n. This survey showed that the rapid invasion of Ponto‐Caspian gobies in the northern Danube caused important changes in the fish fauna composition of the Danube River and enriched the parasite fauna of Hungarian fishes.     

Metazoan parasite communities of sentinel bluegill caged in two urbanizing streams, San Antonio, Texas

Urbanization has deleterious effects on water quality and biota in stream systems. This project used caged bluegill (Lepomis macrochirus) to assess metazoan fish parasite communities in 2 urbanizing streams of the upper San Antonio River Basin, Bexar County, Texas. Field studies on Leon and Salado creeks were conducted during late summer in 1999 and 2000. Juvenile bluegill, obtained from a local aquaculturist, were held in cages for 10-22 days at middle and lower watershed sites to expose them to in-stream conditions and to allow parasite communities to establish. After removal from cages, fish were examined for metazoan parasites. In 2000, wild Lepomis spp. also were collected at study sites for parasite assessment. In both years, physical and chemical water properties were monitored at each site. Of the 120 fish examined for parasites, 96.7% were infected by at least 1 organism from among the 11 parasitic taxa observed. For caged fish, both diversity and equitability of parasite communities tended to be lower at the more eutrophic downstream sites; accordingly, parasite diversity and equitability were inversely correlated with nitrate concentrations. Ectoparasites were more prevalent in caged fish and endoparasites were more abundant in wild fish. An Ergasilus sp. copepod and a Posthodiplostomum sp. trematode dominated the ecto- and endoparasite faunas, respectively. This study suggests that assessment of watershed health can benefit from comparative cage studies of parasite community development involving sentinel fish species.     

南极鱼类后生动物寄生虫研究进展: 线虫、绦虫与桡足类

极端的环境造就了南极独特的生物群体, 其中鱼类是南大洋生态系统中最具多样性的脊椎动物, 也是许多寄生虫的中间或终末宿主。南极鱼类寄生虫种类丰富, 是南大洋海洋生物多样性的重要组成部分。探究南极鱼类及其寄生虫的营养关系可为阐释南极海洋生态系统功能及其变动提供重要的生态数据。虽然关于南极鱼类寄生虫的研究已有一百多年的历史, 但这些研究主要集中在寄生虫的种类鉴定、区系调查和组织病理等方面。由于南极鱼类寄生虫研究跨度时间长、地域范围广, 相关研究较为零散。文章综述了南极鱼类寄生线虫、绦虫以及桡足类的种类组成、宿主范围和地理分布等方面的研究, 并对今后开展南极鱼类寄生虫研究工作提出了展望。     

Downstream changes in the composition of the parasite community of fishes in an Appalachian stream

The spatial distribution of 6 parasite species (Myxobolus sp., Dactylogyrus sp., Sterliadochona ephemeridarum, Plagioporus sinitsini, Allopodocotyle chiliticorum, Allocreadium lucyae) was studied in 5 species of fishes (Oncorhynchus mykiss, Clinostomus funduloides, Notropis chiliticus, Rhinichthys atratulus, Semotilus atromaculatus) in Basin Creek, an Appalachian stream in North Carolina. Nonmetric multidimensional scaling and vector fitting were used to determine if the proximity of sampling sites was related to community similarity. Position along Basin Creek was significantly related to parasite community structure. Breaks in parasite community composition were imposed by waterfalls at upstream areas of Basin Creek that restricted distributions of C. funduloides, N. chiliticus, and S. atromaculatus and at the downstream limit of the study area by a break in the distribution of S. ephemeridarum coincident with the existence of a dam but were independent of suitable piscine host distributions. These discontinuities in parasite community composition imply that the relationship between proximity of sites and community similarity is predictive because distance between sites is related to the probability that fish at different sampling sites recruit parasites from different species pools. This relationship is not the same for all component communities.     

Biogeography of helminth parasites of freshwater fishes in Mexico: the search for patterns and processes

Aim To uncover and describe patterns of biogeography of helminth parasites in freshwater fishes of Mexico, and to understand processes that determine them. Three predictions about host‐specificity, faunal exchange in transitional areas, and the biogeographical ‘core’ fauna, are evaluated, all of which follow from a fundamental hypothesis: that parasites show characteristic associations with particular host clades. The parasite fauna of the southern Mexican cichlids and of the fishes of the Mesa Central are examined as case studies that reflect Neotropical and Nearctic historical influences. Location The region covered in this study includes most of Mexico, with emphasis on six biogeographical areas: the Yucatán Peninsula (area 1), the Grijalva‐Usumacinta drainage (area 2), the Papaloapan and Pánuco drainages (area 3), the Balsas drainage (area 4), the Lerma‐Santiago drainage (area 5), and the Bravo drainage (area 6). Methods A parasite data base containing all the records of helminth parasites of freshwater fishes of Mexico was filtered to extract records of adult helminth parasites in freshwater fishes from the six biogeographical areas designated in this study. Jaccard's similarity coefficients and cluster analyses (using upgma ) were used to analyse the extent of faunal similarity between the designated biogeographical areas and between host (fish) families. Taxonomic composition of parasite assemblages in different host groups was also qualitatively compared from summary data. These data were used to test the three main predictions. Results To date, 184 species of helminths (120 as adults) have been recorded from 127 freshwater fishes in Mexico (almost 33% of the total fish diversity of Mexico). Of these parasite species, 69 are digenetic flukes, 51 are nematodes, 33 are monogeneans, 25 are tapeworms, and only six are acanthocephalans. The data and analyses from the six biogeographical areas corroborate the predictions that: (1) the adult parasite fauna is largely circumscribed by higher levels of monophyletic host taxa (families, orders, etc.), and that this pattern is independent of areas; (2) areas within a certain biogeographical region, and consequently with similar fish composition (e.g. areas 1, 2 and 3) have more similar parasite faunas compared to areas with less similar fish faunal composition; and (3) ‘core’ parasite faunas persist to some extent in transitional areas with limited host‐sharing. Main conclusions Helminth biodiversity in Mexican freshwater fishes is determined by the historical and contemporary biogeography of their hosts. Host lineage specificity, mainly at the level of the host family, appears to be an important factor in the distribution of the parasites. Most fish families (Characidae, Cichlidae, Pimelodidae, Ictaluridae, Catsotomidae, Goodeidae, Atherinidae) possess their own characteristic ‘core’ helminth fauna, with limited host‐sharing in transitional areas (e.g. areas 3 and 4). A re‐evaluation of the helminth fauna of Mexican cichlids questions the hypothesis that cichlids lost parasites during the colonization of Mexico from South America. The evidence supports the idea that they acquired new parasites by host switching, possibly from marine or brackish‐water percomorphs. In contrast, the parasite fauna of the Mesa Central remains enigmatic and reflects the region's history of endemicity with historical marine and Nearctic connections.     

Food borne parasites as indicators of trophic segregation between Arctic charr and brown trout

The habitat and diet choice and the infection (prevalence and abundance) of trophically transmitted parasites were compared in Arctic charr and brown trout living sympatrically in two lakes in northern Norway. Arctic charr were found in all main lake habitats, whereas the brown trout were almost exclusively found in the littoral zone. In both lakes the parasite fauna reflected the niche segregation between trout and charr. Surface insects were most common in the diet of trout, but transmit few parasites, and accordingly the brown trout had a relatively low diversity and abundance of parasites. Parasites transmitted by benthic prey such as Gammarus and insect larva, were common in both salmonid host species. Copepod transmitted parasites were much more common in Arctic charr, as brown trout did not include zooplankton in their diets. Parasite species that may use small fish as transport hosts, were far more abundant in piscivorous fish, especially brown trout. The seasonal dynamics in parasite infection were also consistent with the developments in the diet throughout the year. The study demonstrates that the structure of parasite communities of charr and the trout is highly dependent on shifts in habitat and diet of their hosts both on an annual base and through the ontogeny, in addition to the observed niche segregation between the two salmonid species.     

Demersal fish parasite fauna around the South Shetland Islands: high species richness and low host specificity in deep Antarctic waters

A total of nine Antarctic fish species belonging to five families were examined for their endohelminth parasite fauna. The fishes Parachaenichthys charcoti (Bathydraconidae), Chaenocephalus aceratus (Channichtyidae), Paradiplospinus gracilis (Gempylidae), Muraenolepis microps (Muraenolepididae), Gobionotothen gibberifrons, Lepidonotothen larseni, L. nudifrons, L. squamifrons, and Trematomus eulepidopus (Nototheniidae) were caught between 80 and 608 m trawling depth off the Antarctic Peninsula (Elephant Island, King George Island) in 1996. Nineteen different parasites species comprising five Digenea, two Cestoda, four Nematoda, and eight Acanthocephala were found. Pseudophyllidean cestodes, the nematodes Contracaecum radiatum and C. osculatum as well as the acanthocephalan Corynosoma bullosum were the most common, infesting eight of the fish species studied with prevalences reaching 100%. Pseudoterranova decipiens s.l. was the only parasite that was isolated from all studied fish species; however, at a lower intensity. The observed parasite host specificity was low, and the species richness in a single fish ranged from one to eleven in a C. aceratus. This icefish and the moray cod M. microps were the most heavily infested fish, harbouring many adult and larval parasitic stages. The benthodemersal P. gracilis had only two larval parasite species, while the nototheniids had very similar parasite communities, harbouring a total of 8–14 species. Larval mammalian parasites were found to utilize fish, especially the nototheniids and channichthyids, as a common transmission route into their final hosts. The fish parasites parallel explored different benthic host systems to reach the most suitable host. In contrast to the coast and continental shelf, the meso/bathypelagiac zone appears to be species poor and is inhabited by few larval forms. The fish parasite fauna off the South Shetland Islands can be characterized by generalistic parasites that distribute within Antarctic waters according to the feeding ecology and depth range of their teleost hosts, not only horizontally but also extending vertically into the deep sea.     

Drivers of parasite community structure in fishes of the continental shelf of the Western Mediterranean: the importance of host phylogeny and autecological traits

We explored the relationships between features of host species and their environment, and the diversity, composition and structure of parasite faunas and communities using a large taxonomically consistent dataset of host-parasite associations and host-prey associations, and original environmental and host trait data (diet, trophic level, population density and habitat depth vagility) for the most abundant demersal fish species off the Catalonian coast of the Western Mediterranean. Altogether 98 species/taxa belonging to seven major parasite groups were recovered in 683 fish belonging to 10 species from seven families and four orders. Our analyses revealed that (i) the parasite fauna of the region is rich and dominated by digeneans; (ii) the host parasite faunas and communities exhibited wide variations in richness, abundance and similarity due to a strong phylogenetic component; (iii) the levels of host sharing were low and involved host generalists and larval parasites; (iv) the multivariate similarity pattern of prey samples showed significant associations with hosts and host trophic guilds; (v) prey compositional similarity was not associated with the similarity of trophically transmitted parasite assemblages; and (vi) phylogeny and fish autecological traits were the best predictors of parasite community metrics in the host-parasite system studied.     

Application of an index of biological integrity (IBI) to fish assemblages of the rivers Khan and Kshipra (Madhya Pradesh), India

1. A multimetric index of fish assemblage integrity was developed and similarity analyses were conducted on fish species in two central Indian rivers and the effects of distance from municipal and industrial effluents on those indices then evaluated.
2. Five metrics from Karr et al . (1986 , Illinois Natural History Survey Special Publication 5 , Urbana, IL) were adopted: intolerant species richness, % omnivorous individuals, % top carnivore individuals, total number of individuals and % individuals with anomalies. Seven new metrics (native species richness, native family richness, benthic species richness, water column species richness, % non-native individuals, % tolerant individuals and % herbivorous individuals) were added.
3. Non-native individuals represented 1–55% of the assemblages at sampled sites which held fish.
4. Fish were present at eleven sites and not collected at two sites, despite heavy metal concentrations exceeding U.S. Environmental Protection Agency acute criteria at all sites.
5. Two types of metric scoring were examined. The traditional 5–3–1 method showed the same pattern as continuous scoring from 0 to 10, but produced a higher integrity class at one site.
6. Scores on our modified index of fish assemblage integrity increased with distance downstream from a major effluent source in each river. Jaccard similarity scores between the least disturbed downstream site and all other sites decreased with increasing distance and disturbance.
7. It was concluded that Karr's original index and its theoretical foundations are easily adaptable, even to an ichthyofauna containing no species, and only two families (Cyprinidae, Poeciliidae), in common with the midwestern United States.     

Fish trophic level and the similarity of non-specific larval parasite assemblages

Whereas the effect of parasites on food webs is increasingly recognised and has been extensively measured and modelled, the effect of food webs on the structure of parasite assemblages has not been quantified in a similar way. Here, we apply the concept of decay in community similarity with increasing distance, previously used for parasites in geographical, phylogenetic and ontogenetic contexts, to differences in the trophic level (TL) based on diet composition of fishes. It is proposed as an accurate quantitative method to measure rates of assemblage change as a function of host feeding habits and is applied, to our knowledge for the first time, across host species in marine waters. We focused on a suite of 15 species of trophically-transmitted and non-specific larval helminths across 16 fish species (1783 specimens, six orders, 14 families) with different sizes and TLs, gathered from the same ecosystem. Not all host species harboured the same number and types of parasites, reflecting the differences in their ecological characteristics. Using differences in TL and body length as measurements of size and trophic distances, we found that similarity at both infracommunity and component community levels showed a very clear decay pattern, based on parasite abundance and relative abundance, with increasing distance in TL, but was not related to changes in fish size, with TL thus emerging as the main explanatory factor for similarity of parasite assemblages. Furthermore, the relationships between host TL and assemblage similarity allowed identification of fishes for which the TL was under- or over-estimated and prediction of the TL of host species based on parasite data alone.     

Comparison of the parasitic fauna of Aplocheilus panchax and A. melastigma

The metazoan parasite fauna of two species of freshwater fishes Aplocheilus panchax and A. melastigma collected from a stream at Waltair is compared; 17 parasite species were found. Aplocheilus panchax served as a host to 13 parasite species and A. melastigma to 10 parasite species. Of the 17 parasites collected, 12 were larval helminths to which the fishes act as intermediate and paratenic hosts. This has been attributed to the interaction between terrestrial birds, mammals and fishes in determining the parasite fauna in the biocoenosis. The parasite fauna of these fishes is divided into typical and less typical according to their frequencies. Among less typical there are peripheral division parasites which are abundant in other fishes in the stream. Only six parasite species occurred in both A. panchax and A. melastigma and both fish shared most of their parasite fauna with other fishes. Differences in the parasite fauna of these fishes are attributed to the morphological, behavioural or ecological features of these fishes.