Sea urchins biometry — urchin

Various measurement on Paracentrotus lividus sea urchins providing from fishery (Brittany, France), or from a sea urchins farm in Normandy.

urchin_bio

Format

A data frame with 19 variables:

origin: A factor with two levels: "Culture", and "Fishery".
diameter1: Diameter (in mm) of the test measured at the ambitus (its widest part).
diameter2: A second diameter (in mm) measured at the ambitus, perpendicular to the first one. The idea here is to calculate the average of diameter1 and diameter2 in order to eliminate the effect of possible slight departure from a nearly circular ambitus.
height: The height of the test (in mm), measured from month to anus, thus, orthogonally to the two diameters.
buoyant_weight: Weight (in g) of the sea urchin immersed in seawater.
weight: Weight (in g) of the whole animal.
solid_parts: Weight (in g) of the animal after draining its coelomic fluid out of the test.
integuments: Weight (in g) of the sea urchin after taking out the whole content of the test (coelomic fluid, digestive tract and gonads.
dry_integuments: Dry weight (in g) of the integuments.
digestive_tract: Weight (in g) of the digestive tract, including its content.
dry_digestive_tract: Dry weight (in g) of the digestive tract and its content.
gonads: Weight (in g) of the gonads.
dry_gonads: Dry weight (in g) of the gonads.
skeleton: Weight of the skeleton (g), calculated as the sum of lantern + test + spines.
lantern: Dry weight (in g) of the lantern (the jaw and teeth of the sea urchin).
test: Dry weight (in g) of the calcareous part of the test.
spines: Dry weight (in g) of calcareous parts of the spines.
maturity: Gonads maturity index (integer), measured on a scale of 3 states: state 0 means the gonad is absent or spent, state 1 means it is growing but not mature, and state 2 means the gonad is mature. This should be treated as a circular variable, since the reproductive cycle is 0 -> 1 -> 2 -> 0 (spawning).
sex: When it is possible, the sex of the animal is determined by visual inspection of the gonads (factor with levels "F" and "M").

A stratified sample was performed to make sure all size classes (from 5 to 5 mm in test diameter) from each sub-population are equally represented in the dataset. Hence, the size or weight-classes distributions among each population cannot be studied with this dataset. However, those data are more suitable to explore allometric relationships between body measurements and/or body parts of the sea urchins over the whole size range.

For further details on the farming of these sea urchins, see here.