ABSTRACT
Gobies are generally small-sized fi sh which surpass only occasionally the size of 10 cm and become very seldom larger than 50 cm. Th ey mostly live on the bottom (benthal), only some species swim over the substrate (suprabenthal) or in the free water (pelagial). Th eir body shape is terete, approximately cylindrically and tapered, or depress, dorso-ventrally fl attened (Horn, 1999), but rarely compress. Th e pelvic (ventral) fi ns are situated at the throat where the pelvis is connected to the shoulder girdle (cleithrum). Th e pelvic fi ns can be fused together forming a disc with an anteriorly dermal fold, the frenum, which adapts this fin-complex to function as a sucker by which gobies can attach to the bottom and can withstand streams or flows. Whereas all members of the subfamily Eleotrinae are characterized by separated pelvic fi ns, the reduction of the pelvic disc in the Gobiinae must have developed independently in several lines. Th ere are
various intermediate steps of this development, from reduction of frenum to deep incisions between the fi ns (Miller and El Tawil, 1974; Heymer and Zander, 1978). Reduced suckers can be found in gobies of deeper layers living of more than 10 m depth like the Mediterranean species Gobius auratus, G. fallax, G. vittatus and G. xanthocephalus (Heymer and Zander, 1978, 1992; Zander, 1992), Lebetus guilleti, L. scorpioides (Miller and El Tawil, 1974), Odondobuenia balearicus and Vanneaugobius pruvoti, all from coralligeneous habitats. Also the amphibious Periophthalmus spp. from mud fl ats reveal the same evolutionary trend (Fig. 3.2.1). Heymer and Zander (1978) observed that the separated pelvic fi ns of Gobius vittatus and G. xanthocephalus are used to support the body by turning forward-downward when resting on the ground (Fig. 3.2.2).
