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A detailed account is given about the mode of attachment and histopathological effects of Macrogyrodactylus clarii Gussev, 1961, a viviparous monogenean from the gills of the catfish Clarias gariepinus. Most parasites attach their haptors to the proximal region of the gill filament (primary gill lamellae), while few specimens were seen attached to the distal region. Attachment of the haptor was achieved mainly by the blade of the hamuli, but no evidence was found indicating the participation of marginal hooklets in the attachment. The hamuli of M. clarii penetrate into the interlamellar epithelium of the gill tissue. Some evidences were found to indicate that M. clarii may also utilize suction force during haptoral attachment. The pathological effects of M. clarii are manifested by breakdown of the coating epithelium, necrosis of the epithelial cells, vacuolations inside and outside the host cells, fusion of the gill lamellae, rupture of blood capillaries, infiltration of erythrocytes and degeneration and fibrosis of the interlamellar epithelium. The host response includes the appearance of lymphocytes, mucoid secretions and hyperplasia of the tissue at the site of attachment.

A description is given of three contrasting adhesive attitudes exhibited by three species of capsalid monogeneans from the gills of three different species of teleost fish from Heron Island, Queensland, Australia. The proximal end of the primary lamella of the coral trout, Plectropomus maculatus has a wide inner border, free from secondary lamellae, on each flat face. The haptor of Trochopus plectropomi is small enough to attach to this flat surface without folding. Benedenia sp. 1 attaches itself to the gills of stripey, Lutjanus carponatatus, by folding the haptor longitudinally around the inner edge of the primary lamella. Most specimens of T. plectropomi and all specimens of Benedenia sp. 1 were orientated with the anterior end projecting towards the tip of the primary lamella. Benedenia sp. 2 generally prefers relatively flat surfaces in the gill chamber but is more versatile in its choice of attachment sites on its host, the blacktip cod, Epinephelus fasciatus; two specimens were attached to the gill arch, one to a gill raker and one to the dorsal pharyngeal tooth pad.

The locomotion and attachment of members of the generaMyxinidocotyle andAcanthocotyle (Monogenea, Acanthocotylidae) were studied and marks left by the posterior attachment organ on the hagfish and the rajid host skin were examined by scanning electron microscopy (SEM). The muscle-fibre arrangement in three types of pseudohaptors is described. The pseudohaptor was found to have a suction function. Anatomical data and attachment marks indicate that the hooks of the haptor have a strong attachment capacity. We conclude that in larval stages as well as in adults, the haptor is the most important posterior locomotory organ, whereas the fully developed pseudohaptor is used for stationary attachment. The deep marks caused by both unarmed (Myxinidocotyle) and sclerite-armed (Acanthocotyle) pseudohaptoral ridges appeared to be harmless imprints, whereas the 16 haptoral hooks caused small wounds that may provide potential openings for secondary infections of the host skin.

Malalophus jensenae n. g., n. sp. is described from the gills of the ornate eagle ray Aetomylaeus vespertilio (Bleeker) collected off the eastern coast of the Gulf of Carpentaria, northern Queensland. The new genus is similar to Heliocotyle Neifar, Euzet & Ben Hassine, 1999, with which it shares a haptor bearing seven peripheral loculi and a single dorsal haptoral accessory structure. M.jensenae can be distinguished from species of Heliocotyle by the presence of numerous sclerotised sinuous ridges covering the ventral surfaces of the peripheral loculi of the haptor. It also lacks pseudosepta which are present on the haptor of Heliocotyle species. This is the first published record of a monogenean from an elasmobranch in the Gulf of Carpentaria, Australia.

SUMMARYWe investigated whether host specificity is linked to variability within species ofLamellodiscusmonogeneans, which are gill ectoparasites of the Sparidae. We sampled fish parasites in the northeastern part of the Mediterranean Sea: 4 specialist species, using 1 single host species, and 3 generalist species, using 2 distinct host species. Intraspecific variability was assessed from 2 different datasets. Morphometric variability of the attachment organ, called the haptor, was estimated first from measurements of several sclerified haptoral parts on 102 individuals. Genetic variability was calculated based on comparisons of sequences derived from the first internal transcribed spacer (ITS-1) of nuclear ribosomal DNA of 62 individuals. Morphometric variances in the specialistversusgeneralist species were comparedviaprincipal component analysis andF-tests, and uncorrected genetic distances (p-distances) were estimated within each species. We showed that the inter-individual variance of morphometric characters, as well as p-distances, are clearly greater within generalist species than specialist ones. These findings suggest that a relative increase in morphological and molecular variability enhances the possibility to colonize new host species in monogeneans, and supports the hypothesis that intraspecific variability could be a potential determinant of host specificity.

Lamellodiscus crampus sp. nov. (Monogenea, Diplectanidae) is described from the gills of Dentex maroccanus (Valenciennes) collected from the Gulf of Gabès (Tunisia) in the oriental part of Mediterranean Sea. The new species belongs to the “ignoratus” group (sensu Oliver 1987) characterized by a lamellodisc with complete lamellae and a “lyre” shaped male copulatory organ, and the “ignoratus” sensu stricto subgroup, characterized by a haptor with simple lateral dorsal bars, as proposed by Amine and Euzet (2005). Lamellodiscus crampus can be easily distinguished from all the congeneric species of the subgroup “ignoratus” by the presence, in the “lyre” male copulatory organ, of five spines in the distal portion on the axial side of the paired piece.

Kritskyia n. g. is proposed for K. moraveci n. sp. from the urinary bladder and ureters of Rhamdia quelen (Quoy & Gaimard, 1824), a pimelodid fish from the reservoir of the Hydroelectric Power Station of “Passo Fundo”, Rio Grande do Sul State, Brazil. The new genus is most closely related to Acolpenteron Fischthal & Allison, 1940, from which it differs by having a male copulatory complex composed of a coiled cirrus and a bipartite accessory piece, a sinistral vagina, and an antero-ventrally concave haptor which possesses 14 ventrally directed marginal hooks, but lacks an anterior rim and 4A hooks.

Data on the ontogeny of the posterior haptor of monogeneans were obtained from more than 150 publications and summarised. These data were plotted into diagrams showing evolutionary capacity levels based on the theory of a progressive evolution of marginal hooks, anchors and other attachment components of the posterior haptor in the Monogenea (Malmberg, 1986). 5 + 5 unhinged marginal hooks are assumed to be the most primitive monogenean haptoral condition. Thus the diagrams were founded on a 5 + 5 unhinged marginal hook evolutionary capacity level, and the evolutionary capacity levels of anchors and other haptoral attachement components were arranged according to haptoral ontogenetical sequences. In the final “plotting diagram” data on hosts, type of spermatozoa, oncomiracidial ciliation, sensilla pattern and protonephridial systems were also included. In this way a number of correlations were revealed. Thus, for example, the number of 5 + 5 marginal hooks correlates with the most primitive monogenean type of spermatozoon and with few sensillae, many ciliated cells and a simple protonephridial system in the oncomiracidium. On the basis of the reviewed data it is concluded that the ancient monogeneans with 5 + 5 unhinged marginal hooks were divided into two main lines, one retaining unhinged marginal hooks and the other evolving hinged marginal hooks. Both main lines have recent representatives at different marginal hook evolutionary capacity levels, i.e. monogeneans retaining a haptor with only marginal hooks. For the main line with hinged marginal hooks the name Articulon-choinea n. subclass is proposed. Members with 8 + 8 hinged marginal hooks only are here called Proanchorea n. superord. Monogeneans with unhinged marginal hooks only are here called Ananchorea n. superord. and three new families are erected for its recent members: Anonchohapteridae n. fam., Acolpentronidae n. fam. and Anacanthoridae n. fam. (with 7 + 7, 8 + 8 and 9 + 9 unhinged marginal hooks, respectively). Except for the families of Articulonchoinea (e.g. Acanthocotylidae, Gyrodactylidae, Tetraonchoididae) Bychowsky's (1957) division of the Monogenea into the Oligonchoinea and Polyonchoinea fits the proposed scheme, i.e. monogeneans with unhinged marginal hooks form one old group, the Oligonchoinea, which have 5 + 5 unhinged marginal hooks, and the other group form the Polyonchoinea, which (with the exception of the Hexabothriidae) has a greater number (7 + 7, 8 + 8 or 9 + 9) of unhinged marginal hooks. It is proposed that both these names, Oligonchoinea (sensu mihi) and Polyonchoinea (sensu mihi), will be retained on one side and Articulonchoinea placed on the other side, which reflects the early monogenean evolution. Except for the members of Ananchorea [Polyonchoinea], all members of the Oligonchoinea and Polyonchoinea have anchors, which imply that they are further evolved, i.e. have passed the 5 + 5 marginal hook evolutionary capacity level (Malmberg, 1986). There are two main types of anchors in the Monogenea: haptoral anchors, with anlages appearing in the haptor, and peduncular anchors, with anlages in the peduncle. There are two types of haptoral anchors: peripheral haptoral anchors, ontogenetically the oldest, and central haptoral anchors. Peduncular anchors, in turn, are ontogenetically younger than peripheral haptoral anchors. There may be two pairs of peduncular anchors: medial peduncular anchors, ontogentically the oldest, and lateral peduncular anchors. Only peduncular (not haptoral) anchors have anchor bars. Monogeneans with haptoral anchors are here called Mediohaptanchorea n. superord. and Laterohaptanchorea n. superord. or haptanchoreans. All oligonchoineans and the oldest polyonchoineans are haptanchoreans. Certain members of Calceostomatidae [Polyonchoinea] are the only monogeneans with both (peripheral) haptoral and peduncular anchors (one pair). These monogeneans are here called Mixanchorea n. superord. Polyonchoineans with peduncular anchors and unhinged marginal hooks are here called the Pedunculanchorea n. superord. The most primitive pedunculanchoreans have only one pair of peduncular anchors with an anchor bar, while the most advanced have both medial and lateral peduncular anchors; each pair having an anchor bar. Certain families of the Articulonchoinea, the Anchorea n. superord., also have peduncular anchors (parallel evolution): only one family, the Sundanonchidae n. fam., has both medial and lateral peduncular anchors, each anchor pair with an anchor bar. Evolutionary lines from different monogenean evolutionary capacity levels are discussed and a new system of classification for the Monogenea is proposed.

The unarmed haptor of Anoplodiscus australis erodes the epidermis and attaches to the basal lamina above the stratum compactum in the caudal fin of Acanthopagrus australis by an eosinophilic, weakly PAS-positive and strongly toluidine blue-positive secretion. Ultrastructural evidence shows that the adhesive secretion, in the form of rod-shaped bodies, is produced by subtegumentary cells that connect by ducts to the thin, ventral syncytial tegument of the haptor; these bodies pass into the tegument, then coalesce in the host-parasite interface. This means of attachment has developed by an enhancement and regional specialization of the subtegumentary secretory cells associated with a syncytial tegument in monogeneans and some other platyhelminths. The available evidence indicates that the adult parasite is permanently attached.

Trimusculotrema warnaki gen. et sp. nov. is described from the skin of Himantura uarank Forsskal. Trimusculotrema is distinguished from other genera in the Benedeniinae by the following combination of anatomical features: accessory sclerites and anterior hamuli small; haptor with two or three intrinsic, concentric muscle bands; haptor papillate ventrally; cirrus sac with internal seminal vesicle and spermatophore matrix reservoir; separate male and female pores opening ventrally and dorsally respectively; vagina short. On the basis of these features Benedenia micracantha Euzet and Maillard, 1967 from the skin and B. leucanthemum Euzet and Maillard, 1967 from the gills of Dasyatis marmorata Steindachner off Senegal are transferred to the new genus as Trimusculotrema micracantha comb. nov. and T. leucanthemum comb. nov. The presence of haptoral papillae, noted previously in some species of Entobdella, perhaps indicates that the new genus is more closely related to entobdellids than to benedeniids. Several l...

We describe herein the first occurrence of the monogenean Urocleidoides vaginoclaustrum in the wild. This monogenean was originally described from an aquarium neotropical fish examined in India. Worms were collected from the gills of Xiphophorus hellerii, a species native to tropical Mexico but introduced to the Los Berros Spring in the State of Durango, Northern Mexico. These specimens showed slight morphological differences in the sclerotized structures of the haptor with respect to the specimens described from India. A brief morphological characterization of this species is presented.

Haliotrema leporinus n. sp. and Haliotrema pratasensis n. sp. are described from the gills of surgeonfishes (Acanthuridae) off the Pratas Islands in the South China Sea. Haliotrema leporinus n. sp. differs from all other members of the genus by possessing a rabbit-head-shaped sclerotized piece in the haptor. Haliotrema pratasensis n. sp. differs from its congeners by having a copulatory organ with a clockwise coil and a funnel-shaped base and by lacking an accessory piece.

The Capsalinae Baird, 1853 (Monogenea: Capsalidae) is revised based on a thorough review of original descriptions and examination of type museum material, where available, to validate species. A total of 262 type and voucher specimens was studied representing apparently 42 of the 60 currently described capsaline species. A combination of characters that should be independent of variation due to specimen preparation techniques was chosen to discriminate species. These characters include the presence/absence of papillae on the ventral surface of the haptor, the presence/absence and the morphology of haptoral accessory sclerites and the presence/absence of dorsomarginal body sclerites and their morphology and distribution. We consider that only 36 of the 60 nominal capsaline species are valid. We could find no support for Caballerocotyla Price, 1960 and therefore we synonymise it with Capsala Bosc, 1811. Under the current concept we recognise 22 species of Capsala, 7 species of Capsaloides Price, 1938, 3 species of Nasicola Yamaguti, 1968 and 4 species of Tristoma Cuvier, 1817. The following Capsala species are considered valid: C. albsmithi (Dollfus, 1962) n. comb.; C. biparasitica (Goto, 1894) Price, 1938; C. caballeroi Winter, 1955; C. foliacea (Goto, 1894) Price, 1938; C. gouri Chauhan, 1951; C. gregalis (Wagner & Carter, 1967) n. comb.; C. interrupta (Monticelli, 1891) Johnston, 1929; C. katsuwoni (Ishii, 1936) Price, 1938; C. laevis (Verrill, 1875) Johnston, 1929; C. maccallumi Price, 1939; C. magronum (Ishii, 1936) Price, 1938; C. manteri Price, 1951; C. manteriaffinis (Mamaev, 1968) n. comb.; C. martinierei Bosc, 1811; C. notosinense (Mamaev, 1968) n. comb.; C. nozawae (Goto, 1894) Price, 1938; C. onchidiocotyle (Setti, 1899) Johnston, 1929; C. ovalis (Goto, 1894) Price, 1938; C. paucispinosa (Mamaev, 1968) n. comb.; C. pelamydis (Taschenberg, 1878) Price, 1938; C. poeyi (Perez-Vigueras, 1935) Price, 1938; C. pricei Hildago-Escalente, 1950. We consider the following Capsaloides species valid: C. cornutus (Verrill, 1875) Price, 1938; C. cristatus Yamaguti, 1968; C. hoffmannae Lamothe-Argumedo, 1996; C. magnaspinosus Price, 1939; C. nairagi Yamaguti, 1968; C. perugiai (Setti, 1898) Price, 1938; C. sinuatus (Goto, 1894) Price, 1938. The following Nasicola species are deemed valid: N. brasiliensis Kohn, Baptista-Farias, Santos & Gibson, 2004; N. hogansi Wheeler & Beverley-Burton, 1987; N. klawei Stunkard, 1962. Presently, we consider the following Tristoma species valid: T. adcoccineum Yamaguti, 1968; T. adintegrum Yamaguti, 1968; T. coccineum Cuvier, 1817; T. integrum Diesing, 1850. A list of new and re-established synonyms is provided. The status of each species is discussed in detail and a key to all capsaline species that we consider valid is presented. The following 5 capsaline species are considered to be species inquirendae: Caballerocotyla phillippina Velasquez, 1982; Capsala megacotyle (Linstow, 1906) Johnston, 1929; Tristoma fuhrmanni Guiart, 1938; T. levinsenii Monticelli, 1891; T. uncinatum Monticelli, 1889. The importance of careful character selection to discriminate between capsaline species and the need for studies of live parasites to obtain additional characters based on reproductive structures is addressed. Hostspecificity in the Capsalinae is also discussed.

SUMMARYThe infection biology of Branchotenthes octohamatus (Monogenea: Hexabothriidae) from the gills of the southern fiddler ray, Trygonorrhina fasciata (Rhinobatidae), was studied using the fluorescent dye, 5(6)-carboxyfluorescein diacetate N-succinimidyl ester (CFSE). This is the first use of this technique on a monogenean species with unciliated larvae and the first for any monogenean larva infecting an elasmobranch host. CFSE-labelled post-larvae were recovered from gills of T. fasciata within 30 min of exposure to the host, providing strong evidence that larvae invade host gills directly and do not migrate after initial attachment elsewhere. The rapidity with which larvae settled suggests that the mode of infection may deliver larvae directly to the gills via the host's inhalant respiratory current. The specificity of B. octohamatus was investigated by exposing a sympatric rhinobatid host species, the western shovelnose ray, Aptychotrema vincentiana, to B. octohamatus larvae newly emerged from eggs laid by adult parasites from gills of T. fasciata. Experimental exposure of A. vincentiana to freshly hatched B. octohamatus larvae resulted in a persistent infection, indicating that B. octohamatus may not be strictly host specific. Post-larval development charted on these experimentally infected A. vincentiana specimens was slow. Parasites appeared to be sexually mature at 91 days at 21–25°C. Branchotenthes octohamatus larvae bear only 4 pairs of hooklets on the haptor whereas all other hexabothriid larvae described so far have 5 hooklet pairs. Ontogenetic changes to the haptor revealed that it is probably hooklet pair III that is lost from B. octohamatus prior to larval development.

Nine species of spinefoots, Siganus spp., were examined for Pseudohaliotrema spp. (Monogenoidea, Dactylogyridae) from Australia, China, and Egypt. The findings of Pseudohaliotrema sphincteroporus on the gills of Siganus doliatus, Siganus lineatus, and Siganus corallinus and Pseudohaliotrema molnari on the gills of Siganus corallinus, S. doliatus, S. lineatus, and Siganus punctatus from the Great Barrier Reef, Australia, represent new host and locality records for these helminths. Siganus fuscescens from Australia and China; Siganus argenteus, Siganus rivulatus, and Siganus luridus from Egypt; and Siganus vulpinus from Australia were negative for Pseudohaliotrema spp. Pseudohaliotrema is revised and P. sphincteroporus and P. molnari are redescribed; drawings of the sclerotized parts of the haptor and male reproductive system and measurements of Pseudohaliotrema falcata are provided based on available paratypes. Pseudohaliotrema is limited to 3 species: P. sphincteroporus, P. molnari, and P. falcata. Pseudohaliotrema sigani and Pseudohaliotrema virgata are considered junior subjective synonyms of P. sphincteroporus.

Diechodactylus joaberi n. g., n. sp. is described from the body surface of the banded knifefish Gymnotus carapo L. (Gymnotiformes: Gymnotidae) from southeastern Brazil. The new genus is proposed to accommodate species with five pairs of hooks in anterior bilateral clusters on the haptor, three pairs of hooks in a single cluster on the posterior margin of the haptor, sclerites R1 associated with the superficial bar, and confluent intestinal caeca. The presence of five pairs of hooks in two bilateral clusters anterior in the haptor permits the differentiation of species of Diechodactylus from species of all known genera of the Gyrodactylidae. The genus is likely a member of a clade of the Gyrodactylidae comprising genera with a similar hook distribution.

Species of Rhamnocercinae Monaco, Wood et Mizelle, 1954 are gill parasites of sciaenid fishes (Perciformes). Seven are marine species (three in the western Atlantic and four in oriental Pacific) and one is a neotropical freshwater species (Rio Doce Basin, Brazil). While the status of the subfamily may be questioned, this assemblage of species is apparently supported by several shared apomorphic and plesiomorphic characters, such as: (1) peduncular spines with anterior and posterior roots; (2) haptor laterally expanded, armed with anchors (two pairs); bars (one ventral, two dorsal); 14 hooks and haptoral accessory spines; and (3) double (nested) tubes of the male copulatory organ (MCO), directed posteriorly with the genital pore lying posterior to the MCO. The phylogenetic hypothesis for the eight known species of this clade is: (Spinomatrix penteormos (Rhamnocercoides stichospinus, Rhamnocercoides menticirrhi) Rhamnocercus oliveri (Rhamnocercus rhamnocercus (Rhamnocercus stelliferi, Rhamnocercus bairdiella, Rhamnocercus margaritae)). This hypothesis indicates that Spinomatrix penteormos represents the sister group of all remaining rhamnocercines. The resulting phylogenetic sister-group relationships support the transfer of Rhamnocercus stichospinus Seamster et Wood, 1956 to Rhamnocercoides Luque et Iannacone, 1991 as Rhamnocercoides stichospinus (Seamster et Wood, 1956) n. comb.

Pseudodiplectanum syrticum n. sp. (Monogenea: Diplectanidae) is described from the gills of Synapturichthys kleinii (Risso) collected from the Gulf of Gabès in the Mediterranean Sea off Tunisia. The new species differs from the congeneric species by the morphology of the penis and vagina. It resembles the Mediterranean species P. kearni Vala, Lopez-RomanBoudaoud, 1980 from Solea vulgaris Quensel and P. gibsoni Oliver, 1987 from Michrochirus variegatus (Donovan) in its tubular penis, but it differs from these two species by having a vagina with a long tube presenting two loops and a male copulatory organ ending in a curved point. It also differs in the morphology and size of the transverse bars of the haptor. In P. syrticum the ventral transverse bar and dorso-lateral bars are longer than those of P. gibsoni (114 vs 69.5-89 microm and 48 vs 33-44 microm, respectively).

Cornutohaptor nigrescensi n. sp. (Diplectanidae) is described from the gills of the black snook, Centropomus nigrescens (Perciformes: Centropomidae) from the Pacific coast of Mexico. Cornutohaptor n. gen. is proposed for this new species and is characterized by possessing 2 intestinal ceca terminating blindly; a germarium looping right intestinal cecum; bilobed testis; 2 seminal vesicles; 7 pairs of hooks, each with protruding thumb; a grooved ventral bar and coiled male copulatory organ (MCO); an accessory piece comprising a "baglike structure" with an appendage; dorsal bars associated parallelly to body midline; and no adhesive accessory organs on the haptor. Cornutohaptor differs from all confamilial genera by including species with anchors with straight and deep root longest, hook pair 1 reduced in size, MCO with counterclockwise rings, and by the morphology of the accessory piece. Cornutohaptor nigrescensi most closely resembles species of Murraytrema Price, 1937, Lobotrema Tripathi, 1937, and Murraytrematoides Yamaguti, 1958, because of the absence of squamodiscs or lamellodiscs on the haptor and tegumental scales on the posterior portion of the body. Cornutohaptor differs from these genera in the position and number of haptoral bars (2 bars in Lobotrema spp., dorsal bars transversally associated in Murraytrema and Murraytrematoides spp.) and in having a coiled MCO (copulatory organ is a comparatively straight, poorly sclerotized tube in Murraytrematoides spp.). This is the first diplectanid described from a centropomid along the Pacific coast of Mexico.

Phalloidin fluorescence technique, enzyme cytochemistry and immunocytochemistry, in conjunction with confocal scanning laser microscopy, were used to describe the neuromusculature of the monogenean skin parasite Macrogyrodactylus congolensis from the Nile catfish Clarias gariepinus. The body wall muscles are composed of an outer layer of compactly arranged circular fibres, an intermediate layer of paired longitudinal fibres and an inner layer of well-spaced bands of diagonal fibres arranged in two crossed directions. The central nervous system consists of paired cerebral ganglia from which three pairs of longitudinal ventral, lateral and dorsal nerve cords arise. The nerve cords are connected at intervals by many transverse connectives. Both central and peripheral nervous systems are bilaterally symmetrical and better developed ventrally than laterally and dorsally. Structural and functional correlates of the neuromusculature of the pharynx, haptor and reproductive tracts were examined. Results implicate acetylcholine, FMRFamide-related peptides and serotonin in sensory and motor function. The results were compared with those of Macrogyrodactylus clarii, a gill parasite of the same host fish C. gariepinus.

The adult of Pseudoleptobothrium aptychotremae Young, 1967 (Monogenea, Microbothriidae) is redescribed from the dermal denticles of the southern fiddler ray, Trygonorrhina fasciata (Rhinobatidae) collected off Adelaide, South Australia. This is a new host and locality record. The anatomy of the larva is described from observations of live larvae and the presence of six needle-like spicules in the larval haptor is confirmed. The development of P. aptychotremae is also described.

New taxa are proposed for Nanopolystoma lynchi n. g., n. sp. from the urinary bladder and phallodeum of the caecilian Caecilia cf. pachynema and N. brayi. n. sp. from the urinary bladder of C. gracilis, both from South America. These are the first species of polystomatids to be described from caecilian hosts. The parasites are small with a maximum body length of 2 mm. The two gut caeca are not confluent posteriorly and have neither diverticula nor anastomoses. The haptor bears six well-developed suckers and one pair of hamuli. The single follicular testis lies in the mid-body and the ovary is small. Vaginae are present. A single large, operculate egg lies in the short uterus, which leads to an armed genital bulb. Neither the nature of the oncomiracidium nor the phylogenetic position of these worms is known. Nanopolystoma n. g. shares various morphological features with other polystomatid genera; however, the non-confluent gut-caeca lacking diverticula and the presence of skeletal elements in the haptoral suckers place it with the chelonian polystomes of the subfamily Polystomoidinae. These findings suggest that the caecilian host species are probably semi-aquatic. More polystomatid species are expected to be found in association with other species of Caecilia.

One new species of diplectanid monogenean, Pseudorhabdosynochus summanoides n. sp., is reported and described from the marine fish Epinephelus coioides off Nan’ao Shenzhen, China. P. summanoides differs from its closest relative, P. summanae (Young, 1968), by the shape of its vaginal hard-parts, which have a tightly twisted distal region and an accessory patch on the proximal curve. During the course of this work, type-material of several species of Pseudorhabdosynochus was examined and aspects of the vagina and haptor are redescribed and/or figured. These species include P. americanus (Price, 1937), P. hargisi (Oliver & Paperna, 1984), P. amplidiscatus (Bravo-Hollis, 1954), P. epinepheli (Yamaguti, 1938), P. riouxi (Oliver 1986), P. melanesiensis (Laird, 1958), P. cupatus (Young, 1969), P. bocquetae (Oliver & Paperna, 1984), P. kritskyi Dyer et al., 1995, P. capurroi Vidal-Martinez, 1998, P. querni (Yamaguti, 1968) and P. summanae (Young, 1969). Several closely related species are considered in terms of their conspecificity: P. hargisi is proposed as a junior synonym of P. americanus; P. capurroi is suggested as a likely synonym of P. kritskyi; and it is suggested that P. cupatus and P. bocquetae may eventually be demonstrated to be consepcific with P. melanesiensis.

Myliocotyle borneoensis sp. n. and M. multicrista sp. n. (Monocotylidae: Heterocotylinae) are described from the gills of the mottled eagle ray, Aetomylaeus maculatus (Gray), and the banded eagle ray A. nichofii (Bloch et Schneider) (Mylio- batidae), respectively, collected from the northern coast of Malaysian Borneo. These are the first monogeneans to be described on elasmobranchs from Borneo. The formerly monotypic Myliocotyle (for M. pteromylaei) was distinguished from other mono- cotylids by the distribution and morphology of the eight sclerotised dorsal haptoral accessory structures and the morphology of the male copulatory organ. However, we have determined that M. pteromylaei has ten structures on the dorsal surface of the haptor. Myliocotyle borneoensis is distinguished from M. pteromylaei by the morphology of the male copulatory organ and its accessory piece. Myliocotyle multicrista has 12 sclerotised dorsal haptoral accessory structures and a male copulatory organ with two accessory pieces. Additional sclerotised ridges across the ventral surfaces of each loculus (except the posterior-most pair) are also present in M. multicrista. The diagnosis for Myliocotyle is revised given our discovery of additional dorsal haptoral accessory structures in the type species and to accommodate other new characters of the two new species. Anterior secretions of Myliocotyle are discussed.

We propose Listrocephalos n. gen. (Monogenea: Capsalidae: Entobdellinae) for 2 new capsalid species that infect the skin of 2 species of diamond stingrays (Dasyatidae) in the Gulf of California. We also provide additional observations on 2 previously described capsalid species, which infect the external body surface of stingrays and are currently in Entobdella Blainville in Lamarck, 1818, and transfer them to the proposed new genus. The members of this genus, Listrocephalos corona (Hargis, 1955) n. comb. (type species), Listrocephalos guberleti (Caballero and Bravo-Hollis, 1962) n. comb., Listrocephalos kearni n. sp., and Listrocephalos whittingtoni n. sp., differ from other entobdellines by the combination of having an anterolateral adhesive pad comprising 2 ventral columns of raised ovoid structures, 1 pair of glands that flank the preoral depression, a discoid and aseptate haptor that lacks a marginal valve but has clover-shaped papillae dispersed radially over its entire ventral surface, minute and nonoverlapping median haptoral sclerites, a bizarre chamber yielding a duct that opens on the surface of the penis, separate genital pores, and a gland of Goto located between the testes and ovary. Listrocephalos kearni n. sp. infects Dasyatis brevis and is most easily distinguished from its congeners by the combination of lacking penis tubules and having a convoluted proximal portion of the vas deferens that occupies the space between the ootype and ovary. Listrocephalos whittingtoni n. sp. infects Dasyatis longa and is most easily distinguished from its congeners by the combination of having penis tubules and a vaginal pore that is located posterior to the level of the uterus. We report specimens of L. corona from the ventral body surface of Dasyatis say from a new locality, Mississippi Sound, as well as specimens of L. guberleti from the skin of 2 new hosts, Urobatis maculatus and Urobatis concentricus, and a new locality, Elkhorn Slough, California. We provide a diagnostic key and a table of records for Listrocephalos spp.

The seasonal dynamics of Gyrodactylus rhodei, a monogenean ectoparasite of bitterling (Rhodeus sericeus), was studied from June 2000 to May 2001 in the Kyjovka River, Czech Republic. A negative relationship between prevalence and intensity of infection of G. rhodei and water temperature was found. Metrical variability of the hard parts of the parasite haptor was studied throughout the sampling season. A negative relationship between water temperature and the size of the hard parts of the G. rhodei haptor was evident in the measurements of the total length of the marginal hooks, the sickle length of marginal hooks, anchors, anchor point and root, the width of the ventral bar and the membrane processes. Sequences of the partial ITS (rDNA) of specimens collected during the cold and warm seasons were analysed. Sequences of all studied parasite specimens were identical and there was no evidence of intraspecific variability in the sequenced region.

Spicocleidus n. g. is proposed for S. namae n. sp., a new monogenean collected from the gills of an ambassid, Chanda nama (Ham.), in the River Sai near Lucknow, Uttar Pradesh, India. The new genus is characterised by a pair of modified dorsal anchors (spikes), the absence of a dorsal bar, alate lateral expansion of the anterior haptor and the post-ovarian position of the testis.

Mormyrogyrodactylus gemini gen. et sp. n. (Gyrodactylidea: Gyrodactylidae), a viviparous monogenean is described from the skin and fins of Marcusenius macrolepidotus (Peters) from South Africa. This new genus is unique in having a large cup-shaped cirrus armed with one large needle-like spine and numerous small hair-like spinelets. A peduncular bar is present. The haptor is clearly demarcated from the body and situated on a small pedicle. The haptor has one pair of large anchors, a ventral bar complex, a small dorsal bar and 16 evenly spaced marginal hooks. The ventral bar complex consists of three parts: an inverted U-shaped piece with two semi-attached bars, each bar consisting of a base and an extension. An accessory inverted T- shaped sclerite is present on the posterior rim of the haptor. Mormyrogyrodactylus is the fifth genus of the Gyrodactylidae to be described from Africa.

Caballerocotyla lenti n. sp. (Monogenea: Capsalidae), recovered from the gills of Auxis thazard (Lacépède) captured off the coast of Rio de Janeiro, Brazil, is described using light and scanning electron microscopy. The new species is characterized by: a tegument with 2-5 rows of dorso-marginal, unicuspid spines; 53-54 round testes; a constricted pharynx with numerous papillae on its border; and a haptor with a plicate marginal border, a central polygonal area and seven complete septa. C. manteri (Price, 1951) and C. gouri Chauhan, 1953 sensu Murugesh (1995) are figured and commented upon.

Neoheterobothrium chilensisn. sp. (Monogenea: Diclidophoridae) from the gills of the bigeye flounder Hippoglossina macrops (Paralichthyidae: Pleuronectiformes) from northern Chile (308119S, 718519W) is described and compared with the known species in the genus. Diagnostic characters include the position of the seminal receptacle, the number of hooks in the male copulatory organ, the number of testes, and the relative size of the clamp peduncles. 0.45) long by 0.41 (0.30-0.49) wide; fourth pair 0.45 (0.29-0.52) long by 0.41 (0.29-0.50) wide. Peduncles 0.95 (0.35) long, slender, 0.16 (0.04) wide. First pair of peduncles usually longer than the remainder. Terminal lappet with 1 pair of small hooks (Fig. 5). Pair of oral suckers oval, 0.13 (0.03) long, 0.09 (0.02) wide. Mouth terminal; pharynx ovoid, 0.15 (0.03) long, 0.07 (0.02) wide. Intestinal ceca extending into haptor, with numerous lateral branches. Intestinal bifurcation at the level of the male copulatory organ. Peripheral intes- tinal branches not observed. The number of testes was 105 on an av- erage (range 75-125), spherical, postovarian, intercecal. Male copula- tory organ 0.057 (0.018) in diameter, armed with 11 curved hooks, each with bifid base (Fig. 3). Ovary inverted C-shaped, seminal receptacle ovate, preovarian. Ootype not observed in toto, but in the serial section between the lobes of the ovary (Fig. 4). Oviduct forms an inverted ''U'' duct that joins the ootype. Vitelline follicles coextensive with intestinal ceca, not penetrating haptor. Vitelline ducts join anterior to the ovary, forming the main vitelline duct. Main vitelline duct joins the seminal duct before the genito-intestinal canal. One egg observed; egg with 2 polar filaments; total length, including filament, 0.77; distal filament 0.04 long; proximal filament 0.47 in length.

Polystoma dawiekoki n. sp. is described as a new species of the Polystomatidae parasitic in the urinary bladder of the plain grass frog Ptychadena anchietae. This parasite was collected at Mkuze town and Mkuze Game Reserve in northern Kwazulu-Natal Province, in the Kruger National Park in Mpumalanga Province, South Africa, and at Bulwa in Tanga Province, East Usambara Mountains, Tanzania. It is distinguished from other African Polystoma species by a combination of characters, including the body size, size and shape of marginal hooklets and the haptor length to body length ratio. The presence of adult, as well as subadult, parasites in the same individuals, as is known for Eupolystoma, represents a significant evolutionary departure from the pattern of transmission typical of Polystoma in most of the other anuran hosts.

The African clawed frog Xenopus laevis (Anura: Pipidae) is host to more than 25 parasite genera encompassing most of the parasitic invertebrate groups. Protopolystoma xenopodis Price, 1943 (Monogenea: Polystomatidae) is one of two monogeneans infecting X. laevis. This study focussed on the external morphology of different developmental stages using scanning electron microscopy, histology and light microscopy. Eggs are released continuously and are washed out when the frog urinates. After successful development, an active swimming oncomiracidium leaves the egg capsule and locates a potential post-metamorphic clawed frog. The oncomiracidium migrates to the kidney where it attaches and starts to feed on blood. The parasite then migrates to the urinary bladder where it reaches maturity. Eggs are fusiform, about 300 μm long, with a smooth surface and are operculated. Oncomiracidia are elongated and cylindrical in shape, with an oval posterior cup-shaped haptor that bears a total of 20 sclerites; 16 marginal hooklets used for attachment to the kidney of the host and two pairs of hamulus primordia. Cilia from the 64 ciliated cells enable the oncomiracidium to swim for up to 24 h when the cilia subsequently curl up, become non-functional and are shed from the body. The tegument between the ciliated cells bears a series of sensory papillae. The body of the mature parasite is elongated and pyriform and possesses an opisthaptor armed with three pairs of suckers and two pairs of falciform hooks to ensure a firm grip on the flexible internal surface of the urinary bladder.

The monotypic Philureter n. gen. (Ancyrocephalinae; Dactylogyridae) is proposed to accommodate Philureter trigoniopsis n. sp. with the following features: presence of a cuplike ventral haptor armed with 14 hooks and 2 anchor/bar complexes; dorsal pair of anchors poorly defined and variable in shape, 1 frequently absent; tandem, intercecal gonads, testis bilaterally lobulated. Philureter trigoniopsis n. sp. is described from the ureters and urinary bladder of Galaxias maculatus (Jenyns, 1842) (Osmeriformes) in Patagonian Andean lakes, Argentina.

Acanthoplacatus gen. nov., a new genus of viviparous gyrodactylid, is described from the rns and skin of siganid fishes from the Great Barrier Reef, Australia. The genus is characterized by a muscular, tube-like haptor with 16 marginal hooks on the posterior margin. The ventral lobe of the haptor is located anteriorly relative to the dorsal lobe and contains a pair of hamuli and a ventral bar with posteriorly-projecting ventral bar membrane. A dorsal bar is absent. Five pairs of posterior gland cells surround the posterior terminations of the gut. The male copulatory organ is a muscular, non-eversible bulb with several spines around the distal opening. Species of Acanthoplacatus have a bilateral excretory system consisting of six pairs of flame cells and a pair of excretory bladders. Seven new species are described: Acanthoplacatus adlardi sp. nov. and A. amplihamus sp. nov. from Siganus punctatus (Forster, 1801), A. brauni sp. nov. from S. corallinus (Valenciennes, 1835), A. parvihamus sp. nov. from S. vulpinus (Schlegel and Mueller, 1845), A. puelli sp. nov. from S. puellus Schlegel, 1852, A. shieldsi sp. nov. from S. lineatus (Valenciennes, 1835) and A. sigani sp. nov. from S. fuscescens (Houttuyn, 1782). Species can be discriminated by shape and size of the hamuli, marginal hooks and ventral bar and by male copulatory organ sclerite morphology. Three species (A. brauni sp. nov., A. shieldsi sp. nov. and A. sigani sp. nov.) were assessed for seasonal variation of sclerite size. Ten of thirteen morphological characters showed seasonal variation in size for at least one of the species. The characters were longer in winter except dorsal root tissue cap width. Only one character, marginal hook length, showed significant seasonal variation for all three species. Species of Acanthoplacatus were observed to attach using only the marginal hooks and the role of hamuli in attachment is unclear. The dorsal rn of the host is the preferred site for most species but the anal fin, caudal fin and body surfaces are preferred by some species. Prevalences for species range from 57 to 100%.

When oncomiracidia of Neobenedenia girellae (Monogenea, Capsalidae) were incubated in wells with lyophilized extracts of fish skin epithelia on the bottom, some attached to the well bottom with the haptor unfolded and shed the ciliated epidermal cells. Based on these morphological changes in oncomiracidia, we developed a new assay method to examine the attachment-inducing capacities of various fish extracts for oncomiracidia. Attachment-inducing capacities were found only in extracts of fish skin epithelium and not in other fish extracts. No significant difference in capacities was observed among extracts of skin epithelia of 4 fish species. Wheat germ lectin and concanavalin A suppressed capacities in extracts of skin epithelia of Japanese flounder and yellowtail, respectively. Suppressed capacities were recovered by adding sugars that bound specifically to these lectins. These results indicate that some sugar-related chemical substances that exist specifically in fish epithelium induce the attachment of N. girellae oncomiracidia.

Scomberomorocotyle munroi n. g., n. sp. is described from the gills of Scomberomorus munroi, a Spanish mackerel from the coasts of northern Australia and southern Papua New Guinea. The genus belongs to the suborder Gastrocotylinea because a pair of basal accessory sclerites is present in the clamps. However, the worm does not belong to any of the eight gastrocotylinean families as they are currently recognised. The worm appears to be a member of the Thoracocotylidae, in that the male copulatory organ has relatively weakly developed spines, and that the haptor is one-sided with two rows of clamps. However, the worm differs from all thoracocotylids in that the clamps lack the characteristic lateral rib-like thickenings. To accommodate the new genus and species, the diagnosis of the Thoracocotylidae Price is amended to include worms lacking ribs in their clamps, and a new subfamily, the Scomberomorocotylinae n. subfam., is erected; a key to the four subfamilies which we recognise as valid is provided.

An earlier suggestion based on light microscopy that haptor "spicules" in the oncomiracidium of the microbothriid monogenean Leptocotyle minor are vestigial marginal hooklets is supported by their ultrastructural features. Each spicule is a solid rod of homogeneous, uniformly electron-dense material and is enclosed within a cell (or cells) (oncoblast?). We confirmed that there are six of these spicules in L. minor.

An indirect immunocytochemical technique combined with confocal scanning laser microscopy has been used to demonstrate immunoreactivities to the nonapeptide, RPPGFSPFR (bradykinin, BK) and the endogenous flatworm regulatory peptide, GYIRFamide in the nervous system of the monogenean, Diclidophora merlangi. In addition, a simultaneous double-labelling technique was employed to examine possible co-localization of GYIRFamide- and neuropeptide F (NPF) immunoreactivities, using antisera to the C-terminal nonapeptide-amide of NPF (Moniezia expansa, FAIIGRPRF.NH2). BK immunostaining was restricted to a small population of nerve cells and associated fibres within the ventral nerve cords and to 2 pairs of nerve cells innervating the cirrus and the pharynx, respectively. No immunopositive nerve cells and fibres were identified within the brain or in association with the female reproductive apparatus. In contrast, GYIRFamide staining was abundant throughout the central and peripheral nervous systems, and appeared similar to the staining pattern revealed using an FMRFamide antiserum. GYIRFamide immunoreactivity was localized to nerve cells and fibres within the paired cerebral ganglia and the longitudinal ventral, dorsal and lateral nerve cords and their numerous interconnecting transverse commissures. The plexuses of the buccal suckers, pharynx and clamps of the haptor were strongly immunopositive for GYIRFamide, as were nerve cells innervating the ootype, the oviduct and the vitelline reservoir of the reproductive apparatus. Double-labelling experiments indicated an apparent co-localization of GYIRFamide and NPF immunoreactivities.

A parasite was isolated from Coilia nasus collected from Yangtze River.Morphological(light,scanning electron microscopes)and molecular(28S rRNA amplification)methods were used to identify the species of the isolates.Their typical characteristics:haptor not clearly distinguished from body proper,provided with 4 pairs of heteromorphic clamps.Two clamps on one side are larger than other six clamps.Narrow posterior appendage with 2 pairs of sharp hooks and egg with long filament.The results of sequence alignment showed 100% homology to 28s of Heteromazocraes hexacantha.Neighbor-joining methods of phylogenetic tree also showed that the isolates were in the same clade with H.hexacantha,These results suggested that this parasite is Heteromazocraes lingmueni,and its 28S rRNA was measured for the first time in this study.

Transmission electron microscope studies of the tegument of the tropical marine fish monogenean parasite Pseudothoracocotyla indica describe surface specialisations and detail the ultrastructure of the tegument and the haptor. The tegument consists of a syncytium, numerous electron-dense granules, electron-lucent vesicles and large multivesicular bodies. The posterior tegumental syncytium is infolded to form tegumental ridges that are present on both the ventral and dorsal surfaces. A thin coat of glycocalyx is present on the tegument surface. In contrast, the tegumental syncytium of the haptor is relatively thin, containing electron-dense granules and various-sized electron-lucent vesicles. Exocytosis of the electron-dense and electron-lucent vesicles apparently occurs in the syncytium of the haptor and general body surface. Tegumental damage was observed on the dorsal surface in the mid-body region and may possibly have been due to natural mechanical forces. The haptor consists of electron-dense clamp sclerites embedded within a matrix covered by the tegumental syncytium. The sclerites are connected to each other and to the basal lamina by radially oriented muscle fibres. The haptor is richly supplied with non-myelinated nerve axons. Both uniciliated and non-ciliated presumed sensory structures are present on the body surface and haptor. Uniciliated sensory structures were found mainly around the oral sucker. Groups of neurons and nerve processes containing neurosecretory vesicles were frequently observed in the vicinity of the clamps. Electron immunogold labelling studies demonstrated that neuropeptide F [NPF (Moniezia expansa)] immunoreactivity was confined to electron-dense-cored neurosecretory vesicles in nerve fibres from the posterior and haptor regions of the fluke.

The thin, weakly muscular, disc-shaped haptor of the calceostomatine monogenean Neocalceostomoides brisbanensis is attached to surfaces in the gill chamber of its catfish host by cement. It is unlikely that any suction is generated (there are no muscular loculi) and the hooks are reduced in size. Two distinctive secretions are associated with the haptor: a finely granular secretion from glandular tissue within the haptor and anterior to it, which enters the dorsal haptor tegument near the periphery of the disc and spreads throughout the ventral haptor tegument; a coarser secretion produced in the peduncle and posterior region of the body, which finds its way to gland openings near the hamuli via centrally situated large and small haptor reservoirs. It seems most likely that the tegumentary secretion is the cement, but other possibilities are discussed. It is suggested that the increasing importance of cement for haptor attachment in calceostomatines has led to the development of a weakly muscular, foliaceous haptor and a progressive reduction of the hooks.

Allomurraytrema robustum occurs normally in low numbers on the jaws, gill arch or upper palate; juveniles also occur on the lateral margins of the gill filaments. At high levels of infection the parasite occurs in large groups (> 30 worms) on the jaws and gill arches, and extemds onto the lateral margins of the gill filaments. Large numbers of eggs become entangled among these groups of parasites. Ciliated oncomiracidia emerge from the eggs. The parasite attaches to the surface of epithelia by small hamuli and marginal haptoral hooklets, but an adbesive secretion may be invelved as well. The parasite causes little damage when attached to thick epithelia, but on the surface of the gill filaments there is erasion and degeneration of the epithelium beneath and adjacent to the haptor. Infiltrating leucocytes enter the dermis, epidermis and the host-parasite interface. Intact infiltrating cell occur in the intestinal caeca of the parasite.

The tegumental marfaces of both the bladder (normal) adult and branchial (neotenic) adult of the dimorphic monogenean Polystoma integerrimum are elevated into ridges forming a honeycomb-like pattern of hexagoas. In some regians, upright microvilli are located at the angles of the hexagoas. The two hamuli of the adult forms are sheathed with the ornamented tegument except for the naked distal spine. Larvae with haptors at the two-sucker stage of development have a tegument with the elevated honeycomb design characteristic of the adults. Developing hamuli appear as fully sheathed, conical elevations. The 16 marginal hooklets of the larval hapter are covered by tegument, with the exception of their strongly curved spines. Genetic blueprimts for normal and neotenic development, contained in the genome of all larvae hatching from the eggs of normal individuals, appear to diverge only in relation to the different rates of embryonic development of the two adult forms and the incomplete ontogeny of the neotenic adult.

At least six ancyrocephaline monogeneans, four of which are new species, are reported from the gills of the blue catfish, Arius graeffei, in the Brisbane area, Queensland, Australia, namely Chauhanellus australis (Young, 1967) Bychowsky & Nagibina, 1969, Chauhanellus youngi new species, Hamatopeduncularia pearsoni new species, Hamatopeduncularia brisbanensis Young, 1967, Hamatopeduncularia major new species and Hamatopeduncularia spiralis new species. H. major has been found so far only on catfishes from the Brisbane River (freshwater) and C. youngi and H. brisbanensis only on catfishes from Moreton Bay (salt water). H. spiralis is described from river catfishes; a similar, possibly identical parasite occurs on bay catfishes. Young's paratypes of H. brisbanensis were found to include specimens of H. pearsoni new species. Additional observations were made on the anatomy and biology of C. australis and H. brisbanensis, with special attention being paid to the haptor glands. New light is shed on the function of the marginal-hooklet-bearing haptoral tentacles of Hamatopeduncularia spp. and on the status of these tentacles in taxonomic studies. Possible evolutionary trends in these gill parasites are suggested. Consideration is given to salinity tolerances by the parasites, to possible age-related changes in host susceptibility and to genetic differences between catfishes, as explanations for differences in the distribution of these parasites on large and small hosts and on hosts from the Brisbane River and from Moreton Bay.

The subcutaneous attachment of the monogenean Heterobothrium elongatum (Diclidophoridae) in the gills of Torquigener pleurogramma (Pisces: Tetraodontidae). International Journal for Parasitology 20: 769-777. Heterobothrium elongatum predominantly occurred on the most anterior pair of gill arches of infected pufferfish, Torquigener pleurogramma. Juvenile and immature stages attached to gill lamellae and were concentrated on the ventral regions of the anterior pair of gill arches. Following penetration of subcutaneous tissues, young adult worms formed a subcutaneous channel either directly above or below the transverse septum, a tissue layer connecting the bases of adjacent gill rays. Large, sexually mature worms extended for most or all of the length of the gill arch where they filled the area normally occupied by the longitudinal lymphatic vessel (branchial vein) or lay adjacent to the efferent branchial and colateral arteries. Subcutaneous attachment by the parasite induced a marked inflammatory reaction in the host. During growth, the mid-region of the parasite became markedly elongate and formed a stalk connecting the haptor lying in the dorsal region of the gill and the body which emerged from the lower margin of the gill where penetration began.

Two species of Caballerocotyla from scombrids from Atlantic Ocean, Rio de Janeiro coast, Brazil are described: Caballerocotyla llewelyni n. sp. from gills of Katsuwonus pelamis and Caballerocotyla neothunni, from Thunnus albacares. Caballerocotyla neothunni is reported for the first time in South America. Caballerocotyla llewelyni n. sp. is most similar to Caballerocotyla foliacea, Caballerocotyla gregalis, and Caballerocotyla nozawae by lacking marginal spines and by the presence of a sessile haptor. The new species differs from Caballerocotyla foliacea, mainly by its smaller number of testes and by the presence of “cuticular” papillae on the haptor; it differs from Caballerocotyla gregalis by the haptor/body length ratio, by shape of anchors and haptor with “cuticular” papillae; and it differs from Caballerocotyla nozawae, mainly by its smaller haptor and smaller number of testes. There was no morphological differences between the descriptions of Caballerocotyla neothunni and Caballerocotyla abidjani (parasites of Thunnus albacares) when compared to our specimens of C. abidjani (also collected from T. albacares). We propose Caballerocotyla abidjani as a synonym of Caballerocotyla neothunni. Key words: Brazil, Caballerocotyla, Caballerocotyla llewelyni n. sp., Capsalidae, marine fish parasites, Monogenea, Tuna

Transmission by Gyrodactylus turnbulli occurs most frequently when its hosts (Poecilia reticulata) come into close contact. This study is the first description of a specific migratory behavior that facilitates transmission of a gyrodactylid from dead hosts. Recently-dead guppies typically float at the water's surface; G. turnbulli moves off these fish into the water film, hanging motionless with the haptor held by surface tension. Because guppies are surface feeders, detached parasites in the water film are more likely to contact a new host.

Calicobenedenia polyprioni n. sp. (Capsalidae) is described from the external surfaces (skin and eye) of wreckfish, Polyprion americanus (Teleostei, Perciformes, Polyprionidae), from the north Atlantic Ocean. The monotypic Calicobenedenia n. gen. is proposed for this species and is characterized, in part, by its members possessing an aseptate haptor armed with 14 submarginal hooks and 1 pair of anchors, a common genital pore opening marginally immediately posterior to the left cephalic lobe, 2 testes juxtaposed near the body midlength, and by lacking cephalic suckers or adhesive discs, accessory haptoral sclerites, and a uterine valve. The new genus most closely resembles Entobdella, which differs from Calicobenedenia by having an aseptate haptor armed with 14 submarginal hooks, 2 pairs of anchors, and a pair of accessory sclerites. The Capsalidae (Monogenoidea, Polyonchoinea, Capsalidea) comprises over 40 genera with about 200 species, most of which parasitize the external surfaces of marine perciforms. Some capsalids also infest fishes of the orders Rajiformes, Squaliformes, and Lamniformes (all Elasmobranchii) and Scor- paeniformes, Zeiformes, Tetraodontiformes, Pleuronectiformes, Anguilliformes, and Acipenseriformes (all Actinopterygii) in the marine environment. In this paper, a new genus and species of Capsalidae are proposed from the external surfaces (skin and eye) of wreckfish, Polyprion americanus (Bloch and Schnei- der), Polyprionidae, from the north Atlantic Ocean. The capsalid specimens described herein were collected as part of an ongoing study (master's thesis project of C.J.F) of parasite diversity and host-parasite ecology associated with wreckfish in the north Atlantic Ocean. The host is a large, deep- water, grouper-like fish from subtropical and temperate regions, including the Mediterranean Sea and the Atlantic, south Indian, and southwest Pacific oceans (Fig. 1). Adult wreckfish inhabit deep seamounts, rocky ledges, and wrecks of the continental shelf and nearby banks (Anonymous, 1995; Sedberry et al., 1996); juveniles are pelagic, but the length/age at which they in Canada balsam. The haptors of some specimens were excised and mounted individually in Gray and Wess' medium for study of haptoral sclerites; see Riser (1950), Humason (1979), and Pritchard and Kruse (1982) for fixatives, stains, and mountants. Measurements, all in micro- meters, represent straight-line distances between extreme points and are expressed as the mean followed by the range and number (n) of struc- tures measured in parentheses; body length includes that of the haptor. Type and voucher specimens are deposited in the U.S. National Parasite Collection (USNPC), Beltsville, Maryland, and the helminth collection of the University of Nebraska State Museum (HWML), Lincoln, Ne- braska, as indicated in the description of the new species. Nineteen additional lots of vouchers, not examined for the present study, are in the helminth collection of the Virginia Institute of Marine Sciences, Gloucester Point, Virginia.