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D C Deeming

Publications and source records attributed to D C Deeming.

30 records · Page 2Linked to original sources
PubMed1995

The hatching sequence of ostrich (Struthio camelus) embryos with notes on development as observed by candling.

1. The hatching sequence of the ostrich (Struthio camelus) was determined by observing embryos during candling, those in the process of hatching and in dead-in-shell eggs. 2. Candling showed that there was a progressive increase in dark shadowing within the egg but fine details were not easily seen. Nevertheless candling is considered to be an important method of assessing development of ostrich eggs during incubation. 3. The ostrich embryo adopts a hatching position and follows a hatching sequence different from that of the fowl. During internal pipping, the air space is pulled towards the beak in the former but the beak moves to the air space in the latter. The right foot has an important role in breaking the shell during hatching. 4. The hatching process is considered to reflect an adaptation to the egg having a hard, brittle shell. 5. Malpositions in the ostrich may have been misinterpreted in the past because of the unusual hatching position. The commonest malposition described here was head-in-the-small-end.

Animals↗
PubMed1995

Mathematical models for growth in alligator (Alligator mississippiensis) embryos developing at different incubation temperatures.

A variety of model-based (growth models) and model-free (cubic splines, exponentials) equations were fitted using weighted-nonlinear least squares regression to embryonic growth data from Alligator mississippiensis eggs incubated at 30 and 33 degrees C. Goodness of fit was estimated using a chi 2 on the sum of squared, weighted residuals, and run and sign tests on the residuals. One of the growth models used (Preece & Baines, 1978) was found to be superior to the classical growth models (exponential, monomolecular, logistic, Gompertz, von Bertalanffy) and gave an adequate fit to all longitudinal measures taken from the embryonic body and embryonic mass. However, measurements taken from the head could not be fitted by growth models but were adequately fitted by weighted least squares cubic splines. Data for the stage of development were best fitted by a sum of 2 exponentials with a transition point. Comparison of the maximum growth rates and parameter values, indicated that the growth data at 30 degrees C could be scaled to 33 degrees C to multiplying the time by a scaling factor of 1.2. This is equivalent to a Q10 of about 1.86 or, after solving the Arrhenius equation, an E++ of 46.9 kJmol-1. This may be interpreted as indicating a common rate-limiting step in development at the 2 temperatures.

Alligators and Crocodiles↗
PubMed1993

Observations on the commercial production of ostrich (Struthio camelus) in the United Kingdom: rearing of chicks.

Two sets of ostrich eggs (60 and 120 eggs) were imported into the United Kingdom under class 1 quarantine restrictions. The eggs were incubated and observations were made on the growth, survival and sex ratio of the chicks hatched. The chicks decreased in weight for five days after hatching before they began a sustained period of exponential growth. They reached a liveweight of 4 kg five weeks after hatching. Female chicks grew significantly faster than male chicks. The survival rates of the chicks to three months of age were 66.7 per cent and 78.3 per cent, respectively, for the two sets of eggs, and mortality restricted mainly to the first four weeks of rearing. All the birds which died showed poor rates of growth before they died. The sex ratio of both groups was skewed 2:1 towards males.

Animal Husbandry↗
PubMed1993

Observations on the commercial production of ostrich (Struthio camelus) in the United Kingdom: incubation.

Two sets of ostrich eggs (60 and 120 eggs) were imported into the United Kingdom under class 1 quarantine restrictions. Single stage incubation was carried out and the eggs were weighed before and during incubation in order to control weight loss. In the two hatches the weight losses during the incubation of viable eggs were 13.4 per cent and 11.4 per cent, respectively. The development of the eggs was followed by candling and although only dark shadows were observed a pattern could be recognised. For the first set of eggs the average length of incubation was 45.9 days with an interval of 12.7 hours between pipping and hatching. The second set of eggs was incubated at higher temperatures than the first and the main incubation period was 43.3 days with hatching 19.2 hours after pipping. Larger eggs took longer to hatch.

Animals↗
PubMed1990

Size-dependent pigmentation-pattern formation in embryos of Alligator mississippiensis: time of initiation of pattern generation mechanism.

The pigmentation pattern of Alligator mississippiensis was examined. The number of white stripes on the dorsal side of embryos (stages 21-28) and hatchlings from eggs incubated at 30 degrees C (100% females) and 33 degrees C (100% males) was recorded. Total length, nape-rump length and tail length were recorded for each embryo and hatchling. The number of white stripes was affected by incubation temperature but not sex; hatchlings incubated at 33 degrees C had two more white stripes than those at 30 degrees C, despite being the same length. Five female hatchlings produced at 33 degrees C by manipulation of the temperature, had the same number of stripes as males that developed under the same incubation temperatures. The appearance of the pigmentation was accelerated in embryos incubated at 33 degrees C, occurring eight days earlier than at 30 degrees C. At the time just before the first signs of pigment deposition, embryos from 33 degrees C were longer than those at 30 degrees C. If the stripe formation is size dependent this explains why hatchlings at 33 degrees C have more stripes than hatchlings from 30 degrees C. The mechanism that produces the stripe patterns is unknown. We describe key elements a pattern formation mechanism must possess to produce such stripes and suggest a possible mechanism, based on cell movement driven by chemotaxis. We apply the mathematical model to dorsal patterning on A. mississippiensis. We show how length at pattern formation is the prime factor in determining stripe number and how the pattern can be formed in the observed anterior-posterior sequence. We present numerical simulations and show that the qualitative behaviour is consistent with the experimental results.

Alligators and Crocodiles↗
PubMed1989

Characteristics of unturned eggs: critical period, retarded embryonic growth and poor albumen utilisation.

1. The physiological effects of egg turning during incubation are described. 2. There was a critical period for turning, from days 3 to 7 of incubation, which affected hatchability, embryo growth and utilisation of extra-embryonic fluids. 3. Failure to turn eggs retarded formation of allantoic and amniotic fluids, restricted alumen uptake and retarded growth of the embryo, but only after day 12 of incubation.

Albumins↗
PubMed1989

Importance of sub-embryonic fluid and albumen in the embryo's response to turning of the egg during incubation.

1. The effects of removal of sub-embryonic fluid and albumen on the development of the fowl embryo were investigated. 2. A deficiency of sub-embryonic fluid on day 7 of incubation resulted in a reduction in the volume of the yolk sac and of allantoic fluid, and a reduction in the mass of the embryo later in incubation. 3. A deficiency of albumen on day 3 of incubation led to a reduction in allantoic fluid and embryo mass after day 12 incubation. 4. The results suggest that the physiology of embryos in unturned eggs is better modelled by eggs deprived of albumen than by eggs deprived of sub-embryonic fluid.

Albumins↗
PubMed1988

Environmental regulation of sex determination in reptiles.

The various patterns of environmental sex determination in squamates, chelonians and crocodilians are described. High temperatures produce males in lizards and crocodiles but females in chelonians. Original experiments on the effects of incubation at 30 degrees C (100% females) or 33 degrees C (100% males) on development in Alligator mississippiensis are described. These include an investigation of the effect of exposing embryos briefly to a different incubation temperature on the sex ratio at hatching, and a study of the effects of 30 degrees C and 33 degrees C on growth and development of alligator embryos and gonads. A 7-day pulse of one temperature on the background of another was insufficient to alter the sex ratio dramatically. Incubation at 33 degrees C increased the rate of growth and development of alligator embryos. In particular, differentiation of the gonad at 33 degrees C was enhanced compared with 30 degrees C. A hypothesis is developed to explain the mechanism of temperature-dependent sex determination (TSD) in crocodilians. The processes of primary sex differentiation are considered to involve exposure to a dose of some male-determining factor during a specific quantum of developmental time during early incubation. The gene that encodes for the male-determining factor is considered to have an optimum temperature (33 degrees C). Any change in the temperature affects the expression of this gene and affects the dose or quantum embryos are exposed to. In these cases there is production of females by default. The phylogenetic implications of TSD for crocodilians, and reptiles in particular, are related to the life history of the animal from conception to sexual maturity. Those animals that develop under optimal conditions grow fastest and largest and become male. A general association between the size of an animal and its sex is proposed for several types of vertebrate.

Animals↗
PubMed1987

Failure to turn eggs during incubation: effects on embryo weight, development of the chorioallantois and absorption of albumen.

Turning eggs during incubation is essential for good hatchability. In the present paper additional effects on the development of the chorioallantois, absorption of albumen and growth of the embryo are recorded. The ability of an unturned egg to hatch was not affected by egg weight, egg shell porosity or water loss during incubation. The ability of the chorioallantois to spread around the inner surface of the inner shell membrane and the degree of absorption of the residual albumen affected the growth of the embryo and its ability to hatch. Unturned eggs hatched later than eggs which were turned throughout incubation.

Allantois↗
PubMed1987

Physical influences on embryo development.

There is a critical period between 3 and 7 days of incubation when the absence of turning in eggs of the domestic fowl leads to increased mortality and decreased embryo growth. This critical period coincides with the time of subembryonic fluid formation, and it is suggested that the absence of turning leads to the presence of unstirred layer effects in fluid secretion. This fluid deficiency persists throughout the subsequent development of the embryo. Experiments on shell-less culture systems support this interpretation in preference to other explanations of embryo death in unturned eggs, which usually refer to chorion adhesion to shell membranes.

Animals↗
PubMedDate not supplied

Factors affecting the rate of growth of ostrich (Struthio camelus) chicks in captivity.

A set of 120 ostrich eggs was imported into the United Kingdom under class 1 quarantine restrictions. The chicks hatched were initially reared in mixed size groups and weighed daily to monitor their health. Ten days after hatching the chicks were separated into four groups, based on their weight, which were kept under identical conditions, fed ad libitum and weighed daily. At the end of the 35 day quarantine period the growth rates of the chicks were correlated with their weight on day 10: the heaviest chicks remained the heaviest. In addition, the degree to which the chicks lost weight and the period for which they did so was also related to their weight on day 10. However, the smallest chicks on day 10 grew more quickly than the largest chicks. Chicks which had been helped to pip and hatch showed poor survival rates and low rates of growth. The growth rate of the ostriches appeared to be influenced by environmental factors.

Animal Husbandry↗