Insights into the relationships of Palearctic and Nearctic lymnaeids (Mollusca : Gastropoda) by rDNA ITS-2 sequencing and phylogeny of stagnicoline intermediate host species ofFasciola hepatica

Fascioliasis by Fasciola hepatica is the vector-borne disease presenting the widest latitudinal, longitudinal and altitudinal distribution known. F. hepatica shows a great adaptation power to new environmental conditions which is the consequence of its own capacities together with the adaptation and colonization abilities of its specific vector hosts, freshwater snails of the family Lymnaeidae. Several lymnaeid species only considered as secondary contributors to the liver fluke transmission have, however, played a very important role in the geographic expansion of this disease. Many of them belong to the so-called "stagnicoline" type group. Stagnicolines have, therefore, a very important applied interest in the Holarctic region, to which they are geographically restricted. The present knowledge on the genetics of stagnicolines and on their parasite-host interrelationships is, however, far from being sufficient. The present paper analyses the relationships between Palaearctic and Nearctic stagnicoline species on the base of the new light furnished by the results obtained in nuclear rDNA ITS-2 sequencing and corresponding phylogenetic studies of the lymnaeid taxa Lymnaea (Stagnicola) occulta, L. (S.) palustris palustris (topotype specimens) and L. (S.) p. turricula from Europe. Natural infections with F. hepatica have been reported in all of them. Surprisingly, ITS-2 length and GC content of L. occulta were similar and perfectly fitted within the respective ranges known in North American stagnicolines. Nucleotide differences and genetic distances were higher between L. occulta and the other European stagnicolines than between L. occulta and the North American ones. The ITS-2 sequence of L. p. turricula from Poland differed from the other genotypes known from turricula in Europe. The phylogenetic trees using the maximum-parsimony, distance and maximum-likelihood methods confirmed (i) the inclusion of L. occulta in the branch of North American stagnicolines, (ii) the link between the North American stagnicolines-L. occulta group with Galba truncatula, and (iii) the location of the L. p. turricula genotype from Poland closer to L. p. palustris than to other European L. p. turricula genotypes. The Palaearctic species occulta is included in the genus Catascopia, together with the Nearctic species catascopium, emarginata and elodes. The results suggest a potential of transmission capacity for C. occulta higher than that of other European stagnicolines or Omphiscola glabra. The relatively low genetic distances between C. occulta and G. truncatula and the clustering of both species in the same clade suggest that C. occulta may be potentially considered as the second lymnaeid intermediate host species of F. hepatica in importance in eastern and northern Europe, and probably also western and central Asia, after G. truncatula. L. p. turricula may be considered as a potential secondary vector of F. hepatica, at a level similar to that of L. p. palustris.

Dentition of eight species of Mediterranean Sea Gobiidae: do dentition characters of gobies reflect phylogenetic relationships?

Oral and pharyngeal dentition was analysed in eight Mediterranean species of five different genera using scanning electron microscopy (SEM). Number, position, shape and size of teeth in the jaws and the pharyngeal tooth plates were used as a basis for comparison among taxa. Three different groups could be established based on the dental morphology among the species investigated and homoplasy due to feeding ecology cannot be considered the reason for similarity among them. The established groups are suggested to reflect phylogenetic relationships and correspond with the scarce published data on the topic.

European Lymnaeidae (Mollusca: Gastropoda), intermediate hosts of trematodiases, based on nuclear ribosomal DNA ITS-2 sequences

Freshwater snails of the family Lymnaeidae are of a great parasitological importance because of the very numerous helminth species they transmit, mainly trematodiases of large medical and veterinary impact. The present knowledge on the genetics of lymnaeids and on their parasite-host inter-relationships is far from being sufficient. The family is immersed in a systematic-taxonomic confusion. The necessity for a tool which enables species distinction and population characterization is evident. This paper aims to review the European Lymnaeidae basing on the second internal transcribed spacer ITS-2 of the nuclear ribosomal DNA. The ITS-2 sequences of 66 populations of 13 European and 1 North American lymnaeid species, including the five generic (or subgeneric) taxa Lymnaea sensu stricto, Stagnicola, Omphiscola, Radix and Galba, have been obtained. The ITS-2 proves to be a useful marker for resolving supraspecific, specific and population relationships in Lymnaeidae. Three different groupings according to their ITS-2 length could be distinguished: Radix and Galba may be considered the oldest taxa (370-406 bp lengths), and Lymnaea s. str., European Stagnicola and Omphiscola (468-491 bp lengths) the most recent, American Stagnicola and Hinkleyia being intermediate (434-450 bp lengths). This hypothesis agrees with the phylogeny of lymnaeids based on palaeontological data, chromosome numbers and radular dentition. ITS-2 sequences present a conserved central region flanked by two variable lateral regions corresponding to the 5' and 3' ends. The number of repeats of two microsatellites found in this conserved central region allows to differentiate Radix from all other lymnaeids. Phylogenetic trees showed four clades: (A) Lymnaea s. str., European Stagnicola and Omphiscola; (B) Radix species; (C) Galba truncatula; and (D) North American stagnicolines. ITS-2 results suggest that retaining Stagnicola as a subgenus of Lymnaea may be the most appropriate and that genus status for Omphiscola is justified. Radix shows a complexity suggesting different evolutionary lines, whereas G. truncatula appears to be very homogeneous. North American and European stagnicolines do not belong to the same supraspecific taxon; the genus Hinkleyia may be used for the American stagnicolines. Genetic distances and sequence differences allowed us to distinguish the upper limit to be expected within a single species and to how different sister species may be. S. palustris, S. fuscus and S. corvus proved to be valid species, but S. turricula may not be considered a species independent from S. palustris. Marked nucleotide divergences and genetic distances detected between different S. fuscus populations may be interpreted as a process of geographic differentiation developping in the present. Among Radix, six valid species could be distinguished: R. auricularia, R. ampla, R. peregra (=R. ovata;=R. balthica), R. labiata, R. lagotis and Radix sp. The information which the ITS-2 marker furnishes is of applied interest concerning the molluscan host specificity of the different trematode species. The phylogenetic trees inferred from the ITS-2 sequences are able to differentiate between lymnaeids transmitting and those non-transmitting fasciolids, as well as between those transmitting F. hepatica and those transmitting F. gigantica. The Fasciola specificity is linked to the two oldest genera which moreover cluster together in the phylogenetic trees, suggesting an origin of the Fasciola ancestors related to the origin of this branch. European Trichobilharzia species causing human dermatitis are transmitted only by lymnaeids of the Radix and Lymnaea s. str.-Stagnicola groups. Results suggest the convenience of reinvestigating compatibility differences after accurate lymnaeid species classification by ITS-2 sequencing. Similarly, ITS-2 sequencing would allow a step forward in the appropriate rearrangement of the actual systematic confusion among echinostomatids.

Motility of spermatozoa ofAlburnus alburnus (Cyprinidae) and its relationship to seminal plasma composition and sperm metabolism

The composition of seminal plasma and metabolism of sperm of the cyprinid fishAlburnus alburnus were investigated. Statistically significant correlations were found between motility parameters and seminal fluid osmolality, pH, Na(+), K(+) and protein levels (negative correlations: % immotile spermatozoa-Na(+), K(+); positive correlations: % motile spermatozoa-osmolality, pH, Na(+), K(+), protein; % linear motile spermatozoa-pH protein; swimming velocity of spermatozoa-pH, Na(+), protein). Spermatozoan motility and ATP metabolism and glycolysis were correlated as indicated by measurement of ATPase, pyruvate kinase, adenylate kinase and lactate dehydrogenase activity. The physiological meanings of these correlations and their possible significance for quality control of semen are discussed.

Composition of the ovarian fluid in 4 salmonid species: Oncorhynchus mykiss, Salmo trutta f lacustris, Salvelinus alpinus and Hucho hucho

The ovarian fluid of rainbow trout (Oncorhynchus mykiss), charr (Salvelinus alpinus), lake trout (Salmo trutta f lacustris) and Danube salmon (Hucho hucho) was analyzed for its inorganic and organic composition. The qualitative composition of the ovarian fluid of the investigated species was similar, but significant quantitative differences were found. The following components were determined: sodium 106.6-142.2 mmol/l, potassium 1.7-2.7 mmol/l, calcium 0.45-0.61 mmol/l, osmolality 256.4-291.6 mosmol/kg, pH 8.4-8.8, glucose 1,698-4,195 mumol/l, fructose 17-399 mumol/l, lactate 34-227 mumol/l, cholesterol 650-1,230 mumol/l, phosphatidylcholine 0.25-3.0 mumol/l, lysophosphatidylcholine 10-100 mumol/l, choline 0-1.1 mumol/l, protein 95.0-278.4 mg/100 ml. Arginine, cystine, glycine, histidine, lysine, proline, serine, tyrosine and valine were the free amino acids occurring in concentrations of more than 10 mumol/l. Activities of alkaline phosphatase (200-6,000 mumol substrate/l/h), lactate dehydrogenase (9-690 mumol substrate/l/h), beta-D-glucuronidase (70-410 mumol substrate/l/h), proteases (140-215 mumol/l/h with collagen substrate, 25-90 mumol/h/l with gelatine substrate) and acid phosphatase (100-130 mumol substrate/l/h) were measured, but not the glucose-6-phosphate dehydrogenase and alpha-glucosidases activities.

Energy resources of spermatozoa of the rainbow trout Oncorhynchus mykiss (Pisces, Teleostei)

Spermatozoa of Oncorhynchus mykiss have the enzymatic capacity for glycolysis, for triglyceride and phospholipid catabolism and triglyceride synthesis. They lack glucosidase activity and are therefore not able to utilize polysaccharides as energy resources. In motile spermatozoa glycolysis occurs during the first 30 s of motility and--when motility is initiated in a physiological saline solution--triglyceride catabolism is used for the regeneration of ATP levels after motility has ended. When immotile spermatozoa are incubated with the seminal plasma or in physiological saline solution they behave similarly as regards utilization of their primary energy reserves: glycolysis as well as catabolism of triglycerides occurs. In approximately 60% of the semen samples, spermatozoa synthesize triglycerides at the onset of incubation. Possible physiological reasons for triglyceride synthesis have been discussed.

Monosaccharides as energy resources during motility of spermatozoa in Leuciscus cephalus (Cyprinidae, Teleostei)

Spermatozoa of Leuciscus cephalus have the enzymatic outfit for glycolysis but lack lipase, phospholipase and glucosidase activities. Therefore, they are not able to utilize lipids and polysaccharides as energy resources. During motility they use monosaccharides as energy reservoirs: the intracellular glucose, galactose and fructose levels decrease significantly while lactate levels increase.

Vascularization of male gonads in Blennius pavo (Teleostei, Blenniidae) as revealed by scanning electron microscopy of vascular corrosion casts

The vascular architecture of male gonads of Blennius pavo is studied by scanning electron microscopy of vascular corrosion casts. Arterial supply to the gonads is by a branch of the first ventral segmental artery of the tail. From the surface of the gonads, this vessel gives rise to branches which supply testes, spermatic ducts, testicular glands, blind pouches, urogenital sinus and urogenital papilla. The testis has a rope-ladder-like capillary network around the seminiferous tubules, while in the testicular gland the capillary network is irregular in form. The spermatic ducts are found to have an exterior capillary network located in the compact connective tissue layer and an interior one, lying subepithelially. Urogenital sinus and urogenital papilla show a multilayered capillary network. Angioarchitecture in mature and immature gonads does not differ.

FMRF-amide-like immunoreactivity in brain and pituitary of the hagfish Eptatretus burgeri (Cyclostomata)

Paraffin sections of brain and pituitary of the hagfish Eptatretus burgeri were immunostained with an antiserum to FMRF-amide. Immunoreactivity was visible in a large number of neurons in the posterior part of the ventromedial hypothalamus and in long neuronal processes extending cranially from the hypothalamus to the olfactory system and caudally to the medulla oblongata. FMRF-amide-like immunoreactivity was also found in cells of the adenohypophysis. These observations suggest that the hagfish possesses a brain FMRF-amide-like transmitter system and pituitary cells containing FMRF-amide-like material. Antisera to ACTH, alpha-MSH and pancreatic polypeptide gave no immunoreaction in hagfish brain or pituitary.

[Comparative histology and electron microscopy study of intestinal anastomosis by invagination and by single layer inverted suture]

In the experiment, the technique of anastomosis by means of invagination proves to be a most effective method of joining two parts of the colon. Both histology and the electronic microscope verified the exact conjunction of the different layers.

Cell types in the adenohypophysis of the hagfish, Myxine glutinosa (Cyclostomata)

The anterior pituitary of the Atlantic hagfish, Myxine glutinosa, was investigated by transmission electron microscopy. The cells of the adenohypophysis are arranged in follicles surrounded by connective tissue. Five cell types containing granules and one agranular cell type were identified. At the present state of the study the function of these cells remains open to discussion.