External Characteristics:
Colour, dark blue or dark reddish blue dorsally, lighter ventrally, clitellum reddish or pinkish in living condition.
Length 63-100 mm in apparently mature specimens, and usually 80-90 mm, greatest diameter in clitellum region 3-4 mm, number of segments 130-186, usually 140-170. Prostomium prolobous.
Dorsal pores absent, and middorsal line not thinner than the rest. In shape of the body, I-IX rather cylindrical as in Dr. nemora.
Clitellum in X-XIII, not so distinctly swollen from the neighbouring segments as in Dr. gisti; but clearly distinguishable from the rest in glandulation and colouration. The
ventral side of it is less glandulated, and the midventral portion is rather non-glandulated and tends to become somewhat flattened, especially on X and XI, and besides, the medial sides of
the male porophores are slightly concave.
Setae short and closely paired. Those on II and on clitellar segments may be slightly smaller than the rest. Setal distance ab=cd; anteriorly to about VI aa larger than bc, on
about VII-XV aa nearly equal to bc, behind this region, especially behind XX aa much smaller than bc; dd nearly equal to, or a very little larger than 1/2 of the circumference. Just
medial to c-lines and also just lateral to b-lines, the skin behind clitellar region is thinner, and each appears to be a distinct pale line.
Male pores, one pair each on top of a moderately sized nipple-like or sometimes conical porophore, which is always formed by markedly elevated glandular skin near the posterior about
1/3-1/2 of X, and is situated between b and c, much nearer to b. This porophore is always slightly projecting beyond 10/11 into anterior part of XI; anterior border of XI facing each
porophore may be also slightly elevated (Fig. 3, a).
Female pores, one pair, minute, slit-like, scarcely visible in line with b, on quite anteriormost border of XII; rather easily visible in macerated specimens.
Spermathecal pores, one pair, in 7/8, in c-line or just medial to c; each on a trifle tip which projects from the posterior edge of the preceding segments and is moderately sunken into the
intersegmental furrow; mouth of this depression may be largely opened and its vicinity may be glandulated in mature specimens.
Genital papillae resemble in shape those of Dr. japonica, but much less in number, and not found infrequently; 1-4 in number if present, and irregulary placed on VII-XII, most
frequently on VIII-X unpairly, and midventrally or in ab-line or between b and c.
Internal Characteristics;
Septa 5/6 and 8/9 moderately, 6/7 and 7/8 much thickened and some what musculated, the rest thin; all septa except 10/11 almost normally inserted. Dorsal part of septum 10/11
displaced posteirorly to meet dorsolaterally with 11/12 in intersegmental space of 11/12.
Gizzards, two or three. Each somewhat pot-shaped or barrel-shaped, small but strongly musculated and shining, in XII-XIII or - XIV. In every twenty of the Kyojo and Ryujin
specimens their number was examined; in the former mostly two (2 in fifteen cases and 3 in five cases) and in the latter mostly three (3 in fourteen and 2 in six cases). When three
gizzards are present, the middle one is usually slightly larger than the others.
Testis sacs, one pair, moderate in size, each suspended by 9/10 the larger half lying in X. Its lateral face is usually constriceted moderately by the septum, so it appears to be
kidney-shaped. Those in mature specimens are massive, yellowish white, and granular on surface. Spermduct short, loosely twisted its larger part placed IX, and piercing 9/10 into
X, and entering into parietal wall just at anteromedial side of ectal end of the prostate. Prostate thick and short, about 2 mm long and 1 mm wide, usually compressed and weakly
constricted at its ventral side in about middle portion, somewhat resembling testis sac in shape, but rather thumb-shaped in immature and also in semi-mature specimens, whitish to light
brownish yellow and moderately warty on surface. Removal of its glandular investment reveals a relatively thick but short, tubular body.
Ovarian chamber in XI, formed by 10/11 and 11/12, both septa entirely fused dorsolaterally in intersegmental space of 11/12 (not reaching to middorsal), but separate by about one
segment ventrally, also closed around oesophagus in an inverted U-shape. Ovaries fairly large, much tufted. Ovisacs situated dorsolaterally on alimentary tract, Iong and slender,
moniliformed or distinctly constricted by each septum through its course, extending posteriorly into about XVIII, seldom behind this into XXII or XXIII and in front of this only into XIV or
XV, and never extending so far back as in Dr. japonica; yellowish in appearance fully filled with ripen ova; ova about 5-10 μ in diameter. Posterior part of slender ovisac
usually free from the septa, is situated in various places such as under or laterally to, gizzard or intestine, or pointing anterior-wards by reflection. Even when the ovisac is fully
filled with ova and appears to be yellowish, the posterior end of it which may be only 1-2 mm does not contain ova and remains whitish in appearance compared to the rest.
Spermathecae, one pair, with its atrium wholly lying upon posterior face of 7/8 (Fig. 3, b & c). Ampulla thin-walled, spherical (in immature specimens usually ovoid and empty);
duct very short but very thick and slightly shining, not making a mass of coils in any parts, but loosely twisted, its ental portion much thicker than the rest, about two to three times of
the latter. This much thicker and shorter portion resembles the ampullar duct and the following thinner and longer portion a diverticulum, in a spermatheca of the genus Pheretima.
It is not sharply marked off from the ampulla; ectally joining with entail and dorsal surface of the atrium, but its lumen not fusing with that of the atrium until near the ectal end of
the latter. Atrium small and short, sac-like, always (at least in mature specimens) shorter than diameter of the ampulla, its entail end rounded but not enlarged; when it is separated
off from parities, spermathecal opening may appear as a minute aperture at its ectal end.
Elastic, thickly discoidal accessory glands always found projecting through parities into coelom, corresponding to the external genital papillae; seldom, similar ones may be found
internally even when papillae are not found externally.
Remarks:
The present species closely resembles Dr. japonica in many respects, but differ considerably in (1) general form of the body, (2) aspects of male porophore, and (3) length and
thickness of spermathecal duct.
The region of I-IX is longer than that of Dr. japonica; the shape of this region is cylindrical in the former and is rather shortly ovoid, being weakly constricted in front of
clitellum in the latter; anteroposterior length of each segment of this region is always, at least in equal-sized worms, longer than that of the latter.
Situation of the male pores resembles each other. But, the male porophore in this species is much larger and always somewhat nipple-like or rather penis-like in shape, while it is
only a small oval tumescence in the latter. Proximal position of the porophore is also different; in the former it is at about the posterior 1/3 or often almost 1/2 of X, while in the
latter it is usually at about the posterior 1/5.
Length of spermathecal duct shows slight variation in both species. But, even in the comparison of the longest case of the present species with the shortest of Dr. japonica, the
former is much shorter but much thicker than the latter and weakly musculated and shining, while in the latter it is rather fine through its entire length except for only both entail and
ectal ends (Fig. 1 and Fig. 3, b and c).
The present species also resembles Dr. propatula Gates, but differs mainly in body size, aspects of male porophores, and length and thickness of spermathecal duct. The
differences between the present species and to either Dr. propatula or Dr. japonica appear to be more distinct than those between the latters.
日本産ミミズ大図鑑
