Reproductive ecology of Lampsilis bracteata (Bivalvia: Unionidae)




Seagroves, Lauren

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The Texas fatmucket, Lampsilis bracteata, is a unionid mussel endemic to the Colorado and upper Guadalupe River basins of Central Texas and is one of fifteen threatened mussel species in Texas that is also a candidate for federal listing under the Endangered Species Act. A better knowledge of its reproductive ecology is needed to develop conservation and management strategies. The purpose of this study was to investigate differences in mussel host fish relationships between populations of L. bracteata and fish originating from the San Saba and Llano rivers of the Colorado Basin in Central Texas, and to monitor and compare seasonality of reproduction between the rivers. Monthly sampling events assessed sex ratios, gamete production, gravidity period, and viability of larvae (glochidia). Reproduction varied with season and between rivers. Gravid mussels were detected throughout the study period (February to September 2017), with largest proportions being gravid between February and June before peak water temperatures were reached in summer. Sex ratio in the Llano was female-biased, whereas it did not significantly differ from 1:1 in the San Saba River. Gamete production, fecundity and glochidia viability were consistently higher in the Llano River than the San Saba, where trematode flatworms (Bucephalus sp.) were found in 21% of the egg samples, but none in samples from the Llano or any sperm samples. Host fish compatibility was tested between mussels and fish collected in both rivers using a fully-crossed study design by monitoring juvenile metamorphic (transformation) success. In addition, host compatibility was also tested with Guadalupe bass and largemouth bass from a hatchery. Highest transformation rates occurred on green sunfish, largemouth bass, and Guadalupe bass (hatchery). Average transformation success was higher for some mussel-fish pairings originating from the same tributary, but individual variation was high and the differences between mussel-fish pairings of the same species but different tributaries were not statistically significant. The results of this study suggest that L. bracteata could be produced in the lab using hatchery or wild fish, but propagation efforts that are currently initiated in Texas should consider ecological differences between populations, as mussel populations may be locally adapted to host fish. Further investigations of the life-history strategies of L. bracteata and other mussels are warranted before augmentation and reintroduction efforts are initiated.



Lampsilis, Lampsilis bracteata, Gravid, Host fish, Gamete, Glochidia


Seagroves, L. A. (2017). <i>Reproductive ecology of Lampsilis bracteata (Bivalvia: Unionidae)</i> (Unpublished thesis). Texas State University, San Marcos, Texas.


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