93
random orientation. Also, the surface osteoblasts, which synthesize bone on surfaces
in a well oriented lamellar array, play very important role here (see for details Shapiro
2008 ). I absolutely agree with Elia Beniash that “understanding basic principles of
formation, structure and functional properties of different bone types might lead to
novel bioinspired strategies for material design, and better treatments for diseases of
the mineralized tissues,” (Beniash 2011 ).
Acellular Bone “ Aspidin ” is an example of earliest bone and represents specifi c
acellular, matrix-rich (presumably consisting of collagen fi bres) mineralized tissue
(for review see Donoghue and Sansom 2002 ; Donoghue et al. 2006 ). According to
Tarlo ( 1963 ), “aspidin was the ‘ancestor’ of true, cellular bone, which evolved
sometime after the origin of vertebrates” (Ruben and Bennett 1987 ). Acellular bone
has a plesiomorphic character in vertebrates found in both primitive craniates and
vertebrate lineages (Ørvig 1965 , 1989 ) including teleost fi sh (Moss 1960 , 1961 ,
1962 ). In a group of fossil marine jawless vertebrates which lived from 470 to
370 Ma ago and known as pteraspidomorphs, “aspidin is present both in the form of
bone of attachment associated with the superfi cial dentine-enameloid tubercles, and
comprises the whole of the underlying middle ‘spongy’ and basal ‘lamellar’ layers
of the dermoskeleton” (Donoghue 2002 ; Donoghue et al. 2006 ).
Mapping acellular bone on the teleost phylogeny suggests an increasing trend
toward acellularity, with the superorder Percomorpha containing a little more than
85 % of known acellular bony fi shes (Kranenbarg et al. 2005 ). The multiple origins
of acellularity within teleosts (Meunier et al. 2004 ) indicate a possible selective
advantage of this type of bone. However, there is no consensus yet concerning the
possible functional role of acellular bone, as the factors that have been investigated
such as environment, activity level and gross morphology do not predict the presence of acellularity (Moss and Freilich 1963 ; Moss 1965 ). Therefore, the adaptive
signifi cance or selective pressures that lead to the repeated evolution of acellular
bone in the teleosts remain unclear.
Recently, Horton and Summers ( 2009 ) carried out series of comparative tests
concerning material properties (elastic modulus) of acellular and cellular bone.
They used a three-point bending method to test the hypothesis that the material
stiffness of cellular bone is lower than that of acellular bone. These researchers
suggested that material properties were a selective pressure in the evolution of
acellular bone as specialized skeletal material. The acellular ribs of great sculpin
( Myoxocephalus polyacanthocephalus ) were used in these experiments. It was
reported that “contrary to their expectations, acellular bone was not stiffer by
virtue of fewer lacunae but instead falls at the very low end of the range of
stiffness seen in cellular bone. There remains the possibility that other properties
(e.g. fatigue resistance, toughness) are higher in acellular bone” (Horton and
Summers 2009 ).
Thus, according to Donoghue et al. 2006 “it appears that cellular bone evolved
from an acellular bone, and acellularity has arisen secondarily in a number of
instances, often through distinct developmental pathways”. Is it true that especially
the collagenous matrix plays the crucial role in bone development? Intriguingly, the
3.1 Bone
random orientation. Also, the surface osteoblasts, which synthesize bone on surfaces
in a well oriented lamellar array, play very important role here (see for details Shapiro
2008 ). I absolutely agree with Elia Beniash that “understanding basic principles of
formation, structure and functional properties of different bone types might lead to
novel bioinspired strategies for material design, and better treatments for diseases of
the mineralized tissues,” (Beniash 2011 ).
Acellular Bone “ Aspidin ” is an example of earliest bone and represents specifi c
acellular, matrix-rich (presumably consisting of collagen fi bres) mineralized tissue
(for review see Donoghue and Sansom 2002 ; Donoghue et al. 2006 ). According to
Tarlo ( 1963 ), “aspidin was the ‘ancestor’ of true, cellular bone, which evolved
sometime after the origin of vertebrates” (Ruben and Bennett 1987 ). Acellular bone
has a plesiomorphic character in vertebrates found in both primitive craniates and
vertebrate lineages (Ørvig 1965 , 1989 ) including teleost fi sh (Moss 1960 , 1961 ,
1962 ). In a group of fossil marine jawless vertebrates which lived from 470 to
370 Ma ago and known as pteraspidomorphs, “aspidin is present both in the form of
bone of attachment associated with the superfi cial dentine-enameloid tubercles, and
comprises the whole of the underlying middle ‘spongy’ and basal ‘lamellar’ layers
of the dermoskeleton” (Donoghue 2002 ; Donoghue et al. 2006 ).
Mapping acellular bone on the teleost phylogeny suggests an increasing trend
toward acellularity, with the superorder Percomorpha containing a little more than
85 % of known acellular bony fi shes (Kranenbarg et al. 2005 ). The multiple origins
of acellularity within teleosts (Meunier et al. 2004 ) indicate a possible selective
advantage of this type of bone. However, there is no consensus yet concerning the
possible functional role of acellular bone, as the factors that have been investigated
such as environment, activity level and gross morphology do not predict the presence of acellularity (Moss and Freilich 1963 ; Moss 1965 ). Therefore, the adaptive
signifi cance or selective pressures that lead to the repeated evolution of acellular
bone in the teleosts remain unclear.
Recently, Horton and Summers ( 2009 ) carried out series of comparative tests
concerning material properties (elastic modulus) of acellular and cellular bone.
They used a three-point bending method to test the hypothesis that the material
stiffness of cellular bone is lower than that of acellular bone. These researchers
suggested that material properties were a selective pressure in the evolution of
acellular bone as specialized skeletal material. The acellular ribs of great sculpin
( Myoxocephalus polyacanthocephalus ) were used in these experiments. It was
reported that “contrary to their expectations, acellular bone was not stiffer by
virtue of fewer lacunae but instead falls at the very low end of the range of
stiffness seen in cellular bone. There remains the possibility that other properties
(e.g. fatigue resistance, toughness) are higher in acellular bone” (Horton and
Summers 2009 ).
Thus, according to Donoghue et al. 2006 “it appears that cellular bone evolved
from an acellular bone, and acellularity has arisen secondarily in a number of
instances, often through distinct developmental pathways”. Is it true that especially
the collagenous matrix plays the crucial role in bone development? Intriguingly, the
3.1 Bone