A comparative study of growth, skeletal development and eggshell composition in some species of birds

Abstract

Some studies of birds suggest that the development of the skeleton may invoke a constraint on the rate of postnatal growth. Other studies have shown that the eggshell is the major source of calcium for skeletal development of the embryo. To test whether avian growth rate is indeed associated with different patterns of skeletal development, we compared the degree of skeletal ossification of the long bones of the wing and the leg of one slowly growing precocial species (quail Coturnix japonica) with that of two rapidly growing altricial species (starling Sturnus vulgaris and fieldfare Turdus pilaris). The degree of skeletal ossification of the long bones of the wings and legs of lines of quails that had undergone long-term selection for high-and low-growth rate, respectively, also was compared with a non-selected control line. Next, the fine structure of the inner eggshell surface (mammillary layer) of both pre-and post-incubated eggs, i.e. before and after embryonic development/calcium removal was compared. The data show that the skeleton of the more rapidly growing species and lines was less ossified than that of the more slowly growing ones. This difference appeared to be associated with different rates of calcium removal from the eggshell. Removal was more extensive in eggs of quail than in eggs of starling and fieldfare, i.e. more extensive in shells with a high number of mammillary tips per unit of surface area than in shells with a lower number. It is therefore concluded that growth rate is of fundamental importance for the pattern of skeletal development. Moreover, the mammillary density varies between different bird species, it is suggested, in order to support the different rates of calcium removal by developing embryos.

Variation of the Outer Circumferential Layer in the Limb Bones of Birds

“…The OCL is deposited at a much slower rate than is the fibro-lamellar core (Castanet et al 1996, de Margerie et al 2002, which suggests that its thickness may reflect the amount of residual growth. This conclusion is in general agreement with the proposition that slow growth is conducive to enhanced ossification (Blom & Lilja 2004), but raises a question of why the amount of residual growth would be larger in smaller birds, which grow faster (Starck & Ricklefs 1998). We feel that the answer lies in a more abrupt termination of fast growth.…”

“…We feel that the answer lies in a more abrupt termination of fast growth. However, since the relationship between the overall growth rate and ossification processes are only beginning to be understood at any developmental stage (Blom & Lilja 2004), more dedicated studies of residual growth with precisely aged individuals are needed in order to test this hypothesis.…”

Influence of Simulated Microgravity on Leg Bone Development in Japanese Quail Chicks

“…Growth is the most studied factor to estimate postnatal development of an individual (Ricklefs 1979;Blom and Lilja 2004). There are many studies that characterise the growth and development in Japanese quail under standard earth conditions (L ilja and Marks 1991;Aggrey 2003;Hyánková et al 2001).…”

Why do brood parasitic birds lay strong-shelled eggs?

“…The eggshell is, as the primary source of calcium, necessary for the development of embryonic skeleton and muscle tissue (Simkiss, 1961;Blom and Lilja, 2004). The remarkable behavior displayed by the chicks of evicting cuckoos soon after hatching in ejecting all host progeny may necessitate a more advanced development of its skeleton, i.e., a higher degree of bone ossification than should be expected for an altricial hatchling of similar size.…”

“…Such a comparison is lacking and this possibility remains to be tested. The degree of calcium mobilization from the eggshell by the developing embryo in birds is related to the speed of embryonic development, with the faster growing species consuming less of the eggshell calcium reserves and vice versa in species with slower development, while controlling for body size (Blom and Lilja, 2004). Since cuckoo embryos develop even faster than those of their passerine host species, a substantial amount of chick bone ossification as a result of elevated utilization of the eggshell calcium reserve is unlikely, although direct studies clearly are necessary.…”