RESUMO

INTRODUCTION: A new monogenean, Rhamnocercoides lambayequensis n. sp. (Dactylogyridea: Diplectanidae), is described based on the specimens collected from the gills of the Pacific kingcroaker Menticirrhus elongatus (Günther 1864) (Perciformes: Sciaenidae), a demersal fish endemic to Eastern Pacific, captured off the South American Pacific coast, Lambayeque Region, Peru. MATERIALS AND METHODS: Monogeneans were fixed in hot 4% formalin. Some monogeneans were transferred directly onto a slide in a drop of glycerin-ammonium picrate mixture (GAP). Others were mounted stained with Gomori's trichrome in Canada balsam. Drawings were made using of a drawing tube. RESULTS: The new species is mainly characterized by its MCO, which is tubular and straight, with external (distally expanded and bifurcated) and internal tubes (distally uncovered by external tube). Rhamnocercoides lambayequensis n. sp. is also characterized by having the following features: a weakly sclerotized almost pyriform vagina; haptoral acicular spines with expanded distal portion and by having a small group of haptoral accessory spines associated with haptoral lobes arranged as spikes. CONCLUSIONS: This is the first data on the parasites of M. elongatus, a little known, but popular fish in local markets. The present finding brings to two, the number of known species of Rhamnocercoides Luque and Iannacone 1991, and represents the sixth described marine diplectanid species infecting sciaenid fishes from Peru.

Assuntos

RESUMO

Disturbance and advertisement calls of the Argentine croaker Umbrina canosai were recorded from coastal Uruguayan waters. Dissections indicate typical sciaenid extrinsic swimbladder muscles present exclusively in males. Disturbance calls were produced when captive U. canosai were startled, chased with a net or grabbed by the tail. Calls were unusual for sciaenids because each pulse consisted of multiple cycles. The number of cycles per pulse and dominant frequency did not change with U. canosai size, but pulse duration and interpulse interval increased. Advertisement calls were recorded from unseen choruses in the field and confirmed with captive individuals in a large tank. Advertisement calls were recorded throughout the known range of the species in Uruguay indicating a continuous belt of spawning populations. Tank recordings of the same individuals permitted explicit comparisons between the two calls. Advertisement call pulses averaged 2·4 more cycles (11·0-8·6) although pulses of both calls were basically similar as were durations and dominant frequencies. Pulse number, however, differed markedly, averaging 13·6 and 3·4 pulses for disturbance and advertisement calls respectively. Furthermore, disturbance calls were produced as a rapid series with an interpulse interval of 26-31 ms whereas advertisement call patterns were less stereotyped and ranged from <100 to 450 ms. Multicycle pulses distinguished U. canosai from other sympatric sciaenids.

Assuntos

RESUMO

Visando analisar as associações entre as biomassas de peixes Sciaenidae e de camarões Penaeoidea, foram feitas amostragens com barco de arrasto nas quatro estações do ano de 2001, em um gradiente de profundidade, nas regiões de Ubatuba, Caraguatatuba e São Sebastião. Em cada transecto, foram obtidas amostras de água e de sedimento. As hipóteses de que os fatores ambientais foram diferentes entre as estações do ano e profundidades foram testadas por ANOVAs. A dependência estatística entre as biomassas de peixes (variável resposta) e as biomassas de camarões (covariável) nas três regiões, foi testada por um modelo de ANCOVA. Para quantificar as relações entre as biomassas de cada espécie foi utilizada a CCA. A importância das estações do ano e das regiões no resultado da CCA foi avaliada pelo teste de Kruskal-Wallis e da profundidade pelo teste de Spearman. Nas estações do ano, as temperaturas e salinidades foram significativamente diferentes, o que não ocorreu com matéria orgânica (MO) e o diâmetro médio do sedimento (phi = fi). Foram amostrados 378.618 g de peixes e 79.338 g de camarões, com maiores capturas no inverno e nas menores profundidades. Em Caraguatatuba foram coletadas as maiores biomassas de ambos os grupos e a correlação entre as capturas de peixes e de camarões foi negativa. Já nas demais regiões, a correlação foi positiva. Assim, os dados de Caraguatatuba foram retirados do modelo final da ANCOVA, onde 47 por cento da variabilidade na biomassa dos peixes Sciaenidae pôde ser explicada pela presença dos camarões Penaeoidea. Xiphopenaeus kroyeri foi o único fator importante na distribuição de Sciaenidae no eixo 1, enquanto o eixo 2 evidenciou indiretamente o gradiente de profundidade. Os resultados sugerem que, possivelmente, muitas espécies de peixes busquem as mesmas áreas de ocorrência dos camarões em função dos fatores abióticos ou para utilizá-los como recurso alimentar.

To study the relationships among Sciaenidae fish and Penaeoidea shrimp biomass, fieldwork was carried out in the north coast of São Paulo state, Brazil, during the four seasons of 2001. Samples were collected in transects from different depths at Ubatuba, Caraguatatuba, and São Sebastião cities. Water and sediment were collected from each transect. The hypotheses that the environmental factors were different among the seasons and depths were tested by ANOVAs. The statistical dependence among the biomasses of fishes (response variable) and the biomasses of shrimps (covariable) in the three sections was tested by an ANCOVA model. CCA was used to quantify the relationships among each species' biomass. The seasons and sections important at the CCA results were evaluated by Kruskal-Wallis test and depth by Spearman's test. The temperatures and salinities were significantly different among seasons but organic matter and phi were not. A total of 378,618 g of fish and 79,338 g of shrimp were collected and the majority was captured during the winter and in shallow transects. The greatest biomass of both groups was captured at Caraguatatuba and the correlation between fish and shrimp captures was negative. A positive correlation was found in the other areas. Therefore, data from Caraguatatuba was removed from the final ANCOVA model, in which 47 percent of Sciaenidae biomass variability was explained by the presence of Penaeoidea shrimps. Xiphopenaeus kroyeri was the only important factor in Sciaenidae distribution in the axis 1, while axis 2 indirectly evidenced the depth gradient. The results suggest that many fish species search for the same areas where shrimp occurs, related to abiotic factors, and use them as food resource.

Assuntos