Skeletal Growth Rate

A significant aspect of skeletal growth in corals is the existence of an internal calendar where daily, seasonal, and annual records are kept on file in the form of individual or series of bands. The band thicknesses within a species are environmentally controlled. The number of bands per year in fossil corals has been used in studies on the Earth-Moon system, i.e. effect of tidal friction on number of days per year336.  

Microscopic growth increments 1 to 100 microns thick have been recorded from mollusc shells327. These were explained as daily deposits. However, a note of caution should be sounded in view of the findings that in some shells tidal growth increments are indicated and that the average duration of an increment is 24 hours and 50 minutes (circalunadian rhythm)337.  

In a related experiments, shallow and deep water forms were compared327. In deep water specimens increments had a uniform thickness, without sharp boundaries and no apparent seasonal or tidal indications. In summary microgrowth patterns reflect environmental changes of many sorts. The ultimate reason behind this phenomenon can be explained on physiological grounds as a result of the utilisation of calcium in energy transfer and muscle activities. Namely at times of stress these activities have higher priorities than calcification. 

Banding is most intense in the early stage annual rings and becomes less pronounced as the fish grows older. 

Sodium or one of the proposed trace minerals would act in the capacity of a growth inhibitor for aragonite. A new increment of CaC03 will only form following the deposition of an organic template. 

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Duineveld, G.C.A. and Jenness, M.I. (1984). Differences in growth rates of the sea urchin Echinocardium cordatum as estimated by the parameter to of the von Bertalanffy equation applied to skeletal rings. Marine Ecology Progress. Series, 19, 65-72. 

Q3 The thyroid hormones thyroxine and triiodothyronine have many metabolic effects. In adults they increase metabolic rate, oxygen and calorie consumption, stimulate carbohydrate metabolism and turnover of protein, deplete fat stores and increase catabolism of free fatty acids. Thyroid hormones stimulate heart rate and force and increase pulmonary ventilation, gastrointestinal motility and central nervous system (CNS) activity. Actions on the heart can result in an increased incidence of dysrhythmias. Thyroid hormones are critical for the normal growth and development of the infant, particularly in respect of skeletal growth and maturation of the CNS. 

Lloyd RD. 1990. Does the growth rate of a radionuclide-induced osteosarcoma depend of the skeletal dose rate during the growth period Health Phys 58(l) 73-76. 

Alexander CJ (1976) Effect of growth rate on the strength of the growth plate shaft junction. Skeletal Radiol 1 67-76... 

Rate of length gain Difficult to measure accurately, deficits less likely unless weight is also compromised Provides important additional information about linear/skeletal growth and proportionality... 

These conflicts of opinion are now regarded as due largely to the differences in species effect, which have led to ambiguous or contradictory results. The growth of all monocellular organisms depends on the elaboration of cyto-skeletal compounds, and growth rate can be increased when some at least of these are provided by the environment. 

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