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

As a tribute to Revista de Biología Tropical in its 50th anniversary, this review describes some of the main research efforts carried out in the study of the chemical composition and the mechanism of action of toxins present in the venoms of snakes distributed in Latin America. Venom proteins involved in neurotoxicity, coagulopathies, hemorrhage and muscle necrosis are discussed, together with a description of the inflammatory reactions elicited by these venoms and toxins. In addition, the search for inhibitory substances present in plants and animals that may be utilized in the neutralization of venoms is analyzed. Some of the clinical studies performed on snakebite envenomations in Latin America are also reviewed, together with the development of technologies aimed at improving the quality of antivenoms produced in the region. Toxinology has become a fruitful and stimulating research field in Latin America which has contibuted to a better understanding of snake venoms as well as to an improved management of snakebitten patients.

The geosciences contribution along the 50 years of the Revista de Biología Tropical had been scarcity and episodic. Until now there are 2374 papers but only 21 (0.88%) have some relation with geological sciencies. It`s posible to reconize two periods with geological contributions, one between 1963 and 1978. It`s appropiate to underline the importance of the biologist L. D. Gómez with his contributions about Costa Rican Paleobotanic in this period. The other period includes from 1988 to the present, and it`s tipyfied by an increase of biologist and geologist participation in different topics regarding with geosciences. Foreing and national researches are in the same ratio and belong from several contries like Costa Rica, México and Dominican Repubic. The subjects are concerning mainly about fossil taxonomy (Paleontology: 81%), only 19% are related with geological topics. Such distribution could be explained because the affinity between the fossil studies and the biological sciences.

It is suggested that descriptive taxonomy of thrips must be integrated into biological studies if we are to understand patterns of evolutionary and ecological diversity. Collecting and describing new taxa is easy, but understanding their position in ecosystems and how they have contributed to the origin and maintenance of biological diversity is more important yet more difficult. Many authors fail to appreciate that individual thrips species are commonly highly polymorphic, both within and between sexes, with the result that 20% of species names and 30% of generic names are currently placed into synonymy. The biological significance of such polymorphism has been little studied, but the presence of large and small males in a species is presumed to indicate some form of male/male competition for resources; this is particularly common in fungus feeding species. Amongst phytophagous species, the recognition of the host plants on which thrips actually breed is a prerequisite to understanding patterns of diversity, some thrips lineages being associated with particular groups of plants whereas others exploit a diverse range of plants. Attempts to understand the diversity of thrips, including the application of cladistic methods, are severely limited by the lack of studies on the biology of individual species, although thrips exhibit a wide range of interesting biological phenomena, including various levels of sociality, gall-induction, specific pollination associations, virus transmission, and ectoparasitism.

Tropical coastal biodiversity has been modulated by tropical storms during a long time and it is currently facing a heavy human impact. The purpose of this review is to compile the available information to improve our understanding of hurricane impacts and to promote the establishment of coastal landscape monitoring, because that is the best way to assess these impacts. Although generalizations on hurricane effects are elusive, some historical dynamics and temporal relationships are included and some details are presented on the impacts by resuspension and movement of sediments, storm waves, and breaking off of coral reef organisms. Some effects on marine turtles and coastal forests are also briefly pointed out

A morphological characterization of Thysanophora crinita (Fulton, 1916-1917), including a redescription of the shell and the first description of the genital system, the radula and the jaw, are made based on 58 living individuals and 1378 empty shells; the sample considered for biometry was of 81 specimens. Means and ranges were 3.51 mm (2.6-4.9) diameter and 2 mm (1.5-2.5) height. This species exhibits a discoidaldepressed shell, with an opaque hairy periostracum as its most remarkable feature. The genital system is typical of the genus, with a well developed penis and a pear-shaped bursa copulatrix. Jaw: 16 to 18 narrow plates and radula with 72 transversal rows, formula: (C/3 + 5L/2 + 6M/2) x 2. The Nicaraguan populations of T. crinita are very similar to T. crinita from Cartagena and T.c. arubana, and show dimensiones intermediate between both. This species was previously known from Carthagena, Colombia and is reported from Nicaragua for the first time. A distribution map is included.

A comparative study was performed on the venoms of adult specimens of the neotropical rattlesnake, Crotalus durissus, from Guatemala, Costa Rica, Venezuela and Brazil, together with the venom of newborn specimens of C. d. durissus from Costa Rica. Venoms from Brazil (C. d. terrificus) and from newborn specimens of C. d. durissus presented an electrophoretic pattern characterized by the predominance of bands with molecular mass of 36 and 15 kDa, whereas those of adult specimens of C. d. durissus from Guatemala and Costa Rica, and C. d. cumanensis from Venezuela, showed a conspicuous band of 62 kDa, and additional bands of 36, 29 and 15 kDa. Moreover, venoms from C. d. terrificus and C. d. cumanensis showed a prominent band of < 10 kDa that probably corresponds to crotamine, since a ‘crotamine-like’ activity was detected in these venoms upon intraperitoneal injection in mice. Venoms of C. d. terrificus, C. d cumanensis and newborn C. d. durissus induced higher lethal and myotoxic effects than those of adult C. d. durissus. In contrast, adult C. d. durissus and C. d. cumanensis venoms induced hemorrhage, whereas venoms of C. d. terrificus and newborn C. d. durissus lacked this effect. All venoms showed coagulant effect in plasma, the highest activity being observed in the venom of newborn C. d. durissus. An anti-crotalic antivenom produced by Instituto Butantan (Brazil), using C. d. terrificus venom as antigen, was effective in the neutralization of lethal, myotoxic and coagulant effects of all venoms studied, being ineffective in the neutralization of hemorrhagic activity of the venoms of C. d. cumanensis and C. d. durissus. On the other hand, a polyvalent antivenom produced by Instituto Clodomiro Picado (Costa Rica), using the venoms of C. d. durissus, Bothrops asper and Lachesis stenophrys as antigens, was able to neutralize lethal, myotoxic, coagulant and hemorrhagic effects of C. d. durissus venom, but was ineffective in the neutralization of lethality and myotoxicity of C. d. terrificus, C. d. cumanensis and newborn C. d. durissus venom. The high toxicity of South American and newborn C. d. durissus venoms is related to the presence of high concentrations of the neurotoxic phospholipase A2 complex ‘crotoxin’. Accordingly, antivenom from Instituto Butantan has a much higher titer of anti-crotoxin antibodies than antivenom from Instituto Clodomiro Picado. Crotalus durissus represents an example of intraspecies variation in venom composition and pharmacology that has relevant pathophysiologic and therapeutic implications.

Most of the research about viral interactions with human chromosomes was done during the sixties and early seventies and very few was performed after the human immunodeficiency virus (HIV) appearance as an epidemic in the eighties. The objective of this work was to estimate if particular chromosomal changes follow the infection of homosexual males by HIV and to determine if the lifestyle, habits, sexual practices, of our sample of male homosexuals predisposes them to chromosomal abnormalities at a higher rate than the background level of cytogenetic damage the general population has. This was a double blinded case-control study, 17 individuals positive for HIV antibodies (HIV+) detected by enzyme-linked immunosorbent assay (ELISA) and confirmed by western blot (WB) were the cases, and 17 individuals negative for HIV antibodies (HIV-) the controls. These men were a very homogeneous population in terms of age, social status, lifestyles, drug abuse, sexual practices and education. Blood was collected between September 1988 and October 1989. Fresh whole blood was cultured in duplicate for 72 hr. Cell harvest followed conventional methods. Once all cell cultures were gathered, the tubes were picked up at random and air dried chromosome preparations were trypsin-giemsa banded (GTG) after overnight incubation at 60Cº. The percentage of gaps and breaks these men had was not different from the reported for the general population, nor were there significant difference among both groups (O.R. = 1.8) in terms of amount of chromosomal fragility. The distinction among them was at the level of the specific chromosomal sites where the gaps and breaks located, being sites at 2p21 and at 3p21 four times more frequent among HIV+. These probably represent viral modification sites on chromosomes which are known to look like non-staining gaps which are caused by the virus or viral products. This presumption is supported by an earlier report of repeated breaks at 3p21.1 , in fact this was the most common lesion site in this study of chromosomal aberrations of male homosexuals and the authors even considered the probability of “a new type of chromosome marker” . Furthermore, years later the CKR5 structural gene was mapped to human chromosome 3p21. This gene codes for the chemokine receptor 5 (CKR5) protein which serves as a secondary receptor on CD4+ T lymphocytes for certain strains of HIV-1. It is possible that this gene was being transcribed in HIV+ men and the consequent “staggering” of DNA contributed to the production of gaps and breaks at 3p21.

Two lotic bodies located in a subtropical semi-arid region in north-western Argentina were studied: the Arias-Arenales and the Rosario rivers. Both rivers are located in Salta Province, and belong to the high basin of river Juramento, connected to the river Río de la Plata and the Atlantic Ocean. The study was conducted between March 1997 and March 1998. The region is known by its sustained economic development and one of the highest population growth rates in the country (4% per year). The objective of this work was the assessment of organic pollution spatial gradients in both rivers, as a function of the hydrological regime (a long period of drought from May to October and floodings the rest of the year). Three groups of biotic indices were applied to characterize the level of organic pollution and were based on planktonic microalgae to evaluate water quality. The relative performance of these indices was then compared for use to biomonitoring programs. The diversity indices: Shannon-Weaver and Whilm-Dorris were not highly sensible to detect moderate pollution. The saprobity indices (Pantle and Buck and Diatom Assemblage Index of Watanabe et al.), were useful to detect intermediate levels of organic load, but their sensitivity dropped at high pollution levels. The second index precisely discriminated the most deteriorated part of river Rosario, with values between 0.3 – 0.7 (extreme poli-saprobity). Raw sewage discharges along the most polluted sector of river Arias-Arenales were assigned a value between 10 and 11 in both periods of the hydrological regime. Both saprobity indices consider the same indicator pollution value of species. The first one is based on the relative abundance of the species while the second one is calculated with the species relative frequency. The second index is better than the first one in considering non-dominant species that were constant in each particular environmental condition. The principal component analysis allowed a representation of time and space pollution patterns and showed the specific microalgae assemblage for all the sampling stations and for both periods in the hydrological cycle. Only the latter proved to be fully useful and correct for the biological characterization of water quality system.

We report lichen cover change over a 20 years period for the Costa Rican capitol city. Foliaceous lichen cover was measured with a 10 X 10 cm template positioned 1.5 m above ground on the south, east, north and west sides of ten phorophytic trees per station (11 stations) from 1976 through 1997. Results were compared with previous measurements along an urban transect (at three heights above ground) and in a rural station. Lichen cover was correlated with traffic density and varied between stations and years. Mean lichen cover was 23% in 1976, 12% in 1986, 9% in 1990 and 22% in 1997. Most stations suffered a large cover reduction after 1976 but improved after 1990, possibly reflecting improved traffic regulations and elimination of lead (Pb) from gasoline. Cover values by cardinal orientation were: west 17%, east 14%, north 13% and south 12%. Sidewalks of streets with more traffic had lower cover values. In the rural station, cover was lower than expected (possibly because of climate), and was not correlated with height above ground or cardinal orientation, in contrast with temperate regions. In polluted cities human activity should concentrate above the first floor of buildings (particularly in hospitals or schools) because pollution was found to concentrate in the first 2 m above ground.

The relationship between the myrmecophytic tree Duroia hirsuta (Rubiaceae) and its associated, minute, non-aggressive Myrmelachista sp. (Formicinae) ants is poorly investigated, even though the small understory tree is surrounded by a conspicuos zone almost devoid of vegetation. As to the cause of these barely vegetated “Devil’s Gardens”, two alternative interpretations exist in the literature: the pruning activity of ants and allelopathy. We investigated the mutualistic Duroia-Myrmelachista system in the Ecuadorian Amazon, focusing on the phenomenon of the areas of reduced vegetation, as well as on the natural history of the associated ants. We conducted planting experiments and behavioral studies, including coccoids, the third partner in this mutualism. Because the well-studied Triplaris americana (Polygonaceae) possesses analogous vegetation free surroundings created by the assiduous mechanical pruning of its mutualistic ant partner (Pseudomyrmex sp.), parallel comparative investigations of this ant-plant association were conducted. The two systems are not equivalent; it was demonstrated that the remarkably inactive Myrmelachista ants are not responsible for the bare areas around Duroia plants. Instead, we regard allelopathy as the causative agent for the clear zones.