, Volume 74, Issue 7, pp 821–834 | Cite as

Growth, reproductive traits and habitat patterns of Unio ravoisieri (Mollusca: Bivalvia) from Ichkeul Lake tributaries (Northern Tunisia)

  • Noureddine KhalloufiEmail author
  • Chrifa Aissaoui
  • Mustapha Béjaoui
Original Article


Habitat patterns, growth and reproductive traits of the freshwater mussel Unio ravoisieri were investigated for the first time in two streams (Sejenane and Elmaleh) of the Ichkeul Lake basin (northern Tunisia) over the course of a year. A very similar profile was observed for the two studied populations. The median age class dominated in the age structure, indicating good recruitment and viability. The reproductive period lasted approximately 10 months (from September to June). Females at different gametogenesis stages were found during autumn, winter and spring. Gravid females were sampled during winter and spring, and larval release occurred from early spring to early summer. The number of embryos produced per female reached 84,000 per year. In Elmaleh stream, characterized by high salinity, reproduction of the mussel took place slightly earlier than in the other habitat (Sejenane). However, the variation in reproduction traits between the two populations was not significant (p > 0.05). Similar patterns, but with a difference in the timing of the breeding season, were recorded for Spanish populations. The results highlight a reproductive plasticity of U. ravoisieri and an ability to tolerate harsh abiotic conditions. Nevertheless, salinity and temperature seem to have a stressful effect on different reproductive stages, mainly during the brooding period; negative correlation was found between condition index and the two parameters: Pearson’s r = 0.4–0.8; p < 0.05. To avoid their adverse effects, U. ravoisieri appears to be able to adjust its reproductive cycle to the wet season when these parameters are moderate.


Unio ravoisieri Habitat patterns Reproductive traits Condition index 



The authors are grateful to Manuel Lopes-Lima, Coordinator of the Red List Authority on Freshwater Bivalves Mollusk Specialist Group (IUCN/SSC), from the University of Porto (Portugal) for the scientific review of this paper, the English version, his valuable comments and advice. Thanks are also due to Dr. Rafael Araujo (Museum of Natural Sciences of Madrid) for his comments and data on the Unio ravoisieri populations from Spain. Thanks to Pr. David Reid for his helpful comments and for the English review.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

11756_2019_213_MOESM1_ESM.pdf (446 kb)
ESM 1 (PDF 445 kb)


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Copyright information

© Institute of Zoology, Slovak Academy of Sciences 2019

Authors and Affiliations

  1. 1.Faculty of Sciences of Bizerte, LR01ES14, Laboratory of Environment BiomonitoringUniversity of CarthageBizerteTunisia

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