Seasonal changes in the intestinal mucosa of winter flounder, Pseudopleuronectes americanus (Walbaum), from Passamaquoddy Bay, New Brunswick

Winter flounder from Passamaquoddy Bay, N.B. undergo an annual fast from November to May which results in a decrease in the slope of the length-weight relationship (3·17 to 2·54), in the condition factor (9 to 12%), in the liver (75%) and white muscle (24%) lipid contents, and an increase in muscle water content (2·4%). Winter flounder appear to have sufficient lipid reserves to support the winter fast, as muscle water content declined only at the onset of feeding.
The intestine could be divided into pyloric caeca (4), foregut, midgut and hindgut. Mucosal folding was reduced in all sections of the intestine during the fast. Goblet cell number declined, but little change in enterocyte ultrastructure was observed. Intestinal length remained the same, although the caeca shortened. Overall, mucosal mass declined by 57% from May to January, while surface area declined by 50%. This value is less than that in literature reports for a fast of shorter duration in freshwater rainbow trout. We propose that the continued need for salt and water transport for osmoregulation maintains the proximodistal gradient of mass and surface area and ameliorates the effect of starvation on mucosal mass and area.     

Gyrodactylus neili n. sp. (Monogenea: Gyrodactylidae), a parasite of chain pickerel Esox niger Lesueur (Esocidae) from freshwaters of New Brunswick, Canada

Gyrodactylus neili n. sp. (Monogenea: Gyrodactylidae) is described from the fins and body surface of Esox niger Lesueur (chain pickerel) (Esocidae) from the St. Croix River drainage, New Brunswick, Canada. G.␣neili n. sp. resembles most closely G. fryi Cone & Dechtiar, 1984, a parasite of E. masquinongy in North America, in having relatively large thin hamuli, well-developed marginal hook sickles with a relatively long, wide blade and short handle, a ventral bar with small antero-lateral processes and tongue-shaped membrane, and a cirrus with many small spines in two rows. The new species is easily separated from G. fryi by the length of the hamuli (70-76 m versus 92 m, respectively), by the distal width of the sickle (7–9 versus 14-16 m, respectively) and by subtle differences in the shape of the toe and heel of the marginal hook sickle. Sequence data (922 bp) of rDNA (internal transcribed spacers 1 and 2 and 5.8S) of G. neili n. sp. returned no identical matches in GenBank. The 5.8 sequence alone, however, was identical to morphologically similar gyrodactylids of the subgenus Gyrodactylus from cyprinid fishes in Eurasia. The discovery of G. neili n. sp. and features of its genetic makeup support the idea that this lineage parasitised ancestral cyprinids and that it radiated, possibly through predator/prey interactions, to an ancestor of contemporary Esox. It is concluded that DNA comparison of monogeneans on Holarctic freshwater hosts, such as E.␣lucius, may shed light on the nature of speciation of these parasites.     

Gyrodactylus gvozdevi n. sp. (Gyrodactylidae: Monogenea) from Noemacheilus dorsalis (Kessler) in Kazakhstan

Gyrodactylus gvozdevi n. sp. (Gyrodactylidae: Monogenea) is described from the skin of the freshwater fish Noemacheilus dorsalis (Kessler) (Cobitidae: Cypriniformes) from Kazakhstan. This species is most closely related to G. pseudonemachili Ergens & Bykhovsky, 1967 in the shape and size of the anchors and both the ventral and dorsal bars, but can be distinguished from it by the shape and size of the hookproper of the marginal hooks.     

Description of Gyrodactylus banmae n. sp. (Monogenea,Gyrodactylidae) parasitic on zebrafish,Danio rerio

A new species of Gyrodactylus was described on the body surface of zebrafish (Danio rerio) in China. Basing on morphological characteristics and ITS sequence, we identified the parasite as a new member of the Gyrodactylus-wageneri group. Morphologically, Gyrodactylus sp. nov. is greatly similar to “G. zebrae”, another species parasitic on zebrafish: both have moderately stout hamulus, marginal hook sickle with a prominent heel and toe, as well as a curved blade. However, distinct haptoral shape differences were detected between these two species. The dorsal bar is straight in Gyrodactylus sp. nov. but strongly curved in “G. zebrae”, and the sickle shaft in Gyrodactylus sp. nov. is approximately perpendicular to the base, but in “G. zebrae” it is slanted downwards. The ITS1-5.8S-ITS2 sequence also indicate that Gyrodactylus sp. nov. exhibits the highest similarity to “G. zebrae”: 95.7% sequence identity suggests interspecific differentiation. Phylogenetic analysis of the ITS1-ITS2 sequence showed that Gyrodactylus sp. nov. formed a sister clade with “G. zebrae”, and exhibited a relatively close phylogenetic relationship with G. kobayashii, G. gurleyi, and G. longoacuminatus, all of which parasitise on goldfish, Carassius auratus. To test the susceptibility of zebrafish and goldfish to the Gyrodactylus sp. nov., ten gyrodactylids were inoculated to the caudal fin of zebrafish and goldfish. The gyrodactylids exhibited the ability to attach themselves to the goldfish, and some gyrodactylids reproduced a few days after the inoculation. On day 9, however, the mean abundance sharply decreased to zero on goldfish and increased to more than 30 on zebrafish. The result suggested that golfish is an unsuitable host for Gyrodactylus sp. nov. Therefore, on the basis of morphology, molecular sequence similarity, and host susceptibility, we conclude that the gyrodactylid found on the zebrafish is a new species, which we named Gyrodactylus banmae.     

Gyrodactylus anarhichatis n. sp. and G. microanchoratus n. sp. (Monogenea: Gyrodactylidae) from the Atlantic wolf-fish Anarhichas lupus (Anarhichadidae) off the coast of Norway

The gyrodactylid monogeneans Gyrodactylus anarhichatis n. sp. and G. microanchoratus n. sp. are reported from the skin and fins of wild Atlantic wolf-fish Anarhichas lupus L. caught off the coast of northern Norway. G. anarhichatis n. sp. is also reported from farmed Atlantic wolf-fish and spotted wolf-fish A. minor Olafsen. G. anarhichatis n. sp. most closely resembles G. corti Mizelle & Kritsky, 1967, but is also similar to G. perlucidus Bychowsky & Poljansky, 1953 and G. errabundus Malmberg, 1970, while G. microanchoratus n. sp. differs from most other Gyrodactylus spp. by having marginal hooks longer than anchors and a peculiar lump on the marginal hook sickle toe pointing towards the sickle point.     

Gyrodactylus longipes n. sp. (Monogenea: Gyrodactylidae) from farmed gilthead seabream (Sparus aurata L.) from the Mediterranean

Gyrodactylus longipes n. sp. (Monogenea, Gyrodactylidae) is described from the gills of farmed juvenile gilthead seabream (Sparus aurata L.) from two sites located in Italy and Bosnia-Herzegovina and represents the second species of Gyrodactylus to be described from S. aurata. Gyrodactylus orecchiae Paladini, Cable, Fioravanti, Faria, Di Cave et Shinn, 2009 was the first gyrodactylid to be described from S. aurata, from populations cultured in Albania and Croatia. In the current study, G. longipes was found in a mixed infection with G. orecchiae on fish maintained in Latina Province, Italy, thus extending the reported distribution of the latter throughout the Mediterranean. The morphology of the opisthaptoral hard parts of G. longipes is compared to those of G. orecchiae, using light and scanning electron microscopy. Gyrodactylus longipes is characterised by having larger, elongated ventral bar processes and long, triangular-shaped toe region to their marginal hook sickles which, by comparison, are rhomboid in G. orecchiae. The marginal hook sickles of G. longipes are almost double the size of G. orecchiae which allows for their rapid discrimination from each other in mixed infections. A comparison of the DNA sequence of the ribosomal internal transcribed spacer 1 and 2 regions (ITS1 and ITS2) of G. longipes with the corresponding sequence from G. orecchiae and with those available in GenBank, supports the separate species status of G. longipes. Part of this study necessitated an overview of the existing Gyrodactylus fauna from Italy and Bosnia-Herzegovina; a summary from each country is provided here to assist future investigations.     

A description of a new species Gyrodactylus moldovicus sp. n. (Monogenea: Gyrodactylidae) from the European mudminnow Umbra krameri Walbaum, 1792 from the lower Dnester basin

Gyrodactylus moldovicus sp. n. found on gills, body and in nasal cavities of the European mudminnow (Umbra krameri) differs from G. slovacicus Ergens, 1963 also living on the this host by bigger size of the body, anchors and marginal hooks; from G. cylindriformes Mueller et Van Cleave, 1932 living on the American mudminnow Umbra limi--by bigger size of the body; from G. limi Wood et Mizelle, 1957 also from U. limi--by the form of ventral and dorsal bars and form of marginal hooks. It differs from other freshwater gyrodactylids by special type of marginal hooks which have a hook-like end of the blade. Gyrodactylus moldovicus, G. slovacicus and G. limi have marginal hooks of quite different morphological types. By the morphology of anchors, ventral and sometimes dorsal bars and also morphology of cirrus, G. moldovicus is most related to three species from Cyprininae: G. stankovichi Ergens, 1970, G. longoacuminatus Zitnan, 1964 f. typica and G. shulmani Ling, 1962.     

Gyrodactylus gemini n. sp. (Monogenea: Gyrodactylidae), a parasite of Semaprochilodus taeniurus (Steindachner) from the Venezuelan Amazon

Gyrodactylus gemini n. sp. (Monogenea, Gyrodactylidae) is described from the surface of the body and fins of the fish Semaprochilodus taeniurus (Steindachner) imported into Britain from the Venezuelan Amazon. The new species differs from other species of the genus, including those described from South and Central America, by having: (i) stout hamuli with straight shafts and diverging roots; (ii) marginal hooks with the sickle length larger than the width; (iii) a dorsal bar without a medial constriction; (iv) a rectangular ventral bar with short processes; (v) a triangular ventral bar membrane; and, most obviously, (vi) at least two generations which can develop two embryos simultaneously. This is the first known species of the genus Gyrodactylus from the Venezuelan Amazon and the first record of the subgenus Gyrodactylus (Gyrodactylus) from South America.     

The nuclear rDNA region of Gyrodactylus arcuatus and G. branchicus (Monogenea: Gyrodactylidae)

The primary structure of the ribosomal DNA internal transcribed spacers (ITS-1 and ITS-2) and 5.8S rRNA gene were used to characterize and identify 2 monogenean species of Gyrodacrylus living externally on the threespine stickleback (Gasterosteus aculeatus). The ITS region was amplified by PCR from freshwater, brackish, and marine isolates of Gyrodactylus arcuatus and G. branchicus, and the ends of the coding regions were identified by comparative alignment. No intraspecific and very low interspecific variation were observed in the 5.8S rRNA gene; high inter- and low intraspecific variation were revealed in the ITS-1 and ITS-2 regions. The morphological species identification was in all cases confirmed by the molecular identification. Intraspecifically, samples from 2 locations in the North Sea could be differentiated, but the Baltic sample resembled North Sea genotypes. Our approach offers perspectives for a multimetric genetical, morphometrical, and ecological taxonomy of the genus Gyrodactylus.     

The description of Gyrodactylus mulli sp. n. (Monogenea: Gyrodactylidae) from the Black Sea blunt-snouted mullet Mullus barbatus ponticus

A new species Gyrodactylus mulli sp. n. is described from the thorax fins of blunt-snouted mullet Mullus barbatus ponticus by the collections of B. E. Bychowsky made in 1947 near Karadag on the Black Sea. Gyrodactylus mulli sp. n. differs from G. alviga Dmitrieva et Gerasev, 2000 (described from blunt-snouted mullet too) in having another morphotype of the marginal hooks. The new species differs from G. proterorhini Ergens, 1967, which has the identical type of the marginal hooks, in having longer membrane of the ventral connective bar, longer point of the anchors, shorter marginal hooks, and lesser size of the cirrus.     

Gyrodactylus medaka n. sp. (Monogenea: Gyrodactylidae) parasitic on wild and laboratory-reared medaka Oryzias latipes (Beloniformes: Adrianichthyidae) in Japan

Gyrodactylus medaka n. sp. (Monogenea: Gyrodactylidae) is described from the skin, fins, and gills of medaka Oryzias latipes (Beloniformes: Adrianichthyidae) from Japan. This new species was collected from wild medaka in Hiroshima, Aichi, Saga, and Kumamoto prefectures, and laboratory-reared medaka in Chiba and Aichi prefectures. The small marginal hook sickle (≤4?μm) and the length of the marginal hook of the new species are the diagnostic morphological characters differentiated from other gyrodactylids reported from Asia. The pairwise sequence divergences for the interspecific variation in ITS regions and the phylogenetic analysis suggest that the populations of G. medaka n. sp. may have a similar genetic variation as the medaka populations in Japan. Gyrodactylus medaka n. sp. and Dactylogyrus oryziasi (Monogenea: Dactylogyridae) can maintain their populations in laboratory aquaria using medaka as their hosts, and these monogeneans and medaka have the potential as experimental model animals for clarifying various aspects of their host-parasite relationships. In addition, we report the composition of modified ammonium picrate-glycerin (APG) and show it is advantageous for monogenean taxonomy.     

Pauciconfibula subsolana n. sp. (Monogenea: Microcotylidae) from Morone americana (Perciformes: Percichthyidae) collected in fresh water in New Brunswick, Canada.

Pauciconfibula subsolana n. sp. (Monogenea: Microcotylidae) is proposed for parasites found on the inner surface of the operculum of Morone americana collected in the freshwater reaches of the Saint John River, near Mactaquac, New Brunswick. Pauciconfibula subsolana is differentiated from other species in the genus by the 2 posterolateral clamp sclerites, each of which is composed of 2 distinct sections, and by the absence of appendages on the eggs. An amended generic diagnosis is provided for Pauciconfibula. Pseudoaspinatrium Mamaev, 1986, is considered a junior synonym of Pauciconfibula Dillon and Hargis, 1965, and the species previously assigned to Pseudoaspinatrium are transferred to Pauciconfibula as Pauciconfibula euzeti (Ktari, 1971) n. comb., Pauciconfibula gallieni (Euzet and Ktari, 1971) n. comb., and Pauciconfibula pogoniae (MacCallum, 1913) n. comb.     

Gyrodactylus pictae n. sp. (Monogenea: Gyrodactylidae) from the Trinidadian swamp guppy Poecilia picta Regan, with a discussion on species of Gyrodactylus von Nordmann, 1832 and their poeciliid hosts

Gyrodactylus pictae n. sp. is recorded from Poecilia picta in heterospecific shoals with the guppy P.reticulata in Northern Trinidad. G. pictae is morphologically similar to G. turnbulli Harris, 1986, but the hamuli and marginal hooks are slightly smaller and more gracile. The toe and the point of the marginal hook have a distinctly different shape, providing the best morphological characters for distinguishing the two species. The rDNA ITS1 and ITS2 sequences differ from those of G. turnbulli (the closest relative) by >5, suggesting that these two taxa are not sibling species. The origin of the two species on poeciliids of the subgenus Micropoecilia is discussed, and it is suggested that this may represent a case of host–parasite co-evolution.     

Identification of a host-associated species complex using molecular and morphometric analyses,with the description of Gyrodactylus rugiensoides n. sp. (Gyrodactylidae,Monogenea)

Gyrodactylus rugiensis was originally described as a parasite occurring on the marine gobies Pomatoschistus minutus and Pomatoschistus microps. In our preliminary survey this species was also frequently found on Pomatoschistus pictus and Pomatoschistus lozanoi. Subsequent molecular analysis of the internal transcribed spacers rDNA region revealed that this parasite actually represents a complex of two apparently cryptic species, one restricted to P. microps and the other shared by P. minutus, P. lozanoi and P. pictus. Morphometric analyses were conducted on 17 features of the opisthaptoral hard parts of specimens collected from all four host species. Standard discriminant analysis showed a clear separation of both genotypes by significant differences in marginal hook and ventral bar features. Statistical classifiers (linear discriminant analysis and nearest neighbours) resulted in an estimated misclassification rate of 4.7 and 3.1%, respectively. Based on molecular, morphological and statistical analyses a new species, Gyrodactylus rugiensoides is described. This species seems to display a lower host-specificity than generally observed for Gyrodactylus species as it infects three sympatric host species.However, seasonal and host-dependent morphometric variation is shown for G. rugiensoides collected on P. pictus. Host-switching and gene flow might be important factors preventing speciation on closely related and sympatric host species. The presence of host associated species complexes in this Gyrodactylus-Pomatoschistus system is also confirmed by the presence of two host-dependent genotypes within G. micropsi found on P. minutus and P. lozanoi, and P. microps, respectively. By comparing host and parasite phylogeny, phylogenetic and ecological factors influencing host-specificity are discussed.     

Demonstrating freedom from Gyrodactylus salaris (Monogenea: Gyrodactylidae) in farmed rainbow trout Oncorhynchus mykiss

This paper describes an approach to demonstrate freedom of individual rainbow trout farms from Gyrodactylus salaris Malmberg, 1957. The infection status of individual farms is relevant should G. salaris be introduced into a country or zone previously known to be free of the parasite. Trade from farms where G. salaris may have been introduced would be restricted until freedom had been demonstrated. Cage, fish and parasite sample sizes were calculated based on the minimum detectable prevalence (P*), test characteristics, population size, and Type I and II errors. Between 5 and 23 cages per farm would need to be sampled to demonstrate freedom at a cage level P* of 10%. The number of fish sampled per cage depended mainly on the test sensitivity (probability of correctly identifying an infected fish). Assuming a test sensitivity of 99% at the fish level, 59 fish per cage are needed (P* = 5%). Since G. salaris may exist in mixed infection with G. derjavini, testing a sample of gyrodactylid parasites may not result in the parasite being detected when present. Test sensitivity at the fish level depends on the number of gyrodactylids on the fish, the proportion of which are G. salaris and the number examined. Assuming a P* of 5% (i.e. G. salaris are at least 5% of the gyrodactylid population), between 20 and 73 parasites per fish would need to be sampled (depending on abundance) to maintain the Type I error at 0.01 (thus a fish level test sensitivity of 99%). This work identifies the critical information, and further research, needed to assess freedom from G. salaris with a known level of confidence; this is essential to provide a sound scientific basis for decision-making about disease control measures.