Reptile and Bird Eggs: An Introduction

Reptile and Bird Eggs: An Introduction For a long time now scientist have been studying all types of reptiles since before man walked the earth. When comparing todays modern reptile eggs, and bird eggs we see many differences that are still being studied. Birds are almost found everywhere, while most reptile are only in specific location. They both lay eggs that are diverse internally and externally. We will look at different species of birds and reptiles to find out more about their extraordinary reproductive system and the eggs themselves. Birds Feathered, winged egg laying vertebrates. (Irie, 2010) Approximately 10,000 living species (Deeming, 2007) The only branch of dinosaurs to have survived the Cretaceous Paleogene extinction 65.5 million years ago. (Dolnik, 2001) Scientists theorize that birds evolved from dinosaurs. (Dolnik, 2001) Archaeopteryx lithographica  had two strong legs and walked as a bird does. Its skeleton was reptilian and had the feathers of a bird. (Dolnik, 2001) There are two theories as to why feathers would have developed in the evolution of birds. One is that because the ancestors of birds where becoming warm blooded, they needed the insulation of feathers. Another is that they develop because of a need for flight and gliding. (Dolnik, 2001) This capability to fly gave birds the competitive edge as they could travel over greater distances and areas seeking food. This also permitted them to live in places unreachable to other animals. (Deeming, 2007)   Bird Eggs Bird eggs  are laid by females and  incubated  for a time that changes according to the species. (Deeming, D C; Birchard, G F 2007) A single bird hatches from each egg. (Deeming, D C; Birchard, G F 2007) Lay very typical amniote eggs  with calcified shells. (Dove, 2012) Birds brood their eggs until hatching. Some bird species are naked and helpless at birth, and must be fed by their parents; these birds are called  altricial. (Dove, 2012) Some birds lay eggs even when not fertilized (Deeming, 2007) Cormorant eggs are rough and chalky (Dove, 2012) Tinamou  eggs are shiny (Nathan, 1999) Duck  eggs are oily and waterproof (Nathan, 1999) Cassowary eggs are heavily pitted (Nathan, 1999) Tiny pores in a bird eggshell allow the embryo to breathe. (Irie, 2010) The majority bird eggs have an  oval shape, with one end rounded and the other more pointed. (Deeming, 2007) The eggs wall is shapeable(Deeming, 2007) Numerous animals feed on eggs. (Dove, 2012) Humans have a long history of both eating wild bird eggs and raising birds for farmed eggs for consumption. (Dove, 2012) Brood parasitism  occurs in birds when one species lays its eggs in the nest of another. In some cases, the hosts eggs are removed or eaten by the female, or expelled by her chick. (Irie, 2010) Reptiles Reptiles  are members of the  class  Reptilia  comprising the  amniotes  that are neither  birds  nor  mammals. (Rafferty, 2012) The amniotes are the  vertebrates  with eggs featuring an  amnion, a double membrane that allows the  embryo  to breathe effectively on land. (Dolnik, 2001) Living reptiles are  cold-blooded  and bear scales. (Rafferty, 2012) Reptiles originated around 320-310 million years ago during the  Carboniferous  period, having evolved from highly developed  reptile like amphibians  that became gradually more adapted to life on dry land. (Dolnik, 2001) There are many extinct groups, including  dinosaurs,  pterosaurs, and ichthyosaurs. (Dolnik, 2001) There are 8,240 species of reptiles in the world, inhabiting every continent except Antarctica. (shine, 1999) Lizards and snakes have a single sheet of overlapping scales. (Rafferty, 2012) Other reptiles grow plates. (Rafferty, 2012) The main purpose of the skin is to keep water in the animals body. (Shine, 1999) Reptiles can go without water for long periods, and many species prosper in deserts. (Shine, 1999) Reptiles, like birds, have deliberate control over the muscles in their eyes, which determine their pupil size. They are able to constrict or dilate their pupils at will, not just in reaction to light. (Dove, 2012) The brain of a reptile is not over 1 percent of his body mass. Unlike amphibians, however, the reptilian brain has two hemispheres. (Nathan, 1999) The nervous systems of reptiles are adequately complex and similar to those of mammals. (Rafferty, 2012) Reptile eggs The eggs laid by some reptiles even smaller, and those of insects and other  invertebrates  can be much smaller still. (Nathan, 1999) Chicken eggs have a hard shell while reptile eggs have a soft, leathery shell. (Qualls, 2002) Large macrolecithal eggs, develop independent of water. (Deeming, D C; Birchard, G F 2007) Like amphibians,  amniotes  are air-breathing  vertebrates, but they have complex eggs including an  amniotic membrane. (Qualls, 2002) Dinosaurs laid eggs, some of which have been preserved as petrified fossils. (Dolnik, 2001) Macrolecital eggs are found in  reptiles(Deeming, 2007) Oviparity is typical of birds and reptiles. (Nathan, 1999) Literature Review Dove (2012). Consumption of bird eggs by invasive Burmese Pythons in Florida. Burmese Pythons have been reported to consume 25 species of adult birds in Everglades National Park, Florida but until now no records documented this species eating bird eggs. Deeming, D C; Birchard, G F (2007). Allometry of egg and hatchling mass in birds and reptiles: roles of developmental maturity, eggshell structure and phylogeny. This article looks at a wide range of birds and  reptiles using regression analysis, In birds, initial  egg  mass (IEM) at laying is the most important factor affecting phylogenetic relatedness. For all  reptile  species, IEM phylogenetic relatedness did not. This article also observed for the relationship between  eggmass and incubation period. Shine, R,(1999). Egg-laying reptiles in cold climates: determinants and consequences of nest temperatures in montane lizards. This article studies reptilian life-history and evolution. Many of these species avoid low incubation temperatures by selecting warm nest-sites, reptiles  may adapt to low-temperature incubation rather than avoid it. Bassiana  eggs  tolerate higher temperatures than do Nannoscincus  eggs, but do not develop as rapidly at low temperatures. Dolnik, (2001) Allometry of egg mass, clutch size and total clutch mass in dinosaurs: comparison with modern reptiles and birds. In this article the author presents for the first time empirical allometrical equations matching the mass of dinosaurs with the mass of their  eggs, clutch size and its total mass. Contrast of these equations with those that were planned for modern taxa of  reptiles  and birds shows that dinosaurs can be characterized by intermediate value of allometry index. Nathan, R, and Y. L. Werner (1999). Reptiles and breeding birds on Mt. Hermon: Patterns of altitudinal distribution and species richness This article reviews and analyzes the altitudinal distribution of  reptiles  and breeding  birds on Mt. Hermon over the distance of 2814 m. Species diversity was larger in breeding  birds  than in  reptiles  , declining with rising altitude in both groups, but more sharply so in  birds. The scientist explain that the generalization of vegetation arrangement with increasing altitude may explain this variation, because  birds probably better use the three-dimensionality of densely-vegetated habitats that take over low elevations. C. P. Qualls,  R. M. Andrews (2002). Maternal body volume constrains water uptake by lizard eggs  in utero In this article observations showed that some characteristic of retention in the oviductal environment restricts the amount of water eggs can absorb prior to oviposition. This paper presents proof, from two species of  Sceloporus  lizard, supporting the hypothesis that restricted space within the mothers body cavity physically constrains the ability of eggs to expand, and thereby their ability to absorb water. If such a constraint on water uptake is extensive, it can have significant implications for the understanding the costs of reproduction, and the determinants of reproductive output in squamate reptiles. Anthony R. Rafferty and Richard D. Reina, (2012). Arrested embryonic development: a review of strategies to delay hatching in egg-laying reptiles. This article discusses arrested embryonic development connecting the down regulation or cessation of active cell division and metabolic activity, and the ability of an animal to arrest embryonic development results in temporal plasticity of the duration of embryonic period. Arrested embryonic development is a significant reproductive strategy for egg-laying animals that provide no parental care after oviposition. Irie,Toshiaki, (2010). Retinoid storage in the egg of reptiles and birds In this article storage of retinal has been established in  eggs  from a variety of anamniotic vertebrates, but the retinoid-storage state in  eggs  of oviparous  amniotic  vertebrates (reptiles and  birds) has not been clarified in detail. Scientist studied four reptilian and five avian species and established that retinal was commonly stored in their  egg  yolk. In addition, retinal was the major retinoid in reptilian eggs, with only low levels of retinol, while major amounts of retinol as well as retinal were stored in avian  eggs. In equally reptilian and avian  eggs, retinal was frequently bound to proteins, which were assumed to be homologous to the proteins that attach retinal in the  eggs  of anamniotic vertebrates.