Fish assemblage composition in a tributary of the Mogi Guaçu river basin, southeastern Brazil

Fish assemblage composition and seasonal patterns of species abundance were studied in Cabaceiras stream, a tributary of the Mogi Guaçu river in São Paulo State, Brazil. Three stations were sampled monthly from June 1999 to May 2000 using sieves and small trawl net and gill nets. Fifteen fish families, 37 genera and 45 species were captured. Characiformes (27 spp.) and Siluriformes (13 spp.) were the most species-rich orders. Gymnotiformes and Perciformes were represented by two species each, and Synbranchiformes had only a single species. One group of species (approximately 75 %) persisted in the stream throughout the year. A second group (approximately 25 %) contained species that only occupy the stream for a limited period of their life cycle, and overall fish assemblage composition was associated with the seasonal flood cycle.

Revisão taxonômica e relações filogenéticas das espécies de Roeboides grupo-microlepis (Ostariophysi, Characiformes, Characidae)

The Roeboides microlepis species-group is revised. Four species are recognized: R. myersii Gill, 1870 from the Amazon basin, R. microlepis (Reinhardt, 1851) from river Paraguay, middle and lower river Paraná, R. araguaito sp. nov. from the river Orinoco basin, and R. margareteae sp. nov. known only from Rio Parnaíba and Pindaré-Mearim, northeastern Brazil. The type-locality of R. microlepis is restricted to river Paraguay; R. bonariensis (Steindachner, 1879) is considered a synonym of R. microlepis. The phylogenetic analysis indicates that R. myersii and R. araguaito are most parsimoniously related and may be a sister group. These two species are here considered as sister group of the monophyletic lineage which includes R. microlepis and R. margareteae. A key to the microlepis species-group genus Roeboides is given.

Estrutura populacional e aspectos reprodutivos de Corydoras aeneus (Siluriformes, Callichthyidae) em riachos da bacia do rio Ivinhema, Alto rio Paraná

RESUMO Apesar do crescente número de estudos sobre biologia de espécies de peixes de pequeno porte, o conhecimento dos aspectos básicos da biologia da maioria das espécies ainda é incipiente. Com isso, o objetivo desse estudo foi descrever alguns aspectos populacionais e reprodutivos de Corydoras aeneus (Gill, 1858) em riachos da bacia do rio Ivinhema, Alto rio Paraná. As amostragens foram realizadas entre 2008 e 2011 em 57 riachos distribuídos na bacia. Foram analisados 684 indivíduos, sendo 213 fêmeas e 190 machos, além de 281 exemplares analisados apenas quanto aos dados de comprimento padrão. O comprimento padrão máximo da população analisada foi de 50,19 mm para as fêmeas e de 45,24 mm para machos; Desta forma, as fêmeas foram maiores que os machos. A proporção sexual foi de 52,7% para fêmeas e de 47,1% para os machos, sem variação significativa entre os sexos (Χ2= 1,313; p = 0,252). Quanto à relação peso/comprimento ambos os sexos apresentaram a crescimento isométrico. As maiores frequências de fêmeas maduras foram observadas nos meses de outubro a dezembro, embora tenham sido observadas fêmeas maduras em outros meses do ano. Estimou-se que 50% das fêmeas estão sexualmente maduras com 33,54 mm de comprimento padrão. A fecundidade média foi estimada em 359,47 oócitos, sendo que a população apresenta desova total. O padrão de recrutamento não apresentou um padrão unimodal, embora a maior intensidade tenha sido observada nos meses de outubro a dezembro. O comprimento assintótico foi estimado em 54,59 mm e a taxa de crescimento de 1,1 ano-1. O índice de performance de crescimento foi estimado em 3,51; a longevidade de 2,72 anos e a mortalidade de 1,48 ano-1.

Biologia do saguirú (Characidae, Curimatinae)

In Brazil all the fishes belonging to the sub-family Curimatinae are called « saguirú ». The present work gives a biological study of the Curimatus elegans Steind., a small fish without any economical importance, which is to be found along the whole brazilian coast, down till Paraguay. The specimens utilized for the present study come from Fortaleza (Ceará, north-eastern Brazil). The C. elegans is « ilyophagus », that means, it feeds itself exclusively with those organic materials to be found in mud, specially with microscopical algae. The intestines are very extent, some of them measuring about 9 to 11 times body's length. Studies have been made about growth and age of the C. elegans; the biggest sizes found were of 153 mm. for females and 88 mm. for males. The C. elegans shows developed sexual glands during a long period (April to September). The movements of the spermatozoa, in contact with water is of 40 to 50 seconds of intense movements, ceasing after 70 to 100 seconds. In contact with 0.5% NaCl-solution spermatozoa show a big increase in movements-time, that can last till about 25 minutes. The eggs' diameter measures 0.70 to 0.73 mm., mature and hydrated it attains 0.93 to 1,00 mm. There is a certain correlation between the size of the body and the quantity of eggs. Big specimens can produce a total of 200.000 eggs. The average quantity contained in 1 gr. and 1 cc. is 6018 and 6229 eggs, respectively. Maturity and spawning in laboratory has been obtained due to injections of suspension of fish-hypophysis. Three or four hours after the injection, fishes show more movement and evident signs of excitation, proceeding spawning after 5 to 6 hours. Males, persecuting females, describe successive circles (merry-go-round) - carroussel), swimming side by side with females up to water's surface, where sexual products are start beating dry, for there is no blood yet. Circulation-scheme is to be found on fig. 4 and 5. The swim-bladder and the stomach are but delineated; the intestine is formed by a cylindric tube, all closed. At the place, where later on there will open the mouth, we find a group of ciliary hairs that produce a liquid current, very evident by the semi-circle formed by attached solid particles. After 36 hours, opening of the mouth and formation of the gill slits begin. At the age of 90 hours (4 mm.) the larvas swim well and start to feed themselves; the digestive tube is now all open and the swimbladder works already. During the first days of life, larvas have an adhesive organ situated at their frontal region (fig. 7) in form of a crescent, by means of which they hang to surrounding vegetation (fig. 6). When the larva begins to swim and to feed itself and its yolk are having been absorbed. the adhesive organ retracts and disappears. While larvas and alevins feed themselves with plancton, they have small eye-teeth, which disappear,. when fishes become « ilyophagus ». There exist too, during their life as larvas, pharyngeal-teeth. The lateral line appears in the larva after 16 to 18 days; more or less at the same time all fins are completely developed. Shortly after, first scales appear (20 to 23 days). Evolution of intestines twisting followed (fig. 9). Larvas show at different parts of their bodies small of organs excretory functions, that are constituted by bottons in serial disposition, every one with an excretory canal that opens towards the outside. These formations disappear suddenly when larvas attain their phase of alevin. The existence of a great number of said formations at the caudal fin (fig. 12) is of great interest. In our experiences of breeding we have employed several thousands of C. elegans larvas in different environs and we made conditions of surrounding change (illumination), depth of water, temperature, presence of sand at bottom of aquariums and without sand, food). In this way we could compare the results obtained, estimate the action of each factor for the realisation of a good bring-up of larvas.

Urocleidoides astyanacis n. sp. (Mongenva ancyrocephalinae) from frescwater characidians on the genus Astyanax

A new species of Urocleidoides, U. astyanacis (Monogenea, Ancyrocephalinae) is described from the "lambari" Astyanax scabripinnis (Jenyns, 1842) and A. fasciatus (Cuvier, 1819). Hosts were collected in Atibaia and Jaguari Rivers near Campinas, São Paulo State, Brazil.

A new species of Probursata Bravo-Hollis, 1984 (Mogenea: Heteraxinidae: Heteraxininae) parasite of Oligoplites spp. (Osteichthyes: Carangidae) from the coast of the state of Rio de Janeiro, Brazil

Probursata brasiliensis n. sp., a gill filament parasite of carangid fishes, O. palometa (Cuvier), Oligoplites saurus (Bloch & Schneider), and O. saliens (Bloch), from the Brazilian coast, is described and illustrated. The new species differs from Probursata veraecrucis Bravo-Hollis, 1984, the type and only species of this genus by the presence of spines in the auricular expansions of the genital atrium, by the trifurcate supplementary process of the clamp's midsclerite, and by having a larger number of tests and clamps. This is the first record of the genus Probursata Bravo-Hollis, 1984, in the South Atlantic Ocean.

Mechanism of action of Bacillus thuringiensis toxins

The selectivity of Bacillus thuringiensis toxins is determined both by the toxin structure and by factors inherent to the insect. These toxins contain distinct domains that appear to be functionally important in toxin binding to protein receptors in the midgut of susceptible insects, and the subsequent formation of a pore in the insect midgut epithelium. In this article features necessary for the insecticidal activity of these toxins are discussed. These include toxin structure, toxin processing in the insect midgut, the identification of toxin receptors in susceptible insects, and toxin pore formation in midgut cells. In addition a number of B. thuringiensis toxins act synergistically to exert their full insecticidal activity. This synergistic action is critical not only for expressing the insecticidal activity of these toxins, but could also play a role in delaying the onset of insect resistance.

Occurrence of Sciadicleithrum mexicanum Kritsky, Vidal-Martinez et Rodríguez-Canul, 1994 (Monogenea: Dactylogyridae) in the Cichlid Cichlasoma urophthalmus from a flooded quarry in Yucatan, Mexico

Cichlids, Cichlasoma urophthalmus, collected in a flooded quarry in the Yucatan Peninsula, Mexico, from January through June 1992, had high levels of infection with the ancyrocephaline Sciadicleithrum mexicanum (Monogena: Dactylogyridade) in all montlhly samples. Neither occurrence nor maturation of the worms eshibited any pronounced monthly fluctuation. The infection rate was found to be sizedependent, greater in longer fish. The worms occurred on primary lamellae of gill filaments of all arches, with lower numbers of parasites attached to the fourth gill arch. Otherwise, there was no significant site preference of worms. Only minor histopathological changes were found at the sites of attachment, and these were restricted to the epithelial cells of the primary lamellae of thegill filaments. The lack of seasonal periodicity in this tropical monogenean is compared to seasonal cycles typical of temperate species.

Monogeneans of leatherjackets, Oligoplites spp. (Osteichthyes: Carangidae), with the description of a new species of Metacamopia (Monogenea: Allodiscocotylidae) from the coast of the State of Rio de Janeiro, Brazil

Metacamopia oligoplites n. sp., a gill filament parasite of carangid fishes of three species of Oligoplites Gill, O. palometa (Cuvier), O. saurus (Bloch & Schneider), and O. saliens (Bloch), from the coast of the State of Rio de Janeiro, Brazil, is described and illustrated. Metacamopia oligoplites n. sp. differs from M. indica by: the shape of the body; the pre-, para-, and post-germarial testes; vaginas lacking sclerotized structures; well-developed seminal receptacles; muscular sleeves around the constriction between the vaginas and the seminal receptacles; and the haptor highly asymmetric, with a large, heel-like area; and differs from M. chorinemi by: the esophagus lacking diverticles; a larger number of testes (26-55) and not just, approximately 10; and the vaginas lacking sclerotized structures of any kind. This is the first record of Metacamopia in the South Atlantic Ocean. The generic diagnosis of Metacamopia is emended. Hargicola oligoplites is reported for the first time in the South Atlantic Ocean. Oligoplites palometa and O. saliens are new host records for Hargicola oligoplites.

Behavior of Biomphalaria glabrata Say, 1818 (Gastropoda: Planorbidae): I. Morphophysiology of the Mantle Cavity

Using longitudinal and transverse anatomical sections, we observed that the three cristae of the mantle of Biomphalaria glabrata (renal, rectal and dorsolateral cristae) divide the mantle cavity into three chambers which we designated air or pulmonary chamber, water inflow chamber and water outflow chamber. Using videotape filming, we observed the inflow and outflow of air and water into and from the mantle cavity and we related their probable functions such as flotation, oxygen reservoir and transport, excreta circulation and elimination, water skeleton, and modification of specific weight. To determine whether the air bubble may function as a physical gill in this species we submitted three groups of snails to different systems in which water contained the same level of dissolved oxygen whereas the gas phases were atmospheric air, pure nitrogen or pure oxygen. We observed the following parameters: time of permanence on the surface, time of immersion, and frequency at which the snails reached the surface. These results did not demonstrate a physical gill function; morphological analysis of the mantle cavity indicates this possibility

Larval biometry of Simulium rubrithorax (Diptera: Simuliidae) and size comparison between populations in the states of Minas Gerais and Roraima, Brazil

The number of larval instars of Simulium (Hemicnetha) rubrithorax Lutz (Diptera: Nematocera) was determined using the lateral length of the head capsule. In this study 1,035 larvae, of different sizes, were measured (639 from the state of Roraima and 396 from the state of Minas Gerais). A frequency distribution analysis was carried out on the measurements of the lateral length of the head capsule to determine the number of larval instars. The limits of each instar were defined by the lower frequency of the measurements falling in a range of values, by the presence of the "egg burster" that characterizes the first larval instar, and by the developmental stage of the gill histoblast. The determination of the instar number was tested using a Student's t-test (p < 0.05), the Dyar rule and the Crosby growth rule. The results indicate the existence of 7 larval instars for this species, although this result was not in accordance to the Crosby rule. Last-instar larvae from two widely separated geographical populations (Roraima and Minas Gerais), collected in habitats with different water temperature were compared and no differences (p > 0.05) were observed between them.

Simulium (Chirostilbia) bifenestratum (Diptera, Simuliidae), a new black-fly species from the Atlantic forest, State of São Paulo, Brazil

The larva, pupa, male, and female of Simulium bifenestratum n. sp. are described and illustrated. The pupae of the new species have 10 gill filaments, thick at their base and arranged in a three-dimensional way, surrounding the head and thorax. Its pupal cocoon is peculiar, not found in any of the known Brazilian black-fly species; it is very thick and hard with two openings in the anterior region. S. bifenestratum n. sp. was collected in one stream in the Bocaina mountain chain, Atlantic forest, in São José do Barreiro county, state of São Paulo, in a high (1500 m) natural grassland. Larvae and pupae were collected on the edges of small waterfalls and in places with-high speed laminar water flow, attached to the bedrock.

Histophatology and ultrastructure of Henneguya caudalongula sp. n. infecting Prochilodus lineatus (Pisces: Prochilodontidae) cultivated in the state of São Paulo, Brazil

The histological and ultrastructural characteristics of a new species of Henneguya and the host reactions to infection by this species are reported. Henneguya caudalongula sp. n. was found in the inter and intralamellar regions of the gills of Prochilodus lineatus (Valenciennes, 1836) cultivated at Center for the Research and Management of Continental Fishing Resources located in the municipality of Pirassununga, state of São Paulo, Brazil. The plasmodia were white and round or ellipsoidal and measured 0.2 to 1 mm in length. The development of the parasite was asynchronous and the mature spores were fusiform, with a total length 71 ± 1.4 µm, body length of 16.6 ± 0.54 µm and width 4.6 ± 0.2 µm. The caudal process was 52.6 ± 1.5 µm long. The polar capsules were elongate (length 6.1 ± 0.19 µm, width 1.6 ± 0.15 µm) and of equal size. The polar filament was coiled in 10-11 turns. The prevalence of the parasite was 48.3% and did not vary significantly with the season or host size.

Myxobolus insignis sp. n. (Myxozoa, Myxosporea, Myxobolidae), a parasite of the Amazonian teleost fish Semaprochilodus insignis (Osteichthyes, Prochilodontidae)

A new myxosporean species is described from the fish Semaprochilodus insignis captured from the Amazon River, near Manaus. Myxobolus insignis sp. n. was located in the gills of the host forming plasmodia inside the secondary gill lamellae. The spores had a thick wall (1.5-2 µm) all around their body, and the valves were symmetrical and smooth. The spores were a little longer than wide, with rounded extremities, in frontal view, and oval in lateral view. They were 14.5 (14-15) µm long by 11.3 (11-12) µm wide and 7.8 (7-8) µm thick. Some spores showed the presence of a triangular thickening of the internal face of the wall near the posterior end of the polar capsules. This thickening could occur in one of the sides of the spore or in both sides. The polar capsules were large and equal in size surpassing the midlength of the spore. They were oval with the posterior extremity rounded, and converging anteriorly with tapered ends. They were 7.6 (7-8) µm long by 4.2 (3-5) µm wide, and the polar filament formed 6 coils slightly obliquely to the axis of the polar capsule. An intercapsular appendix was present. There was no mucous envelope or distinct iodinophilous vacuole.

Cytotaxonomy of Simulium cauchense Floch & Abonnenc and Simulium quadrifidum Lutz (Diptera: Simuliidae) in Brazilian Amazonia

Simulium cauchense Floch & Abonnenc and Simulium quadrifidum Lutz are widely distributed in the Amazon region and are morphologically similar at the larval and pupal stages. Chromosomally, these species are readily distinguished by the position of the nucleolar organizer, which is in the short arm of chromosome I in S. cauchense and in the long arm of chromosomes III in S. quadrifidum. They also differ by three fixed inversions. Sex chromosomes are undifferentiated in both species. Chromosomal resolution of the two species allowed us to evaluate four structural features previously used as diagnostic aids at the larval stage. Characters that distinguish larvae of the two species are the number of branches and branching patterns of the dorsal abdominal setae and the dark band on each primary fan. Branching patterns of the gill histoblasts were often diagnostic, with S. quadrifidum exhibiting more proximal branching and S. cauchense more distal branching. Sites where both species occurred sometimes had larvae with one petiole branching proximally and the other distally; in these cases examination of the chromosomes permitted assignment of the specimen to species. Pigmentation patterns of larvae, on the other hand, are highly variable. Color typically is sex linked in both species.