The Problem of the Pre-Lessepsian Migrants Through the Isthmus of Suez
33
Under such conditions only a few estuarine species would be able to survive
and advance. Some of them-like the barnacle Balanus amphitrite, or species of
the isopod genus Sphaeroma-are so widespread that it is hard to say which way
they invaded the Isthmus: from the Red Sea or from the Mediteranean. It is
interesting in this respect to quote Keller (1882) who states that: "Sphaeroma
serrata ... vielleicht nebst anderen (our italics) sich schon vor Eröffnung des heutigen Suez Kanals in den salzigen Tümpeln auf dem Isthmus vorfanden". According to Glynn (1972), there are actually three species of euryhaline isopods of this
category in the Canal: Sphaeroma serratum, S. walkeri, and Cymodoce truncata.
In some species the direction of migration is clear, as in the case of Pirenella
conica. There is also a clear-cut case of a euryhaline bivalve Cerastoderma glaucum
( = Cardium edule) which came from the Mediterranean, and, before the cutting
of the Canal, succeeded in spreading as far as the northernmost end of the Gulf of
Suez (see W. Steinitz, 1929).
In two previous papers (Por, 1971 a, b) I proposed the term "Isthmus Fauna"
for this particular euryhaline fauna, the migrational movements of which might
have preceded the Lessepsian canal.
Riemann and Rachor (1972, p.185) have recently added some nematode speeies to the list of the Isthmus fauna. They write: "Diese Arten können Reste einer
alten Bittersee Fauna repräsentieren, die bereits vor der Öffnung des Kanals
bestand". Por and Marcus (1972) also added several species to the presumed list of
the Isthmus fauna.
The list of the species tentatively considered to belong to the Isthmus fauna is
as follows:
Nematoda:
Polychaeta:
Copepoda:
Ostracoda:
Cirripedia:
Isopoda:
1heristusjlavensis "Gruppe" (Sensu Riemann and Rachor)
1heristus oxycerca
Oncholaimus oxyuris
Syringolaimus striatocaudatus?
Spilophorella paradoxa?
Ptycholaimellus ponticus ?
Augeneriella lagunari
Canuella perplexa
Canuellina insignis
Robertsonia salsa
Nitocra spinnipes o.rientalis
Nitocra affinis
Heterolaophonte quinquespinosa (nec Paralaophonte, Por, 1973a)
N eocyclops salinarum
Pseudodiaptomus salinus
Cyprideis torosa
Aglaiocypris sp.
Balanus amphitrite communis
Sphaeroma serratum
Sphaeroma walkeri
Cymodoce truncata
33
Under such conditions only a few estuarine species would be able to survive
and advance. Some of them-like the barnacle Balanus amphitrite, or species of
the isopod genus Sphaeroma-are so widespread that it is hard to say which way
they invaded the Isthmus: from the Red Sea or from the Mediteranean. It is
interesting in this respect to quote Keller (1882) who states that: "Sphaeroma
serrata ... vielleicht nebst anderen (our italics) sich schon vor Eröffnung des heutigen Suez Kanals in den salzigen Tümpeln auf dem Isthmus vorfanden". According to Glynn (1972), there are actually three species of euryhaline isopods of this
category in the Canal: Sphaeroma serratum, S. walkeri, and Cymodoce truncata.
In some species the direction of migration is clear, as in the case of Pirenella
conica. There is also a clear-cut case of a euryhaline bivalve Cerastoderma glaucum
( = Cardium edule) which came from the Mediterranean, and, before the cutting
of the Canal, succeeded in spreading as far as the northernmost end of the Gulf of
Suez (see W. Steinitz, 1929).
In two previous papers (Por, 1971 a, b) I proposed the term "Isthmus Fauna"
for this particular euryhaline fauna, the migrational movements of which might
have preceded the Lessepsian canal.
Riemann and Rachor (1972, p.185) have recently added some nematode speeies to the list of the Isthmus fauna. They write: "Diese Arten können Reste einer
alten Bittersee Fauna repräsentieren, die bereits vor der Öffnung des Kanals
bestand". Por and Marcus (1972) also added several species to the presumed list of
the Isthmus fauna.
The list of the species tentatively considered to belong to the Isthmus fauna is
as follows:
Nematoda:
Polychaeta:
Copepoda:
Ostracoda:
Cirripedia:
Isopoda:
1heristusjlavensis "Gruppe" (Sensu Riemann and Rachor)
1heristus oxycerca
Oncholaimus oxyuris
Syringolaimus striatocaudatus?
Spilophorella paradoxa?
Ptycholaimellus ponticus ?
Augeneriella lagunari
Canuella perplexa
Canuellina insignis
Robertsonia salsa
Nitocra spinnipes o.rientalis
Nitocra affinis
Heterolaophonte quinquespinosa (nec Paralaophonte, Por, 1973a)
N eocyclops salinarum
Pseudodiaptomus salinus
Cyprideis torosa
Aglaiocypris sp.
Balanus amphitrite communis
Sphaeroma serratum
Sphaeroma walkeri
Cymodoce truncata