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At least 289 records · Page 16Linked to original sources
PubMed1991

The lack of influence of exogenous testosterone on male parental behavior in a neotropical frog (Eleutherodactylus): a field experiment.

Males of the Puerto Rican frog Eleutherodactylus coqui exhibit prolonged parental care (nest attendance and defense) of direct-developing eggs in nonaquatic nest sites. Earlier work showed that plasma androgen levels are significantly lower in males caring for eggs than in noncaring, calling males. In this study, we investigated the effects of elevated plasma androgens on parental care behavior by implanting either testosterone (T) or placebo (P) pellets in parental males brooding eggs in the field. Plasma androgen levels, assessed 4 days after pellet implantation, were six times higher in T males than in P males. Despite this increase, T males exhibited no changes in nest fidelity or brooding behavior. The results indicate that lower androgen levels, at least those corresponding to a decline in T during parental care, are not necessary to maintain parental behavior in this tropical frog.

Animals↗
PubMed1987

Leishmaniasis in Brazil: XXIII. The identification of Leishmania braziliensis braziliensis in wild-caught neotropical sandflies using monoclonal antibodies.

Using the indirect immunofluorescence test natural flagellate infections of wild-caught sandflies, from the Serra dos Carajás region of Pará State, Brazil, were identified by sequentially staining smears made from the infected flies with monoclonal antibodies. With normal methods of isolation 30% of the infections were identifiable, but when monoclonal antibodies specific to Leishmania braziliensis braziliensis were used a further 26% were identified. The staining of organisms in smears of natural infections was different from that seen with culture forms and with forms from experimentally infected wild flies. A monoclonal antibody previously thought to be specific for Leishmania did not react with culture forms of Endotrypanum, but did react with those of monoxenous insect parasites.

Animals↗
PubMed1992

Variability in alkaloid profiles in neotropical poison frogs (Dendrobatidae): genetic versus environmental determinants.

Dendrobatid frogs produce a diverse set of alkaloids, whose profiles appear characteristic of frogs of each species or, in the case of variable species, of each population. In the case of one widespread species, Dendrobates auratus, alkaloid profiles in extracts of skin are markedly different in three populations, one from a Pacific island, Isla Taboga, Panama, one from central mountains in Panama, and the third from the Caribbean coast in Costa Rica. The first contains three major classes of dendrobatid alkaloids, the histrionicotoxins, the pumiliotoxin-A class and the decahydroquinolines. The second contains mainly histrionicotoxins, pumiliotoxin-A class alkaloids and one indolizidine. The third contains histrionicotoxins, a homopumiliotoxin, one decahydroquinoline, and a variety of indolizidines, quinolizidines and pyrrolizidines. Frogs from Isla Taboga or a nearby island were introduced into the Manoa Valley, Oahu, Hawaii, in 1932. Remarkably, although alkaloids of the pumiliotoxin-A class and one decahydroquinoline are still major constituents in skin extracts of Hawaiian frogs descended from the 1932 founding population, histrionicotoxins are absent and a novel tricyclic alkaloid is present. Offspring of wild-caught parents from Hawaii, Panama or Costa Rica raised in indoor terrariums on a diet of crickets and fruit flies do not contain detectable amounts of skin alkaloids. Offspring raised in large outside terrariums in Hawaii and fed mainly wild-caught termites and fruit flies do contain the same profile of alkaloids as their wild-caught parents in Hawaii, but at reduced levels. The genetic, environmental and dietary determinants of alkaloid profiles in dendrobatid frogs remain obscure, in particular the underlying cause for total absence in terrarium-reared frogs.

Alkaloids↗
PubMed1983

Renal function in the neotropical bat, Artibeus jamaicensis.

1. When feeding on figs (Ficus insipida), the bat Artibeus jamaicensis increases dietary sodium density while decreasing potassium density by primarily extracting and ingesting pulp juices rather than other parts of the fruit. 2. Based on urine osmotic pressure, these bats are uniformly dehydrated when they leave day roosts and become rapidly rehydrated (0.5-1 hr) after initiation of feeding. 3. After 2000 hr, and throughout the night there is no difference in urine concentration of free-flying bats compared with bats held in the laboratory without food or water for the same time interval. 4. Mean maximum urine concentration in this species is 972 mOsm/kg.

Animals↗
PubMed1989

Fungi in neotropical epiphyte roots.

Roots of thirty-eight Ecuadoran vascular epiphytes, representing eleven angiosperm families, were examined for the presence of symbiotic microorganisms. Most orchid roots contained fungal endophytes like those that regularly infect terrestrial counterparts. Hyphae were also common in and on nonorchid roots, but assignments of these relationships to known mycorrhizal morphologies was not possible in all cases. Evidence of vesicular-arbuscular mycorrhizae (VAM) existed in a number of subjects while in Ericaceae and Campanulaceae a fungal association similar to the demateaceous surface fungi (DSF) described for alpine and prarie plants was usually present. Some associations were characterized by multicellular propagules on root surfaces. The significance of these findings and the factors likely to influence occurrence and consequences of root-fungus mutualisms in tropical forest canopies are discussed. Facts and considerations that could aid future inquiry on these systems are provided.

Fungi↗
PubMed2006

Effects of temperature and calcium availability on cardiac contractility in Synbranchus marmoratus, a neotropical teleost.

An isometric muscle preparation was used to investigate the importance of the ventricular sarcoplasmic reticulum (SR) and extracellular Ca2+ (1.25 up to 11.25 mM) to force generation at 25 degrees C (acclimation temperature), 15 and 35 degrees C. The post-rest tension and force-frequency relationship were conducted with and without 10 microM ryanodine in the bathing medium. Increments in extracellular Ca2+ resulted in increases in twitch force development only at 35 degrees C. A significant post-rest potentiation was recorded for the control preparations at 25 degrees C (100% to 119.8+/-4.1%). However, this post-rest potentiation was inhibited by ryanodine only at 25 degrees C (100% to 97.6+/-1.5%). At 35 degrees C, force remained unchanged in the control preparations, but a significant post-rest decay was recorded in the presence of ryanodine (100% to 76.6+/-4.6%) while at 15 degrees C, ryanodine was not able to preventing the post-rest potentiation observed in the control preparations. The increases in the imposed contraction frequency caused a decline of the force at 25 and 35 degrees C and ryanodine decreased significantly peak tension at both temperatures. The findings suggest a high or medium calcium turnover, possibly related to the presence of a functional SR, whose functionality is diminished when temperature is decreased.

Animals↗
PubMed2006

Stomach lysozymes of the three-toed sloth (Bradypus variegatus), an arboreal folivore from the Neotropics.

Lysozymes are antimicrobial defences that act as digestive enzymes when expressed in the stomach of herbivores with pre-gastric fermentation. We studied this enzyme in the complex stomach of the three-toed sloth (Bradypus variegatus), a folivore with pre-gastric fermentation. Lysozymes were identified by SDS-PAGE and immunoblotting in all portions: diverticulum, pouch, glandular and muscular prepyloric area with 14.3 kDa of molecular mass. Purified lysozymes from all areas but the diverticulum were characterized by MALDI-TOF, optimal pH, optimal ionic strength, and specific activity. The differences observed suggested at least three isoforms. The optimal pHs were similar to the pH of the stomach portion where the enzymes were isolated. The lysozyme from the pouch (fermentation chamber) exhibited higher specific activity and concentration than the others. The specific activity of the enzyme from the acid muscular prepyloric portion was comparable to that reported in the cow abomasums; however, its concentration was lower than that observed in cow. This distinctive pattern of secretion/specific activity and overall low concentration suggests different roles for the lysozymes in this herbivore compared to Artiodactyla. We postulate that sloth stomach lysozymes may still be antimicrobial defences by protecting the microbial flora of the fermentation chamber against foreign bacteria.

Animals↗
PubMed2004

Differences in ingestive balance of two populations of neotropical Thrichomys apereoides (Rodentia, Echimyidae).

Thrichomys apereoides is widely distributed in the Caatinga, a semi-arid region in Brazil, but is presumed to lack capabilities for water conservation. In the present study, we compared two populations of adult individuals living under different precipitation conditions (700 and 450 mm year(-1)). Animals from the less dry area were twice as heavy as those from the drier locality. Under ad libitum water regimen, there were differences between populations in relative food intake as well as in water intake and urine concentration, but not in normalized body mass water intake. Under short-term water deprivation, both populations presented similar body mass loss. Whereas individuals from the more arid locality maintained food consumption, urine volume and urine osmolality, Thrichomys from the less dry locality reduced food consumption and urine volume. The occurrence of anuria in 75% of animals from this population indicates that the limits of their ability to deal with water shortage had been reached. The morphological and physiological difference and the non-allometric similarities found between the two populations of T. apereoides fulfill the criteria for physiological adaptations to differences in annual rainfall. Our data challenge the hypothesis that the irregularity of annual rainfall in the Caatinga precludes the evolution of adaptations to this semi-arid climate.

Adaptation, Physiological↗
PubMed2005

Erythrocyte senescence and haematological changes induced by starvation in the neotropical fish traíra, Hoplias malabaricus (Characiformes, Erythrinidae).

Adult specimens of traira (Hoplias malabaricus Bloch) were subjected to long-term starvation (30 to 240 days) and re-fed for 30 days after 90 and 240 days of food deprivation. Counting of immature erythrocytes in peripheral blood showed that erythropoiesis decreased significantly during the first 30 days of food deprivation. The results suggest that a process of senescence takes place in the pre-existent red blood cells and that the cells are not replaced during starvation. After 240 days of starvation, H. malabaricus had a significantly reduced number of red blood cells, causing changes in hematocrit and blood indices (mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration). Furthermore, during this period, the fish presented leukopenia (lymphocytopenia) and thrombocytopenia. After re-feeding, the number of leukocytes and thrombocytes recovered, but the red blood cell number remained reduced and there was a significant increase in abnormal red cell nuclei.

Animal Feed↗