The spinetail mobula (''Mobula japanica''), also known as the spinetail devil ray or Japanese mobula ray, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

marine fish which belongs to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Mobulidae. The spinetail mobula gets its name due to its devil like appearance from the "horns" on its head and the unique spines on its tail. Generally, these rays love to be mobile and show off their aerial acrobatics. ''M. japanica'' can be found throughout the

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

and

sub-tropical The subtropical zones or subtropics are geographical and climate zones immediately to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 3 ...

waters of the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

and eastern

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

Taxonomy

''Mobula japanica'' falls under the order Myliobatiformes and family Mobulidae. The Mobulidae family is a family of rays, manta rays and devilfish specifically, consisting of 11 species. The IUCN suggests that the species should be considered conspecific with the devil fish (''Mobula mobular'') Due to its low population growth and low reproduction rates, there isn't much variability or "branch off" species from ''M. japanica''. Recently, a study found no genetic difference between north-west Pacific, north-east Pacific, Indian and east Atlantic ocean populations of ''M. japanica'', suggesting the hypothesis of geographic isolation. Given that all the ''M. japanica'' are genetically identical worldwide, it seems relatively stagnant in its position in the phylogeny.

Description

The spinetail mobula ray is a large ray which can grow up to a maximal width of ; average width is . Like most rays, it is dorsoventrally flattened, also known as a depressed body form, and has relatively large triangular

pectoral fins Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only b ...

on either side of the main body disc that sit slightly convex. At the front, it has a pair of cephalic fins which are forward extensions of the pectoral fins. These can be rolled up in a spiral for swimming or can be flared out to channel water into the ventral mouth when the animal is feeding. ''M. japanica'''s eyes sit on the side of the head, while the mouth is on the underside for convenient filter feeding as it swims through the ocean. The background body coloration of the dorsal side is deep blue-mauve with a large black band stretches from eye to eye. The ventral side is white. The inner surface of the cephalic fins are silver-grey with black tips, while the outer surface and side behind eye are white. The coloration of ''M. japanica'' serves as protection from predators, such as larger sharks and killer whales, both above and below them in the water column. When looking down, their dark dorsal slide allows them to blend in with the deep blue below and when looking up, their white ventral side allows them to appear homogenous with the lighter surface hit with sunlight. ''Moubla japanica'' is often mistaken for its relative, the giant manta ray (''M. birostris''), however the species can be distinguished from other large rays by its projecting head, narrower head and body, subterminal mouth, small spine at the base of the tail, a white-tipped dorsal fin. Its spiracle is just above the area where the pectoral fin meets the body. M japanica

Distribution and movement

The spinetail mobula is a mobile species, usually traveling in small groups together. They are assumed to have a circumglobal distribution in tropical and temperate waters, both inshore and offshore and fully oceanic. Their widely distributed pattern has to do with factors such as food availability and water column dynamics, with which they adapt accordingly based off of the surrounding ecosystem and environment. The southern Gulf of California appears to be an important mating and pupping ground. Limited studies have shown that they have a preference for more warm and shallow waters like the Gulf of Mexico, Mediterranean Sea, and southwest Pacific Ocean. However, one study in particular found that despite their "preference", the spinetail mobula distribution is directly related to seasonal upwelling systems with high productivity in the cold coastal waters, such as the eastern Pacific Ocean. Ultimately, their movement is dictated by environmental conditions that affect the zooplankton they follow. This makes them highly susceptible to environmental changes such as ocean acidification and global warming. During the months before summer, many individuals of ''M. japanica'' inhabit the continental shelf before migrating to tropical waters for the rest of the year. Although many studies have been done, spatial constraints and low sample sizes prohibit full understanding of the relationship between the rays' spatial distribution and the conditions of the environment around them. A recent study following the depth and temperatures at which these organisms reach within a 24 hour time period shows that ''M. japanica'' spend the days in deeper waters and then undergo a nocturnal migration to the surface at night to feed.

Feeding

''Mobula japanica'' is a filter feeder, meaning they feed on small organisms, such as zooplankton or small crustaceans, by straining nutrient rich water through their system. As previously mentioned, their movement is highly correlated to the food abundance causing them to readily move up and down the water column. During upwelling events, spinetail mobula rays rush to the coasts and take advantage of the boost in zooplankton and nutrient abundance. Scientists conducted a study that measured the diversity and abundance of a random group of ''M. japanica''. This provided a better understanding for the specific details of the spinetail mobula ray's diet. The study found 5 different groups that made up the stomach contents: decapods, copepods, gastropods, Polychaeta and other prey. With decapods being the highest percentage, at 99.54%, their label as plankton filter feeders is further confirmed. They are classified as omnivorous animals, yet can be carnivorous if given the opportunity.

Biology

The spinetail mobula ray has a

lifestyle and has been observed both alone and in groups. It feeds on

zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

by filtering sea water. As all Mobulidae, species is

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a "bridging" form of reproduction between egg-laying oviparity, oviparous and live-bearing viviparity, viviparous reproduction. Ovoviviparous animals possess embryos that develo ...

. After mating, the fertilized eggs develop within the female's

oviduct The oviduct in vertebrates is the passageway from an ovary. In human females, this is more usually known as the fallopian tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, or will dege ...

. At first, they are enclosed in an egg case while the developing embryos feed on the yolk. After the egg hatches, the pup remains in the oviduct and receives nourishment from a milky secretion. The pup is in disc width at birth. Females typically only give birth to one pup. They have low somatic growth rate, low annual reproductive output, and low maximum population growth rates, suggesting they have low productivity.

Threats and conservation

The spinetail mobula is threatened by both targeted and accidental capture in various fishing methods. Despite conservation efforts, global landings of these rays have risen due to gill plate demand. The gill plates are used in traditional medicines to treat a range of ailments, including cancer. Commercial and artisanal fisheries target ''M. japanica'' in their warm water habitats. In addition, this species is also a victim of bycatch, getting caught in gill and trawl nets intended for other species. Furthermore, due to their movement around the world being tied closely to the environment that influences the distribution of zooplankton, they are more susceptible to environmental changes such as ocean acidification and global warming. The effects of climate change can throw off natural systems and processes that drive zooplankton abundance in many parts of the world, which then in turn would affect ''M. japanica'' by stretching the geographic ranges by which they comfortably live or by changing them biologically to adapt to these new conditions. Especially due to their low reproductive rates, late maturity and slow growth, the spinetail mobula ray is particularly vulnerable and it would take a while to recover from depletion or exploitation. Additionally, habitat destruction and pollution pose indirect threats to their survival. However, with more push for legislation to protect our oceans and Earth in general, this species could still reap the benefits of that. Voters have the power to spark more conservation efforts under laws and policies. For example, spinetail mobula rays are protected under the Wildlife Act of 1953 in New Zealand's territory. Hunting, killing, or harming devil rays in general can lead to up to $250,000 and six months in prison. If more places around the world could adopt policies like this, we could see drastic change in the conservation status of ''M. japanica'' and other rays.

References

{{Taxonbar, from=Q1754242, from2=Q11086609 Mobula Fish of Japan Pantropical fish Fish described in 1841 Taxonomy articles created by Polbot