Previously unknown apicomplexan species infecting Iceland scallop, Chlamys islandica (Müller, 1776), queen scallop, Aequipecten opercularis L., and king scallop, Pecten maximus L

Examination of three scallop species from three separate locations: Iceland scallop from Icelandic waters, king scallop from Scottish waters and queen scallop from Faroese and Scottish waters, revealed infections of a previously unknown apicomplexan parasite in all three scallop species. Developmental forms observed in the shells appeared to include both sexual and asexual stages of the parasite, i.e. merogony, gametogony and sporogony, which suggests a monoxenous life cycle. Meronts, gamonts, zygotes and mature oocysts were solely found in the muscular tissue. Zoites, which could be sporozoites and/or merozoites, were observed in great numbers, most frequently in muscles, both intracellular and free in the extracellular space. Zoites were also common inside haemocytes. Examination of the ultrastructure showed that the zoites contained all the major structures characterizing apicomplexans. This apicomplexan parasite is morphologically different from other apicomplexan species previously described from bivalves. Presently, its systematic position within the phylum Apicomplexa cannot be ascertained.     

Age-specific residual reproductive value and reproductive effort in the Iceland scallop,Chlamys islandica (O.F. Müller)

Summary The possibility for a trade-off between age-specific residual reproductive value (RRV) and reproductive effort (RE) was investigated. Different ways of estimating RE did not affect conclusions which were: a) there is no clear trade-off between RRV and RE until the scallop has reached an age of about 13 years, i.e. after a reproductive life of about eight years; b) the larva of C. islandica is more important as a means of dispersal than as a means of maintaining the parent population.     

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.     

A chromosome study ofSchistocephalus solidus (Müller, 1776) (Cestoda: Pseudophyllidea)

Analysis of Giemsa-stained metaphase plates of plerocercoids ofSchistocephalus solidus revealed the mode diploid number of chromosomes for this species as 2n=18. Chromosome pairs 1, 5, 6, 8 and 9 are metacentric, pairs 2, 4 and 7 are subtelocentric, and pair 3 is subtelocentric to acrocentric. The karyotype is characterised by mean absolute chromosome length between 1.9 and 5.9 m and a total chromosome length of the haploid complement of 32 m. A comparison with other known karyotypes of related species of pseudophyllidean cestodes was made.     

Description of Ulvella elegans sp. nov. and U. islandica sp. nov. (Ulvellaceae,Ulvophyceae) from Iceland – a study based on morphology of species in culture and tufA gene sequences

Two new Ulvella species, U. elegans R. Nielsen & K. Gunnarsson and U. islandica R. Nielsen & K. Gunnarsson are described. These microfilamentous marine green algae were found in the sublittoral zone in northern Iceland, epiphytic on Euthora cristata and associated with a calcareous polychaete tube, respectively. Unialgal cultures were established from field-collected material for morphological observations. In culture, Ulvella elegans was characterized by rosettes of monostromatic pseudoparenchyma consisting of radiating filaments with a margin of mutually free filaments. Each cell had one pyrenoid. Hairs were not observed. Ulvella islandica had a heterotrichous morphology, consisting of dense tufts of upright broad branches and much narrower, rhizoid-like branches. Acrochaete-type hairs occurred; these are hyaline non-septate merocytic extensions from a more or less bulbous base, which may be separated from the vegetative cell below. Most cells had one pyrenoid except for a few broad cells which had two or three. In a phylogenetic reconstruction based on the chloroplast-encoded tufA gene, the sequences for the two species were clearly distinct from any other Ulvella sequence available for this gene. Ulvella islandica was placed in a clade together with U. lens, U. wittrockii, U. reticulata and U. pseudorepens. Ulvella elegans occupied a branch deep in the phylogeny but the position was poorly supported.     

Anatomical variability and secondary sexual characteristics in Pomphorhynchus laevis (Müller, 1776) (Acanthocephala)

A brief historical survey demonstrates the differences in opinion concerning the taxonomic status of species within the genus Pomphorhynchus. The anatomy of P. laevis from a single population in the River Severn, England was found to be highly variable. Much of this variability is produced as individuals grow. P. laevis possesses circumbursal and circumpenial rings of receptors on the male copulatory bursa. Specimens from Eire and the R. Severn had identical arrangements of these receptors. A preliminary appraisal of the value of secondary sexual characters as criteria of specific identity in the Acanthocephala is presented. ac]19860721     

New insights on ctenophore neural anatomy: immunofluorescence study in Pleurobrachia pileus (Müller, 1776)

Ctenophores are non-bilaterian animals sharing with cnidarians and bilaterians the presence of sensory receptors, nerve cells, and synapses, absent in placozoans and sponges. Although recent immunofluorescence studies have renewed our knowledge of cnidarian neuro-anatomy, ctenophores have been much less investigated despite their importance to understanding the origin and early evolution of the nervous system. In this study, the neuro-anatomy of the ctenophore Pleurobrachia pileus (Müller, 1776) was explored by whole-mount fluorescent antibody staining using antibodies against tyrosylated -tubulin, FMRFamide, and vasopressin. We describe the morphology of nerve nets and their local specializations, and the organization of the aboral neuro-sensory complex comprising the apical organ and polar fields. Two distinct nerve nets are distinguished: a mesogleal nerve net, loosely organized throughout body mesoglea, and a much more compact “nerve net” with polygonal meshes in the ectodermal epithelium. The latter is organized as a plexus of short nerve cords. This epithelial nervous system contains distinct sub-populations of dispersed FMRFamide and vasopressin immunoreactive nerve cells. In the aboral neuro-sensory complex, our most significant observations include specialized nerve nets underlying the apical organ and polar fields, a tangential bundle of actin-rich fibers (interpreted as a muscle) within the polar fields, and distinct groups of neurons labeled by anti-FMRFamide and anti-vasopressin antibodies, within the apical organ floor. These results are discussed in a comparative perspective.     

A cytogenetics study of Hydrodroma despiciens (Müller, 1776) (Acari: Hydrachnellae: Hydrodromidae)

The karyotypes of water mites (Acari: Hydrachnellae: Hydrodromidae) are largely unknown. The present investigation is the first report of a study designed to characterize the chromosomes of water mites. The study was carried out with specimens of Hydrodroma despiciens collected from Eber Lake in Afyon, Turkey. Several different methods were tried to obtain chromosomes of this species. However, somatic cell culture proved to be the most effective for the preparation of chromosomes. In the present study, we determined the diploid chromosome number of Hydrodroma despiciens to be 2n = 16. However, a large metacentric chromosome was found in each metaphase, which we believed to be the X chromosome. We could not determine the sex chromosomes of this species. This study is the first approach to the cytogenetic characterization of this water mite group. Furthermore, these cytogenetic data will contribute to the understanding of the phylogenetic relationship among water mites. To our knowledge, this is the first report on the cytogenetics of water mites.     

Spermatological characters of the pseudophyllidean cestode Bothriocephalus scorpii (Müller, 1776)

Spermiogenesis of Bothriocephalus scorpii (Cestoda, Pseudophyllidea) includes an orthogonal development of two flagella, followed by a flagellar rotation and a proximo-distal fusion with the median cytoplasmic process. The fusion occurs at the level of four attachment zones. The presence of dense material in the apical region of the differentiation zone in the early stage of spermiogenesis appears to be a characteristic feature for the Pseudophyllidea. The mature spermatozoon possesses two axonemes of 9+"1" pattern of the Trepaxonemata, nucleus, cortical microtubules, electron-dense granules and crested body. The anterior part of the gamete exhibits a centriole surrounded by electron-dense tubular structures arranged as incomplete spiral. When the crested body disappears, the electron-dense tubular structures are arranged into a ring encircling the axoneme. The electron-dense tubular structures and their arrangement appear to be a specific feature for the clade "Bothriocephalidea". The organization of the posterior extremity of the gamete with the nucleus is described for the first time in the Pseudophyllidea.     

An alternative mode of larval development inScoloplos armiger (O. F. Müller, 1776) (Polychaeta,Orbiniidae)

During a three-year plankton monitoring at the island of Helgoland (German Bight, North Sea), pelagic larvae ofScoloplos armiger (O. F. Müller, 1776) were observed to occur regularly from February to April. Up to the present day, only benthic development within egg cocoons has been described (Anderson, 1959). Planktonic larvae comprise early, ovoid trochophores up to advanced stages with 11 setigers. The main morphological difference between the two larval types is the more numerous differentiation of lateral cilia by the pelagic larvae. Annual alterations in appearance and abundance suggest that reproduction is correlated with water temperature.     

Feeding ecology of capelin (Mallotus villosus Müller) in West Greenland waters

Capelin (Mallotus villosus Müller) is a key pelagic mediator of energy from lower to higher trophic levels in arctic waters. This is also the case in Greenland waters, but little is known of its feeding behaviour in this region. By analysing stable nitrogen isotopes and stomach content of capelin collected along 1500?km of the Greenland west coast, this study aims to provide knowledge on capelin feeding ecology and the role that diet composition and biomass may have in generating the observed latitudinal growth differences in Greenland capelin. In total, 572 stomachs were sampled. The most dominant prey by wet weight was euphausiids (61?%) followed by amphipods (18?%) and copepods (10?%). The most common species were Thysanoessa raschii, Themisto libulla, Calanus finmarchicus and Calanus hyperboreus. Copepods dominated in smaller capelin but were replaced by euphausiids in larger fish. A similar prey shift towards euphausiids along with an increase in prey weight (relative and absolute) was seen with increasing latitude. The spatial variation in feeding pattern was supported by stable nitrogen analyses. The mean δ¹⁵N values of capelin muscle tissue for the south (60–64°N) and north (68–72°N) were 9.54?‰?±?0.72 and 12.47?‰?±?0.38 (mean?±?SD), respectively. However, when differences in isotopic baseline values (C. finmarchicus δ¹⁵N, 2.47?‰) in the two areas were taken into account, the isotope values suggest that capelin in the northern areas fed on a slightly higher trophic level higher than in the south, as would be expected with increasing importance of euphausiids. These significant feeding differences along the Greenland west coast are likely impacting capelin growth and condition as they show parallel trends along the same gradient.     

General morphology and ultrastructure of the radula of Testudinalia testudinalis (O. F. Müller, 1776) (Patellogastropoda,Gastropoda)

The radular morphology of the patellid species Testudinalia testudinalis (O. F. Müller, 1776) from the White Sea was studied using light, electron, and confocal microscopy. The radula is of the docoglossan type with four teeth per row and consisting of six zones. We characterize teeth formation in T. testidinalis as follows: one tooth is formed by numerous and extremely narrow odontoblasts through apocrine secretion; this initially formed tooth consists of numerous vesicles; the synthetic apparatus of the odontoblasts is localized in the apical and central parts of the cells throughout the cytoplasm and is penetrated by microtubules which are involved in the transport of the synthesized products to the apical part of the odontoblast; the newly formed teeth consist of unpolymerized chitin. Mitotic activity is located in the lateral parts of the formation zone. The first four rows contain an irregular arrangement of teeth, but the radular teeth are regularly arranged after the fifth row. The irregularly arranged teeth early on could be a consequence of the asynchronous formation of teeth and the distance between the odontoblasts and the membranoblasts. The morphological data obtained significantly expands our knowledge of the morphological diversity of the radula formation in Gastropoda.     

Morphology and cell division of the oxytrichids Architricha indica nov. gen., nov. sp., and Histriculus histrio (Müller, 1773), Corliss, 1960 (Ciliophora, Hypotrichida)

The oxytrichid ciliate Architricha indica nov. gen., nov. sp., isolated from the river Yamuna, Delhi, shows a new combination of characters. It possesses a flexible body, 18 frontal-ventral-transverse (FVT) cirri, 3 right and 2 left marginal cirral rows, 6 dorsal bristle rows and 3 caudal cirri (CC). The FVT cirri arise from 6 primordia, which utilize 6 parental cirri in their origin as is typical of Oxytricha species. Multiple marginal rows (MMR) develop through 5 independent marginal primordia arising \"within-row\", 1 in each parental marginal row. All the 5 marginal rows are thus morphogenetically active. Such a mode of formation of MMR has not been recorded among oxytrichids and has necessitated separation of A. indica at the generic level. Histriculus, on the other hand, has well-known characteristics, viz. rigid body, confluent marginal rows and absence of CC. The morphogenesis of Histriculus histrio has been described by Berger and Foissner [1997. Cladistic relationships and generic characterization of oxytrichid hypotrichs (Protozoa, Ciliophora). Arch. Protistenkd. 148, 125-155]. Reinvestigation of very early stages of development revealed that (i) the FVT cirral primordia utilize kinetosomes from 5 parental FVT cirri, (ii) the primordium II of the proter is of a composite origin: kinetosomes from the oral primordium merge with the primordium II that originates from the buccal cirrus II/2 and (iii) the FVT primordia V and VI for the 2 daughter cells arise sequentially from the parental cirrus V/4. Thus, the genus Histriculus exhibits a new combination of characters with respect to the origin of FVT cirri, an additional pattern to be added to the known 6 patterns of FVT development in oxytrichids [Berger and Foissner, 1997; Berger, H., 1999. Monograph of the Oxytrichidae (Ciliophora, Hypotrichida), Kluwer Academic Publishers, Dordrecht/Boston/London].     

Morphological characteristics of the pharynx of Nereis diversicolor Müller, 1776 (Polychaetes, Nereidae)

Within the biometrical study of the Nereidae and in order to characterize the different populations, we looked for the most relevant biometrical characteristics. In fact, for these sea-animals, the weight and length remain just significant statements within certain limits; on the other hand the length of the maxillary, the number of paragnaths which decorate the proboscis can be precisely known.     

Occurrence of Pomphorhynchus laevis Müller 1776 (Acanthocephala) in Silurus glanis (L.) from the River Po.

The sheatfish, Silurus glanis (L.), from the terminal part of River Po was examined for the presence of helminth parasites. Of 182 S. glanis specimens, 95 (52.2%) were infected with the acanthocephalan Pomphorhynchus laevis. Mid-gut followed by fore-gut appeared to be the most infected portions of host alimentary canal. In 45 sheatfish of total length < or = 40 cm, specimens of P. laevis were found encapsulated in mesenteric and peritoneal tissues. A comparison between light and electron microscopy on features and stages of testis development in both encapsulated male P. laevis and intestinal male parasites showed that the encysted acanthocephalans were immature; mature spermatozoa were rarely found within the testis of worms from the alimentary canal. Among extraintestinal P. laevis specimens, the presumable eversion of parasite praesoma was observed and described. The results of the present survey suggest that small-size individuals of S. glanis could be used as paratenic host by P. laevis during its life cycle in the study area.     

ITS rDNA sequences of Pomphorhynchus laevis (Zoega in Müller, 1776) and P. lucyi Williams & Rogers, 1984 (Acanthocephala: Palaeacanthocephala)

The internal transcribed spacers (ITS-1 and ITS-2) of the ribosomal RNA gene of Pomphorhynchus laevis (Zoega in Müller, 1776) (Acanthocephala) isolated from various fish species across Central and Southern Europe were compared with those of P. lucyi Williams & Rogers, 1984 collected from the largemouth bass Micropterus salmonoides Boulenger from the USA. The nucleotide sequences of ITS regions of P. laevis from minnows Phoxinus phoxinus (L.) and chub Leuciscus cephalus (L.) from two distant localities in the Slovak Republic were found to be 100% identical. The ITS-1 and ITS-2 of P. laevis from chub from the Czech Republic and Italy were also mutually identical, but significantly different from Slovak worms (88.7% identity for ITS-1, 91.3% identity for ITS-2). A fifth sample collected from Barbus tyberinus Bonaparte from Italy was very similar to the sympatric Italian isolate from chub, possessing four nucleotide substitutions in ITS-1 (98.4% identity). The ITS rDNA sequences of P. lucyi differed significantly from those of P. laevis; the values of identity were 51.8–56.1% for ITS-1 and 63.1–65.3% for ITS-2, and were significantly higher than the range of P. laevis within-species variability. The results based on the ITS sequences confirmed the occurrence of strains in P. laevis from Continental Europe which are well defined by molecules but reveal only slight differences in their morphology.