24 p. : 24 cm

"Opsanus phobetron is described from the western Bahamas, Cuba, and the Isle of Pines. It was observed to nest in late December at Bimini, Bahamas. The black mouth functions as a warning mechanism, and under low albedo conditions, as at Bimini, the dark coloration is indicated to be of social significance. Attention is called to unidentified samples of Opsanus from Little Bahama Bank and the Gulf of Campeche. The ranges and recognition characters of O. pardus, O. tau, O. beta, and O. barbatus are discussed. Opsanus vandeuseni Fowler is referred to the synonymy of Opsanus beta (Goode and Bean). Opsanus hildebrandi Breder is placed in Marcgravia Jordan and appears not to be identical with M. ctyptocentra (Cuvier and Valenciennes). The low numbers of dorsal and anal rays attributed to Opsanus in the literature are valid if the Queensland genus Batrachoemus Ogilby is considered identical with Opsanus. Published paleotemperature measurements indicate that the 'tropical' Atlantic and Caribbean regions were not tropical during the last glacial period. The trans-Florida faunal province, now absent from southern Florida, was continuous around the southern tip of the Florida land mass; at the same time coral reefs were absent from most of the West Indies, and the shore fauna was predominantly temperate in the north and predominantly subtropical in the south. It is improbable that the Florida peninsula neck was submerged during Pleistocene interglacial periods. The presence of marine fishes in Florida fresh waters is not considered significant from the standpoint of historical zoogeography, and it is suggested that the elevated chlorinities in Florida fresh waters are maintained by current processes. Even if the neck of the Florida peninsula had been drowned, the Gulf of Mexico populations of trans-Florida fishes probably could not utilize the passage, as the temperatures would have been too high. The Gulf of Mexico disjunct trans-Florida populations are interpreted as glacial rather than interglacial relicts, and a comparison is drawn between the Gulf of Mexico and the Sea of Okhotsk. Because the spawning threshold temperature of Opsanus parallels the minimal thermal tolerance of reef corals, Opsanus is considered to be an 'indicator' of temperate coastal waters. Owing to thermal requirements and tolerances, Opsanus survives as a glacial relict in a few West Indian localities. During the last glacial period, the northern distributional limit for Opsanus may have been as far south as southern Florida. Opsanus, lacking pelagic life-history stages, could have dispersed through the West Indies by passive transport during storms"--P. 20-21

Title from caption

"October 12, 1961."

Includes bibliographical references (p. 21-24)

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