Taxonomic study of Ascocotyle (Phagicola) longa Ransom, 1920 (Digenea: Heterophyidae) and related taxa

Species of Ascocotyle Looss, 1899 (subgenus Phagicola Faust, 1920) (Digenea: Heterophyidae) related to A. (P.) longa Ransom, 1920, i.e. those with a bipartite gonotyl and a single crown of 16 circumoral spines, were revised on the basis of examination of type and voucher specimens. The species A. (P.) arnaldoi Travassos, 1929, A. (P.) byrdi (Robinson, 1956) and A. (P.) longicollis (Kuntz & Chandler, 1956), all possessing 16 circumoral spines, are synonymised with A. (P.) longa. A. (P.) ascolonga Witenberg, 1929, the types of which were not available, is provisionally retained as a valid species despite its close similarity to A. (P.) longa (identical number of circumoral spines and morphology of the ventrogenital sac). It differs from A. (P.) longa in the presence of uterine loops posterior to the testes and intestinal caeca ending anterior to the ovary (versus the pretesticular uterus and intestinal caeca reaching to the posterior margin of the ovary in A. (P.) longa). A. (P.) inglei (Hutton & Sogandares-Bernal, 1959), found only once in a single specimen, is also tentatively considered a valid species because it differs in number of circumoral spines (19), slightly larger eggs (23–26×13–16 m) and the distribution of refractile bodies of the gonotyl arranged in four separate groups from A. (P.) longa and A. (P.) ascolonga (16 circumoral spines; eggs 15–20×–12 m; refractile bodies in two groups).     

Taxonomic status, redescription, and surface ultrastructure of Ascocotyle (Phagicola) pindoramensis n. comb. (Digenea: Heterophyidae)

Pygidiopsis pindoramensis Travassos, 1928, is redescribed from the holotype and specimens obtained from experimental infections of hamsters with metacercariae of the naturally infected poeciliids Poecilia vivipara and Phalloptychus januarius from Rio de Janeiro, Brazil. Ascocotyle (Phagicola) pindoramensis (Travassos, 1928) n. comb. is proposed, based on the presence of a solid, tapering muscular posterior prolongation of the oral sucker and Ascocotyle (Phagicola) mollienisicola (Sogandares-Bernal and Bridgman, 1960) is synonymized with A. (P.) pindoramensis because of the identical morphology and measurements of adults and metacercariae, similar spectrum of fish intermediate hosts (poeciliids), and the same site of infection of the metacercariae. Trematodes designated as Pygidiopsis pindoramensis, previously reported from Argentina and Mexico, represent another species of Pygidiopsis Looss, 1907, because they possess circumoral spines and their oral sucker is devoid of the posterior muscular prolongation. Data on the surface morphology of metacercariae and adults of A. (P.) pindoramensis are inferred from scanning electron microscopy observations.     

On the morphology of Acanthostomum spiniceps (Looss, 1896) and A. absconditum (Looss, 1901) (Digenea: Cryptogonimidae: Acanthostominae) with particular reference to the juvenile stage

The morphology of juvenile and adult stages of Acanthostomum spiniceps and A. absconditum, from bagrid fish of the river Nile in Egypt, was studied with both light and scanning electron microscopy. In early juveniles, circumoral spines are absent and the entire body surface is covered with tegumental spines. Late juveniles show gradual differentiation of the circumoral tegument into a collar of spines associated with a reduction in density of tegumental spines at the posterior extremity of the body. Genital primordia appear when juveniles are about 1.75 mm long. The distributions of tegumental spines on adult A. spiniceps and A. absconditum are similar. Spines are denser on the dorsal and ventral surfaces of the anterior and middle parts of the body and less dense towards the posterior end. The tegumental fold surrounding the ventral sucker of A. absconditum has spines while the fold of A. spiniceps lacks them. The most important morphological features differentiating both species are the number of circumoral spines, body shape, ratio of body length to width, sucker sizes, and the presence or absence of spines on the ventral sucker.     

Redescription of Ascocotyle (Ascocotyle) felippei Travassos, 1928 (Digenea: Heterophiydae) with new synonymies

The heterophyid trematode Ascocotyle (Ascocotyle) felippei Travassos, 1928, is redescribed and new data on its life cycle are provided, based on types and metacercariae found in the heart bulb and gills of naturally infected guppies, Poecilia vivipara (new fish intermediate host), from a coastal lagoon in Rio de Janeiro, Brazil. Examination of the type and all voucher specimens of A. (A.) felippei collected by Travassos in the type host and locality in Brazil has shown that they possess only 32 (16 + 16) circumoral spines, rather than 36 (18 + 18) spines as previously reported. Based on the identical number and arrangement of circumoral spines, shape of the body, the presence of a long preoral lobe and posterior muscular prolongation of the oral sucker, short and wide ceca, a simple gonotyl lacking refractile bodies, and the site of infection of metacercariae (predominantly heart bulb), A. (A.) puertoricensis Price, 1932 and A. (A.) tenuicollis Price, 1935, are proposed as new synonyms of A. (A.) felippei.     

Tegumental ultrastructure of the juvenile and adult Himasthla alincia (Digenea: Echinostomatidae)

The tegumental ultrastructure of juvenile and adult Himasthla alincia (Digenea: Echinostomatidae) was observed by scanning electron microscopy. One-, 5- (juveniles) and 20-day-old worms (adults) were harvested from chicks experimentally fed metacercariae from a bivalve, Mactra veneriformis. The juvenile worms were elongated and curved ventrally. The head crown bore 31 collar spines, arranged in a single row. The lip of the oral sucker had 12 paired, and 3 single type I sensory papillae, and the ventral sucker had about 25 type II sensory papillae. The anterolateral surface between the two suckers was densely packed with tegumental spines with 4-7 pointed tips. The adult worms were more elongated and filamentous, and had severe transverse folds over the whole body surface. On the head crown and two suckers, type I and II sensory papillae were more densely distributed than in the juvenile worms. Retractile brush-like spines, with 8-10 digits, were seen on the anterolateral surface, whereas claw-shaped spines, with 2-5 digits, were sparsely distributed posteriorly to the ventral sucker. The cirrus characteristically protruded out, and was armed with small spines distally. The surface ultrastructure of H. alincia was shown to be unique among echinostomes, especially in the digitation of its tegumental spines, the distribution of sensory papillae and by severe folds of the tegument.     

Tegumental ultrastructures of Paragonimus iloktsuenensis according to the developmental stages

A scanning electron microscopic study was performed to observe the tegumental ultrastructures of Paragonimus iloktsuenensis according to its developmental stages. The metacercariae were obtained from the liver of the brackish water crab, Sesarma dehaani. Juvenile and adult P. iloktsuenensis were recovered from the experimental rats on 2, 4 and 8 weeks after infection. The findings were summarized as follows: 1. The excysted metacercariae were characteristically gourd-shape, with their whole body surface beset with numerous spade-shape spines. The large, type II sensory papillae (non-ciliated round swellings) were arranged along the rim of the oral and ventral suckers, 11-12 and 6-8 in numbers respectively. 2. Two-week old juvenile worms, recovered chiefly from the liver of the experimental rats, were slender in body shape, with their ventral sucker near the anterior one-third level. The distribution of tegumental spines was less dense than in the excysted metacercariae. The spines were with 1-2 pointed tips and 3-4 longitudinal splits. Numerous ciliated knob-like, type I papillae were observed in both sides of the oral sucker, and 6 large, type II papillae were arranged along the rim of the ventral sucker. 3. Four-week old worms, recovered from the thoracic cavity and/or lung parenchyme of the experimental rats, were thicker than wide in body configuration, and their ventral sucker was located near the anterior one-fourth level. The tegumental spines at ventral surface were grouped, each group with 3-5 aggregated ones. The type I and type II papillae (small-sized) were distributed chiefly around the rim of two suckers. 4. Adult (eight-week old) worms, recovered from the capsules in the lung parenchyme, were very stout, and covered densely with bearfoot-like spines. At dorsal surface, cobblestone-like cytoplasmic processes were well-developed, with many tegumental spines embedded in them. It was observed in this study that the tegument of P. iloktsuenesis continued to change and differentiate as the worms grew to be adults.     

Surface ultrastructure of juvenile and adult Acanthoparyphium tyosenense (Digenea: Echinostomatidae)

The tegumental ultrastructure of juvenile and adult Acanthoparyphium tyosenense (Digenea: Echinostomatidae) was observed by scanning electron microscopy. One- to 3-day-old juveniles and 10-day-old adults were harvested from chicks experimentally fed metacercariae from a bivalve, Mactra veneriformis. The juvenile worms were minute, curved ventrally, and had 23 collar spines characteristically arranged in a single row. The lips of the oral sucker had 7 single aciliated sensory papillae and 4 grouped uniciliated sensory papillae. The ventral sucker had 25 aciliated round swellings on its lip. The anterolateral surface between the 2 suckers was densely packed with tongue-shaped tegumental spines, and the ventral surface just posterior to the ventral sucker was covered with peg-like spines. Retractile, peg-like spines were seen on the anterolateral surface, whereas scale-like spines with round tips and broad bases were sparsely distributed posterior to the ventral sucker. The cirrus was characteristically protruding and armed with minute spines. The surface ultrastructure of A. tyosenense was unique, especially in the number and arrangement of collar spines, shape, and distribution of tegumental spines and in distribution of sensory papillae.     

First record and description of metacercariae of Curtuteria arguinae n. sp. (Digenea: Echinostomatidae), parasite of cockles Cerastoderma edule (Mollusca: Bivalvia) in Arcachon Bay, France

A new Himasthlinae species, Curtuteria arguinae, is described as metacercariae from the cockle Cerastoderma edule (L.), collected at Banc d'Arguin (southwestern France). These metacercariae encysted preferentially in the mantle and also in the foot of cockles. Encysted and chemically excysted metacercariae were studied by light microscopy and scanning electron microscopy, respectively. Excysted metacercariae were elongated and curved ventrally. They bore a 33-spine circumoral collar. Sensory papillae were arranged around the oral sucker and also symmetrically along the ventral surface body, from the collar to the acetabulum. The dorsal and ventral tegument surfaces were densely packed with similar pointed spines. The posterior end of the body was without any spines. Among the Curtuteria species described previously, only Curtuteria haematopodis Smogorjewskaja and Iskova, 1966 had the same number of circumoral collar spines. A 6-yr field survey showed that the cockle population at Banc d'Arguin was subjected to a summer infection of C. arguinae. Curtuteria arguinae phenology of infection is characterized by interannual variability and seasonality (beginning in July-August and maximum in autumn). The first intermediate and final hosts remain unknown.     

Surface ultrastructure of Heterophyes nocens (Trematoda: Heterophyidae).

The surface ultrastructure of Heterophyes nocens (Trematoda: Heterophyidae) was studied by scanning electron microscopy(SEM). The adult worms were recovered from experimentally infected cats and from a naturally infected patient. They were leaf-like, ventrally concave, and ovoid or pyriform in shape. Ciliated knob-like sensory papillae (type I) were observed in single or grouped forms on and around the oral sucker, whereas non-ciliated round swellings (type II papillae) were seen on the lip of the ventral sucker. The tegumental spines around the oral sucker were 5-9 pointed, whereas those between the two suckers were 12-17 pointed. Ventrolaterally, three groups of 5-6 type I papillae were located between the oral and ventral suckers, with single ones alternating between them. The genital sucker was protruded or depressed, depending on the contraction state of the flukes, and the gonotyl spine number ranged 50-60. The number of tip points of tegumental spines was decreased posteriorly; finally they became 1-3 pointed. On the dorsal surface, 4 groups of 4-5 type I papillae were symmetrically located on both lateral sides, and the shape and distribution of tegumental spines were similar to those of the ventral surface. Although the tegumental ultrastructure of H. nocens was generally similar to those of other heterophyids, the genital sucker morphology including the number of gonotyl spines and/or the distribution pattern of tegumental spines and sensory papillae were suggested to be the characteristic features of H. nocens.     

Surface ultrastructure of Metagonimus takahashii metacercariae and adults

A scanning electron microscopic study was performed on the surface ultrastructure of metacercariae and adults of Metagonimus takahashii. Metacercariae were collected from the scale of crucian carp (Carassius auratus), and adult flukes were harvested 1-4 weeks after infection to rats. In excysted metacercariae, the oral sucker had type I (numerous) and type II (seven in total) sensory papillae. Tegumental spines were dense and digitated into 5-7 points on the surface anterior to the ventral sucker, but became sparse and less digitated posteriorly toward the end of the body. In adults, seven type II sensory papillae were characteristically arranged around the lip of the oral sucker, and on the inner side of the lip four small and two large type I sensory papillae were symmetrically seen on each side (12 in total). Tegumental spines on anterior two-thirds of the body, were digitated with 9-12 tips ventrally and 8-13 tips dorsally. Sperms entering into the Laurer's canal were observed. The results show that the surface ultrastructure of M. takahashii is generally similar to those of M. yokogawai and M. miyatai except for the digitation of tegumental spines.     

Tegumental ultrastructure of juvenile and adult Echinostoma cinetorchis]

The tegumental ultrastructure of juvenile and adult Echinostoma cinetorchis (Trematoda: Echinostomatidae) was observed by scanning electron microscopy. Three-day (juvenile) and 16-day (adult) worms were harvested from rats (Sprague-Dawley) experimentally fed the metacercariae from the laboratory-infected fresh water snail, Hippeutis cantori. The worms were fixed with 2.5% glutaraldehyde, processed routinely, and observed by an ISI Korea DS-130 scanning electron microscope. The 3-day old juvenile worms were elongated and ventrally curved, with their ventral sucker near the anterior two-fifths of the body. The head crown was bearing 37-38 collar spines arranged in a zigzag pattern. The lips of the oral and ventral suckers had 8 and 5 type II sensory papillae respectively, and between the spines, a few type III papillae were observed. Tongue or spade-shape spines were distributed anteriorly to the ventral sucker, whereas peg-like spines were distributed posteriorly and became sparse toward the posterior body. The spines of the dorsal surface were similar to those of the ventral surface. The 16-day old adults were leaf-like, and their oral and ventral suckers were located very closely. Aspinous head crown, oral and ventral suckers had type II and type III sensory papillae, and numerous type I papillae were distributed on the tegument anterior to the ventral sucker. Scale-like spines, with broad base and round tip, were distributed densely on the tegument anterior to the ventral sucker but they became sparse posteriorly. At the dorsal surface, spines were observed at times only at the anterior body. The results showed that the tegument of E. cinetorchis is similar to that of other echinostomes, but differs in the number and arrangement of collar spines, shape and distribution of tegumenal spines, and type and distribution of sensory papillae.     

Species of Proteocephalus Weinland, 1858 (Cestoda: Proteocephalidae), parasites of coregonid and salmonid fishes from North America: taxonomic reappraisal

A taxonomic study of species of Proteocephalus Weinland, 1858 (Cestoda: Proteocephalidae), from coregonid and salmonid fishes in North America, based largely on their type specimens, was carried out. None of the taxa studied possesses obvious autapomorphies that would justify its validity. On the contrary, all species share the following diagnostic features typical of Proteocephalus longicollis (Zeder, 1800) (syn. Proteocephalus exiguus La Rue, 1911), a polymorphic and widely distributed parasite in the Holarctic: (1) a spherical or club-shaped scolex, with sublaterally situated suckers and a vestigial but distinct and relatively large apical sucker; (2) the vagina possessing a well-developed vaginal sphincter and crossing mostly ventrally the proximal part of the cirrus sac; and (3) a long, thick-walled cirrus sac, overlapping vitelline follicles medially by more than its proximal half. Accordingly, Proteocephalus pusillus Ward, 1910; P. laruei Faust, 1920; "P. obtundus" La Rue, 1920 (nomen nudum); P. arcticus Cooper, 1921; P. wickliffi Hunter and Bangham, 1933; P. parallacticus MacLulich, 1943; P. californicus Haderlie, 1950; P. salmonidicola Alexander, 1951; and P. primaverus Neiland, 1952 are considered junior synonyms of P. longicollis.     

Acanthostomum macroclemidis n. sp. (Digenea: Cryptogonimidae: Acanthostominae) from the alligator snapping turtle,Macroclemys temmincki

Acanthostomum macroclemidis n. sp. is described from specimens found in the intestine of an alligator snapping turtle Macroclemys temmincki from southern Mississippi. The most important diagnostic features of the new species are the general shape and proportions of the body, the position of the pharynx (relative length of the prepharynx and esophagus), the egg size, the relative length and position of the vitelline fields, and the number, shape, and size of the circumoral spines. The new species has a very elongated body (length-width ratio, 8.9-13.0:1), 26 circumoral spines, which are almost oval in shape, a long prepharynx and a very short (shorter than the pharynx) esophagus, a seminal receptacle situated between the ovary and the anterior testis, a uterus not extending posterior to the anterior margin of the ovary, a long-stemmed and short-armed excretory vesicle, and 2 anal openings. Some features of the external morphology, such as the suckers, circumoral spines, sensory papillae, tegumental spines, and morphology of the posterior end, are examined using scanning electron microscopy. A diagnosis differentiating A. macroclemidis n. sp. from some other acanthostomine digeneans is provided. Acanthostomum macroclemidis n. sp. is the first digenean reported from an alligator snapping turtle and represents the northernmost record of an acanthostomine from turtles.     

Two Species of Stephanostomum Looss, 1899 (Digenea: Acanthocolpidae) from Marine Fishes off Namibia,Including S. Beukelaardori n. sp.

Stephanostomum kovalevae Parukhin, 1968 from the intestine of Lophius vomerinus off Swakopmund, Namibia, is redescribed. It is characterised by its large number (c. 73-88) of circum-oral spines, its relatively very long hindbody and the vitellarium reaching close to or just overlapping the ventral sucker. S. beukelaardori n. sp., from the intestine of Zenopsis conchifera off Walvis Bay, Namibia, is described. It belongs to the group of species where the vitellarium reaches the ventral sucker, and which has c. 32-38 circum-oral spines. It is closest to S. casum (Linton, 1910), but differs in lacking the lining of prominent spines in the ejaculatory duct, probably in egg-size and in both forebody and hindbody lengths.     

A new species of Heterosentis Van Cleave, 1931 (Acanthocephala, Arhythmacanthidae), a parasite of pinguipedid fishes in the southwest Atlantic

A new species of arhythmacanthid acanthocephalan, Heterosentis martini n. sp., parasitic in the Argentinean sandperch Pseudopercis semifasciata (Cuvier) (Perciformes, Pinguipedidae) from the coasts of Argentina is described. Heterosentis martini n. sp. differs from all congeneric species by having 10 longitudinal rows of hooks in the proboscis, each with 7-8 hooks, consisting of 1 medium apical and 3 larger sub-apical hooks with root, and 3-4 smaller, basal, curved hooks with rudimentary roots and spines in both ventral and dorsal regions of the body. The most similar species, Heterosentis heteracanthus (Linstow, 1896) Van Cleave, 1931, and Heterosentis brasiliensis Vieira, Felizardo and Luque, 2009, also have 10 longitudinal rows of hooks, but H. heteracanthus differs from the new species by having only 3-5 (more frequently 4) hooks in each row, with only the anterior hook large and bearing a developed root. Heterosentis brasiliensis differs from the new species by possessing 2 sub-apical hooks in each row (instead of 3), similar body length but shorter proboscis, and trunk spines restricted to the ventral surface of body.     

Surface ultrastructure of the gill arch of the killifish, Fundulus heteroclitus, from seawater and freshwater, with special reference to the morphology of apical crypts of chloride cells

The surface ultrastructure of the gill arches of the killifish, Fundulus heteroclitus, adapted to seawater or freshwater, was found to be similar to that reported for other euryhaline teleosts. Two rows of gill filaments (about 42 filaments per row) extended posterolaterally, and two rows of gill rakers (about 10 rakers per row) extended anteromedially from each arch. Leaf-like respiratory lamellae protruded along both sides of each filament, from its base to its apex. The distributions, sizes, and numbers of various surface cells and structures were also determined. All surfaces were covered by a mosaic of pavement cells, which measured about 7 X 4 microns and exhibited concentrically arranged surface ridges. Taste buds were especially prominent on the rakers and the pharyngeal surfaces of the first and second gill arches, but were often replaced by horny spines on the third and fourth gill arches. Apical crypts of chloride cells occurred mostly on the surfaces of the gill filaments adjacent to the afferent artery of the filament. In seawater adapted killifish, crypts resembled narrow, deep holes along the borders of adjacent pavement cells, had openings of about 2 microns2, and occurred at a frequency of about 1 per 70 microns2 of surface area. In freshwater fish, the crypts usually had larger openings (about 10 microns2), occurred less frequently (1 per 123 microns2), and exhibited many cellular projections in their interiors. Changes in crypt morphology may be related to the ion transport function of chloride cells.     

A new species of Petasiger (Digenea: Echinostomiformes: Echinostomatidae) in the brown pelican, Pelecanus occidentalis, (Aves: Pelecaniformes: Pelecanidae), from the Area de Conservación Guanacaste, Costa Rica

A new species of Petasiger inhabits Pelecanus occidentalis, from the Area de Conservación Guanacaste, Costa Rica. The new species most closely resembles Petasiger novemdecim Lutz 1929 and Petasiger caribbensis Nassi, 1980 by having 19 circumoral spines and vitelline follicles confluent between the ventral sucker and gonads. The new species differs from both of these species by having a cirrus sac that is anteroposteriorly elongate and that reaches posteriorly to the midventral sucker, an ovary and Mehlis' gland that overlap the anterior testis dorsally, a uterus that lies dorsal to the ventral sucker, and a dextromedial genital pore. In P. novemdecim and P. caribbensis the cirrus sac is round and does not extend posteriorly to the anterior margin of the ventral sucker, both the ovary and Mehlis' gland are anterior to the anterior testis, the uterus runs lateral to and not dorsal to the ventral sucker, and the genital pore opens medially and sinistromedially, respectively.     

A scanning electron microscope study on the tegument of Proalarioides kobayashii Park, 1940 (Trematoda)

A SEM study was performed on the surface of adult P. kobayashii Park, 1940, recovered from the snake, Elaphe rufodorsata. The anterior part of the worms was cup-shape and equipped with oral, ventral suckers, pseudosuckers, and tribocytic organ, and the posterior one was finger-like and round-ended. The tegument of the anterior body was covered with 3-4 pointed small spines on the mid-ventral surface and 1-2 pointed ones on the lateral surface. Sensory papillae such as type II, dome-shape ones, and papillae with an opening were distributed over the ventral surface of the anterior portion. The round tribocytic organ was bearing small stout spines laterally, whereas the surface which comes in contact with the host tissues consisted of numerous long fibrillar fibers. The lip of the oral sucker contained type II papillae. Lateral margin of the anterior body revealed type III papillae.     

Surface ultrastructure of Metagonimus miyatai metacercariae and adults

A scanning electron microscopic study was performed to observe surface ultrastructures of excysted metacercariae and adults of Metagonimus miyatai. Metacercariae were collected from the scale of the pale chub (Zacco platypus), and adult flukes were harvested 1-4 weeks after infection to rats. In excysted metacercariae, the oral sucker was devoid of tegumental spines and had type I and type II sensory papillae. Anteriorly to the ventral sucker, spines were dense and digitated into 5-7 points, whereas near the posterior end of the body spines were sparse and digitated into 2-3 points. In one-week adults, 7 type II sensory papillae were arranged around the lip of the oral sucker, and at inner side of the lip one pair of small and two pairs of large type 1 sensory papillae were seen on each side. The distribution of tegumental spines was similar to that of metacercariae, but they were more differentiated with 9-11 pointed tips. In two- to four-week old adults, the surface ultrastructure was nearly the same as in one-week old adults, however, sperms were frequently seen entering into the Laurer''s canal. Conclusively, the surface ultrastructure of M. miyatai was generally similar to that of M. yokogawai, however, differentiation of tegumental spines and distribution of sensory papillae around the oral sucker were different between the two species, which may be of taxonomic significance.