Ozobranchus jantseanus
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Ozobranchus jantseanus |
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| Scientific name | ||||||||||||
| Ozobranchus jantseanus | ||||||||||||
| Oka , 1912 |
Ozobranchus jantseanus is a species of leeches (Hirudinea) that parasitizes on freshwater turtles in China and Japan. Experiments have shown that the animals are able to survive extreme temperatures and freezing in liquid nitrogen.
features
Ozobranchus jantseanus reaches a body length of 2.2 to 7.0 millimeters and a maximum diameter of 1.2 to 3.0 millimeters. The animal used for the first description was 9 millimeters long and had a maximum diameter of 2 millimeters. The body is brightly colored and has conspicuous fringes on the sides, which consist of 11 paired and continuously equal-sized tufts of gills . This distinguishes it from Ozobranchus margoi with 5 and Ozobranchus branchiatus with 7 paired gill tufts.
The body consists of two distinctly different regions, a head and neck area and the torso area. The head and neck are not clearly separated and consist of 18 rings, with the first 3 rings on the ventral side forming the mouth suction cup of the leech. The second ring has a pair of point eyes on the front edge on both sides of the middle. Shortly before the transition to the trunk area, the male and female genital openings are located on the abdomen, the distance between them being less than a ring width. The fuselage consists of 27 rings, with 11 wider and narrower rings alternating and at the end there are 5 rings that decrease in size. On the belly side, the wider and narrower rings are fused together. The wide rings each have a gill tuft on their sides, which consists of a short basal piece, which then splits into two branches and later into five to seven gill threads. These gill tufts are all the same size, while in other species of the genus they decrease in size towards the rear and are more like those of the genus Branchellion .
At the end of the fuselage, the rear suction cup connects to the narrowing formed by the smaller rings. The diameter of the suction cup corresponds roughly to the width of the trunk with a maximum of 2 millimeters.
distribution
The distribution area of Ozobranchus jantseanus covers parts of East Asia and is tied to the occurrence of the host freshwater turtles. It was originally described from Wuchang , now a district of the city of Wuhan in the People's Republic of China , and it is best known from Japan .
Way of life
Ozobranchus jantseanus lives as an ectoparasite on several species of freshwater turtles in Japan. The flukes have been identified primarily for the two species Chinemys reevesii and Mauremys japonica , and in 2012 it was also found in the red- eared slider turtle ( Trachemys scripta elegans ) introduced in Japan . Other species of the genus, however, occur exclusively on marine turtles.
On the turtles it settles mainly in the softer areas of the skin folds between the belly and back armor ( plastron and carapace ), and it also lives in the eye sockets or within the turtle shell. In the case of a red-eared slider turtle, animals have also been detected in the mouth, which probably entered through an injury to the beak.
The eggs are laid in balls that are attached to the back armor, but this could not be proven for the infestation on the red-eared slider turtle. From here the juvenile stages of the leech pass over to the eggs of the turtles and the leeches remain on the host animals throughout life.
Investigations of the leech showed that it can survive even under extreme cold conditions and that it is capable of cryobiosis . It can withstand freezing and thawing and even survive freezing in liquid nitrogen at a temperature of −196 ° C for a period of 24 hours. It survives freezing at −90 ° C for a period of up to 32 months and it can also survive repeated, cyclical freezing to −100 ° C and thawing to 20 ° C. This shows a tolerance to extreme temperatures that has not yet been proven in other leeches. For other organisms too, including tardigrade or fly larvae ( Chymomyza costata ), only lower survival rates could be demonstrated in shorter-term experiments. Signs of anhydrobiosis (dehydration before freezing) or the production of trehalose or glycerine as antifreeze could not be detected in the leech and it is assumed that it retains water in the cells even when frozen.
Long-term freezing survival rate of Ozobranchus jantseanus
Ozobranchus jantseanus survival rate with repeated freezing
Survival rates of different species of leeches at −90 ° C and −196 ° C
Since the turtles and therefore also the leeches are more often exposed to temperatures of 0 ° C and below, a general cold tolerance of the leeches makes sense, but in their natural habitat they are never exposed to the extreme conditions of the experiments.
Systematics
Ozobranchus jantseanus is classified as an independent species of the genus Ozobranchus within the Ozobranchidae . All seven known species of the genus live ectoparasitic on turtles. The first description of Ozobranchus jantseanus was made in 1912 by the Japanese zoologists Asajiro Oka from a single individual, which he by a colleague from Wuchang in China, now a suburb of the city of Wuhan , province Hubei , the Yangtze River , after which it is named, received.
supporting documents
- ↑ a b c d Takeo Yamauschi, Tomoko Nishibori, Dai Suzuki: First Report of Ozobranchus jantseanus (Hirudinida: Ozobranchidae) Parasitizing the Exotic Red-Eared Slider Trachemys scripta elegans in Japan. Comparative Parasitology 79 (2), 2012; Pp. 348-349; doi : 10.1654 / 4553.1
- ↑ a b c d e f g Asajiro Oka: A new Ozobranchus species from China. (Oz. Jantseanus n. Sp.). Annotationes Zoologicae Japonenses 8 (1), 1912; Pp. 1-4; ( Literature entry at Zoobank ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. )
- ↑ a b c d Takeo Yamauschi, Dai Suzuki: Geographical distribution of Ozobranchus jantseanus (Annelida: Hirudinida: Ozobranchidae) in Japan. Medical entomology and zoology 59 (4), 2008; Pp. 345-349; ( Full text ( Memento of the original from February 22, 2014 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this note. )
- ↑ a b c d Dai Suzuki, Tomoko Miyamoto, Takahiro Kikawada, Manabu Watanabe, Toru Suzuki: A Leech Capable of Surviving Exposure to Extremely Low Temperatures. PLoS ONE 9 (1), e86807, January 22, 2014; Pp. 348-349; doi : 10.1371 / journal.pone.0086807
