Ultrastructural Scale Patterns in Nerodia and Thamnophis

Chiasson, Robert B.; Lowe, Charles H.

doi:10.2307/1564016

Cited by 26 publications

(21 citation statements)

References 9 publications

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“…Smaller spinules, of serrated aspect, disposed in overlying rows, much farther from one another, possibly help in diminishing the resistance generated by water movement, and the quite shallow pits on the scale surfaces suggest an improvement in the snake's hydrodynamic performance. Chiasson and Lowe (1989) have suggested that the pits present on the scale surface of Asiatic aquatic Colubridae may contain impermeabilizing substances. These authors based themselves on the discovery of fatty acids present in the surface of these snakes' scales.…”

Section: Discussionmentioning

confidence: 99%

“…Several recent studies have suggested a functional significance for microornamentation (Manderson, 1966;Porter, 1967;Steward and Daniel, 1973;Gans and Baic, 1977;Smith et al, 1982;Renous, et al,1985;Gower, 2003) or have simply described microanatomy (Arroyo and Cerdas, 1985;Chiasson and Lowe, 1989;Velloso et al, 2005). Microstructures have also been used as tools in taxonomy (Hogue and Santos 1953;Dowling et al, 1972;Stewart and Daniel, 1975) and in ontogenetic and/or evolutionary studies of squamates (Peterson, 1985;Harvery 1993;Harvery and Gutberlet Jr, 1995).…”

Section: Introductionmentioning

confidence: 99%

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Analysis of the microstructure of Xenodontinae snake scales associated with different habitat occupation strategies

Barbosa

2009

Braz. J. Biol.

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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.Keywords: scales, microstructure, snakes, Xenodontinae, SEM. provavelmente auxilia na locomoção fossorial, reduzindo o atrito com o solo. Nossos dados parecem corroborar a importância da microestrutura funcional, contribuindo para a hipótese de adaptação das espécies de serpentes aos seus microhabitats preferenciais. Análise da microestrutura de escamas de serpentes Xenodontinae em associação à ocupação de diferentes microhabitatsPalavras-chave: escamas, microestrutura, serpentes, Xenodontinae, MEV.sisted of museum specimens from the Alphonse Richard Hoge collection at the Instituto Butantan (IB).In an attempt to avoid errors derived from phylogenetic factors, the species chosen all belong to the same subfamily (Xenodontinae).Dorsal, lateral and ventral scales were taken from the mid-region of the body of five adult individuals (males, 2 scales, and females, 3 scales) of each species. The scales were placed in numbered tubes and duly identified for each species. Distilled water and neutral soap were added to the tubes. Each tube was manually shaken for about 1 minute to remove any probable impurities. Scales were then removed...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of the microstructure of Xenodontinae snake scales associated with different habitat occupation strategies

Barbosa

2009

Braz. J. Biol.

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“…One problem with this hypothesis is that the possible pores in uropeltids are perhaps too small to allow even the thinnest of liquids to be extruded. Chiasson and Lowe (1989) speculated that depressions on the oberhautchen surface of aquatic colubrid snakes may hold possibly waterproofing oils, and this was supported by the discovery of the esters of at least two fatty acids in material covering the surface of scales of these snakes, and by the fatty nature of the underlying mesos layer in squamates. In this context, it might also be noted that the European colubrid Malpolon monspessulanus is known to wipe a liquid secretion from a pair of snout glands over its body (e.g., Arnold, 2002b) but, as far as I am aware, its scale microornamentation has not been investigated.…”

Section: Functionmentioning

confidence: 99%

Scale microornamentation of uropeltid snakes

Gower

2003

Journal of Morphology

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Microornamentation was examined on the exposed oberhautchen surface of dorsal, lateral, and ventral scales from the midbody region of 20 species of the fossorial snake family Uropeltidae and seven species of fossorial scolecophidian and anilioid outgroups. No substantial variation was observed in microornamentation from the different areas around the midbody circumference within species. All oberhautchen cells were flat and exhibited no major surface features other than occasional posterior margin denticulations, small pores/pits, and narrow, low ridges. This is largely consistent with the hypothesis that friction reduction and dirt shedding are the main selective pressures on microornamentation, given that reducing shine is not of key importance in fossorial animals. Variations among taxa were observed in the shape and size of oberhautchen cells, in the presence of pores/pits, in the presence and size of denticulations on posterior cell margins, and in the level or imbricate nature of cell borders. Six microornamentation characters were formulated, scored, and plotted onto a selected phylogeny. Character evolution and phylogenetic signal were explored, accepting the incomplete understanding of intraspecific variation and of uropeltid interrelationships. There is evidence that all but one of these characters evolved homoplastically, probably by multiple independent origin. There is no clear evidence for character state reversal, but greater phylogenetic resolution is required to test this further. Phylogenetic signal appears to exist in some instances, including possible microornamentation synapomorphies for Uropeltidae and Melanophidium. These derived character states are found elsewhere within Squamata. A microornamentation of narrow, finely, and regularly spaced ridges is associated with scale iridescence. These ridges, and possibly pores/pits, are also associated with scales that are less wettable, and that therefore might be expected to be better at shedding dirt in moist conditions. Testable hypotheses are presented that might explain minor variations in the form of ridges and pits among uropeltids.

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“…The smooth scales of laticaudine sea snakes may reduce the possibility of the skin being colonized by marine algae and other organisms (McCarthy, 1987) and the very rough scale surfaces on the tail of uropeltid snakes encourages the accumulation of a plug of earth which helps prevent predators following the snakes into their burrows (Gans and Baic, 1977). Some partly aquatic natricine snakes in the genera Nerodia and Thamnophis have pores on their dorsal body scales that exude lipids that collect in hollows in the scale microornamentation, perhaps helping to make the skin waterproof (Chiasson and Lowe, 1989). Digital setae in many geckoes and some other lizards facilitate adhesion while climbing.…”

Section: Factors That May Cause Evolutionary Changementioning

confidence: 99%

“…For instance, publications dealing with dorsal body scales include: Bryant et al (1967), Monroe and Monroe (1967), Ruibal (1968), Stewart and Daniel (1972, 1975, Burstein et al (1974), Cole and van Devender (1976), Sammartano (1976), Gans and Baic (1977), Gasc and Renous (1980), Groombridge (1980), Wuest (1982, 1983), Price (1982Price ( , 1983Price ( , 1989, Peterson (1984a,b), Peterson and Bezy (1985), Renous et al (1985), Bea (1986), Bowker et al (1987), McCarthy (1987), Stille (1987), Bezy and Peterson (1988), Irish et al (1988), Vaccaro et al (1988), Chiasson and Lowe (1989), Lang (1989), Price and Kelly (1989), Renous and Gasc (1989), Harvey (1993), and Harvey and Gutberlet (1995).…”

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confidence: 99%

History and function of scale microornamentation in lacertid lizards

Arnold

2002

Journal of Morphology

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Differences in surface structure (ober-hautchen) of body scales of lacertid lizards involve cell size, shape and surface profile, presence or absence of fine pitting, form of cell margins, and the occurrence of longitudinal ridges and pustular projections. Phylogenetic information indicates that the primitive pattern involved narrow strap-shaped cells, with low posteriorly overlapping edges and relatively smooth surfaces. Deviations from this condition produce a more sculptured surface and have developed many times, although subsequent overt reversals are uncommon. Like variations in scale shape, different patterns of dorsal body microornamentation appear to confer different and conflicting performance advantages. The primitive pattern may reduce friction during locomotion and also enhances dirt shedding, especially in ground-dwelling forms from moist habitats. However, this smooth microornamentation generates shine that may compromise cryptic coloration, especially when scales are large. Many derived features show correlation with such large scales and appear to suppress shine. They occur most frequently in forms from dry habitats or forms that climb in vegetation away from the ground, situations where dirt adhesion is less of a problem. Microornamentation differences involving other parts of the body and other squamate groups tend to corroborate this functional interpretation. Microornamentation features can develop on lineages in different orders and appear to act additively in reducing shine. In some cases different combinations may be optimal solutions in particular environments, but lineage effects, such as limited reversibility and different developmental proclivities, may also be important in their genesis. The fine pits often found on cell surfaces are unconnected with shine reduction, as they are smaller than the wavelengths of most visible light.

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Ultrastructural Scale Patterns in Nerodia and Thamnophis

Cited by 26 publications

References 9 publications

Analysis of the microstructure of Xenodontinae snake scales associated with different habitat occupation strategies

Analysis of the microstructure of Xenodontinae snake scales associated with different habitat occupation strategies

Scale microornamentation of uropeltid snakes

History and function of scale microornamentation in lacertid lizards

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