Abstract
The reproductive biology of a natural population of Idotea balthica basteri (Pallas, 1772) collected from Menzel Jemil (Bizerte lagoon, Tunisia) was monthly studied from October 2009 to October 2010. Besides water temperature, salinity, turbidity, pH, and dissolved oxygen were measured. Based on the state of differentiation of individuals, the population was divided into 8 categories. Their numbers depend on the one hand to intrinsic factors imposed by the specimens and the structure of the population themselves, and to extrinsic factors due to the variability of environmental conditions on the other hand. Females were morphologically recognisable at smaller size than males. Reproductive activity, which was reflected through the presence of ovigerous females and juveniles, underwent fluctuations throughout the year, but it was continuous. Moreover, salinity, temperature, nitrates, and plant biomass have a noticeable effect on the fecundity and fertility. The Principal Component Analysis also confirmed that the richness of the water in nitrates would be favorable to fecundity and fertility of Idotea balthica basteri. However, higher phosphate concentrations, in April and May seem to have a positive effect on the sex ratio. Otherwise, the temperature would be responsible for increasing the percentage of ovigerous females.
Highlights
According to its ecological and economic importance, the Bizerte lagoon has been the subject of several investigations in the last decades, carried on its physico-chemical [1]-[4], on its flora [5] [6] and on its fauna such as mussels and clams [7], Crustaceans Copepoda [8] [9]
In the present study we focused on Idotea balthica basteri which is common on the Tunisian coasts and shows characteristics that make it easy to capture: 1) The population lives on the upper infralittoral, reducing the sampling effort in a defined area and there isn’t planktonic larval stages because the embryonic and post embryonic development occurs in the female’s marsupium until mancae stage; 2) all phases of life cycle can be sampled with the assurance that the young are issued from the same population; 3) individuals are abundant being able to support a wide range of environmental conditions
Based on the environmental factors we have obtained, we find that in January and February, the richness of the water in nitrates would be favorable to fecundity and fertility of Idotea balthica basteri
Summary
According to its ecological and economic importance, the Bizerte lagoon has been the subject of several investigations in the last decades, carried on its physico-chemical [1]-[4], on its flora [5] [6] and on its fauna such as mussels and clams [7], Crustaceans Copepoda [8] [9]. Several works which have been carried on the biology and reproductive behaviour of the genus Idotea, showed variations in the duration of the breeding season in lagoon species Idotea chelipes Pallas 1766 [12]-[14] and marine species such as Idotea granulosa [15], Idotea pelagica (Leifsson 1998), Idotea metallica [16], Idotea balthica [17]-[21]. The main objective of this work is to investigate the reproductive biology of a natural population of Idotea balthica basteri at Menzel Jemil (Bizerte lagoon) and to highlight the influence of some environmental factors on its reproduction
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