Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The Chirostoma “humboldtianum” group includes seven silverside species considered as a monophyletic assemblage because of their high genetic and morphological similarities. The group includes five moderately large species, “peces blancos” (117 - 300 mm standard length - SL) and two smaller species, “charales” (70 - 142 mm SL). These species are of great economical, cultural and ichthyological interest for local populations, and their management practices are controversial. We investigated the morphometric, meristic and allozyme variations of the seven species (13 populations) and related the variations with life history, habitat and management procedures. Nineteen morphometric variables, eight meristic variables (by multivariate analysis) and 23 allozyme loci of the seven species and populations of Chirostoma were compared. Principal component analysis (PC) of morphometric and meristic data indicate that both sets of data provided information to differentiate among the seven species. The variables that accounted for most of this differentiation were head length (HL), predorsal 1 length (P1L) and length of pelvic fin base (PfbL). PC and Discriminant Analysis (DA) with morphometric data also suggested the differentiation of populations within C. grandocule (83% correctly classified organisms), whereas PC and DA with meristic data differentiated populations of C. humboldtianum (80% correctly classified organisms). The most important morphometric variables for the differentiation were anal fin height (AfH), length of anal fin base (AfbL) and predorsal 2 length (P2L) and the meristic variables D2fR, PdS and AfR. The genetic variability data indicate changes in values of some of the species in relation to previously reported data. The present populations of C. grandocule show a reduction in He (0.002 vs. 0.009). Other species showed an increase; for instance, C. consocium consocium, C. humboldtianum, C. lucius, C. promelas and C. sphyraena averaged He = 0.069 vs. 0.027. θ indicated significant genetic differentiation among the analysed species (0.247, S.D. 0.159) and θS supported the morphological data that suggest intra-specific differentiation (0.360, S.D. 0.154).

Distribution of Micropogonias furnieri in the Sepetiba Bay, an ecosystem highly important as rearing ground for this species that represents 5.8% of the numerical catches by otter trawling, was analyzed based in monthly and bi-monthly samplings from two programmes (beach seines = continental margin; and otter trawl = inside of the Bay), over three annual cycles, between 1993 and 1997. Spatial comparisons were assessed by dividing the Bay in two zones for the beach seines (inner and outer Bay) and three zones for the otter trawl (inner, central and outer Bay), following depth, salinity and transparency gradient, as well as for the influence of the sea. Beach seines (30 m extension, a 10 m length x 2.5 m of height x 7 mm mesh) and otter trawls were used. Trawls covered 1.5 km and the boat (net mouth 8 m, mesh size 12 mm between opposites knots in the cod). Temperature (oC) and salinity (p.s.u.) were taken in each sampling; depth (m) and transparency (m) were measured during the trawl. Fish from beach seine were basically young-of-the-year; in the trawl they were individuals of larger size with total length varying from 70 mm to 300 mm. Spatially, highest CPUEs were found for the continental margin in the inner Bay, and for the inside Bay, in the inner and central zones. Highly significant correlations were detected among M. furnieri abundance and low salinity, transparency and depth in the inner Bay, with no defined pattern for the continental margin. Temporally, differences in fish abundance were shown only for the second annual cycle (1996) for the continental margin, with peaks in September/October.

Lipid composition of Heterotis niloticus, Brycenus nurse, Gnathonemus cyprinoides and Sarotherodon galilaeus, which vary in scale thickness, were studied. Heterotis niloticus (very thick scales) had the lowest lipid content (13%), while G. cyprinoids (light scales) had the highest lipid content (26%). The common neutral lipids were cholestrol, free fatty acids and cholesterol esters, while diphosphatidyl glycerol, phosphatidyl glycerol and phosphatidyl ethanolamine were the most predominant phospholipids

From November 1991 to October 1993, 980 specimens of the characid Brycinus nurse were collected from Asa reservoir to examine its diet. The diet was analyzed using the frequency of occurrence, numerical and gravimetric methods. Two hundred and sixty nine (27.45%) of the stomachs examined were empty. The fish was an omnivore feeding extensively on a wide array of plant and animal food items. These consisted of 9 families, 10 genera and 10 species. The most extensively consumed plant food item was aquatic plant parts which occurred in 63.88% of the stomachs, and accounted for 6.06% by number and 12.10% by weight while the ephemeropteran, Povilla adusta was the most dominant animal food item, occurring in 50.92% of the stomachs, and accounting for 11.98% by number and 11.86% by weight. Conversely, the least consumed plant food item was Volvox occurring in 4.49% of the stomachs and accounting for 0.18% by number and 0.35% by weight, while the fish Barbus sp. was the least consumed animal food item occurring in 0.51% of the stomachs, accounting for 0.03% by number and 1.62% by weight. New food items not previously recorded such as a watermite, Aspatharia sinuata and Barbus callipterus were found in the stomach contents. The nonspecific feeding regime of the fish and its ability to utilize different food items effectively was what accounted for the prominence and wide distribution of the fish in the lake.

A year-long research on the Mugil cephalus and M. curema diet was conducted. The food content in the cardiac portion of 192 stomachs revealed a great similarity in both species leading to two conclusions: sediments are their basic food and high levels of benthic diatoms are dominant. A total of 130 taxa were found (Nitzschia, Navicula, Amphora, and Cocconeis dominated). Other food components were: Foraminifera, Nematoda, Copepoda, Ostracoda, Amphipoda, Pelecypoda, Gastropoda, eggs of invertebrates, and undetermined organic matter

The armored catfish Hypostomus affinis is a widespread Loricariidae fish in the Lajes Reservoir (22o42’-22o50’ S; 43o53’-44o05’ W), the largest lentic environment in the Rio de Janeiro State, but little is known about their reproductive biology. One hundred and twenty five females, captured from January 1996 to December 1997, were used to assess ovarian development (29 were used to determine fecundity). The oocyte distribution by size-diameter classes revealed the occurrence of two modes suggesting an asynchronic development of the ovaries. The total fecundity ranged from 1235 to 4304, averaging 2374. An exponential relationship between fecundity and total length was determined, and a direct linear relationship was found between fecundity and total weight and gonad weight.

Specimens of the characid Brycinus nurse (N = 980) were collected in Asa reservoir, Nigeria, from November 1991 to October 1993. The diet was analyzed from stomach contents using the frequency of occurrence, numerical and gravimetric methods. Fish sex affected occurrence, number and weight of food items. The relative importance index (RI) indicates that diet varied seasonally. There was also a noticeable switch from insectivorous habits in small fish (less than 18 cm) to herbivorous feeding habits in larger fish. The ability of the fish to evolve trophic strategies that ensure optimum foraging despite seasonal changes can account for its success in the lake.

A systematic revision of the fish genus Bryconamericus from Central America was done based in museum collections (UCR, STRI, BMNH, USNM, UMMZ) and samples collected by the author in Panama. Five valid species are recognized: B. bayano, B. emperador, B. gonzalezoi sp. nov. B. scleroparius and B. terrabensis; B. ricae is synonyms of B. scleroparius. Moreover, B. scleroparius and B. terrabensis were redescribed with fresh material and the lectotype of B. scleroparius was designated. Bryconamericus baudoensis, B. ortholepis, B. scopiferus (from western of Colombia), B. cascajalensis and B. zeteki (from Central America) are synonyms of B. emperador.

Pelagic fish were collected with long line in the 20-22ºC isotherms from 1986 to 1988 off Guajira, Colombia. Thirteen species of pelagic fish were found incluiding four new records: Lampris guttatus, Lepidocybium flavobrunneum, Tetrapturus pfluegeri, Eumegistius brevorti. The occurrence of the orca (Orcinus orca Linnaeus) is confirmed in the Colombian Caribbean waters.

Water retention on the leaf surface can be maladaptive to the plant because it increases the colonization of epiphylls and interferes with the physiologic processes of the leaf, diminishing the photosynthetic capacity. To test if leaf driptips facilitate leaf drying after rainfall in a tropical rain forest of Costa Rica, we (1) experimentally measured the capacity to retain water on leaf surfaces of 30 plant species before and after dritip removal, and (2) analyzed the development of driptips along forest strata. We expected leaf driptips to be less developed in the upper strata due to the environmental conditions of the canopy (i.e., high solar radiation, strong winds and low relative humidity), which favor the natural drying of leaves. The presence of driptips increased 100% the water run off capacity of leaves in all the analyzed species. Also, the development of leaf driptips was smaller in canopy species than in understory species. Additionally, they became less developed in canopy species as trees increased in height. These results support the hypothesis that the adaptive role of driptips is to facilitate the drying of leaf surfaces.