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Members of the genus Kudoa are typically histozoic and only a few are coelozoic parasites, mainly in marine fishes. In the present study, 2 novel Kudoa species were recovered and described as Kudoa niluferi sp. nov. in the musculature of Neogobius melanostomus and Kudoa anatolica sp. nov. in the musculature, urinary bladder and kidney of Atherina hepsetus collected from the coast of Sinop on the Black Sea. Means ± SD (ranges) of mature spores of K. niluferi sp. nov. were 5.9 ± 0.1 (5.7-6.1) µm in length, 9.2 ± 0.2 (8.8-9.5) µm in width and 7.5 ± 0.3 (7.0-8.1) µm in thickness, while those of K. anatolica sp. nov. were 4.1 ± 0.3 (3.5-4.1) µm in length, 7.1 ± 0.2 (6.7-7.2) µm in width and 5.7 ± 0.2 (5.3-6.0) µm in thickness. In both parasite species, length and width of the 4 polar capsules were not equal and formed 3 distinct size classes, largest (1), intermediate (2) and smallest (1) in size. The prevalence and intensity of infection by K. niluferi sp. nov. were 12.8% and 20-29 parasites (per field-of-view, at 200× magnification), respectively, in the musculature of N. melanostomus. These values for K. anatolica sp. nov. were 32.1% and 10-19 parasites in the musculature as well as 2.9% and 20-29 parasites jointly in the kidney and urinary bladder of A. hepsetus. Phylogenetic analysis based on nuclear small subunit rDNA also suggested K. niluferi and K. anatolica as 2 novel species. These species appeared in the same lineage with K. nova and formed a Black Sea lineage.

To describe the histology of the digestive tract and to investigate the occurrence of endocrine cells in Oligosarcus hepsetus (O. hepsetus).The digestive tract (DT) of O. hepsetus was divided into esophagus, two stomach regions (glandular and non-glandular) and two intestinal regions (anterior and posterior). These specimens were processed by routine histological techniques and stained with hematoxylin-eosin, Gomori's trichrome, periodic acid Schiff (PAS) and Alcian blue (AB). An immunohistochemical method using avidin-biotin-peroxidase was employed.The esophagus is lined with a non-keratinized stratified squamous epithelium that is reactive to PAS and AB. The stomach has a mucosa lined with a simple columnar epithelium with mucus-secreting cells that are reactive only to PAS. The intestine has a simple columnar epithelium with a brush border and goblet cells that are reactive to PAS and AB. Somatostatin, serotonin and cholecystokinin immunoreactive cells were identified throughout the DT.This study revealed adaptations for the species' diet and showed that the distribution and relative frequency of immunoreactive cells are similar to those of other fish.

Summary Gill anomalies in three common fish species of different taxonomic order, habitat dwelling and feeding habits (one Characiformes, Oligosarcus hepsetus; one Siluriformes, Hypostomus auroguttatus; and one Perciformes, Geophagus brasiliensis) from a eutrophized tropical river in south-eastern in Brazil were compared. The aim of this study was to search for sentinel species that could be used as potential biomarkers of environmental quality. Most fish had gills with histological changes, namely epithelial lifting, interstitial oedema, leucocyte infiltration, hyperplasia of the epithelial cells, lamellar fusion, vasodilatation and necrosis. On the other hand, lamellar blood congestion and lamellar aneurysm, which are more serious and often irreversible changes, were recorded for the water column carnivorous O. hepsetus and, to a lesser extent, for the bottom-dwelling detritivorous H. auroguttatus. A histopathological alteration index (HAI) based on the occurrence and severity of gills anomalies indicated that O. hepsetus (mean score = 11.4) had significantly higher values (Kruskall– Wallis H2,41 = 15.95, P = 0.0003) compared with G. brasiliensis (mean score = 7.0). Overall, the omnivorous G. brasiliensis had comparatively lesser occurrence of most gill anomalies compared with other two species, being less suitable as biomarker of environmental quality. In contrast, the water column– dweller O. hepsetus (water column) and the bottom-dweller H. auroguttatus had gills most susceptible to changes, making them more suitable for using as histological biomarkers of the environmental quality in entrophized tropical rivers.

Coastal lagoons are important systems for freshwater, estuarine and marine organisms; they are considered important zones of reproduction, nursery and feeding for many fish species. The present study investigates the fish assemblages of the natural reserve of Dzilam and their relationship with the hydrologic variables. A total of 6 474 individuals (81 species) were collected, contributing with more than 50% considering the Importance Value Index (IVI), Sphoeroides testudineus, Fundulus persimilis, Anchoa mitchilli, Eucinostomus gula, Eucinostomus argenteus and Mugil trichodon. Differences in species composition were found between seasons the highest during the cold fronts. Spatially, differences were related with the presence of freshwater seeps, the highest in the ecological characterized eastern part and the lowest with higher difference in specific composition located in the western part of the internal zone, due to a higher abundance and dominance of L. rhomboides. Salinity and temperature were the variables that presented a higher influence in the distribution of some pelagic species such as A. mitchilli and A. hepsetus. Because of the abundant freshwater seeps characteristic of the coastal lagoons of Yucatan Peninsula their community structure and fish assemblage display spatial and temporal differences in specific composition. Rev. Biol. Trop. 57 (1-2): 89-103. Epub 2009 June 30.Las lagunas costeras son sistemas importantes para muchas especies de organismos dulceacuícolas, estuarinos y marinos, ya que son consideradas zonas de reproducción, refugio y alimentación de muchas especies de peces. El presente estudio analizó los ensamblajes de la comunidad íctica de la reserva de Dzilam y su relación con las variables hidrológicas. Se capturaron un total de 6 474 individuos (81 especies), en donde Sphoeroides testudineus, Fundulus persimilis, Anchoa mitchilli, Eucinostomus gula, Eucinostomus argenteus and Mugil trichodon contribuyeron con más del 50% del Indice de Valor de Importancia (IVI). Las diferencias en composición de especies se encontraron entre temporadas, la mayor durante los nortes. Espacialmente, las diferencias fueron relacionadas con la presencia de afloramientos de agua dulce, la mayor en la zona Este de la laguna y la menor con mayor diferencia en composición específica se localizó en la parte Oeste de la zona interna, esto debido a la gran abundancia y dominancia de una sola especie (L. rhomboides). La salinidad y la temperatura fueron las variables que presentaron la mayor influencia en la distribución de algunas especies pelágicas como son A. mitchilli y A. hepsetus. Debido a la abundancia de afloramientos de agua dulce, característicos de las lagunas costeras de la Península de Yucatán, los ensamblajes de peces muestran diferencias espaciales y temporales en la composición específica.

Six reproductive classes of male Oligosarcus hepsetus (Cuvier, 1829), a medium-sized carnivorous Characiform species, are described based on macroscopic and histological techniques. A total of 175 individuals were caught monthly between April 2001 and June 2002 in the Lajes Reservoir, Brazil, one of the largest impoundment areas in the state of Rio de Janeiro. The reproductive classes were based upon changes in the testicular morphology and stages of germinative cells, i.e., resting, early maturing, late maturing, mature, partially spent and totally spent. Fish in the resting class showed testes with spermatogonia and spermatocytes along the wall of seminal lobules, while spermatids were present in the lumina of the lobules. During early maturing, active spermatogenesis occurs throughout the testis; in the late maturing and mature classes, the lobules are swollen with sperm that are typical of fish in breeding condition. Spent testes presented seminal lobules with residual spermatozoa, coinciding with decreasing GSI and greatly reduced sperm production. Overall, the testicular morphology and class of maturity development of O. hepsetus in the Lajes reservoir did not differ significantly from those of closely related species in other lentic environments. Lower GSI values in the oligotrophic Lajes reservoir than in other eutrophic natural lakes suggest that this species may be modifying this aspect of its reproductive strategy in response to the artificial environment. Seis classes de maturação dos testículos de Oligosarcus hepsetus (Cuvier, 1829), um Characiforme carnívoro de médio porte, foram descritas com base em técnicas macro e microscópicas. Um total de 175 indivíduos foi capturado mensalmente entre abril/2001 e junho/2002 no Reservatório de Lajes, Brasil, uma das maiores áreas represadas do Estado do Rio de Janeiro. As classes reprodutivas foram estabelecidas de acordo com mudanças na morfologia dos testículos e nos estádios das células germinativas: repouso, maturação inicial, maturação final, maduro, parcialmente esvaziado e totalmente esvaziado. Os testículos da classe em repouso apresentaram espermatogônias e espermatócitos ao longo da parede dos túbulos seminíferos, enquanto as espermátides foram encontradas no lúmen dos túbulos. Nos testículos em maturação inicial, a espermatogênese é intensa; em maturação avançada e maduros, os túbulos estão repletos de sêmen, que são característicos de peixes aptos a reprodução. Testículos esvaziados apresentaram sêmen residual nos túbulos seminíferos, coincidindo com a diminuição do IGS e com uma grande redução na espermatogênese. Em geral, a morfologia dos testículos e o desenvolvimento das classes de maturação de O. hepsetus no Reservatório de Lajes não diferiram de espécies similares em outros ambientes lênticos. Os menores valores do IGS para o reservatório oligotrófico de Lajes, quando comparados com lagos naturais eutróficos, sugerem que O. hepsetus pode estar alterando este aspecto de sua estratégia reprodutiva no ambiente artificial.

We assessed spatial and seasonal changes in the diet of Oligosarcus hepsetus in order to describe the strategy developed by this species that allows their very high abundance in Lajes reservoir, Rio de Janeiro, Brazil. Fish samplings were carried out using gill nets, deployed during ca. 12 and 24 hours, between April 2001 and May 2002. A total of 289 individuals were examined, of which 97 showed gut contents. We used the index of relative importance (IRI) to compare probable dietary shifts, and the frequency of occurrence (% OC) to analyze possible ontogenetic influences on feeding. O. hepsetus showed carnivorous habits, feeding preferably on fish and insects, the latter of which occurred in 71.0% of the guts presenting contents. O. hepsetus consumed different items along the three reservoir zones: insects (61.0% IRI) and Cichla monoculus (38.9% IRI) in the lower zone; Lepidoptera (57.0% IRI) in the middle zone; and C. monoculus (77.0% IRI) in the upper zone. Food items changed seasonally with C. monoculus predominating in autumn 2001, and Hymenoptera and Lepidoptera in the winter. In spring almost all food was Lepidoptera (99.8% IRI), while in the summer Hemiptera dominated in the diet. In autumn 2002 Hemiptera (97.0% IRI) was dominant, in significant contrast with the previous autumn. Individuals smaller than 190 mm SL fed heavily on insects, while fishes predominated in the diet of individuals larger than 190 mm SL. Shifts in prey-capture ability among length classes suggest decreasing intraspecific competition. A higher food plasticity seems to be the strategy employed by this opportunist species, which used food resources available in the reservoir. Foram analisadas variações na dieta de O. hepsetus conforme comparações espaciais e sazonais, com o objetivo de descrever a estratégia desenvolvida por essa espécie que permite sua elevada abundância no reservatório de Lajes, Rio de Janeiro, Brasil. As amostras foram coletadas utilizando redes de espera com permanência aproximadamente de 12 e 24 horas, no período entre abril de 2001 e maio de 2002. Dos 289 exemplares capturados, 97 peixes continham alimento no estômago. A análise foi baseada no índice de importância relativa (IIR), enquanto eventuais influências ontogenéticas foram determinadas pela freqüência de ocorrência (% FO). O. hepsetus apresentou hábito alimentar carnívoro, alimentando-se preferencialmente de peixes e insetos. O item Insetos apresentou relevante participação na dieta, ocorrendo em 71% dos estômagos que continham alimento. O. hepsetus consumiu diferentes itens entre as três zonas do reservatório: insetos (61% IIR) e Cichla monoculus (38,9% IIR) na zona baixa; Lepidoptera (57% IIR) na zona intermediária; e C. monoculus (77% IIR) na zona alta. No geral, ocorreram diferenciações durante todo o ciclo sazonal, em que C. monoculus predominou no outono de 2001 e Hymenoptera e Lepidoptera, no inverno. Na primavera, a alimentação foi basicamente constituída por Lepidoptera (99,8% IIR), enquanto no verão, Hemiptera predominou na dieta. No outono de 2002 foi registrado 97% IIR para Hemiptera, diferindo do outono anterior. Indivíduos menores que 190 mm de comprimento-padrão (CP) consumiram preferencialmente insetos, enquanto os espécimes de maior tamanho (> 190 mm CP) alimentaram-se principalmente de peixes. Mudanças na captura de presas entre classes de tamanho sugerem diminuição da competição intra-específica. A alta plasticidade na alimentação parece ser uma estratégia usada por essa espécie oportunista, consumindo os recursos alimentares disponíveis no reservatório.

PubMedID: 12475070 Heavy metal (Cd, Cr, Cu, Fe, Pb, Zn) concentrations in the muscle, gill and liver of six fish species (Sparus auratus, Atherina hepsetus, Mugil cephalus, Trigla cuculus, Sardina pilchardus and Scomberesox saurus) from the northeast Mediterranean Sea were measured and the relationships between fish size (length and weight) and metal concentrations in the tissues were investigated by linear regression analysis. Metal concentrations (as µg/g d.w.) were highest in the liver, except for iron in the gill of Scomberesox saurus and lowest in the muscle of all the fish species. Highest concentrations of Cd (4.50), Cr (17.1) and Pb (41.2) were measured in liver tissues of T. cuculus, Sardina pilchardus and A. hepsetus, respectively. The liver of M. cephalus showed strikingly high Cu concentrations (202.8). The gill of Scomberesox saurus was the only tissue that showed highest (885.5) iron concentrations. Results of linear regression analysis showed that, except in a few cases, significant relationships between metal concentrations and fish size were negative. Highly significant (P

Spatial distribution of fish assemblages in Lajes Reservoir, a 30 km2 impoundment in Rio de Janeiro State (Lat. 22 degrees 42'-22 degrees 50'S; Long. 43 degrees 53'-44 degrees 05'W) was assessed to detect patterns of available habitat use by the fish. A standardized monthly sampling program was carried out from January to December 1994 at three zones of the reservoir (upper, near tributary mouths; middle; and lower, near the dam). Fishes were caught by gillnets, (50 m long, 3 m height), with mesh ranging having from 25 to 45 mm between knots, submerged during 12 hours. A total of 5,089 fishes were collected comprising 15 species, 14 genera and 9 families. Loricariichthys spixii, Astyanax bimaculatus, Parauchenipterus striatulus. Astyanax fasciatus parahybae, Oligosarchus hepsetus, Rhamdia parahybace, Hypostomus affinis. and Geophagus brasiliensis were the most abundant species, each contributing above 1% of the total number. Loricariichthys spixii was the dominant species, contributing over 80% of total number and biomass. Fish abundance, number of species, and biomass were higher in the upper zone, but differences from this overall pattern were shown by some species. Loricariichthys spixii and Rhamdia parahybae were more abundant in the upper zone, while all other species showed no differences in their abundance among the zones. Seasonal environmental variables of temperature, pH, transparency, and water level did not show a clear association with fish occurrence. Most fish used the different zones of the reservoir with no clear sign of spatial separation. High dominance of L. spixii. reduced abundance of reolific species Leporinus copelandii and Cyphocharax gilberti, and presence of introduced species such as Cichla monoculus and Tilapia rendallalli are indications of antropic effects in the fish community.

A new species of philometrid nematode, Philometroides africanus sp. n., is described from female specimens found encapsulated in gill arches and inner surface of gill covers of the African pike, Hepsetus odoe (Bloch), an endemic freshwater fish in Africa, from the Okavango River and Delta in Botswana. This new nematode is characterised mainly by a markedly small and plump body of gravid females (body length 6-9 mm), a separate anterior oesophageal bulb, a conspicuously small oesophageal gland, presence of four pairs of very small submedian cephalic papillae, and absence of any caudal processes. The prevalence of P. africanus in African pike of the Okavango Delta was 29%, with the intensity 1-8 (mean 3) encapsulated nematodes per fish. The genus Margolisianum Blaylock et Overstreet, 1999 is considered a junior synonym of Philometroides Yamaguti, 1935 and, consequently, its type species is transferred to the latter as Philometroides bulbosus (Blaylock et Overstreet, 1999) comb. n.