Caecidotea simulator, a new subterranean isopod from the Ozark Springfield Plain (Crustacea: Isopoda: Asellidae)

6 Pages·1999·2.3 MB·

by  J J Lewis

PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
112(1):175-180. 1999.
Caecidotea simulator, a new subterranean isopod from the Ozark
Springfield Plain (Crustacea: Isopoda: Asellidae)
Julian J. Lewis
217 W. Carter Avenue, Clarksville, Indiana 47129 U.S.A.
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Abstract. With the description of Caecidotea simulator, a. phreatobitic iso-
pod reported herein from Arkansas and Kansas, a total of six species of sub-
terranean asellids is now known from the Springfield Plain section ofthe Ozark
Plateau. The presence of C. macropropoda in Arkansas, a subterranean species
previously known with certainty only from Oklahoma, is confirmed by two
collections examined from northeastern Arkansas.
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The Springfield Plain is a region of gent- 13$ ?. Arkansas: Washington County, O.
ly rolling karst landscape formed on flat- A. Lasterling's well, 0.25 mile west High-
bedded limestones in the southwestern part way 71, Fayetteville, 22 Jul 1965, E. H.
of the Ozark Plateau. This area of the cen- Schmitz, 15(5 (?, 11$$.
tral United States includes parts of south- An 11.0mm 6 from Baxter Springs,
western Missouri, northwestern Arkansas, Kansas is designated as the holotype
northeastern Oklahoma, and a tiny piece of (USNM 216971), with paratypes from Bax-
southeastern Kansas. Previously reported ter Springs (USNM 222477) and Laster-
from the Springfield Plain were the subter- ling's well (USNM 216972). All of the ma-
ranean asellids Caecidotea ancyla (Flem- terial has been deposited in the collection
C
ing, 1972), C. antricola Creaser (1931), of the National Museum ofNatural History,
& C
macropropoda Chase Blair (1937), Smithsonian Institution.
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stiladactyla Mackin Hubricht (1940), and Description. Eyeless, unpigmented,
C. steevesi (Fleming 1972). The type spec- longest male to 19mm, female to 13mm.
imens of C. steevesi were examined and Body slender, linear, about 6.5X as long as
three species were found to be present: (1) wide. Margins of head, pereonites, and
C. steevesi from Carrico Cave, Dade Coun-
pleotelson moderately setose. Head about
Dtyo, wMnissMoouurnita(itynpe-Claovcea,litAy)d,aiarndCoGuintttye,n 1.5X as wide as long, anterior margin con-
C cave, postmandibular lobes moderately pro-
Oklahoma; (2) antricola, also in the Car- duced. Pleotelson about 2X as long as wide,
rico Cave collection; and (3) the new spe-
sides subparallel, caudomedial lobe slightly
cies described below from Baxter Springs,
produced.
Cherokee County, Kansas.
Mandibles with 4-cuspate incisors and la-
Caecidotea simulator, new species cinia mobilis, palp with rows of plumose
Figs. 1, 2a, c-f, 3a, b setae on distal segments. Maxilla 1 with 5
robust plumose setae on inner lobe, 13
Asellus steevesi Fleming 1972: 491-494
spines on outer lobe. Antenna 1 flagellum
[Baxter Springs, Kansas record]; 1973:
to 18 segments, esthete formula 3-0-1-0-1.
295, 300 [in part]. Antenna 2, last segment of peduncle about
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Material examined. Kansas: Cherokee 1.2X length of preceding segment, flagel-
County, Baxter Springs, seeps off 7th Av- lum of 19mm S with 168 segments.
enue, 12 Jun 1964, J. R. Holsinger, lOdd, Male pereopod 1, propus 1.5X as long as
176 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASfflNGTON
Fig. 1. Caecidotea simulator, male from Baxter Springs, Cherokee Co., Kansas: (a) habitus, (b) distal seg-
ments of antenna 1 flagellum, (c) right mandible, incisor, (d) left mandible, incisor and lacinia mobilis, (e)
mandibular palp, (f) maxilla 1, outer lobe, (g) same, inner lobe, (h) pleopod 3, (i) pleopod 5, (j) pereopod 4.
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VOLUME 112, NUMBER 1 177
Fig. 2. Caecidotea simulator, (a, c-f) male from Baxter Springs, Cherokee Co., Kansas, and Caecidotea
steevesi, (b, g) male from Carrico Cave, Dade Co., Missouri: (a) pleopod 1, (b) same, (c) gnathopod propus,
palmar margin, (d) pleopod 2, (e) same, endopod tip, (f) same, caudal processes folded over anterior processes
under coverslip, (g) pleopod 2, endopod tip.
wide, palm with raised proximal spine, me- concave, distal margin with 6—8 long plu-
dian triangular process and slightly bicuspid mose setae. Pleopod 2, protopod with 3 me-
distal process close together, sexual dimor- sial setae. Exopod, proximal segment with
phism absent. Pereopods 2-7 with moderate about 5 lateral setae, distal segment with
setation as figured, sexual dimorphism for about 15 long plumose setae along margin.
clasping slight with male pereopod 4 carpus Endopod with distinct basal apophysis, en-
2.6X as long as wide female 2.9X. dopod tip twisted in appearance, processes
Male pleopod 1, protopod about 0.6 directed away from axis of endopod, can-
length of exopod, with 4 retinacula. Exopod nula tapering to a stylet, mesial process ta-
about 1.6X as long as wide; lateral margin pering and becoming digitiform, decurved
178 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
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Fig. 3. Fourth pleopod exopods of related subterranean Caecidotea from the Springfield Plain: (a) sim-
ulator, Baxter Springs, Cherokee Co., Kansas, (b) C. simulator, Lasterling's well, Washington Co., Arkansas,
(c) Caecidotea stiladactyla, small seeps 4.0 m. S. Boxley, Newton Co., Arkansas, (d) C. steevesi, Gittin Down
Mountain Cave, Adair Co., Oklahoma, (e) C. steevesi, Carrico Cave, Dade Co., Missouri, (f) C. steevesi. War
Eagle Cave, Madison Co., Arkansas.
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VOLUME NUMBER
112, 1 179
mesiad, caudal process heavily sclerotized, quite distorted under the pressure of the
thickened laterally and mesially. Pleopod 3 glass (as the endopod twists). The endopod
exopod, proximal segment about 9.7 tips illustrated in Fig. 2 are the result of
length of distal segment, with about 6 plu- numerous attempts to gain the same per-
C
mose setae on distal margin. Pleopod 4 with spective for both simulator and C. steev-
up to 18 proximolateral setae, two false su- esi. The endopods appear to be fundamen-
tures present. Pleopod 5 with 2 sutures. tally similar, although side by side compar-
Uropods of male about 2X length of pleo- ison (Fig. 2e-g) illustrates minor differenc-
telson, equal to length of pleotelson in fe- es of questionable importance. For
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male. example, the mesial process in simulator
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Etymology. The noun "simulator", tapers to a narrow, cylindrical digitiform
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from the Latin meaning imitator or pretend- process, while in steevesi it is wider and
er, indicates the close resemblance of C. obliquely truncate.
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simulator to C. steevesL The vernacular The best way to separate simulator
name suggested for this species is the from C. steevesi is by the structure of the
Springfield Plain groun—dwater isopod. fourth pleopod exopod (Fig. 3a—b, d-f),
Habitat and range. Caecidotea simu- which has two false sutures in C. simulator
C
lator is known from the type-locality in (and macropropoda, Lewis, 1982, Fig.
southeastern Kansas and one locality in the 3h), but only a single sigmoid suture in C.
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adjacent comer of northwestern Arkansas. steevesi (and stiladactyla. Fig. 3c).
From its vermiform, eyeless, unpigmented
appearance C. simulator is clearly an in- Caecidotea macropropoda Chase & Blair,
habitant of subterranean waters. Caecidotea 1937
simulator has not been found in caves and
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presumably lives in the saturated soil inter- Material examined. Arkansas: Carroll
stices that supply groundwater to the two County, White River at Beaver Down, G.
sites from which it has been taken, a well C. Kephart, Jul 1978, ASS, 5$ $.—Wash-
and a seep spring.— ington County, spring 2.2 miles north
Relationships. Caecidotea simulator Dutch Mills, L. Hubricht, 21 May 1942,
and C. steevesi are very similar morpholog- 6S S 5 $ $ seep, 1.5 miles north Winslow,
, ;
ically. The gnathopods of both species are L. Hubricht,—22 May 1940, 31c?(5, 7? ?.
nearly identical. The apex of the first ple- Remarks. Lewis (1982) synonymized
C
opod exopod has elongate plumose setae in ozarkana with C. macropropoda and re-
both species, a characteristic also shared described the species. Dearolf (1953) re-
with all species of the Hobbsi Group (Lew- ported this species from two sites in Arkan-
C
is, 1982). In simulator these setae occur sas, but the validity of the records was un-
all the way across the distal margin of the known (Lewis, 1982). The records provided
C
pleopod and are about 7-8 in number. In here substantiate those of Dearolf for the
steevesi the setae are located only on the occurrence of C. macropropoda in Arkan-
mesial half of the distal margin and number sas. The species is endemic to the Spring-
4-5 (Fig. 2b). field Plain, where it is found in cave
Due to torsion of the second pleopod en- streams, springs, and seeps.
dopod the taxonomically important tip pro-
cesses are difficult to interpret and compare Acknowledgments
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in simulator and C. steevesi, a charac-
teristic shared with C macropropoda and The late Dr. Thomas E. Bowman provid-
C. stiladactyla. The critical features are not ed the loan of type-specimens of Caecido-
easily seen without applying a coverslip, tea steevesi from the collections of the
and the positions of the tip processes are Smithsonian Institution, read the manu-
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180 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
script, and offered suggestions for its im- Fleming, L. E. 1972. Four new species of troglobitic
provement. asellids—(Crustacea: Isopoda) from the United
States. Proceedings of the Biological Society
of Washington 84(57):489-500.
Literature Cited A
Lewis, J. J. 1982. diagnosis of the Hobbsi Group,
Chase, H. D.. & A. P. Blair. 1937. Two n—ew blind with descriptions of Caecidotea teresae, new
isopods from northeastern Oklahoma. Ameri- species, and C. macropropoda Ch—ase and Blair
can Midland Naturalist 18:220-224. (Crustacea: Isopoda: Asellidae). Proceedings
Creaser, E. P. 1931. A new blind isopod—of the genus of the Biological Society Washington 95:338-
Caecidotea, from a Missouri cave. Occasional 346.
Papers of the Museum of Zoology, University Mackin, J. G., & L. Hubricht. 1940. Descriptions of
of Michigan 222:1-7. seven new species of Caecidotea (Isopoda,
Dearolf, K. 1953. Th—e invertebrates of 75 caves in the Asellidae) from the central United States.
United States. Pennsylvania Academy of Sci- Transactions ofthe AmericanMicroscopicalSo-
ence 27:225-241. ciety 59:383-397.