モリミミズ

＜原記載（クリックして展開）＞

Habitate:

　　This worm has hitherto not been known from the region of North-eastern Honshu.  This worm is very swift and active, and is especially common under dead leaves in the above localities on high but not cultivated ground.  This species is commonly living under accumulated (10-14 cm thick) withered leaves of Pinus thunbergii, but other species of this genus are generally not found under such leaves.

 

External characters:

　　The size of the worms together with several other external characters based on those collected at Asamushi, are as follows: Body length 84-102 (averge 93) mm, body width at head 5-6 (5.5) mm, body width at middle 4-4.5 (4.2) mm, number of segments 73-88 (84).

　　The measurements of the body and number of segments of 18 individuals from Hirashima are as follows: body length 91-121 (103.2) mm, body width at XVIII 5.2-6.8 (5.9) mm, number of segments 67-100 (89.9).

　　As many easily be noticed from the above table, the variation found for the body length is from 91-121 mm, 103 mm in average; for the body width from 5.2-6.8 mm, 6.4 mm in average; for number of segments from 67-100, 90 in average.

　　The measurements of the body and number of segments from Kunimi-toge, are as follows; body length 74-94 (85) mm, body width at head 4-4.5 (4.2) mm, at middle 3-3.5 (3.2) mm, number of segments 79-87 (84).

　　As seen in the above tables, the worm is rather small in size.

　　The colour when the worm is alive, is fresh, somewhat with deep redish brown on the dorsal surface, milky white on the ventral surface and possesses a relatively thin skin.  On account of these characters, the dorsal blood vessels in this species can be seen very easily through semitransparent integment, especially in the prostate glands and seminal vesicles which are very well developed.  The colour of clitellum is darkish yellow and the region nearer to the clitellum is irresdescent with purple.  Altogether this is a very handsome worm.

　　The spermathecal openings are of two pairs in VI/VII and VII/VIII, and are situated in the ventro-lateral.  The pores are very conspicuous especially owing to a deep depression of body wall both in front and behind of the pores in the worm from Asamushi.  The pores are a very small wart-like process in top view, as is shown in Text-fig. 1, 1.  The general appearance of the openings is much the same as is seen with Pheretima vittata (Goto et Hatai) and Pheretima levis (Goto et Hatai).  No genital papillae are found in the neighborhood of the spermathecal openings.

　　The proportion of the intersegmental circumference where the spermathecal openings are situated to the circular distance between two spermathecal openings ventrally, is as follows; circumference VI/VII 14.4-15.9 (15.1) mm, VII/VIII 16-17 (16.4) mm, circular distance between two spermathecal openings VI/VII 7.2-8 (7.6) mm, those of VII/VIII 7.8-8.6 (8.1) mm, ratio of these two measurement 2-2.1 (2).

　　Clitellum is well developed and occupies 3 segments, XIV, XV and XVI and the female opening is located in XIV along the ventral median line.  The clitellum without setae, and intersegmental furrows, but with dorsal pores.

　　The majority of the annual species belonging to the genus Pheretima except for some rare species apparently clitellate in July or August in the Northeastern Japan, but the present species even an aclitellates at the end of September.  The proportion of the clitellate to the aclitellate specimens are given below;

　　1. Izushima, 105 specimens, all aclitellate, other genital markings apparent, September 16, 1936.

　　2. Ashijima, 165 specimens, all aclitellate, other genital markings apparent, September 17, 1936.

　　3. Hirashima, 25 aclitellate and 8 clitellate specimens, September 18, 1936.

　　4. Enoshima, 21 specimens, all aclitellate, September 18, 1936.

　　5. Tashirojima, 4 specimens, all aclitellate, September 24, 1936.

　　6. Ajishima, 11 aclitellate and 4 clitellate specimens, September 25, 1936.

　　7. Kinkazan, 75 aclitellate and 65 clitellate specimens, September 26, 1936.

　　8. Oshima, 3 aclitellate and 3 clitellate specimens, September 28, 1936.

　　The above data may be rearranged as follows: Total number 489, Number of aclitellate specimens 409, number of clitellate specimens 80.

　　Setae beginning on segment II.

　　Number of setae in some of the segments from Asamushi are as follows: omitted.

　　From the above table the following variation is recognized, for the setal number of segment V, from 46-52, 49.1 in average; on the segment VI, from 50-56, 52.1 in average; on the segment VII, from 50-63, 54.9 in average; on the segment VIII from 53-66, 57.9 in average; and on the segment XX from 57-68, with the average of 61.8.

　　The openings of male pores in segment XVIII are situated close to the lateral border on the slightly elevated oblong area and behind the setal line.  The pores are star-shape, somewhat oval-shape and prominently elevated from the body surface, and separated by 11 setae (varying from 10-12).  This setal number between the male pores is the average of 8 individuals from Hirashima.

　　The genital papillae which are symmetrically located and well deliniated are of round-shape and slightly convex forwards, about 0.7 mm (varying from 0.6-0.8 mm) in diameter, and are situated on the inside of the male pores on the setal line, as is shown in Text- fig. 1, 2.  The papillae are situated within the elevated area anterior to and slightly on the interior of the male pore in some specimens.  And somewhat separated from the male pore in the specimens from Asamushi but those which were collected in Sendai this papillae is either very closely located to the male pore or even whitin the pores.  When the distance between the pore and position of the papillae were reduced the area of elevation is correspondingly reduced.  The margin of the male pores and genital papillae are considerably elevated over the body surface.

　　The first dorsal pore is in XII/XIII.

 

Internal characters:

　　Spermatheca situated in segments VII and VIII.  The ampula is pear shaped somewhat ellipsoidal and slightly dorsoventrally flattened; about 4 mm long, 3 mm broad, and continuous to the spermathecal duct which is nearly of equal length or a little shorter than the ampulla.  The diverticulum is slender, very thick and tubular, much longer than the combined length of duct and ampulla, not coiled or looped, it is swollen in the middle region and forms a long chamber.  The ducts of diverticulum and of the main sac unite together near external orifice.

　　Ovisac one pair, it is small and hangs behind the septum XII/XIII.

　　Prostate gland extends through segments XVI-XXIII or XVI-XXIV, (about 8 or 9 segments occupied), but push XXIII/XXIV posteriorly and XV/XVI anteriorly and reach XIV/XV.  And are much lobulated and enlarged at both ends.  A large circular mass of small glands is located slightly anterior to the prostatic duct and interior to the prostate gland.  This body is composed of numerous individual glands and each gland has an opening externally in the papilla already above mentioned.

　　The vas defferens which leads from the prostate gland to the exterior is long and curved.

　　The genital papillae are found externally on segment XVIII, as is shown in Text-fig. 1, 2, and are associated with the accessory glands which appear as one part of the prostate glands, as shown in Text-fig. 2, 2.  This accessory glands sometimes varies like the capsulogenous glands as seen in Pheretima hilgendorfi Michaelsen, as is shown in Text- fig. 1, 5, A, and also sometimes appear as a compact glandular mass as seen in Pheretima yamizoyamensis Ofhuchi, as shown in Text-fig. 1, 5, B.

　　The saccular intestine commences in XV and a pair of the intestinal coecum or ginates originate in XXVII.  The coecum posses six finger-shaped projections as are seen in many species of Japanese Pheretima, and the most developed dorsal projection extends for five segments anteriorly, viz. to XXIII, as is shown in Text-fig. 1, 3.

　　The septum is rather delicate and not noticeably thickened though pre-gizzard three septa are somewhat thickened.  But the septum VI/VII and VII/VIII thickened, VIII/IX and IX/X absent, X/XI more or less thickened.  The septa in this species are less developed compared with other species in the same genus, viz. Pheretima kikuchii Hatai and Ohfuchi.

　　The ovaries are large but we was unable to find the ovisacs.

　　The seminal vesicles are well developed and situated in XI, XII very large, and cover the dorsal blood vessel in those vesicles; the anterior vesicles extend forward and come into contact with a third of the posterior end of the gizzard, the posterior vesicles extend to the middle of segment XIV; (Text-fig. 1, 4, A and B).

 

Remarks:

　　The prostatic duct, the prostate glands, the seminal vesicles, and the spermathecae are characteristically formed and well developed even in the smallest specimens of this species.  Thus all of the specimens, sufficiently exhibit the genital markings; the proportion of the clitellate to the aclitellate specimens are cited above.

　　It is very interesting to find that many earthworms of this species in North-eastern Japan are even aclitellate in September, a month much colder than other in localities of the same month of Honshu Japan.  This may be a characteristic of the earthworms living on small islets.

　　This interesting species was found in midst of the dense forest among semi-dried rootlets of trees and shrubs and in under accumulated withered leaves of Pinus thunbergii.  In fact the forest soils appear unfavourable to the earthworms due probably to the rather dried and comparatively high acidity of soils together with other factors of as yet unknown.  The presence of this species in dense forest is interesting from ecological standpoit also.  We may say however that whether this species lives exclusively in the forest in not yet determined.

内田智子, 伊原真樹, 2003. 金華山の大型土壌動物相. 宮城教育大学環境教育研究紀要 6: 31-37.