Maria da Graca Salomao

Tracing an invasion: landbridges, refugia, and the phylogeography of the Neotropical rattlesnake (Serpentes: Viperidae: Crotalus durissus)

Pleistocene fragmentation of the Amazonian rainforest has been hypothesized to be a major cause of Neotropical speciation and diversity. However, the role and even the reality of Pleistocene forest refugia have attracted much scepticism. In Amazonia, previous phylogeographical studies have focused mostly on organisms found in the forests themselves, and generally found speciation events to have predated the Pleistocene. However, molecular studies of open‐formation taxa found both north and south of the Amazonian forests, probably because of vicariance resulting from expansion of the rainforests, may provide novel insights into the age of continuous forest cover across the Amazon basin. Here, we analyse three mitochondrial genes to infer the phylogeography of one such trans‐Amazonian vicariant, the Neotropical rattlesnake (Crotalus durissus), which occupies primarily seasonal formations from Mexico to Argentina, but avoids the rainforests of Central and tropical South America. The phylogeographical pattern is consistent with gradual dispersal along the Central American Isthmus, followed by more rapid dispersal into and across South America after the uplift of the Isthmus of Panamá. Low sequence divergence between populations from north and south of the Amazon rainforest is consistent with mid‐Pleistocene divergence, approximately 1.1 million years ago (Ma). This suggests that the Amazonian rainforests must have become fragmented or at least shrunk considerably during that period, lending support to the Pleistocene refugia theory as an important cause of distribution patterns, if not necessarily speciation, in Amazonian forest organisms. These results highlight the potential of nonforest species to contribute to an understanding of the history of the Amazonian rainforests themselves.

Hemorrhagic, fibrinogenolytic and edema-forming activities of the venom of the colubrid snake Philodryas olfersii (green snake)

The venom of P. olfersii has high hemorrhagic, edema-inducing and fibrin(ogen)olytic activities. It is devoid of thrombin-like, procoagulant, phospholipase A2 and platelet aggregating enzymes. The main activities are metalloproteinases inhibited by metal chelators (EDTA and 1,10-phenanthroline) and sulfhydryl compounds (DTT and cysteine). The hemorrhagic and fibrinogenolytic enzymes were partially purified by gel filtration on HPLC. The hemorrhagic activity of the venom was neutralized by commercial horse antivenoms to Bothrops species, as well as by rabbit antisera specific for hemorrhagic factors isolated from these Bothrops venoms. No immunoprecipitin reactions were obtained, indicating that the few epitopes of the P. olfersii hemorrhagin are involved in these neutralization reactions. The fibrinogenolytic enzyme cleaves A alpha-chain more quickly than the B beta-chain of human fibrinogen. The venom also solubilizes fibrin. This solubilization appears to occur from the hydrolysis of unpolymerized alpha-chain and cross-linked gamma-gamma dimer. The fibrin peptide products are distinct from those produced by plasmin.

Morphological correlates of incipient arboreality and ornithophagy in island pitvipers, and the phylogenetic position of Bothrops insularis

Morphological differences between two semi-arboreal, bird-eating island pitvipers, Bothrops insularis and Gloydius shedaoensis, and their mainland relatives were investigated. Mitochondrial DNA sequence data for two genes show B. insularis to be rooted within B. jararaca. Bothrops insularis has a more anterior heart, a relatively longer tail, a longer head, and shorter fangs than B. jararaca. The greater head length is paralleled in the ecologically similar G. shedaoensis. Increased head size may represent an adaptation to the abundance of larger food items (migratory passerine birds), providing a selective advantage to snakes able to switch to larger prey at an earlier age. Furthermore, B. insularis and G. shedaoensis have converged on similar body sizes from opposite ancestral states. Other characters, including fang length, tail length and size of neonates do not show parallel variation in G. shedaoensis and B. insularis, suggesting that caution is required when interpreting character state shifts coinciding with ecological shifts in a single species only.

Activity pattern of Crotalus durissus (Viperidae, Crotalinae): Feeding, reproduction and snakebite

One hundred and seventy‐three adults and twenty‐six juveniles of Crotalus durissus were examined by removing the stomach contents and faecal material. Rattlesnakes were most active between April and May (autumn) (unimodal type), but most intensive feeding occurred during summer and autumn (February to May). Juveniles were observed to feed from late autumn (May) through the winter. Prey consisted of rodents (Cavia aperea, Rattus norvegicus and Mus sp.) and no ontogenetic change was observed in the diet. Feeding peaks precede vitellogenesis (autumn ‐ winter). Mated females continue feeding until ovulation (spring). It was observed that the biggest number of accidents were caused by snakes with stomach contents, especially males.

Origin and phylogenetic position of the Lesser Antillean species of Bothrops (Serpentes, Viperidae): biogeographical and medical implications

We use mitochondrial DNA sequences to infer the origin and phylogenetic position of the Lesser Antillean species of the pitviper genus Bothrops , B. caribbaeus and B. lanceolatus . The two species form a monophyletic group, which in turn forms the sister clade to the Bothrops asper-atrox complex. High levels of sequence divergence among the Caribbean species, and between them and the nearest mainland relatives, suggest a relatively ancient origin of these snakes. The hypothesis that the Lesser Antillean Bothrops are the result of a recent colonisation event from within the South American B. atrox complex is rejected, as is the hypothesis that they were introduced to their island habitats by aboriginal humans. The high level of morphological apomorphy displayed by B. lanceolatus suggests a stepping-stone colonisation, St. Lucia being colonised first and then Martinique from St. Lucia. The medical implications of these findings are discussed: a recent case of envenoming from Saint Lucia suggests that Bothrops caribbaeus causes the same thrombotic syndrome of envenoming as B. lanceolatus .

Natural History of the Vine Snake Oxybelis Fulgidus (Serpentes, Colubridae) From Brazil

ABSTRACT. Aspects of natural history of the vine snake Oxybelis fulgidus from the northern region of Brazil were inferred based on the analysis of 106 preserved specimens (55 males and 51 females), and from a review of records in the published literature. Males mature at smaller size than females. Differences in body length and shape were also found among adult females and males: adult females are larger in mean snout-vent length and have relatively larger heads and shorter tails. Females have an extended seasonal vitellogenic cycle from April to December (mainly throughout the dry season). Oviductal eggs and egg-laying were recorded from September to December, while births occurred from January to April. Fecundity varied from four to twelve eggs or vitellogenic follicles (n = 13), and was positively correlated with female body length. Testicle volume is significantly larger from February to July (mainly in April and May; end of the rainy season), however the deferent ducts diameter do not differ significantly throughout the year. We hypothesized that both males and females may have an associated reproductive pattern, both synchronized in the end of the rainy season. Oxybelis fulgidus feeds on lizards (mainly iguanian) and passerine birds. Apparently, females feed more frequently on birds than males.ABSTRACT. Aspects of natural history of the vine snake Oxybelis fulgidus from the northern region of Brazil were inferred based on the analysis of 106 preserved specimens (55 males and 51 females), and from a review of records in the published literature. Males mature at smaller size than females. Differences in body length and shape were also found among adult females and males: adult females are larger in mean snout-vent length and have relatively larger heads and shorter tails. Females have an extended seasonal vitellogenic cycle from April to December (mainly throughout the dry season). Oviductal eggs and egg-laying were recorded from September to December, while births occurred from January to April. Fecundity varied from four to twelve eggs or vitellogenic follicles (n = 13), and was positively correlated with female body length. Testicle volume is significantly larger from February to July (mainly in April and May; end of the rainy season), however the deferent ducts diameter do not differ signific...

A new technique to distinguish between immature and adult snakes and between males and females in six species of the neotropical colubrid snakes Philodryas

This paper reports the observed maximum and minimum SVLs of six species of the neotropical colubrid snakes Philodryas. A new sexing technique using the SVL: W‐ratio is presented, in addition to a proposed SVL critical value, which is useful in distinguishing between adult and immature snakes within the species studied. There is no sexual dimorphism of SVL x W for any of the studied species.

Morphology of Duvernoy's Glands and Maxillary Teeth and a Possible Function of the Duvernoy's Gland Secretion in Helicops modestus Günther, 1861 (Serpentes: Xenodontinae)

Abstract. We investigated the gross anatomy, histology and ultrastructure of Duvernoys glands and scanning electron microscopy of maxillary teeth of Helicops modestus, as well as its prey-handling behavior in laboratory. We later compared this histology with other species of Hydropsini. Duvernoys glands are located in the post-ocular region, immediately behind the supralabial gland. Each gland is connected to a pair of ungrooved rear fangs by a vestibule from which the secretion is drained. Histological analysis showed that the gland is wrapped by a layer of connective tissue and consists of a glandular body formed by prismatic cells organized in acini and a duct lined with columnar cells. The prismatic cells are positive to PAS and bromophenol blue, indicating glycoprotein content, whereas the columnar ductal cells are positive to PAS and alcian blue pH 2.5, indicating the presence of acid mucous. Transmission electron microscopy showed electron-dense, heterogeneous granules in the prismatic cells, whereas the granules of the columnar cells were electron-luscent and homogeneous. The Duvernoys glands of H. modestus are more similar to those of H. angulatus than any other species analyzed. Observations of prey-handling behavior showed that H. modestus strikes and holds fish in its mouth while repeatedly carrying out bilateral raking motions with both maxillae. Ingestion starts headfirst. We observed only a single episode of constriction. Snakes usually swallowed fish alive but clearly immobilized, suggesting that the primary function of the Duvernoys secretion is associated with the quiescence/immobilization of the fish prey.