If you want to learn more about how the charismatic creatures known as stingrays feed, you should check out a new study published in the most recent issue of Neotropical Ichthyology.

While spending days and nights scuba diving and snorkelling in the upper Paraná River of Brazil, researchers Domingos Garrone-Neto and Ivan Sazima made 132 observations of freshwater stingrays and noticed three different forms of foraging behaviour.

Picture of Motoro Sting Ray, Ocellate river stingray – Potamotrygon motoro.
Copyright www.jjphoto.dk

The first hunting technique involved hovering close to the bottom, or even settle on top of it, while undulating the disc margins. By doing so, the stingray would stir up the substrate, unveiling small invertebrates. The invertebrates – typically snails, crabs and larval insects – could not escape from under the ray’s disc and ended up as food.

When using its second hunting technique, the stingray would slowly approach shallow water while keeping its eyes on suitable prey items that concentrate in such environments. When it got close enough, it would make a rapid attack; stunning the prey or trapping it under its disc. This hunting technique did not target tiny invertebrates hiding in the sand; it focused on tetras and freshwater shrimps instead. The studied stingrays only used this method during the night when they could sneak up on prey without being seen.

The third technique observed relied on the presence of vertical or inclined surfaces in the water, such as boulders and tree stumps, including man-made structures like concrete slabs. On this type of objects a lot of different organisms, e.g. snails, like to crawl around or attach themselves. The hunter would simply position itself with the anterior part of its disc above the water’s edge and start picking the animals off the surface, one at a time.

The two studied species were Potamotrygon falkneri and Potamotrygon motoro; both belonging to a genus of freshwater stingrays found exclusively in South America.

As mentioned above, you can find the paper in Neotropical Ichthyology 7.

Garrone-Neto, D and I Sazima (2009) Stirring, charging, and picking:

hunting tactics of potamotrygonid rays in the upper Paraná River. Neotropical Ichthyology 7, pp. 113–116.

Chinese ichthyologists Yang, Chen and Yang have described three new species of snow trout in a paper[1] published in the journal Zootaxa[2]. All three species have been described from material previously identified as one single species, Schizothorax griseus. True trouts belong to the Salmoninae subfamily in the Salmonidae family, but snow trouts are members of the family Cyprinidae.

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Schizothorax

New species: Schizothorax beipanensis

Schizothorax heterophysallidos

Schizothorax nudiventris

Schizothorax beipanensis

Schizothorax beipanensis is found in southern China where it inhabits the Beipan River drainage, a part of the Pearl River drainage. It has been encountered in both slow-flowing deep pools and fast-flowing rivers with clear water and over a wide range of different bottom substrate, from mud and sand to rocks, boulders and pebbles.

Schizothorax beipanensis differs from its close relatives by having well-developed upper and lower lips (the lower lip is actually tri-lobed), no horny sheath on the lower jaw, and a continuous postlabial groove with a minute median lobe.

Schizothorax heterophysallidos

Just like Schizothorax beipanensis, the snow trout Schizothorax heterophysallidos is found in the Pearl River drainage in southern China, but it lives in the river drainage of Nanpan, not Beipan. Schizothorax heterophysallidos lives in small streams where the bottom consists of sand and pebbles.

The name heterophysallidos is derived from the unusual swim bladder of this fish; physallis is the Greek word for bladder and heteros means different. In addition to the swim bladder (the posterior chamber of the air bladder is three to six times longer than the anterior chamber), Schizothorax heterophysallidos can be recognized on its well-developed and trilobed lower lip, thin upper lip, and blunt snout. It has a continuous postlabial groove with a minute median lobe and the last unbranched dorsal-fin ray has a strong lower part. In mature specimens, the abdomen lacks scales.

Schizothorax nudiventris

Schizothorax nudiventris also lives in southern China, but in the upper parts of the Mekong River drainage. The Mekong basin is one of the richest areas of biodiversity in the world. More than 1200 species of fish have been identified here and the number is believed to increase as the area becomes more thoroughly explored by science.

Schizothorax nudiventris has a well-developed and trilobed lower lip, thin upper lip, blunt snout, and continuous postlabial groove. The body is decorated with irregular black spots on the sides, and the last one-quarter of the last unbranched dorsal-fin ray is soft. In mature specimens, the abdomen has no scales, and it is this feature that has given the fish its name nudiventris. Nudus is the Latin word for naked, while venter means abdomen.

Sri Lankan scientists have described a new species of fish from south-western Sri Lanka and placed in the genus Puntius.

Unlike its close relatives in Sri Lanka and India, the new species Puntius kelumi feature a combination of a smooth last unbranched dorsal-fin ray, a body depth that is 28.6-35.5 % of standard length (SL), maxillary barbels (about as long as the eye diameter) but no rostral barbels, 20-23 lateral-line scales on the body, and ½3/1/2½ scales in transverse line from mid-dorsum to pelvic-fin origin. One breeding males, the sides of the head and body are rough and extensively tuberculated.

Puntius kelumi is primarily found in large streams with clear water that flows down from the mountains. The bottom is typically made up by granite, pebbles and/or sand and is often littered with boulders.

The description was published by the journal Ichthyological Exploration of Freshwaters.

For more information about Puntius kelumi, see the paper: Pethiyagoda, R, A Silva, K Maduwage and M Meegaskumbura (2008) Puntius kelumi, a new species of cyprinid fish from Sri Lanka (Teleostei: Cyprinidae). Ichthyological Exploration of Freshwaters 19, pp. 201–214.

http://www.pfeil-verlag.de/04biol/pdf/ief19_3_02.pdf

A picture of the new species can be seen here

_____________________

Puntius is a genus of ray-finned fishes in the family Cyprinidae. All known members of the genus are native to Southeast Asia and India, including Sri Lanka. The name Puntius is derived from the word pungti, which is the term for small cyprinids in the Bangla (Bengali) language.

Puntius fish are commonly referred to as spotted barbs, but some species display vertical black bands instead of spots. Spotted barbs are commonly kept by aquarists and are known to be active, curious and bold. Many of them are unsuitable companions for fish with long and flowing finnage since they tend to nip such fins, a habit which causes both injury and stress in the afflicted animal.