1 Introduction
Ecological morphology also known as ecomorphology is a comparative
discipline with its central focus on the study of the interaction
between morphological and ecological diversity of organisms both in the
present and over evolutionary time (Kotrschal and Motta, 1991). The
morphological adaptations and ecological characteristics are closely
correlated because the interspecific morphological differences result
from the distinct selective pressures that they suffer (Beaumord and
Petrere Jr, 1994). Interactions between ecology and morphology can be
studied at multiple levels; among taxonomic unites or life history
intervals and between their phenotypic characteristics and their use of
ecological resources in a particular environment (Norton et al., 1995).
Skin as a phenotypic characteristic is a boundary between animals and
their environment, serving multiple roles such as acting in protection,
contributing to locomotion, maintaining moisture of the body, altering
the characteristics of the skin, helping in camouflage, capturing prey,
as well as contributing to physiological regulation, sensory detection,
respiration, and coloration (Abo-Eleneen and Allam, 2011; Vitt and
Caldwell, 2013). Snake’s scales are essentially made of folds of
epidermis and dermis; however, the scales themselves are essentially
originated from the epidermis. The number of scales neither increases
nor reduces as the snake matures over time, but the scales grow larger
and may undergo changing in shape as the snake exuviates (Swadźba and
Rupik, 2010; Abo-Eleneen and Allam, 2011). Most of the body surface in
reptiles is covered by these keratinized epidermal scales. Two keratin
types contribute to the formation of scales; the ß-keratin covering
entirely the scale’s surface, and α-keratin constructing the interscalar
space or suture. This distribution of keratin produces a durable and
protective scale surface with junctures between the scales that allow
flexibility and expansion of the skin (Vitt and Caldwell, 2013).
Generally called “Oberhautchen”, The ß-layer of scale is in direct
contact with the environment. The oberhautchen exhibits a particular
micro-structure in several squamate reptile groups and often is divided
into cell-like parts that may bear complex three-dimensional features.
The overall arrangement of these cells and their surface features are
called microornamentation (Ruibal, 1968; Stewart and Daniel, 1973;
Arnold, 2002). Scale shape, extent, and microornamentation can serve as
important charactersistics for taxonomic and systematic investigations
(Leydig, 1873; Picado, 1931; Price, 1982). Microornamantation
variability may be arises from adaptation pressures directly acting upon
scales, and could play important taxonomic role in discriminating
generic and specific, but not family categories (Rocha-Barbosa and
Moraes e Silva, 2009; Crowe-Riddell et al., 2016). Several studies have
surveyed the association of scale microornamentation and systematics and
ecological variation. According to these studies, since the
ultrastructural features of scales might be relatively free from direct
adaptational pressures, they could well be more reliable indicators of
interspecific relationships (Burstein et al., 1974). Price (1982)
reported that microornamentation patterns reflect the phylogenetic
relationships, rather than environmental or habitat impacts and that
there was no evidence for a correlation between microornamentation and
habitats or environment. Nevertheless, microstructures have been used as
tools in ontogenetic and/or evolutionary studies of squamates (Harvey
and Gutberlet Jr, 1995). Gower (2003) and Pough et al. (2003) have found
strong correlation between scale microornamentation and ecology,
emphasizing that certain kinds of micro-ornamentation are associated
with certain habitats.
Solar radiation consist of a wide range of wavelengths and affect all
creatures on Earth. Sunlight primarily are divided into visual,
ultraviolet and infrared wavelenghts that absorbed or reflected by
animate and inanimate surfaces. In animals the skin is in direct contact
with the environment and play an important role in absorbing or
reflecting visible and invisible light. Many invertbrates and vertbrates
have the ability to perceive UV light and also possess UV-reflective
structures on their body surface (Shi and Yokoyama, 2003; Modarressie et
al., 2013). The roles of UV in vision are manifold from animal
communication, guiding navigation and orientation behavior, to detecting
food and potential predators (Modarressie et al., 2013).
P. persicus and P. fieldi inhabit sandy and rocky terrains
with moderate vegetation of bushes and grasses. They are nocturnal in
habits, retreats during the day into crevices among rocks or burrows in
comparatively hard soil near roots of bushes. Their diet consists of
deserticolous lizards, mice, and arthropods (Khan, 2011). The immediate
habitat of the P. urarachnoides contains hill and high grounds
mostly composed of gypsum. It prefers deep cracks and holes in the
gypsum substrates to benefit moisture and coolness in the warm months of
summer (Fathinia et al., 2009). Its main diet in adulthood is migratory
passerines (Fathinia et al., 2015). E. macmahonii is
morphologically adapted to live in fine loose sand of shifting dunes.
Its habitat is without any mentionable vegetation, except for very
sparse growth of stunted bushes and grasses (Khan, 2011). E.
carinatus recorded from sandy and rocky alluvial habitats, with sparse
xerophytic to moderately dense grass and scrub vegetation. In
mountainous habitats it lives under rock blocks, while in
sub-mountainous regions inhabits hedges and other scrubby vegetation,
noticeably avoiding marshy areas and very dense vegetation (Khan, 2011).Cerastes gasperettii as a nocturnal true desert snake prefer
sandy soil regions with high temperature and some vegetation as
shelters (Sadoon and Paray., 2016).Eirenis rafsanjanicus inhabits mountain areas with substrates
compose of clay soil covering with numerous pebbles, and annual and
perennial plants (Akbarpour et al., 2020). Lythorhynchus maynardiinhabits sandy terrains covered by bushes. The vegetation is dominated
by Tamarix sp. and a syntopic snake species is Echis
carinatus.
The present study is aimed to: 1) compare microstructure variation in
scale surface using SEM, 2) discover variation in light reflection of
scales among snake species in two families and five genera occupying
both the same and different microhabitats, and 3) explore the
taxonomic-ecomorphological association in the concerned species.