Cambarus ocoeensis Thoma & Williams, 2025, sp. nov.
Creators: name: Thoma, Roger F.
name: Williams, Bronwyn W.
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Cambaridae
Cambarus
Cambarus ocoeensis

description: Cambarus ocoeensis sp. nov.
(Figs. 1, 3, 4, 5, Table 3)
Type material. OSUMC #10897 (Holotype MI), # 10898 (Allotype F), # 10896 (Morphotype MII), 10899 (Paratypes 4 MI, 3 MII, 5 F, 4 F ovig.), Tennessee, Polk Co., Rogers Branch upstream US Rt. 64 bridge, 10.7 km NW of Ducktown, 6.4 km SE of Archville 35.08286°N, 84.48927°E, RFT & Jim K. Grow, 4/15/21.
Other material examined. Tennessee, Polk Co., OSUMC #8428, 1 MI, 1 M-juv, Little Caney Branch of Ocoee River east of Greasy Creek, upstream US Rt. 64, 4.3 km SW of Archville, 16.7 km NW of Ducktown, 35.09834°N, 84.54987°E, Roger F. Thoma (RFT), Lon E. Hersha (LEH), 5/25/11; OSUMC #8439, 1 MI, Right Prong Caney Creek upstream US Rt. 64, 3.9 km SSE of Archville, 15.6 km NW of Ducktown, 35.099°N, 84.53677°E, RFT & LEH, 5/26/11; OSUMC #8478, 5 MII, 5 female (F), 1 F-juv, Rogers Branch upstream US Rt. 64 bridge, 10.7 km NW of Ducktown, 6.4 km SE of Archville, 35.08286°N, 84.48927°E, RFT & LEH, 6/27/11; OSUMC #8481, 5 MII, 6 F, 1 F-juv, Gassaway Creek upstream US Rt. 64, 10.3 km NW of Ducktown, 7.1 km SE of Archville, 35.0777°N, 84.48505°E, RFT & LEH, 6/27/11; OSUMC #8483, 5 MII, 6 F, 1 M-juv, Rock Creek upstream US Rt. 64, 8.0 km NW of Ducktown, 9.2 km SE of Archville, 35.06843°N, 84.46149°E, RFT & LEH, 6/27/11; OSUMC #8486, 1 MII, 6 F, 6 m-juv, 3 F-juv, Rock Creek upstream US Rt. 64, 8.0 km NW of Ducktown, 9.2 km SE of Archville, 35.06609°N, 84.46069°E, RFT & LEH, 6/27/11; OSUMC #8496, 4 MII, 4 F, 3 M-juv, Brush Creek below US Rt. 64 bridge, 4.7 km W of Ducktown, 7.8 km NW of Copperhill, 35.0360°N, 84.4352°E, RFT & LEH, 6/28/11; OSUMC #8498, 2 MII, 4 F, 3 M-juv, 8 F-juv, unnamed tributary of Brush Creek below US Rt. 64 bridge and adjacent railroad track, 4.0 km W of Ducktown, 7.3 km NW of Copperhill, 35.03581°N, 84.42705°E, RFT & LEH, 6/28/11; OSUMC #8864, 1 F, 2 M-juv, 4 F-juv, Left Prong Caney Creek at TNDOT Corridor K Alternative 9 crossing (hike in), 3.17 km SSW of Archville, 16.81 km E of Ocoee, 35.10471°N, 84.53536°E, RFT & Max A. Luehrs, 9/19/12; OSUMC #8866, 1 MI, 5 F, 1 M-juv, 3 F-juv, Gassaway Creek upstream US Rt 64 bridge and at TNDOT Corridor K Alternative 9 crossing, 7.05 km SE of Archville, 21.91 km ESE of Ocoee, 35.07861°N, 84.48407°E, RFT & Max A. Luehrs, 9/19/12; OSUMC #8869, 3 MI, 2 MII, 2 F, 5 M-juv, 2 F-juv, Rogers Branch approx. 150 m upstream US Rt. 64 at TNDOT Corridor K Alternative 9 crossing, 6.40 km SE of Archville, 21.37 km ESE of Ocoee, 35.08329°N, 84.48845°E, RFT & Max A. Luehrs, 9/20/12.
Diagnosis. Body pigmented; eyes well developed. Rostrum acuminate, with margins only slightly thickened and devoid of marginal spines or tubercles at RBMT. Carapace with areola 2.5–4.1 times as long as wide and comprising 32.4–37.2% of entire length of carapace (40.6–47.2 percent of postorbital carapace length) and bearing 5–7 punctations across narrowest part; usually 2 small cervical tubercles present, cervical spines lacking; suborbital angle acute; postorbital ridge terminating anteriorly in very small spine especially in younger specimens. Antennal scale approximately 2.2 times as long as wide, broadest at mid-length. First pereopod chela not strongly depressed, normally 1 row of tubercles along mesial margin of palm, mesial most row consisting of 6–9 (mode 8); lateral margin of palm not costate, both fingers with moderately defined longitudinal ridges dorsally, either lacking or very little lateral impression present. Male with basis of third pereiopod bearing small eminence opposing hook on ischium. First pleopod of MI with terminal elements extending slightly beyond umbo (Fig. 1F): central projection slightly tapering distally, recurved at approximately 110° to main shaft of appendage, and bearing conspicuous subapical notch; mesial process somewhat inflated, acute, and extending caudolaterally approximately equal to tip of central projection at angle of about 90° to main shaft. Female with annulus ventralis sub-symmetrical, shallowly embedded in sternum. First pleopod present.
Description. Holotypic male, MI. Body subovate, depressed (Fig. 1A). Carapace maximum width greater than depth (12.1 mm). Areola 3.5 times as long as wide, moderately punctate, 5 punctations across narrowest part. Anterior section of carapace 1.9 times as long as areola, length of latter 34.6% entire length of carapace. Rostrum with slightly thickened convergent margins, devoid of marginal spines or tubercles at RBMT, tapering gradually from base to level of distal end of basal segment of antennular peduncle, from there angled at 45° and forming acute tip at median of penultimate antennomere of latter. Dorsal surface of rostrum concave, densely punctate especially basally. Postorbital ridge short, not strongly elevated, grooved dorsolateral, and terminating without tubercle. Subrostral ridge moderately developed. Suborbital angle obtuse. Branchiostegal spine very small. No cervical spine, replaced by 1 weak tubercle, one other smaller tubercle dorsal. Carapace punctate dorsally, with polished area in gastric region, and granulate laterally; granules largest on hepatic region and in anteroventral branchiostegal region.
Abdomen as long as carapace (28.7 and 28.6 mm), narrower than thorax (12.9 and 14.5 mm, respectively); pleura 3–5 of moderate length, straight ventrally and with caudoventral extremity formed by 90° slightly rounded angle.
Telson anterior section with 2 spines in each caudolateral corner.
Uropodal protopod with distal spine on each lobe; mesial ramus with weak sub-median ridge terminating in short pre-marginal spine.
Epistome anteromedian lobe (Fig. 1H) subtriangular with rounded edges, anterolateral margins thickened; main body with shallow median fovea; epistomal zygoma moderately arched.
Antennule with ventral surface of proximal antennomere with minute spine at base of distal one-third.
Antennal peduncle with minute spine on lateral surface of basis and lacking tubercle on ventral surface of ischium; antennal scale (Fig. 1E) approximately 2.6 times as long as wide, broadest at mid length, its mesial margin rounded, lacking angles, and its distal spine reaching end of ultimate antennomere of antennular peduncle.
Third maxilliped with ventral surface of ischium with clusters of long stiff setae throughout and submarginal lateral row of equal size; distolateral extremity angular.
Right chela (Fig. 1I) about 2.2 times as long as broad; mesial margin of palm constituting 29% total length, with row of 6 tubercles subtended dorsally by another row of 5: on palm otherwise punctate, without other tubercles. Both fingers with moderately developed dorsal sub-median longitudinal ridges, flanked by setiferous punctations. Fixed finger not costate laterally; opposable margin of finger, from base, with 2 small, 1 large, 2 small, 1 larger, and 2 very small tubercles. Narrow band of minute denticles extending distally from level of sixth tubercle to corneous tip of finger. Opposable margin of dactyl, from base, with 1 larger, 2 smaller, 1 slightly larger, and 6 smaller tubercles decreasing in size. Single row of minute denticles extending distally from sixth tubercle from base; mesial margin of dactyl tuberculate along proximal one-third and bearing row of setiferous punctations along distal two-thirds. Carpus with moderately deep, slightly oblique longitudinal furrow running dorsal full length, flanked by punctations; mesial surface with prominent spine near distal third and smaller spine proximally, larger spine lacking additional small tubercle at proximoventral base; ventral surface with 1 tubercle on distal margin. Merus with 2 subdistal tubercles dorsally, mesial and lateral surface smooth, ventromesial row of 9 spinose tubercles and ventrolateral margin with 2. Mesial margin of ischium with row of 4 small spinous tubercles.
Third pereiopod ischium with simple hook, overreaching basioischial articulation, opposed by small eminence on basis (Fig. 1G). Fourth pereiopod coxa with vertically disposed caudomesial boss; that of fifth without boss, its ventral surface membranous.
First pleopods (Fig. 1B, C) contiguous at bases and reaching coxae of third pereiopods; both terminal elements recurved at angle greater than 90° to main shaft. Mesial process inflated, quickly tapering distally to acute tip directed caudolaterally, upturned at end; central projection, widest at base, more strongly recurved than mesial process and with moderate subapical notch.
Allotypic female. Differing from holotype, other than in secondary sexual characters, as follows: chela 75% of carapace length; mesial margin of palm of left chela with 8 tubercles in mesial most row subtended dorsolaterally by row of 4 very small tubercles; opposable margin of fixed finger with 3 smaller tubercles at base, opposable margin of dactyl with row of 10 similar sized tubercles decreasing in size distally; ventral surface of merus with lateral row of 3 spinous tubercles. Antennal scale length 2.1 times width. Eye diameter 46% of rostrum width at level of eyes. Abdomen width 74% of length.
Annulus ventralis (Fig. 1F) rather shallowly situated in sternum, asymmetrical, tongue running from right to left, with left side more rounded than right, width 86% of length; anterior half with median longitudinal furrow flanked by paired narrow ridges, and prominent subangular ridge forming caudal wall; sinus originating in caudal portion of median furrow, and, extending caudally for short distance, turning sinistrally at right angle before making hairpin turn and crossing to dextral side of median line; from there sinus curving caudally in gentle arc across caudal ridge and terminating on caudal face of latter almost on median line. Postannular sclerite slightly more than half width of annulus and about one-third as wide as long; surface without ornamentation. First pleopod extending anteriorly to anterior margin of annulus when abdomen flexed.
Morphotypic male, Mll. Differing from holotype in following respects: areola with 6 punctations across narrowest part; both chelae regenerated and not detailed herein. Antennal scale 2.4 times width. Two very small cervical spines. Areola width almost 38% of length. Antennal scale length 1.8 times length.
First pleopod (Fig. 1J) with terminal elements directed caudally at right angle to main shaft of appendage; central projection broadly rounded apically and extending about as far caudally as distally directed subacute apex of mesial process.
Size. MI (n = 7) mean TCL 25.3 mm, range 21.8–30.8 mm (PCL 16.8–24.8 mm). MII (n = 15) mean TCL 23.9 mm, range 20.7–29.3 mm (PCL 15.8–23.2 mm). Female (n = 24) mean TCL 24.08 mm, range 19.4–30.7 mm (PCL 15.5–24.8 mm). The largest specimen examined was a MI, TCL 30.8 mm (PCL 24.8 mm).
Color. Carapace and abdomen slightly mottled. Cambarus ocoeensis sp. nov. (Fig. 3) carapace ground color brown; lateral margins of carapace a darker brown. Hepatic and antennal region of carapace punctuated with lighter brown tubercles. Postorbital ridge, rostrum margins and acumen brown. Anterior section of carapace immediately anterior to and including cervical groove brown; mandibular abductor scars not noticeably demarcated. Lateral margin of antennal scale suffused with slight greenish hue. Antennal flagellum and antennules greenish brown, with olivaceous hue. Dorsal surface of chelae greenish brown to olivaceous coloration basely and distally. Tubercles on opposable surfaces of fingers yellow. Ventral surface of chelae cream or tan. Dorsal surface of carpus greenish brown, or brown; carpus spine brown. Distalmost podomeres of pereopods light blue with proximal podomere grading to light brown. Dorsal and dorsolateral surface of abdomen same colors as carapace; abdomen lacking dorsal stripe. Uropod same colors as abdomen. Ventral surface of abdomen and carapace cream. Dorsal ridge of MI gonopod central projection amber; body of central projection, gonopod, and mesial process tan. MII gonopod and all associated processes cream.
Type locality. Rogers Branch (a really nice name) tributary to Ocoee River upstream US Rt. 64 bridge, Tennessee, Polk County, 35.08286°N, 84.4893°W.
Disposition of types. The holotype, allotype, morphotype and paratypes are deposited in The Ohio State University Museum of Biological Diversity Crustacean collection (OSUMC #10897, # 10898, # 10896, 10899 respectively).Additional paratypes are deposited in the North Carolina Museum of Natural Sciences Non-Molluscan Invertebrates Collection (NCSM 96038, 96039), Raleigh, NC and the Invertebrate Zoology Collection, National Museum of Natural History, Smithsonian Institution, Washington D.C. (USNM 1746096, 1746097).
Geographic range. Cambarus ocoeensis, sp. nov. (Fig. 3) is currently known only from streams entering the Ocoee River from the north side of the river in the Southern Medisedimentary Mountains of Tennessee (Fig. 3). Cambarus ocoeensis sp. nov. is the dominant tertiary burrower in the first and second order streams of the area. Note that the species was not recovered from the Goforth Creek drainage despite sampling efforts in several first and second order streams in the system. While the southern tributaries of the Ocoee River were not sampled in this study, from USNM (six lots, 23 specimens) no specimens of C. ocoeensis sp. nov. were observed.
Habitat and life history. Cambarus ocoeensis sp. nov. is restricted to first and second order headwater streams. The species is found under instream slab rocks and has not been found burrowing into stream banks. Records of the species only exist for April, May, June, and September. We observed MI in April, May, and September. Four ovigerous females have been observed in April. Amplexus has not been observed. No information for feeding habits or lifespan is available.
Conservation status. We suggest Cambarus ocoeensis sp. nov. be listed as Threatened (T) using the American Fisheries Society criteria (Taylor et al. 2007), assigned a G1 ranking using the Faber-Langendoen (2009) global conservation criteria for conservation listing, and listed as Vulnerable (VU D2) using the International Union for the Conservation of Nature (IUCN 2001) criteria. The species has an exceedingly narrow distribution; it is currently known to occupy only 19 km 2. Consequently, C. ocoeensis sp. nov. is highly vulnerable to environmental and human-mediated perturbation. A major road improvement project is scheduled for the U.S. Rt. 64 corridor in the Ocoee River Gorge area. The project could have negative impacts on the six known populations of C. ocoeensis sp. nov. by increasing sedimentation and releasing iron oxide from abundant shale bedrock layers in turn elevating the proposed classification to Endangered. An additional impact could be realized in the form of wild boar, Sus scrofa Linnaeus, 1758, populations in the area. During fieldwork efforts several streams were observed to have been impacted by wild boar feeding activities that had removed almost all resident crayfish. Given its restricted range and potential threats, we strongly suggest the status of Cambarus ocoeensis sp. nov. be reviewed by State and Federal officials.
Crayfish associates. Cambarus ocoeensis sp. nov. has been collected with Cambarus parvoculus Hobbs & Shoup, 1947, Cambarus aff. bartonii Fabricius, 1798, Cambarus acanthura Hobbs, 1981, Cambarus latimanus Le Conte, 1856, and Cambarus nodosus Bouchard & Hobbs, 1976.
Variation. Minimal morphological variation has been observed in this narrowly distributed species.
Etymology. The epithet ocoeensis references the species’ range, which is limited to the Ocoee River Basin.
Common name. Ocoee Crayfish. The common name is in reference to the Ocoee River.
Relationships and comparisons. Cambarus ocoeensis sp. nov. (Fig. 1) is morphologically most like Cambarus hiwasseensis and Cambarus parrishi Hobbs, 1981. It can be differentiated from C. hiwasseensis as follows. The chelae of C. ocoeensis sp. nov. are generally less sculpted, usually with one row of 6–9 palmer tubercles; if a second row is present, it is very weakly developed, consisting of 6 or fewer tubercles. In contrast, the chelae of C. hiwasseensis exhibit 2 rows of tubercles, the first row with 6–10, and the second row well-developed with 7–8. The lateral margin of the chelae of C. ocoeenis sp. nov. is not costate, and the lateral impression is weak at most but usually absent. Areola length of C. ocoeensis sp. nov. is 2.5–4.1 times greater than width, with 5–8 punctations at the narrowest part, whereas the areola length is 1.9–3.7 times greater than width in C. hiwasseensis with 8–10 punctations. Size at maturity is generally smaller for C. ocoeensis sp. nov.; MI TCL ranges from 21.8 to 30.9 mm compared with 24.6 to 40.0 mm for C. hiwasseensis. The antennal scale of C. ocoeensis sp. nov. is broadest at the midpoint, whereas the antennal scale of C. hiwasseensis is broadest distal to mid-length. The annulus ventralis of female C. ocoeensis sp. nov. is asymmetrical having one curved/rounded margin (either dextral or sinistral) and the opposite straight edged, forming an approximately 45° angle at its lateral point (Fig. 1I). In C. hiwasseensis the annulus ventralis is symmetrically rhomboid, with no curved edge sculpturing.
Cambarus ocoeensis sp. nov. differs from C. parrishi in the following ways. The RBMT of C. ocoeensis sp. nov. tapers anteriorly from base, gradually decreasing in thickness, terminating in a distinct deflection point of an approximately 45° angle at which point the edges converge more rapidly to the tip of the acumen; the rostrum lacks tubercles or spines. In contrast, the rostrum of C. parrishi is broadly dagger-shaped, with two small marginal tubercles at the base of the acumen. In addition, the annulus ventralis in C. parrishi is symmetrically rhomboid.
Most species in the genus Cambarus differ from C. ocoeensis sp. nov. in having one or more of the following character states: cervical spines, rostral spines/tubercles, closed or narrow areola (<3 punctations), 2+ strongly developed rows of palmar tubercles, and/or an acuminate rostrum. Alternatively, some species will differ from C. ocoeensis sp. nov. through the absence of the following character states: pigmented eyes, chelae fingers with easily discerned dorsal ridges, and tubercles of varying size on their opposable margins, and/or antennal scale widest at midpoint.
While physical similarities of C. ocoeensis sp. nov. to some members of the C. bartonii species complex are minimal, the phylogenetic relationship is clear (Fig. 5, Table 2). This speaks to the high morphologic variability present in the C. bartonii species complex. The C. bartonii complex in turn intergrades into the C. howardi species complex. Within this broader C. bartonii - howardi complex, C. ocoeensis sp. nov. shares an acuminate rostrum and general chelae form with C. howardi sensu stricto. Cambarus howardi sensu lato encompasses several morphological variants (personal observations by RFT and BWW), making it difficult to identify a single set of characters that distinguish all forms within the complex from C. ocoeensis sp. nov. Rostral acumination can be used to distinguish C. ocoeensis sp. nov. from many members of the C. howardi complex, as C. howardi generally possesses a more strongly acuminate rostrum. While spines are highly distinctive for many C. howardi variants, they are not present in all and absent in C. ocoeensis sp. nov. In addition, most C. howardi forms have a densely punctate carapace, but C. ocoeensis sp. nov. also has carapace punctation of a similar degree. Considerable work is needed to understand, and tease apart, the diversity and variation subsumed within the C. howardi group.
description: Published as part of Thoma, Roger F. & Williams, Bronwyn W., 2025, Cambarus ocoeensis, a new species of crayfish (Decapoda: Cambaridae) from the Ocoee River Basin of Tennessee, USA, pp. 106-118 in Zootaxa 5618 (1) on pages 109-115, DOI: 10.11646/zootaxa.5618.1.7, http://zenodo.org/record/15217478