A field test of a sediment bioassay with the oligochaete worm Tubifex tubifex (Müller, 1774)

A sediment toxicity test using reproduction in the tubificid oligochaete Tubifex tubifex was tested in 11 geographic locations in the Laurentian Great Lakes where sediments have previously been documented as being contaminated. Samples were taken from both potentially contaminated and clean sites in each of the 11 areas. Using test endpoints such as survival and growth, results from 72 samples were classified using cluster and ordination techniques. Six response groups were identified and four groups of toxic sites determined. Toxic effects ranged from mortality of adult worms to reduced reproduction. Using correlation and discriminant analysis there was good evidence that high concentrations of metals such as copper and lead were responsible for the observed effects at some sites.     

Possible sites of ultrafiltration in Tubifex tubifex Müller (Annelida,Oligochaeta)

Summary The endothelia of Tubifex tubifex Müller consist of myoendothelial cells, chloragocytes, or podocytes. The latter seem to occur only as windows on the ventral vessel which has an endothelium of myoendothelial cells elsewhere. The podocytes are large cells, with several processes on the inner side which ramify into several pedicels. These are aligned upon the outside of the basement membrane which lines the inside of the endothelium. The gaps between adjacent pedicels are about 40 nm wide. In capillaries fenestrated endothelia occur with irregular spacings measuring up to 0.4–1 m. A diaphragm in podocytes or capillary fenestrations do not seem to exist. The basement membrane is the only continuous layer lining the blood vessels and capillaries of Tubifex with a rather uniform diameter in the range of 50 nm. It is the only permeability barrier between blood and coelomic fluid.     

Some characteristics of genetic variants of Tubifex tubifex (Müller, 1774) (Oligochaeta: Tubificidae) in laboratory cultures

Genetic variants of the oligochaete Tubifex tubifex were identified with enzyme electrophoresis and subsequently reared in laboratory cultures. Three types are abundant in field populations. Individuals that show homozygotic bands of glucosephosphate-isomerase (GPI) 22 together with isocitrate-dehydrogenase (IDH) 35 were labeled Type A. Type B is characterized by GPI 23 together with IDH 11 and Type C is characterized by GPI 11 with either IDH 34 or IDH 33. Initial results on freshweights of adults and cocoon production revealed differences between the two main types, A and B. In the same period, Type B reached higher weights and produced five times as many cocoons as Type A, whereas number of eggs per cocoon were not different between these Types. Type B also had the lowest mortality in 16-week experiments with changing temperatures.     

Screening the Toxicity of Ni,Cd, Cu,Ivermectin, and Imidacloprid in a Short-Term Automated Behavioral Toxicity Test with Tubifex tubifex (Müller 1774) (Oligochaeta)

A new automated online toxicity test for screening of short-term effects of chemicals is presented using the freshwater oligochaete Tubifex tubifex in the Multispecies Freshwater Biomonitor? (MFB). Survival and locomotory behavior of the worms were observed during 24 h of exposure to metals (Cd, Cu, Ni), pesticides (Imidacloprid), and pharmaceuticals (Ivermectin). The LC₅₀ values revealed increasing toxicity in the following order: Ni (> 100 mg/l) < Cu (15.2 mg/l) < Cd (4.9 mg/l) < Ivermectin (1.8 mg/l) < Imidacloprid (0.3 mg/l). The EC₅₀ for locomotion showed a similar order of increasing toxicity: Ni (86 mg/l) < Cu (3.8 mg/l) < Ivermectin (2.0 mg/l) < Cd (1.1 mg/l) < Imidacloprid (0.09 mg/l). Toxicity was dependent on both concentration and exposure time. This could be demonstrated in 3d response models and proven in the statistical analysis showing a significant interaction term (C × T) for the experiments with Cu and Ni. T. tubifex proved to be very tolerant, but even then behavioral responses were more sensitive than mortality for Cu, Cd, and Imidacloprid.     

Factors affecting feeding rate, reproduction and growth of an oligochaete Lumbriculus variegatus (Müller)

Worm density of a deposit feeding oligochaete (Lumbriculus variegatus) did not affect egestion whereas both temperature and sediment type had a significant influence. The worms egested less actively at the lowest temperature (6 °C). The egestion rate, expressed as mg dry feces produced, was highest in the sandy sediment and lowest in the sediment derived almost exclusively from decaying plant material. The amount of dry material and the volume of wet sediment passing through the worms varied between the test sediments; the results are probably dependent on the chosen unit of measure. Reproduction was significantly decreased in sandy sediment with low organic carbon content. Reproduction was also dependent on the worm size, larger worms reproducing more frequently. Most worms lost weight during the tests, but the loss was lowest in the sediment with the highest organic carbon content. This revised version was published online in July 2006 with corrections to the Cover Date.     

Allozyme variation in the camaenid tree snails Amphidromus atricallosus (Gould, 1843) and A. inversus (Müller, 1774)

We examined allozyme variation in two camaenid tree snails, Amphidromus atricallosus and A. inversus, across two principal regions of Thailand and from Singapore, plus for A. inversus, one site in peninsular Malaysia. Using horizontal starch gel electrophoresis, 13 allozyme loci (11 polymorphic) were screened for A. atricallosus and 18 (5 polymorphic) for A. inversus. Heterozygosity was higher in A. atricallosus (Hexp=0.018-0.201, mean=0.085) than in A. inversus (Hexp=0-0.023, mean= 0.002). Genetic heterogeneity among samples was higher in A. inversus (Fst=0.965) than in A. atricallosus (Fst=0.781). Within A. atricallosus, populations were more differentiated in southern Thailand (Fst=0.551) than in eastern Thailand (Fst=0.144). The high Fst and low Hexp in populations of A. inversus suggest that this species is likely to have experienced a series of strong bottlenecks, perhaps occurring chiefly on offshore continental-shelf islands. The low Fst values of A. atricallosus in eastern Thailand suggest frequent gene flows among populations in this region. The southern and eastern samples of A. atricallosus exhibited fixed allele differences at four loci and great genetic distance (Nei's D=0.485-0.946), suggesting that these two samples may actually represent, or else be evolving into, separate species.     

Quantification of sediment reworking by the Asiatic clam Corbicula fluminea Müller, 1774

Active organisms modify the substratum in which they dwell. This process, called “bioturbation”, affects the way that biogeochemical fluxes are mediated at the substratum–water interface. In the frame of this work, the bioturbation potential of the Asiatic clam Corbicula fluminea was characterized and quantified. We measured the displacement of fluorescent particles by C. fluminea burying in a size-based experimental design in order to explore the effects of body-size on sediment reworking. Our results stress that C. fluminea belongs to the functional group of biodiffusors, and that C. fluminea can be considered as an intermediate sediment reworker. We suggest that bioturbation was mainly induced by the pedal-feeding activity of the clams. Results also showed that, though large clams induced displacement of particles deeper into the sediment, small clams showed the highest net sediment reworking activity. This result was in contrast to the initial hypothesis of biovolume as the main driver for particle displacement by bioturbating organisms. Life-history traits and specific features of pedal-feeding could explain the observed pattern.     

Reproduction, growth and circadian activity of the snail Bradybaena fruticum (O. F. Müller, 1774) (Gastropoda: Pulmonata: Bradybaenidae) in the laboratory

Selected life cycle parameters of the snail Bradybaena fruticum were studied in the laboratory. The initial material for the laboratory culture was taken from a population in South Western Poland; the snails were kept in Petri dishes and plastic containers. The temperature, humidity and lighting conditions were maintained at a constant level (day 18°C, night 12°C, rh 80%, light:dark 12:12). Circadian activity observations were conducted outside the climatic chamber. Eggs — calcified, slightly oval, of mean dimensions 2.67x2.56 mm — were laid singly or in batches of 6–62, as a result of both biparental and uniparental reproduction. Incubation took 27–76 days and hatching was asynchronous. Hatching success was lower among eggs produced by single parents compared to eggs produced by two parents (c.a. 56 and c.a. 88%, respectively). Growth included fast (2.25 to 5 whorls) and slow (1.9–2.25 and >5 whorls) phases as well as lip formation, and took 261 to 420 days. The first eggs/batches were laid c.a. one year later, and for uniparentally reproducing snails the period was even longer. The growth of snails kept singly was faster than in those kept in groups. Juvenile snails were much more active than adults in the spring, summer and autumn but the adults were more mobile in the winter. In all seasons, juveniles were more active at night than adults.     

Life cycle and identification of an eyefluke from Israel transmitted by Melanoides tuberculata (Müller, 1774)

A philophthalmid species from Israel using the freshwater snail Melanoides tuberculata as intermediate host was studied. The biological and morphological characteristics of all developmental stages of the life cycle of this philophthalmid were described, and compared to those of Philophthalmus lucipetus Rudolphi, 1819 from Israel, Philophthalmus gralli Mathis and Leger, 1910 from Jordan, Philophthalmus palpebrarum Looss, 1899, Philophthalmus nocturnus Looss, 1907, Cercaria distomatosa Looss 1896 from Egypt, and Philophthalmus lucknowensis Baugh, 1962 from India. The possible identity with 1 of these species is discussed. On the basis of comparative analysis of the data for all parasite stages in the life cycle, geographical distribution, snail hosts, and snail host specificity, we propose to designate the Israeli Melanoides tuberculata-transmitted eye fluke to Philophthalmus distomatosa n. comb. (Looss, 1896), (Digenea: Philophthalmidae).     

Micro-structure and chemical composition of vateritic deformities occurring in the bivalve Corbicula fluminea (Müller, 1774)

Vateritic deformities occurring in the invasive heterodont bivalve Corbicula fluminea from several locations in the UK were characterised in detail for the first time using scanning electron microscopy, X-ray diffraction and different geochemical techniques (electron microprobe, ICP-AES, and mass spectrometry). Large volumes of vaterite are produced abnormally in the animals' shells in the form of yellow-green bulges. These are distinguished from the aragonitic parts of the shell by their characteristic micro-structures, content of organic material, trace elemental composition and carbon stable isotope signatures. The most commonly observed micro-structures include columnar vaterite, lamellar vaterite and different irregular structures occurring in all parts of the shell. There are indications that organic material is present largely as intracrystalline impurities or nano-scale phases and not as envelopes around microstructural units. These micro-structures are novel, nothing equivalent having yet been described for other vateritic systems. Euhedral vaterite crystals also occur occasionally. The vaterite has generally higher Mg/Ca and lower Na/Ca, K/Ca than the aragonite. In addition, δ13C is also always lower. Microstructural characteristics would suggest loss of biological control probably due to physiological stress(es) inducing the switch to vaterite production. The vaterite might be stabilised by its higher content of organic material and magnesium.     

Purification and properties of beta-N-acetylhexosaminidase from the mollusc Helicella ericetorum Müller.

1. A beta-N-acetylhexosaminidase was purified 330-fold from the digestive gland of the terrestrial mollusc Helicella ericetorum Müller. 2. Its pH optimum is 4.5 for both beta-N-acetylglucosaminidase and beta-N-acetylgalactosaminidase activities in two buffer solutions; it is fully stable at 37 degrees C for 2h in the pH range 3.8--4.6 and shows one isoelectric point (pH 4.83). 3. The estimated mol.wt. is between 120,000 and 145,000. 4. The enzyme shows an endo-beta-N-acetylhexosaminidase activity on natural substrates such as ovalbumin, ovomucoid, chondroitin 4-sulphate, chitin and hyaluronic acid. 5. Two forms of the enzyme were separated by preparative polyacrylamide-gel electrophoresis. 6. Km and Vmax. for p-nitrophenyl 2-acetamido-2-deoxy-beta-D-glucopyranoside and p-nitrophenyl 2-acetamide-2-deoxy-beta-D-galactopyranoside are 0.43 mM, 30.1 micronmol of p-nitrophenol/min per mg and 0.19 mM, 8.6 micronmol of p-nitrophenol/min per mg respectively. 7. It is inhibited by Hg2+, Fe3+, acetate, some lactones, N-acetylgalactosamine, N-acetylglucosamine and mannose. 8. Mixed-substrates analysis and Ki values for competitive inhibitors indicated that beta-N-acetylglucosaminidase and beta-N-acetylgalactosaminidase activities are catalysed by the enzyme at the same active site.     

Comparison of fatty acids and some mineral matter profiles of wild and farmed snails,Cornu aspersum Müller, 1774

ABSTRACT

The fatty acid and mineral matter compositions of the visceral mass and pedal mass of wild and farmed Cornu aspersum were compared. The relative fatty acid amounts of the visceral and pedal masses of wild and farmed snails are: polyunsaturated fatty acid (PUFA) > saturated fatty acid (SFA) > monounsaturated fatty acid (MUFA), PUFA?>?SFA?>?MUFA, MUFA?>?PUFA?>?SFA and PUFA?>?MUFA?>?SFA, respectively. Wild snails had a higher concentration of iron and zinc than farmed snails. Selenium was 2.82 times higher in the pedal mass of farmed snails than the pedal mass of wild snails. Ca:P ratios in the visceral mass of wild snails, visceral mass and pedal mass of farmed snails were 1.76:1, 1.12:1 and 3.87:1 respectively. Both wild and farmed snails have high contents of oleic, linoleic, eicosapentaenoic and docosahexaenoic fatty acids and are a good source of minerals. Careful attention should be paid, however, as to which diet will be used during farming because the composition of fatty acid in the snail is affected by diet.     

Morphological study of muscular tissue collagen of wild and reared Cornu aspersum (Müller, 1774)

Muscular tissue collagen fibrils’ diameter and period of reared and wild snails (Cornu aspersum) were measured in order to investigate the role of nutrition on the collagen. Wild adult individuals were collected from Crete (Greece) and compared with adult individual snails reared under laboratory conditions fed a formulated diet. Transmission electron microscope and image analysis algorithms were used in the study. Statistically significant differences between the diameters of the collagen fibrils in the reared and the wild snails were found, and the D-period of the fibrils differed.     

Comparison of morphological characters in Irish and English populations of the acanthocephalan Pomphorhynchus laevis (Müller, 1776)

Pomphorhynchus laevis is believed on ecological evidence to exist as three strains in the British Isles. However, the strains have never been shown to be capable of being distinguished using morphological characters. A morphological comparison was made between a sample of P. laevis from Salmo trutta in L. Feeagh in the west of Ireland and a sample from Leuciscus cephalus in R. Culm in the south of England. The length and width of the trunk, neck, bulb, proboscis and hooks were measured. The number of hooks per row, the number of rows and the positions of the stoutest and longest hooks were also recorded. A Principal Components Analysis based on the morphological measurements confirmed the separation of the two populations and showed that two characters successfully identified the populations: the position of the stoutest hook and the ratio of numbers of anterior to posterior hooks.     

Biological studies and phenology of the slug Deroceras reticulatum (Müller, 1774) (Pulmonata: Stylommatophora)

Summary

In the southeast of Buenos Aires Province (Argentina), slugs cause reductions in crop yield by killing seeds and seedlings, by destroying stems and growing points, and by reducing leaf area. Deroceras reticulatum (Müller, 1774) was introduced into Argentina a long time ago, but the biology and ecology of this species in this country are still unknown. The aim of this study was to determine how temperature affects growth rate, reproduction and survival of D. reticulatum and also to assess the seasonal phenology of this species. The life cycle of D. reticulatum was investigated at 12°C, 20°C and at a temperature which alternated between 12°C for 16 h and 20°C for 8 h. The light/dark regime during the experiment was LD: 8/16 h. Slug populations were sampled from grassland located at the Experimental Station of INTA Balcarce. Eggs hatched after 16.3 to 39.8 days and fertility varied between 83.9% and 91.1%. The mean time from hatching to oviposition was longer and fecundity lower at 20°C than 12°C and 12/20°C (p <0.05). The net reproductive rate was 1.49 to 70.53 and the mean generation time varied between the 27 and 30 weeks. In natural conditions, eggs of D. reticulatum were found from early winter until the end of the spring, when soil temperature was 8–15°C and humidity was above 15%. These results indicate that D. reticulatum has one generation per year, univoltine phenology, with peak densities of slugs from the beginning of winter to the end of spring, which coincides with the sowing and emergence of winter and summer crops.     

Habitat preference of freshwater snails in relation to environmental factors and the presence of the competitor snail Melanoides tuberculatus (Müller, 1774)

Our objective is to evaluate the habitat preference of freshwater snails in relation to environmental factors and the presence of the competitor snail Melanoides tuberculatus. In the first phase, snails was collected at 12 sites. This sampling sites presented a degree of organic input. In the second phase 33 sampling sites were chosen, covering a variety of lotic and lentic environments. The snail species found at Guapimirim, state of Rio de Janeiro, displayed a marked habitat preference, specially in relation to the physical characteristics of each environment. Other limiting factors for snail distribution at the studied lotic environments were the water current velocity and the amount of organic matter, mainly to Physa marmorata, M. tuberculatus, and Biomphalaria tenagophila. The absence of interactions between M. tuberculatus and another snails could be associated to the distinct spatial distribution of those species and the instability of habitats. This later factor may favor the coexistence of M. tuberculatus with B. glabrata by reduction of population density. In areas of schistosomiasis transmission some habitat modification may add to the instability of the environment, which would make room for the coexistence of M. tuberculatus and Biomphalaria spp. In this way, some of the usual measures for the control of snail hosts would prevent the extinction of populations of Biomphalaria spp. by M. tuberculatus in particular habitats.     

Biology of Pseudopotamilla reniformis (Müller 1771) in the White Sea,with description of asexual reproduction

The tube-dwelling polychaete Pseudopotamilla reniformis (Sabellidae) forms dense and complex aggregations of flexible tubes on hard substrates in the subtidal zone of the White Sea. No sexual reproduction was observed in this study and recruitment appeared to be due to asexual reproduction by architomy in winter, from October to March. The posterior part of the abdomen undergoes spontaneous fission into from 2 to 4 fragments and depending on their position, the fragments regenerate their anterior ends or both anterior and posterior ends. Regeneration in P. reniformis takes place via a combination of epimorphosis (replacement of missing parts by cell proliferation and the growth of new tissue) and morphallaxis (the remodelling of pre-existing structures without cell proliferation). The morphogenetic events during regenerative restoration include de novo formation of branchial crown, formation of thoracic segments and restoration of the posterior end. Asexual reproduction appears to play a crucial role for formation of P. reniformis aggregations and is very important for the population in the White Sea, at the margin of the species’ range.     

Effect of reproduction on escape responses and muscle metabolic capacities in the scallop Chlamys islandica Müller 1776

In scallops, gametogenesis leads to mobilization of glycogen and proteins from the adductor muscle towards the gonad. This mobilization is likely to diminish the metabolic capacities of the adductor muscle and thereby the scallops' escape response. We examined the escape response in terms of number of valve claps until exhaustion, rate of clapping and the recovery during and after valve closure in adult scallops, Chlamys islandica, sampled at different stages in the reproductive cycle (immature, mature, before and after spawning). In parallel, we measured muscle glycogen, protein and phosphoarginine contents, the oxidative capacity of mitochondria isolated from the adductor muscle and levels of muscle enzymes which are active during exercise and recovery. The number of claps (24-26), rate of clapping ( approximately 13 clapsmin(-1)) and phosphoarginine and arginine kinase levels were similar during the different reproductive stages. All immature scallops responded to restimulation immediately after opening their valves, while only 62% of mature, 82% of prespawned and 38% of spawned scallops responded. Immature animals completely recovered their initial swimming capacity within 4 h of opening their valves, but mature, prespawned and spawned scallops needed 18, 12 and 18 h, respectively. Overall phasic adductor muscle from mature, prespawned and spawned animals showed decreased glycogen phosphorylase, phosphofructokinase, pyruvate kinase (except for prespawned), octopine dehydrogenase and citrate synthase levels, a deterioration of the oxidative capacity of mitochondria and a marked decrease in glycogen content compared to immature scallops. Therefore, during gonadal maturation and spawning, C. islandica did not change its clapping capacity, but slowed its recuperation from exhausting burst exercise, both during and after valve closure, likely due to the decreased metabolic capacity of the adductor muscle.