35
terrestrial environment (see for review Brischoux and Bonnet 2009 ). Studies about
the mechanical properties of sea snake skin (Jyane 1988 ) are of importance for
bionics, as well as for biomaterials science. For example, different variations in
the surface hydrophobic properties of the sea snake skin in seawater are currently
the subject of ongoing investigations (Lillywhite et al. 2009 ). It was shown that the
external skin surfaces of marine Laticauda snakes studied by Lillywhite and coworkers are hydrophobic. Thus, the skin can interact with a microfi lm of air at
the surface of the stratum corneum. Probably, “variation in the nature of this air fi lm
is correlated with species differences in the effl ux of water when these snakes are
aquatic” (Lillywhite et al. 2009 ).
Sea snakes are known to shed their skin with relative frequency. Probably due to
hydration damage of corresponding layers of their skin, which seems inevitable
over time (Tu et al. 2002 )? Moreover effective hydrophobic properties of the skin
surfaces can be changed due frequent shedding (Lillywhite et al. 2009 ). Also the
presence of neuronal processes, which is almost certainly important for detecting
vibrations in the aquatic environment cannot be excluded (Lillywhite et al. 2009 ).
The Crocodilians (Order Crocodylia) include crocodiles, gavials, caimans and
alligators. Altogether – 23 species. None of them is truly distributed in marine environment. Only the saltwater or “estuary” crocodile ( Crocodylus porosus ) habituates
in brackish waters of south-east Asia and Australia (Martin 2008 ). Species like
Crocodylus johnstoni or C. acutus have been found in tidal waters (Rasmussen et al.
2011a , b ). Crocodilians are usually distributed in tropical waters. Alligators in USA
and China live, however, in temperate climates. Crocodylians are cold-blooded,
amphibious, egg-laying reptiles with 4 legs, partially webbed feet, and a long
powerful tail. Exemplars of saltwater crocodile C. porosus can be up to 6.2 m long
(Montague 1983 ). The weight of a 6 m adult is 1,100 kg. Their external skin has
scales, often strengthened by bone deposits (osteoderms), and they have a fl attened,
tooth-lined skull with broad or narrow snouts. Crocodilians’ long fl attened tails
possess morphological features that enable them to swim effi ciently through
water. These reptiles breathe through nostrils located at the top of their head.
The presence of the lingual salt glands which help to secrete excess of salt ions is
known in crocodiles (Grigg et al. 1980 ; Taplin and Grigg 1981 ; Taplin 1984 , 1985 ;
Franklin and Grigg 1993 ). These glands in crocodilians are stimulated by a salt load,
and their morphology is conserved (Kirschner 1980 ; Mazzotti and Dunson 1984 ).
From physiological point of view “these tissues are typifi ed by their abundance of ion
pumps, including Na
+ /K
+
-ATPase (NKA), a basolateral, transmembrane ion pump
responsible for the maintenance of cellular electrochemical gradients through the
movement of Na
+ and K
+ ions against their osmotic gradients,” (Cramp et al. 2010 ).
The enzyme Na
+ /K
+ -ATPase plays an important role in salt regulation. Its
abundance, distribution, activity, and expression in the salt glands of C. porosus
increase following chronic saltwater acclimation (Cramp et al. 2010 ). It was
demonstrated that the salt glands of this species are “phenotypically plastic, both
morphologically and functionally and acclimate to changes in environmental salinity”
(Cramp et al. 2008 ). Similar glands are known also for Nile crocodile; however
they may be not as effi cient as those in the C. porosus (Taplin and Loveridge 1988 ).
1.2 Part I: Biomaterials of Vertebrate Origin. An Overview
terrestrial environment (see for review Brischoux and Bonnet 2009 ). Studies about
the mechanical properties of sea snake skin (Jyane 1988 ) are of importance for
bionics, as well as for biomaterials science. For example, different variations in
the surface hydrophobic properties of the sea snake skin in seawater are currently
the subject of ongoing investigations (Lillywhite et al. 2009 ). It was shown that the
external skin surfaces of marine Laticauda snakes studied by Lillywhite and coworkers are hydrophobic. Thus, the skin can interact with a microfi lm of air at
the surface of the stratum corneum. Probably, “variation in the nature of this air fi lm
is correlated with species differences in the effl ux of water when these snakes are
aquatic” (Lillywhite et al. 2009 ).
Sea snakes are known to shed their skin with relative frequency. Probably due to
hydration damage of corresponding layers of their skin, which seems inevitable
over time (Tu et al. 2002 )? Moreover effective hydrophobic properties of the skin
surfaces can be changed due frequent shedding (Lillywhite et al. 2009 ). Also the
presence of neuronal processes, which is almost certainly important for detecting
vibrations in the aquatic environment cannot be excluded (Lillywhite et al. 2009 ).
The Crocodilians (Order Crocodylia) include crocodiles, gavials, caimans and
alligators. Altogether – 23 species. None of them is truly distributed in marine environment. Only the saltwater or “estuary” crocodile ( Crocodylus porosus ) habituates
in brackish waters of south-east Asia and Australia (Martin 2008 ). Species like
Crocodylus johnstoni or C. acutus have been found in tidal waters (Rasmussen et al.
2011a , b ). Crocodilians are usually distributed in tropical waters. Alligators in USA
and China live, however, in temperate climates. Crocodylians are cold-blooded,
amphibious, egg-laying reptiles with 4 legs, partially webbed feet, and a long
powerful tail. Exemplars of saltwater crocodile C. porosus can be up to 6.2 m long
(Montague 1983 ). The weight of a 6 m adult is 1,100 kg. Their external skin has
scales, often strengthened by bone deposits (osteoderms), and they have a fl attened,
tooth-lined skull with broad or narrow snouts. Crocodilians’ long fl attened tails
possess morphological features that enable them to swim effi ciently through
water. These reptiles breathe through nostrils located at the top of their head.
The presence of the lingual salt glands which help to secrete excess of salt ions is
known in crocodiles (Grigg et al. 1980 ; Taplin and Grigg 1981 ; Taplin 1984 , 1985 ;
Franklin and Grigg 1993 ). These glands in crocodilians are stimulated by a salt load,
and their morphology is conserved (Kirschner 1980 ; Mazzotti and Dunson 1984 ).
From physiological point of view “these tissues are typifi ed by their abundance of ion
pumps, including Na
+ /K
+
-ATPase (NKA), a basolateral, transmembrane ion pump
responsible for the maintenance of cellular electrochemical gradients through the
movement of Na
+ and K
+ ions against their osmotic gradients,” (Cramp et al. 2010 ).
The enzyme Na
+ /K
+ -ATPase plays an important role in salt regulation. Its
abundance, distribution, activity, and expression in the salt glands of C. porosus
increase following chronic saltwater acclimation (Cramp et al. 2010 ). It was
demonstrated that the salt glands of this species are “phenotypically plastic, both
morphologically and functionally and acclimate to changes in environmental salinity”
(Cramp et al. 2008 ). Similar glands are known also for Nile crocodile; however
they may be not as effi cient as those in the C. porosus (Taplin and Loveridge 1988 ).
1.2 Part I: Biomaterials of Vertebrate Origin. An Overview