Friday, 26 May 2017

Stoplight Parrotfish

Stoplight parrot fish

Habitat and Environment

Sparisoma viride, which is commonly known as the Stoplight Parrotfish, can be found along southern Florida, Bermuda, Bahamas, Carribean Sea, and within the Gulf of Mexico (Fish Background). Our sighting of this fish occurred in the Florida Keys at the following sites: (1) the mid-channel reefs Coffin Patch and Pillar Patch and (2) Looe Key which was a reef crest coral reef. These fish prefer coral reef habitats and can have longer lifespans at offshore reefs in comparison to inshore reefs (Additional Basic Background on Stoplight Parrotfish). Along coral reef habitats these fish are commonly found anywhere from 3-50 meters in down in the water column. Their common predators in these areas include snappers, jacks, moray eels, and other carnivorous fish.

Appearance and Physiology

Subterminal Female and Primary
 Male Characteristic Coloration
Picture taken at Looe Key in
Florida Keys
The Stoplight Parrotfish has a typical parrotfish appearance consisting of large heavy scales along it's body and cheeks, beak-like jaw, and oblong body. Their beak-like jaw is formed from the fusion of their front teeth and is continuously growing through their lifetime. In the back of their throat they possess pharyngeal teeth which consist of convex plates of interlocking sets of molariform teeth. They utilize their pharyngeal teeth to crush coral reef fragments that they break down. The common food source for this herbivorous fish are algae and corals. After digesting the coral they eat and extracting the nutritious polyp, the coral waste is excreted as fine white sand. Current max length of this parrotfish is around 55 cm.

Terminal Male (aka Supermale)
 Characteristic Coloration.Picture
 taken at Pillar Patch in Florida Keys
Distinguishing characteristics of this type of parrotfish pertain to its coloristic patterns. Two distinct dimorphic forms exist with one representing primary males and subterminal females and the other form representing terminal males. The subterminal female and primary male have the following coloristic features: (1) mottled reddish brown trunk with white scales mixed in, (2) bright red belly, (3) red dorsal, anal, and back half of the caudal fin, and (4) white pectoral and first half of the caudal fin. In comparison the terminal male, also known as the supermale, has the following coloristic features: (1) a bright green trunk, (2) diagonal orange bands on upper head, (3) yellow spot on their gill and at the base of caudal, and (4) an orangish red crescent on the back of their caudal fin (Additional Basic Background on Stoplight Parrotfish). This caudal coloration pattern of orangish red, green, and yellow are where the common name originated from as it gives it a stoplight appearance.

Reproduction

The Stop

light Parrotfish has very interesting reproductive strategies. These fish typical reach sexual maturation in their third year of life and are able to undergo sex reversals as part of their hermaphroditic life styles. The primary males, which are born male, do not undergo a sex change. Instead these males spawn in groups with one female (Warner 1988). The subterminal females are the ones able to undergo sex changes. These sex changes are thought to be due to low sex ratios and are known as protogynous hermaphroditism (Girlolamo 1999). The males that result from this sex change are referred to as either supermales or terminal males. The supermales are the dominant, more aggressive male compared to the primary male and are known to form harems in order to claim the most females (Mumby 2002). An advantage thought to arise due to this reproductive strategy is that female size does not particularly influence their ability to reproduce, so they stay females when they are younger and smaller. However, once these females reach a certain size and sex ratios are off, then they can shift into the male form. Their larger sizes later in their lifetime allow them to succeed in protecting their harem and territory and making them competitively dominant to the primary males (Warner 1982). Along with their ability to change sex if necessary, they can also reproduce year round, with more intense spawning occurring during the summer months.

Interesting Facts

Some interesting facts about this fish is that due to their diurnal nature, they are only active during the day and rest at night. To avoid predation they employ a couple tactics. Instead of hiding in crevices they sleep in relatively open spaces as a way to quickly escape any oncoming predators that may try to corner them. Although this may seem like it leaves them vulnerable they have an interesting strategy to counteract the vulnerability open spaces inherently possess. They are known to surround themselves in a mucous cocoon for extra protection when sleeping (Additional Basic Background on Stoplight Parrotfish).  It is thought to deter predators by masking their scent and visual appearance, along with having a bad taste for predators. Unfortunately, we did not observe these fish during the night to witness them cocooning, but I would love to be able to observe them in this form of protection.

Another interesting fact about them pertains to how they swim. Unlike other fish species, Stoplight Parrotfish do not utilize their caudal fin as a primary source of propulsion. Instead, they only utilize their caudal fin for quick bursts of speed as a way to escape from predators. For primary propulsion the Stoplight Parrotfish instead utilizes their pectoral fins (Additional Basic Background on Stoplight Parrotfish).

References and Links

Basic background website links

·         Fish Background
·         IUCN Listing

Article Refrences

·         Girlolamo, M. Social organization and sexual pattern in the Mediterranean parrotfish Sparisoma cretense. Marine Biology (1999) vol. 135, no. 2, pp. 353-360

·         Mumby, P. and Wabnitz, C. 2002. Spatial patterns of aggression, territory size, and harem size in five sympatric Caribbean parrotfishes. Environmental Biology of Fishes. 63: 265-279.


·         Warner, R. Metamorphosis: Among tropical fish, when the going gets tough, the tough change sex. Science, Dec. 1982

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