Some peculiarities of the relationships between parasitic copepods and their invertebrate hosts

According to the rule of academican E. N. Pavlovskiy, any organism of host is an environment of inhabit for a parasite (Pavlovskiy, 1934). It was analysed, which "ecological niche" or microbiotop (= microhabitat) is occupied by this or that species of symbiotic (parasitic) copepods in organisms of different groups invertebrate-hosts. The assumption lying in a basis of the given analysis means that each group of hosts may give to cohabitants only certain variants of microbiotopes independently on the general morphological structure and life mode of hosts. Five types of microbiotops offered by various groups of hosts for symbiotic copepods are designated (Ta[symbol: see text] 2). 1. The body surface of benthic invertebrates as a microbiotope is characterized by conditions being little different (concerning any kind of physical and chemical influences on copepods) from those in external environment on any other substrate. Apparently a trophical dependence plays a determining role in this case. There are certain directions in a development of adaptations, which are characteristic in some extent for all water ectoparasitic crustaceans and have one functional task--to help to an ectoparasite to keep itself on a surface of host body. In the first, the maxillules and maxillipeds significantly are developed, they get a form of large claws, with which the dopepods are strongly attached on a surface of host body and have an opportunity to move on it without a danger to be washed off. In the second, the form of the body undergoes a dorso-ventral expression and expansion of prosome, forms a cephalic shield allowing to the symbiont to press itself tightly to the host body surface and to avoid the loss of host (tab. 2). In occasions, some ectoparasites stimulate the formation of galls in skin tissues of the host, that also provides the parasite with constant conditions, without any threat to lose the host. However, this phenomenon has not a wide distribution and is observed in some groups of crustacean and echinoderm hosts. 2. The narrow tubular cavities in the organism of host either they are a part of external environment (as in channel system of spongia) or a part of internal environment of organism (as channels of blood system or thin parts of a digestive system) have always rigidly limited sizes and form. Characteristics of all parasites occupying this microbiotopes are the strong transformations. They are expressed by the reduction of legs or any other appendages (frequently in a significant degree), loss of segmentation to some extent and in eruciform (or vermiform) form of a body (tab. 2). This microbiotope is occupied by an ectoparasite in one case only (Spongicola uncifer from channel system of spongia) and by endoparasites in all other cases. 3. Large cavities connected with external environment. The formations of various genesis, such as mantle cavity of molluscs, gill cavity and marsupium of crustaceans, bursal cavity of ophiuroids and branchial cavity of ascidians, concern this type of microbiotopes. All of them are characterized by the relative difference from the external environment and rather large volume (in comparison to sizes of copepods), that provides the parasites with a sufficient protection from factors of the external environment and constant source of food such as elements of host body or food's particles brought by the water flow. Morphological changes in inhabitants of the microbiotope have two directions. They practically are absent in the overwhelming majority copepods, living in the mantle of cavity of the lamellibranches. On the other hand, the inhabitants of gill cavity and marsupium of crustaceans, bursal cavities of ophiuroids and branchial cavity of ascidians are characterized by the presence of strong transformations. Usually there are expressed in a loss of segmentation to some extent, reduction of appendages and swelling of body, as in species of the genus Sphaeronella (tab. 2). Changes are also observed in the life cycle: the tendency to reduce stages of development (development of nauplii stage, which takes place under the ovarial cover). In this case the copepodid stages hatch from the ova. 4. The internal cavity of organism of host. This type of microbiotopes in different groups of the hosts is represented in a various degree. We recognise it in a coelome of polychaetes, lacunar system of molluscs, mixocoel of crustaceans, coelome of echinoderms and cavity of body in ascidians. Two basic evolutionary directions are observed in copepods occupying this microbiotope. In the first case, the parasite is not exposed to transformations and keeps the initial plan of structure as in ancestral free-living forms. In the second case the parasites are exposed to strong transformations, they either live directly in cavity's liquid, or are surrounded by a cyst (as in Cucumaricolidae). 5. Microbiotope of the last type is most specific. The simultaneous existence in two environments--external environment (environment of the second order) and internal environment (environment of the first order) leads to the complete loss of ancestral type in a structure and level of organisation. At the same time both morphological and functional division of the parasite body into two parts produces a new formation--the ectosome and endosome. In this case we deals with the phenomenon of mesoparasitism.     

The evolutionary history of parasitic sucking lice and their rodent hosts: A case of evolutionary co-divergences

Parasites are often dependent on their hosts for survival and dispersal and this led to a hypothesis that the evolution of obligate permanent host-specific parasites specifically will show phylogenetic congruence with their hosts. To investigate the factors influencing parasite evolution, mitochondrial- and nuclear DNA sequence data were used to test for genetic co-divergences between Hoplopleura and Polyplax lice occurring on four rodent taxa associated with the Aethomys/Micaelamys rodent complex. Mitochondrial DNA haplotype networks drawn from 24 rodents and 74 obligate permanent lice supported the existence of at least eight genetically distinct parasite lineages. Bayesian and maximum likelihood analyses showed considerable congruence between the phylogenies of the parasites and their hosts, and these finding were also partly supported in a fair amount of overlap in the timing of divergences. Jane co-phylogenetic reconstructions illustrated that co-divergences are the most parsimonious solution to explain the evolution within Polyplax, and also within Hoplopleura. Based on mitochondrial DNA cytochrome oxidase subunit I sequence distances of >13% between strongly supported monophyletic parasite lineages, coupled to some unique morphological features detected for both lice taxa occurring on Micaelamys granti, we propose that the taxonomy of Polyplax and Hoplopleura studied herein is in need of revision. In addition, our findings provide examples of perfect topological co-divergence between parasites and their hosts, and in doing so also provide circumstantial evidence for co-evolution between these permanent host-specific parasites and their hosts. We argue that the signal of co-divergence is partly enforced by limited opportunities for host switching events across the landscape.     

Differences in pectoral fin spine morphology between vocal and silent clades of catfishes (Order Siluriformes): Ecomorphological implications

Stridulatory sound-producing behavior is widespread across catfish families, but some are silent. To understand why, we compared spine morphology and ecotype of silent and vocal clades. We determined vocal ability of laboratory specimens during disturbance behavior. Vocal families had bony (not flexible or segmented) spines, well-developed anterior and/or posterior serrations, and statistically significantly longer spines. We compared morphology of the proximal end of the pectoral spine between vocal and silent species. For vocal taxa, microscopic rounded or bladed ridges or knobs were present on the dorsal process. Most silent species had reduced processes with exclusively smooth, convoluted, or honeycombed surfaces very similar to spine-locking surfaces, or they had novel surfaces (beaded, vacuolated, cobwebbed). Most callichthyids had ridges but many were silent during disturbance. All doradid, most auchenipterid and most mochokid species were vocal and had ridges or knobs. Within the Auchenipteridae, vocal species had spines with greater weight and serration development but not length. Silent auchenipterids had thin, brittle, distally segmented spines with few microscopic serrations on only one margin and a highly reduced dorsal process lacking any known vocal morphology. Silent auchenipterids are derived and pelagic, while all vocal genera are basal and benthopelagic. This is the first phylogenetic evidence for stridulation mechanism loss within catfishes. Phylogenetic mapping of vocal ability, spine condition, and ecotype revealed the repeated presence of silence and vocal taxa, short and long spines, and ecotype shifts within clades. The appearance and loss of vocal behavior and supporting morphologies may have facilitated diversification among catfishes [Current Zoology 56 (1): 73-89 2010].     

Consequences of asymmetric competition between resident and invasive defoliators: A novel empirically based modelling approach

Invasive species can have profound effects on a resident community via indirect interactions among community members. While long periodic cycles in population dynamics can make the experimental observation of the indirect effects difficult, modelling the possible effects on an evolutionary time scale may provide the much needed information on the potential threats of the invasive species on the ecosystem. Using empirical data from a recent invasion in northernmost Fennoscandia, we applied adaptive dynamics theory and modelled the long term consequences of the invasion by the winter moth into the resident community. Specifically, we investigated the outcome of the observed short-term asymmetric preferences of generalist predators and specialist parasitoids on the long term population dynamics of the invasive winter moth and resident autumnal moth sharing these natural enemies. Our results indicate that coexistence after the invasion is possible. However, the outcome of the indirect interaction on the population dynamics of the moth species was variable and the dynamics might not be persistent on an evolutionary time scale. In addition, the indirect interactions between the two moth species via shared natural enemies were able to cause asynchrony in the population cycles corresponding to field observations from previous sympatric outbreak areas. Therefore, the invasion may cause drastic changes in the resident community, for example by prolonging outbreak periods of birch-feeding moths, increasing the average population densities of the moths or, alternatively, leading to extinction of the resident moth species or to equilibrium densities of the two, formerly cyclic, herbivores.     

寄生真菌与百合科寄主分类学关系初探

将寄生在百合科上11个属的真菌列成图谱,发现霜霉目（Peronosporales)只寄生葱属（Allium),小煤炱目（Meliolales)只寄生菝葜属（Smilax)。结果显示,葱属和菝葜属之间以及与其他9个属之间的亲缘关系均比较远,这与哈钦松分类系统相吻合,这对有较高经济价值的百合科的分类提供了重要佐证。     

The geographic structure of selection on a coevolving interaction between social parasitic wasps and their hosts hampers social evolution

Social parasites exploit societies, rather than organisms, and rear their brood in social insect colonies at the expense of their hosts, triggering a coevolutionary process that may affect host social structure. The resulting coevolutionary trajectories may be further altered by selection imposed by predators, which exploit the abundant resources concentrated in these nests. Here, we show that geographic differences in selection imposed by predators affects the structure of selection on coevolving hosts and their social parasites. In a multiyear study, we monitored the fate of the annual breeding attempts of the solitary nesting foundresses of Polistes biglumis wasps in four geographically distinct populations that varied in levels of attack by the congeneric social parasite, P. atrimandibularis. Foundress fitness depended mostly on whether, during the long founding phase, a colony was invaded by social parasites or attacked by predators. Foundresses from each population differed in morphological traits and reproductive tactics that were consistent with selection imposed by their natural enemies and in ways that may affect host sociality. In turn, parasite traits were consistent with selection imposed locally by hosts, implying a geographic mosaic of coevolution in this brood parasitic interaction.     

Dispersal behavior of the parasitic wasp Cotesia urabae (Hymenoptera: Braconidae): A recently introduced biocontrol agent for the control of Uraba lugens (Lepidoptera: Nolidae) in New Zealand

Estimates of the dispersal range of a recently introduced biocontrol agent in its new environment are vital to understanding its relative searching capacity, and to foresee the maximum area that could be covered in a release event. In New Zealand, the solitary endoparasitoid Cotesia urabae Austin and Allen (Hymenoptera: Braconidae) was first released in January 2011 as a biological control agent for the gum leaf skeletoniser, Uraba lugens Walker (Lepidoptera: Nolidae). The objective of this study was to utilize an experimental approach to quantify the dispersal behavior of one generation of C. urabae. In our experiment, which used sentinel larvae as target hosts, parasitoids dispersed up to 20 m away from the release point but parasitism was highest within 5 m of the release site. A high level of parasitism was observed at the release tree (87.6%) which suggests that most of the females released may have stayed there. According to the dispersal model developed from the data collected, Cotesia would be able to disperse up to 53 m in one release event. In addition, significant differences were found between the different directions tested for dispersal, showing a clear downwind effect on dispersal suggesting that wind has a direct effect on the dispersal behavior of C. urabae in the field.     

Morphological correlates of serotonin-neuropeptide Y interactions in the rat suprachiasmatic nucleus: Combined radioautographic and immunocytochemical data

Summary The morphological substrate of putative serotonin (5-HT)/neuropeptide Y (NPY) interactions in thé suprachiasmatic nucleus (SCN) was investigated by combined radioautography and immunocytochemistry after intraventricular administration of (³H)5-HT in the rat. In the ventral portion of the SCN, the distribution of (³H)5-HT uptake sites overlapped closely the NPY-immunoreactive terminals. Previous investigations have shown that the dense 5-HT and NPY innervations of the SCN originate in different structures, i.e., the midbrain raphe nuclei and the ventral lateral geniculate nucleus, respectively. Accordingly, in the present study, destruction of 5-HT afferents by 5,7-dihydroxytryptamine was not found to induce any modification in NPY staining and, in ultrastructural immuno-radioautographic preparations, two distinct pools of axonal varicosities could be identified. Both 5-HT and NPY terminals established morphologically defined synaptic junctions, sometimes on the same neuronal target. Some cases of direct axo-axonic appositions between the two types of terminals were also encountered. These data constitute additional criteria for characterizing the cytological basis of the multiple transmitter interactions presumably involved in the function of the SCN as a central regulator of circadian biological rhythms.     

Coevolutionary analyses of the relationships between piroplasmids and their hard tick hosts

Host–parasite coevolution is a key driver of biological diversity. To examine the evolutionary relationships between piroplasmids and their hard tick hosts, we calculated the molecular clock and conducted phylogenetic analyses of both groups. Based on our results, we conclude that the divergence time of piroplasmids (~56 Mya) is later than divergence time of their hard tick hosts (~86 Mya). From analyses of the evolution of both piroplasmid and vector lineages and their association, we know that hard ticks transmit piroplasmids with high genus specificity and low species specificity.     

Trophic relationships between the larvae of two freshwater mussels and their fish hosts

Freshwater mussels of the order Unionoida have life cycles that include larval attachment to and later metamorphosis on suitable host fishes. Information on the trophic relationship between unionoid larvae and their host fishes is scarce. We investigated the trophic interaction between fish hosts and encysted larvae of two species of freshwater mussels, Margaritifera margaritifera and Unio crassus, using stable isotope analyses of larvae and juvenile mussels as well as of host fish gill and muscle tissues before and after infestation. Due to different life histories and durations of host‐encystment, mass and size increase in M. margaritifera during the host‐dependent phase were greater than those of U. crassus. δ¹³C and δ¹⁵N signatures of juvenile mussels approached isotopic signatures of fish tissues, indicating a parasitic relationship between mussels and their hosts. Shifts were more pronounced for M. margaritifera, which had a five‐fold longer host‐dependent phase than U. crassus. The results of this study suggest that stable isotope analyses are a valuable tool for characterizing trophic relationships and life history strategies in host–parasite systems. In the case of unionoid mussels, stable isotopic shifts of the larvae are indicative of the nutritional versus phoretic importance of the host.     

Interactions between searching strategies ofDrosophila parasitoids and the polymorphic behavior of their hosts

Two strains of Drosophila melanogaster, rover and sitter, differing in locomotion while foraging were simultaneously exposed to females of either Leptopilina boulardi or Ganaspis xanthopoda (parasitic Hymenoptera). These two parasitoids show different modes of host-searching behavior, ovipositor searching, or vibrotaxis, respectively. L. boulardi parasitized the sitter host strain significantly more than the rover. In contrast, G. xanthopoda parasitized the rover strain more than the sitter. In one case, L. boulardi selected far more sitters than rovers in population cage experiments. We also describe the frequencies of rovers and sitters in three natural populations where the local parasitoid community may have partially contributed to the differences in rover and sitter frequencies.     

Evolutionary relationships between digeneans of the family Brachycladiidae Odhner, 1905 and their marine mammal hosts: A cophylogenetic study

Cophylogenetic studies examine the congruence between host and parasite phylogenies. There are few studies that quantify the relative contribution of coevolutionary events, i.e. duplication, loss, failure-to-diverge, host-switching and spreading in trophically-transmitted parasites at the marine realm. We addressed this issue in the Brachycladiidae, a cosmopolitan digenean family specific to marine mammals. We used, for the first time, distance-based and event-based methods to explicitly test the coevolutionary events that have shaped the current brachycladiid-marine mammal associations. Parasite phylogeny was constructed using mtDNA ND3 sequences of nine brachycladiid species, and host phylogeny using cytochrome b sequences of 104 mammalian species. A total of 50 host-parasite links were identified. Distance-based methods supported the hypothesis of a global non-random association of host and parasite phylogenies. Significant individual links (i.e., 24 out of 50) were those related to Campula oblonga, Nasitrema delphini, N. globicephalae and Brachycladium atlanticum and their associated taxa from the Delphinoidea. Regarding event-based methods, we explored 54 schemes using different combinations of costs for each potential coevolutionary event. Three coevolutionary scenarios were identified across all schemes and in all cases the number of loss events (87–156) was the most numerous, followed by failure-to-diverge (40), duplication (3–6), host-switching (0–3) and cospeciation (0–2). We developed a framework to interpret the evolution of this host-parasite system and confirmed that failure-to-diverge and colonization with or without subsequent diversification could have been decisive in the establishment of the associations between brachycladiids and marine mammals.     

Arms races between social parasites and their hosts: geographic patterns of manipulation and resistance

The evolutionary interactions between permanently social parasiticspecies and their hosts are of special interest because socialparasites are not only closely dependent on, but are also closelyrelated to, their hosts. The small European slavemaker Harpagoxenussublaevis has evolved several characters that help manipulateits host. In this study we investigated adaptations of thissocial parasite to its local hosts and the geographic patternof host resistance in two main host species from three differentpopulations. In behavioral experiments, we examined whetherhost colonies from three geographically distant Leptothoraxacervorum populations varied in their ability to defend thenest against social parasites. Naive colonies from the unparasitizedEnglish population killed attacking slavemakers more often thandid host colonies from two parasitized populations. We alsofound strong interpopulation variation in the ability of theslavemaker to manipulate host behavior. H. sublaevis uses theDufour gland secretion to induce intracolonial fights and, ingeneral, this "propaganda" substance was most effective againstlocal hosts. Our results suggest that the social parasite isleading the arms race in this aspect. Similar experiments uncovereddifferences between two populations of the second host speciesL. muscorum and could demonstrate that nest defense in bothhost species is similarly efficient. In L. acervorum, monogynouscolonies were more successful in nest defense, whereas socialstructure had no impact in L. muscorum. Colony size did notaffect the efficacy of nest defense in either host species.The caste of the slavemaker had a strong influence on the successof an attack.     

寄生植物的生物学特性及生态学效应

寄生植物是陆地生态系统的重要组成部分,在多数生态系统中均有分布.寄生植物完全或部分依赖于寄主植物获取有机养分、无机养分和水分等,以满足自身生长发育需求.在生态学效应方面,寄生植物不但直接影响寄主植物的生长发育,也会通过改变寄主植物的竞争力而影响植物群落组成.寄生植物对寄主植物个体水平的影响多是消极的,并能给人类的生产活动造成直接经济损失,故对寄生植物的防治一直是人们关注的热点问题;在群落水平上,寄生植物对促进植物群落的物种多样性有积极的意义,基于此,寄生植物有潜在利用价值.深入了解寄生植物的生理生态学特性,对有害寄生植物的防除和有益寄生植物的利用有重要价值.本文对寄生植物的生物学特性,包括其寄生类型、寄主范围及偏好、寄主识别和吸器的形成与功能,进行了阐述,并就寄生植物对寄主植物和群落结构的影响进行了探讨,对相关研究前景进行了展望.     

Pineal-retinal relationships: rhythmic biosynthesis and immunocytochemical localization of melatonin in the retina of the pike (Esox lucius)

Summary The levels of melatonin and the activities of two enzymes of the melatonin biosynthetic pathway, serotonin N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT), were measured throughout the light-dark cycle in the retina of a teleost fish, the pike. HIOMT activity did not display significant variations, whereas NAT activity and melatonin content showed a daily rhythm, high levels occurring during the night. The profiles of the latter two rhythms did not closely match one another and differed from those previously described in the pineal organ of the same species. These results are discussed with respect to a possible paracrine role of retinal melatonin. Melatonin-like immunoreactivity was found in the photoreceptor cell layer and in the Müller cells of the inner nuclear layer. The intensity of the melatonin-like immunoreactivity varied throughout the 24 h light-dark cycle, in good correlation with the variations in the melatonin level as measured by radioimmunoassay.This article is dedicated to the memory of Dr. Klaus Hoffmann     

Characterization and localization of an Mr 225 kDa polypeptide specifically involved in the defence mechanisms of the clam Tapes semidecussatus

Parasitosis by the trophozoite protozoan Perkinsus sp. (Apicomplexa, Perkinsea) induces in the gill filaments of the clam Tapes semidecussatus (Mollusca, Bivalvia) a cellular reaction, which is constituted by infiltrated granulocytes. This cellular reaction has characteristics of those of a holocrine gland, since the parasites are encapsulated by the secretion product of the granulocytes after cell death. An enriched fraction of prezoosporangia and their associated capsule was obtained after culture of the parasitized gills in fluid thioglycollate medium. Specific polypeptides from this fraction were separated by SDS-PAGE and isolated for rabbit immunizations. The serum obtained against an Mr 225 kDa polypeptide, revealed its exclusive localization in the capsule and in the granules of the infiltrated granulocytes, thus indicating that this polypeptide is synthesized by these cells and secreted, in a polarized way, around the trophozoites resulting in their encapsulation. Selective deglycosylation of the polypeptide, by Endo H and alkaline -elimination, did not show an effect on its molecular weight or antibody recognition. Furthermore, the absence of the 225 kDa band in the Western-blots of non-parasitized gills indicated the specific association of this polypeptide with the parasitosis. Finally, this is the first tissue-specific factor described in molluscs in relation to defence mechanisms.     

Nuclear structure in early mouse embryos: A comparative ultrastructural and immunocytochemical study with special emphasis on the "2-cell block in vitro"

The embryos from many outbred and inbred strains of mice are arrested at the late 2-cell stage when cultured in vitro in simple culture media. This phenomenon is referred to as the "2-cell block in vitro". The ultrastructural morphology of the nuclei of the blocked embryos is not yet well described. In the present paper we documented the results of a comparative study on the nuclei of mouse embryos, both normally developing and arrested at the 2-cell stage. The blocked embryos maintain the morphological integrity of their nuclei. Main nuclear domains (nucleolus precursor bodies, interchromatin granule clusters, perichromatin granules, and perichromatin fibrils), typical for the control embryos, are observed in the blocked ones. A number and morphological characteristics of these nuclear substructures are not changed significantly in the blocked embryos. At the same time, RNA polymerase II and pre-mRNA splicing factors are redistributed in the nucleus of the blocked embryos. Although something goes to show that nuclear organization of the blocked embryos differ from that of the control, we could not reveal in the blocked embryos distinct signs of degeneration which might characterize aged or dying cells. Our data confirm a peculiar functional state of the 2-cell blocked embryos.     

Success of aphid parasitoids and their hosts varies with ant attendance: A field study

Aphid–ant associations are often described as mutually beneficial interactions in which honeydew is traded for protection from predators and parasitoids. The aim of the present study was to determine parasitization avoidance in ant‐tended aphid colonies. Field experiments were carried out on two host plants: hoary cress Lepidium draba (Brassicaceae) and Canadian teasel Cirsium arvense (Asteraceae). Lepidium was host to Acyrthosiphon gossypii (Aphididae) tended by the ant Lasius turcicus (Formicidae) and attacked by two parasitoids, Trioxys asiaticus (Braconidae) and Lysiphlebus fabarum (Braconidae). Cirsium was host to Brachycaudus cardui tended by Crematogaster sordidula and attacked by L. fabarum and Aphidius colemani (Braconidae). The per capita population growth rate of A. gossypii was significantly higher in the presence of ants, while B. cardui was negatively affected, albeit non‐significantly. The parasitism rate of A. gossypii decreased significantly when tended by Lasius turcicus, but the presence of Crematogaster sordidula in colonies of B. cardui significantly increased parasitism. Our results indicate that the effects of ant attendance vary between different aphid–ant interactions. Moreover, parasitoids can benefit from the presence of ants under some conditions.