Friday, November 15, 2013

Archer fish(Toxotes jaculatrix)

                     Under Water Archer 


Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Toxotidae
Genus: Toxotes
Species: jaculatrix
Author: Cuvier, 1816

Fishes forage for food in various ways and the way it forages it depends on the environment, physiology, morphology. Here, there is a fish that uses water as arrow to catch its prey. Archer fish is distributed in estuaries, mangrove swamps and river mouths of Indo-pacific waters. It posses laterally compressed body with five black markings on either sides. Unlike other fishes the dorsal fins present at the posterior end of the body. Juveniles grow in fresh water and move to brackish and then to sea when as it become adult. Mouth is protractible with groove in upper end that helps in ejecting water to catch its prey. This fish can grow up to 30 cm in length. Archer fish feeds on land based insects such as spider, grasshopper, butter fly etc.

Speciality of Predation
Every fish has their own way of predating their prey; Archer also follows its own way for predation. It spits water as arrow to catch the prey present above the surface of water. Strategy behind this is, when it sees the prey it roles its eye to get a full image of the prey on ventral temporal periphery of retina and spits the water by placing tongue at groove present in upper end of mouth. It acts as a tube through which the water passes in jet speed by compressing operculum. It usually shoots at an angle of 74 degree but, the aim is accurate at 45 and 110 degree. Accuracy is not only because of having good eyesight, it also knows to compensate refraction of light that passes air sea interface during aiming. Italian scientists demonstrated the force of the water is based on water dynamics rather than using internal muscles. It modulates the velocity of the jet as it alters its shape through air. The top of the jet increases in volume as it gets liquid from tail to form a big drop that hits insects with greater force.  Adults almost hit the prey in a single shot but, juveniles’ accuracy increases as it gets adult. Hence, juveniles hunt in groups to catch their prey.

Acknowledgement
Pictures and video were collected from following links
http://ies.franciscoasorey.ccmc.climantica.org/2012/10/28/un-chorro-mortal/