Cambarus truncatus Hobbs 1981

Cambarus (Depressicambarus) truncatus

Cambarus diogenes subsp.—Hart and Hart, 1974:33.

On the basis of my tentative identification of a specimen of this crayfish, from 8.1 miles east of Irwinton on State Route 52, Wilkinson County, Georgia, Hart and Hart (1974) recorded it as a host of Ankylocythere tiphophila (Crawford, 1959).

DIAGNOSIS.—Eyes small. Rostrum without marginal spines or tubercles and lacking median carina. Carapace without cervical spine or prominent tubercle. Areola obliterated or as much as 50 times as long as broad, constituting 38.2 to 42.5 (average 40.6) percent of entire length of carapace (44.0 to 47.7, average 46.0, percent of postorbital carapace length). Suborbital angle virtually obsolete. Postorbital ridge terminating cephalically without spine or tubercle. Antennal scale almost 3 times as long as wide, widest distal to midlength. Palm of chela with at least 2 rows of tubercles, mesialmost row consisting of 7 or 8. First pleopod terminating in short, moderately arched central projection, its tip directed somewhat caudoproximally at about 110 degrees to main shaft of appendage and bearing distinct subapical notch; mesial process robust and mammiform, extending beyond tip of central projection; caudal knob absent. Mesial ramus of uropod almost always lacking distomedian and distolateral spines. Color pinkish orange with tan to brown areas particularly evident on dorsal surfaces of distal part of merus, on carpus, and on mesial half of palm of chela; abdominal terga without stripes or bands. Female with first pleopod present.

HOLOTYPIC MALE, FORM I.—Body subovate, compressed (Figure 57a,j). Abdomen narrower than cephalothorax (9.1 and 12.8 mm); greatest width of carapace slightly greater than depth at caudodorsal margin of cervical groove (12.8 and 12.0 mm). Areola linear, lacking punctations in narrowest part, length 41.5 percent of total length of carapace (46.9 percent of postorbital carapace length). Rostrum slightly asymmetrical with convergent, thickened margins, contracted more abruptly sinistrally than dextrally into short acumen, base of which not clearly set off from remainder of rostrum; apex reaching slightly beyond midlength of penultimate podomere of antennular peduncle; dorsal surface of rostrum deeply concave, weakly punctate but with transverse striae in basal part. Subrostral ridges moderately strong and evident in dorsal aspect to base of acumen. Postorbital ridges weak, lacking tubercles or spines cephalically and not markedly swollen caudally. Suborbital angle obsolete, cephalic margin of carapace broadly rounded in area usually occupied by angle; branchiostegal spine rudimentary. Cervical spine represented by small tubercle scarcely larger than those in hepatic region. Carapace punctate dorsally and granulate laterally with tubercles in anteroventral branchiostegal region and in cephalic hepatic region. Abdomen shorter than carapace (22.8 and 27.5 mm), pleura (Figure 39k) short, truncate ventrally and rounded caudoventrally. Cephalic section of telson with single fixed spine in each caudolateral corner; usual paired incisions shallow and transverse suture not evident (Figure 39m.) Uropod with proximal podomere lacking spines; mesial ramus with well-developed submedian ridge devoid of marginal or premarginal spine and lateral margin of ramus entire, lacking lateral spine.

Cephalomedian lobe of epistome (Figure 57g) subrhomboidal, narrow, and with cephalomedian projection; margins slightly thickened and elevated ventrally; main body with fovea represented by comparatively shallow depression, epistomal zygoma arched. Ventral surface of proximal podomere of antennular peduncle lacking usual spine or tubercle. Antennal peduncle without spines; flagellum reaching sixth abdominal tergum; antennal scale (Figure 57i) almost 3 times as long as broad, broadest distinctly distal to midlength with mesial margin subangular at base of distal two-fifths, distal spine almost reaching base of ultimate podomere of antennular peduncle. Mesial half of ventral surface of is chium of third maxilliped studded with irregular rows of long stiff setae and with submarginal lateral row of both smaller stiff and plumose ones, few additional setae in area between; distolateral angle subacute.

Right chela (Figure 57l) 2.1 times as long as broad, mesial margin of palm occupying about one-third of its length. Mesial surface of palm with 2 well-defined rows of 7 tubercles each, more lateral row on left chela consisting of only 6 tubercles, row of 3 tubercles adjacent to mesialmost row ventrally; entire ventral surface of palm and mesial half of dorsal surface tuberculate, lateral half of latter punctate; 2 prominent tubercles present ventrally on marginal thickening opposite base of dactyl; lateral surface of chela strongly costate. Both fingers of chela with well-defined submedian longitudinal ridges dorsally and ventrally; opposable margin of fixed finger with row of 7 tubercles (third from base largest) extending along proximal three-fourths of finger, additional large tubercle on lower level slightly proximal to distalmost tubercle of row; opposable margin of dactyl with row of 11 tubercles (left with 9), fourth from base largest, along proximal three-fourths of finger; single row of minute denticles between and distal to tubercles along distal half of both fingers; mesial surface of dactyl with cluster of large tubercles on basal half and row of punctations continuing distally.

Carpus of cheliped with distinct furrow dorsally flanked by setiferous punctations; mesial surface with moderately large tubercle near base of distal fourth, another slightly smaller one immediately proximal to it, and 2 much smaller ones within proximal half; ventral surface punctate and bearing usual 2 marginal tubercles distally and several additional small ones proximomesial to more mesial marginal tubercle. Merus with 4 (left with 2) premarginal tubercles dorsally, ventrolateral row of 8 (left with 6) tubercles, and ventromesial row of 11; podomere otherwise polished and/or punctate. Ventromesial margin of ischium with row of 4 small tubercles.

Ischium of third pereiopod with simple hook extending proximally over basioischial articulation (Figure 57h), opposed by very weak tubercle on basis. Coxa of fourth pereiopod with comparatively small subrectangular, vertically disposed caudomesial boss; that of fifth pereiopod lacking boss but with ventral membrane setiferous.

First pleopod (Figure 57b,d,f) reaching coxa of third pereiopod. (See “Diagnosis” for description.)

ALLOTYPIC FEMALE.—Differing from holotype, other than in secondary sexual characters, as follows: rostrum with margins contracted abruptly at base of triangular acumen; areola obliterated along part of its length; branchiostegal spine absent, not even represented by tubercle; mesial margin of palm of chela with 8 tubercles in mesialmost row and 6 (7 on left) in adjacent one, opposable margin of fixed finger with row of 5 tubercles, that of dactyl with 7 (6 on left); ventromesial row on merus of cheliped consisting of 10 tubercles (12 on left), and ventrolateral row of 7 (10 on left); ischium with ventromesial row of 3 (2 on left) tubercles. (See “Measurements.”)

Annulus ventralis (Figure 57k) deeply embedded in sternum, subequal in length and width, strongly asymmetrical; cephalic region distinctly less calcified than caudal, with hinge action across junction of 2 areas; cephalic area with shallow submedian trough (dextral wall higher than sinistral), its caudal portion curving caudodextrally and with tongue extending beneath high thickened dextral wall, sinus originating there and following usual tilted S-shaped curve, ending on caudal wall in median line. Caudodextral wall inflated (convex) and caudosinistral wall concave. Postannular sclerite about 1.6 times as broad as long, length half that of annulus and width more than half that of latter. First pleopod reaching midlength of annulus when abdomen flexed.

MORPHOTYPIC MALE, FORM II.—Differing from holotype in following respects: shape of rostrum more nearly approaching that of allotype; no trace of branchiostegal spine; mesial margin of palm of left chela with 8 tubercles in mesialmost row and 6 in adjacent row on both chelae; opposable margin of fixed finger with small tuft of plumose setae at base, and with row of 5 tubercles on right and 4 on left; corresponding margin of dactyl with 6 tubercles on both right and left; dorsal surface of merus of cheliped with 3 (right) and 2 (left) preapical tubercles, ventral surface with mesial row of 10 tubercles and lateral one of 7; ischium of cheliped with only 2 tubercles ventromesially; hook on ischium of third pereiopod poorly developed, adnate, not overreaching basioischial articulation; boss on coxa of fourth pereiopod proportionately not much reduced. (See “Measurements.”)

First pleopod (Figure 57c,e) reaching coxa of third pereiopod; central projection rounded distally, lacking subapical notch, and directed at about 75 degree angle to main shaft of appendage; mesial process less inflated and less constricted apically than in holotype.

COLOR NOTES (Figure 38f).—Basic color of body pale orange tan with darker tan markings. Rostrum with paired narrow longitudinal stripes immediately mesial to postorbital ridges, and subrostral ridges light orange tan. Remainder of cephalic region dark tan except for cream marginal antennal and mandibular regions, light transverse band across base of postorbital ridges, and paired light oval patches over posterior gastric region short distance cephalic to cervical groove. Branchiostegites pale tan, tinged with red dorsally and fading to cream ventrally; cephalic and caudal triangular parts of areola suffused with dark tan. Abdomen with cephalic part of tergum of first abdominal segment almost brown and succeeding terga with dorsal part suffused with dark tan extending onto cephalic part of telson; lateral portions of terga and much of pleura pale orange, latter with cream spot encompassing part of margin of each. Uropods and caudal part of telson cream. Antennular and antennal peduncles orange tan, flagella tan. Cheliped more orange than tan basically, with dark tan to brown reticulate markings on dorsal surfaces of distal part of merus, mesial half of carpus, and mesial half of palm of chela. Remaining pereiopods pinkish orange suffused with tan on merus and carpus, and ventral surface of body pinkish cream.

Measurements (mm)

TYPES.—The holotypic male, form I, allotypic female, and morphotypic male, form II (numbers 116966, 146649, and 146650, respectively), are deposited in the National Museum of Natural History, Smithsonian Institution, together with the paratypes comprising 2I, 1II, 8, 3j, and lj.

TYPE-LOCALITY.—Roadside ditch 15.4 miles east of Irwinton, Wilkinson County, Georgia, on State Route 57, where specimens were dug from complex burrows in sandy clay soil.

RANGE.—Known from only 4 localities on the Fall Line Hills District in the Oconee Basin of Laurens and Wilkinson counties, Georgia.

GEORGIA SPECIMENS EXAMINED.—I have examined 18 specimens from the following localities. Laurens County: (1) roadside ditch 2.6 mi NW of St Rte 338 on US Hwy 441 (10.7 mi SW of Court House in Dublin), 2, 1j, 20 Jun 1975, D. J. Peters, J. E. Pugh, HHH, collectors; 1I, 1II, 1, 21 Apr 1977, C. E. Carter, JEP, HHH. Wilkinson County: (2) type-locality, 1, 1II, 1, 26 Apr 1966, E. T. Hall, Jr., HHH; (3) roadside ditch 8.1 mi E of Irwington on St Rte 57, 1I, 26 Apr 1966, ETH, HHH; (4) roadside ditch 2.1 mi E of Toomsboro on St Rte 57, 5, 3j, 3 Apr 1978, R. J. Dubois, DJP, JEP, HHH.

VARIATIONS.—Most of the variations noted are minor ones involving numbers of tubercles on a podomere of the cheliped, and the only ones observed that are not pointed out in the descriptions of the primary types are rows of 10 tubercles on the opposable margins of both fingers in one of the males and the presence on the ischium of the cheliped of only a single tubercle ventromesially. The carpus of the right cheliped of one of the largest females has a row of four spines on the mesial surface. Most of the specimens possess spines on the basal segment of the antennular peduncle. A first form male is the only specimen in which there exists a small premarginal spine at the end of the median rib of the mesial ramus of the uropod, and in the same specimen, as well as in others, the telson is more deeply incised at the level of the base of the lateral spines than in the holotype. One of the first form males lacks virtually any trace of the tubercle on the basis of the third pereiopod opposing the ischial hook. No variation worthy of note is evident in the first pleopod of the first form males. The allotype and the second form male are the only specimens that possess a distolateral spine on one of the pairs of mesial rami of the uropods. The postannular sclerite is distinctly small in proportion to the annulus ventralis in the paratypic females.

SIZE.—The largest specimen available is a male, form I, in which the carapace length is 34.1 (postorbital carapace length 30.4) mm. The smallest first form male has corresponding lengths of 25.6 and 22.8 mm. No females with eggs or young have been observed.

Cambarus (D.) truncatus

E Ankylocythere tiphophila (Crawford, 1959:173): Wilkinson (Hart and Hart, 1974:33)

Cambarus (Depressicambarus) truncatus Hobbs

Cambarus (Depressicambarus) truncatus Hobbs, 1981:140, figs. 23b, 38f, 39k, m, 41, 57, 206.

TYPES.—Holotype, allotype, and morphotype, 116966, 146649, 146650; paratypes, USNM.

TYPE LOCALITY.—Roadside ditch 15.4 miles (24.6 km) east of Irwinton, Wilkinson County, Georgia, on State Route 57.

RANGE.—Known from only four localities on the Fall Line Hills District in the Oconee Basin of Laurens and Wilkinson counties, Georgia.

HABITAT.—Burrows (primary burrower).

Cambarus.—Hay, 1902a:232.

Cambarus truncatus, the Oconee burrowing crayfish, is a species of crayfish in the family Cambaridae. It is found in North America.

The IUCN conservation status of Cambarus truncatus is "NT", near threatened. The species may be considered threatened in the near future. The IUCN status was reviewed in 2010.