TABLE 2 in Taxonomic significance of test morphology in the echinoid genera Diadema Gray, 1825 and Echinothrix Peters, 1853 (Echinodermata)

TABLE 2. — Test measurements, proportions and features for Diadema mexicanum A. Agassiz, 1863 and D. paucispinum A. Agassiz, 1863. Abbreviation: SD, standard deviation.
D. mexicanumD. paucispinumOrigin of specimens examinedGalapagos Islands, MexicoHawaii (Oahu, Maui), Fiji (Viti(Acapulco, Mazatlan, Pochutla)Levu, Taveuni)Test colourblack (brown tinge)black (red tinge in juveniles, bluetinge in adults)Test shaperounded pentagonalhemisphericalTest distinctionsambulacra slightly raised aborallyambulacra slightly raised aborallyIridophore pattern (interambulacra)blue lines (faint)faint blue linesIridophore pattern (apical system)blue ring (faint)no apical ring observedIridophore pattern (genital plate)blue arch (faint)no iridophoresMean horizontal test diameter (SD)75 mm (6.1 mm)70 mm (4.4 mm)Mean vertical test diameter (SD)40 mm (4.2 mm)40 mm (3.1 mm)Maximum horizontal test diameter observed92 mm82 mmMaximum vertical test diameter observed46 mm48 mmMarkings on test (median area ofday: no marking; night: faint whitelight brown spot marking (nightinterambulacra)spotonly)Markings on naked test (median area ofwhite spot markingnoneinterambulacra)Markings on naked test (genital plate)arch-shapednoneNumber of tubercles on genital plate0-2 small tubercles2-6 tuberclesHeight to width (at widest point) ratio of0.69:10.71:1genital plateDiameter of gonopore (% of genital plate35%30%height)Form of apical systemhemicyclichemicyclicForm of periproct (distinguishing features)small black, no ring or plateletssmall black, no ring or plateletsApical system (% of horizontal test diameter)20-25%20-28%Periproct (% of horizontal test diameter)12-16%11-15%Peristome (% of horizontal test diameter)45-50%40-45%Ambulacra % of interambulacra (at ambitus)25-30%22-26%Tubercle structureperforate and crenulateperforate and crenulateNumber of median series of tubercles on1variable (1 or 2)interambulacraRudimentary tube feet present on thenonoperistomeBuccal tube feet present5 pairs5 pairsSpines present on the buccal platesnonoNumber of specimens examined4862