Sphalloplana (Sphalloplana) percoeca (Packard 1879)

Sphalloplana (Sphalloplana) percoeca (Packard, 1879)

Dendrocoelum percoecum Packard, 1879:141.

Fonticola percoecum.—Hyman, 1931:328.

Sphalloplana percaeca.—Beauchamp, 1931:321.

Dendrocoelum percaecum.—Giovannoli, 1933:622.

Sphalloplana percaeca.—Castle and Hyman, 1934:156.

Fonticola percaeca.—Hyman, 1935:345.

Sphalloplana percoeca.—Hyman, 1937:469.

Sphalloplana (Sphalloplana) percoeca.—Carpenter, 1971:1284.

Sphalloplana alabamensis Hyman, 1945:476.

TYPE MATERIAL.—Packard's original material apparently is not preserved. Hyman's syntypes of S. alabamensis, one whole mount and two slides of sagittal sections (USNM 20639).

HISTORY.—The early history of the discovery and description of the species has been reviewed by Buchanan (1936:194). It was first depicted by Packard (1879:141) in a small, rather primitive illustration that was also reproduced in later publications of the same author (1880:141 and later editions of his Zoology; 1888:28). Illustrations of preserved specimens were furnished by Beauchamp (1931:322) and drawings and photographs of living animals by Buchanan (1936:196) and Carpenter (1970, fig. 11). Descriptions of the species were given by Packard (1888:28), Beauchamp (1931), Buchanan (1936:195–196), Hyman (1937:470–471), and Carpenter (1970:69–75). Hyman's description of S. alabamensis is based on badly preserved materials and contains several inaccuracies. In the following, only the essential characters of the species will be discussed.

EXTERNAL FEATURES (Figures 1, 11).—Sphalloplana percoeca is a purely white species, without any pigmentation. Mature animals generally are about 10–12 mm long and about 2 mm wide, but may reach a length of 16 mm. The anterior end has a bulging frontal margin and conspicuous rounded auricles projecting anterolaterally. The situation of the adhesive organ is seen as an opaque spot behind the center of the frontal margin. Behind the auricles, the lateral margins of the body narrow to some extent, then widen again. Characteristic is the outline of the anterior border of the intestinal area that is rounded and not forming the two lateral extensions seen in some species with more highly developed adhesive organs.

ANATOMY.—The adhesive organ (Figure 30) is a shallow subterminal pit lined with an infranucleate epithelium that is pierced by many eosinophilic gland ducts and equipped with a system of muscle fibers (see Beauchamp, 1931:323–325; Hyman, 1937:470).

In the reproductive system, examined by me in four sets of sagittal serial sections, the ovaries are situated at the level of the second or third lateral branch of the anterior intestinal ramus. The testes, in moderate number, are dorsal and prepharyngeal, occupying on either side a longitudinal zone. The copulatory complex (Figure 45) has been described and illustrated by Beauchamp (1931, fig. 8) and Hyman (1937, fig. 13), but needs further analysis. The genital atrium is divided distinctly into an anterior male atrium (am) surrounding the penis papilla and a posterior chamber that appears to be a combination of the common atrium (ac) and the expanded terminal part of the bursal duct or vagina (v). The penis has a rather small bulb (bp) with weak musculature and a large, generally rounded, plug-shaped papilla (pp). This corresponds to the penis shape illustrated by Beauchamp (1931, fig. 8) rather than to Hyman's (1937, fig. 13) diagram of the copulatory apparatus. The papilla is covered with a cuboidal epithelium with an underlying coat of muscle fibers, circular ones adjoining the epithelium and longitudinal ones below them. The bulb contains a small cavity, the seminal vesicle (vs), of rounded shape in a medial section, but extending laterally to both sides. From this cavity originates a duct (de) passing into the papilla, rather narrow in its anterior part and of variable diameter posteriorly, sometimes widening in a funnel-like fashion, and opening at the tip of the papilla. This lumen apparently corresponds to an ejaculatory duct. It is surrounded by a muscle layer consisting chiefly of longitudinal fibers. The sperm ducts or vasa deferentia (vd) approach the sides of the penis bulb, enter the bulb laterally, and open into the lateral extensions of the seminal vesicle. Eosinophilic gland ducts enter the penis bulb from the surrounding mesenchyme, traverse the penis, and open on the outer surface of the papilla. The two oviducts unite above the male atrium and the common oviduct (odc) thus formed opens into the dorsal roof of the male atrium, far removed from the gonopore (gp). The copulatory bursa (b) is a sac of variable shape located between the posterior wall of the pharyngeal chamber and the penial bulb. Its outlet, the bursal duct (bd), starts as a rather narrow, straight canal running posteriorly above the penis and male atrium to a level behind the gonopore. There it turns ventrally and expands into a voluminous cavity, the vagina (v), which is in wide connection with the cavity of the common genital atrium (ac). The vagina has a thick muscle coat of intermingled circular and longitudinal fibers. It was not possible to analyze the musculature of the anterior, thin part of the bursal duct.

All epithelia of the copulatory apparatus are nucleate except, perhaps, the lining of the male atrium, which appears to be, at least in part, infranucleate in some of the specimens studied.

DISTRIBUTION AND ECOLOGY.—Sphalloplana percoeca is a troglobitic species and appears to be widely distributed in the states of Kentucky, Tennessee, and Alabama, possibly extending also into West Virginia and Georgia. Localities that need verification are preceded by a question mark (?) in the following list.

ALABAMA. JACKSON COUNTY: (1) Dinky Pit, Alabama Cave Survey No. 756 (Carpenter, 1970:71). (2) Fern Cave, Survey No. 597, located just above the town of Paint Rock; about 25 specimens collected by William W. Torode, many mature, 14 December 1975. (3) Graham Pit, Survey No. 943 (Carpenter, 1970:71). (4) “Old Saltee Cave” (= Sauta Cave), Survey No. 50, near town of Lim Rock, type-locality of S. alabamensis (Hyman, 1945:477; Carpenter, 1970:71; Holsinger, 1966:85). (5) Williams Saltpeter Cave, Survey No. 590, located about 20 miles east of Huntsville; 30 specimens collected by W. W. Torode, some mature, 27 October 1975.

KENTUCKY. CALDWELL COUNTY: (1) ?Lisanby Cave (Carpenter, 1970:69). CARTER COUNTY: (1) ?Cascade Cave (Dearolf, 1953:226). EDMONSON COUNTY: (1) ?Diamond Cave (Packard, 1888:28). (2) ?Ganter Cave (Dearolf, 1953:226). (3) Great Onyx Cave (Carpenter, 1970:71); specimens kindly sent to me by J. H. Carpenter in February 1971. (4) Mammoth Cave, type-locality of Dendrocoelum percoecum, in Shaler's Brook, Gothic Avenue, Richardson's Spring, Annette's Dome, Audubon Avenue, and Rafinesque Hall (Packard, 1888:28; Bolivar and Jeannel, 1931:308; Beauchamp, 1931:317; Giovannoli, 1933:622; Buchanan, 1936:194; Barr, 1968:155); one specimen collected by the writer in Annette's Dome, August 1933. (5) ?White Cave (Dearolf, 1953:226; Carpenter, 1970:71; Barr and Kuehne, 1971:71). ESTILL COUNTY: (1) Pearson Cave (Carpenter, 1970:71). HART COUNTY: (1) ?Mammoth Onyx Cave (Dearolf, 1953:226). JACKSON COUNTY: (1) Clemons Cave, (2) John Rogers Cave, (3) Morning Hole Cave, and (4) Wind Cave (Carpenter, 1970:71). WAYNE COUNTY: (1) Jesse Cave (Carpenter, 1970:71).

TENNESSEE (all records need verification). CAMPBELL COUNTY: (1) Meredith Cave (Barr, 1961:31). DAVIDSON COUNTY: (1) Mill Creek Cave (McRitchie, 1959:31). PUTNAM COUNTY: (1) Harve Petty Cave (Barr, 1961:31). RUTHERFORD COUNTY: (1) Herring Cave (McRitchie, 1959:31). VAN BUREN COUNTY: (1) Creeping Cave (Barr, 1961:31). WHITE COUNTY: Indian Cave (Carpenter, 1970:71).

WEST VIRGINIA. PENDELTON COUNTY: (1) ?Blowhole Cave (Carpenter, 1970:69).

Sphalloplana georgiana, a problematic species, may also be identical with S. percoeca. The localities of that species are listed under S. georgiana.

Some ecological data for S. percoeca were presented by Buchanan (1936): The temperature of the waters in Mammoth Cave was in the range of 12°C to 14°C, the pH, 7.6. Holsinger (1966:85) observed a large population of “S. alabamensis” in Sauta Cave in a rimstone pool where large amounts of decaying wood had accumulated; he speculated that the flatworms may be able to feed on particulate organic matter or on smaller organisms that inhabit such pools or on both types of food. Barr (1968:155) and Barr and Duehne (1971:71) reported that the species in White Cave occurred in temporary rimstone pools soon after the pools filled with water dripping from stalactites or trickling down and concluded that they had survived in the silts of the dried pools by encysting in the layers of the hygroscopic deposits at the bottom of the pools. A similar survival of cave planarians had been reported by Ginet and Puglisi (1964) for Phagocata notadena (Beauchamp) and by Gourbault (1965:477) for Dendrocoelopsis chattoni (Beauchamp) in two caves in France. The same mode of survival during the desiccation of the habitat is known also for some epigean planarians (see, for example, Lascombe, 1971:31–32). Carpenter (1970 and 1973) reported that cocoons of S. percoeca were found in the caves in spring and summer and hatched in the laboratory at 13°C in about three months, each cocoon yielding 2–17 young.

PHYSIOLOGICAL STUDIES.—Buchanan (1935 and 1936) studied the behavior of the species in the cave and the laboratory, its locomotion, reactions to light, tolerance of acidity and alkalinity (pH 6.6 to 8.0) and of temperature (it may tolerate 24°C for hours), and its limited regenerative ability. Wells and Harris (1954) reported briefly on its sensitivity to ultraviolet irradiation.

TAXONOMIC POSITION.—The weakly developed adhesive organ places S. percoeca in the subgenus Sphalloplana of which it is the type-species. Other specific characteristics are the presence of conspicuous auricles, the rounded anterior border of the intestinal area, the dorsal position of the testes, the shape of the penis (with small bulb and large, plug-shaped papilla), the lateral entry of the vasa deferentia, the opening of the penis lumen on the tip of the papilla, the confluence of the common genital atrium and the vagina of the bursal duct, and the location of the mouth of the common oviduct, far removed from the genital aperture. From the externally similar S. consimilis it differs by its penial structure, from S. evaginata by the absence of diverticula on the common genital atrium, and from S. holsingeri by the dorsal position of the testes and the anatomy of the copulatory complex.