Introduction

BLUE-SPOTTED FANTAIL RAY (Taeniura lymma)

Belonging to the stingray family Dasyatidae (whiptail stingrays), T. lymma is a cartilaginous fish (their skeletal system is made of cartilage rather than bone like humans and other vertebrates) that is common throughout the tropical Indian and western Pacific Oceans, with a range that begins from the intertidal zone and extends up to a depth of 30 metres (100 feet). It can grow up to 35cm across and 80cm long, with a weight of up to 5kg

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conservation conservation

Conservation Status and Threats

Given the charismatic looks of T. lymma (read more about Physical Description), it is not surprising that it is perceived more as a friend rather than food or foe. But are we really treating it as such? Our actions actually say otherwise.

Fig. 2. IUCN status. Image retrieved from International Union for Conservation of Nature.

There is currently no data on the local status of T. lymma in Singapore but ever since 2005, T. lymma has been listed as "Near Threatened" (global status) under the International Union for Conservation of Nature (IUCN) Red List of Threatened Species

 . This is due to the following human activities and practices that continue to threaten its survival.

Having a positive image as a "friend" is generally perceived as a good thing. Especially in the field of conservation, it is likely the case that there will be less human-wildlife conflict and more reasons for protecting the organisms of interest and/or its habitat than removing or exterminating them, if it is seen positively. But having this positive image is only good until it starts to backfire and ironically cause more harm upon the organism, as evident from the involvement of T. lymma in the aquarium trade. The important conservation message here then is that charismatic creatures such as T. lymma are most beautiful when free to roam about in their natural habitats, not when they are kept in captivity whiile their natural habitats get destroyed by human activities.

A Common Mix-up

Notice how so far, we have been using the scientific name (T. lymma) rather than the common name (blue-spotted stingray) when referring to this species of interest? Well, that is because this species goes by several common names, both English and non-English

 (Fig. 3) and the scientific name is the most straightforward and unambiguous way of referring to this species. The following figure presents some of the common names of T. lymma in selected languages used within the region it can be found in (read more about Geographical Range and Distribution).

Fig. 3. Common names in selected languages

From one glance, it is easy to see how the common name of this species came about. 1) It is a stingray. 2) It has blue spots (read more about Distinctive Features). It makes sense for easier general communication if it was the only stingray with blue spots but guess what? There is another stingray species called Neotrygon kuhlii which also has blue spots and is, coincidentally, also known commonly as the blue-spotted (sting)ray (see the names in red) or Kuhl’s stingray

 . Not to mention that this second species also tends to occupy the same kind of habitat - inshore over coral reefs

 (read more about Habitat) - which further complicates things. Hence, scientists have devised a standardized naming system with vigorous rules to avoid such confusion. For more information on how scientific names work, check out this page. Having said all that, for the rest of this page, we will continue to use the scientific names of species.

DID YOU KNOW?
All of this mix-up seems to originate from two main things. On one hand, we have N. kuhlii, which is found almost everywhere in the world except the Red Sea and is commonly called the “blue-spotted (sting)ray”. On the other hand, T. lymma, which is actually found in the Red Sea and referred to as the “blue-spotted fantail/ribbiontail ray” everywhere else, is known by locals near the Red Sea as *the* “blue-spotted (sting)ray” since it is the only stingray that locals have seen in the region

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A New Discovery!!!

Considering how recognizable and popular T. lymma is, it is reasonable to think that there would not be an surprises left in store for us but... we were wrong. In fact, just earlier this year in 2016, researchers have split the existing T. lymma species into two separate species, with the newly described one called Taeniura lessoni

 . In light of this, besides providing some general information on stingrays, with a focus on the species T. lymma, this page also aims to resolve part of the prevailing confusion by providing some diagnostic features that can allow one to tell T. lymma apart from species it is can be confused with such as N. kuhlii and T. lessoni (read more about Species Diagnosis and Identification). Fret not if some of the terms used get a little technical at times for explanations to these terms are provided where possible and links to the definitions of these terms are also given in cases where a short explanation is insufficient. You will also find many videos and pictures that accompany the information. The section on Taxonomy and Systematics will be the most technical section but do challenge yourself to read it to gain a better understanding of how T. lymma got its current name and more

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physical physical

Physical Description

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distinctive distinctive

Distinctive Features

Taeniura lymma is a fairly small ray with a rounded snout

 and numerous striking iridescent blue spots adorning its olive-green, dorsoventrally compressed, oval body

. The spots vary in size and generally become smaller and increase in density towards the edge of the body disc

. A pair of distinctive blue stripes also runs along each side of its tail

 which is equipped with one or two (usually two) venomous tail spines near the end of the tail (Fig. 6)

.This is contrary to the popular belief that tail spines are located at the end of the tail. Overall, its brightly-coloured skin serves as a warning to other animals that it Is venomous

. While some individuals off Southern Africa have been found to lack the blue stripes on the tail

, it has been recently proposed that they are a new species distinct from T. lymma (read more about T. lessoni at Species Diagnosis and Identification).

Main Body

Taeniura lymma has generally smooth skin, with the exception of some small thorns scattered down the middle of its back in adults. On the dorsal side (upper side of the body), T. lymma also has large, broad spiracles which are located right behind large, bulbous eyes that are bright yellow in colour

(Fig. 9). Its pectoral fins are estimated to be approximately four-fifths as wide as it is long and its pelvic fins are narrow and angular

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Fig. 4. Dorsal view. Image by Rokus Groeneveld (Edited). Used with permission.

Its mouth, gills, nares (naris if singular) and cloaca (Fig. 8) are found on its ventral side (underside of the body), which is uniformly white in colour

.The location of the mouth makes T. lymma adapted to efficiently scoop up animals hiding in the seafloor bed while its white underside provides some camouflage against the sunny waters above when it is viewed from below (countershading)

. Between the nares, reaching past the mouth, there is also a narrow flap of skin with a fringed posterior (nearer the rear end of the stingray) margin. Meanwhile, the lower jaw dips at the middle with deep furrows at the corners of the mouth

. Within the mouth, numerous small teeth are arranged in two plates that are adapted for crushing the shells of their prey

(read more about Feeding). This crushing power is aided by their strong yet lightweight jaws which have been strengthened due to several layers of calcified cartilage supported by hollow, mineralized struts

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Fig. 5. Ventral View. Left image retrieved from the © Australian Museum (Edited). Right image by Ron DeCloux (Edited). Used with permission.

Tail and Tail Spines

Taeniura lymma has a thick, depressed tail that tapers at the end

. Measuring about 1.5 times the length of the body disc so as to allow it to strike enemies directly in front

, the tail has a low midline ridge on the dorsal surface and a broad skinfold (or fin fold) on the ventral surface that reaches the tip of the tail

. This ventral skinfold is the very structure that contributes the “ribbontail” part to one of the common names of T. lymma

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As mentioned above, the tail of T. lymma usually has one or two venomous tail spines that are located near the base of the tail. These tail spines are serrated

 with sharp barbs that face the body of the stingray

 and narrow grooves that run lengthwise along the undersides. This entire tail spine structure is then covered by a thin layer of skin that acts like a sheath

 (read more about how the tail is used for defence at Defence Mechanisms).

Fig. 6. Close-up view of tail. Image by Rob Atherton (Edited). Used with permission.

Fig. 7. Close-up view of tail spine. Pending permission.

DID YOU KNOW?
The tail spines of stingrays have been used to make weapons such as daggers

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Males versus Females

The males and females of Taeniura lymma, similar to most other stingrays and cartilaginous fish, look physically different. We describe these creatures as "sexually dimorphic". "Dimorphic" comes from the Greek words 'di-' and 'morphe' which translates to 'having two forms'

 and the term that describes this phenomenon in T. lymma is "sexual dimorphism". Sexual dimorphism in stingrays manifests in many ways, one of which is evident from size and the presence of a pair of claspers near the pelvic fin. Claspers are male anatomical structures that are used to channel semen into females via their cloaca during mating. Females are typically larger than males and as shown in the figure below, male stingrays possess claspers whereas female stingrays do not

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Fig. 8. Comparing anatomy of males and females. Image by King Bee Chen (Edited). Used with permission.

Taeniura lymma also exhibits sexual dimorphism in the electrosensory system (read more about Sensory Mechanisms) with the males possessing a significantly lower total abundance of electrosensory nerve axons compared to the females. From this, it has been suggested that the greater number of electrosensory nerve axons in females may help in improving their sensitivity, thus allowing them to differentiate between approaching their own kind and potential predators, as well as to better identify suitable males for mating (read more about Reproduction and Breeding)

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As previously mentioned, T. lymma is often confused with N. kuhlii, both of which share the common name “blue-spotted (sting)ray” and are found in similar habitats. To avoid making such a mistake, simply look out for some of the diagnostic features of each species in the figures below

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Fig. 9. Close-up comparison. Left image by Rob Atherton (Edited). Right image by Shawn M. Miller (Edited). Used with permission.

Fig. 10. Full body comparison. Left and right images by Marc Baldwin (Edited). Used with permission.

Fig. 11. Distinguishing feature of the new species. Image by Arthur Chapman (Edited). Used with permission.

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range range

Geographical Range and Distribution

Worldwide

Said to be widespread in the Indo-West Pacific region

Picture missing

Fig. 12. Global distribution. Image retrieved from Florida Museum of Natural History. Used with permission.

Singapore

Taeniura lymma is often encountered by divers and can be spotted (no pun intended) on sandy areas or near coral reefs on some of our shores. They have been encountered at the Southern Islands of Singapore such as Saint John’s Island and Sisters’ Island and even at Tanah Merah and Pulau Semakau

For more pictures of T. lymma found in Singapore, check out WildSingapore’s webpage here.

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habitat habitat

Habitat

Taeniura lymma is a bottom-dwelling species

Adults and juvenile rays are found to occupy dissimilar habitats, with the adults in cool deeper reef environments, and the juveniles in warm, shallow intertidal seagrass, mangal or rocky shoreline habitats

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Biology and Ecology

General Behaviour

A shy creature that swims away when approached by divers

Just a word of caution… despite the fact that the stingrays in the video typically flee before having their tails grabbed (from behind and not from the front), do not, under any circumstances, attempt what was done in the video. It goes without saying that if a stingray happens to be startled by a human stepping on them, it will not hesitate to use its tail spines so be careful of where you step (read more about how a stingray actually utilizes its tail spines at Defence Mechanisms).

DID YOU KNOW?
Interestingly, T. lymma has been observed soliciting cleanings from shrimp and tiny fish such as the bluestreak cleaner wrasse (Labroides dimidiatus). How do they do it? They simply head to ‘cleaning stations’ and raise the margins of their disc and pelvic fins 

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feeding feeding

Feeding

Taeniura lymma are predators in benthic habitats within their range, feeding on molluscs, polychaete worms, shrimps, crabs and small fishes

DID YOU KNOW? Foraging T. lymma are often followed by other fish, such as the goatfish, that are ready to capture any prey missed by the ray

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predators predators

Predators and Parasites

Hammerhead sharks and bottlenose dolphins are known predators of T. lymma, with other large fish, such as sharks, and marine mammals as potential predators

Taeniura lymma is also host to various parasites which include tapeworms, flatworms, nematodes, copepods and protozoans

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reproduction reproduction

Reproduction and Breeding

Taeniura lymma, similar to other stingrays, have an (aplacental) ovoviviparous mode of reproduction. This means that female rays give birth to live offspring that have hatched from egg cases within the body

During development, the embryos are initially sustained by yolk after which, as they continue to develop and deplete the yolk sac, they receive additional nourishment in the form of histotroph or “uterine milk” (enriched with mucus, fat and proteins) produced by the mother

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defence defence

Defence Mechanisms

It is common knowledge that T. lymma, as a stingray, defends itself using its tail spines and that the two main things that cause the resulting pain are the barbs on the tail spines and the venom that the stingray injects into its victim. But how does a stingray attack? The process is actually pretty simple. The stingray has to first face the victim then all it has to do is to flip its long tail upward and over its body to strike the victim in front

 . If you like, you can watch the video below from 1:23 to 2:26.

The venom may not be fatal but it causes excruciating pain for the victim. It consists of the enzymes 5-nucleotidase and phosphodiesterase which essentially cause tissue and cell death, as well as the neurotransmitter serotonin, which causes the severe contraction of smooth muscle. It is the latter that makes the venom especially painful. Fortunately, if the venom is released into an area like the ankle, the wound can usually be treated with the help of heat. Applying heat breaks down the venom and limits the amount of damage it can render. However, in the worst-case scenario, if the wound is not treated in time, amputation might still be necessary

Locomotion

In order to generate thrust while keeping their dorsoventrally compressed body mostly rigid

 , T. lymma exhibits undulatory (wave-like) locomotion in which undulatory waves are propagated down their pectoral fins from the anterior end (nearer the head end of the stingray) to the posterior end (nearer the rear end of the stingray) 

 . To move backwards, all it has to do is to simply reverse the direction of the wave propagation 

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Taeniura lymma also possess fin muscles that are found throughout the entire length of the pectoral fin and all of them are typically active, except at lower speeds when there is no need for propulsion through the water

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sensory sensory

Sensory Mechanisms

Ever wondered how stingrays like T. lymma are able to sense their surroundings or even know where to find their prey if their eyes are on the dorsal side while their mouths are on the ventral side? Well, they rely on electroreception to detect prey, navigate and communicate. This is achieved with the help of their peripheral electrosensory system which comprises hundreds to thousands of separate electrosensitive units called the ampullae of Lorenzini, which are tightly grouped into distinct subepidermal clusters. Each of these clusters is linked to an individual pore on the skin via a long canal that is filled with an electrically conductive gel (Fig. 14)

Fig. 14. Image retrieved from Kempster, et al., 2013 [13] (Edited).

Within each individual ampulla, sensory receptor cells line the epithelial wall and these cells have the ability to detect electrical potential differences between the apical side of the gel-filled canal and the basal side of the sensory receptor cell outside the ampulla. These cells allow each ampulla to detect and transduce weak electric fields into electrical impulses which can then be recognized by the nerves of the central nervous system

For T. lymma, very few electrosensory pores are located on the dorsal side. The majority of them are found on the ventral side of the body instead, concentrated particularly around the mouth. In terms of adaption, this arrangement makes sense since it would facilitate and enhance detection of prey

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taxo taxo

Taxonomy and Systematics

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hierarchy hierarchy

Taxonomic Hierarchy

Information retrieved from: Integrated Taxonomic Information System (ITIS) and Skates and Rays of Atlantic Canada.
The WoRMS (World Register of Marine Species) taxon tree for the blue-spotted fantail ray can be found here.

Historical Background

The blue-spotted fantail ray, while now known as Taeniura lymma, was not always named as such. The earliest record shows that it was originally described as Raja lymma by Swedish naturalist Peter Simon Forsskål in 1775

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Fig. 14. Original description. Image retrieved from the Biodiversity Heritage Library (Edited). Click on image to view the full record at Biodiversity Heritage Library.

DID YOU KNOW?
Interestingly, while T. lymma today fall under the class Chondrichthyes for cartilaginous fish, they were actually originally placed under the class Amphibia

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It is important to note, however, that sources have inaccurately cited the original description to be in the book Descriptiones animalium quae in itinere ad maris australis terras per annos 1772, 1773, et 1774 suscepto collegit, observavit, et delineavit Joannes Reinlioldus Forster, etc., curante Henrico Lichtenstein. An example is shown in the figure below.

Fig. 15. Inaccurate information. Image retrieved from World Heritage Encyclopedia™

In past scientific literature, the blue-spotted fantail ray also went by the name Trygon ornatus after being documented by British zoologist John Edward Gray in 1830

 , an illustration of T. lymma was included.

Fig. 16. Illustration by John Edward Gray. Image retrieved from the Biodiversity Heritage Library (Edited). Click on image to view the full record at Biodiversity Heritage Library.

However, as the naming of species works on the Principle of Priority, what Gray had done was to erroneously re-describe a species that already had an assigned species name. Hence, since Trygon ornatus (1830) came after Raja lymma (1775), the former name is now known as a junior synonym. But that is not the end of the story... In 1837, German biologists Johannes Peter Müller and Friedrich Gustav Jakob Henle created the genus Taeniura

 that is said to mean ‘dirt’. No type specimen was designated by Forsskål

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Higher Level Classification

The family Dasyatidae (Order Myliobatiformes) is one of the biggest families of batoid fishes, and the members within this family have a body that is “characterized by a large, oval, circular or rhomboidal disc usually covered with denticles, thorns and tubercles on the dorsal surface and sometimes on the tail”. However, given the large number of species described in the family Dasyatidae as well as taxonomic uncertainties, the classification and status of some species are still subject to change, especially at the family level (read more about Taxonomic Hierarchy)

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Phylogeny and Morphology

There are many taxonomic issues within rays, including the family Dasyatidae. Recently, these issues have become even more contentious based on studies that were conducted just two to three years ago. In fact, the discovery of the new species T. lessoni this year is just the tip of the iceberg. Within the genus Taeniura itself, there are issues of species placement. While some taxonomic sources recognize three species in the genus Taeniura (note that back then, T. lessoni was not discovered yet), others have removed the species T. grabata and T. meyeni and placed them in the genus Taeniurops instead

 . Of course, this means that T. lymma was the sole member of the genus for a while until T. lessoni came along (read more about T. lessoni at Species Diagnosis and Identification).

A study that proposed such a change in species placement was one that was conducted by Lim et al. (2015) with the following aims

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1. Elucidate the phylogenetic relationships of stingrays in the family Dasyatidae using COI, ND2 and RAG1 genes
2. Re-examine the morphological characters used by Last et al. (2010) for species differentiation in the book “Sharks and Rays of Borneo” (Collingwood: CSIRO Marine and Atmospheric Research)

This was the first time these genes (or even any other genes for that matter) were successfully studied at the family level for rays and based on the results, it was suggested that the current family Dasyatidae is non-monophyletic and should be split, instead, into four different families – Neotrygonidae, Himanturidae, Pastinachidae and Dasyatidae – including itself. The results that they obtained are summarized in the respective trees below. Note that for the RAG1 gene, a cladogram was generated instead as the short distances among the taxa resulted in a crowded phylogenetic tree

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Fig. 17. Trees for the COI, ND2 and RAG1 genes respectively. Image retrieved from Lim,et al., 2015 [22] (Edited). Click on image to view the enlarged trees.

It would be most ideal if a summarized tree using all three of the genes was generated. However, this was not done so in the study proposed by Lim et. al (2015). Nevertheless, all of the trees show that the Dasyatidae family (boxed up in green) is not monophyletic, forming four clades for the COI and RAG1 genes and two main clades (each with two subclades) for the ND2 gene. Hence, in order to maintain monophyly, the researchers proposed the following changes in classification in their discussion

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• Elevation of the three clusters to family level (three new families)
• Retain original Dasyatidae family (Dasyatis and Taeniurops spp.)
• 1st new family: Neotrygonidae (Neotrygon spp. and Taeniura lymma)
• 2nd new family: Himanturidae (Himantura spp.)
• 3rd new family: Pastinachidae (Pastinachus spp.)

It is interesting to note that after resolving the problem of non-monophyly, members of the order Myliobatiformes could be accurately and correctly classified into their respective families based on morphology, using nine character measurements that have been identified as useful morphological information and removing previously used characters that caused incertae sedis (uncertain placements) and/or past misclassifications

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These characters are relative total length (TL), disc length (DL), tail width (TW), tail height (TH), eye diameter (ED), spiracle length (SPL), interspiracular length (ISL), distance between fifth gill slits (I5) and ventral tail fold length (VFL). These were the findings observed[24]:

• Neotrygonidae are separated from the other families by their relatively large ED
• Himanturidae have no fin fold and the longest DL
• Pastinachidae are separated from the rest by their relatively longer VFL

Genetic Sequences

In early 2015, the complete mitogenome of T. lymma was also sequenced and it was found to be 17,652 basepairs long (GenBank accession number: KM881715), containing 37 mitochondrial genes and a non-coding AT-rich region of 1906 basepairs in length. The base composition of the T. lymma mitogenome is A: 32.09%, T: 27.04%, G: 13.00% and C: 27.87%. Mitogenome comparisons indicate has a closer relationship between T. lymma and N. kuhlii (88%) than between T. lymma and T. meyeni (85%). This is consistent with previous analyses done based on the mitochondrial COI and 16S genes and the nuclear RAG1 markers, as well as the aforementioned phylogenetic study by Lim et al. (2015). Given the many unresolved questions with regards to the taxonomic boundaries in rays, the mitogenomic information for Taeniura will be a useful molecular resource for future studies

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A representative barcode sequence (the centroid of all available sequences) for T. lymma is shown below.

Fig. 18. DNA Barcode. Image retrieved from Encyclopedia of Life.

Beyond This Page

External Links

Animal Diversity Web
ARKive
The Elasmodiver Shark and Ray Field Guide
Encyclopedia of Life
Florida Museum of Natural History
A Guide to Common Marine Fishes of Singapore
IUCN Red List
MarineBio
Wild Fact Sheets (Wild Singapore)

References

This page was authored by Shelley Chan Hiang Ming

Last curated in 2016