Variations in the parasite fauna of the Patagonian toothfish (Dissostichus eleginoides Smitt, 1898), with length, season, and depth of habitat around the Falkland Islands

The parasite fauna of Dissostichus eleginoides was examined from locations around the Falkland Islands. In total, of 11,362 individual parasites of 27 taxa were recovered from 105 fish. Two species, Ceratomyxa dissostichi and Sphaerospora dissostichi, represent new host records. The nematode Ascarophis nototheniae and the larval acanothocephalan Corynosoma bullosum were found to be new locality records and add to the knowledge of the biogeography and host specificity of parasites on the Patagonian Shelf. There were no significant differences in the mean abundance and prevalence of parasites recovered between sexes. Therefore, sex was not considered in further analysis and the data were pooled. Cysts of unknown etiology (CUE), the monogenean Neopavlovskioides georgianus, the larval acanthocephalan Corynosoma bullosum, and the digenean Neolepidapedon magnatestis had significant positive correlations with increasing host length. The larval Trypanorhynch cestode Grillotia erinaceus and the digenean Elytrophalloides oatesi showed significant negative correlations with increasing host length. CUEs, N. georgianus, the digenean Gonocerca physidis and E. oatesi showed statistically significant prevalence between summer, winter, and spring. The effect of depth on parasite communities was also examined, initially using a linear discriminant function analysis. The prevalence of individual parasites was then compared between depth strata using the chi-square test. The parasite communities on the shelf and deep water (> 1,000 m) were found to be different, whereas those caught at intermediate depths on the shelf slope were found to have parasite communities that were intermediate, containing a mixture of shelf and deeper-water parasites. The causes of the variations in parasite faunas in association with these intrinsic and extrinsic factors are discussed.     

Level,content, and caloric equivalents of the lipid,carbohydrate, and protein in the body components of Luidia clathrata (echinodermata: asteroidea: platyasterida) in Tampa bay

The body components of the primitive platyasterid starfish, Luidia clathrata (Say) have been characterized according to season, reproductive, and nutritional condition. The animal has been ‘reconstructed’ in terms of the wet and dry weights, the weight of organic matter, and the caloric equivalents of the body components in early summer (when there are no gonads and the pyloric caeca are small), in autumn (just prior to initiation of gonadal development and at maximal caeca size), and in early spring (at maximal gonad size). The body wall is always the most significant component in terms of wet and dry weights. In terms of organic matter and calories, the pyloric caeca are the most significant compartment in the fall and, together with the gonads, in the spring. On starvation for one month, the decrease in the size of the pyloric caeca is calculated to have produced 2.048 kcal. The energy requirement over the period, calculated from Q_o2 values, is 2.112 kcal. There was no change in biochemical composition of the pyloric caeca with starvation, suggesting that energy production came about through cell destruction rather than preferential utilization of cellular nutrient stores. Lack of extreme change in the composition of the pyloric caeca with size through the year also suggests that energy deposition in the organ is primarily by change in cell number and not by cell size.     

Population dynamics of Gyrodactylus sp. (Monogenea) infecting the sand goby in the Oslo Fjord, Norway

Prevalence and abundance of Gyrodactylus sp. on the 1993 year-class of sand gobies Pomatoschistus minutus in the Oslo Fjord, Norway, decreased slightly during the cold months, increased as temperature increased in spring, reaching a peak in June, then decreased significantly, corresponding with a decline in the number of hosts from August. Abundance and, especially, prevalence increased again in September, and decreased in late autumn. Death of the most heavily infected hosts, and/or host resistance might be responsible for the decline in parasite numbers on post-spawners in summer. The young of the year (1994 year-class) were probably infected shortly after they commenced benthic life in July, and prevalence and abundance increased significantly throughout late summer and autumn. Parasite abundance on males was significantly higher than on females at the height of the breeding season in June, but significantly lower at the end of the breeding season in July. Two-thirds of the parasites infected the gills, oral cavity and pharynx. The proportion of parasites on the body, head and fins increased on both sexes, but significantly more so on males, during the breeding season of the host, when parasite intensity was highest. Possible routes of transmission of the parasite are discussed.     

Seasonal population dynamics of Paraquimpevia tenevvima (Linstow) (Nematoda) in the European eel Anguilla anguilla (Linnaeus) in three localities of southwest England

Seasonal population dynamics of Puraquzmperia tenerrima (Linstow) in the European eel Anguillu anguillu (Linnaeus) have been investigated in three localities in Devon, southwest England. The nematode is common and exhibits very similar seasonal patterns in changes of prevalence and abundance in the three localities. The population increases over winter through to late spring or early summer as the recruitment of the new generation occurs throughout this period. Reproduction of the nematode starts in spring. A sharp decrease of prevalence and abundance accompanies or follows reproduction, and infection levels are very low in autumn and early winter. The dispersion pattern of the nematode varies with the infection levels from over-dispersion in spring and early summer to almost random dispersion in autumn and winter. It is suggested that P. tenerrimu is a common specific parasite of eels, especially in small streams or rivers and that insect larvae or species of crustaceans might serve as intermediate hosts for the nematode.     

Search for seasonality in occurrence of parasites of cod,Gadus morhua L. in a fjord at 70°N

Samples of cod from the subarctic fjord, Balsfjord, in Norway, were collected in spring, summer and autumn from spring 1986 to spring 1987. The macroparasite fauna was investigated for seasonality in prevalence, mean intensity and abundance. Anisakis simplex had maximum mean intensity and abundance in the autumn. Echinorhynchus gadi had minimum prevalence, mean intensity and abundance in the autumn, but this was not statistically significant. None of the remaining 11 species of parasites demonstrated seasonality according to our definition.     

Seasonal dynamics of a flea number (Siphonaptera) on the common shrew (Sorex araneus) in the north part of the Novgorod oblast

In the course of 5-year stationary investigations of the common shrew Sorex araneus in the north part of the Novgorod oblast, 12 flea species have been recorded on this host. Among them, Palaeopsylla soricis and Doratopsilla dasycnema are specific parasites of small insectivores, including the common shrew. Hystrichopsylla talpae is a polyxenous species, parasitizing both rodents and insectivores. Other 9 flea species are not common parasites of S. araneus and apparently have come to this host from other mammal species inhabiting the forest biotopes in the area of investigation. P. soricis and D. dasycnema have similar phenology of parasitism. These fleas appear in spring (April), are present during summer and autumn and disappear in winter. During a year, the abundance of these species shows three pikes, which correspond to three generations: spring (April), summer (June-July) and autumn (September-October) generation. The first species dominates in spring (April-May) and in the autumn-winter period, while the second species predominates in summer. These two species comprise over 90% of total number of fleas collected and determine general dynamics of the flea number on the shrews; during the year the flea number has a sinusoidal increasing from spring to autumn and minimum in winter.     

The occurrence of Sphaerostoma bramae (Digenea: Allocreadiidae) in the roach from the Worcester-Birmingham canal

Two hundred roach (Rutilus rutilus) were examined over a twelve-month period to provide information concerning the occurrence of Sphaerostoma bramae. Infection levels were high during the autumn and winter and at this time of year the parasite population was composed almost exclusively of immature parasites. Maturation was rapid in the spring but was accompanied by a decrease in the infection level. In late summer, after egg-laying, losses due to the death of spent parasites began to be replaced by the recruitment of immature parasites and this recruitment reached its peak in the autumn and winter. The annual cycle of occurrence and maturation is discussed in relation to fluctuating environmental variables and the feeding behavior of the roach.     

The occurrence of metacercariae of Bucephaloides gracilescens (Digenea: Gasterostomata) in an intermediate host, the four-bearded rockling, Enchelyopus cimbrius (Gadidae)

Infections with metacercariae of Bucephaloides gracilescens in the four-bearded rockling Enchelyopus cimbrius were studied for a year in a Norwegian fjord. The prevalence was at all times high, but abundance showed a marked decline in spring to a low level during summer. A rise in abundance, variance-to-mean ratio and frequency of smaller metacercariae in early autumn (August-September) shows infection to have occurred mainly in autumn. There were no differences in level of infection between host sexes, but a highly significant positive correlation of parasite burden with host length. No influence on the condition factor of the host was revealed, the parasite cysts in the central nervous system are believed to have low pathogenicity. A detailed account of the distribution of metacercarial cysts is given. No support for infection being via the lateral line canals is revealed, cercarial penetration is believed to be through the general surface of the head and through the unpaired fins of the trunk and tail.     

Seasonal occurrence of helminths in the anadromous fish Coilia nasus (Engraulidae): parasite indicators of fish migratory movements

To understand the seasonal migration of the anadromous Coilia nasus , we attempted to identify the parasites infecting C. nasus and determine their seasonal occurrence. From June 2007 to July 2008, a survey of 775 C. nasus individuals from the estuary of the Yangtze River and the coast of the East China Sea revealed more than 7,300 parasites associated with the gills and alimentary tracts of C. nasus . The following 6 helminth taxa were identified, i.e., the monogeneans Heteromazocraes lingmueni and Helciferus tenuis, the digenean Elytrophallus coiliae, the acanthocephalan Acanthosentis cheni , and larvae of the nematodes Anisakis simplex and Contracaecum sp., all of which are marine or brackish-water parasites. The absence of freshwater helminths suggested that the parasites acquired in freshwater may have been accidentally, and easily, lost by the time the fish had reached the estuary and coast. Contrary to seasonal occurrence of the parasites' life cycles, the lowest mean abundance and prevalence of H. lingmueni and A. cheni occurred in August, which suggested the immigration of C. nasus from freshwater to the Yangtze estuary, with lower parasite burdens. The highest mean abundance and prevalence of the nematodes A. simplex and Contracaecum sp. in May and June, and the lowest in August, indicated the arrival of the fish from the coast and the Yangtze River, to the estuary, respectively. These findings suggested that a majority of the fish prepared for spawning migration in the estuary in spring and early summer and returned to the estuary after spawning in the lower and middle reaches of the Yangtze River in late summer.     

Parasite communities of common dolphins (Delphinus delphis) from Patagonia: the relation with host distribution and diet and comparison with sympatric hosts

We studied the helminths of 18 common dolphins, Delphinus delphis, from northern Patagonia. Parasites were found only in the gastrointestinal tract. Four species were in the stomach, the nematode Anisakis simplex, the acanthocephalan Corynosoma cetaceum, and the digeneans Braunina cordiformis and Pholeter gastrophilus, plus 1 digenean in the hepatopancreatic ducts, Oschmarinella rochebruni. Infection levels were low (0-155 parasites). Braunina cordiformis and C. cetaceum were the most prevalent species. Anisakis simplex was mainly concentrated in the forestomach, B. cordiformis in the main stomach, and C. cetaceum in the pyloric stomach. Component diversity was low and component evenness was intermediate. Infracommunity diversity was also low, and the mean evenness was higher than at the component community level. Low prevalence in common dolphins is consistent with parasite assemblages of other cetaceans off Patagonia. None of the parasites found is specific to this host species within the study area. We suggest that potential prey are probably important in parasite transmission in this and other dolphins from the Patagonian region.     

The occurrence and life history of Asymphylodora kubanicum (Platyhelminthes: Digenea: Monorchidae) in the Worcester-Birmingham canal, with special reference to the feeding habits of the definitive host, Rutilus rutilus

Two hundred roach and over 400 molluscs were examined over a one year period to investigate the occurrence and life history of Asymphylodora kubanicum in the Worcester-Birmingham canal. Larval stages, infective to the fish definitive host, were present in molluscs throughout the year but did not show a seasonal fluctuation in numbers. Parasites in the intestine of the roach showed a marked annual cycle of occurrence and maturation: low winter infection levels preceded a dramatic increase in infection during the spring and summer. Maturation of the parasite population was rapid during the spring and summer and in late summer and early autumn the parasites laid their eggs and subsequently died. The death of parasites after egg-laying resulted in the low winter infection level during which time little recruitment occurred.
Roach became infected mainly in their third year when molluscs become a dominant component of their diet. Thereafter the older fishes (<2+) are all equally susceptible to infection, but the larger (older) fishes become more heavily infected because of the greater consumption of molluscs per fish. The sex of the fish made no difference to infection with the parasite.     

洄游型、淡水型和陆封型刀鲚的寄生蠕虫群落结构

由于对淡水环境的适应和江湖阻隔,部分洄游型刀鲚(Coilia nasus)分化成淡水型和陆封型,为寻找区分洄游型、淡水型和陆封型这3种生态型刀鲚的寄生虫标志,并分析其寄生蠕虫群落结构特征,本文调查了3种生态型刀鲚鳃部、胃、肠和幽门盲囊中寄生蠕虫的种类和感染情况。共发现10种寄生虫,包括鳃上3种单殖吸虫:林氏异钩铗虫(Heteromazocraes lingmueni)、细长嗜鳀虫(Helciferus tenuis)和长江中华钩铗虫(Sinomazocraes changjiangensis);胃部1种复殖吸虫:鲚套茎吸虫(Elytrophallus coiliae);肠道3种线虫:简单异尖线虫(Anisakis simplex)、对盲囊线虫(Contracaecum sp.)和胃瘤线虫(Eustrongylides sp.),以及肠和幽门盲囊的3种棘头虫:陈氏刺棘虫(Acanthosentis cheni)、鲇异吻钩棘头虫(Arhythmacanthus parasiluri)、长江傲刺棘头虫(Brentisentis yangtzensis)。林氏异钩铗虫和陈氏刺棘虫在3种生态型的刀鲚中都有较高的感染率和平均丰度;海水性寄生虫细长嗜鳀虫、鲚套茎吸虫和对盲囊线虫只感染洄游型刀鲚,可作为区分洄游型刀鲚的寄生虫标志;淡水性寄生虫长江中华钩铗虫、鲇异吻钩棘头虫和长江傲刺棘头虫只在淡水型刀鲚中发现,可作为淡水型刀鲚的寄生虫标志。洄游型刀鲚的物种丰富度和Brillouin多样性最高,分别在1.25和0.19以上,淡水型刀鲚的较低,分别为0.79~1.12和0.10~0.12,陆封型刀鲚的最低,分别在0.66和0.02以下,这主要是由于淡水型和陆封型刀鲚中海水性寄生虫大部分丢失,以及淡水性寄生虫感染率和平均丰度都较低造成的。盐度降低和中间宿主缺乏是导致淡水型和陆封型刀鲚中海水性寄生虫丢失的主要原因;而淡水性寄生虫较低的感染水平可能是由于其对新宿主的适应时间较短;地理隔离可能是陆封型刀鲚中寄生虫群落多样性最低的另一重要原因。     

Population biology of parasites of striped mullet, Mugil cephalus L. I. Monogenea

Young-of-the-year (class 0) and yearling (class 1) striped mullet, Mugil cephalus , were collected from Sapelo Island, Georgia from May 1970 to June 1971 to study the development, seasonal abundance and relationship of environmental variables to parasitic populations. The number of species of parasites increased with age of the host. Initial infection appeared to be influenced by closeness of association of mullet age classes, by the period of abundance of a parasite on class I mullet and by the mobility of the infective parasitic stage. Fluctuations in intensity and prevalence of a parasite on class 0 mullet were similar to those of class I mullet after the initial infection. Ancyrocephalus vanbenedenii was first observed on class 0 mullet in March. Intensity was high on both classes in spring and on reproductively active mullet in late autumn. Prevalence on both classes was above 80% except in late summer. Polyclithrum mugilis was not observed on class 0 mullet until August even though intensity and prevalence on class I mullet was highest during early spring. Gyrodactylus mugelus did not occur on class 0 mullet but appeared on class I mullet during late summer. Microcotyle psuedomugilis was observed on class 0 mullet in early summer and Metamicrocolyla maeracantha in October. Both species occurred but at a low intensity on class I mullet.     

Circannual variation in blood parasitism in a sub‐Saharan migrant passerine bird,the garden warbler

Knowing the natural dynamics of pathogens in migratory birds is important, for example, to understand the factors that influence the transport of pathogens to and their transmission in new geographical areas, whereas the transmission of other pathogens might be restricted to a specific area. We studied haemosporidian blood parasites of the genera Plasmodium, Haemoproteus and Leucocytozoon in a migratory bird, the garden warbler Sylvia borin. Birds were sampled in spring, summer and early autumn at breeding grounds in Sweden, on migration at Capri, Italy and on arrival and departure from wintering staging areas in West Africa: mapping recoveries of garden warblers ringed in Fennoscandia and Capri showed that these sites are most probably on the migratory flyway of garden warblers breeding at Kvismaren. Overall, haemosporidian prevalence was 39%, involving 24 different parasite lineages. Prevalence varied significantly over the migratory cycle, with relatively high prevalence of blood parasites in the population on breeding grounds and at the onset of autumn migration, followed by marked declines in prevalence during migration both on spring and autumn passage. Importantly, we found that when examining circannual variation in the different lineages, significantly different prevalence profiles emerged both between and within genera. Our results suggest that differences in prevalence profiles are the result of either different parasite transmission strategies or coevolution between the host and the various parasite lineages. When separating parasites into common vs. rare lineages, we found that two peaks in the prevalence of rare parasites occur; on arrival at Swedish breeding grounds, and after the wintering period in Africa. Our results stress the importance of appropriate taxonomic resolution when examining host‐parasite interactions, as variation in prevalence both between and within parasite genera can show markedly different patterns.     

Redescription and life cycle of the monorchiid Postmonorcheides maclovini Szidat, 1950 (Digenea) from the Southwestern Atlantic Ocean: Morphological and molecular data

The adult monorchiid, Postmonorcheides maclovini Szidat, 1950, digenean parasite of the Patagonian blennie Eleginops maclovinus (Cuvier) (Eleginopidae) from Puerto Deseado (47° 45′ S, 65° 55′ W), Argentina, was characterized and its life cycle elucidated. P. maclovinus is the only species of the genus Postmonorcheides, proposed by Szidat (1950) from Tierra del Fuego province (~ 54° S), Argentina. This digenean uses the Patagonian blennie as definitive host, and the intertidal bivalve Lasaea adansoni (Gmelin) (Lasaeidae) as both first and second intermediate hosts (metacercariae encyst inside sporocysts), being the first record of this clam as intermediate host of trematode parasites. The cercaria may, in addition to encysting in the sporocyst, emerge and presumably infect other intermediate hosts. This is the second report of a monorchiid species with metacercariae encysting inside the sporocyst. Adults were found parasitizing the fish stomach, pyloric caeca and intestine with a prevalence of 100%; sporocysts with cercariae and/or metacercariae were found parasitizing the gonad of the bivalve with a prevalence of 2.78%. The cercariae possess a well-developed tail and eye-spots are absent. The ITS1 sequence from the adult digeneans found in the Patagonian blennie, identified as P. maclovini, was found to be identical to the ITS1 sequences obtained both from sporocysts containing cercariae and encysted metacercariae found in L. adansoni.     

Dynamics and predicted decline of Anguillicola crassus infection in European eels, Anguilla anguilla, in Neusiedler See, Austria

The eel population in Neusiedler See has been maintained by regular massive stocking since 1958. After the establishment of the National Park Neusiedler See-Seewinkel in 1993, eel stocking was prohibited and the population, together with the specific parasites of eels, was predicted to decline to extinction within 10 years. This investigation was undertaken to document the decline and extinction of the Anguillicola crassus population in eels. From 1994 to 2001, 720 eels were collected from two sites in the lake. Prevalence and abundance of A. crassus were lower in spring than in summer and autumn and larger eels harboured more parasites than smaller ones. Neither year of study nor sampling site were correlated with parasite infection levels. No significant trend in the population parameters of A. crassus was detected over the 8 years of the survey. This suggested that there had been no significant decline in the eel population. This suggestion was confirmed by investigations of the fishery, which also found evidence of regular illegal stocking. The stability of the A. crassus population over the past decade seems to reflect the lack of change in eel population density. No mass mortalities of eels occurred over the period despite the many similarities between Neusiedler See and Lake Balaton in Hungary. Differences in eel size, eel diet and the lack of large-scale insecticide use are discussed as possible explanations for the absence of eel mass mortalities in Neusiedler See.     

宁夏枸杞根际土壤线虫群落特征

宁夏枸杞具有很高的药用价值和营养价值,在宁夏大面积种植,带来了巨大的经济效益.研究不同条件下宁夏枸杞根际土壤线虫群落特征,对防止枸杞园土壤退化具有重要意义.以宁夏枸杞之乡——中宁为研究区,系统分析了季节、树龄和土层对枸杞根际土壤线虫数量和生态指数的影响.结果表明: 夏季宁夏枸杞根际土壤线虫数量最多,小杆属和拟丽突属为优势属;春季线虫数量最少,小杆属、针属和盘旋属为优势属;从春季到秋季,线虫稀有属种类和个体密度逐渐减少.随着树龄的增加,夏季根际土壤线虫总数逐渐减少;春季和秋季枸杞根际线虫总数先增加后减少,其中9年树龄根际土壤线虫总数最多.各树龄根际均为食细菌线虫所占比例最大,食真菌线虫和捕食-杂食类线虫比例很小,树龄<3年和>9年时植物寄生线虫比例相对较大.夏季枸杞根际20～40 cm比0～20 cm土壤线虫数量增加49.4%.随着树龄的增加,枸杞根际土壤线虫多样性指数、均匀度指数和丰富度指数均呈减小-增大-减小的趋势,而优势度指数先减小后增大.土壤pH值与土壤线虫优势度指数呈显著正相关;土壤有机质和速效磷与植物寄生线虫分别呈显著正相关和负相关;土壤碱解氮与线虫总数呈显著正相关;速效钾与线虫多个生态指数均呈显著负相关.整体上,随着树龄的增加,春季和秋季土壤线虫数量先增加后减少,夏季土壤线虫数量呈逐渐减少的趋势;线虫多样性下降,土壤逐渐退化.此外,在幼林和树龄>9年后需要抑制土壤植物寄生线虫的繁殖,以减少后期因线虫引起的病害.     

Infracommunity structure of parasites of Hemigymnus melapterus (Pisces: Labridae) from Lizard Island, Australia: the importance of habitat and parasite body size

This study describes the community of all metazoan parasites from 14 individuals of thicklip wrasse, Hemigymnus melapterus, from Lizard Island, Australia. All fish were parasitized, and 4,649 parasite individuals were found. Twenty-six parasite species were identified although only 6 species were abundant and prevalent: gnathiid isopods, the copepod Hatschekia hemigymni, the digenean Callohelmis pichelinae, and 3 morphotypes of tetraphyllidean cestode larvae. We analyzed whether the body size and microhabitat of the parasites and size of the host affected understanding of the structure of the parasite community. We related the abundance, biovolume, and density of parasites with the host body size and analyzed the abundances and volumetric densities of some parasite species within microhabitats. Although the 2 most abundant species comprised 75% of all parasite individuals, 4 species, each in similar proportion, comprised 85% of the total biovolume. Although larger host individuals had higher richness, abundance, and biovolume of parasites than smaller individuals, overall parasite volumetric density actually decreased with the host body size. Moreover, parasites exhibited abundances and densities significantly different among microhabitats; some parasite species depended on the area available, whereas others selected a specific microhabitat. Parasite and habitat size exhibited interesting relationships that should be considered more frequently. Considerations of these parameters improve understanding of parasite community structure and how the parasites use their habitats.     

Seasonal dynamics and distribution of the digenean Phyllodistomum pawlovskii (Trematoda: Gorgoderidae) in the bullhead catfish, Pseudobagrus fulvidraco, in a lake of China

Seasonal population dynamics of the digenean Phyllodistomum pawlovskii in the urinary bladder of the bullhead catfish, Pseudobagrus fulvidraco, were investigated in Liangzi Lake in the flood plain of the Yangtze River in China from February 2001 to July 2002. The overall prevalence of the parasite was high, 41.5% (n = 1,476), while the mean abundance was relatively low, 1.24 +/- 2.11. The parasite exhibited evident seasonality in changes of prevalence and abundance. In brief, prevalence and abundance were very low in midwinter (January), but increased and remained relatively high in other seasons and months. The distribution pattern of this parasite in the fish was overdispersed, with a variance to mean ratio > 1, but its frequency distribution could not be described by the negative binomial model. There were positive correlations between the number of the parasites per fish and the age and length of the fish; a peaked age-parasite abundance curve was not detected in the parasite-host association. It is suggested that the parasite P. pawlovskii has little effect on the population structure of the bullhead catfish.