SEDAO 1:163-173 (2015)  -  DOI: https://doi.org/10.3354/sedao00015

ABSTRACT: Vertical distribution, sex ratio, size structure and mate encounters of Firoloida desmarestia in the southern Gulf of Mexico were analyzed during 4 seasons (in February, May, August and November). A total of 395 individuals were collected with an opening-closing net at 5 levels of the 105 m upper water column. Results indicated that the species reproduces throughout the year, with a reproductive peak in May and a low reproductive period from August to February. Length measurements indicated that females (as long as 30 mm) are larger than males (18 mm). Estimations of a ‘spatial overlap’ index showed a high overlap degree between sexes, suggesting that patterns in their vertical distribution are not a reproductive barrier. Sex ratio (F:M) at birth seemed to be 1:1, but during most of the year the adult sex ratio was dominated by females. We propose that larger dimensions and faster swimming speeds of females provide competitive advantages over males in searching for food and avoiding predators. Simulations of mate encounters indicated that values during the low reproductive season were low under turbulent and non-turbulent conditions (<4.9 males d^-1 female^-1), but enough to fertilize a high percentage of females. During the high reproductive season, encounters were as high as 17.2 males d^-1 female^-1 because the high density of adult population and the influence of wind-induced turbulence. We suggest that some biological features of females (seminal receptacle and exocrine gland) compensate for the low encounter rates. A conceptual model for the population dynamics of F. desmarestia is proposed.

KEY WORDS: Sex ratio · Size structure · Encounter rates · Spatial overlap · Wind-induced turbulence · Vertical distribution · Demographic model · Population dynamics

Full text in pdf format Supplementary material

Cite this article as: Lemus-Santana E, Sanvicente-Añorve L, Alatorre-Mendieta M, Flores-Coto C (2015) Population structure and mating encounter rates in a marine pelagic invertebrate, Firoloida desmarestia (Mollusca). Sex Early Dev Aquat Org 1:163-173. https://doi.org/10.3354/sedao00015 Export citation Share:    Facebook - - linkedIn