Faxonius elix Couch, 2022

Couch, Zachary L. & Hayes, David M., 2022, Description of a new species of crayfish in the genus Faxonius (Decapoda: Cambaridae) from the Lower Ohio River Drainage, with evidence of glacial influence on the distribution of some crayfish species throughout the Ohio River basin, Zootaxa 5165 (3), pp. 365-386 : 376-383

Faxonius elix Couch n. sp.

( Figures. 6 , 7 , 8 ; Table 5 )

Diagnosis. Body and eyes pigmented. Carapace moderately dorsoventrally flattened and typically wider than abdomen, especially in larger individuals. Areola 4.5 times longer than wide at its narrowest point, with room for 2–4 punctations. Cervical spine present, but often reduced or worn in larger individuals. Branchiostegal and hepatic spines absent. Very sparse setae along periopods and caudal ridge. Rostrum broad and shallowly excavated. Rostrum typically two times as long as wide (x =2.2 + 0.215, n=27). Median carina often present in larger individuals. Rostral margins converging slightly along posterior third to half, parallel along anterior half to two thirds. Rostral margins terminating in small spines or tubercles at the base of acumen. Rostrum terminating in pointed acumen. Postorbital ridges parallel. Suborbital angle obsolete. Antennal scale straight along lateral margin, terminating in corneous tip; medial margin rounded with widest point superior to the midpoint. Evenly distributed setae, nearly equal in length to antennal scale width, extend from medial antennal scale margin. Cephalomedian lobe of epistome subcircular to subhexagonal and lacking cephalomedian projection; epistomal zygoma moderately arched.

Chelae with two rows of tubercles along the mesial margin of palm. Longitudinal ridges extend along the chelae dorsal surface with scattered tubercles throughout. Sparse tufts of short setae located along mesial margins of the dactyl. Usually, one spine extending from the mesial margin of the carpus and 1–2 spines extending from the mesial margin of the merus. Hooks on ischia of third pereiopods on Form I males. Mandible with dentate margins (74% of Form I male specimens examined, n=27). First pleopod of Form I male with terminal elements approximately 30% percent of total length (x =31% + 0.019, n=27). Central projection typically longer than mesial process for both Form I and Form II males. Central projection longer than mesial process in 89% of Form I male specimens examined (n=27). Central projection bladelike and curving towards the mesial process. Gonopod with shoulder along the dorsal gonopod margin near base of central projection in 100% of individuals examined (n=27). Annulus ventralis, immovable and subrhomboidal, with a centrally located fossa and a slightly sinuous sinus extending from fossa to caudal margin.

Description of holotypic male, Form I ( Fig. 8 A–D, H, J, K ). Body dorsoventrally depressed with carapace width greater than carapace height (16.9 and 14.4 mm, respectively). Carapace wider than abdomen (16.9 and 14.2 mm, respectively). Total carapace length (32.8 mm) nearly equal to abdomen length (31.4 mm). Postorbital carapace length (27.0 mm) 82.3% of total carapace length. Areola 6.8 times longer (11.6 mm) than wide (1.7 mm) with three punctuations across narrowest part; length of areola 35.3% of total carapace length. Antennal scale straight along lateral margin, terminating in a corneous tip. Medial margin rounded with widest point superior to the midpoint. Right antennal scale 5.9 mm long, 2.5 mm wide. Rostrum densely covered with punctations, excavated, median carina present; margins thickened, distal halves straight and slightly converging, ending in small rounded corneous spines; rostral trough wide, steeply rising towards rostral margins. Acumen terminating in upturned corneous rounded spine and reaching near midpoint of antennular peduncle. Postorbital ridges well developed, terminating in small, rounded corneous spines. Suborbital angle obsolete. Mandible with mesial serrations along incisor region. Cervical spines corneous; branchiostegal areas of carapace densely punctate, dorsal surface scattered with punctations. Telson terminating with one immovable spine in each caudolateral corner. Protopodite of uropod with spine extending over endopodite and spine in caudolateral corner extending over exopodite. Caudal margin of cephalic section of exopodite with numerous fixed spines (n=16). Exopodite with pronounced longitudinal ridge. Lateral margin of endopodite with prominent median ridge terminating in spine; endopodite with prominent median ridge terminating in subterminal spine. Dorsal surfaces of telson and uropods setiferous.

Mesial surface of palm of right chela with two rows of tubercles, seven tubercles in mesial most row and six tubercles in dorsomesial row. Sparse setiferous punctations emanating from around mesial tubercles. Sparse setiferous punctations along mesial and lateral margins of propodus. Dorsal and ventral surfaces of fingers of chela with longitudinal ridges flanked on both sides by rows of setiferous punctations. Opposable margin of propodus with nine well developed tubercles, third through sixth from base nearly equal in length. Opposable margin of dactyl with 14 tubercles of nearly uniform size. Propodus and dactyl with well-developed corneous tips at terminal ends. Carpus with deep furrow dorsally; mesial margin with one large corneous procurved spine at midpoint; ventral surface with two overlapping protuberances. Dorsodistal surface of merus with two tubercles; ventromesial margin with one row of seven tubercles, terminating in two corneous spines, the distal-most spine being the largest; two large tubercles located laterally to the ventromesial margin along the distal end. Ischium with one distal protuberance and one small proximal corneous spine along ventromesial margin. Second and third periopod setiferous, with setae increasing in length and density distally. Fourth and fifth periopods less setiferous. Hook on ischia of third pereiopods only; simple, overreaching basioischial articulation. First pleopod extending to base of second periopod, 41% of total carapace length, partially hidden beneath dense setae originating from the venter of carapace when at rest; shoulder present proximal to central projection; mesial process slightly shorter than central projection. Central projection corneous, subulate and slightly procurved, constituting 30% of total gonopod length. Mesial process 27% of total gonopod length, blade-like, slightly sinuous, reflexed toward central projection, and bluntly terminating.

Description of allotypic female ( Fig 8 G, I ). Differing from the holotype as follows. Postorbital carapace length 80.22% of total carapace length. Areola 5.6 times longer (10.6 mm) than wide (1.9 mm). Right antennal scale 7.0 mm long, 3.0 mm wide. Mesial surface of palm of right chela with two rows of tubercles, eight tubercles in mesial most row and seven tubercles in dorsomesial row. Opposable margin of dactyl with nine tubercles of nearly uniform size. Annulus ventralis as described in Diagnosis.

Description of morphotypic male (MII) ( Fig. 8 E, F ). Differing from the holotype as follows. Postorbital carapace length 80.22% of total carapace length. Areola 6.1 times longer (12.9 mm) than wide (2.1 mm) with two punctuations across narrowest part; length of areola 35.9% of total carapace length. Right antennal scale 5.8 mm long, 2.6 mm wide. Mesial surface of palm of right chela with two rows of tubercles, eight tubercles in mesial most row and seven tubercles in dorsomesial row. Opposable margin of dactyl with nine tubercles of nearly uniform size.

Ischia of third periopods with protuberance on ischia of third pereiopods not overreaching basioischial articulation. First pleopods as described in Diagnosis.

Disposition of primary type. The holotype, allotype, and morphotype are deposited at the National Museum of Natural History , Smithsonian Institution, Washington , D.C. (catalog numbers USNM 1593333 , USNM 1593334 , USNM 1593335 , respectively). Paratypes are deposited in the Branley A. Branson Museum of Zoology at Eastern Kentucky University, Richmond, Kentucky USA .

Type locality. Fern Creek at Feganbush Lane (Kentucky Highway 864) crossing, approximately 150 meters east of the intersection of Feganbush Lane and Fern Valley Road in Louisville , Jefferson County, Kentucky (38.160374 o N, - 85.639214 o W; Figure 9 ). The holotype was collected from under piece of limestone approximately 0.3 x 0.5 meter located in a run. Stream substrates were a mix of bedrock (along the right-descending bank) and large cobble interspersed with gravel and fines (mainly along the left-descending bank). Stream width was approximately 10 meters at the collection site. The right-descending bank and riparian area consisted of a small limestone outcropping while the left-descending bank and riparian area consisted of a mowed and maintained residential site. The collection was made on November 19, 2018, and included the holotype, allotype, and morphotype .

Range. Faxonius elix n. sp. is restricted to the Pond Creek and Abrams Run drainages in Jefferson, Bullitt, and Meade counties, Kentucky. The Pond Creek system is a tributary to the Salt River near its confluence with the Ohio River. Abrams Run is a direct tributary of the Ohio River approximately 5.6 kilometers downstream of the confluence of the Salt River and Ohio River in Meade County. Surveys conducted at stream sites in Indiana and in the Ohio River at the Falls of the Ohio did not produce records of the species. Water depth prevented surveys for the species in the Salt River .

Color. Overall body color ranging from pale and muted grayish green to dark and vibrant orange with tinges of olive. Chelae always tipped in bright orange-red followed posteriorly by a broad band of black often two to three times as broad as the preceding orange band. Periopods often exhibiting tinges of orange along the joint margins. Rostral margins often darker than rostrum. Darker patch located dorsally along the posterior third of the cephalic region of the carapace. Dorsum of thoracic section of carapace lighter than the lateral area of the branchiostegal, except for the dorsal portion of the thoracic section immediately anterior to the caudal ridge. Dorsum of abdomen often with a light central longitudinal band with parallel and adjacent dark longitudinal bands, with bands most pronounced on the three anterior-most terga. Venter light gray to white.

Habitat. Faxonius elix n. sp. is typically encountered in moderate gradient streams that provide surface water throughout the summer. The species is usually observed seeking refuge during daylight hours under natural substrates and detritus, as well as crevices in bedrock, emergent vegetation, and anthropogenic refuse deposits. Urban development of the watershed has altered the habitat for the species over the past 150 years. Many streams harboring populations of F. elix n. sp. have been channelized, relocated, or destroyed ( Figure 10 ). All stream systems where the species was encountered exhibited at least some anthropogenic impact.

Life History. Form I males have been collected in March, April, June, July, August, September, October, and November. Adult Form II males were collected in March, April, May, and June. Males began transitioning from Form I to Form II in early to mid-April. Ovigerous females were observed mid-April through early May. One ovigerous female was collected from Bee Lick Creek in Jefferson County on 28, April 2018 with 146 eggs. Stage I juveniles were typically first observed in late April. Amplexes was observed on one occasion in late September. The smallest Form I male observed had a total carapace length of 11.24 mm; most Form I males had a total carapace length greater than 18 mm.

Etymology. Elix: Latin for ditch or canal; in reference to the significant channelization of streams that has occurred throughout the range of the species.

Suggested Vernacular name. The Mowild Crayfish. In recognition of GoWild Alpha, Inc. for their dedication to conservation of the species.

Crayfish associates. A single unidentified specimen of Cambarus was collected from a site at Abrams Run where specimens of F. elix n. sp. were collected on 24 May, 2008. Procambarus acutus (Giard 1852) and Faxonius immunis ( Hagen 1870) were collected within streams with populations of F. elix n. sp.

Variation. In addition to the already mentioned specimen variability in the diagnosis and color sections, variation in F. elix n. sp. includes the following. Incisor region of the mandible, especially in larger specimens, is smooth to slightly dentate. Median carina, especially in smaller individuals, reduced to absent. Form I males rarely with mesial process equal in length to central projection.

Comparisons. Of Faxonius members found in the central Ohio River basin, F. elix n. sp. is most similar to F. jeffersoni , F. bisectus , and F. margorectus . All of these species are restricted to small Ohio River tributaries in Kentucky and have terminal elements less than 35% of total gonopod length. Faxonius elix n. sp. differs from these species in having a shoulder on the gonopod of Form I males and terminal elements that comprise over 30% of total gonopod length. Additionally, F. elix n. sp. typically has a dentate mandible, which distinguishes it from both F. jeffersoni and F. margorectus . While Faxonius bisectus is similar to F. elix n. sp., the former typically possesses a dentate mandible along the incisor region, the terminal elements of F. bisectus comprise less than 25% of the total gonopod length and the mesial processes diverge laterally.

Relationships. Genetic and morphological analyses yielded confounding results regarding the taxonomic relationship of F. elix n. sp. with its congeners. While the species is most similar to Faxonius jeffersoni morphologically, genetic analyses indicate that the species is genetically identical to published sequences of F. illinoiensis and F. stannardi (Taylor and Krouft, 2006) from Illinois, and specimens identified as introduced individuals of F. cf. ronaldi ( Adams et al., 2015, Kessler et al., 2015) using a 600 bp portion of the cytochrome c oxidase (COI) analyzed. Given this, Faxonius elix n. sp. is considered a member of the Old/Lower Ohio River clade as described herein.

Conservation status. Given the restricted geographic range of the species, the recently discovered co-occurrence of multiple non-native crayfish species ( Procambarus acutus Girard 1852 , Faxonius immunis Hagen 1870 ) within streams containing populations of the species, and the obvious anthropogenic impacts to habitat where the species resides, F. elix n. sp. is recommended Endangered status following the criteria of the American Fisheries Society as described by Taylor et. al. (2007). Likewise, these observed and potential impacts to the species warrant a classification as Critically Endangered following the criteria of the International Union for the Conservation of Nature (IUCN 2012).

Material examined. Number, sex, and form of specimens examined are in parenthesis. MI = form I male, MII = form II male, F = female, KDFWR # denotes Kentucky Department of Fish and Wildlife Resources catalog number, EKU # denotes Branley A. Branson Museum of Zoology. Asterisk denotes specimen included in genetic analysis.

Faxonius elix . KENTUCKY: Bullitt County: EKU 3875 (1 MI), EKU 3848 (1 MI). Meade County: EKU 3842 (2 MI), EKU 3853 (1 MI), EKU 3889 (3 MI). Jefferson County: EKU 2279 (6 MI), EKU 2363 (4 MI), EKU 3846 (2 MI), EKU 3857 (1 MI), EKU 3873 (1 MI), EKU 3874 (1 MI), KDFWR 92* (1 MI), KDFWR 100* (1 MI), KDFWR 79* (1 MI), KDFWR 99* (1 MI), KDFWR 79* (1 MI), KDFWR 80* (1 MI), KDFWR 91* (1 F), KDFWR 92* (1 MI), KDFWR 93* (1 MII), KDFWR 98* (1 MII), KDFWR 99* (1 MI), KDFWR 100* (1 MI), KDFWR 104* (1 F), KDFWR 105* (1 MII), KDFWR 106* (1 F), KDFWR 107* (1 F), KDFWR 108* (1 F), KDFWR 109* (1 F), KDFWR 111* (1 MII), KDFWR 112* (1 MII), KDFWR 117* (1 MII), KDFWR 118* (1 MII), KDFWR 119* (1 MII), KDFWR 120* (1 MII), KDFWR 121* (1 MII), KDFWR 122* (1 MII), KDFWR 123* (1 F), KDFWR 124* (1 F), KDFWR 125* (1 MII), KDFWR 126* (1 MII), KDFWR 127* (1 F), KDFWR 128* (1 MII), KDFWR 129* (1 MII), KDFWR 130* (1 F), KDFWR 131* (1 F), KDFWR 132* (1 F).

Faxonius immunis . KENTUCKY: Jefferson County. KDFWR 110* (1 F), KDFWR 113* (1 MII).

Faxonius jeffersoni : KENTUCKY: Jefferson County: EKU 2104 (2 MI), EKU 2105 (2 MI), EKU 2670 (2 MI), EKU 865 (3 MI), EKU 2121 (2 MI), EKU 2901 (1 MI), EKU 2571 (1 MI), EKU 2572 (1 MI), EKU 180 (3 MI), EKU 478 (4 MI), EKU 534 (1 MI), EKU 613 (6 MI), EKU 618 (7 MI), EKU 619 (6 MI), EKU 622 (4 MI), EKU 3834 (7 MI), EKU 3839 (2 MI), EKU 3843 (5 MI), KDFWR 97* (1 MI), KDFWR 82* (1 MI), KDFWR 74* (1 MI), KDFWR 75* (1 MII), KDFWR 76* (1 MII), KDFWR 77* (1 MII), KDFWR 78* (1 MII), KDFWR 97* (1 MI). Oldham County: EKU 3840 (2 MI), EKU 3858 (2 MI), KDFWR 84* (1 MI), KDFWR 87* (1 MI), KDFWR 81* (1 MI), KDFWR 82* (1 F), KDFWR 83* (1 F), KDFWR 84* (1 MI), KDFWR 85* (1 MII), KFDWR 87* (1 MI), KDFWR 88* (1 MII), KDFWR 90* (1 MI), KDFWR 133* (1 MII), KDFWR 134* (1 MI), KDFWR 135* (1 MI), KDFWR 136* (1 MII), KDFWR 137* (1 MII), KDFWR 138* (1 MII).

Figures

FIGURE 6. Dorsal view of MI holotype of Faxonius elix n. sp. Photograph by Price Sewell.

FIGURE 7. Comparative plate of key diagnostic differences between Faxonius jeffersoni and Faxonius elix n. sp. Photos include MI gonopod (left column), rostrum (center column), and mandible (right column) of F. elix n. sp. (top row) and F. jeffersoni (bottom row). Arrows point to diagnostic characteristics for F. elix n. sp. Photographs by Guenter Schuster.

FIGURE 8. Faxonius elix n. sp.: Male Form I holotype (A–D; H, J, K), morphotype male Form II (E, F), and allotype female (G, I). Lateral aspect of carapace (A); mesial and lateral aspect of Form I male gonopod, respectively (B–C), mesial view of entire gonopod of Form I male (D); mesial and lateral aspect of form II male gonopod, respectively (E–F); ventral aspect of epistome (G); dorsal view of carapace (H); ventral view of female annulus ventralis (I); dorsal view of antennal scale (J); dorsal view of right chelae (K). Photographs by Guenter Schuster.

FIGURE 9. Type locality for Faxonius elix n. sp., Fern Creek at Feganbush Lane (Kentucky Highway 864) crossing, Jefferson County, Kentucky (38.160374o N, -85.639214o W. Photograph taken on November 19, 2018.

FIGURE 10. Typical habitat for Faxonius elix n. sp. throughout its range with signs of anthropogenic alternation.