Reproduction and Sizes of Animals in the Suez Canal
81
2.8 Reproduction and Sizes of Animals in the Suez Canal
This chapter would have been large1y unnecessary had it been c1ear to everybody that the Suez Canal is an environment to life as every other water body and
not only a passage way, as it has been abstractly considered.
Time and time again, authors were surprised to report that they found reproductive or egg-bearing species in the Canal, on the assumption that the Canal
system operates like a hypersaline or brackish lagoon, with adult populations
either leaving for reproduction or having to be constantly reinforced by new
swept-in swarms of larvae. Such a behavior can be expected from good swimmers:
fish, penaeid shrimps, portunid crabs, or cephalopods. However, there are no
indications that a migratory "catadromous" life cyc1e actually exists in any of
these species in the Canal. The system, especially owing to the brackish areas of
Lake Timsah, may in fact offer a very wide range of salinities for those species that
need a certain salinity value in order to reproduce. Catadromous reproductive
behavior is probably present but far from being the rille.
Among fishes, Tillier (1902) reports the following species as reproducing in the
Canal: Atherinaforskalii (= Atherina pinguis), Clupea quadrimaculata, Crenidens
forskalii (= C.crenidens), Mugil seheli, M.capito? and M.saliens? No additional
nektonic fish in spawning stage has been reported since!
The nektonic decapods positively known to reproduce in the Canal are: Penaeopsis stebbingi, the larvae of which Gurney (1927 a) found in the Canal, and the
swimming crab 1halamita poissoni, which Calman (1927 a) found to be ovigerous.
From the more "sedentary" organisms of the Canal re1atively few have been
reported to reproduce there. In fact, the collections are not specially analyzed for
that; reporting of"adillt" specimens is not enough. Fishes, for example, have to be
dissected. Hippocampus hippocampus males were found with brood pouches full of
deve10ping eggs (Steinitz and Ben-Tuvia, 1972).
In molluscs the situation is similar for the bivalves; the egg-masses of Gastropoda can, however, be identified, especially by the large-sized spawns. The only
cases in which reproduction of molluscs within the Canal could be proven are
those reported by Barash and Danin (1972) in which egg masses were found, i.e. of
Murex anguliferus, another species of Murex and an egg collar of Natica sp.
The situation is somewhat better in the case of benthic Decapoda; not only
because most of them are egg-bearing animals, but also due to the fact that
Gurney, the undisputed authority on decapod larvae, had had the opportunity to
collect them personally. Larvae or egg-bearing females of 11 species of Decapoda
were identified in the Canal waters (BaIss, 1927; Calman, 1927a; Gurney, 1927a;
Holthuis, in Por and Ferber, 1972). Gurney adds to the list another two unidentified types of crab larvae. If one considers, according to Holthuis (1956), that there
are 38 species ofDecapoda known from the Canal proper, then the 11-13 species
known to reproduce there represent quite a high percentage. This is even more
impressive if one takes into account that the Cambridge Expedition collections
covered only the months of September and October. In the case of the ascidians of
the Cambridge Expedition the ratio of the ovigerous species is equally high, i.e.
eight out of 25 (Harant, 1927). The case of the Decapoda and Ascidiacea may
81
2.8 Reproduction and Sizes of Animals in the Suez Canal
This chapter would have been large1y unnecessary had it been c1ear to everybody that the Suez Canal is an environment to life as every other water body and
not only a passage way, as it has been abstractly considered.
Time and time again, authors were surprised to report that they found reproductive or egg-bearing species in the Canal, on the assumption that the Canal
system operates like a hypersaline or brackish lagoon, with adult populations
either leaving for reproduction or having to be constantly reinforced by new
swept-in swarms of larvae. Such a behavior can be expected from good swimmers:
fish, penaeid shrimps, portunid crabs, or cephalopods. However, there are no
indications that a migratory "catadromous" life cyc1e actually exists in any of
these species in the Canal. The system, especially owing to the brackish areas of
Lake Timsah, may in fact offer a very wide range of salinities for those species that
need a certain salinity value in order to reproduce. Catadromous reproductive
behavior is probably present but far from being the rille.
Among fishes, Tillier (1902) reports the following species as reproducing in the
Canal: Atherinaforskalii (= Atherina pinguis), Clupea quadrimaculata, Crenidens
forskalii (= C.crenidens), Mugil seheli, M.capito? and M.saliens? No additional
nektonic fish in spawning stage has been reported since!
The nektonic decapods positively known to reproduce in the Canal are: Penaeopsis stebbingi, the larvae of which Gurney (1927 a) found in the Canal, and the
swimming crab 1halamita poissoni, which Calman (1927 a) found to be ovigerous.
From the more "sedentary" organisms of the Canal re1atively few have been
reported to reproduce there. In fact, the collections are not specially analyzed for
that; reporting of"adillt" specimens is not enough. Fishes, for example, have to be
dissected. Hippocampus hippocampus males were found with brood pouches full of
deve10ping eggs (Steinitz and Ben-Tuvia, 1972).
In molluscs the situation is similar for the bivalves; the egg-masses of Gastropoda can, however, be identified, especially by the large-sized spawns. The only
cases in which reproduction of molluscs within the Canal could be proven are
those reported by Barash and Danin (1972) in which egg masses were found, i.e. of
Murex anguliferus, another species of Murex and an egg collar of Natica sp.
The situation is somewhat better in the case of benthic Decapoda; not only
because most of them are egg-bearing animals, but also due to the fact that
Gurney, the undisputed authority on decapod larvae, had had the opportunity to
collect them personally. Larvae or egg-bearing females of 11 species of Decapoda
were identified in the Canal waters (BaIss, 1927; Calman, 1927a; Gurney, 1927a;
Holthuis, in Por and Ferber, 1972). Gurney adds to the list another two unidentified types of crab larvae. If one considers, according to Holthuis (1956), that there
are 38 species ofDecapoda known from the Canal proper, then the 11-13 species
known to reproduce there represent quite a high percentage. This is even more
impressive if one takes into account that the Cambridge Expedition collections
covered only the months of September and October. In the case of the ascidians of
the Cambridge Expedition the ratio of the ovigerous species is equally high, i.e.
eight out of 25 (Harant, 1927). The case of the Decapoda and Ascidiacea may