but also a very important food source for benthic organisms [37, 38], due to large
seasonal abundances, the above-mentioned diversity and the relationships they
evolved with given species [39]. For example, the Posidonia oceanica environment
contains several species of diatoms [40] and some of them are selectively present on
the plant leaves, if not exclusive, due to a long evolutionary history [41]. The genus
Cocconeis (Fig. 3), in particular, contains some species (e.g., Cocconeis scutellum
var. posidoniae and C. scutellum var. neothumensis) that were identified in very
specific areas and in presence of the plant substratum [40]. Cocconeis spp. diatoms
are well adapted to the life on P. oceanica leaves because they are generally
sciaphylic [42], very adhesive and slow growing, able to seasonally cover almost
the entire surface of plant leaves. They represent an excellent trophic resource for
various micro-grazers [43], due to a complete spectrum of fatty acids specifically
produced, and low generic toxicity [29].
5
The Life Cycle of Hippolyte inermis
The peculiar case of Hippolyte inermis Leach, 1815 is emblematic in this view [44].
H. inermis lives in shallow waters of the Mediterranean and along the Atlantic coast
of Spain [45]. It forms stable populations in seagrass meadows [46], mainly in
Posidonia oceanica and Cymodocea nodosa [47]. Most individuals exhibit mimic
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Time [min]
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Fig. 2 An HTML profile of Cocconeis scutellum parva lipophilic fraction. The active compound
responsible for the apoptotic destruction of the A.G. of Hippolyte inermis is considered to be in the
area indicated by a red ellipse
7 Co-evolution of the Shrimp Hippolyte inermis and the Diatoms Cocconeis. . .
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