The Model ofLessepsian Migration and Other Inter-Oceanic Contacts
167
The present Panama Canal, which was also started by Ferdinand de Lesseps,
leads through a system of locks, but more important, through two big artificial
freshwater lakes-Lake Gatun and Lake Miraflores. According to Abele (1972)
Lake Gatun is the most important of the two freshwater barriers along the Canal.
The fauna ofthe Panama Canal (opened in 1913) was first investigated by Hildebrand (1939) and in recent years by Rubinoff (1968, 1970), Rubinoff and Rubinoff
(1968), and by Abele (1972). Fauna on both sides was analyzed by Powell (1971)
and Alvarmo (1974). Discussion of possible passive transport through the Canal
can be found in Menzies (1968) and Chesher (1968).
It seems that practically no species was able to cross the Isthmus of Panama
through the present Canal. There are old reports that the turtle grass 1halassia
and the tarpon M egalops atlanticus have crossed from the Atlantic into the Pacific. McCosker and Dawson (1975) add to this the pipe fish Oosthetus lineatus.
However, Voss (1972) states that the appearance of these species on the Pacific
side is sporadic and that they did not establish stable populations there. Rubinoff
and Rubinoff (1968) reported the presence of a very euryhaline Atlantic goby,
Lophogobius cyprinoides, in the Miraflores Third Lock, a brackish excavation
made in 1943 near the Pacific entrance. McCosker arid Dawson (1975) add two
more Atlantic species of fish which have established themselves in the Miraflores
lock: Lupinoblennius dispar and Hypleurochilus aequipinnis. Abele (1972) has thoroughly analyzed the decapod fauna of the Panama Canal and assumed that three
extremely euryhaline species actually crossed the Isthmus: the prawn Palaemon
pandaliformis, and two mangrove crabs, Sesarma rhizophorae and S. sulcatum. The
prawn went only as far as the Pacific entrance and the two crabs reached only the
Caribbean mouth of the Canal. Alvarifio (1974) admits the possibility of interchange between the siphonophorans in the plankton of both sides, and Powell
(1971) of that of the bryozoans. Menzies (1968) made an interesting trial and
towed a set of intertidal organisms through the Panama Canal from one of the
ships: most ofthem survived. Chesher (1968) drew attention to the possibility of
transport in ballast water of ships. Evidence indicates a clear predominance of the
movement from the Atlantic to the Pacific. However, Rubinoff and Rubinoff
(1968) reported the presence of the Pacific goby Gobiosoma nudum and McCosker
and Dawson (1975) of the Pacific blenny Omobranchus punctatus on the Atlantic
side of the Canal. In conclusion: (1) very few extremely euryhaline species or a
good swimmer like the tarpon have succeeded in crossing the Isthmus of Panama;
(2) these species did not spread into the new sea but remained confined to the
canal outlets; (3) passive transport such as fouling or in ship ballast might have
eventually occurred. These species are, however, nonspecific adventives, as for
example, the crabs Callinectes sapidus and Rithropanopeus harrisi (Abeie, 1972),
which have also reached the Eastern Mediterranean and the Black Sea, respectively, in ballast water; and (4) there is no evidence that the zoogeographical
phenomena caused by the only 60-year-old Canal are building up towards a
qualitative change.
The present-day Panama Canal is an excellent parallel to what was the classical Egyptian-Roman Canal across the Isthmus of Suez. There is, of course, quite a
different order of magnitude if we compare the sizes of the two Canals, the
number of ships which passed through it, the speed of their passage, and thus, the
167
The present Panama Canal, which was also started by Ferdinand de Lesseps,
leads through a system of locks, but more important, through two big artificial
freshwater lakes-Lake Gatun and Lake Miraflores. According to Abele (1972)
Lake Gatun is the most important of the two freshwater barriers along the Canal.
The fauna ofthe Panama Canal (opened in 1913) was first investigated by Hildebrand (1939) and in recent years by Rubinoff (1968, 1970), Rubinoff and Rubinoff
(1968), and by Abele (1972). Fauna on both sides was analyzed by Powell (1971)
and Alvarmo (1974). Discussion of possible passive transport through the Canal
can be found in Menzies (1968) and Chesher (1968).
It seems that practically no species was able to cross the Isthmus of Panama
through the present Canal. There are old reports that the turtle grass 1halassia
and the tarpon M egalops atlanticus have crossed from the Atlantic into the Pacific. McCosker and Dawson (1975) add to this the pipe fish Oosthetus lineatus.
However, Voss (1972) states that the appearance of these species on the Pacific
side is sporadic and that they did not establish stable populations there. Rubinoff
and Rubinoff (1968) reported the presence of a very euryhaline Atlantic goby,
Lophogobius cyprinoides, in the Miraflores Third Lock, a brackish excavation
made in 1943 near the Pacific entrance. McCosker arid Dawson (1975) add two
more Atlantic species of fish which have established themselves in the Miraflores
lock: Lupinoblennius dispar and Hypleurochilus aequipinnis. Abele (1972) has thoroughly analyzed the decapod fauna of the Panama Canal and assumed that three
extremely euryhaline species actually crossed the Isthmus: the prawn Palaemon
pandaliformis, and two mangrove crabs, Sesarma rhizophorae and S. sulcatum. The
prawn went only as far as the Pacific entrance and the two crabs reached only the
Caribbean mouth of the Canal. Alvarifio (1974) admits the possibility of interchange between the siphonophorans in the plankton of both sides, and Powell
(1971) of that of the bryozoans. Menzies (1968) made an interesting trial and
towed a set of intertidal organisms through the Panama Canal from one of the
ships: most ofthem survived. Chesher (1968) drew attention to the possibility of
transport in ballast water of ships. Evidence indicates a clear predominance of the
movement from the Atlantic to the Pacific. However, Rubinoff and Rubinoff
(1968) reported the presence of the Pacific goby Gobiosoma nudum and McCosker
and Dawson (1975) of the Pacific blenny Omobranchus punctatus on the Atlantic
side of the Canal. In conclusion: (1) very few extremely euryhaline species or a
good swimmer like the tarpon have succeeded in crossing the Isthmus of Panama;
(2) these species did not spread into the new sea but remained confined to the
canal outlets; (3) passive transport such as fouling or in ship ballast might have
eventually occurred. These species are, however, nonspecific adventives, as for
example, the crabs Callinectes sapidus and Rithropanopeus harrisi (Abeie, 1972),
which have also reached the Eastern Mediterranean and the Black Sea, respectively, in ballast water; and (4) there is no evidence that the zoogeographical
phenomena caused by the only 60-year-old Canal are building up towards a
qualitative change.
The present-day Panama Canal is an excellent parallel to what was the classical Egyptian-Roman Canal across the Isthmus of Suez. There is, of course, quite a
different order of magnitude if we compare the sizes of the two Canals, the
number of ships which passed through it, the speed of their passage, and thus, the