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At least 433 records · Page 24Linked to original sources
PubMed2003

Reproductive ecology of a neotropical cichlid fish, Cichla monoculus (Osteichthyes: Cichlidae).

The reproductive ecology of the freshwater fish Cichla monoculus Spix, 1831 (Osteichthyes: Cichlidae) was investigated in the Campo Grande Reservoir, Northeast Brazil. Rainfall, temperature, pH, dissolved oxygen and electrical conductivity of the water were recorded monthly. Fish collected on a monthly basis were measured, weighted, dissected, sexed and the stage of maturation of the gonads were assessed by macro and microscopic means. The semi-arid study region has short spells of rain of 2-3 months duration interspersed with dry seasons. A positive correlation was observed between rainfall and air and water temperatures and conductivity of the water. The study population had an extended spawning season, with peak reproductive activity coinciding with low water temperatures. Males were longer and heavier than females on average and were larger at onset of sexual maturity. The size frequency distributions of the oocytes indicate that C. monoculus is a multiple spawner with an estimated batch fecundity of 3100. Condition factor showed an inverse relationship in relation to gonad size during maturation in both sexes and spent fish were in poor condition. In mature males, lipid stores in the post-occipital cephalic protuberance, a secondary sexual characteristic developed during the reproductive phase, which depleted in spent individuals. The success of this fish is attributed to its reproductive capacity and to the phenotypic plasticity that allows it to adapt to the harsh ecological conditions that prevail in the semi-arid region of Northeast Brazil.

Animals↗
PubMed2004

Ureotelism is inducible in the neotropical freshwater Hoplias malabaricus (Teleostei, Erythrinidae).

Increased environmental pH decreases ammonia transport through the gills, impairing nitrogenous waste. The consequent toxicity is usually drastic to most fishes. A few species are able to synthesize urea as a way to detoxify plasma ammonia. We studied three teleosts of the family Erythrinidae living in distinct environments, and assumed the biochemical behaviors would be different in spite of their being closely related species. Adult fish collected in the wild were submitted to alkaline water and the urea excretion rate was determined. The specific activity of urea cycle enzymes was determined in liver samples of fish from neutral waters. The studied species Hoplias lacerdae, Hoplerithrynus unitaeniatus, and Hoplias malabaricus are ureogenic. Urea synthesis is not a metabolic way to detoxify ammonia in H. lacerdae and Hoplerithrynus unitaeniatus exposed to an alkaline environment. The plasma ammonia profile of both species showed two distinct biochemical responses. Urea excretion of H. malabaricus was high in alkaline water, and the transition to ureotelism is proposed. The nitrogen excretion rate of H. malabaricus was among the highest values reported and the high urea excretion leads us to include this species as ureotelic in alkaline water.

Adaptation, Physiological↗
PubMed2005

Acute morphological and physiological effects of lead in the neotropical fish Prochilodus lineatus.

The present study investigated lead effects on gill morphology, hematocrit, blood sodium, glucose, lipids, protein, and cholesterol of Prochilodus lineatus exposed to two sublethal lead concentrations for 96 h. Preliminary series of short-term static toxicity tests were run to determine LC50 (96 h) of lead in P. lineatus, which was 95 mg Pb.L-1. Therefore, lead concentrations tested in the sublethal experiments were 24 and 71 mg Pb.L-1, which correspond to 25% and 75% of the LC50 (96 h), respectively. Gills of P. lineatus exposed to both lead concentrations during 96 h presented a higher occurrence of histopathological lesions such as epithelial lifting, hyperplasia, and lamellar aneurism. P. lineatus did not show significant alterations in hematocrit during exposure to both lead concentrations. Fish exposed to the highest lead concentration showed a significant decrease in Na+ plasma concentration after 48 h, possibly reflecting a sodium influx rate decrease. P. lineatus exposed to both lead concentrations presented a "classical general adaptation syndrome to stress", as hyperglycemia associated with lowered lipids and proteins was reported. Stress-response magnitude was dose-dependent. While the response to the lowest lead concentration might represent adaptation, the highest concentration seems to characterize exhaustion.

Adaptation, Physiological↗
PubMed2005

Cytogenetic analysis of the neotropical spider Nephilengys cruentata (Araneomorphae, Tetragnathidae): standard staining nors, C-bands and base-specific fluorochromes.

The aim of this work is to characterize Nephilengys cruentata in relation to the diploid number, chromosome morphology, type of sex determination chromosome system, chromosomes bearing the Nucleolar Organizer Regions (NORs), C-banding pattern, and AT or GC repetitive sequences. The chromosome preparations were submitted to standard staining (Giemsa), NOR silver impregnation, C-banding technique, and base-specific fluorochrome staining. The analysis of the cells showed 2n = 24 and 2n = 26 chromosomes in the embryos, and 2n = 26 in the ovarian cells, being all the chromosomes acrocentric. The long arm of the pairs 1, 2 and 3 showed an extensive negative heteropycnotic area when the mitotic metaphases were stained with Giemsa. The sexual chromosomes did not show differential characteristics that allowed to distinguish them from the other chromosomes of the complement. Considering the diploid numbers found in N. cruentata and the prevalence of X1X2 sex determination chromosome system in Tetragnathidae, N. cruentata seems to possess 2n = 24 = 22 + X1X2 in the males, and 2n = 26 = 22 + X1X1X2X2 in the females. The pairs 1, 2 and 3 showed NORs which are coincident with the negative heteropycnotic patterns. Using the C-banding technique, the pericentromeric region of the chromosomes revealed small quantity or even absence of constitutive heterochromatin, differing of the C-banding pattern described in other species of spiders. In N. cruentata the fluorochromes DAPI/DA, DAPI/MM and CMA3/DA revealed that the constitutive heterochromatin is rich in AT bases and the NORs possess repetitive sequences of GC bases.

Animals↗
PubMed2006

Floral preferences of a neotropical stingless bee, Melipona quadrifasciata Lepeletier (Apidae: Meliponina) in an urban forest fragment.

Species of plants used by Melipona quadrifasciata Lepeletier for pollen and nectar gathering in an urban forest fragment were recorded in Belo Horizonte, Minas Gerais, Brazil. Melipona quadrifasciata visited 22 out of 103 flowering plant species. The plant species belonged mainly to Myrtaceae, Asteraceae, and Convolvulaceae (64% of the visits). Melipona quadrifasciata tended to collect pollen or nectar each time, except for Myrtaceae species, from which both pollen and nectar were collected. Bee abundance at flowers did not significantly correlate to food availability (expressed by flowering plant richness). We found a relatively high similarity (50%) between plant species used by M. quadrifasciata, which was also found in studies carried out in São Paulo State. However, low similarity (17%) was found between the results of this study and those of another done in Bahia State, Brazil.

Animals↗
PubMed2003

Two digestive trypsins occur in three species of neotropical anophelines.

Trypsin activity increases in the midgut of Anopheles aquasalis, Anopheles albitarsis, and Anopheles darlingi after a bloodmeal. The activity returns to basal levels at the time the blood is completely digested. Affinity chromatography, reversed-phase high performance liquid chromatography (HPLC), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used to sequentially purify the mosquito trypsins found in the midguts at 24 h after feeding. Aminoterminal sequencing of the purified trypsins showed the occurrence of two distinct trypsins in the midgut of each of the mosquitoes studied. The sequences obtained are similar to those of the trypsins of other hematophagous insects.

Amino Acid Sequence↗
PubMed2003

Bots (Diptera: Oestridae) infesting a neotropical forest rodent, Proechimys semispinosus (Rodentia: Echimyidae), in Panama.

Botfly larvae (Cuterebra sp.) infesting spiny rats (Proechimys semispinosus) in 8 small islands in the Panama Canal were studied. Rats were live trapped monthly on each island from January 1991 through February 2000 and visually examined for the presence of bots. Overall, bot prevalence was 4.6% and differed statistically among island rat populations. Rats were simultaneously infested by as many as 4 bots. Overall bot intensity was 1.3 bots per infested rat and did not differ among islands. Mean bot density across all islands was 0.0111 and was greater during the dry seasons than during the rainy seasons, but it did not differ among islands. Bots were found during all the 12 calendar months, suggesting a multivoltine reproductive schedule. Although bot activity varied seasonally, there was little synchrony of bot activity among islands. Bot density was related negatively to rainfall but was not related to host density, suggesting that drier ambient conditions may promote reproduction by adult bot flies in this system.

Animals↗
PubMed2005

Neotropical Monogenoidea: Euryhaliotrema dontykoleos n. sp. (Dactylogyridae) from the gills of the freshwater sciaenid, Pachyurus junki (Perciformes).

Euryhaliotrema dontykoleos n. sp. (Monogenoidea, Polyonchoinea, Dactylogyridae) is described based on specimens collected from the gills of Pachyurus junki (Teleostei, Sciaenidae, Pachyurinae) in the Rio Tocantins and its tributaries, State of Tocantins, Brazil. The new species, the first species of Monogenoidea reported from a pachyurine, is easily differentiated from its congener by the presence of toothlike projections in the border of the vaginal opening and by having a trapezoidal anteromedial projection on the ventral bar. Phylogenetic analysis indicates that the new species is not a member of the clade that includes the Euryhaliotrema spp. from Plagioscion spp., a second lineage of freshwater sciaenids in South America. Euryhaliotrema dontykoleos shares an immediate ancestor with the clade formed by parasites infecting marine Paralonchurus spp., (Sciaenidae), and those of Plagioscion spp.

Animals↗
PubMed2003

Neotropical Monogenoidea. 43. Diplectanum monticellii n. sp. (Diplectanidae) from the gills of Cynoscion leiarchus (Perciformes: Sciaenidae) in Brazil.

Diplectanum monticellii n. sp. is described from the gills of Cynoscion leiarchus, a marine Sciaenidae, from Itacuruçá, Rio de Janeiro (type locality); Baía de Guaratuba, Paraná; and Pontal do Sul, Paraná in Brazil. The new species is characterized by the following features: bell-shaped male copulatory organ with a sleevelike base, accessory piece absent, vas deferens looping left intestinal cecum, vaginal aperture sinistroventral, and ventral anchor with elongate superficial and deep roots.

Animals↗
PubMed2006

Thermal ecology of the neotropical army ant Eciton burchellii.

I explored the thermal ecology of Eciton burchellii, a New World army ant, in primary forest and forest fragments in the Atlantic lowlands of Costa Rica in 2002 and 2003. My primary objective was to determine whether high surface temperatures in pastures surrounding forest fragments posed a thermal barrier to ant colonies within those fragments; secondarily, I assessed whether thermal gradients within continuous moist forest were sufficient to elicit avoidance reactions from foraging colonies. E. burchellii colonies in forest fragments avoided entering open pasture in full sun (51.3 degrees C) on 100% of all edge interactions; however, edges were readily crossed where artificial shaded areas had previously been installed. Ant raids in primary forest avoided artificially established temperatures >43 degrees C but tolerated 45.5 degrees C in the presence of prey baits. Captive ants held at 43 degrees C survived 18.5 min; at temperatures of 51.3 degrees C survival time was only 2.8 min. Ants running on established foraging trails increased running velocity by 18% when substrate temperature was raised from 28.4 degrees to 38.0 degrees C, and they abandoned trails at temperatures >43 degrees C. The standard deviation (s) of temperatures on active raid trails in continuous forest was 2.13 degrees C, while nearby systematic sampling revealed a greater background standard deviation of 4.13 degrees C. E. burchellii colonies in this region appear to be living surprisingly near their upper limits of thermal tolerance. The heat of open pastures alone is sufficient to prevent their exiting forest fragments, or entering similarly hot areas within continuous forest. Shaded vegetative corridors are sufficient to permit mobility between isolated fragments, and their preservation should be encouraged. Despite views that tropical lowland moist forests have an essentially homogenous microclimate, army ants appear to avoid local hot spots on the forest floor, steering daily foraging trails to follow cooler routes than would be expected by chance. As deforestation remakes tropical landscapes worldwide, it is important to consider the thermal consequences of these actions and their effect on keystone organisms such as army ants. Changes in global climate patterns are likely to affect even evergreen tropical systems whose organisms may be sensitive to finer microclimatic variation than previously suspected.

Animals↗
PubMed2006

Regional and phylogenetic variation of wood density across 2456 Neotropical tree species.

Wood density is a crucial variable in carbon accounting programs of both secondary and old-growth tropical forests. It also is the best single descriptor of wood: it correlates with numerous morphological, mechanical, physiological, and ecological properties. To explore the extent to which wood density could be estimated for rare or poorly censused taxa, and possible sources of variation in this trait, we analyzed regional, taxonomic, and phylogenetic variation in wood density among 2456 tree species from Central and South America. Wood density varied over more than one order of magnitude across species, with an overall mean of 0.645 g/cm3. Our geographical analysis showed significant decreases in wood density with increasing altitude and significant differences among low-altitude geographical regions: wet forests of Central America and western Amazonia have significantly lower mean wood density than dry forests of Central and South America, eastern and central Amazonian forests, and the Atlantic forests of Brazil; and eastern Amazonian forests have lower wood densities than the dry forests and the Atlantic forest. A nested analysis of variance showed that 74% of the species-level wood density variation was explained at the genus level, 34% at the Angiosperm Phylogeny Group (APG) family level, and 19% at the APG order level. This indicates that genus-level means give reliable approximations of values of species, except in a few hypervariable genera. We also studied which evolutionary shifts in wood density occurred in the phylogeny of seed plants using a composite phylogenetic tree. Major changes were observed at deep nodes (Eurosid 1), and also in more recent divergences (for instance in the Rhamnoids, Simaroubaceae, and Anacardiaceae). Our unprecedented wood density data set yields consistent guidelines for estimating wood densities when species-level information is lacking and should significantly reduce error in Central and South American carbon accounting programs.

Altitude↗
PubMed2006

Changes in climate and habitat suitability for the cattle tick Boophilus microplus in its southern Neotropical distribution range.

We addressed the possible effects of several climate scenarios on habitat suitability (HS) for the cattle tick Boophilus microplus and the probability of producing permanent populations from introduced females of that tick in central parts of Argentina, using both a correlative model (derived from climate predictors) and a mechanistic (life cycle) model. There was high correlation (R2 = 0.866) between HS-derived and life cycle outputs for HS values higher than 0.52, suggesting that HS is a good estimator of the life cycle of the tick above a critical threshold of HS values. Scenarios with increased temperatures increased suitable habitats for the tick in southern parts of the study region, extending below parallel 34 degrees S, but suitable habitats remained limited in the west. A concurrent increase in rainfall produced a further increase of HS in these areas. Results from the life cycle model suggest that in areas of suitable habitat, permanent cattle tick populations are most probable if engorged females are introduced during mid-summer.

Animals↗
PubMedDate not supplied

Systematics of the genus Chaetosphaeria and its allied genera: morphological and phylogenetic diversity in north temperate and neotropical taxa.

Chaetosphaeria is a common saprobic pyrenomycete genus with simple, homogeneous teleomorphs and complex, diverse anamorphs. As currently circumscribed in the literature, the genus encompasses 30 species distributed in four 'natural groups', and includes morphological entities in 11 anamorphic genera. Species frequently have been defined primarily based on characters of the anamorphs resulting in species with almost indistinguishable teleomorphs. This study aimed to assess the value and significance of morphological characters in resolving phylogenetic relationships in Chaetosphaeria and its allied genera. Phylogenetic relationships of 42 taxa, representing 29 species distributed in Chaetosphaeria and five related genera, were estimated with partial sequences of the nuclear LSU rDNA and beta-tubulin genes. Sequences were analyzed with maximum parsimony, maximum likelihood and Bayesian methods. Phylogenetic analyses of these two genes combined revealed two major lineages. The Chaetosphaeria lineage includes 21 species possessing both typical and new sexual and asexual morphologies. The lineage contains a strongly supported monophyletic clade of 13 species and eight paraphyletic taxa; the latter includes C. innumera, the type species of the genus. The second major lineage includes groupings concordant with the morphological circumscriptions of the genera Melanochaeta, Melanopsammella, Striatosphaeria, Zignoëlla and the new genus Tainosphaeria.

Ascomycota↗
PubMed1978

Humoral and cell-mediated immunity to Histoplasma capsulatum during experimental infection in neotropical bats (Artibeus lituratus).

The humoral and cell-mediated immune responses of the large, frugivorus bat, Artibeus lituratus, were studied following intraperitoneal injection of 10 or 10(4) viable mycelial particles of Histoplasma capsulatum. Most bats had both cultural and histologic evidence of disease at autopsy. Utilizing a technique designed to measure the volume of footpad swelling in hypersensitive bats a significant degree of delayed hypersensitivity to histoplasmin was evident in both groups 4 to 6 wk after infection. Precipitating antibodies first appeared in the serum 3 wk after infection, but only in the animals infected with 10(4) viable organisms. Both the double diffusion and counterimmunoelectrophoresis techniques for antibody gave identical results. These findings suggest that A. lituratus is very susceptible to infection with H. capsulatum, and that a mild infection will stimulate delayed hypersensitivity to the organism but only low levels of antibody. The footpad test utilized in this study may be a sensitive and practical method for detecting natural infection in bats.

Animals↗
PubMed2003

Ecologic correlates of Toxoplasma gondii exposure in free-ranging neotropical mammals.

A serologic survey for Toxoplasma gondii in 18 free-ranging forest mammal species (n = 456) in French Guiana was undertaken with a direct agglutination test. Serum antibody prevalence varied from 0-71%. The relationships between ecologic features of the species and seroprevalence were investigated. Terrestrial mammals were significantly more exposed to T. gondii than other mammals. This result is concordant with oral exposure to T. gondii related to ground dwelling behavior and/or carnivory.

Age Factors↗
PubMed2000

Visual and nutritional food cues fine-tune timing of reproduction in a neotropical rainforest bird.

Food may act as a proximate factor in the regulation of avian seasonal breeding. Food cues could provide particularly important seasonal information to birds living in variable tropical environments, but this has not yet been tested. Spotted antbirds (Hylophylax n. naevioides) inhabiting a humid forest in central Panama (9 degrees N) likely use changes in the tropical photoperiod to time reproduction on a long-term, seasonal basis. We predicted that these insectivorous birds also adjust reproduction to short-term cues such as food availability because the onset of the rainy season and the resulting increase in insect abundance varies considerably between years. To test this prediction, prior to their breeding season (when they had half-maximal gonads), we either exposed captive male spotted antbirds to an ad libitum standard diet only or added live crickets to this diet. Males that received live crickets significantly increased gonad sizes within 3 weeks over controls on the standard diet. Moreover, in six additional experiments cricket availability always increased song rate, usually within a few days. The stimulatory effect of live crickets on song activity may function independent of nutritional aspects: Freshly killed crickets, providing similar nutritional content as live crickets, did not stimulate the birds' song activity. However, song activity increased to intermediate levels when live crickets were shown under a clear plastic wrap, i.e., when birds could see but not eat crickets. We hypothesize that the opportunity to see and handle live insects stimulates song and reproductive activity in these birds. Our data indicate for the first time that a tropical rainforest bird can use food cues to evaluate the suitability of local environmental conditions for breeding. J. Exp. Zool. 286:494-504, 2000.

Animal Nutritional Physiological Phenomena↗