therefore, the species so-called exotic in the Mediterranean is likely to be native and
to have been misidentified.
The spectacular West African gastropod Marginella glabella, reported in the
fishing harbour of Málaga by Luque et al. (2012), was speculated to have been
imported when the fishing fleet routinely operated on Saharan fishing grounds. The
species persisted in the fishing harbour of Málaga, without spreading, at least for
some years.
Another introduced species that comes from West Africa is the crab Cryptosoma
cristatum, which was captured in Malaga in 1993 (García Raso 1993, as Cycloes
cristata). However, the origin of the presence in Alboran of some African crustacean
species is not clear, as they could be either introductions or the result of a natural
advance. For example, Synalpheus africanus, which may come from the Atlantic or
Mediterranean African coasts (García Raso 1984b), is a very coastal species that has
been able to enter with ballast water from ships or transported (as larvae) by currents.
Acantharctus posteli (¼ Scyllarus posteli) was first found in Europe in Cádiz and is
most likely the result of an introduction (Pozuelo et al. 1976; García Raso 1982) but
its presence in Alboran (Málaga) is the result of a natural progression. Another case
would be the crab Brachynotus atlanticus, which was first cited for Europe in
Alboran (Málaga) (García Raso 1984a) but, in European waters, only has wellestablished populations in the Gulf of Cádiz (García Raso 1985; unpublished data),
so its presence in the Alboran Sea would be a case similar to that of Acantharctus
posteli. Another more recent case is that of the pea crab Afropinnotheres monodi,
which lives inside the mussel (Mytilus galloprovincialis), was first caught in the Bay
of Cádiz and shows a progress towards the Mediterranean coasts (Pérez-Miguel et al.
2017).
In any case, the scarcity of studies on the coast of Mauritania and Morocco
(especially in shallow areas) means that the actual distribution of many African
species is not well known. This makes it uncertain whether the presence of a species
in the South of Spain is due to human introductions or not. As examples, we may
mention the prawn Processa macrodactyla (García Raso and Salas Casanova 1985),
or more recently the hermit crab Pagurus mbizi (García Raso et al. 2014), whose
northernmost known location before its capture in Alboran was the coast of Senegal.
Since the publication of the MAGRAMA checklist, several additions have been
made to the alien fauna. The Alboran Sea is far away from the Suez Canal and, thus,
more difficult to reach by the Lessepsian migrants that entered the Mediterranean
through this waterway. Still, the record of a Lessepsian migrant Bursatella leachii, a
sea-hare, in the Alboran sea was made very recently (March 2018, J.D. Moreno,
pers. comm.) at Marina del Este (Granada). Another recent addition is the sponge
Paraleucilla magna, reported as spreading fast inside the Mediterranean including
the Alboran Sea (Guardiola et al. 2016). In relation to decapod crustaceans, the only
strictly invasive alien species is Percnon gibbesi, which entered the Suez Canal into
the Mediterranean in 1999 (Katsanevakis et al. 2010; IUCN–MedPAN 2012) and
whose most recent and western location is in the Alboran Sea, in 2017 on the coast of
Almeria (near the border with the province of Granada). Nonetheless, the Alboran
Sea seems to resist invasions better than other marine areas of Europe. Azzurro et al.
11 Biogeographical and Macroecological Context of the Alboran Sea
449
to have been misidentified.
The spectacular West African gastropod Marginella glabella, reported in the
fishing harbour of Málaga by Luque et al. (2012), was speculated to have been
imported when the fishing fleet routinely operated on Saharan fishing grounds. The
species persisted in the fishing harbour of Málaga, without spreading, at least for
some years.
Another introduced species that comes from West Africa is the crab Cryptosoma
cristatum, which was captured in Malaga in 1993 (García Raso 1993, as Cycloes
cristata). However, the origin of the presence in Alboran of some African crustacean
species is not clear, as they could be either introductions or the result of a natural
advance. For example, Synalpheus africanus, which may come from the Atlantic or
Mediterranean African coasts (García Raso 1984b), is a very coastal species that has
been able to enter with ballast water from ships or transported (as larvae) by currents.
Acantharctus posteli (¼ Scyllarus posteli) was first found in Europe in Cádiz and is
most likely the result of an introduction (Pozuelo et al. 1976; García Raso 1982) but
its presence in Alboran (Málaga) is the result of a natural progression. Another case
would be the crab Brachynotus atlanticus, which was first cited for Europe in
Alboran (Málaga) (García Raso 1984a) but, in European waters, only has wellestablished populations in the Gulf of Cádiz (García Raso 1985; unpublished data),
so its presence in the Alboran Sea would be a case similar to that of Acantharctus
posteli. Another more recent case is that of the pea crab Afropinnotheres monodi,
which lives inside the mussel (Mytilus galloprovincialis), was first caught in the Bay
of Cádiz and shows a progress towards the Mediterranean coasts (Pérez-Miguel et al.
2017).
In any case, the scarcity of studies on the coast of Mauritania and Morocco
(especially in shallow areas) means that the actual distribution of many African
species is not well known. This makes it uncertain whether the presence of a species
in the South of Spain is due to human introductions or not. As examples, we may
mention the prawn Processa macrodactyla (García Raso and Salas Casanova 1985),
or more recently the hermit crab Pagurus mbizi (García Raso et al. 2014), whose
northernmost known location before its capture in Alboran was the coast of Senegal.
Since the publication of the MAGRAMA checklist, several additions have been
made to the alien fauna. The Alboran Sea is far away from the Suez Canal and, thus,
more difficult to reach by the Lessepsian migrants that entered the Mediterranean
through this waterway. Still, the record of a Lessepsian migrant Bursatella leachii, a
sea-hare, in the Alboran sea was made very recently (March 2018, J.D. Moreno,
pers. comm.) at Marina del Este (Granada). Another recent addition is the sponge
Paraleucilla magna, reported as spreading fast inside the Mediterranean including
the Alboran Sea (Guardiola et al. 2016). In relation to decapod crustaceans, the only
strictly invasive alien species is Percnon gibbesi, which entered the Suez Canal into
the Mediterranean in 1999 (Katsanevakis et al. 2010; IUCN–MedPAN 2012) and
whose most recent and western location is in the Alboran Sea, in 2017 on the coast of
Almeria (near the border with the province of Granada). Nonetheless, the Alboran
Sea seems to resist invasions better than other marine areas of Europe. Azzurro et al.
11 Biogeographical and Macroecological Context of the Alboran Sea
449