LESSON 1:
General Description and Scientific Classification
By the end of this lesson, you should be able to:
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Give a general description of a manta ray that includes:
- Distribution
- Size and shape
- Meaning of name
- Hawaiian name
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Name the scientific term for cartilaginous fishes.
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State one important difference between stingrays and manta rays.
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Identify the common characteristic of devil rays.
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Name the two species of manta rays.
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Describe variations in manta coloration.
General Description
Manta rays are large sea animals that live in tropical, sub-tropical, and temperate waters worldwide. Their side or pectoral fins have evolved into wide triangular wings that they use to easily propel themselves through the water. With a diamond shaped body and wing spans reaching 20' across, manta rays are one of the largest animals in the ocean.
Their broad blanket-like bodies earned them the name manta that means cloak or blanket in Spanish. In Hawaiian, they are called hahalua.
KINGDOM: Animalia
PHYLUM: Chordata
CLASS: Chondrichthyes
SUBCLASS: Elasmobranchii
SUPERORDER: Batoidea
ORDER: Myliobatiformes / Rajiformes
FAMILy: Mobulidae
GENUS: Manta
SPECIES: birostris or alfredi
Sharks and Rays
Manta rays are related to sharks. Sharks and rays belong to the scientific classification Chondrichthyes and share the common characteristics of cartilaginous skeletons and no swim bladder.
Sharks and rays are also grouped together in a subclass called Elasmobranchii, but most people simply use the word Elasmobranch when discussing sharks and rays. As far as the meaning of this word, the Greek root elasmo means 'plate' and branch means 'gills'. The word relates to the 5 - 7 separate openings and platelike gills of sharks and rays.
Unlike many shark species, manta rays do NOT have sharp teeth. Manta rays do possess a tooth band that is more like a long strip of sandpaper that runs along the lower jaw only.
Manta ray versus Stingray
Manta rays are related to stingrays. When classified scientifically, rays belong to the superorder of Batoidea and stingrays and their relatives (including manta rays) belong to the order Myliobatiformes. Both have flattened body shapes and wide pectoral fins that are fused to the head.
Differences between stingrays and manta rays include:
Stingrays dwell on the ocean bottom, but manta rays live in the open ocean. A stingray's mouth is located on the underside of its body whereas the mouth of the manta ray is along the front edge of its body.
One of the most important differences between manta rays and stingrays is that manta rays do NOT have a tail stinger or tail barbs like stingrays.
Devil Rays
Manta rays belong to the family of rays called Mobulidae and often referred to as devil rays. Devil rays share the common characteristic of cephalic or head fins. When unfurled, the fins help to funnel in food and water into the mouth. To make the fins more streamlined, devil rays can roll up these flexible appendages. When furled, these fins were thought to resemble a devil’s horns.
There are 9 species of Mobula rays and 2 species of Manta rays. The Mobula ray mouth is located under the front edge of its body whereas the manta mouth runs along the front edge. Some mobula ray species have exposed tail spines and some are mustard colored.
Manta Species
Manta rays are divided into two different species:
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Manta birostris
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Manta alfredi
Manta birostris typically roam the open ocean and are migratory. They are regularly sighted at offshore islands, oceanic seamounts, and submarine ridge systems. This species can reach up to 23' across and may weigh up to 5000 lbs. Manta birostris is occasionally sighted along the Kona Coast.
Manta alfredi is a smaller species that may reach up to 12’ across and may weigh 1000-3000 lbs. This species is commonly sighted near shore around coral reefs, often times in residential groups.
Manta alfredi is the species of manta ray at the Kona manta ray night dive and snorkel sites.
Manta Coloration
Like many other open ocean animals, most manta rays exhibit counter shading - dark on dorsal (top) side and light ventral (bottom) side. Typically, manta rays have a dark dorsal side with light shoulder bars.
In a study conducted by Dr. Csilla Ari (2014), rapid color changes on the dorsal surface of captive manta rays were observed during exposure to certain environmental stimuli. The greateset changes occured on the head and shoulder bars prior to feeding and intense social interactions.
The ventral surface of manta rays can be light or dark. Typically, Manta birostris has a light ventral side with a few dark spots and wide gray bands along the back edge of the wings. Manta alfredi can also have a light ventral side, but often has a big blotchy spot pattern between the gills as well as other spots throughout the ventral side.
The most extreme difference in manta coloration comes with the “black manta”. These mantas are predominantly black on their ventral surface with patches of white. Both Manta birostris and Manta alfredi species have a black coloration. Black mantas are sighted occasionally along the Kona coast of Hawaii.
Scientific Classification
Taxonomy is the science of classifying and naming organisms based on shared characteristics or phylogenetic relationships. As new scientific discoveries are made, classifications are changed. This is what we could find as the most current taxonomy for manta rays.
Resources:
Ari, C. (2014). Rapid coloration changes of manta rays (Mobulidae). Biological Journal of Linnean Society 113, 180-193.
Douady, C.J., Dosay, M., Shivji, M., Stanhope, M. (2002). Molecular phylogentic evidence refuting the hypothesis o Batoidea (rays and skates) as derived sharks. Academic Press. Retrieved from
Greek and Latin Root Words for Biology. Retrieved from http://courses.washingoton.edu/chordate/453labs/Greek-Latin-Roots-Biology.pdf
Marshall, A., Bennett, M.B., Kodja, G., Hinojosa-Alvarez, S., Galvan-Magana, F., Harding, M. Stevens, G. & Kashiwagi, T. 2011. Manta birostris. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>.
Marshall, A. D., Compagno, L. J. V., & Bennett, M.B. (2009). Redescription of the genus Manta
with resurrection of Manta alfredi (Kreft 1868) (Chondrichthyes; Myliobatoidei; Modbulidae). Zootaxa 2301, 1-28.
National Oceangraphic and Atmospheric Administration Fisheries. Retrieved http://courses.washingoton.edu/chordate/453labs/Greek-Latin-Roots-Biology.pdf.
Randall, J.E. ((2007). Reef and Shore Fishes of the Hawaiian Islands. Sea Grant College Program, University of Hawaii: Honolulu.
Taxonomy. Retrieved from http://www.biology-online.org/dictionary/Taxonomy.