Over the period from June 2002 to June 2003, we examined the relationship of seasonal changes in the mass of the gonad and somatic tissues to environmental factors for four size groups of the zebra ark shell Arca zebra at Chacopata, in northeastern Venezuela. The gonads of A. zebra began to increase in size when individuals attained 18–20 mm in shell length, but maximum gonad mass relative to somatic mass was only attained at 55–60 mm in length. Large individuals (>50 mm) showed a distinct annual reproductive cycle with a marked increase in gonad mass from July to late September 2002, coinciding with the increase in temperatures related to stratification of the water column. A decrease in gonad size occurred during October 2002 through January 2003 and coincided with a temperature decline related to renewed upwelling. The mass of somatic tissues was highest between late August to late December 2002, coinciding with the reproductive period and elevated temperatures. Other environmental factors showed little seasonal variation, although chlorophyll a concentration was lowest during the major period of increase in the gonad and somatic tissues (July to late September 2002), suggesting that the animals were not limited by the abundance of phytoplankton food. A. zebra seemed to be well adapted to the high loads of inorganic seston found in the Chacopata region.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 25 • No. 3