Polycelis coronata brevipenis Kenk 1972

Polycelis (P.) coronata brevipenis Kenk, 1972

Polycelis coronata.–Hyman, 1931:124–135.–Kenk, 1952:194–198.

Polycelis coronata brevipenis Kenk, 1972:27.

HOLOTYPE.–North Fork of Thompson River, 1 mile below Glenhaven, Larimer County, Colorado; series of sagittal sections, USNM 23679.

The subspecies P.c. brevipenis was first described from South Dakota by Hyman (1931) who assumed that it was identical with Girard’s Phagocata coronata from Wyoming, which was known only by its external appearance. Hyman’s description was later supplemented by Kenk (1952) who collected the same form in Colorado. Braithwaite (1962), while studying the anatomy of a Polycelis from Utah, discovered certain differences between his worms and Hyman’s account of the reproductive system of the South Dakota form. As he had no comparative material from Girard’s type-locality, he refrained from naming the local species from Utah and pointed out that the problem of the taxonomic status of the North American Polycelis was not yet settled. Kenk (1972:27), upon examining specimens from Fort Bridger, Wyoming, recognized their identity with the form from Utah and considered the animals from South Dakota and Colorado to be sufficiently different from the worms of Wyoming to justify the establishment of a new subspecies, P.c. brevipenis.

CHARACTERISTICS OF THE SUBSPECIES.–In life P.c. brevipenis is indistinguishable from the nominate subspecies (p. 3; see also Hyman, 1931:126–127; Kenk, 1952:194–195). It differs from the subspecies P.c. coronata in the shape and structure of the male copulatory organ (Figure 5). The penis bulb is elongated, very muscular, and much larger than the short and rather broad penis papilla. The penis lumen is likewise elongated, its bulbar section (seminal vesicle) is lined with a cuboidal, nonglandular epithelium. The two vasa deferentia enter the seminal vesicle from the sides, often asymmetrically. Many gland ducts containing a slightly eosinophilic secretion penetrate the muscular layers of the penis bulb and empty into the seminal vesicle. The bursal stalk shows the same division into an anterior glandular and a posterior muscular section as in the case of the nominal subspecies.

ECOLOGY AND DISTRIBUTION.–P.C. brevipenis, like the two other subspecies of P. coronata, is an inhabitant of cold streams and mountain lakes and has, so far, been recorded only from South Dakota and Colorado, but it is probably more widely distributed in the mountainous regions of the western states. The following localities yielded sexually mature specimens:

COLORADO (cf. Kenk, 1952:196). LARIMER COUNTY: Localities in Rocky Mountain National Park: (1) Poudre Lake, (2) Thompson River in Moraine Park, (3) Chiquita Creek on Fall River Road, and (4) Glacier Creek (tributary of Thompson River), 24–27 September 1951. (5) North Fork of Thompson River, 1 mile below Glenhaven (type-locality of the subspecies), 28 September 1951.

SOUTH DAKOTA. Stream near Deadwood (Lawrence County?), in the Black Hills, 30 August 1929 (see Hyman, 1931:130).

LIFE CYCLE.–Hyman stated that many of the worms collected in August in the stream near Deadwood were sexually mature, that no cocoons were found in the field, and that there were no indications of the occurrence of fission. Kenk (1952:196) reported that among 39 specimens taken in Glacier Creek in September, 17 were asexual, showing no signs of reproduction, 20 showed evidence of recent fission, and only 2 were sexually mature. In other localities, the great majority of the collected animals were also asexual. These data are too meager to permit any conclusions concerning the seasonal distribution of the reproductive activity.

Male atrium surrounded by a very thick muscle coat.