TY - JOUR
T1 - Skeletal calcification patterns in the sea urchin Tripneustes gratilla elatensis (Echinoidea: Regularia) - I. Basic patterns
AU - Dafni, J.
AU - Erez, J.
PY - 1987/7
Y1 - 1987/7
N2 - A comprehensive study on skeletal calcification in the regular echinoid Tripneustes gratilla elatensis was carried out between 1979 and 1981 in the northern Gulf of Eilat (Red Sea), employing size measurement, allometry and radiotracer techniques. Uptake rates of the isotope 45Ca were used to estimate the calcification rate of whole tests. Calcification rates of the different skeletal parts and the 45Ca uptake along the sutural margins of individual plates were also measured. Whole-test calcification rates for juvenile individuals, 11 to 13 mm in diameter, relative to their skeletal Ca dry weight, calculated using the allometric relationship between skeletal dry weight and diameter, were 1.5 to 1.8% d-1 for 4 to 8 h of incubation, while calcification rates obtained from periodical size measurements and allometrical constants amounted to 2.75% d-1. The apparent discrepancy between these results is explained partly by the short duration of the incubations, during which the internal calcium pools, apparently in the coelom, were not fully saturated with the radioactive tracer. This discrepancy decreased when longer radioactive incubations were used, or when a post-incubational deposition of 45Ca from these pools was allowed. The size of these pools is roughly 10 μmol Ca per 13-mm individual, and it resides probably in the coelom where Ca concentration is ∼ 3 times higher than in seawater. The calcification rates given as percentage of skeleton added per day, both for the radioactive and allometric methods, decreased with the urchins' size. The calcification patterns of various components of the skeleton generally fitted their allometrical trends - a relative decrease in the size of the spines, apical plates and lantern. The teeth calcify rapidly to compensate for the constant erosion of their tips. Calcification per plate decreased exponentially from the apex to the peristome. Plate-edge calcification patterns of both interambulacral and ambulacral plates fitted patterns derived from size increment measurements, using natural growth-lines. Typically, most plates grow more horizontally (latitudinally) than vertically. It is suggested that the vertical vs horizontal calcification ratio (v/h) determines the individual plate growth and affects the whole test morphology.
AB - A comprehensive study on skeletal calcification in the regular echinoid Tripneustes gratilla elatensis was carried out between 1979 and 1981 in the northern Gulf of Eilat (Red Sea), employing size measurement, allometry and radiotracer techniques. Uptake rates of the isotope 45Ca were used to estimate the calcification rate of whole tests. Calcification rates of the different skeletal parts and the 45Ca uptake along the sutural margins of individual plates were also measured. Whole-test calcification rates for juvenile individuals, 11 to 13 mm in diameter, relative to their skeletal Ca dry weight, calculated using the allometric relationship between skeletal dry weight and diameter, were 1.5 to 1.8% d-1 for 4 to 8 h of incubation, while calcification rates obtained from periodical size measurements and allometrical constants amounted to 2.75% d-1. The apparent discrepancy between these results is explained partly by the short duration of the incubations, during which the internal calcium pools, apparently in the coelom, were not fully saturated with the radioactive tracer. This discrepancy decreased when longer radioactive incubations were used, or when a post-incubational deposition of 45Ca from these pools was allowed. The size of these pools is roughly 10 μmol Ca per 13-mm individual, and it resides probably in the coelom where Ca concentration is ∼ 3 times higher than in seawater. The calcification rates given as percentage of skeleton added per day, both for the radioactive and allometric methods, decreased with the urchins' size. The calcification patterns of various components of the skeleton generally fitted their allometrical trends - a relative decrease in the size of the spines, apical plates and lantern. The teeth calcify rapidly to compensate for the constant erosion of their tips. Calcification per plate decreased exponentially from the apex to the peristome. Plate-edge calcification patterns of both interambulacral and ambulacral plates fitted patterns derived from size increment measurements, using natural growth-lines. Typically, most plates grow more horizontally (latitudinally) than vertically. It is suggested that the vertical vs horizontal calcification ratio (v/h) determines the individual plate growth and affects the whole test morphology.
UR - http://www.scopus.com/inward/record.url?scp=2342510099&partnerID=8YFLogxK
U2 - 10.1007/BF00409015
DO - 10.1007/BF00409015
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AN - SCOPUS:2342510099
SN - 0025-3162
VL - 95
SP - 275
EP - 287
JO - Marine Biology
JF - Marine Biology
IS - 2
ER -