ホソミミズ

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External characters:

  The body length from 50-64 mm, the greatest diameter from 3.5-4 mm, the number of segments varies from 80-93.

  The color of this worm in formalin, brownish dorsally, light ventrally, clitellum blackish brown, extends from XIV to XVI, dorsal pores, intersegmental furrows and setae are lacking.

  The setae begins on segment II.  Setae prominent on ventral side of anterior segments, ventral setae of III-VIII or IX noticeably long and widely spaced.  Both dorsal and ventral breaks very distinct.  The setae numbers are as follows; 22-24/V, 25-27/VI, 28-31/VII, 33-36/ VIII, 48-53/XX.

  The first dorsal pore is in XI/XII.

  Two pairs of spermathecae pores in VI/VII and VII/VIII, ventro-lateral in position, each pore is minute.  No genital papillae are found near this region.

  The male pores situated on setae circle close to lateral border of XVIII, about 1/3 of circumference apart, separated by 14 setae.  The margin of the male proofer is considerably elevated over the body surface.

 

Internal characters:

  Septa VI/VII, VII/VIII and VIII/IX slightly thickened, absent in IX/X, X/XI, XI/XII and XII/XIII scarcely forms the membrane.

  Intestine begins in XIV and a pair of intestinal coecum commences in XXVII and extends to XXIV anteriorly, it is a simple sac-shaped and not serriformed on both ventral and dorsal margins.

  Two pairs of spermathecae are found in VII and VIII.  Ampulla differentiated from its duct and longer than the latter, well-distended, ovoidal or pear-shaped, its surface dull pale and smooth and slightly flattened door-ventrally, about 2 mm in length, 1.5 mm in breadth and continuous to the short ampullary duct which is about 1 mm in length, sharply marked off from ampulla.  The spermathecal diverticulum usually arises from the inner face of the spermathecal duct, usually twisted in its most part, always longer than the main portion if stretched, and forming a seminal chamber in its mental end, but sometime no trace of chamber is found.

  The ovisac is present in segment XIV.

  The prostate gland always well developed, thick and expanded, whitish and smooth on surface, divided into two or three main lobes, and again subdivided into small pieces.  The muscular duct short but stout, not looped as usually seen in other species of this genus.

  Seminal vesicles are well developed and are situated in XI and XII.  Testis sacs large, roundish and flattened, in X and XI as in the other species of this genus.

 

Remarks:

  Present species differs from Pheretima micronaria and Pheretima oyuensis, that the formers possesses four pairs spermathecae in Vi, VII, VIII and IX and latter has no spermathecae, and by other various characters.

  This species is the smallest one of the species known today possessing two spermathecae in VII and VIII known among Riu-kiu species of Pheretima.

  It is closely resembles to both Pheretima micronaria and Pheretima oyuensis in several aspects such as (1) body size, and (2) feature of intestinal caeca.  But it is easily distinguished from Pheretima micronaria by (1) presence of genital papillae in the male pore region, (2) spermathecae without the diverticulum, and (3) possession of four pairs spermathecae in VI, VII, VIII and IX, and also differs from Pheretima oyuensis particularly by having no spermathecae, male pore, or prostate gland.