Caecidotea antricola Creaser 1931

Caecidotea antricola Creaser

Caecidotea antricola Creaser, 1931:1–7, pls. 1, 2.—Miller, 1933: 102, 104.—Van Name, 1936:473–476; 1940:133.—Mackin and Hubricht, 1940:390, 394.—Levi, 1949:3.—Nicholas, 1960a:131.—Steeves, 1969:52,53.—Peck and Lewis, 1978:44, 55.

Asellus antricolus.—Hubricht, 1950:16.—Mackin, 1959:875.—Steeves, 1966:392, 394–396, 398–401, figs. 7–13.—Fleming, 1972a:227, 231; 1973:294, 300.—Lewis, 1974:8, 15.—Pflieger, 1974:37.—Craig, 1975:3.—Kenk, 1975:333; 1977:7.—McDaniel and Smith, 1976:58.

Asellus antricola.—Dearolf, 1953:227.—Bresson, 1955:51.

Asellus alabamensis.—Chappuis, 1957:42.

“Blind isopod”.—Mohr and Poulson, 1966:68, 150, 151 [photographs].

Conasellus antricolus.—Henry and Magniez, 1970:356.

Acellus atricolus.—Miller, 1974:14.

[Not Asellus antricolus.—Fleming, 1972a:245.] [Kentucky, record.]

HISTORY.—The first record of Caecidotea antricola was Creaser's (1931) description of specimens from River Cave, Camden Co., Missouri. Although the description is rather long and detailed, the male second pleopod tip was described only as “armed at apex with three teeth,” and only a small drawing of the entire second pleopod was given. Although Creaser pointed out that the validity of the genus Caecidotea was uncertain, he placed his new isopod in that genus and gave a key to the known species.

In an argument for synonymizing Caecidotea with Asellus, Miller (1933) included C. antricola in a table comparing 45 asellid species and subspecies.

Van Name (1936) repeated Creaser's (1931) description and later (1940) added a new locality for the species in St. Louis Co., Missouri.

Mackin and Hubricht (1940) noted the similarities of C. antricola to C. packardi and C. acuticarpa Mackin and Hubricht (1940). Levi (1949) likewise compared C. conestogensis with C. antricola.

Hubricht (1950) included Asellus antricolus in a checklist of Ozark cave invertebrates and gave as its range “caves east of the Crystal City Escarpment” without adding new specific localities. Dearolf (1953) gave records of A. antricola from 7 Missouri caves in his checklist of invertebrates from 75 U.S. caves.

Bresson (1955) included A. antricola in a list of 27 known nearctic asellids. Chappuis (1957) recorded it as Asellus alabamensis from caves in Crawford and Jefferson counties, Missouri. Mackin (1959) included A. antricolus in a list of cave asellids. Nicholas (1960a) compiled a checklist of the troglobites of the U.S., which included C. antricola. Nicholas restricted the range of the species to the “Type locality and St. Louis Co., Missouri,” apparently unaware of Dearolf's (1953) records.

Mohr and Poulson (1966) included 2 photographs of the species in their book on cave animals.

Steeves (1966) partly redescribed Asellus antricolus using specimens from Crevice Cave, Perry Co., Missouri, since the type-specimens had been damaged. Several new records for the species were given for Missouri, along with a single Arkansas locality. In the same paper Steeves proposed a phylogeny of 13 troglobitic asellids, expressing the belief that A. antricolus was most closely related to A. alabamensis. Steeves (1969) again mentioned Caecidotea antricola in a historical review of American asellids.

In a revision of asellid classification Henry and Magniez (1970) divided the North American Asellus among 3 genera (Asellus, Conasellus, Pseudobaicalasellus) and included Conasellus antricolus in a list of 34 species assigned to Conasellus.

Fleming (1972a) compared A. antricolus to A. extensolingualus Fleming (1972) and listed 8 new localities, including an erroneous one in Kentucky. The following year Fleming (1973) included A. antricolus in a checklist and key to the species of Asellus.

Asellus antricolus appeared in checklists of invertebrates of Mystery Cave (Lewis, 1974), inhabitants of Missouri springs (Pflieger, 1974), and subterranean invertebrates of Missouri (Craig, 1975).

In an aquatic microhabitat study conducted in Tumbling Creek Cave, Taney Co., Missouri, Miller (1974) compiled a list of the aquatic species known from the cave including Acellus atricolus [sic].

Kenk noted the occurrence of Asellus antricolus with the flatworms Macrocotyla lewisi Kenk (1975) and Sphalloplana evaginata Kenk (1977) in caves in Perry Co., Missouri.

McDaniel and Smith (1976) reported A. antricolus from 5 caves in Arkansas.

MATERIAL EXAMINED.—ARKANSAS. Benton Co.: Logan Cave, Civil War Cave, leg. Mark Schram (no date). MISSOURI. Perry Co.: Mystery Cave, 5 mi (8 km) SE Perryville, stream pools in North Upper Passage, leg. J. Lewis, 6 May 1972, 1 (10.0 mm), 1 (13.6 mm); 20 May 1972, 2. LaClede Co.: Ratcliffe Cave, leg. J. Vineyard, 1 Aug 1974, 1, 1. Pulaski Co.: Folly Cave, 6 mi (9.7 km) S St. Robert, leg. J. Gardner, 2 Mar 1979, 2, 1. Stockpen Cave, leg. J. Gardner, 28 Nov 1978, 1, 2. Crawford Co.: Jagged Canyon Cave, in small quiet pool with muddy substrate, leg. J. Gardner, 4 Oct 1978, 1 (11 mm). St. Louis Co.: small cave, Fern Glen, leg. L. Hubricht. St. Genevieve Co.: Kohm's Cave, leg. J. Lewis, 12 Apr 1975, 1.

DESCRIPTION.—Large, eyeless, unpigmented. Length up to about 15 mm in specimens examined (Steeves (1966) reported length to 20 mm); body slender, linear, about 5.1× as long as wide; coxae visible in dorsal view. Margins of head, pereonites, and telson very setose; dorsum of pereonites with many small spines. Head about 1.6× as wide as long; anterior margin concave; postmandibular lobes moderately produced. Telson about 1.3× as long as wide; sides subparallel; caudomedial lobe slightly produced.

Antenna 1 reaching middle of last segment of antenna 2 peduncle; flagellum with about 10 to 14 segments; esthete formula 3-0-1 or 4-0-1. Antenna 2 reaching anterior margin of pereonite 7, last segment of peduncle about 1.5× length of preceding segment; flagellum with about 90 segments.

Mandibles with 4-cuspate incisors and lacinia; spine row with 17 spines in left mandible, 20 spines in right mandible; distal segment of mandibular palp with elongate plumose setae. Maxilla 1, outer lobe with 13 robust apical spines and 2 plumose setae, 1 subterminal; inner lobe with 5 apical plumose setae. Maxilliped with about 6 retinacula.

Pereopod 1 of , propus about 1.4× as long as wide; palmar margin with small triangular proximal process and large bicuspid distal process; dactyl flexor margin with proximal slightly produced boss and distal row of spines, size varying with age. Pereopod 1 of , propus about 1.7× as long as wide; palm with robust spine proximally, and low, slightly produced, bicuspid distal process. Pereopod 4 of and similar, sexual dimorphism moderate, mesial margin of dactyl with about 2 spines.

Pleopod 1 longer than pleopod 2; protopod about 0.6× length exopod, with about 8 retinacula. Exopod about half as wide as long, with about 6 long setae on proximal lateral margin tapering to row of short setae along distal lateral margin, apex with several setae along margin and subterminally. pleopod 2 exopod, proximal segment with about 5 plumose setae; distal segment oval, with about 18 long plumose setae along margin of distal part. Endopod with broadly rounded basal apophysis; tip ending in 3 processes: (1) lateral process extending almost perpendicular to axis of endopod, slightly S-shaped, tapering distally to rounded point; (2) cannula distal to and parallel with lateral process, length about equal to lateral process, beakshaped; (3) caudal process broadly rounded, comprising apex of endopod bearing other processes. Pleopod 2 of with about 10 long plumose setae. Pleopod 3 exopod, proximal segment about 0.7× length of distal segment, apical margin with about 9 plumose setae. Pleopod 4 exopod type B, without proximal spinules on lateral margin. Uropod rather setose, very elongate, at least 0.5× length of body, protopod about 1.3× length of endopod and at least 5× length of exopod.


VARIATION.—The size of this species is highly variable. Specimens from the Perry Co., Missouri, area are the largest and most robust examined, and specimens from Arkansas are much less robust in appearance. In comparison with the Perry County population described herein, the following differences have been noted in Arkansas specimens: (1) pereopod 1, palmar margin of propus processes less robust; (2) pleopod 1, proximal segment with 4 to 6 retinacula on mesial margin, lateral margin of some individuals with a seta; distal segment, setae of lateral margin forming a continuously tapering row rather than a sharply demarcated row of long, then short setae as illustrated (Figure 10f); (3) pleopod 2, protopod in some individuals with 1 or 2 setae on mesial margin; exopod with setae present as illustrated (Figure 9h) but with some variation in numbers; endopod tip processes generally as illustrated (Figure 10i,j), curvature of lateral process slight in some specimens, cannula likewise less robust.

ETYMOLOGY.—The origin of the name was not given by Creaser (1931), but obviously indicates an inhabitant of caves.

RELATIONSHIPS.—Relationships of C. antricola are discussed under C. beattyi, the species which is closest to it morphologically.

HABITAT.—Caecidotea antricola is an inhabitant of cave streams and pools (Figure 11g), where it can be found under stones, crawling across gravel or mud-bottom pools, or occasionally in drip pools.

RANGE.—We have examined C. antricola from 1 Arkansas and 6 Missouri counties; this species appears to be endemic to the Salem Plateau section of the Ozark Plateau province. This region is underlain by Ordovician sedimentary rocks, largely limestone and dolomite (Vineyard and Feder, 1974). In Missouri alone more than 3500 caves are known, providing ample suitable habitats for the dispersal of C. antricola. Fleming (1972a) erroneously reported this species from Kentucky.