HYDROIDS OF THE GULF OF MEXK^O 



By Edward S. Deevey, Jr., Osborn Zoological Laboratory, Yale University 



The life cycle of hydroids "typically" alternates 

 between a sessile, asexually reproducing polyp or 

 hydroid stage and a free-swimming sexual medusa 

 stage. One generation or the other may be re- 

 duced, however, or even suppressed entirely. 

 Because of this fact and because hydroids are 

 obtained by shore collectors or bj^ dredging, 

 whereas medusae form part of the plankton and 

 are studied by different zoologists, the ta.xonomy 

 of the group, is in an unhappy state. 



Closely related types may differ in a respect 

 that at first sight would appear fundamental: the 

 polyp may produce free-living medusae, or the 

 medusa may remain permanently attached to the 

 polyp, even degenerating completely except for 

 its sex products, which then appear to be the sex 

 products of the polyp. This distinction, far from 

 being of subordinal rank, may split a genus down 

 the middle or, at most, may divide closely related 

 genera from each other, according to one's view 

 of what constitutes a generic character. That is, 

 unless the structural characters of the hydroid are 

 to be given no weight whatever, the mode of 

 reproduction cannot provide the basis for erecting 

 taxonomic categories higher than the genus. 



Thus, the hjxlrozoan systematist faces a real 

 dilemma, and he is not helped by the fact that 

 many typically reproducing species have received 

 different names as medusae and as polyps and 

 must continue to bear them until proof of their 

 identity is obtained. The writer is not a student 

 of medusae, and in fact his knowledge of hydroids 

 is largely confined to specimens preserved in alco- 

 hol. He is in no position to do anything abouc 

 the fact that even the families are differently 

 constituted in hydroid and medusa systematics, 

 and the task of fusing the two systems awaits an 

 abler zoologist. This chapter deals exclusively 

 with hydroids. 



The hydroid fauna of the Gulf of Mexico is 

 little known, and the chief purpose of this account 

 is to document this fact. A treatise on the Gulf 



of Mexico is a peculiarly appropriate setting for 

 such a catalog of ignorance, for what we do not 

 know about GuF hydroids should be especially 

 obvious against the massive backdrop of what we 

 know about the biology of the Gulf. 



COLLECTING 



Hydroid collect uig in the Gulf of Mexico has 

 been chiefly undertaken in the Tortugas and the 

 Florida Keys, but if we except the work of Mayer 

 (1910) as dealing almost entirely with medusae, 

 the only paper sp' ifically discussing the Tortugas 

 fauna is that of Wallace (1909). Gulf of Mexico 

 records are scattered through many papers (Fraser 

 1943, 1945; Jaderholm 1896, 1903, 1920; Leloup 

 1935, 1937; Perkins 1908; Pourtales 1869; Stechow 

 1912, 1919, 1923, 1926) and through the mono- 

 graphs of Nutting (1900, 1904, 1915), but system- 

 atic dredging in the region has not been under- 

 taken since the days of the Corwin and the Blake. 

 The collections of h. de Pourtales on the former 

 vessel were reported by Allman (1877), and those 

 of A. Agassiz on the latter were published by 

 Clarke (1879) and Fewkes (1881). 



The monograph of Fraser (1944) recapitulates 

 all the earlier records and adds many more, for 

 Fraser xamined the large collections in the 

 U. S. National Museum and the Museum of 

 Comparative Zoology whither most of the Amer- 

 ican hydroids collected in the nineteenth century 

 eventually made their way. It is possible to 

 extract from Fraser's book an essentially com- 

 plete picture of the hydroid fauna of the Gulf as 

 far as it is known. In fact, this procedure is the 

 basis of the present account. Fraser's list has 

 been expanded in only one noteworthy respect. 

 The survey of fouling on navigation buoys, 

 conduct 1 by the Woods Hole Oceanographic 

 Institution during World War II, yielded several 

 hur !red records of hydroids from the Bahamas,- 

 both coasts of Florida, and Texas. Most of these 

 are still unpublished, but those that are new 



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