Cambarus (Depressicambarus) clairitae Schuster and Taylor

Schuster, Guenter A. & Taylor, Christopher A., 2016, Cambarus (Depressicambarus) clairitae, a new species of crayfish (Decapoda: Cambaridae) from Alabama with a review of the halli Group in the subgenus Depressicambarus, Zootaxa 4193 (2), pp. 332-346 : 333-339

Cambarus (Depressicambarus) clairitae Schuster and Taylor , new species

( Figures 1–9 , Table 1 )

Diagnosis. Body and eyes pigmented. Rostrum slightly excavated, terminating in short acumen not distinctly set off from rest of rostrum ( Figure 3 H); no median carina present. Rostral margins thickened; margins straight, distinctly converging, not terminating in spines or tubercles ( Figures 1 & 7 ). Margins of acumen not as thickened as rest of rostrum. Rostrum usually with subrostral spines or rounded tubercles. Areola 37.7–40.5% (n=23, x =39.2, SD=0.9) of TCL and 45.0–48.4% (n=23, x =46.7, SD=1.0) of PCL; narrowest at midpoint, 4.1–7.3 (n=23, x =5.4, SD=0.8) times as long as wide, with four to six punctuations (n=23, x =4.6, SD=0.7) across narrowest part. One corneous well developed cervical spine on each side of carapace. Postorbital ridge well defined, ending in corneous spines ( Figure 3 H). Suborbital angle obtuse. Branchiostegal spine well developed; branchiostegal sclerite covered with large rounded tubercles laterally, extending towards dorsal surface. Antennal scale widest at distal 2/3 of scale, scale width goes into length 2.2–3.1 (N=23, x =2.6, SD=0.2) times; thickened lateral margin terminating in large corneous spine ( Figure 3 J). Ischia of third pereiopod of males with hooks; hooks overreaching basioischial articulation in form I males only.

Chela with two rows of tubercles along mesial margin of palm ( Figure 3 K), usually 5–8 (n=15, x =6.3, SD=0.9) in mesial most row, most proximal two sometimes fused; 4–7 (n=14, x =6.1, SD=0.9) in dorsomesial (second) row, palm with deep furrow lateral to second row of tubercles. Dactyl length is 1.6–2.0 (n=18, x =1.8, SD=0.1) times longer than palm length. Total length of chela is 1.6–1.9 (n=17, x =1.7, SD=0.1) times longer than dactyl length. Distomedian spine on the ventral surface of the carpus large and corneous usually with proximolateral tubercle or spine.

Mandible with serrated incisor region. Cephalomedian lobe of epistome subtriangular; epistomal zygoma ridged and arched ( Figure 3 G).

Gonopods of MI symmetrical, extending to posterior edge of bases of third pereiopods when abdomen flexed. Central projection corneous without subapical notch; mesial process non-corneous, extending beyond central projection. Gonopod of MII non-corneous, extending to posterior edge of bases of third pereiopods when abdomen flexed; central projection broadly rounded, mesial process bulbous and subequal in length to central projection; both elements tapering to rounded tips ( Figures 3 D & E). Annulus ventralis immovable, subtriangular; cephalic end with median trough, fossa centered; sinuate sinus running from center of annulus to bottom edge ( Figure 3 I). Annulus ventralis of some females may be mirror image of Figure 3 I).

Description of the holotype male, form I. Cephalothorax ( Figure 3 H) TCL 31.9 mm and PCL 27.5 mm; dorsoventrally compressed; maximum width greater than maximum height (11.8 and 16.8 mm, respectively). Abdomen somewhat narrower than cephalothorax (13.2 and 16.8 mm, respectively). Areola 12.7 mm long, 2.5 mm wide ( Figure 3 H). Cephalic portion of cephalothorax 2.5 times longer than areola; areola comprising 46.2% of PCL (39.8% of TCL). Surface of carapace punctate dorsally ( Figure 3 H), laterally covered with many large rounded tubercles ( Figures 3 A & H). Rostrum ( Figure 3 H) broadest at base (4.4 mm), 7.2 mm long; sides gradually converging to tip of acumen, acumen not distinctly set off; margins distinctly thickened, but slightly thinned at acumen; acumen anteriorly with rounded, upturned tubercle; acumen length 2.5 mm; subrostral ridge with well developed spine. Postorbital ridge ( Figure 3 H) strong with large spine anteriorly. Suborbital angle ( Figure 3 A) obtuse and rounded; branchiostegal spine moderate. Cervical spine well developed.

Cephalic lobe of the epistome ( Figure 3 G) broadly rounded; main body of epistome rectangular in broad outline, zygoma strongly arched. Antennal scale ( Figure 3 J) 5.0 mm long and 2.1 mm at widest point; mesial margin with row of long, flexible setae.

Third maxilliped well developed, ventral and lateral sides of basal segments covered with long flexible plumose setae in two rows; distal segments also with long setae, but not as dense.

Cephalic section of telson with one movable and one immovable spine in right caudolateral corner, left caudolateral corner with one immoveable spine and two moveable spines. Protopod of uropod with spine extending over endopodite. Caudal margin of cephalic section of exopodite with numerous fixed spines (n=11). Cephalic section of exopodite with median ridge, caudolateral corner with spine. Lateral margin of endopodite terminating in spine; endopodite with median ridge terminating in premarginal spine. Dorsal surfaces of telson and uropods covered with short, branched setae.

Right chela ( Figure 3 K) total length 31.3 mm, dactyl length 17.4 mm, dactyl and propodus each with strong dorsomedian longitudinal ridges. Palm width greater than palm length (14.4 and 10.4 mm, respectively); no plumose beard of setae along palm mesial margin; mesial margin of palm with a row of 7 tubercles, a second dorsal row of 6 tubercles and scattered elongated tubercles near deep furrow on dorsal surface of palm. Opposable margin of dactyl with 12 round tubercles, basal 6 of nearly equal size, last 6 progressively smaller distally. Opposable margin of fixed finger with 8 large tubercles, third and seventh tubercles enlarged, seventh tubercle slightly off set, small denticles in between distal three tubercles to base of terminal spur. Carpus of cheliped with curved dorsal furrow, one large dorsomesial spine and a number of small rounded tubercles along mesial margin. Hook on ischium of third pereiopod only, overreaching basioischial articulation. Coxae of fourth pereiopod with boss.

First pleopods symmetrical at base, total length 7.7 mm; terminal elements as described in “Diagnosis” ( Figures 3 B, C & F; 6A).

Description of allotype female. Differs from holotype in the following: Cephalothorax TCL 32.0 mm and PCL 27.0 mm; maximum width greater than maximum height (17.4 and 12.6 mm, respectively). Abdomen narrower than cephalothorax (15.8 and 17.4 mm, respectively). Areola 12.8 mm long, 2.5 mm wide. Cephalic portion of cephalothorax 1.5 times longer than areola; areola comprising 47.4% of PCL (40.0% of TCL). Rostrum widest at base (5.4 mm), 8.4 mm long. Antennal scale 5.5 mm long, 2.0 mm at widest point. Right chela total length 29.1 mm, dactyl length 15.5 mm; palm width greater than palm length (12.3 and 9.7 mm, respectively). Opposable margin of dactyl with 12 tubercles with basal 8 about same size. Opposable margin of fixed finger with 9 tubercles, fourth and eighth enlarged, eighth off set. No hook on ischium of third pereiopod. Annulus ventralis ( Figure 1 I) as described in “Diagnosis.” Cephalic section of telson with one movable and one immovable spine in each caudolateral corner.

Description of the morphotype male, form II. Differs from holotype in the following: Cephalothorax TCL 25.2 mm and PCL 20.0 mm; maximum width greater than maximum height (12.8 and 10.4 mm, respectively). Abdomen narrower than cephalothorax (10.9 and 12.8 mm, respectively). Areola 10.1 mm long, 2.0 mm wide. Cephalic portion of cephalothorax 1.5 times longer than areola; areola comprising 48.3% of PCL (40.1% of TCL). Rostrum widest at base (4.3 mm), 5.8 mm long. Antennal scale 4.8 mm long, 2.0 mm at widest point. Right chela total length 21.8 mm, dactyl length 12.1 mm; palm width greater than palm length (9.3 and 7.0 mm, respectively); Opposable margin of dactyl with 10 round tubercles. Opposable margin of fixed finger with 9 round tubercles, third and eighth enlarged. Hook on ischium of third pereiopod much smaller than on holotype. Gonopod length 6.4 mm ( Figures 3 D & E). Cephalic section of telson with one movable and one immovable spine in each caudolateral corner.

Color. ( Figures 1 , 2 & 4 ). The predominant carapace background color is dark brown to black with large rhomboid golden yellow to light cream yellow spots on the branchiostegites that extend dorsally and laterally. The hepatic region of the carapace dorsally with a large irregular shaped golden to light cream yellow spot just posterior to the rostrum. The postorbital ridges and their anterior spines bright orange to red. The rostral margins are bright yellow to orange; at the base of the rostrum on each side there is a splash of orange to red. In dorsal view each abdominal sclerite brown to black; the anterior portion of the first sclerite black, posterior margin straw to white in color. The telson and uropods much lighter in coloration, ranging from tan to cream. The antennae are light to dark brown.

Dorsally the center region of the chelae with a large brown to black area. Laterally on either side of this darkened area the color lightens dramatically from cream to white. This coloration is extended onto both fingers. The carpus of the cheliped is largely brown to black with a large cream to white spot that mesially forms a straight line which extends ventrally to the margin then expands distally to the anterior margin of the segment. The distal third of the merus is brown to black and the rest of the segment is cream to white. All of the large spines and tubercles of the chelae, except those on the palm and fingers, are bright orange to red. The remaining pereiopods are cream with the distal margins of each segment orange to red in color. Venter of body and all legs cream to white in color. Most setae on the body golden-straw to brown in color.

There is little variation in the actual color pattern in C. clairitae . The greatest variation is in the brightness of the colors ( Figure 4 ). In specimens that are recently molted ( Figure 4 B) the colors are more vibrant, while specimens that have not molted recently are much darker overall and the dark browns go to black ( Figure 4 A). This produces a very distinct contrast with the lighter areas of the body and legs.

Disposition of types. The holotype, allotype, and morphotype are deposited in the Illinois Natural History Survey Crustacean Collection, Champaign, IL as INHS 15446, INHS 15448, and INHS15447, respectively.

Size. The largest specimen in this study was a female having a TCL of 33.7 mm (PCL 28.6 mm). The largest MI had a TCL of 31.9 mm (PCL 27.5 mm). The smallest MI had a TCL of 29.7 mm (PCL 24.7 mm). MIIs ranged in TCL from 24.8–26.1 mm (in PCL 20.2–21.8 mm) while females ranged in TCL from 26.5–33.7 mm (in PCL 22.6–28.6).

Type locality. Gurley Creek, a tributary of Locust Fork in the Black Warrior River drainage, in a long riffle approximately 100 meters upstream of the State Route 79 bridge, Jefferson County, Alabama (33.7942N; - 86.6867). Most of the specimens were collected from under larger rocks in the midst of the riffle.

Range and specimens examined. Cambarus clairitae is currently known only from 5 locations in the Blackburn Fork of the Little Warrior River and Gurley Creek drainages of the Locust Fork drainage in Jefferson and Blount counties, AL. A total of 23 adults was examined for this study: UADC 193.02, 1 Fe : AL, Blount County, Blackburn Fork of Little Warrior River at SR 79 crossing, February 28, 1991, Collectors: R.M. Wood, S.R. Layman, A.M. Simon . MMNS, 2 Fe : AL, Jefferson County, Gurley at Trafford, June 13, 1997, Collectors: Geological Survey . INHS 12035, 2 MI, 1 MII, 2 Fe : AL, Jefferson County, Gurley Creek at SR 79 crossing, October 6, 2011, Collectors : GAS, CAT; INHS 15449, 1 MI, 1 MII, 1 Fe : AL, Jefferson County, Gurley Creek at SR 79 crossing, October 27, 2014, Collectors : GAS, CAT, SWM; INHS 15019, 1 MII: AL, Jefferson County, Gurley Creek at SR 121 crossing, October 27, 2014, Collectors : GAS, CAT, SWM; INHS 15451, 2 MII, 2 Fe : AL, Blount County, Blackburn Fork of the Little Warrior River at CR 15 crossing, October 29, 2014, Collectors : GAS, CAT.

Etymology. Named in honor of our wives Claire Schuster and Rita Taylor, who have supported us faithfully since the beginning. They have endured weeks alone at home while we were in the field or in some museum chasing crayfishes. Without their continued support we would not have been able to follow our research paths. We are forever grateful to them. This honor is a small token of that appreciation.

Habitat and life-history notes. Cambarus clairitae is a stream dwelling crayfish. The known habitats of this species include fast running riffles in Gurley Creek and Blackburn Fork of the Little Warrior River. Within these streams, the species was always collected from under rocks in areas of the streams with depths ranging from 0.1 to 0.5 m. All MIs have been collected in the month of October. No ovigerous females or females carrying young have been collected. No additional life history information is known for this species.

Crayfish Associates. Species that have been collected with C. clairitae include Cambarus obstipus , C. striatus , Orconectes erichsonianus , O. validus , and O. virilis .

Variation. Variation found within the 23 adult specimens examined was minimal for most characters. Characters that showed little variable included the following: 1) Females with first pleopod present but reduced in size; 2) Percentage of areola length by total carapace length; 3) The ratio of antennal scale length by antennal scale width; 4) Eye diameter; 5) MI gonopod length; 6) Annulus ventralis width; 7) The number of palm tubercles in the first and second row. Much of the variation in measurements was due to variation in the sizes of individuals (e.g. carapace, abdomen and areola measurements).

Relationships. Based on the overall morphological features of C. clairitae , we assign it to the halli Group in the subgenus Depressicambarus. These features include the shape of the rostrum, the presence of well developed cervical spines and having a wide areola. Cambarus clairitae appears to be most closely related to C. englishi . Both species lack a distinct subapical notch on the central projection ( Figures 5 C & G), best seen in mesial or lateral view. There are a number of other morphological differences between C. clairitae and C. englishi ( Figures 5 A–D & 5E–H). See “Review of the halli Group” for comparisons between C. clairitae and the other members of the halli Group.

Common name. The suggested common or vernacular name for this species is the Zebra Crayfish because of its very distinct and contrasting light and dark coloration. This is especially evident on the dorsum of the abdomen where it resembles the stripes of a zebra.

Conservation status. Although extensive collecting has been done in the drainages in the vicinity of the known locations for this species in Blount and Jefferson counties, no additional populations have been found. Additional fieldwork needs to be done to better assess the distribution and population sizes of this species and its current status. However, based on the criteria of the American Fisheries Society as outlined by ( Taylor et al. 2007) and the system developed by The Nature Conservancy/NatureServe ( Master 1990), we propose that this species, because of its apparent narrow range, be considered Vulnerable (V) with a G3 global ranking. The species should rank as Vulnerable by the International Union for the Conservation of Nature (IUCN) under Criteria D.

Figures

FIGURE 1. Cambarus (Depressicambarus) clairitae n. sp.: Holotype, Jefferson County, AL, dorsal view.

FIGURE 2. Cambarus (Depressicambarus) clairitae n. sp.: Holotype, Jefferson County, AL, lateral view.

FIGURE 3. Cambarus (Depressicambarus) clairitae n. sp.: A. lateral view of carapace; B & C, respectively, mesial and lateral view of terminal end of left gonopod of MI; D & E, respectively, mesial and lateral view of terminal end of left gonopod of MII; F, mesial view of entire left gonopod of MI; G, epistome; H, dorsal view of carapace; I, annulus ventralis; J, antennal scale; K, dorsal view of right chela and carpus of MI. (3 A – C, F – H & K are of holotype; 3 I is of allotype; 3 D – E & J are of morphotype).

FIGURE 4. Color variations of Cambarus (Depressicambarus) clairitae n. sp.

FIGURE 5. Morphological structures of halli Group species. A – D, Cambarus clairitae n. sp. respectively, carapace dorsum, chela dorsum, mesial view of MI gonopod and annulus ventralis; E – H, C. englishi respectively, carapace dorsum, chela dorsum, mesial view of MI gonopod and annulus ventralis; I – L, C. halli respectively, carapace dorsum, chela dorsum, mesial view of MI gonopod and annulus ventralis; M – P, C. obstipus respectively, carapace dorsum, chela dorsum, mesial view of MI gonopod and annulus ventralis.

FIGURE 6. Mesial view of MI gonopod showing angle of recurve of central projection to main axis for each halli Group species. A. Cambarus clairitae n. sp.; B. C. englishi; C. C. halli; D. C. obstipus.

FIGURE 7. Dorsal view of rostrum and acumen of: A. Cambarus clairitae, n. sp.; B. C. englishi.

FIGURE 8. Antennal colors of: A. Cambarus clairitae, n. sp.; B. C. englishi; C. C. halli.

FIGURE 9. Lateral view of extended abdomens showing degree of curvature of posterior margins of abdominal pleurites and notch development between them, for: A. Cambarus clairitae, n. sp.; B. C. englishi; C. C. halli.

Tables

TABLE 1. Measurements (mm) of type specimens of Cambarus clairitae, new species.

Holotype	Allotype	Morphotype
Carapace
Height 11.8	12.6	10.4
Width 16.8	17.4	12.8
Total carapace length (TCL) 31.9	32.0	25.2
Postorbital carapace length (PCL) 27.5	27.0	20.9
Areola length 12.7	12.8	10.1
Areola width 2.5	2.5	2.0
Eye diameter 2.0	2.1	1.8
Rostrum
Width 4.4	5.4	4.3
Length 7.2	8.4	5.8
Chela
Length, mesial margin palm 10.4	9.7	7.0
Width, palm 14.4	12.3	9.3
Length, total 31.3	29.1	21.8
Length, dactyl 17.4	15.5	12.8