Phylogeny, Biogeography, and Ecology
of the
American seven-spined Gobies
(A general introduction)

by James L. Van Tassell PhD
Biology Dept.
Hofstra University

The Tribe Gobiosomini, as originally proposed by Birdsong (1975) and later revised by Birdsong et al. (1988), unite what was commonly called the American seven-spined gobies and several closely allied genera, all endemic to the New World.  Additional genera were added to the tribe by Hoese (1976) and Birdsong & Robins (1995).  Genera currently included in the tribe are Aboma  Jordan and Starks, 1895; Akko Birdsong and Robins, 1995; Aruma  Ginsburg, 1933; Barbulifer  Eigenmann & Eigenmann, 1888; Bollmannia  Jordan in Jordan and Bollmann, 1890; Chriolepis Gilbert, 1892; Elacatinus  Jordan, 1904;Eleotrica  Ginsburg, 1933a; Enypnias  Jordan & Evermann, 1898; Evermannichthys  Metzelaar, 1920; Ginsburgellus  Böhlke & Robins, 1968; Gobiosoma Girard, 1858; Gobulus  Ginsburg, 1933; Gymneleotris Bleeker, 1874; Microgobius  Poey, 1876; Nes Ginsburg, 1933;, Ophiogobius  Gill, 1863; Palatogobius  Gilbert, 1971; Pariah  Böhlke, 1969; Parrella  Ginsburg, 1938; Psilotris Ginsburg, 1953; Pycnomma  Rutter, 1904; Risor  Ginsburg, 1933; Robinsichthys Birdsong, 1988; and Varicus  Robins & Böhlke, 1961.  Böhlke and Robins (1968) defined the genus Gobiosoma  to include the subgenera Austrogobius  de Buen, 1950,; Elacatinus  Jordan, 1904; Garmannia  Jordan and Evermann in Jordan, 1895; Gobiosoma  Girard, 1858; and Tigrigobius  Fowler, 1931.  While the tribe may not be monophyletic, later work by Birdsong et al. (1988) inferred a subset of the group, known as the ‘Gobiosoma  Group’ (all genera except Bollmannia, Microgobius, Palatogobius, Akko, and Parrella ) to be monophyletic.

Many of the genera within the tribe are monotypic. They include Aboma, Akko, Aruma, Eleotrica, Ginsburgellus, Gymneleotris, Nes, Ophiogobius, Palatogobius, Pariah, Risor, and Robinsichthys.  Several contain only a few species (Pycnomma, 2 spp.; Enypnias, 2 spp.; Psilotris, 3 spp.; Gobulus, 4 spp.; Evermannichthys, 4 spp.; Parrella, 5 spp.) and are rather distinctive.  The most speciose genera, other than Gobiosoma (37 spp.), are Microgobius (14 spp.) and Bollmannia (13 spp.).

Characters used to unite the Gobiosomini are a dorsal fin pterygiophore formula of 3-221110 ( in all genera except Evermannichthys, Pariah, and Risor ), a  vertebral count of 11+16-17 (in all but Evermannichthys, and Pariah ), and the fusion of hypurals 1+2 with 3+4 (in all genera except Aboma, Akko, Bollmannia, Microgobius, Palatogobius, and Parrella ) (Birdsong, 1975).

The largest genus, Gobiosoma, has been divided into as few as four or as many as seven subgenera (Ginsburg, 1933b, 1944; Böhlke and Robins, 1968; Hoese, 1971) based on squamation, cephalic pore patterns, or sensory papillae patterns.  The characters used to define the genus and to separate the subgenera phenetically include (1) the number of pores and the extent of development of the head lateral line canal system, (2) elongation of dorsal fin spines, (3) precaudal and caudal vertebral numbers, (4) the shape of the ‘tongue’,  (5) the extent of squamation on the body and (6) the presence or absence of basicaudal scales.  While the species within Gobiosoma are, in general, well-defined, their phylogenetic relationships have not been investigated cladistically.  Previous authors agree little on the arrangement of the species within the subgenera or which subgenera to include within the genus Gobiosoma.

The species of Gobiosoma  sensu (Böhlke and Robins, 1968) were first studied by Isaac Ginsburg in a series of papers from 1933 to 1953.  He recognized three genera  (Aboma, Gobiosoma, Garmannia ) based on the extent of squamation: Aboma (monotypic), completely scaled; Garmannia, scaled at least on the posterior half of the trunk and possessing four transverse scales on the caudal peduncle; and Gobiosoma, either completely naked or possessing only two modified basicaudal scales.  Gobiosoma  and Garmannia  were divided into numerous subgenera: Gobiosoma  into the subgenera Elacatinus, Nes, Gobiosoma, Aruma, Dilepidion  Ginsburg, 1933, Gerhardinus Meek & Hildebrand, 1928, and Garmannia  into the subgenera Tigrigobius, Gobicula, Ginsburg 1944, Gobiolepis  Ginsburg, 1944, Garmannia, Gobiohelpis  Ginsburg, 1944, Gobiculina  Ginsburg, 1944, and Risor, again based on the extent of squamation.  Ginsburg erected the subgenera  as  temporary holding areas for the species until he could obtain sufficient data on each species to change the arrangement.  In his final published papers, he alluded to sensory papillae patterns as a character that could be used to rearrange the species.  His later work on this subject, however, was never published.

Böhlke and Robins reviewed the Atlantic species of Gobiosoma  and closely related genera in 1968 and included nominal Pacific species of Gobiosoma  in discussing general relationships.  The genera included in their study were Gobiosoma, Risor, Ginsburgellus, Nes, Aruma, Enypnias, Barbulifer, Eleotrica, Gymneleotris, and Pycnomma.  Ten new species and one new genus were described. They elevated Ginsburg's subgenera Nes  and Aruma  to genera and made Garmannia  a subgenus of Gobiosoma.  Their classification was based on the presence or absence of oculoscapular and preopercular canal pores and numbers of vertebrae rather than on scale patterns as adopted by Ginsburg.  According to Böhlke and Robins, Gobiosoma was composed of five subgenera (Elacatinus, Gobiosoma, Austrogobius, Tigrigobius, Garmannia ).

Hoese (1971) revised the eastern Pacific species of Gobiosoma  in his doctoral dissertation.  The nine Pacific species, three of which were new, are separated by color pattern, extent of squamation, presence or absence of head barbels, cephalic lateral line pore patterns, fin ray counts, sensory papillae patterns, vertebral counts, elongation of the sphenotic, and changes in the length to width ratio of the skull.  He included the genus Aboma  as a subgenus of Gobiosoma  and commented on the type species, Aboma etheostoma, as perhaps the most primitive member of Gobiosoma.  Several new species were described and the subgenus Gobiolepis (Ginsburg 1944) was resurrected.