Neotropical Monogenoidea. 43. Diplectanum monticellii n. sp. (Diplectanidae) from the gills of Cynoscion leiarchus (Perciformes: Sciaenidae) in Brazil

Diplectanum monticellii n. sp. is described from the gills of Cynoscion leiarchus, a marine Sciaenidae, from Itacuru?á, Rio de Janeiro (type locality); Baía de Guaratuba, Paraná; and Pontal do Sul, Paraná in Brazil. The new species is characterized by the following features: bell-shaped male copulatory organ with a sleevelike base, accessory piece absent, vas deferens looping left intestinal cecum, vaginal aperture sinistroventral, and ventral anchor with elongate superficial and deep roots.     

Effective proliferation of human regulatory T cells requires a strong costimulatory CD28 signal that cannot be substituted by IL-2

The strength of immune repression by regulatory T (Treg) cells is thought to depend on the efficiency of Treg cell activation. The stimuli and their individual strength required to activate resting human Treg cells, however, have so far not been elucidated in detail. We reveal here that induction of proliferation of human CD4(+)C25(+) Treg cells requires an extraordinary strong CD28 costimulatory signal in addition to TCR/CD3 engagement. CD28 costimulation, noteworthy, cannot be substituted by IL-2 to induce proliferation of Treg cells, which is in contrast to CD4(+)CD25(-) T cells. IL-2, in contrast, prevents spontaneous apoptosis of Treg cells, but does not initiate their amplification. IL-2 and CD28 costimulation clearly exhibit disparate effects on Treg cells which are in contrast to those on CD4(+)CD25(-) T cells. Moreover, the prerequisites for Treg cell proliferation differ strikingly from those for effector T cells, implying a balanced orchestration in initiating and limiting a T cell immune response. In addition, data are of relevance for the design of therapeutic strategies involving IL-2 administration and CD28 costimulation.     

Caterpillar regurgitant induces pore formation in plant membranes

Formation of channel-like pores in a plant membrane was induced within seconds after application of an aqueous solution containing regurgitant of the insect larvae Spodoptera littoralis. Gated pore currents recorded on the tonoplast of the Charophyte Chara corallina displayed conductances up to several hundred pS. A voltage-dependent gating reaction supports the assumption that pore-forming molecules have amphipathic properties. Regurgitant samples separated into masses smaller or larger than 3kDa were evaluated by patch-clamp and mass spectroscopy. Fractions containing peptides larger than 3kDa constituted pores of large conductances, peptides smaller than 3kDa constituted pores of small conductances. Peptide-free eluates did not constitute conducting pores, indicating that pore-forming components in regurgitant are membrane-spanning oligopeptides.     

Neotropical Monogenoidea. 50. Oviparous gyrodactylids from loricariid and pimelodid catfishes in Brazil, with the proposal of Phanerothecioides n. g., Onychogyrodactylus n. g. and Aglaiogyrodactylus n. g. (Polyonchoinea: Gyrodactylidea)

The diagnosis of Phanerothecium Kritsky & Thatcher, 1977 is amended, and Phanerothecioides n. g., Onychogyrodactylus n. g. and Aglaiogyrodactylus n. g., all comprised of oviparous gyrodactylids (Monogenoidea: Polyonchoinea), are proposed to accommodate 11 of the 15 species (14 new to science) herein described and/or reported from loricariid and pimelodid catfishes (Teleostei: Siluriformes) in Brazil: Phanerothecium harrisi Kritsky & Boeger, 1991, P. spinatoides n. sp. and P. deiropedeum n. sp. all from Hypostomus spp.; P. spinulatum n. sp. from Hypostomus cf. regani; Phanerothecioides agostinhoi n. g., n. sp. (type-species) from Hypostomus spp. and Pseudoplatystoma fasciatum; Onychogyrodactylus sudis n. g., n. sp. (type-species) and O. hydaticus n. sp. both from Ancistrus multispinus; Aglaiogyrodactylus forficulatus n. g., n. sp. (type-species) from Kronichthys lacerta; A. pedunculatus n. sp. from Hisonotus sp.; A. guttus n. sp. from Pseudotothyris obtusa; A. salebrosus n. sp., A. conei n. sp. and A. ctenistus n. sp. all from Pareiorhaphis parmula; and A. calamus n. sp. and A. forficuloides n. sp. both from Schizolecis guntheri. Phanerothecioides n. g. is characterised by oviparous forms lacking superficial and deep haptoral bars and pregermarial vitelline follicles, and by having a conspicuous testis in adult specimens, a syncytial prostatic gland, a reduced copulatory sac and vitelline ducts in the form of an inverted ‘U’. Onychogyrodactylus n. g. is differentiated from all other oviparous gyrodactylid genera by its members having a spine-like accessory sclerite enclosed in a separate pouch associated with the terminal male genitalia. Species of Aglaiogyrodactylus n. g. possess H-shaped vitelline ducts and a complex accessory piece and sclerotised or non-sclerotised male copulatory organ enclosed within the copulatory sac.     

Histopathology of the mangrove land crab Ucides cordatus (Ocypodidae) affected by lethargic crab disease

Lethargic crab disease (LCD) has caused extensive epizootic mortality of the mangrove land crab Ucides cordatus (Linnaeus 1763) (Brachyura: Ocypodidae) along the Brazilian coast. Direct culture of tissue samples from sick crabs and subsequent isolation and purification identified the causative agent as an Exophiala species of fungus. The histopathology of crabs with variable signs of LCD indicates that the most affected tissues are the epidermis, connective tissue, heart, hepatopancreas, nervous system, and gills. Gonads, somatic muscles, and digestive system are less affected by the fungus. The observed pathology is compatible with the clinical signs of LCD. Necrosis, tissue degeneration, and congestion of hemal sinuses and vessels are present in heavily infected organs. Nerve fibers may be compressed by accumulations of yeast-like cells. In heavy infections the tissue of gill lamellae is destroyed with subsequent dilation or compression. Cellular immune responses include hemocytic infiltration, agglutination and encapsulation, and phagocytosis. Phagocytosis of yeast-like cells is abundant in the connective tissue associated with the exoskeleton. These results indicate that LCD is the result of a systemic phaeohyphomycosis caused by a species of Exophiala. The present study also suggests that dispersal of the fungus within the crab occurs through the hemal system.     

Synergism between mutational meltdown and Red Queen in parthenogenetic biotypes of the freshwater planarian Schmidtea polychroa

Do parasites and accumulation of deleterious mutations act synergistically in balancing the costs of sex? We addressed this possibility in the freshwater planarian flatworm Schmidtea polychroa. Sexual and parthenogenetic forms of this species sometimes coexist but show no ecological separation. Previous studies indicate that in a mixed sexual/ parthenogenetic population in Lago di Caldonazzo (N. Italy) parthenogens get more frequently infected with parasites. At the same time, they suffer from higher embryo mortality, which has been interpreted as a sign of accumulation of deleterious mutations. In the present study, we test whether these two factors are correlated, by focusing on the differences among the clonal lineages of a predominantly parthenogenetic subpopulation. Our results suggest that, for two out of three parasite types found, the infections are positively associated with the indirect measure of host mutation load.     

Spatial behaviour in the Aquatic Warbler (Acrocephalus paludicola) during mating and breeding

Summary The range use of both sexes of the Aquatic Warbler was studied during two breeding seasons by radio-tracking. Males used home ranges of up to 8 ha. These home ranges over-lapped by up to 74 %, (mean 51 %) between individuals. During the mating period and prior to nesting, females used isolated sites of 2.8 to 6.4 ha (mean: 4.2 ha) within activity ranges of 100 to 160 ha (mean: 120 ha). Home ranges of different females overlapped by up to 20 %. However, during nest-building and incubation, the average size of home ranges in females was only 1.6 ha. Since no constant ranges were observed, we conclude that Aquatic Warblers are not territorial in the breeding season.

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Räumliches Verhalten des Seggenrohrsängers (Acrocephalus paludicola) während Partnerfindung und Bebrütung

Zusammenfassung In zwei aufeinanderfolgenden Brutzeiten wurde die Raumnutzung von Seggenrohrsängern mittels Telemetrie untersucht. Die ermittelte Größe der Streifgebiete von Männchen betrug in der gesamten Brutzeit bis zu 8 ha. In dem Streifgebiet eines einzelnen Männchens wurden bis zu elf telemetrierte Männchen festgestellt. Die Überlappungen der Streifgebiete telemetrierter Männchen betrugen durchschnittlich 51 %, maximal 74 %. Weibchen nutzten während der Paarungszeit nicht zusammenhängende inselartige Areale von insgesamt 2,8 bis 6,4 ha (Mittelwert 4,2 ha) innerhalb von Aktionsräumen von 110 bis 160 ha (Mittelwert 120 ha). Diese Areale überlappten zu 20 % mit den Aufenthaltsgebieten anderer Weibchen. Während des Brütens sank die Größe der Streifgebiete der Weibchen auf durchschnittlich 1,6 ha. Da im Beobachtungszeitraum keine konstant genutzten Aufenthaltsgebiete vorlagen, schließen wir, daß sich Seggenrohrsänger in der Brutzeit nicht territorial verhalten.

     

Evolution of ITS1 rDNA in the Digenea (Platyhelminthes: Trematoda): 3′ End Sequence Conservation and Its Phylogenetic Utility

A comparison of ribosomal internal transcribed spacer 1 (ITS1) elements of digenetic trematodes (Platyhelminthes) including unidentified digeneans isolated from Cyathura carinata (Crustacea: Isopoda) revealed DNA sequence similarities at more than half of the spacer at its 3′ end. Primary sequence similarity was shown to be associated with secondary structure conservation, which suggested that similarity is due to identity by descent and not chance. Using an analysis of apomorphies, the sequence data were shown to produce a distinct phylogenetic signal. This was confirmed by the consistency of results of different tree reconstruction methods such as distance approaches, maximum parsimony, and maximum likelihood. Morphological evidence additionally supported the phylogenetic tree based on ITS1 data and the inferred phylogenetic position of the unidentified digeneans of C. carinata met the expectations from known trematode life-cycle patterns. Although ribosomal ITS1 elements are generally believed to be too variable for phylogenetic analysis above the species or genus level, the overall consistency of the results of this study strongly suggests that this is not the case in digenetic trematodes. Here, 3′ end ITS1 sequence data seem to provide a valuable tool for elucidating phylogenetic relationships of a broad range of phylogenetically distinct taxa. Received: 20 October 1997 / Accepted: 24 March 1998