Reproductive cycle and gonad development of the Northern Argentinean <Emphasis Type="Italic">Mesodesma mactroides</Emphasis> (Bivalvia: Mesodesmatidae) |
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Authors: | Marko Herrmann José E F Alfaya Mauro L Lepore Pablo E Penchaszadeh Jürgen Laudien |
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Institution: | (1) Alfred Wegener Institute for Polar and Marine Research, P.O. Box 120161, 27515 Bremerhaven, Germany;(2) Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Av. ángel Gallardo 470, 3er piso lab. 57, C1405DJR Buenos Aires, Argentina |
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Abstract: | The reproductive cycle and gonad development of the yellow clam Mesodesma mactroides was studied over a period of 24 months (January 2005–December 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 summer–autumn 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.
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Keywords: | Yellow clam Histology Condition index Ash-free shell-free dry mass Oocyte size and abundance |
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