Occurrence of symbiotic turbellarians in the oyster,Crassostrea virginica

Crassostrea virginica was collected from several locations where it is cultured, both along the Northumberland Strait of New Brunswick and Malpeque Bay on the coast of Prince Edward Island. The oysters were found with two turbellarians on their gills. Urastoma cyprinae (Graff) was found in the oysters mostly during the warmer months of the year in numbers averaging as high as 50 worms per host (N = 50) and with as much as 78% of the host population infected (N = 100). Paravortex gemellipara (Linton) was also found during warmer months, but much less frequently or abundantly.Both male and female oysters were found to have U. cyprinae. No eggs or recent young of U. cyprinae were found in hosts; female-mature individuals of P. gemellipara with young were found from June through August.     

Notes on the biology of some psammophile Turbellaria of the Black Sea

The biology of two marine turbellarians, Cercyra hastata (Tricladida) and Pseudomonocelis ophiocephala (Proseriata) has been studied over a period of five years. They are the main components of the biocoenosis of the saccocirrus sand of Sevastopol Bay. These species have a significant role in the processes of secondary production and transformation of the organic matter in the coastal zone.     

Two species of Ergasilidae (Copepoda: Poecilostomatoida) parasitic on the gills of Mugil cephalus Linnaeus (Pisces: Teleostei), with proposition of a new genus Dermoergasilus

A new genus of Ergasilidae (Dermoergasilus) is proposed to accommodate Ergasilus amplectens Dogiel et Akhmerov, 1952; E. coleus Cressey, 1970; and E. semicoleus Cressey, 1970. Dermoergasilus amplectens (Dogiel et Akhmerov, 1952) and Nipergasilus bora (Yamaguti, 1939) are redescribed based on the specimens recovered from the gills of Mugil cephalus L. collected in Kojima Bay, Okayama Prefecture, Japan.     

Fine Structural Observations on the Turbellarians Stenostomum sp. and Microstomum lineare with Special Reference to the Extracellular Matrix and Connective Tissue Systems

Employing transmission electron microscopy, observations were made on epidermis, muscle cells and connective tissue systems, with special emphasis on extracellular matrix components (ECM), in two rather primitive turbellarians: Stenostomum sp. (Catenulida) and Microstomum lineare (Macrostomida). In Stenostomum the only ECM components found are basal laminae, predominantly situated subepidermally. In Microstomum ECM is well developed and connective tissue filaments abundant in conspicuous extracellular spaces. It is uncertain whether basal laminae exist. The finding of basal lamina structures as the only ECM component present in Stenostomum makes it now possible to establish a complete ECM and connective tissue hierarchy in turbellarians, ranging from a purely cellular type with no ECM present to systems dominated by ECM and very similar to loose connective tissue in vertebrates. Comparative aspects of ECM and connective tissue systems in turbellarians are discussed in addition to the difficulties and ambiguities regarding definition and nomenclature of basal matrices as basal laminae and subepidermal membranes.     

Monogenea of marine fishes from Hainan Island, China. VIII. Two new species of Euryhaliotrema Kritsky & Boeger, 2002 (Dactylogyridae) from Lutjanus argentimaculatus (Teleostei: Lutjanidae)

This paper reports two new species of Euryhaliotrema Kritsky & Boeger, 2002 collected from the gills of Lutjanus argentimaculatus (Forsskål). E. xinyingense n. sp. is similar to Euryhaliotrema atlanticum Kritsky & Boeger, 2002 in the structure of copulatory apparatus, but differs from the latter in the shape of anchors and the structure of vagina. E. hainanense n. sp. also closely resembles E. atlanticum Kritsky & Boeger, 2002, but differs from the latter in the structure of haptor and the shape of accessory piece.     

The protozoan epizooites found on the gills of Gammarus pulex

Four protozoan epizooites are found attached to the gills of Gammarus pulex collected from Rutland Water. The suctorian, Dendrocometes paradoxus, and the peritrichs, Epistylis sp. and Lagenophrys sp., are relatively abundant, but the chonotrich, Spirochona gemmipara is only occasionally found. SEM studies of various aspects of these protozoa are described. SEM has been useful in distinguishing between the two species of Lagenophrys found on Gammarus. L. ampulla is found on the gills and L. nassa is found on the limbs. The two species are distinguished by the differences in the structure of the loricastome. The relationship between the epizooites and their host is discussed briefly.     

Polymorphic microsatellite loci in Eurytoma brunniventris,a generalist parasitoid in oak cynipid galls

Eurytoma brunniventris is a parasitic wasp with a wide range of host species. We have developed primers for nine polymorphic microsatellite loci to allow examination of intraspecific population subdivision associated with two aspects of the biology of their hosts: host species (oak gallwasps) and the tree on which the gallwasp develops (different oak species). All nine loci amplified well across individuals collected from a range of gallwasp species and across two oak taxa. These microsatellite loci are potentially of value in the study of closely related economic pests such as seed predators of almonds (E. amygdali) and pistachios (E. plotnikovi).     

Subinhibitory concentrations of nalidixic acid alter bacterial physiology and induce anthropogenic resistance in a commensal strain of Escherichia coli in vitro

The human gut houses a complex group of bacterial genera, including both opportunistic pathogens and commensal micro-organisms. These are regularly exposed to antibiotics, and their subinhibitory concentrations play a pivotal role in shaping the microbial responses. This study was aimed to investigate the effects exerted by sub-MICs of nalidixic acid (NA) on the growth rate, bacterial motility, biofilm formation and expression of outer membrane proteins (OMPs) in a commensal strain of E. coli. The NA-sensitive strain was sequentially passaged under sub-MICs of NA. E-test was used to determine the MIC values of NA. Results indicated significant changes in the growth profile of commensal E. coli upon exposure to NA at sub-MICs. Differential expression of OMPs was observed in cells treated with sub-MICs of NA. Bacterial motility was reduced under 1/2 MIC of NA. Interestingly, successive passaging under 1/2 MIC of NA led to the emergence of resistant E. coli with an increased MIC value of 64 µg ml⁻¹ in just 24 days. The NA-resistant variant was confirmed by comparing its 16S rRNA sequence to that of the sensitive commensal strain. Mutations in the Quinolone Resistance-Determining Regions (QRDRs) of chromosomal gyrA, and Topoisomerase IV-encoding parC genes were detected in NA-resistant E. coli. Our results demonstrate how antibiotics play an important role as signalling molecules or elicitors in driving the pathogenicity of commensal bacteria in vitro.     

Potential effect of ice formation on Antarctic pelagic copepods: salinity induced mortality of Calanus propinquus and Metridia gerlachei in comparison to sympagic acoel turbellarians

The salinity tolerance of two dominant Antarctic planktic copepods (Calanus propinquus and Metridia gerlachei) was tested over a range from 34 to 85 PSU and compared with that of sympagic turbellarians. The copepods survived only at a salinity of 34, higher salinities causing death within days. The turbellarians survived at salinities up to 75. The data imply that C. propinquus and M. gerlachei will not survive incorporation into newly forming sea ice because of the increasing brine salinity in new ice. Received: 27 January 1998 / Accepted: 11 April 1998     

Morphology and ultrastructure of the gills of terrestrial crabs (Crustacea,Gecarcinidae and Grapsidae): Adaptations for air-breathing

Summary The terrestrial crabsGeograpsus grayi, Geograpsus crinipes, Cardisoma hirtipes andGecarcoidea natalis have a reduced number of gills and show a reduced planar gill surface (SA) compared to aquatic species. Gill lamellae are stiffened and thickened (increasing blood/gas (BG) diffusion distances) and nodules maintain wide spacing between lamellae. Haemolymph is directed through the gill lamellae by rows of pillar cells and in the afferent region an intralamellar septum splits the haemolymph into two parallel networks. Gaps in the lines of pillar cells allow movement of haemolymph between adjacent channels. The afferent vessel distributes haemolymph to the lamella via a number of direct channels including the marginal canal and in large gills with the aid of a long, forked sinus which supplies the ventral and central regions of the lamellae. The marginal canal functions in both distribution and collection of haemolymph; the role varies with species. Potential flow-control sites were identified at the junctions between afferent and efferent areas and where the efferent channels enter the efferent branchial vessel. Each gill receives a branch from the sternal artery which supplies all the lamellae. Transport epithelia is the principal cell type in the gills of all species examined though its location varies between species, either being confined to certain gills or specific parts of the lamellae.The gill lamellae of air-breathing crabs are clearly modified to breathe air (stiffening and presence of nodules), though the overall contribution of the gills to gas exchange has been reduced (smaller SA and longer BG diffusion distances). The role of the gills in air-breathing crabs thus appears to have switched from one of an efficient aquatic gas-exchanger (thin with large surface area) and transport tissue, to one that is predominantly set up for ion-regulation.Abbreviations a afferent branchial vessel - ac afferent channels - art arteriole - ass artifactual subcuticular space - bl basal lamina - c cuticle - col collagen - ct connective tissue - e efferent branchial vessel - ec efferent channels - epi epithelium - f folds - g Glycogen - h haemolymph - hc haemocyte - is intralamellar septum - m marginal canal - mi mitochondria - mt microtubules - n nucleus - p pillar cell - s shaft of efferent vessel - sd septate desmosome     

Symbiotic Bacteria in Gills and Guts of Chinese Mitten Crab (Eriocheir sinensis) Differ from the Free-Living Bacteria in Water

Aquatic animals have a close relationship with water, but differences in their symbiotic bacteria and the bacterial composition in water remains unclear. Wild or domestic Chinese mitten crabs (Eriocheir sinensis) and the water in which they live were collected from four sampling sites in Jiangsu and Shanghai, China. Bacterial composition in water, gills or guts of E. sinensis, were compared by high-throughput sequencing using 16S rRNA genes. Analysis of >660,000 sequences indicated that bacterial diversity was higher in water than in gills or guts. Tenericutes and Proteobacteria were dominant phyla in guts, while Actinobacteria, Proteobacteria and Bacteroidetes were dominant in gills and water. Non-metric multidimensional scaling analysis indicated that microbiota from gills, guts or water clearly separated into three groups, suggesting that crabs harbor a more specific microbial community than the water in which they live. The dominant OTUs in crab gut were related to Mycoplasmataceae, which were low in abundance in gills, showing that, like mammals, crabs have body-site specific microbiota. OTUs related to Ilumatobacter and Albimonas, which are commonly present in sediment and seawater, were dominant in gills but almost absent from the sampled water. Considering E. sinensis are bottom-dwelling crustacean and they mate in saline water or seawater, behavior and life cycle of crabs may play an important role in shaping the symbiotic bacterial pattern. This study revealed the relationship between the symbiotic bacteria of Chinese mitten crab and their habitat, affording information on the assembly factors of commensal bacteria in aquatic animals.     

Musculature of the facultative parasite Urastoma cyprinae (Platyhelminthes)

In an effort to understand how the feeding motions of Urastoma cyprinae are generated, the arrangement of its musculature was studied using fluorescence microscopy of phalloidin‐linked fluorescent stains and conventional light histology and transmission electron microscopy. BODIPY 558/568 phalloidin and Alexa 488 phalloidin resolved a meshwork of ribbon‐shaped body‐wall muscles as well as inner‐body musculature associated with the pharynx and male copulatory organ. The general pattern of body‐wall muscles in U. cyprinae is similar to that of other rhabdocoel turbellarians in consisting only of circular, longitudinal, and diagonal fibers; the arrangement of these muscles readily correlates with the bending motions the animal undergoes as it feeds at the surface of gills in bivalves it parasitizes. The orogenital atrium of U. cyprinae lies at the posterior apex of the body, opening at a terminal pore. As evidenced by the arrangement of its epithelium and musculature, it appears to be an invagination of the body wall and comes closest of any such duct studied in turbellarians to satisfying the hypothetical model of a “pseudopharynx,” ostensibly adapted as an organ for swallowing and so supplementing the ingestive role of the animal's true pharynx. J. Morphol. 241:207–216, 1999. © 1999 Wiley‐Liss, Inc.     

Seasonal occurrence and ecological aspects of Afrodiplozoon polycotyleus (Monogenea: Diplozoidae) from the gills of three cyprinids from the Nwanedi-Luphephe dams,South Africa

The effect of seasonal changes and ecological aspects of Afrodiplozoon polycotyleus (Paperna, 1973) collected on Labeobarbus marequensis (Smith, 1841), Enteromius trimaculatus (Peters, 1852) and Enteromius radiatus (Peters, 1853) was investigated from January to October 2008. Fish were collected at the Nwanedi-Luphephe dams, Limpopo River System, South Africa using gill, cast and seine nets and electrofishing gear. Enteromius radiatus and E. trimaculatus were the most infested compared with L. marequensis. Seasonal changes had an influence on the intensity of A. polycotyleus, with infestation rates higher in spring, summer and autumn. The adults predominantly infected the medial region of the second gill arch, whereas diporpae were mainly found on the first gill. Neither sex nor water quality changes had an influence on the intensity of the parasite. The health condition of the hosts was not affected by the parasite. The different infestation rates of the parasite between the species could be attributed to host characteristics, behaviour and habitat preferences. The selection of a particular gill/region could be attributed to space for attachment organs and food supply, as well as flow and velocity of the water over the gills. The occurrence of A. polycotyleus on E. radiatus constitutes a new host record.     

False Vertical Rootlets of Epidermal Cilia in the Oncomiracidia of Neoheterocotyle rhinobatidis and Monocotyle spiremae (Platyhelminthes,Monogenea, Monopisthocotylea)

Epidermal cilia of the oncomiracidium of Neoheterocotyle rhinobatidis (Monogenea, Monopisthocotylea, Monocotylidae) have long cross-striated vertical rootlets that are not extensions of the basal bodies as are the vertical rootlets in all catenulid and rhabditophoran turbellarians examined to date. Instead, they originate in the basal part of the horizontal rootlet a short distance from the basal bodies. In Monocotyle spiremae (Monocotylidae), the vertical rootlets are less distinct, with no apparent cross-striation, but they also originate from the basal part of the horizontal rootlets. Epidermal cilia of the oncomiracidium of Zeuxapta seriolae (Monogenea, Polyopisthocotylea, Axinidae) lack vertical rootlets like all other neodermatans examined, but bundles of fibres extend from the basal bodies a short distance into the cytoplasm of the epidermal cells. Monopisthocotylean Monogenea would be intermediate between rhabditophorans and the other neodermatans (in having weakly developed vertical rootles), if these structures were homologous in the two groups. However, in view of the different origin of vertical rootlets in turbellarians and monopisthocolylean oncomiracidia, it is suggested that they are not homologous, and vertical rootlets in the Monopisthocotylea are therefore named “false vertical rootlets”.     

Laboratory adapted Escherichia coli K‐12 becomes a pathogen of Caenorhabditis elegans upon restoration of O antigen biosynthesis

Escherichia coli has been the leading model organism for many decades. It is a fundamental player in modern biology, facilitating the molecular biology revolution of the last century. The acceptance of E. coli as model organism is predicated primarily on the study of one E. coli lineage; E. coli K‐12. However, the antecedents of today's laboratory strains have undergone extensive mutagenesis to create genetically tractable offspring but which resulted in loss of several genetic traits such as O antigen expression. Here we have repaired the wbbL locus, restoring the ability of E. coli K‐12 strain MG1655 to express the O antigen. We demonstrate that O antigen production results in drastic alterations of many phenotypes and the density of the O antigen is critical for the observed phenotypes. Importantly, O antigen production enables laboratory strains of E. coli to enter the gut of the Caenorhabditis elegans worm and to kill C. elegans at rates similar to pathogenic bacterial species. We demonstrate C. elegans killing is a feature of other commensal E. coli. We show killing is associated with bacterial resistance to mechanical shear and persistence in the C. elegans gut. These results suggest C. elegans is not an effective model of human‐pathogenic E. coli infectious disease.     

Colonization factors of diarrheagenicE. coli and their intestinal receptors

WhileEscherichia coli is common as a commensal organism in the distal ileum and colon, the presence of colonization factors (CF) on pathogenic strains ofE. coli facilitates attachment of the organism to intestinal receptor molecules in a species- and tissue-specific fashion. After the initial adherence, colonization occurs, and the involvement of additional virulence determinants leads to illness. EnterotoxigenicE. coli (ETEC) is the most extensively studied of the five categories ofE. coli that cause diarrheal disease, and has the greatest impact on health worldwide. ETEC can be isolated from domestic animals and humans. The biochemistry, genetics, epidemiology, antigenic characteristics, and cell and receptor binding properties of ETEC have been extensively described. Another major category, enteropathogenicE. coli (EPEC), has virulence mechanisms, primarily effacement and cytoskeletal rearrangement of intestinal brush borders, that are distinct from ETEC. An EPEC CF receptor has been purified and characterized as a sialidated transmembrane glycoprotein complex directly attached to actin, thereby associating CF-binding with host-cell response. Three, additional categories ofE. coli diarrheal disease, their colonization factors and their host cell receptors are discussed. It appears that biofilms exist in the intestine in a manner similar to oral bacterial biofilms, and thatE. coli is part of these biofilms as both commensals and pathogens.Abbreviations CF colonization factor - CFA Colonization Factor Antigen - CS coli-surface-associated antigen - EAggEC enteroaggregativeE. coli - ECDD E. coli diarrheal disease - EHEC enterohemorrhagicE. coli - EIEC enteroinvasiveE. coli - EPEC enteropathogenicE. coli - ETEC enterotoxigenicE. coli - Gal galactose - GalNAc N-acetyl galactosamine - LT heat-labile toxin - NeuAc N-acetyl neuraminic acid - PCF Putative colonization factor - RBC red blood cells - SLT Shiga-like toxin - ST heat-stable toxin     

Differences between sympatric populations of <Emphasis Type="Italic">Eotetranychus carpini</Emphasis> collected from <Emphasis Type="Italic">Vitis vinifera</Emphasis> and <Emphasis Type="Italic">Carpinus betulus</Emphasis>: insights from host-switch experiments and molecular data

Eotetranychus carpini (Oudemans) is an important pest of grapevine (Vitis vinifera L.) in southern Europe. This mite is also found on a number of different plants, including Carpinus betulus L., which commonly occurs in stands and hedgerows bordering vineyards, where it may serve as a potential mite reservoir. The economic importance of this pest has motivated a number of studies aimed at investigating whether the mites found on V. vinifera and C. betulus are conspecific. The results obtained to date have been inconclusive. In this study, we used biological and molecular approaches to investigate this issue. First, we conducted host-switch experiments to test the ability of E. carpini to develop on an alternative host plant, using mite populations originally collected on either C. betulus or V. vinifera plants from the same area. Second, we investigated DNA-based differentiation using nucleotide sequences of the ITS1-5.8S-ITS2 region of the ribosomal DNA of individual E. carpini from the populations examined in our host-plant experiments. We also analyzed sequences of individuals collected in other regions (Italy and Slovenia) to estimate species variation. The results from our host-switch experiments suggest the differentiation of mites collected on the two hosts. Mites collected from C. betulus did not survive and reproduce on V. vinifera and vice versa. Our molecular work revealed significant genetic differentiation between the mites collected from the two hosts, but no evidence of genetic variation among specimens collected from the same host species. Our results indicate the existence of host races of E. carpini.     

Temporary pools are not `enemy-free'

Temporary pools are traditionally considered as refuges where the conspicuous anostracans are protected from predation. While this is true for the size-selective predation by fish, there is compelling evidence that invertebrate predation is an important biotic stress regulating temporary pool communities. In rock pools in southeastern Botswana, we studied the impact of some suspected invertebrate predators on populations of the freshwater anostracan Branchipodopsis wolfi by means of observations and manipulative experiments. In a survey of 45 pools, the relationship between B. wolfi natural population sizes and the abundance of suspected predators were never negative for turbellarians and mosquito larvae. When dragonfly larvae, notonectids or tadpoles were present, the anostracan populations were generally non-existent or very small. In enclosure experiments with turbellarians, there was a significant effect of predation within one hour of the start; the average daily predation rate was about 1/4 anostracan per turbellarian. Anostracans from a pool with few turbellarians were slightly less vulnerable than those from a turbellarian-rich pool. Furthermore, there was an indication of males being predated on more than females. With dragonfly larvae and notonectids, the predation effect was marked with all six anostracans in an experiment eaten in less than one day by a single predator (predation rate: about one anostracan every 2 h per predator). In a behavioral study, both sexes of B. wolfi avoided swimming above sediment that held more turbellarians than the open patches; there was no evidence for chemical communication with respect to this behavior.     

Gill-symbiosis in mytilidae associated with wood fall environments

Bivalves belonging to the genera Idas and Adipicola were collected from wood fall environments in the west Pacific (Vanuatu islands) between 300 and 890 m depths in 2004. Bacterial symbionts were checked by three complementary techniques: histological and DAPI staining, in situ hybridization (FISH), and TEM. No bacteria were detected inside the gills of the two species, rejecting the endosymbiosis hypothesis. However, results from our study demonstrated the existence of ectosymbionts colonizing microvilli differentiated at the apical surface of the cells constituting the lateral zone of gill filaments. These ectosymbionts are γ-Proteobacteria due to their strong hybridization with the specific probe GAM42; in contrast no hybridization was obtained from either gills or other host tissues by using the oligonucleotide probes specific to α- β- and δ-Proteobacteria. Based on TEM observations, these Gram-negative bacterial symbionts are not methanotrophic due to the lack of concentric stacking of intracellular membranes in their cytoplasm. Such ectosymbionts may represent thioautotrophic bacteria as already described in various Mytilidae from hydrothermal vents and cold seeps. Unfortunately, no phylogenetic analysis could be done in this study to compare their DNA sequence to that of other marine invertebrate symbionts described to date.     

New and Rare Typhloplanoid Species (Turbellaria,Neorhabdocoela) for Fauna of the Urals and Russia

Morphological decriptions and information on the biology and distribution are given for the first time for fauna of the Urals turbellarians from the Neorhabdocoela order of the Typhloplanidae family: Strongylostoma simplex Meixner 1915, Typhloplanella halleziana (Vejdovsky 1880), Phaenocora rufodorsata (Sekera 1904). The species Typhloplanella halleziana was found the first time on the territory of Russia.