Gonad development stages and reproductive traits of Diadema mexicanum (Echinodermata: Echinoidea) from Oaxaca, Mexico

Abstract

Diadema mexicanum is a common inhabitant of the Mexican Pacific coast and a key species for coral reefs dynamics. Several reproductive traits of D. mexicanum throughout one year at La Entrega Bay, Oaxaca (15°44′N), in the Mexican tropical Pacific, were analyzed. Maturity index or microscopic maturity index “MI” was calculated. Annual ratio of males to females (1:1) was not significantly different. Five gonad development stages “GDS” (i.e. development, mature, spawning, post-spawning, nutritive) were recognized. The nutritive stage was noticeably later to post-spawning. High values of gonadosomatic index “GSI” in December 2008 and February/March 2009 did not correspond to maturity but to the nutritive stage. MI values ratified the periodicity of each GDS and spawning preparedness. MI was a better descriptor than GSI for reproductive season of D. mexicanum, and probably for all sea urchins exhibiting the nutritive stage. D. mexicanum has a single annual reproductive season (maturity/spawning) from April to October, similar to the population of Panama (9°00′N), without a second season, as proposed previously for the population of Colima, Mexico (19°10′N). Previous disparities in its reproductive season reflect differences of the environments it inhabits, rather than an effect of the latitudinal gradient in the tropical region.