SCYPHOZOA 



By Joel W. Hedgpeth, Scripps Institution of Oceanography 



With the exception of Mayer's studies at Tor- 

 tugas nearly 50 years ago there has been no serious 

 attempt to study the medusae of the Gulf of 

 Mexico. While there are a few scattered records 

 of medusae along the coast, little is available on 

 the occurrence of jellyfish in the pelagic regions of 

 the Gulf or of the deep-water forms. 



There are a few large medusae which charac- 

 teristically occur in the neritic waters of the Gulf 

 of Mexico from Florida to the Rio Grande. Fore- 

 most of these is Stomolophus meleagris, the cab- 

 bagehead. This rhizostome often occurs in vast 

 numbers in lower bays and around passes at the 

 end of the summer. Such swarms were observed 

 at Port Aransas, Texas, on August 4-5, 1947, and 

 September 20, 1948. The latter swarm was esti- 

 mated to be drifting through the channel on an 

 incoming tide at the rate of 2 million an hour. 

 The bobbing white domes of these jellyfish seemed 

 to be packed almost solidly across the 800-yard 

 width of the channel. Occasionally, Stomolophus 

 is caught by the ton in shrimp trawls, and there 

 has been some speculation about a possible eco- 

 nomic use for these animals. Mayer mentions 

 several oriental species which are pickled, but such 

 a specialty delicatessen use would hardly cat into 

 the unwanted surplus. With the possible excep- 

 tion of a few hypersensitive individuals, Stomolo- 

 phus is not a dangerous species to bathers and may 

 be handled with impunity. It is a fine animal for 

 physiological experimentation. 



Another rhizostome, Rhopilema verrilli, may be 

 more common than suspected. Specimens have 

 been taken from Mobile Bay, and one was col- 

 lected at Port Aransas. This is a much larger 

 medusa than Stomolophus, and Mayer suggested 

 that it is a southern form which occasionally 

 extends as far north as Long Island. Burkenroad 

 (personal communication) considers it common in 

 Chandeleur Sound. 



One of the most common jellj^sh in the bays, 

 especially during the summer months, is Dacty- 



lometra quinquecirrha, a semaeostome medusa" 

 This medusa may cause a mild rash or unpleasant 

 sting,' but severe cases of jell3^sh poisoning by 

 this species are rarely reported (Hedgpeth 1945). 



An occasional denizen of bay waters is the moon 

 jelly, Aurellia aurita. While it is usually more a 

 frequenter of the lower bays and gulf waters, it 

 at times outnumbers Dactylometra in the bays. 



Another large Medusa in Gulf waters is the 

 lion's mane, Cyanaea capillata var. versicolor. 

 Mayer gives the southern limit of this variety as 

 Cape Canaveral, Florida, and did not find it at 

 Tortugas. R. O. Christenson, of Alabama Poly- 

 technic Institute, identified this medusa from 

 Mobile Bay, on February 20, 1938. A large, 

 reddish, striped medusa was observed on an out- 

 going tide at Port Aransas, Texas, on March 16, 

 1948, which appeared to be this species. It is of 

 interest to note that both these records are to- 

 ward the end of the Gulf coast winter. Burken- 

 road (personal communication) considers it com- 

 mon in Louisiana waters. 



According to Mayer, some 75 species of medu- 

 sae occur at Tortugas. Nine of these are scypho- 

 zoans, and the great majority are hydromedusae, 

 more properly considered under hydroids (p. 267). 

 There are probably more species to be found in 

 the Gulf. Following is a list of the Scyphomedu- 

 sae known to occur in the Gulf of Mexico, prin- 

 cipally at Tortugas. This list includes the 9 

 species discussed by Mayer and the 2 species 

 whose occurrence in the Gulf was not known to 

 him: ^ 



Carybdaea aurifera Mayer, pp. 510, fig. 328. 

 A rare form taken only twice at Tortugas. 



I The Portuguele Man-of-War, Physalia, is more dangerous and probably 

 causes some distress to unwary bathers every season. This siphonophore 

 is often washed up on the outer beaches in great numbers, and its stranded 

 pneumatophores are heard popping under the wheels by motorists driving 

 on the beach. Two smaller siphonophores, Porpila linneana and Velella 

 velieia, are often stranded on the beach, 



' All page and figure numbers given after the name of the species refer to 

 Mayer's publication. 1910. 



277 



