ABSTRACT
The morphology of many organisms seems to be related to the environment they live in. Nonetheless, many snakes are so similar in their morphological patterns that it becomes quite difficult to distinguish any adaptive divergence that may exist. Many authors suggest that the microornamentations on the scales of reptiles have important functional value. Here, we examined variations on the micromorphology of the exposed oberhautchen surface of dorsal, lateral, and ventral scales from the mid-body region of Xenodontinae snakes: Sibynomorphus mikani (terricolous), Imantodes cenchoa (arboreal), Helicops modestus (aquatic) and Atractus pantostictus (fossorial). They were metallized and analyzed through scanning electron microscopy. All species displayed similar microstructures, such as small pits and spinules, which are often directed to the scale caudal region. On the other hand, there were some singular differences in scale shape and in the microstructural pattern of each species. S. mikani and I. cenchoa have larger spinules arranged in a row which overlap the following layers on the scale surface. Species with large serrate borders are expected to have more frictional resistance from the caudal-cranial direction. This can favor life in environments which require more friction, facilitating locomotion. In H. modestus, the spinules are smaller and farther away from the posterior rows, which should help reduce water resistance during swimming. The shallower small pits found in this species can retain impermeable substances, as in aquatic Colubridae snakes. The spinules adhering to the caudal scales of A. pantostictus seem to form a more regular surface, which probably aid their fossorial locomotion, reducing scale-ground friction. Our data appear to support the importance of functional microstructure, contributing to the idea of snake species adaptation to their preferential microhabitats.
A morfologia de muitos organismos parece estar relacionada ao ambiente em que eles vivem. No entanto, muitas serpentes são tão similares nos seus padrões morfológicos que se torna difícil distinguir qualquer divergência adaptativa existente. Muitos autores sugerem que as micro-ornamentações nas escamas de répteis possuem importante valor funcional. Neste trabalho, examinamos variações na micromorfologia da superfície oberhautchen exposta das escamas ventrais, laterais e dorsais da região medial de serpentes Xenodontinae: Sibynomorphus mikani (terrestre), Imantodes cenchoa (arbórea), Helicops modestus (aquática) e Atractus pantostictus (fossorial). Estas foram metalizadas e analisadas por microscopia eletrônica de varredura. Todas as espécies apresentaram microestruturas similares, tais como microcovas e espículas, que estão normalmente orientadas para a região caudal da escama. Por outro lado, houve algumas diferenças singulares em relação ao formato da escama e padrão microestrutural de cada espécie. S. mikani e I. cenchoa possuem espículas grandes arrumadas em linhas que sobrepõem as camadas seguintes da superfície da escama. Em espécies que possuem longas denticulações sobrepostas sobre as bordas posteriores das células, é esperado que haja uma maior resistência friccional da direção posterior para anterior das escamas. Isso pode favorecer a vida em ambientes que precisam de maior atrito, facilitando a locomoção. Em H. modestus, as espículas são menores e mais afastadas das linhas posteriores, o que pode reduzir o atrito com a água durante a natação. As microcovas mais rasas encontradas nesta espécie podem reter substâncias impermeáveis, como nas serpentes Colubridae aquáticas. As espículas que aderem às escamas caudais de A. pantostictus parecem formar uma superfície mais regular, o que provavelmente auxilia na locomoção fossorial, reduzindo o atrito com o solo. Nossos dados parecem corroborar a importância da microestrutura funcional, ...
Subject(s)
Animals , Female , Male , Colubridae/anatomy & histology , Ecosystem , Epidermis/ultrastructure , Colubridae/physiology , Microscopy, Electron, ScanningABSTRACT
Philodryas olfersii is found in South America, from Amazonas to Patagonia. It is important to characterize the venom of P. olfersii, who inhabits the North-East region of Argentina, since snake venoms are known to exhibit considerable variability in composition and biological activities. In this work, mice weighing 18-20 g (n = 4 for each experimental group) were used. For the edematogenic activity mice were injected s.c. in the right foot pad with 50 microl of solutions containing different amounts of venom, whereas the left foot pad was injected with 50 microl of PBS. Two hours after injection mice were killed by cervical dislocation and both feet were cut off and weighed individually. For the myotoxic activity mice were injected i.m. with 100 microl of solutions containing 40 microg of venom. Blood samples were extracted after 1, 3, 6, 8, 10, 12, 14, 16 and 24 h of venom injection to determinate serum CPK activity and mice were sacrificed at the same time intervals to obtain the inoculated gastrocnemius muscle. They were fixed with Bouin solution and stained with Hematoxylin-Eosin. Results showed that P. olfersii venom exhibits a high edematogenic activity (MED = 0.31 microg) and a moderate myotoxic activity. Myonecrosis reached its highest level after 12 h of venom injection as shown by plasmatic CPK levels (5,401 +/- 330 IU/l) and microscopic assay. It demonstrates the potential toxicity of the venom of P. olfersii, who inhabits the North-East region of Argentina. It also reinforces the original warning concerning the potential danger of bites by colubrids.
Subject(s)
Colubridae/physiology , Edema/chemically induced , Muscle, Skeletal/drug effects , Snake Venoms , Argentina , Colubridae/anatomy & histology , Creatine Kinase/blood , Edema/physiopathology , Salivary Glands/metabolism , Salivary Glands , Hemorrhage/chemically induced , Hemorrhage/physiopathology , Mice , Muscle, Skeletal/pathology , Muscle, Skeletal/physiopathology , Necrosis , Reaction Time/physiologyABSTRACT
A new species of Oxybelis is described from Isla de Roat n, Honduras. It differs from all species of Oxybelis in its tan to golden yellow coloration, in having a higher number of subcaudals as well as in other details of color and scutellation. The new species is closely related to O. fulgidus and is thought to be derived from a fulgidus-like ancestor (i.e., is the sister species to fulgidus) that has been isolated in the area of its present range probably since the very late Pliocene. The presence of a yellow population of Oxybelis on Isla de Roat n, Honduras, has long been known (Keiser 1969). The status of this insular population has remained uncertain pending the acquisition of additional material (Keiser 1969, Wilson and Meyer 1985). We recently visited Isla de Roatán a number of times and obtained a large series of additional specimens. After examining this new material, and the previously known specimens from this island, we believe that this population represents an undescribed taxon, which should be known as.
Subject(s)
Animals , Male , Female , Colubridae/anatomy & histology , HondurasABSTRACT
Uma nova espécie de Sibynomorphus é descrita com base em material proveniente das províncias argentinas de Jujuy, Salta, Chaco e Formosa e do Paraguay. Sibynomorphus lavillai sp. nov. é caracterizado pela presença de manchas sobre todo o corpo que alcançam a primeira fileira de escamas; estas manchas säo mais largas ou iguais ao inter-espaço anteriormente e mais estreitas posteriormente; pela fileira vertebral moderadamente alargada; pelo processo palatino estendendo-se até a extremidade anterior do maxilar e por ter de 47 a 61 subcaudais