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Redescription of two cestodes (Eucestoda: Proteocephalidea) parasitic in Phractocephalus hemioliopterus (Siluriformes) from the Amazon and erection of Scholzia gen. n.

de Chambrier & Vaucher (1999) compared the proteocephalidean cestode Spatulifer maringaensis Pavanelli & Rego, 1989 from Hemisorubim platyrhynchos (Valenciennes) with similar specimens, which they described as S. cf. maringaensis, parasitising Sorubim lima (Bloch & Schneider) collected in the Paraná and Paraguay Rivers. No remarkable differences between these worms were found by these authors, except for the scolex diameter and a different infection rate in each fish host. In order to elucidate the taxonomic status of the fish cestode Spatulifer cf. maringaensis from Sorubim lima, type and voucher material of S. maringaensis from H. platyrhynchos, and voucher and new material recently collected from Sorubim lima in Argentina are described in terms of their internal morphology and tegumental surface. During the study, mature and gravid worms with smaller metascoleces were found among voucher specimens from both hosts and in the new material from S. lima. The number of testes in the type-material was difficult to assess, but it could be determined in the voucher material from the type-host as being within the range of the specimens from S. lima. Both taxa are morphologically identical and can therefore be considered as conspecific. The data on their parasitological indices support the idea that S. lima is the principal final host and H. platyrhynchos is a secondary final host. Spatulifer maringaensis is widespread throughout the Paraná basin. A comparison of the microthrix pattern of S. maringaensis with that of S. rugosa (Woodland, 1935) revealed that they have the same type of microtriches, but with a different distribution, size and density. Tumuli were observed for the first time in a Neotropical taxon. Some studies have shown that the microthrix pattern is useful for characterising and discriminating species of the Proteocephalidea, and it was used herein as a tool for determining the conspecificity of S. cf. maringaensis with S. maringaensis.

The type-specimens of Parspina argentinensis (Szidat, 1954) from Pimelodus maculatus Lacépède, and new material from Iheringichthys labrosus (Lütken), Parapimelodus valenciennis (Lütken), Pimelodella gracilis (Valenciennes), Pimelodus albicans (Valenciennes), P. argenteus Perugia and P. maculatus caught in the basins of the La Plata and Paraná Rivers, Argentina, were studied to elucidate its taxonomic status. The type-specimens of Parspina bagre Pearse, 1920 from Pimelodella metae Eigenmann in Lake Valencia, Venezuela, were also studied and new observations on its morphology recorded. The amendation of the generic diagnosis of Parspina Pearse, 1920 is proposed based on the study of both species, which revealed, among other features, the absence of a thin walled-membrane enclosing the male terminal genitalia. Parspina argentinensis is characterised by the following features: absence of a gonotyl; presence of a bipartite seminal vesicle, pars prostatica and ejaculatory duct; caeca of nearly equal length; uterus extending from the level of the ventral sucker to end of body; testes symmetrical to slightly oblique; ovary transversely elongate, compact and variable in shape; and the utilisation of a wide range of freshwater fishes as hosts. The tegumental surface of this species is covered with pectinate spines arranged quincuncially. Spines decrease in size and density from forebody to hindbody. There are two types of sensory papillae, ciliated and dome-shaped. Ciliated papillae are distributed on the surface of the oral region and on the dorsal and ventral surfaces of the body, whereas dome-shaped papillae are found on the surface of the ventral rim of the oral sucker associated with a ciliated papilla. Gland-duct openings are interspersed with the spines of the oral crown. In addition, the infection indices of P. argentinensis vary widely, not only among different hosts but also between the Paraná and La Plata River basins. Higher prevalences of P. argentinensis are recorded in the La Plata River, and Pimelodus albicans, P. maculatus and Iheringichthys labrosus are the principal final hosts in this area.

The following chaetognaths were found in the Atlantic Ocean between 34 to 40°S and 52°20' to 62°00' W: Sagitta friderici, S. tasmanica, S. minima, S. gazellae, and S. enflata (in order of abundance). Of these, only S. friderici was parasitised by unencysted metacercariae of the families Derogenidae (Derogenes sp.), Hemiuridae (Ectenurus sp.) and Fellodistomidae (Monascus filiformis), and encysted metacercariae of Lepocreadiidae. The percentage of infection for each sampling station varied from 0.033 to 0.001 in August and from 0.02 to 0.001 in October 1996, with the highest values occurring at stations closer to the coast. The intensity of infection (worms per host) varied from 1 to 3 for Ectenurus sp. and was 1 for Derogenes sp., Monascus filiformis and Lepocreadiidae. Unencysted metacercariae were found in mature developmental stages of chaetognaths, whereas encysted ones occurred mainly in juveniles. The size and length of the ovaries of parasitised and unparasitised chaetognaths did not differ significantly. This is the first report of encysted Lepocreadiidae metacercariae and a progenetic metacercaria of Ectenurus sp. in Chaetognatha from the SW Atlantic Ocean.KEY WORDS: Chaetognaths · Derogenes sp. · Ectenurus sp. · Monascus filiformis · Lepocreadiidae · Argentine Sea · Zooplankton Resale or republication not permitted without written consent of the publisherDis Aquat Org 71: [225][226][227][228][229][230][231][232] 2006 geographic areas other than those of our investigation (Furnestin 1957, Cavalieri 1963, Reimer et al. 1975). The present work examines the biodiversity, prevalence and intensity of infection of the helminths that parasitise S. friderici in the SW Atlantic Ocean. MATERIALS AND METHODSChaetognaths were collected during 2 sampling surveys carried out in the Argentinean Sea (Fig. 1). The first survey was conducted in August 1996 in the El Rincón area (38°30' to 40°30' S and 58°30' to 61°15' W) and included 18 stations that yielded 7212 specimens; the second, conducted in October 1996, at 34°to 40°S and 52°20' to 62°00' W covered 116 stations that yielded 2870 specimens. The latter survey covered 2 important breeding areas for fish: the Argentinean-Uruguayan common fishing zone (ZCPAU) to the north and El Rincón to the south. Plankton samples were fixed in 4% buffered formaldehyde in seawater. Total density (D) of chaetognats in each sampling station was calculated as D = ind. m -3 . Chaetognaths were identified according to Casanova's (1999) criteria, and each specimen was also assigned to the following maturity stages (Daponte et al. 2004):Stage 0 (juvenile): anterior and posterior fins developed, without ovaries or testes.Stage I: ovaries undergoing development containing small oocytes, testes like fine tubes, some loose spermatocytes in the basal part of the tail, seminal vesicles absent.Stage II: larger ovaries with oocytes of various sizes, spermatocytes occupying the coelom of the tail, seminal vesicles undergoing development, but still empty.Stage III: ovaries fully develop...

Nomimoscolex semenasae n. sp. is described from the primitive fish Diplomystes viedmensis (Siluriformes) from the Patagonian region of Argentina. The new species is placed in Nomimoscolex because of the cortical position of the vitelline follicles, medullary position of the testes, ovary and uterus, and having a scolex with four uniloculate suckers. N. semenasae differs from all other species in the genus by the following combination of characters: (1.apical organ absent; (2). strobila acraspedote; (3). vagina anterior or posterior to cirrus-sac and lacking a sphincter; (4). testes in one irregular layer and in two fields connected anteriorly; (5). uterine stem cortical in immature proglottides, growing from cortical stem into medullary region in mature proglottides; (6). long uteroduct; and (7). presence of spiniform microtriches on all regions of the scolex, proliferation zone and immature proglottis. This is the first record of a proteocephalidean tapeworm in D. viedmensis and in the family Diplomystidae.

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