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Sunday, June 26, 2011

The Beauty Wrasse

Beauty Of Animal | The Beauty Wrasse | The wrasses are a family, Labridae, of marine fish, many of which are brightly colored. The family is large and diverse, with over 600 species in 82 genera, which are divided into nine subgroups or tribes. They are typically small fish, with most less than 20 centimetres (7.9 in) long, although the largest, the Humphead wrasse, can measure up to 2.5 metres (8.2 ft). They are efficient carnivores, feeding on a wide range of small invertebrates. Many smaller wrasses follow the feeding trails of larger fish, picking up invertebrates disturbed by their passing.

Wrasses have protractile mouths, usually with separate jaw teeth that jut outwards. Many species can be readily recognized by their thick lips, the inside of which is sometimes curiously folded, a peculiarity which gave rise the German name of "lip-fishes" (Lippfische.) The dorsal fin has 8–21 spines and 6–21 soft rays, usually running most of the length of the back. Wrasse are sexually dimorphic. Many species are capable of changing sex. Juveniles are a mix of males and females (known as Initial Phase or IP individuals) but the largest adults become territory-holding (Terminal Phase or TP) males.

The wrasses have become a primary study species in fish-feeding biomechanics due to their jaw structure. The nasal and mandibular bones are connected at their posterior ends to the rigid neurocranium, and the superior and inferior articulations of the maxilla are joined to the anterior tips of these two bones, respectively, creating a loop of 4 rigid bones connected by moving joints. This "four-bar linkage" has the property of allowing numerous arrangements to achieve a given mechanical result (fast jaw protrusion or a forceful bite), thus decoupling morphology from function. The actual morphology of wrasses reflects this, with many lineages displaying different jaw morphology that results in the same functional output in a similar or identical ecological niche.

Most labroids are protogynous hermaphrodites within a haremic mating system. Hermaphroditism allows for complex mating systems. Labroids exhibit three different mating systems: polygynous, lek-like, and promiscuous mating systems. Group spawning and pair spawning occur within mating systems. The type of spawning that occurs depends on male body size. Labroids typically exhibit broadcast spawning, releasing high amounts of planktonic eggs, which are broadcast by tidal currents; adult labroids have no interaction with offspring. Wrasse of a particular subgroup of the Labridae family Labrini do not exhibit broadcast spawning.

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