Pseudarhahdttsynachus yucatanensis sp. n. (Diplectanidae) is described from the gills of the red grouper, Epinephelus maria (Valenciennes, 1824) (Serranidae), from the coast of the Yucatan Peninsula, Mexico. This new species is characterized by having both the ventral and the dorsal squamodiscs composed of 10-12 rows of rods, with 0-1 innermost row forming a closed circle. Furthermore, the vagina of P. yucatanensis has a non-sclerotized ampulla with a fine, sclerotized duct leading to a sclerot-ized seminal receptacle. Prevalence (percentage of infected fish) and abundance (mean number of worms per examined fish) were estimated for P. yucatanensis from 8 localities along the coast of Yucatan. Prevalence varies from 38% to 100%, while abundance was between 1.2 ± 0.6 and 43.2 ± 17.8 worms per ftsh. The lack of linear relationship between the host length and the number of monogcneans per fish (regression F, = 0.56. p = 0.45) was probably due to the fact that the sample was restricted to juvenile hosts.
Sciadicleithrum meekii sp. n. is described from the gills of the cichlid fish Cichlasoma meeki (Brind) from cenotes (= sinkholes) of the Yucatan Peninsula, Mcxico.The new species differs from congeners by having a dorsal hamuli with a prominent superficial root articulated with a straight shaft and curved point, and a vagina with a coiled tube comprised of one ring.
Bothitrema bothi (MacCallum, 1913), a monopisthocotylean monogenean (Bothitrematidae) found on gills and occasionally on the olfactory rosette within the nares of the bothid flounder, Scophthalmus aquosus (Mitchill, 1815), is distributed along the Atlantic coast of the USA from Woods Hole, Massachusetts to Delaware Bay. This study details aspects of the morphology, microecology and biology of the oncomiracidium, juvenile and adult. Adult worms occur almost exclusively between rakers on the first and second gill arches while juveniles occupy secondary gill filaments. Analysis of variance revealed significant arch, side and position effects. Worm attachment and position is maintained largely by suction generated by a circular seal using its 54 radially arranged accessory haptoral sclerotised elements and a marginal valve. A small anterior appendix with two marginal hooks lies dorsal to a deep anteromedian cleft in the haptor, which, together with wall muscles, creates and releases the negative pressure required for attachment. Four pairs of gland openings in the ventrolateral margins of the anterior adhesive area produce secretions for attachment. Operculate eggs with four rounded protuberances and a filament are laid individually at four-minute intervals at 22ºC. Hatching occurs in five days at 20°C. Oncomiracidia have two pairs of eyes, with the posterior pair fused, show both positive and negative phototaxis and swim at a mean rate of 5.2 mm/s at 22°C. Larvae have a circle of 16 hooks and a pair of hamulus primordia. Other accessory haptoral sclerotised structures arise de novo in juveniles after attachment to the host. These data will help to resolve more clearly the relationships of the Bothitrematidae within the Monopisthocotylea.
The Capsalidae are monogeneans parasitizing ''skin'', fins and gills of marine fishes. Some capsalids are pathogenic to cultivated fish and a few have caused epizootic events. It is a cosmopolitan family with broad host associations (elasmobranchs and teleosts, including sturgeons). Approximately 200 capsalid species are placed in nine subfamilies and 44-46 genera, some of which are well known (Benedenia, Capsala, Entobdella, Neobenedenia). Sturgeons host two capsalid species (Nitzschiinae) and 15 species in five genera are reliably reported from elasmobranchs. The combination of ancient (shark, ray, sturgeon) and modern (teleost) host fish lineages indicates that capsalid evolution is likely a blend of coevolution and host-switching, but a family phylogeny has been lacking due to deficient knowledge about homologies. The current phenetic subfamilial classification is discussed in detail using a preliminary phylogeny generated from large subunit ribosomal DNA sequence data from representatives of five subfamilies. Monophyly of the Capsalidae is supported by possession of accessory sclerites. Hypotheses are proposed for the possible radiation of capsalids. A suggestion that Neobenedenia melleni, a pathogenic species atypical due to its broad host-specificity (>100 host teleost species from >30 families in five orders), may be a complex of species is supported from genetic evidence. This may explain peculiarities in biology, taxonomy, host associations and geographic distribution of N. 'melleni' and has implications for fish health. Holistic studies using live and preserved larval and adult capsalid specimens and material for genetic analysis are emphasised to further determine identity, phylogeny and details of biology, especially for pathogenic species.
The current work describes two new species of Gyrodactylus von Nordmann, 1832 collected from pipefish Syngnathus scovelli (Evermann et Kendall) and Syngnathus typhle L. during two separate gyrodactylosis episodes on fish held in a public aquarium located in northern Italy. The gyrodactylids collected from the skin, fins and gills of pipefish were subjected to a morphological analysis of the attachment hooks and the morphometric data were compared to the four species of Gyrodactylus previously described from syngnathid hosts, namely G. eyipayipi Vaughan, Christison, Hansen et Shinn, 2010, G. pisculentus Williams, Kritsky, Dunnigan, Lash et Klein, 2008, G. shorti Holliman, 1963 and G. syngnathi Appleby, 1996. Principal components analysis (PCA) of the morphological data indicated six clusters; two discrete groups among the specimens taken from the pipefish held in the Italian aquarium and four further groups representing G. eyipayipi, G. pisculentus, G. shorti and G. syngnathi. Molecular sequences of the ribosomal internal transcribed spacers (ITS1 and ITS2) and the 5.8S gene for the new species considered here were then compared with those available for other species in GenBank. The comparison did not reveal any identical match, supporting the morphological analysis that Gyrodactylus corleonis sp. n. from S. typhle and Gyrodactylus neretum sp. n. from S. scovelli represent distinct species. Both G. corleonis and G. neretum possess robust hamuli, marginal hook blades that curve smoothly from their sickle base to a point beyond the toe and, ventral bars with a broad median portion and a reduced membrane. Gyrodactylus corleonis, however, can be distinguished on the basis of its heart-shaped ventral bar; G. neretum has a 1:2 hamulus point:shaft ratio and a rectangular-shaped ventral bar. A redescription of the haptoral hard parts of the four species previously recorded on pipefish is also presented.
The elongated encased spermatophores of the capsalid (entobdelline) monogeneans Neoentobdella diadema (Monticelli, 1902) Kearn et Whittington, 2005 and N. apiocolpos (Euzet et Maillard, 1967) Kearn et Whittington, 2005 have been found attached by their proximal ends to the region of the vaginal opening, with the bulk of the spermatophore projecting from the vagina and therefore lying outside the body. In spite of previous reports, no spermatophores were found projecting from the common genital opening and if spermatophore exchange is as rapid as it is in the related entobdelline Entobdella soleae, then the chances of finding a spermatophore in this location are small. In N. diadema and N. apiocolpos it is likely that sperm enters the vagina through the open proximal end of an attached spermatophore, after which the empty spermatophore case is probably discarded. There is no evidence for a previous proposal that the whole spermatophore is engulfed by the vagina followed by digestion of the case to release the sperm. Three specimens of N. diadema were found each with two spermatophore cases projecting from the vagina and a specimen of N. apiocolpos carried three cases. Assuming that each parasite is able to donate or receive only one spermatophore at each mating, then the presence of one spermatophore does not prevent a further mating and acceptance of a fresh spermatophore. In spite of differences between the spermatophores of E. soleae and N. diadema/N. apiocolpos, the events of spermatophore exchange may be similar.
Using the localization of nonspecific esterases, the nervous system of Polystoma indicum Diengdoh et Tandon, 1991 could be revealed in toto. The nervous system is bilaterally symmetrical. Cerebral ganglia, which are connected by a thick dorsal commissure, are present dorsal to the pharynx. From the cerebral ganglia arise five anterior pairs and four posterior pairs of nerve trunks. The anterior nerves and/or their fine branches join to form a conspicuous circumoral nerve ring complex. The posterior nerves unite in the opisthaptoral region to form two main haptoral nerves, the branches from which innervate the components of the opisthaptor. Presence of nerve cells is also revealed in association with the main nerves, more predominantly in the vicinity of the opisthaptoral suckers.
Dendromonocotyle lotteri sp. n. is described from the dorsal skin surface of the stingray Himantura gerrardi (Gray) on exhibit in the public aquarium at the Atlantis resort in Dubai. It is differentiated from all other Dendromonocotyle species by the unique morphology of the distal portion of the sclerotised male copulatory organ. Dendromonocotyle lotteri is the second representative in the genus with 56 marginal haptoral papillae having a papillae to loculus association represented numerically as 6-6-8-8. We found Dendromonocotyle colorni Chisholm, Whittington et Kearn, 2001 on the same host specimens at the Atlantis resort public aquarium and Dendromonocotyle kuhlii Young, 1967 on Neotrygon kuhlii (Müller et Henle) kept at Burgers' Zoo Aquarium in Arnhem, The Netherlands. Supplemental information is provided for both D. colorni and D. kuhlii. The presence of Dendromonocotyle infections in public aquaria and host specificity are discussed. A key to the 17 species of Dendromonocotyle is also provided.
Numerous specimens of Calydiscoides spp. from Lethrinus nebulosus and L. harak, and fewer specimens from L. lentjan, L. ravus and L. obsoletus, collected off New Caledonia, South Pacific, were examined. Three species of Calydiscoides were recognized. Calydiscoides difficilis (Yamaguti, 1953) Young, 1969 was generally the most abundant species on the five hosts. Specimens of C. difficilis were measured and compared to the type specimens (from Indonesia) and museum vouchers (from Australia and the Arabian Gulf). The morphology of the massive male copulatory organ and of haptoral sclerotized parts was similar, but specimens from the same host and from different hosts showed wide morphometric variations; it is concluded that C. difficilis has a high degree of variability, although the possibility of a species complex remains. Calydiscoides duplicostatus (Yamaguti, 1953) Young, 1969 was found on L. nebulosus, L. harak and L. lentjan; specimens were homogeneous in the three hosts and similar to the type specimens. Calydiscoides terpsichore sp. n. is described from L. nebulosus (type host) and L. harak and was uncommon in both fish. The new species, a member of the 'australis group', is characterized by its Y-shaped male copulatory organ, with the left branch bearing a trifurcated secondary branch. Lethrinus nebulosus and L. harak shared the 3 species of Calydiscoides studied here, a fact probably related with their close phylogenetic relationships. Among the 15 species of Lethrinus present in New Caledonia, 11 were examined and 9 species harboured 1-3 species of Calydiscoides each. Only 7 species of Calydiscoides were found, due to their stenoxenous specificity. Each species of Calydiscoides has 1 to 5 hosts.
The present study is focusing on the transmission of the monogenean ectoparasite Gyrodactylus salaris Malmberg, 1957, a major pathogen on natural populations of Norwegian Atlantic salmon, Salmo salar L. In laboratory experiments the transmission rate of G. salaris after direct host to host contact was positively correlated with water temperature (1.2, 4,7 and 12.2°C). The transmission of detached G. salaris in the planktonie drift was studied in field experiments where salmon parr were individually isolated for 24 hours in small wire mesh cages suspended in the water column. Ten out of 157 salmon parr (prevalence 6.4%, mean intensity 1.0) contracted G. salaris infections after this exposure. Furthermore, 200 uninfected marked salmon parr were released into the same area of the river. After 24 and 48 hours, respectively 18 and 19 marked parr were caught by electro-fishing. The prevalence of G. salaris was 44.4% (mean intensity 1.9) after 24 hours, rising to 57.9% (mean intensity 2.3) after 48 hours. Gyrodactylids have no specific transmission stage or swimming ability, but detached G. salaris drifting in the water column were found to infect salmon parr. However, the transmission rate was markedly higher to free-living fish, suggesting that transmission routes such as indirect transmission from the substrate or direct contact transmission from infected live and/or dead fish, are relatively more important than transmission by drifting detached parasites.