Species

Foureye butterflyfish

October 27, 2011, 6:16 pm
Content Cover Image

Foureye butterflyfish, Saba. Source: Clark Anderson/Aquaimages.

Introduction

The foureye butterflyfish (scientific name: Chaetodon capistratus) is a member of the butterflyfish family (Family Chaetodontidae) that lives on coral reefs in the Western Atlantic Ocean and the Caribbean Sea. This species has an imaginative form of cryptic morphology, by exhibiting large spots on either side of its posterior, thus fooling predators who may then mistake its direction of forward motion. Foureye butterflyfish are one of the top ten commonest reef fish species in this marine region of the Western Atlantic.

 

.Foureye butterflyfish. Source: ''Reef Fish Identification'', New World Publications © 1994

 

 

Scientific Classification

Kingdom: Animalia (Animals)
Phylum:--- Chordata
Class:------ Osteichthyes (Bony Fishes)
Order:-------- Perciformes
Family:-------- Chaetodontidae (Butterflyfishes)
Genus:----------Chaetodon
Species:----------- Chaetodon capistratus (Linnaeus, 1758)

Physical Description

Foureye butterflyfish are small (7.5 to 15 centimeters in length) fish with slender oval-shaped bodies.  They are silver-gray in color, with many thin dark lines radiating diagonally from the mid-body.  They gets their name from the black spot, ringed in white located on the rear of their upper body near the base of the tail that looks like a large eye. In addition, this species has a black bar on the head that runs through theeye. 

This color pattern is thought to be an adaption to confuse predators.  Because the animal's true eye is hidden by the bar, predators may think that the eyespot indicates the presence of the individual's head.  Thus, if the predator anticipates that its prey will attempt to escape by swimming forward, that predator may tend to attack slightly "in front" of what it perceives to be the head of its prey, thus allowing the prey to escape.  In addition, the large eye could deter predators, because such a sizable eye causes a predator to think that the butterflyfish is larger than actuality.

C. capistratus manifests an extremely small pointed mouth located at the front of the tapered head.

Distribution 

caption Distribution of the foureye butterflyfish. Florida Museum of Natural History.

Foureye butterflyfish are found in the western waters of the Atlantic Ocean along the North and South American coasts, stretching from Massachusetts to Brazil as well as in the Gulf of Mexico and the Caribbean Sea.

Habitat

C. capistratus is usually found in shallow coral reefs at depths ranging from two to twenty meters. They typically stick relatively close to the safety of the reef.

Feeding Behavior

Foureye butterflyfish are browsers who feeds on anthozoans (corals) preferring hexacoral such as scleractinians, anemones, and zoantharians. They are reef fishes that not only rely on the corals for habitat but also food. Anthozoans are readily available on coral reefs therefore it's not surprising that anthozoan tissue is their main diet. They are considered active generalists because anthozoans have minimal nutritional value and in order to make up for that loss, they readily feed on fish eggs, worms or crustaceans when these foods are accessible. Having a mixing diet provides essential nutrients or a balanced diet for assimilation efficiency or both

Their bodies are well designed to allow this foraging strategy.  Their narrow bodies allow them the move through tight places in the reef as they are foraging.  They have good eyesight to allow them to detect their prey.  Their thin pointed mouth, which contains fine teeth, allows them to feed on individual polyps.

Behavior

Foureye butteflyfish are often observed in pairs foraging on the reef.  In areas of high density,  they may form social foraging groups of as many as 15 individuals.

The "social communication hypothesis" proposes that the eyespots should be variable among individuals because variability could  serve as differences that could be used to recognized individuals.  This hypothesis was supported by the fact that pairs of fishes display laterally to each other while rejoining after being separated. 

caption Tholichthys larvae of butterflyfish. Florida Museum of Natural History.

Reproduction

Most reproduction is thought to occur in the period from February to May.  Foureye butterflyfish are believed to be typically monogamous, but the species may mass spawn in areas with high population density. Spawning occurs in the water above the reef: both the male and female release a cloud of gametes into the water column where fertilization occurs. The number of eggs produced depends on the size of the female, ranging from hundreds to thousands. Eggs are buoyant and hatch within a day or two to produce a larvae with a yolk sac attached.  After a few days the yolk sac is absorbed, and the larvae continue their pelagic stage.  During this interval, the larvae develop a series of armor-like plates over their heads and bodies.  Eventually, the larvae settle on the reef and rapidly transform into juveniles that live in sandy areas around isolated coral heads and sponges, in sea-grass beds, or in mangroves. The juveniles live solitarily until they reach sexual maturity at about one year of age. 

Conservation Status

Foureye butterflyfish are widespread and abundant, such that the species is deemed not to be at risk.

References and Further Reading

Glossary

Citation

McGinley, M. (2011). Foureye butterflyfish. Retrieved from http://www.eoearth.org/view/article/152842

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