Preprint volume - SIBM

Pre-print Volume - Oral presentations
Topic 2: MARINE ORGANISMS AND ECOSYSTEMS AS MODEL SYSTEMS
Clibanarius erythropus did not prey on the urchins (Tab. 1). Among 8 species of crabs
presented to young settlers of P. lividus, the two Pilumnus species and Liocarcinus
arcuatus resulted efficient predators, consuming almost all the sea urchins offered. The
two Xantho species had a low predation rate (Tab. 1). The pistol shrimp Alpheus
dentipes showed an intermediate predation rate (Tab. 1).
Tab. 1 - Species used in the predation experiments.
Specie usate negli esperimenti di predazione.
Species Predation rate Size
Mean ± SD mm n
(n /10 in 48h)
Hermit crabs
Pagurus anachoretus 0.74 ± 0.23 1.5-5.5 16
Calcinus tubularis 0.77 ± 0.24 1.5-5.5 16
Cestopagurus timidus 0.00 ± 0.00 1.2-2.2 5
Clibanarius erythropus 0.00 ± 0.00 1.3-3.3 16
Crabs
Pilumnus hirtellus 0.83 ± 0.17 3.9-12 16
Pilumnus villosissimus 0.93 ± 0.10 4.8-19.5 4
Xantho pilipes 0.13 ± 0.10 11-16.8 4
Xantho poressa 0.20 ± 0.14 10-13.4 4
Liocarcinus arcuatus 0.93 ± 0.10 3-4.5 4
Sirpus zariquieyi 0.00 ± 0.00 3-3.7 4
Acanthonyx lunulatus 0.00 ± 0.00 3-5.2 4
Macropodia rostrata 0.00 ± 0.00 5-6.5 4
Pistol shrimp
Alpheus dentipes 0.34 ± 0.36 3-8.4 16
Predators of P. lividus were abundant in EAS and almost absent in the BS, where only
one individual of A. dentipes was found (Tab. 2).
Tab.2 - ANOVA on the abundance of P. lividus predators.
ANOVA sulle abbondanze dei predatori di P. lividus.
Crabs Pistol shrimp
Source of variation df MS F MS F
State (BS vs EAS) 1 24.08 289.00** 36.75 441.00**
Site (State) 2 0.08 0.05 n.s. 0.08 0.06 n.s.
Residuals 8 1.83 1.50
Total 11
Conclusions – In the Mediterranean Sea, high densities of P. lividus may maintain
coralline barrens state determining drastic changes on ecosystem functioning.
Theoretical and empirical studies suggest that resilience of alternative community
states can be enhanced by self-perpetuating process (Knowlton, 2004). Many authors
suggest that post-settlement events, like predation, may strongly influence the
abundance of sea urchins (Jennings & Hunt, 2010 and references therein). This study
for the first time investigates predation on young settlers of P. lividus by small
invertebrates. Our predation experiments provide laboratory evidence that different
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
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