Classification and occurrence of abnormally developed Paradiplozoon homoion (Monogenea, Diplozoinae) parasitising gudgeon Gobio gobio

Morphological analyses of the attachment apparatus (clamps and central hooks) of Paradiplozoon homoion (Bychowsky & Nagibina, 1959) (Diplozoinae, Monogenea) parasitising gills of Gobio gobio (L.) showed a high percentage of abnormally developed parasite specimens. Four different localities in the Vlára River basin, Czech Republic, were investigated for the presence of such abnormal individuals. The highest percentage of abnormalities in the attachment apparatus (over 39%) was recorded in the Vlára River, at Bohuslavice. This study provides a comprehensive classification of these abnormalities with 7 types of abnormalities described and illustrated. Abnormalities of parts of the attachment apparatus that form in the later stage of ontogenetic development were the most frequent, the most frequent types of abnormalities being clamps with abnormal sclerites, and combinations of abnormalities. Abnormalities of the central hooks were also found in our material. The abnormalities found in diplozoids are probably connected with environmental pollution; however, this point requires further investigation.     

Molecular characterization of Diplozoidae populations on 5 species of Cyprinidae: new data on parasite specificity

The genus Diplozoon (Platyhelminth) exhibits one of the most striking modes of reproduction. Adults reproduce after the permanent fusion of two larval hermaphrodites, which play a symmetrical role. The Diplozoidae are also exceptional among the Monogenea Polyopisthocotylea for two other reasons. They represent the only group really diversified on continental freshwater fishes; however, this diversification is difficult to evaluate since few morphoanatomical criteria are available to distinguish species and their host specificity is atypically variable among the Monogenea. For the first time in the Diplozoidae, the problems of species definition and of host specificity are examined using molecular tools. Two ribosomal markers (ITS2 and 28S rDNA (D1)) have been sequenced in five Diplozoidae, interacting with five Cyprinidae host species: the corresponding parasite-host systems have been well characterised, revealing some contrasting situations in the relations between Diplozoidae and Cyprinidae. Some species are effectively strictly host specific, but Diplozoon scardinii initially considered as a specific species on Scardinius erythrophtalmus and D. homoion on Rutilus rutilus are proposed to be a single species on the basis of their identical ITS2 and 28S rDNA sequences. On the same basis we proposed that D. paradoxum is able to parasitize two fish species, Abramis brama and Blicca bjoerkna, despite the morphological differences observed between the two xenopopulations. Phylogenetic relationships among Diplozoidae species were estimated with ITS2 sequences while cytochrome b sequences were used for their fish hosts. Finally, the comparison between these two molecular phylogenies seems to exhibit the phenomenon of cospeciation.     

The relationship between developmental instability of gudgeon Gobio gobio and abundance or morphology of its ectoparasite Paradiplozoon homoion (Monogenea)

Gudgeon Gobio gobio (Cyprinidae) were collected monthly from the Vlara Stream (Czech Republic) during 2004 and examined for the presence of the ectoparasite Paradiplozoon homoion (Diplozoidae; Monogenea). Over 26% of P. homoion showed abnormalities of the attachment sclerites, indicating either a stressful environment or that the quality of the fish host was suboptimal for parasite development. Here, the hypotheses that parasite abundance and the occurrence of morphological abnormalities are correlated with fluctuating asymmetry (FA, the random deviation from the perfect bilateral symmetry) in its fish host were tested. The FA and morphological abnormality are estimators of developmental instability. To estimate fish developmental instability nine meristic and two morphometric bilateral characters on the right and the left sides of the fish were measured. In general, there was no correlation between mean fish FA and parasite abundance or the proportion of parasites with abnormalities. There was, however, a significant relationship between the proportion of abnormal P. homoion and the number of asymmetric meristic traits per individual fish. This study thus indicates that developmental instability of P. homoion , measured as morphological abnormality of the attachment apparatus, is only weakly dependent on the fish quality as measured by FA.     

The surface topography of <Emphasis Type="Italic">Eudiplozoon nipponicum</Emphasis> (Monogenea) developmental stages parasitizing carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.)

Using scanning electron microscopy (SEM), the external morphology of all developmental stages (egg, oncomiracidium, diporpa, just fused juvenile and adult) of the parasite, Eudiplozoon nipponicum (Monogenea, Diplozoidae), from the gills of carp was studied. During the ontogeny, the tegument, tegumentary and sensory structures are subsequently developed. The tegument of free swimming oncomiracidium occurs in two types — the ciliated and non-ciliated with numerous uniciliated sensory structures. An attachment apparatus starts to form during the oncomiracidium stage. Further developmental stages are adapted to the environment of the gills. Tegumentary folds become more apparent later in development and assist to the parasite’s attachment. In connection with its reproductive strategy, the two morphological structures of diporpa (ventral sucker and dorsal papilla) appear to play important role. On the gills, two individuals need to meet and these structures mediate the fusion between two diporpae. The hindbody of adult parasite is highly modified for attachment. The haptor, folds and lobular extensions are most developed. The forebody is flexible and able to interact with host gill tissue via the mouth and associated mouth structures. The process of food intake of the parasite was discussed.     

Seaweed extracts as a natural control against the monogenean ectoparasite,Neobenedenia sp., infecting farmed barramundi (Lates calcarifer)

Aqueous extracts from common tropical seaweeds were evaluated for their effect on the life cycle of the commercially important ectoparasite, Neobenedenia sp. (Platyhelminthes: Monogenea), through the survival of attached adult parasites, period of embryonic development, hatching success and oncomiracidia (larvae) infection success. There was no significant effect of any extract on the survival of adult parasites attached to fish hosts or infection success by oncomiracidia. However, the extracts of two seaweeds, Ulva sp. and Asparagopsis taxiformis, delayed embryonic development and inhibited egg hatching. The extract of A. taxiformis was most effective, inhibiting embryonic development of Neobenedenia sp. and reducing hatching success to 3% compared with 99% for the seawater control. Furthermore, of the 3% of eggs that hatched, time to first and last hatch was delayed (days 14 and 18) compared with the seawater control (days 5 and 7). Asparagopsis taxiformis shows the most potential for development as a natural treatment to manage monogenean infections in intensive aquaculture with the greatest impact at the embryo stage.     

Abnormalities of the attachment clamps of representatives of the family Diplozoidae

A comparative study has been made of the haptoral morphology of four species of diplozoon (Monogenea: Diplozoidae) from the gills of fish exposed to different levels of water pollution in two river systems in eastern Europe. An examination of the haptors of Paradiplozoon homoion (Bychowsky & Nagibina 1959), Paradiplozoon ergensi (Pejcoch 1968) and Paradiplozoon megan (Bychowsky & Nagibina 1959) from chub caught in the River Morava, Czech Republic and of Diplozoon paradoxum (Nordmann 1832) from bream recovered from the River Volga, Russia has revealed abnormalities to the attachment clamps. Two abnormal conditions were found: structural alterations to the attachment clamps and changes in the number of attachment clamps; these occurred both singly and in combination. A higher frequency of abnormal attachment clamps was found in diplozoons from fish caught in the more polluted localities of both rivers. The abnormalities have been recorded and their morphology compared in the light of conditions of environmental stress.     

Attachment-inducing capacities of fish tissue extracts on oncomiracidia of Neobenedenia girellae (Monogenea, Capsalidae)

When oncomiracidia of Neobenedenia girellae (Monogenea, Capsalidae) were incubated in wells with lyophilized extracts of fish skin epithelia on the bottom, some attached to the well bottom with the haptor unfolded and shed the ciliated epidermal cells. Based on these morphological changes in oncomiracidia, we developed a new assay method to examine the attachment-inducing capacities of various fish extracts for oncomiracidia. Attachment-inducing capacities were found only in extracts of fish skin epithelium and not in other fish extracts. No significant difference in capacities was observed among extracts of skin epithelia of 4 fish species. Wheat germ lectin and concanavalin A suppressed capacities in extracts of skin epithelia of Japanese flounder and yellowtail, respectively. Suppressed capacities were recovered by adding sugars that bound specifically to these lectins. These results indicate that some sugar-related chemical substances that exist specifically in fish epithelium induce the attachment of N. girellae oncomiracidia.     

Involvement of host recognition by oncomiracidia and post-larval survivability in the host specificity of Heterobothrium okamotoi (Monogenea: Diclidophoridae)

Heterobothrium okamotoi, a monogenean gill parasite, shows high host specificity for tiger puffer, Takifugu rubripes. In the present study, in vivo and in vitro experimental infections were conducted using various fish species, including T. rubripes, to understand the mechanisms of specificity. In in vivo experiments, T. rubripes, grass puffer, Takifugu niphobles, olive flounder, Paralichthys olivaceus, and red sea bream, Pagrus major, were exposed to oncomiracidia of H. okamotoi labelled with a fluorescent dye, 5- (and -6) carboxyfluorescein diacetate succinimidyl ester, and the numbers of parasites on the gills and skin were recorded at intervals. Oncomiracidia were attached to gills and skin of all the experimental fish species immediately after exposure, and the infection intensity on T. rubripes was higher than that on T. niphobles and much higher than those on the other two species. After 2 days, the attached parasites remained on the gills of T. rubripes, but disappeared from the other hosts. During in vitro experiments, gill filaments excised from seven different fish species (four fish species used in the in vivo experiments and panther puffer, Takifugu pardalis, southern flounder, Paralichthys lethostigma and spotted halibut, Verasper variegates) were exposed to oncomiracidia and the attachment to each fish species and subsequent larval behaviour was observed. The percentage of post-larvae that attached to T. rubripes was slightly higher than those which attached to congeneric fish species and much higher than those of non-tetraodontid fish species. In vivo and in vitro experiments demonstrated that oncomiracidia of H. okamotoi have an affinity for their natural host, T. rubripes, and congeneric fish species. The disappearance of attached post-larvae from 'alien' hosts within 2 days during in vivo experiments suggested that host recognition by oncomiracidia and subsequent post-larval survivability are involved in the host specificity of H. okamotoi.     

Effect of host quality of Callosobruchus maculatus (Coleoptera: Bruchidae) on performance of the egg parasitoid Uscana lariophaga (Hymenoptera: Trichogrammatidae)

Development and reproductive success of the solitary egg parasitoid Uscana lariophaga Steffan were examined after development in eggs of the bruchid storage pest Callosobruchus maculatus Fabricius reared at either low or high densities on cowpea seeds and laid at day 1 and 4 of maternal life. Both bruchid larval competition and maternal age negatively affected egg size, but the latter more than the former. Uscana lariophaga reared in small hosts developed slower, were smaller and produced fewer eggs compared to parasitoids reared in large hosts. Fecundity of the parasitoid was heavily influenced by host egg size. This was reflected in the values for the intrinsic rate of increase of U. lariophaga, which differed for wasps that developed in host eggs laid by bruchid females of different age. Wasps allocated marginally more female offspring to larger hosts.     

Effect of Temperature on the Biology of Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae) Reared on a Factitious Host,Antheraea pernyi (Lepidoptera: Saturniidae) Egg

Laboratory studies were conducted to investigate the effect of selected temperatures on the development, mortality, sex ratio, and emergence rate of Trichogramma dendrolimi Matsumura reared from a factitious host, oak silkworm, Antheraea pernyi (Guérin-Méneville) eggs. The comparison tests were conducted to investigate the fecundity on Dendrolimus spectabilis (Butler) eggs of T. dendrolimi reared from natural and factitious hosts, and artificial hosts. Developmental periods from egg to adult of T. dendrolimi reared at 26, 28, 30, and 32°C were 10.9, 9.6, 9.0, 8.6 days, respectively. Emergence rates of T. dendrolimi decreased 78.0, 88.4, 60.7, and 50.1% as temperature increased. The progeny sex ratios (i.e., females per male) were 7.3, 8.4, 8.2 and 6.9 at the respective temperatures. When adult T. dendrolimi emerged from A. pernyi eggs were kept in dark conditions for storage at different temperatures for 34 days, their mortality increased as temperature increased: 0% at 0°C; 10% at 4°C; 40% at 6°C; 50% at 18°C and 100% at ≥26°C. The fecundity of T. dendrolimi reared from three different hosts was investigated on D. spectabilis eggs. During the first day, the adult T. dendrolimi reared on A. pernyi eggs laid most eggs (99.0±10.7), followed by those reared on artificial hosts (76.6±24.5) and D. spectabilis eggs (63.4±35.9). Over the entire lifespan, T. dendrolimi reared on D. spectabilis eggs produced the highest number of eggs (218.0±27.9), followed by A. pernyi eggs (104.0±44.7) and artificial host (98.2±37.1). These results suggest that the temperature and three hosts factors had an effect on rearing of the T. dendrolimi on the factitious host, A. pernyi eggs.     

How to catch a parasite: Parasite Niche Modeler (PaNic) meets Fishbase

Parasite Niche Modeler (PaNic) is a free online software tool that suggests potential hosts for fish parasites. For a particular parasite species from the major helminth groups (Acanthocephala, Cestoda, Monogenea, Nematoda, Trematoda), PaNic takes data from known hosts (maximum body length, growth rate, life span, age at first maturity, trophic level, phylogeny, and biogeography) and hypothesizes similar fish species that might serve as hosts to that parasite. Users can give varying weights to host attributes and create custom models. In addition to suggesting plausible hosts (with varying degrees of confidence), the models indicate known host species that appear to be outliers in comparison to other known hosts. These unique features make PaNic an innovative tool for addressing both theoretical and applied questions in fish parasitology. PaNic can be accessed at < http://purl.oclc.org/fishpest >.     

Is the Octomacridae the sister family of the Diplozodae?

Diplozoidae and Octomacridae are usually considered as sister families. Essentially this is because they are the only polyopisthocotyleans parasitising primary freshwater teleosts. Because of the lack of phylogenetically informative morphological characters to explore the pattern of colonisation of the primary continental freshwater teleosts and in order to understand the appearance of the "natural parabiosis" of Diplozoidae, a molecular phylogeny was inferred by comparing newly obtained partial 28S and 18S rDNA gene sequences of Eudiplozoon nipponicum and Diplozoon homoion with other already available sequences. The phylogenetic analysis seems to show that Diplozoidae and Octomacridae are not sister groups. Thus, the colonisation of primary freshwater teleosts by these two families could be independent.     

Beyond Symbiosis: Cleaner Shrimp Clean Up in Culture

Cleaner organisms exhibit a remarkable natural behaviour where they consume ectoparasites attached to “client” organisms. While this behaviour can be utilized as a natural method of parasitic disease control (or biocontrol), it is not known whether cleaner organisms can also limit reinfection from parasite eggs and larvae within the environment. Here we show that cleaner shrimp, Lysmata amboinensis, consume eggs and larvae of a harmful monogenean parasite, Neobenedenia sp., in aquaculture. Shrimp consumed parasite eggs under diurnal (63%) and nocturnal (14%) conditions as well as infectious larvae (oncomiracidia) diurnally (26%). Furthermore, we trialled the inclusion of cleaner shrimp for preventative parasite management of ornamental fish, Pseudanthias squamipinnis, and found shrimp reduced oncomiracidia infection success of host fish by half compared to controls (held without shrimp). Fish held without cleaner shrimp exhibited pigmentation changes as a result of infection, possibly indicative of a stress response. These results provide the first empirical evidence that cleaner organisms reduce parasite loads in the environment through non-symbiotic cleaning activities. Our research findings have relevance to aquaculture and the marine ornamental trade, where cleaner shrimp could be applied for prophylaxis and control of ectoparasite infections.     

不同寄主植物对幻紫斑蝶产卵选择及种群适合度的影响

通过研究幻紫斑蝶(Euploea core Cramer)成虫对6种寄主植物和2种非寄主植物的产卵选择,以及用5种寄主植物饲养下幻紫斑蝶的发育、存活和繁殖情况,为幻紫斑蝶人工规模化养殖提供理论依据。幻紫斑蝶成虫优先选择聚果榕,其次选择古钩藤和马利筋进行产卵;用黄花夹竹桃饲养的幻紫斑蝶发育历期最长,用马利筋饲养的幻紫斑蝶发育历期最短;用古钩藤、爬森藤和马利筋饲养的幻紫斑蝶蛹的质量、体长和头宽均大于其它两种寄主植物;用古钩藤、爬森藤和聚果榕饲养的幻紫斑蝶存活率较高,而黄花夹竹桃最低;用古钩藤饲养的幻紫斑蝶成虫产卵量、交配频率和卵孵化率均最高,其次为爬森藤。因此,聚果榕、古钩藤和马利筋可作为幻紫斑蝶成虫产卵的优势寄主,古钩藤和爬森藤可作为饲养幻紫斑蝶的优势寄主。     

Polystoma gallieni: Experimental evidence for chemical cues for developmental plasticity

Among monogeneans that display direct life cycles, plastic developmental strategies may have been selected to counter the lack of transmission opportunities. Within amphibian polystomatids, some species of the genus Polystoma develop into two different phenotypes depending on the host physiological stage to which free swimming larvae attach. When oncomiracidia infest old tadpoles, they develop slowly and migrate during host metamorphosis towards the bladder where they reach maturity. On the other hand when larvae infest young tadpoles, they develop rapidly into neotenic phenotypes that reproduce in the branchial chamber. These alternative developments are explored through experimental infestations with Polystoma gallieni, the specific polystome of the stripeless tree frog Hyla meridionalis. When oncomiracidia were left for 6 h in water in which young tadpoles had been previously maintained for one day, they mainly developed into the neotenic phenotype regardless of the tadpole stage they encountered later. This indicates that P. gallieni could collect released host-derived signals before physical contact with its host.     

A laboratory study of the effects of cytoplasmic polyhedrosis virus on Heliothis virescens (Lepidoptera: Noctuidae)

Larvae of Heliothis virescens reared from eggs contaminated with cytoplasmic polyhedrosis virus weighed 50% less than those reared from virus-free eggs. The larval stage in a virus-infected group was 4 days longer than that of a healthy group, and diseased pupae weighed an average of 60 mg less than healthy pupae. Furthermore, adult emergence was reduced 10% in virus-infected pupae, diseased moths lived 9 days less than healthy moths, and production of eggs was reduced 68% in diseased females.     

Surface carbohydrates of Eudiplozoon nipponicum pre- and post-fusion

The development of the monogenean Diplozoon (Nordmann, 1832) (Diplozoidae) necessitates fusion of two larval stages (diporpae) into one double organism. How diporpae find, distinguish and contact each other is unclear, nor is the nature of the stimuli responsible for the dedifferentiation of cells and the formation of new tissues at the site of somatic fusion. Previous studies have implied a role for carbohydrates and glycoproteins in the interactions between helminth parasites and their hosts. Hypothetically, glycoconjugates may also be involved in the establishment of parasite-parasite associations. Changes in the surface saccharide residues during the development of Eudiplozoon nipponicum, a gill ectoparasite of carp (Cyprinus carpio) are described. Flat-fixed specimens and sections of diporpae, juveniles (just-fused) and adult worms were examined following exposure to a panel of 12 FITC-conjugated lectins. All developmental stages exhibited a specific surface binding pattern with ten lectins, indicating that Man/Glc, GlcNAc, Gal and GalNAc are probably present on their surfaces. No reaction was observed with Fuc-specific lectins (UEA-I and LTA). There is evidence that parasite development is accompanied by both qualitative and quantitative changes in the saccharide pattern distribution. The diporpa sucker reacted with nine lectins, excluding BS-II. A very strong binding of PNA, LCA and ConA (Gal and Man/Glc-specific lectins) was observed with the papilla glands of juvenile worms. The role of glandular secretions in this unique fusion process is discussed.     

利用柞蚕卵繁殖的松毛虫赤眼蜂的适宜冷贮虫期和温度

我国普遍利用柞蚕Antheraea pernyi卵大量繁殖和释放赤眼蜂防治多种农林害虫。对赤眼蜂进行冷贮有助于其商品化生产、运输和释放应用。为了全面评价冷贮对柞蚕卵繁殖赤眼蜂的影响,作者采用柞蚕卵为寄主,以贮存温度（4℃、7℃、10℃和13℃）、贮存虫期（卵、幼虫、预蛹和蛹期）和贮存时间（2周、4周、6周和8周）为参试因子,研究了冷贮对松毛虫赤眼蜂Trichogramma dendrolimi羽化出蜂率、单卵出蜂数、单卵雌蜂比的影响。结果表明,3个因素均可单独或互作显著影响羽化出蜂率和单卵出蜂数,尤以贮存虫期的影响更为明显;但3个因素对单卵出蜂性比影响不大。综合各冷贮虫期对低温的反应,松毛虫赤眼蜂对10℃反应最敏感,各虫期羽化出蜂率和单卵出蜂数明显降低,不适宜长期冷贮;对7℃反应相对较不敏感,最适宜长期贮存。在适宜长期冷贮温度（4℃和7℃）条件下,适宜贮存虫期有所不同,4℃下为幼虫期和蛹期,7℃下为卵期和蛹期,在这些虫期和贮存温度条件组合下羽化出峰率和单卵出蜂数相对于其他虫期受冷贮的不利影响较小。从对羽化出蜂率的影响来看,于卵期7℃下冷贮为最适宜;从对单卵出蜂数的影响来看,于蛹期在4℃和7℃冷贮为适宜。