Shallow-Water Hydroids of Bermuda. The Athecatae

Abstract

sidered according to provisions of the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature [iczn|, 1985). Some of the nomenclatural problems encountered have been resolved here, while others will require submissions to the commission. Questions regarding the identity, synonymy, and systematic positions of taxa arose repeatedly during the course of this study. One quandary in particular involved the extent to which nominal species should be combined or divided. The hydrozoan literature is replete with extremes of taxonomic "lumping" and "splitting," and the confusion resulting from both. For example, Duchassaing and Michelotti (1864) viewed practically every morphological form of the hydrocoral Millepora Linnaeus, 1758, from the Caribbean as a distinct species, whereas Hickson (1898a, 1898b) recognized only one species in the genus worldwide. Most authors now follow Boschma (1948) in recognizing three species in the Caribbean, and about a dozen worldwide. Nevertheless, determining how far to go in combining or splitting nominal species is largely a matter of personal opinion. Most recent hydrozoan systematists have tended to be "taxonomic lumpers," and generally broad taxa have been recognized here. Reasons why relatively few species of hydroids are believed to exist worldwide were briefly stated by Cornelius (1981). Related to the question of lumping or splitting of taxa is the interpretation of hydroid species distribution. According to literature records, many species of hydroids are virtually cosmopolitan. Admittedly, certain hydroids are well adapted for long-range dispersal, and their rate of speciation seems to be rather slow (Cornelius, 1981). Yet the question arises whether some species are as widely distributed as records indicate, or whether their reported range is partly an artifact of the hydrozoan taxonomist's inability to discriminate distinct but closely related species. Hydrozoan classification is complicated by many factors, including the following: (1) the existence of separate hydroid and medusa generations in many species; (2) the legacy of separate classifications for hydroids and medusae; (3) the production of free medusae and fixed gonophores in closely related species; (4) the differential reduction of male and female gonophores in certain species; (5) the production in some taxa of morphologically dissimilar medusae by virtually indistinguishable hydroids, and vice versa; (6) the morphological variation sometimes displayed within a given taxon; (7) the scarcity of reliable taxonomic characters in various taxa; (8) the general lack of knowledge concerning the biology of these animals, including life cycles of many species. Classification of the order Athecatae Hincks, 1868, in particular is currently in a state of flux. Most authors over the past 30 years have regarded the Capitata Kiihn, 1913, as the most primitive suborder of the Hydrozoa, largely following Rees (1957). Athecate classification has been extensively modified recently by Peters...