Blood-feeding. Move actively, able to swim. Detect and orient towards hosts by aquatic vibrations resulted from hosts into the water.
This species can be easily recognized by the five longitudinal, usually black-bordered yellowish stripes, in which the mid-dorsal one is most conspicuous on the greenish or olive dorsum with the marginal yellow stripes and the pale yellowish venter without any spots. However, notice the head of this species is about broad as the body, rather than attenuated and sharp as in Whitmania species.
Body length 30–60 mm, maximum body width 4.0–8.5 mm, anterior sucker diameter 2.0–4.5 mm, posterior sucker diameter 3.0–5.5 mm. Body elongated, dorsal-ventrally flattened and thick, with dorsum moderately arched and venter flat. Head broad, round, anterior sucker wide, oval shape, venter of lip with a deep median fissure. Posterior sucker circular, diameter from two-thirds to about the same as maximum body width.
Dorsum flat, with three pairs of paramedian, intermediate and supramarginal lines of obscure, translucent-tipped sensillae. Venter flat, with sensillae flattened and more obscure than dorsum. Dorsum of posterior sucker flat, with scattered sensillae. Venter of posterior sucker flat or indented with thickened rim and flattened radiating ridges.
When alive, Dorsum greenish, olive, or brownish with five longitudinal, narrow, often bordered and broken, yellowish stripes. The median one most conspicuous and rarely absent, while the other four thinner and sometimes obscure or missing, and leaving the black border as four narrow broken lines in each side. Body margin with a yellow longitudinal stripe in each side. Venter uniform, pale yellowish, with no spots or stripes. Dorsum of posterior sucker with the same color as dorsum and a wide stripe extended from the mid-dorsal one on the dorsum. Venter of posterior sucker the same color as ventral body, with no spots.
Eyes five pairs, punctiform, arranging respectively at II (2nd annulus), III (3rd annulus), IV (4th annulus), V (6th annulus) and VI (9th annulus) in parabolic arc.
One hundred and two annuli. I, II and III uniannulate. IV biannulate ((a1a2)>a3). V biannulate dorsally ((a1a2)>a3) and uniannulate ventrally. VI triannulate with the three annuli equal dorsally and biannulate in a1a2 & a3 ventrally. VII triannulate (a1<a2<a3). VIII quadrannulate (a1>a2>b5=b6). IX–XXIII midbody somite and quinquannulate, with the five annuli of the same length. XXIV quadrannulate with the four annuli of the same length. XXV triannulate. XXVI biannulate. XXVII uniannulate. Anus in the middle of XXVII (102nd annulus). Gonopores separated by five annuli; male at XI b5/b6 (31st/32nd annulus); female at XII b5/b6 (36th/37th annulus); both transverse slits strictly within furrows.
Jaws three, crescent shaped, large and thick, with 55-70 teeth; one mid-dorsally, the other paired ones ventro-laterally, all in deep buccal chamber beyond the velum. Pharynx in VII–IX, moderately narrow, with six spongy ridges in which three continuous with the three jaws and the other three intermediately between the formers, surrounded by numerous unicellular salivary glands. Crop in X–XIX, with 10 pairs of bi-lobed caeca in X–XIX. The first nine pairs of caeca lateral, while the last pair large, wide, and elongated posteriorly to XXIV and lateral to intestine; the first pair usually small and indistinct, the rest of each pair of caeca larger than the former one. Intestine in XIX–XXIV, no caeca, with flexure and ventral to rectum in XXIV. Rectum short, tapered towards anus.
Ten pairs of testisacs at XIII/XIV–XXII/XXIII. Vas deferens entered epididymis in XI/XII. Epididymis in XI, large, round-convoluted, thick, massive, and lateral to the atrium and penis sheath. Ejaculatory bulbs muscular, large, elongated ellipsoid, tapered inwards into the side of the atrium and connected by slender ejaculatory ducts to atrium in XI. Atrium in XI, large, conspicuous, bulbed; with a thick layer of prostate gland surrounding the wide anterior part, rising well dorsad of the level of the nerve cord passing along in the left side, and led posteriorly into the anteriorly-bent penis sheath near XII. Ovisacs in XII posteriorly, moderately small, connected with long and curled common oviduct in XII before the covering thick oviducal gland. Vaginal sac in XII–XIII/XIV, long, fusiform, with short and thick vaginal stalk extended anteriorly into female gonopore in XII.
Hirudo nipponia is similar to Whitmania leeches, such as W. laevis and W. acranulata, in the external color pattern of five longitudinal yellowish stripes. The head shape is a good character to distinguish between these species. Head shape of H. nipponia is wide and round, with the width about the same as or slightly less than the maximum body width. On the contrary, head of Whitmania leeches is attenuated and the head width is much less than half, even only one-third of the maximum body width. In addition, the color pattern of the venter can be an additional identifying key for that there is no spot or stripe on the venter of H. nipponia, while there are two marginal spotted lines on the venter of both W. laevis and W. acranulata and many spots scattered on the venter of W. laevis.
Although H. nipponia mainly takes blood from amphibians, reptiles and mammals, it may also attacks teleost fishes. However, it has never been reported that H. nipponia take blood from any birds. In addition, it has been reported that H. nipponia attack other same-sized or larger leeches, whether predacious species or blood-feeding ones, and feed on the body fluid of predacious leech host or the blood in the digestive tract taken earlier by the blood-feeding leech host. Such leech hosts usually die after being parasitized by H. nipponia.
According to Takahashi, H. nipponia was common mainly in the south island and was rarely found in the east and north island in 1930s. Keegan et al also mentioned that H. nipponia was found in large numbers at several low-elevation localities and was common in rice paddies, ponds, slow streams, drainage ditches and open sewers in the central and southern portions of the island. Comparing the past records of localities where H. nipponia was collected, we assumed that before 1960s, this species was common in central and south Taiwan, should be relatively rare in north Taiwan, and its rarely distributing in east Taiwan in 1930s was probably due to the inconvenient transportation for naturalists in the east island. However, in spite of the common records in the past, H. nipponia, as well as other aquatic blood-feeding leeches, has disappeared from the rice paddies and drainage ditches around the island, and has been hardly found in ponds, slow streams, and open sewers in these decades. We suggested that the use of insecticides, herbicides and fertilizers may be the main reason of the disappearance because it has been reported by Yang that these chemicals are able to kill H. nipponia in China. The organic pollution in the low-elevation aquatic environment in Taiwan may also reduce the population of aquatic blood-feeding leeches as H. nipponia and Hirudinaria manillensis, for that H. nipponia is not able to survive in highly-polluted aquatic environment.
PREY OR HOST
Amphibians, reptiles and mammals, including human.
In the world, this species is recorded in East Asia, including Far East district in Russian, Japan, Korea, China, Mongolia, Ryukyu Islands and Taiwan. In Taiwan, it was recorded in large numbers at several low-elevation localities in Taichung, Nantou, Chiayi, Tainan, Kaohsiung, Pingtung, Hualien and Taitung. However, recently this species has been found only in a mountain lake in the Yilan area.
Rice paddies, irrigation ditches, ponds, slow streams, drainage ditches and open sewers.