Larval development and reproductive strategies of Central Amazon fishes

Larval development and reproduction of 19 species of Central Amazonian fish (five cichlids, two siluriforms, one osteoglossiform and 11 characiforms) were studied over two years. Most species spawn during the flooding season. The cichlids, the siluriforms and two species of characiform are nest spawners, reproducing in the littoral areas of the floodplain. The osteoglossiform is a mouth-brooder. The remaining characiforms spawn in the river channels and show no parental care. Two main strategies explain 90% of the variability of reproductive traits found among the 19 species. The first strategy is used by riverine spawners (characiforms). They have high fecundity , high to very high reproductive expenditure (calories per spawn per wet weight of female) and spawn once a year during a short season. Their eggs vary in size from 0.06 to 0.3 mg and have intermediate to high calorific value. The second strategy is used by the cichlids and two species of characiforms. They have low fecundity, low reproductive expenditure, long spawning season, multiple spawnings per season and some of them show parental care. Their eggs vary in size from 0.4 to 1.2 mg and have an intermediate calorific content. The other three species show distinct combinations of reproductive traits, but have as common feature a high reproductive expenditure, a short annual spawning season and parental care. Patterns of larval development are correlated with egg size and adult spawning sites. Egg size explained most of variability of larval body size at hatching, pectoral fin bud, eye pigmentation, jaw formation, swim bladder inflation, onset of swimming, first feeding and maximum size attained with exclusively endogenous feeding. The pattern of blood circulation of the larvae was correlated with the spawning sites. Larvae of riverine spawners are small, utilize yolk efficiently and are relatively resistant to starvation. Newly hatched larvae of riverine spawners seem to be very sensitive to physico-chemical conditions of the floodplain lakes, but by the first feeding stage they develop some resistance to the low availability of oxygen. Larvae of littoral spawners are large, utilize yolk less efficiently, and seem to be resistant to low concentrations of oxygen. The resistance of larvae to oxygen deficiency is correlated with the development of the larval respiratory system. It is suggested that egg size of riverine spawners was selected to optimize the distance of the dispersal of the larvae in a range of floodplain lakes. Conversely, egg size of floodplain spawners seemed to be selected to optimize larval survival in the spawning lake. The results are further discussed in relation to life history models

Larval Description of Psectrogaster amazonica and Potamorhina altamazonica (CURIMATIDAE, PISCES) of Central Amazon

Larvae of Psectrogaster amazonicaand Potamorhina altamazonica,obtained by artificial fertilization, were described. The morphologic, morphometric characteristics are presented according to the classification of development. The larvae of the two species can be separated by their pigmentation patterns and myomere numbers.Foram descritas as larvas de Psectrogaster amazonicae Potamorhina altamazonica,obtidas por fecundação artificial. As características morfológicas, morfométricas foram apresentadas segundo a classificação de estádios de desenvolvimento. As larvas das duas espécies podem ser separadas pelo padrão de pigmentação e número de miômeros

EFECTO DEL AMONÍACO SOBRE EL CRECIMIENTO DE LA GAMITANA Colossoma macropomum (Cuvier, 1818)

El efecto de la concentración de amoníaco sobre el crecimiento fue probado usandosoluciones acuosas con concentraciones de 0.002 (control), 0.07 y 0.46 mg/l de NHy un control. Los peces fueron mantenidos en tanques de 500 litros con estas soluciones por un período de 2 meses. No se observaron efectos significativos del amoníaco sobre el crecimiento de la gamitana en este período. Se concluye que la gamitana es una especie muy tolerante y que puede ser mantenida en concentraciones de amoníaco de 0.46 mg/l sin comprometer su crecimiento

Kelet-Közép-Európa a digitális selyemúton? : Lehetséges politikai gazdaságtani magyarázatok

A kelet-közép-európai térség országai eltérő módon viszonyulnak ahhoz a kérdéshez, hogy bevonják-e – és ha igen, milyen mértékben – a kínai technológiai vállalatokat digitális átalakulásukba. A tanulmány központi kérdése éppen ezért az, hogy hogyan és miért reagálnak ezen országok eltérően Kína digitális selyemút kezdeményezésére. Az eltérő válaszok magyarázatára négy hipotézist fogalmazunk, majd vizsgálunk meg, figyelembe véve regionális, globális és nemzeti szintű tényezőket. Először azt a feltételezést vizsgáljuk, mely szerint a kapitalizmus helyi változata hatással van a vizsgált országok külpolitikai preferenciáira. Ezt követően elemezzük, vajon a 2008-as gazdasági válság nyomán Európában kialakult új mag–periféria törésvonal késztethette-e arra a kormányokat, hogy EU-n kívüli szereplők felé forduljanak. Teszteljük továbbá a kölcsönös gazdasági függésre és a biztonsági aggályokra vonatkozó nemzetközi politikai gazdaságtani meglátásokat. Végül azt a feltételezést is megvizsgáljuk, hogy az infrastrukturális fejlettség tekintetében elmaradottabb országok hajlamosabbak lehetnek-e Kínát bevonni infrastrukturális fejlesztéseikbe

Número de vértebras de characiformes do rio Amazonas e seu uso na identificação de larvas do grupo

Vertebras numbers are related to mymere numbers, consequently are a useful tool for identifying the species of fish larvae. We present here vertebrae counts and estimations of the number of myomeres for 29 species of Characiformes which have their reproduction linked to the Amazon river. We also analyse the potencial of vertebrae counts for the identification of the larvae

The larval diet of Mylossoma aureum and M. duriventre in Central Amazon

Mylossoma aureum and M. duriventre are two abundant species in the Amazon floodplain, but little is known about their larval ecology. Here, it is described the diet of 4,5 to 16mm long larvae sampled in the river and in five lakes along the Amazon. The larvae were caught with ichthyoplankton net and hand net in the main mesohabitats of the river and flood-plain. The stomach content of both species were analyzed by lake and larval size, and the contribution of the food particles accessed by their dry weight (µg). It was found that the fish fed primarily under the floating grass mats and rarely in river mesohabitats. The foremost food of both species were, initially, ciclopoid copepods and later chironomid larva. The main sources of variation in the proportion of food items in the diets were the lakes and larval length. Both species consumed particles smaller than 50% of their mouth gap. Great lenght food ingestion result in smaller amount of preys in the larva alimentary tract.Mylossoma aureum e M. duriventre são duas espécies abundantes na várzea do rio Solimões/Amazonas, entretanto, pouco se conhece sobre a ecologia de suas larvas. Aqui, são descritas as dietas de larvas de 4,5 a 16 mm de comprimento padrão, no rio e em cinco lagos de várzea. As capturas foram feitas com rede de ictioplâncton e rede de mão nos principais mesohabitats do rio e da sua planície de inundação. A contribuição relativa dos alimentos foi analisada pelos seus pesos secos no conteúdo estomacal. Os mesohabitats e o comprimento das larvas foram considerados na avaliação da dieta. Verificou-se que as duas espécies alimentaram-se com maior intensidade nas áreas inundadas, principalmente nos capins aquáticos, e raramente no canal do rio. Os alimentos que mais contribuíram nas dietas foram os copépodos ciclopóidos e os quironomídeos. As principais fontes de variação na composição da dieta foram os locais de captura e o comprimento da larva. Tanto as larvas de M. aureum como as de M. duriventre consumiram alimentos cujas larguras não ultrapassaram 50% do diâmetro de abertura bucal e larvas que ingerem alimentos maiores apresentam uma menor quantidade de presas no trato alimentar

Reproduction and early life history of Hoplias malabaricus in Central Amazon

Hoplias malabaricus is a predator fish widely distributed in South America. It is found frequently in the Amazon but its biology in the region is relatively unknown. We present here a description of its reproduction and early life history in a floodplain lakes of Rio Solimões. The fecundity of H. malabaricus is relatively low and increases with fish size. The mean diameter of ripe ovocytes are 1.5 mm. Egg masses were found in the edges of the floodplain littoral. The larvae hatched with 4.7 mm of length and details of its larval development is here presented.Hoplias malabaricus, ou traíra é um peixe predador com ampla distribuição na América do Sul.E encontrado com frequência na Amazônia, porém sua biologia ainda é pouco estudada na região. Nesta nota apresentamos dados relativos a sua reprodução e ao início do seu desenvolvimento larval na várzea do rio Solimões. A traíra se reproduz durante todo o ano. As fêmeas têm fecundidade relativamente baixa, que varia conforme o tamanho do peixe. Os ovócitos maduros são grandes (média = 1,5 mm). Ovos fecundados foram encontrados em posturas nas margens dos lagos de várzea. As larvas eclodiram com 4,7 cm de comprimento e detalhes sobre seu desenvolvimento embrionário são apresentados