Comparative mating success of smaller male-phase and larger male-role euhermaphrodite-phase shrimp, <Emphasis Type="Italic">Lysmata wurdemanni</Emphasis> (Caridea: Hippolytidae) |
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Authors: | Email author" target="_blank">Dong?ZhangEmail author Junda?Lin |
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Institution: | (1) Vero Beach Marine Laboratory, Florida Institute of Technology, 805 East 46th Place, Vero Beach, FL 32963, USA;(2) Department of Biological Sciences, Florida Institute of Technology, , FL, USA |
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Abstract: | The protandric simultaneous hermaphrodite shrimp Lysmata wurdemanni (Gibbes 1850) has a pure searching mating system, i.e., males are continually searching for receptive females and copulation
is brief. To examine whether size-based advantage in male–male competition occurs and whether the mating ability of male-phase
(M) shrimp equals that of euhermaphrodite-phase shrimp serving as males (Em), mating performance, including mating frequency
and precopulatory behavior, of M and Em shrimp was compared using two M:Em ratios. Two experiments were carried out from March
2004 to August 2004 at Florida Institute of Technology’s Vero Beach Marine Laboratory using laboratory-cultured shrimp that
originated from Port Aransas, TX, USA. In the two experiments, one parturial euhermaphrodite-phase shrimp acting as a female
(Ef) was maintained with one M and two Em shrimp (one with and one without an egg mass), and two M and two Em shrimp, respectively.
The M shrimp used were always smaller than the Em shrimp. Experiment 1 showed that there was no significant difference in
mating ability between Em with and without egg mass. In both experiments, the M shrimp gained mating partners more frequently
than the Em shrimp did. In the experiment with two M and two Em shrimp, mating frequencies of the small M and large M shrimp
were similar. Precopulatory behaviors of the M shrimp were more active than those of the Em shrimp. Mating between the small
M and larger Ef shrimp was sometimes successful even when the size difference was 20.0 mm total length (TL). Mating between
a larger M shrimp and smaller Ef shrimp sometimes failed when the size difference was only 13.0 mm TL. Mating frequency of
M shrimp over that of Em shrimp with Ef shrimp increased significantly with increasing density and operational sex ratio.
The advantage of M over Em shrimp in obtaining mating partners is probably a result of sexual selection and adaptation, and
may partially explain the observed delayed sex change in some L. wurdemanni, i.e., some male-phase shrimp grow very large and never become hermaphrodites. |
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