On the Growth of the Loggerhead Turtle, Caretta caretta, under Rearing Conditions

The present study was carried out to resolve the growing phases of the Loggerhead Turtle, Caretta caretta (Linné), which were raised from just hatch out stage to the 4.5 years old in the Aquarium, since the knowledge on the Sea Turtle is very poor today. The carapace length, carapace width, head length, head width, shell depth and body weight were measured every month after the hatching and the data were treated by the biometrical method (Fig. 1). The result may be summarized as follows: 1. The growth rate of the carapace length and body weight from 1.5 years to 4.5 years found to follow the logistic curve of the Robertson formula (Fig. 2, 3). 2. The relationships of the age (t year) and the carapace length (L mm) and body weight (W gr) of the Turtles are able to be expressed by the following formulae. LA=1041/1+exp1.1309-0.7038t LB=972/1+exp1.0877-0.7107t WA=110000/1+exp3.543-1.331t WB=91000/1+exp3.449-1.346t 3. The growth of reared Turtles may attain 1040mm in maximum carapace length and 110kg in body weight, and attains the egg laying size in about 6-7 years. 4. The alternating point of growth rates (dLA/dt, dLB/dt, dWA/dt, dWB/dt) was calculated as 3 years in the carapace length and 4 years in the body weight. 5. The relationships between those meristic characters were able to be expressed by the formula of allmetric growth equations. (x) (y) range in mm Carapace length Carapace width y*=0.1709x1.4189 39-53 Carapace length Carapace width y**=1.0608x0.9678 70-740 Carapace length Shell depth y=0.4706x1.0081 39-245 Carapace length Head length y=0.9643x0.7787 74-740 Carapace length Head width y=1.1306x0.6821 74-740 Carapace length Body weight y=0.0004910x2.8317 39-740 Carapace width Body weight y=0.0004431x2.9147 43-740 6. An inflection point was found in the relationship between carapace length and carapace width at 57.25mm in carapace length. It suggests the ecological or physiological or physiological changes occuring in Turtles. For example, morphological changes found in the upper jaw in the pointed end at the early growth stage (Fig. 7, Plate 1). 7. At the criticl point, the proportion of body forms which were derived from the allometric growth, was able to be divide into two stages. The inherent body shape was constituted from this critical point onward. 8. The growth gradient was taken a postero anterior gradient type by the body axis. The gradient was with high values in the posterior part.