Fine-toothed saw

For the first time, the species was scientifically described by John Latham in 1794 on the basis of the rostrum ^[6] . The described sample was destroyed during a fire at the Museum of the Royal College of Surgeons of England ^[7] . Species epithet comes from the words lat. micro - "small" and others. Greek. ὀδούς - “tooth” and is due to the fact that this species has a rather short rostrum compared to other sawmills ^[7] .

Stingrays belonging to the genus saws are conventionally divided into two groups with large and small teeth "saws". Saws with small teeth form a complex of Pristis pectinata species ( P. clavata , P. pectinata and P. zijsron ), and with large teeth, they form the Pristis pristis complex ( P. microdon , P. perotteti and P. pristis ), which needs further taxonomic studies . Pylar saws with small teeth are probably not separate species, but subspecies or representatives of subpopulations of the same species of global distribution. The existence of three main treasures (the Atlantic, Indo-Pacific and East Pacific) has been genetically proven, but they do not correspond to the current ranges of sawfly species belonging to the group with small teeth ^[8] . The International Union for Conservation of Nature has deleted the profile of the small-toothed saw tree, combining it with the profile of the European saw tree , since according to the latest data these species are synonymous ^[5] .

Small-toothed sawflies live in the tropical and subtropical waters of the Indo-Pacific region. Distributed off the east coast of Africa , starting from Durban . They are found off the coast of Madagascar , Pakistan , India , Thailand , Indonesia , Vietnam , the Philippines , in the South China Sea , in the waters of Australia (from Western Australia to the northern Territory and Queensland ), Borneo and Papua New Guinea , Indonesia . They enter the estuaries and fresh waters of the rivers: Zambezi , Mahanadi (Iniya, 64.4 km upstream), Chauphray (Thailand, 62 km), Mekong (Vietnam), Fly and Lake Marri (Papua New Guinea) and rivers flowing in the Northern Territory (Australia) ^[7] .

The fine-tooth saws are kept in shallow water. In northern Australia, during the rainy season from December to March, they prefer to stay in fresh water, and in drought they move to coastal sea bays and estuaries. In Australia, these stingrays share their habitat with blunt sharks. Adult individuals, at least seasonally, go to the open sea ^[7] .

The maximum recorded length is 7 meters, and the maximum mass is about 600 kilograms ^[4] . The elongated flat rostrum of the small-toothed sawmill on both sides is dotted with tooth-like outgrowths. It is covered with electroreceptors , catching the slightest movement of potential prey buried at the bottom. The teeth are firmly and deeply fixed in the hard cartilaginous tissue and do not grow back when they are damaged. A long lamellar snout, gradually narrowing from the base to the end, has from 14 to 22 pairs of teeth on each side (usually 18–20), and the distance between two teeth increases from the tip of the snout to the base ^{[7] [9]} . The first pair of teeth is located at the base of a wide and strongly tapering toward the end of the rostrum. The number of teeth on different sides may differ, as a rule, there are more teeth on the left. In two independently conducted studies, it was found that in males and females the number of teeth is also different. Regardless of the geographical area, males had an average of 20.9 teeth on each side, and females had 18.9 teeth. In general, males have a slightly longer rostrum than females. In fine-tooth sawlogs, large teeth are comparable in size only with the teeth of Atlantic sawflies ^[7] .

The body is long and slightly flattened. The mouth, nostrils and gill slits, like other stingrays, are located on the ventral surface of the body. There are small teeth in the mouth. Behind small eyes there are sprinklers that pump water through the gills and allow the slopes to lie motionless at the bottom. There are 2 rather large dorsal fins of approximately the same size, broad pectoral fins and inferior in size to them ventral fins of a triangular shape, a caudal fin with a developed upper and small lower lobes. Anal fin missing. The skin is densely covered with small placoid scales ^[10] . Each flake is covered with ridges, which are less noticeable in larger individuals. The dorsal surface of the body is yellow-gray, the fins have a yellow-brown fringing, the ventral surface of the body is dirty cream. The rostral teeth are painted in a dirty cream or yellow color and contrast with a darker shade of rostrum. In the mouth there are small rounded teeth assembled in rows, on the upper jaw there are 70–72 rows of 115–127 teeth, and on the lower 64–68, 122–140 teeth ^[7] .

From Asian saws, in which the teeth of the rostrum are in the form of blades, the fine-tooth saws differ in pointed teeth, as well as in the less developed lower lobe of the caudal fin. They are distinguished from the Queensland sawfish by the relatively first forward dorsal fin, the presence of the lower lobe of the caudal fin, and also their large size. The main differences between the small-toothed sawmill and the comb and green one are a wider and flatter rostrum, fewer pairs of rostral teeth (14–22 versus 20–34 and 23–37, respectively), the presence of the lower lobe of the caudal fin and the position of the base of the dorsal fin (in front of the base of the ventral fins) ) They also differ from the comb sawlogs with a more stocky body and a greater width of the pectoral fins. There are no external differences between the small-toothed and European sawmills, they have only different ranges, perhaps these species are synonymous ^[7] .

Small-toothed sawfish are bottom fish that feed on crustaceans, mollusks, and small fish. Using a snout in search of food, they dig up the ground, injure their victim, and also defend themselves from enemies, which in the natural environment are sharks, for example, blunt-nosed, and combed crocodiles ^[7] . Their "saw" is dotted with electroreceptors, helping to detect prey in troubled waters ^[10] .

Like other pyloric skates, small-toothed pyloryls reproduce by egg-production. Fertilization is internal, embryos develop in the womb and feed on the yolk . These stingrays grow slowly and mature, they have a small offspring. In litter up to 10 and more newborns 72–93 cm long with an already formed but soft snout. Their teeth are coated and reach their final size in relation to the rostrum only after childbirth. Pregnancy lasts about 5 months. Childbirth occurs including in fresh water. The breeding cycle is probably one year old. Males and females reach puberty at a length of 250 and 300 cm, respectively ^[7] .

The length of three sexually mature males caught in the waters of Durban ranged from 3.75-3.92 m, and the weight of 180-188 kg. During the study, a one-year-old individual, 91.2 cm long, a 2-year-old male, 1 m long, a three-year-old male and a 1.6-meter-long female and 4–5-year-old individuals of both sexes, a 2.1–2-long, were caught off the coast of Western Australia , 3 m. In 2004, a 2.2 m long female was tagged and released in the Fitzroy River. After 5 months, she was caught and remeasured. The growth during this time was 30 mm. In the waters of Papua New Guinea, a 3.6 m long fine-toothed sawfly was caught, whose age was estimated at 44 years based on the vertebral structure, while an immature male 2.5 m long was approximately 16 years old ^[7] .

On the small- tooth pyloric parasites, the monogenies Dermopristis paradoxus ^[11] , Nonacotyle pristis and Pristonchocotyle papuensis ^[12] , Cestodes Pterobothrium fragile ^[13] , Nematodes Terranova pristis ^[14], and copepods Caligus furcisetifer ^{[15] are} parasitic . ^[12] .

Contrary to myths, small-toothed sawflies are not dangerous to humans. However, given the large size and sharp teeth of the rostrum, caution should be exercised with these fish ^[16] .

Sawmills have long been the subject of commercial fishing. The meat of these fish, especially the fins, which are an ingredient in the famous soup , is much appreciated ^[17] . Liver fat is used in folk medicine. The price for the rostrum can reach $ 1000 or more ^[18] . Serrated rostrum makes them very vulnerable - they can get entangled in nets and garbage floating in the water. The International Union for Conservation of Nature has deleted a separate profile of the fine-toothed sawlog, combining it with the profile of the European sawlog, which has the status of “On the brink of extinction” due to the deterioration of the ecological situation and overfishing . Since 2007, the sale of all types of sawing rays, including their fins, meat, organs, skin, rostrum and rostral teeth, has been banned ^[19] . Despite this, poaching continues to threaten the existence of these fish. Representatives of this species are quite common in public aquariums, however, as a rule, they have not lived for more than 7 years ^[20] .

• Animal life . Volume 4. Lancelet. Cyclostomes. Cartilaginous fish. Bone fish / ed. T. S. Rassa , ch. ed. V. E. Sokolov . - 2nd ed. - M .: Education, 1983 .-- S. 54 .-- 300,000 copies.
• Fowler, SL, Cavanagh, RD, Camhi, M., Burgess, GH, Cailliet, GM, Fordham, SV, Simpfendorfer, CA and Musick, JA Sharks, Rays And Chimaeras: The Status of the Chondrichthyan Fishes. - Switzerland and Cambridge, UK: IUCN SSC Shark Specialist Group, IUCN, Gland, 2005.

• Fine-Toothed Sawmill (Eng.) In the FishBase Database.
• Species Fine-toothed sawfish (Eng.) In the World Register of Marine Species .
• Fourteenth Meeting of the Conference of the Parties, Proposal 17: Inclusion of the Sawfish family Pristidae in Appendix I (unopened) (link not available) . CITES (January, 2008). Date of treatment October 20, 2015. Archived January 11, 2014.