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The most numerous species was Leptocheirus hirsutimanus (26 specimens),
followed by Ampelisca multispinosa (17 specimens) and Cheirocratus sundevalli (9
specimens). These species were quite limited to the 50-100 m depth, there bottom was
composed by detritic sediments. In the Pontine Archipelago the number of individuals
reached, on average 4.1±0.5 (total 249) and were found 3.2±0.4 (total 95) species. On
77 stations investigated, crustaceans were found in 61. The most representative species
were Cheirocratus sundevalli (19 individuals), Ampelisca multispinosa (12 individuals),
Eurydice truncata, Galathea strigosa and Upogebia typica (11 individuals each). The
most part of them were found at 50-100 m depth, where bottom was characterised by
detritical sediments. The Aeolian Archipelago displayed the lowest number of
individuals (total 144, on average 3.3±0.5) and of species (total 58, on average 2.2±0.3).
On a total of 66 stations sampled, only in 40 stations crustaceans were found. The
species most represented were Ampelisca ledoyeri (28 specimens), Cheirocratus
sundevalli (14 specimens) and Photis longicaudata (8 specimens). The highest number
of this species were found at 50-100 m depth where dominated detritic sediments. The
poverty observed in the crustaceans populations of the Aeolian Archipelago was just
observed by meiofauna (Giacobbe et al., 1997) and by mollusc assemblages (Covazzi
Harriague et al., 2002). In this area the water column is characterised by the low
concentrations of the organic material with scarse quality, so could be defined as
oligotrophic system (Povero et al., 1998).

Similarly to number of individuals and of species, diversity showed the highest
average value in the Ustica Island and the lowest in the Aolian Archipelago. While
evenness ranged, on average, between 0.89 (Ustica) and 0.96 (Pontine Archipelago), on
the whole crustacean assemblages seemed to be well structured (Fig. 3).

As we reported by mollusc assemblages (Covazzi Harriague et al., 2002),
crustacean populations have showed differences both intra and inter-archipelago. In
fact, only 6 species were common to all archipelagos and Ustica island (Tab. 1). The
dissimilarity between sites was evident in the MDS plot (Fig. 4).

The average similarity inside archipelagos was very low (16.5 %), while the
dissimilarity between archipelagos was very high and range between 72.8 % (Ustica vs
Egadi) and 90.7 % (Aeolian vs Partenopean; Tab. 3).

2,5

H' (log2)

2 J
1,5
1

0,5
0

Egadi Ustica Aeolian Pontine Partenopean

Fig. 3 - Average values of Shannon diversity and evenness.

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