Description

Anatomy Lips of Labrus festivus 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.) and the Dutch name of "lipvissen". The dorsal fin has eight to 21 spines and six to 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 individuals), but the largest adults become territory-holding (terminal phase) males. The wrasses have become a primary study species in fish-feeding biomechanics due to their jaw structures. 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 four 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.

Fun Facts

Reproductive behavior Most labroids are protogynous hermaphrodites within a haremic mating system. A good example of this reproductive behavior is seen in the California sheephead. 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 numbers 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. Sex change in wrasse is generally female-to-male, but experimental conditions have allowed for male-to-female sex change. Placing two male Labroides dimidiatus wrasses in the same tank will result in the smaller of the two becoming female again. Additionally, while the individual to change sex is generally the largest female, evidence also exists of the largest female instead "choosing" to remain female in situations in which she can maximize her evolutionary fitness by refraining from changing sex