Sphalloplana (Speophila) chandleri Kenk 1977

Sphalloplana (Speophila) chandleri

Speophila hubrichti.—McRitchie, 1959:20 [misidentification].

Sphalloplana (Speophila) pricei.—Carpenter, 1970:96 [in part].

TYPE MATERIALS.—Holotype, set of sagittal sections on 7 slides, USNM 53416. Paratypes, 10 sets of sagittal and transverse sections on 62 slides, USNM 53417–53426.

EXTERNAL FEATURES (Figures 10, 26).—A purely white species of moderate size, up to 18 mm long and 3 mm wide. Smaller individuals (12 mm long) may also be sexually mature. The anterior end is truncated, with a somewhat convex frontal margin and rounded lateral corners lacking prominent auricular projections. The protrusible adhesive organ is seen as a slightly opaque area and its outlet may be noticeable as a small notch in the midline of the frontal margin when the animal is gliding quietly. There is no definite constriction or neck behind the anterior end, only a gentle narrowing of the body margins when the animal is in locomotion. Then the body widens gradually, to narrow again in the postpharyngeal region to a rounded or bluntly pointed posterior end. The anterior portion of the intestinal area forms a V-shaped border, the lateral branches of the intestine reaching farther forward to both sides of the adhesive organ than the median intestinal trunk. The root of the pharynx is located at about the middle of the body length or slightly behind the middle. Its length is about one-eighth the length of the body.

ANATOMY.—The adhesive organ (Figure 38), in its retracted state, is a deep invagination with folded walls, as is typical for the subgenus Speophila. The zone of marginal epithelium is also typically developed.

The two ovaries are situated below or behind the first to third pair of lateral intestinal branches. The numerous, rather small, rounded testes are strictly dorsal, occupying, on either side of the midline, a longitudinal zone beginning some distance behind the level of the ovaries and ending near the pharyngeal root. The copulatory complex (Figure 60) was studied in 14 sets of serial sections. The genital aperture or gonopore (gp) leads into the common genital atrium (ac) that is not very clearly marked off from the terminal part of the outlet (bd) of the bursa copulatrix (b). Anteriorly, the common atrium connects with the male atrium (am) surrounding the penis papilla. The penis appears in the slides in various stages of muscular contraction indicating the great plasticity of this organ. The rounded, muscular penis bulb is of moderate size. The penis papilla, when extended (Figure 60), is long, finger-shaped, and larger than the bulb. In several of the specimens, however, the posterior part of the papilla is inverted into the penis lumen to a varying degree or even telescoped (Figure 61). The musculature of the penis papilla is restricted to a two-layered coat underlying the external epithelium, while the penis lumen seems to be devoid of a musculature of its own. The penial lumen consists of a rather large cavity, lined with a tall, secretory epithelium, the seminal vesicle (vs), located in the penis bulb and extending into the basal part of the penis papilla, and a canal (de) of variable diameter running through the rest of the papilla and opening at its tip. This canal, corresponding to an ejaculatory duct, has a nonglandular, cuboidal or flattened epithelial lining. The two vasa deferentia (vd) approach the copulatory apparatus as expanded, twisted spermiductal vesicles filled with masses of sperm, run posteriorly to the level of the male atrium, curve dorsally, enter the penis bulb posterodorsally, and open into the seminal vesicle. This recurving of the vasa deferentia is very characteristic and was seen in all specimens examined, regardless of the state of contraction of the muscular organs. The common oviduct (odc) opens into the posterior part of the male atrium from the dorsal side, generally at a considerable distance from the gonopore (in the specimens from Indiana and Virginia more closely to the gonopore). The copulatory bursa (b) is a rounded sac of variable size. Its outlet, the bursa stalk (bd), widens gradually as it proceeds posteriorly, then becomes contorted and thrown into loops, and bends ventrally to unite with the common atrium. The terminal part of the bursal stalk does not change its histological characteristics. The muscle layer surrounding the stalk consists of intermingled circular and longitudinal fibers.

None of the epithelia of the copulatory apparatus are infranucleate.

DISTRIBUTION AND ECOLOGY.—Sphalloplana chandleri was collected by Dr. Clay Chandler under rocks in a stream issuing from a cave near Stokes Lane in Nashville, Davidson County, Tennessee, on 22 August 1973 (water temperature, 16°C) and in May 1975. A total of about 35 specimens were sent to me alive. Some were placed in cultures maintained at about 14°C. Two cocoons were laid in the cultures soon after the collection dates. The cocoons are spherical, unstalked, 1½ mm in diameter. The locality has been known to turbellarian workers for some time. The presence of “Speophila hubrichti” in the Stokes Lane spring had been reported by McRitchie (1959:20) and by Darlington and Chandler (1972:60). McRitchie states that he collected a very large specimen, 3 cm in length, on 5 May 1959. Carpenter (1970:96), who considered S. hubrichti to to be a synonym of S. pricei, listed S. pricei for the same locality, collected in 1969. Other possible habitats of “S. hubrichti” in Tennessee, mentioned by McRitchie (1959:21) (spring at junction of U.S. routes 70N and 70S, Cheatham County, and Herring Cave, near Lascassas, Rutherford County), which also may refer to S. chandleri, need further examination.

INDIANA. Small spring next to the road on Edwardsville Hill, west of New Albany, Floyd County. One specimen collected by Jerry Lewis on 22 December 1974 (besides Phagocata gracilis).

VIRGINIA. Fallen Rock Cave, Tazewell County, located 5 miles south-southeast of Pounding Mill. A total of 7 specimens collected by John R. Holsinger and others on 13 October 1973, 27 July and 27 November 1974, and on 24 July 1976.

One cocoon, laid in a culture (kept at 14°C) in June, hatched after about 12 weeks and nine young emerged.

McRitchie (1959:20, 36, 37) comments on the gliding and leechlike locomotion and on the sensitivity to light of the form from the Stokes Lane spring.

TAXONOMIC POSITION.—Sphalloplana chandleri, apart from its well-developed adhesive organ that places it in the subgenus Speophila, is characterized by the lack of auricles, the V-shaped anterior intestinal border, dorsal position of the testes, recurving of the sperm ducts before dorsal entry into the penial bulb, large penis papilla, nonmuscular penial lumen, and lack of a distinctive vagina. In life, it is very similar to S. pricei (lack of auricles, V-shaped intestinal border), but differs from it by the dorsal location of the testes and the recurving of the vasa deferentia. Sphalloplana hubrichti, which also has a similar outline of the anterior end, has a different intestinal border and configuration of the sperm ducts. It is interesting to note that Carpenter (1970:88, 96) was aware of some of these differences but did not consider them to be significant enough to be the basis of species separation.

The species is named in honor of the collector, Dr. Clay M. Chandler of the Middle Tennessee State University.