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Revision of the Dalatiid Shark Genus Squaliolus: Anatomy, Systematics, Ecology

1978; American Society of Ichthyologists and Herpetologists; Volume: 1978; Issue: 4 Linguagem: Inglês

10.2307/1443686

1938-5110

Jeffrey A. Seigel,

Fish Biology and Ecology Studies

Detailed descriptions of the teeth, vertebral column, claspers and viscera are presented for Squaliolus laticaudus and compared with those of two related species, Euprotomicrus bispinatus and Isistius brasiliensis. Jaw teeth of S. laticaudus are heteromorphic and closely resemble those of E. bispinatus. The total number of vertebrae (I = 60) found in S. laticaudus is the lowest of any known shark. The vertebrae most closely resemble those of E. bispinatus in number and structure. The claspers are of squaloid type and display characters which not only may be used to distinguish Squaliolus, but also may indicate a close phylogenetic relationship between S. laticaudus and E. bispinatus. In most visceral characters, S. laticaudus is more similar to E. bispinatus than to I. brasiliensis. Squaliolus is known from the Indo-west Pacific, North Pacific, North and South Atlantic and Indian oceans and seems to prefer waters associated with continental land masses. The vertical distribution is from 500 m during the day to 200 m at night. Squid may comprise a major portion of the diet along with midwater fishes. Bioluminescence is reported for the first time in Squaliolus; the photophores most closely resemble those of E. bispinatus in size and structure.