OBSERVATIONS ON THE SPAWN OF 3 SPECIES OF CONUS FROM THE GOLFO TRISTE, VENEZUELA

Volume: 27Start Page: 14End Page: 1

Gonadic cycle of Pseudechinus magellanicus (Philippi, 1857) (Echinoidea: Temnopleuridae) from Patagonia, Argentina

ZBSTRACT: Psettdecliirius tnagellanicus is one of the most abundant echinoids in Argentinean waters,r :cursing at depths from intertidal to over 150 m. It is distributed along the South American coast, from off Rioi- la Plata in the Atlantic Ocean, to Puerto Montt, in the Pacific Ocean. This species is also found in islands of7:: Antarctic Sea. It occupies a variety of habitats such as tide pools, mixed gravel and sand bottoms,'~crocystisb lades and Mytilus beds. Monthly samples were examined from September 2000 to March 2003.i?ecimens were collected by scuba diving from depths of 6-10 m in Golfo Nuevo, Puerto Mad~ynG. onad index- 2s analyzed monthly. There are two reproductive peaks and partial spawning events throughout the year. Major;-wnings were recorded in late winter (June-August) corresponding to the minimum winter water temperature.-9°C) and an increase in day length, and in summer (January- February), corresponding to the highest waters-aperature value (17-18OC) and maximum day lengths. These observations were corroborated by analysis-m'i croscopic changes in gonads and in the distribution of oocyte sizes in the ovary. Males recover faster-Y females, being able to spawn during ahnost the whole year. Resorption after spawning was observed in: -3 sexes. Oocytes bigger than 105 km have a jelly coat of 10-12 p,m which could protect them after released-I ::?e water

Reproductive cycle and gonad development of the Northern Argentinean Mesodesma mactroides (Bivalvia: Mesodesmatidae)

The reproductive cycle and gonad development of the yellow clam Mesodesma mactroides was studied over a period of 24 months (January 2005December 2006) at the Argentinean sandy beach Santa Teresita. Histological examination of gonadal tissue revealed that sex ratios did not significantly deviate from the proportion of 1:1 and no case of hermaphroditism was found. The reproductive cycle of M. mactroides followed an annual cyclicality, which was significantly correlated to monthly mean sea surface temperatures (SST). Oocytes showed highest abundance in winter, indicating a process of gonadal development and sexual maturation. The mean oocyte size decreased significantly during spring. Modal oocyte sizes decreased significantly during winter and late spring of each year, suggesting spawning events. The condition index was not useful in describing the annual reproductive cycle of M. mactroides. Ash-free, shell-free dry mass was chosen to detect the condition of the specimens, and this significantly correlated with monthly mean SST and the gametogenic cycle. Annual recruitment patterns during summerautumn indicated a 3-month-long planktonic phase of M. mactroides. The reproduction cycle and gonad development of M. mactroides showed only weak differences between data from the present study and those collected 40 years ago