146
The Migrant Biota
catches from depths of 15-50 m along the Egyptian and Sinai Coast (Gulf ofTina)
(Gorgy, 1966). For all these species of portunid crabs it is difficult to indicate a
competing local species which has been displaced. None of the local portunids
was frequent enough to be compared with the wealth of the three species of
newcomers.
The success of the leucosid crab Myrafugax reported from Jaffa as early as
1930 cannot be regarded as a competitive displacing of a closely allied local species.
In the Rubin profile (Gilat, 1964) it appears as a dominant species besides Charybdis longicollis, on the same type of bottoms between 35-50 m (Fig.42). It seems
however that Myra fugax is still frequent at depths over 100 m, probably the
deepest going Lessepsian migrant, encountered also on bottoms of clean mud.
There are two species of local leucosid crabs in the Eastern Mediterranean.,
Ebalia granulosa and Ilia nucleus, but they are not known to be frequent in any of
the investigated stations. Another Indo-Pacific leucosid crab, Leucosia signata,
has also appeared recently in the Levant.
There are few data about the colonizing success of the Lessepsian migrants
among the level bottom molluscs. According to Gilat (1969) the bivalve Paphia
undulata is a fairly characteristic species of mixed bottoms between 10-35 m. It
does not appear on shallower clean-sand bottoms and not deeper than some 35 m.
A curious case of sudden massive appearance is that of the gastropod Cerithium kochi. This Red Sea species, not reported in the Suez Canal, did not appear
in Gilat's collections from Haifa Bay (1953-1956) or from Rubin (1960-1962).
First dredged in 1963 in the Bay, it has since appeared rapidly as one of the
dominant species of the level bottoms of the Israel coast -between 20-60 m depth.
In Gilat's 1968-1969 profiles it was already one of the mass organisms. It is very
difficult to assume that this sudden explosion of Cerithium populations, maintained at about the same numerical levels, has occurred at the expense of some
other species. There is to our knowledge no species of gastropods which has such
huge biomasses on the inshore level bottoms of Israel.!
It is interesting to analyze the qualitative importance of the Lessepsian migrants among the general species diversity which characterizes the different
depths ofthe EI Arish profile (Gilat, 1969).
Between
5-8 fathoms 1 Lessepsian out of 9 frequent species
Between
10 fathoms 5 Lessepsians out of 10 frequent species
Between
12 fathoms 7 Lessepsians out of 12 frequent species
Between 20-25 fathoms 3 Lessepsians out of 18 frequent species
Between 30-40 fathoms 1 Lessepsian out of 19 frequent species
Between 50-100 fathoms 2 Lessepsians out of 30 frequent species
1 Note added in proof: Recently, M. Tom in a thesis "The Benthic Fauna Association of Haifa
Bay" (Tel-Aviv University, October 1976), compared the benthic diversity of sampIes collected
in 1974-75 with those collected there by Gottlieb-Gilat in 1953-56. Four Indo-Pacific species
have been found as new and numerous members ofthe benthic communities ofHaifa Bay: the
crab Charybdis longicollis was frequent on biogenie rocks and the gastropods Cerithium kochi
and I sanda cf. holdsworthiana on soft bottoms between 25-30 m. The brittle star Ophiactis parva
(Mortensen), a new addition to the list of the Lessepsian migrants, has been found by Tom as
a frequent inhabitant of the Caulerpa scalpellijormis meadows and on the arms of Antedon
mediterranea around 40-50 m depth.
The Migrant Biota
catches from depths of 15-50 m along the Egyptian and Sinai Coast (Gulf ofTina)
(Gorgy, 1966). For all these species of portunid crabs it is difficult to indicate a
competing local species which has been displaced. None of the local portunids
was frequent enough to be compared with the wealth of the three species of
newcomers.
The success of the leucosid crab Myrafugax reported from Jaffa as early as
1930 cannot be regarded as a competitive displacing of a closely allied local species.
In the Rubin profile (Gilat, 1964) it appears as a dominant species besides Charybdis longicollis, on the same type of bottoms between 35-50 m (Fig.42). It seems
however that Myra fugax is still frequent at depths over 100 m, probably the
deepest going Lessepsian migrant, encountered also on bottoms of clean mud.
There are two species of local leucosid crabs in the Eastern Mediterranean.,
Ebalia granulosa and Ilia nucleus, but they are not known to be frequent in any of
the investigated stations. Another Indo-Pacific leucosid crab, Leucosia signata,
has also appeared recently in the Levant.
There are few data about the colonizing success of the Lessepsian migrants
among the level bottom molluscs. According to Gilat (1969) the bivalve Paphia
undulata is a fairly characteristic species of mixed bottoms between 10-35 m. It
does not appear on shallower clean-sand bottoms and not deeper than some 35 m.
A curious case of sudden massive appearance is that of the gastropod Cerithium kochi. This Red Sea species, not reported in the Suez Canal, did not appear
in Gilat's collections from Haifa Bay (1953-1956) or from Rubin (1960-1962).
First dredged in 1963 in the Bay, it has since appeared rapidly as one of the
dominant species of the level bottoms of the Israel coast -between 20-60 m depth.
In Gilat's 1968-1969 profiles it was already one of the mass organisms. It is very
difficult to assume that this sudden explosion of Cerithium populations, maintained at about the same numerical levels, has occurred at the expense of some
other species. There is to our knowledge no species of gastropods which has such
huge biomasses on the inshore level bottoms of Israel.!
It is interesting to analyze the qualitative importance of the Lessepsian migrants among the general species diversity which characterizes the different
depths ofthe EI Arish profile (Gilat, 1969).
Between
5-8 fathoms 1 Lessepsian out of 9 frequent species
Between
10 fathoms 5 Lessepsians out of 10 frequent species
Between
12 fathoms 7 Lessepsians out of 12 frequent species
Between 20-25 fathoms 3 Lessepsians out of 18 frequent species
Between 30-40 fathoms 1 Lessepsian out of 19 frequent species
Between 50-100 fathoms 2 Lessepsians out of 30 frequent species
1 Note added in proof: Recently, M. Tom in a thesis "The Benthic Fauna Association of Haifa
Bay" (Tel-Aviv University, October 1976), compared the benthic diversity of sampIes collected
in 1974-75 with those collected there by Gottlieb-Gilat in 1953-56. Four Indo-Pacific species
have been found as new and numerous members ofthe benthic communities ofHaifa Bay: the
crab Charybdis longicollis was frequent on biogenie rocks and the gastropods Cerithium kochi
and I sanda cf. holdsworthiana on soft bottoms between 25-30 m. The brittle star Ophiactis parva
(Mortensen), a new addition to the list of the Lessepsian migrants, has been found by Tom as
a frequent inhabitant of the Caulerpa scalpellijormis meadows and on the arms of Antedon
mediterranea around 40-50 m depth.