Faxonius roberti Fetzner Jr & Taylor 2018, new species
Creators: name: Fetzner Jr, James W.
name: Taylor, Christopher A.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Cambaridae
Faxonius
Faxonius roberti

description: Faxonius roberti, new species
Figures 3–4, Table 3
Orconectes eupunctus Williams, 1952:334, pl. 1: figs. 1–8 [in part]; 1954:840, figs. 41–49 [in part].— Hobbs, 1974:19, fig. 116 [in part].
Orconectes (Crockerinus) eupunctus.— Fitzpatrick, 1987:51 [in part], Hobbs, 1989:36, fig. 154 [in part]. Faxonius eupunctus.—Crandall and De Grave, 2017:629 [in part].
Diagnosis. Body and eyes pigmented (Fig. 3). Rostrum deeply excavated, terminating in long acumen; median carina absent. Rostral margins thickened; straight, subparallel or slightly concave; terminating in spines (Fig. 4H). Areola 31.9–39.2% ( = 34.7%, n = 76, SD = 0.01) of total length of carapace, narrowest part at midpoint, 4.7–9.2 ( = 6.3, n = 76, SD = 0.9) times as long as wide, with one to three (mode = 2, n = 76, SD = 0.4) punctations across narrowest part (Fig. 4H). One (rarely zero (1.3%) or two (3.9%)) corneous cervical spine on each side of carapace (Fig. 4A). Postorbital ridges well developed, terminating in corneous spines (Fig. 4H). Suborbital angle obsolete (Fig. 4A). Antennal scale broadest distal to midlength, thickened lateral margin terminating in large corneous spine (Fig. 4G). Ischia of third pereiopods of males with hooks; hooks overreaching basioischial articulation in Form-I males only. Chela with two or three rows of tubercles (see Variation) along mesial margin of palm, usually five to 11 tubercles in mesialmost row and four to ten in dorsomesial row, third row, if present, with few scattered tubercles; dorsal surfaces of fingers lacking well defined longitudinal ridges (Fig. 4K). Mandible with serrateedged incisor region. Cephalomedian lobe of epistome subpentagonal to subtriangular without cephalomedian projection; epistomal zygoma forming weak arch. First pleopods of Form-I male symmetrical, extending to posterior edge of base of second pereiopods when abdomen flexed. First pleopod of Form-I male without shoulder on cephalic surface at base of central projection; central projection corneous, constituting 20.2–27.6% ( = 23.9, n = 27, SD = 0.02) of total length of first pleopod, continuous with main shaft of pleopod, tapering to a pointed tip, tip slightly arched caudolaterally; mesial process equal to or slightly subequal in length to central projection, noncorneous, tapering to an acute tip, tip arched cephalomesially (Figs. 4B, C, F). First pleopod of Form-II male noncorneous, extending to posterior edge of bases of second pereiopods when abdomen flexed forward; central projection straight, mesial process arched slightly cephalomesially and subequal in length; both elements tapering to rounded tips (Figs. 4D, E). Annulus ventralis immovable, subrhomboidal; cephalic half with wide median trough and two caudally directed weak protuberances overhanging centrally located fossa; sinuate sinus running from center of fossa to slightly raised caudal edge (Fig. 4I).
Description of holotypic male, form I. Body slightly depressed dorsoventrally, carapace wider than abdomen (17.4 and 15.2 mm, respectively). Greatest width of carapace larger than height at caudodorsal margin of cervical groove (17.4 and 15.8 mm, respectively). Postorbital carapace length 78.1% of total length of carapace. Areola 5.3 times longer (11.4 mm) than wide (2.1 mm) with three punctations across narrowest part; length of areola 34.9% of total length of carapace. Rostrum deeply excavated dorsally, floor smooth, lacking carina; margins thickened, straight and slightly converging, terminating in corneous spiniform marginal tubercles. Acumen long and terminating in corneous spine, reaching posterior margin of third antennal peduncle. Postorbital ridges well developed, terminating in corneous spines. Suborbital angles obsolete. Two corneous cervical spines on righthand side, dorsal most spine less than half the length of more ventrally located spine, single spine on lefthand side broken off. Antennal scale as in Diagnosis. Right antennal scale 7.0 mm long, 2.5 mm wide. Epistome as in Diagnosis. Abdomen longer than carapace (34.7 and 32.5 mm, respectively). Cephalic section of telson bearing two spines in each caudolateral corner, more mesial pair movable. Proximal podomere of uropod with spine extending over mesial ramus and spine in caudolateral corner extending over lateral ramus. Caudal margin of cephalic section of lateral ramus with 18 (left) and 15 (right) fixed spines and one movable spine in caudolateral corner, lateral ramus with median ridge terminating in spine. Lateral margin of mesial ramus terminating in spine; mesial ramus with prominent median ridge terminating in premarginal spine. Dorsal surfaces of telson and uropods setiferous.
Mesial surface of palm of left chela with two rows of tubercles, nine tubercles in each row, with an additional three interspersed tubercles between. Mesial and lateral surfaces of chela, and opposable margins of fingers, covered with punctations; dorsal surface with scattered punctations, ventral side with scattered puncations mostly along lateral edge. Dorsal surface of finger of propodus with slight submedian longitudinal ridge, more pronounced near tip of finger; basal half of opposable margin with six tubercles, first two roughly the same size, third tubercle from base of finger largest, remaining three tubercles slightly decreasing in size toward tip of finger. Dorsal surface of dactyl with weak submedian longitudinal ridge flanked by setiferous punctations; basal half of opposable margin with five tubercles, first three of roughly the same size, fourth tubercle largest, fifth slightly smaller than first three. Propodus and dactyl with subterminal corneous tip.
Right carpus with deep oblique furrow dorsally; dorsal surface with one large corneous spine at distolateral corner; mesial margin with one large corneous procurved spine at midpoint; ventral surface with one large corneous spine just lateral to midpoint of distal margin, one large spine just mesial to midpoint of distal margin. Dorsodistal surface of merus with two large corneous spines; ventral surface with one large corneous spine at distolateral corner and mesial row of six spines, row terminating in large corneous spine. Ischium lacking corneous spine just proximal to midlength of mesial margin, one large tubercle on distal end of mesial margin.
Hook on ischium of third pereiopod only; hook simple, overreaching basioischial articulation, not opposed by tubercle on basis. First pleopod of Form-I male without shoulder on cephalic surface at base of central projection; central projection corneous, constituting 20.2% of total length of first pleopod, parallel to main shaft of pleopod, tapering to pointed tip, tip directed caudomesially; mesial process slightly subequal in length to central projection, non-corneous, tapering to acute tip, tip arched cephalolaterally (Figs. 4B, C, F).
Description of allotypic female. Except for secondary sexual characteristics, differing from holotypic male in the following respects. Areola constituting 34.6% of length of carapace and seven times longer than wide. Postorbital carapace length 79.7% of length of carapace. Abdomen wider than carapace (20.3 and 19.4 mm, respectively). Left cheliped regenerated. Mesial surface of palm of right chela with two rows of tubercles, nine tubercles in mesialmost row and eight tubercles in dorsomesial row. One small tubercle adjacent to distal-most tubercle in second row. Finger of propodus with basal half of opposable margin with eight tubercles, first two roughly the same size, third and sixth tubercles largest, remaining tubercles smaller and slightly decreasing in size toward tip of finger. Eighth tubercle offset mesially from others. Basal half of opposable margin of dactyl with seven tubercles, first four of roughly the same size, remaining four slightly decreasing in size toward tip of dactyl. Seventh tubercle offset slightly laterally. Caudal margin of cephalic section of lateral ramus of uropod with 17 fixed spines.
Sternum between third and fourth pereiopods narrowly V-shaped. Postannular sclerite 64% as wide as annulus ventralis (described in Diagnosis). First pleopod uniramous, barely reaching caudal margin of annulus when abdomen flexed.
Description of morphotypic male, form II. Differing from holotype as follows: Areola constituting 33.5% of length of carapace, 5.6 times longer than wide. Postorbital carapace length 76.8% of length of carapace. Ventral surface of right merus with mesial row of five spines. Hook on ischium of third pereiopod not overreaching basioischial articulation. First pleopod as described in Diagnosis.
Type locality. Spring River just upstream of the AGFC Bayou Access boat ramp off County Road 2027, 7.0 km S Mammoth Spring, Fulton County, Arkansas (36.43396, -91.52714, WGS 84, 134 m) (Fig. 5). The type series was collected from a riffle with cobble, approximately 135 m upstream of the boat ramp. The Spring River is a large cool river that is directly fed by Mammoth Spring, which is the largest spring in Arkansas and the third largest in the Ozarks Plateau region. At the time of collection (15 April 2017), the river was 35–40 m wide near the type locality with a swift flow. Water temperature was 64.4°F (the temperature of water emerging upstream from Mammoth Spring is 58°F) and water depth at the riffle was roughly 0.5 m. The river was rocky, containing what appeared to be a gravel to cobble substrate and occasional larger rocks. Stream banks were well vegetated and the surrounding land was densely forested. The river at this access point receives a considerable amount of traffic from public users, including activities such a boating, camping, canoeing and fishing.
Disposition of primary types. The holotypic male (form I), allotypic female, and morphotypic male (form II), are housed in the crustacean collection of the Carnegie Museum of Natural History (CMNH; accession numbers 38749, 38750, and 38751, respectively). Paratypes have also been deposited at CMNH (38758, 38759) and the Illinois Natural History Survey (INHS; catalog numbers: 6920, 10704, 10785, 12343, 12822). The localities and dates of collection are provided in the following range and specimens examined section.
Range and specimens examined. Endemic to the Spring and Strawberry river drainages in the Ozark Highlands physiographic province of northern Arkansas and southern Missouri. This species can be found in Fulton, Lawrence, and Sharp counties Arkansas and Howell County, Missouri (Fig. 10). In both river drainages, the species is known only from the mainstems, except in the Spring River drainage where it is also found in the mainstems of the more southern major tributaries (e.g., South Fork Spring River and West Fork Spring Creek). The collection lots from CMNH and INHS below are referenced using their museum accession numbers. MI=male Form-I, MII=male Form-II, F=female, MDC = Missouri Department of Conservation.
A total of 76 specimens have been examined from the following nine localities: ARKANSAS: Fulton County: (1). Spring River at Many Islands, 0.4 km SSW Many Islands, 36.386, -91.5307 (WGS84), 25-May-2006, coll: BK Wagner, M Kottmyer, J Koppleman and Fry, INHS-10704, 1 MII, 1 F. (2). Spring River at Bayou Access, 7 km S Mammoth Spring, 36.433389, -91.528396 (WGS84), 20-May-2014, coll: C Ames, M Mabery, C Knerr and L Bachmann, CMNH-38782, 1 MI, 6 MII, 5 F; CMNH-38 751, 1 MII (Morphotype). (3). TYPE LOCALITY: Spring River upstream of Bayou Access boat ramp, 7 km S Mammoth Spring, 36.433396, -91.52714 (WGS84), 15-Apr-2017, coll: JW Fetzner Jr., CMNH-38759, 2 MI, 3 MII; CMNH-3 8749, 1 MI (Holotype); CMNH-38750, 1 F (Allotype). (4). Spring River just upstream of Big Creek confluence, 7.6 km SSE Mammoth Spring, 36.42934, -91.520324 (WGS84), 24-Oct-1998, coll: C Flinders, INHS-6920, 3 MI. Sharp County: (5). Strawberry River at Barnes Road crossing, 5.3 km W Poughkeepsie, 36.07815, -91.53805 (WGS84), 02-Oct-2014, coll: BK Wagner and A Daniel, CMNH-38765, 7 MI, 3 F. (6). Strawberry River at Barnes Road crossing, 7.3 km E Evening Shade, 36.07808, -91.5381 (WGS84), 21-Sep-2006, coll: BK Wagner, M Kottmyer and S Henry, INHS-10785, 8 MII, 9 F. (7). Strawberry River downstream of Barnes Road, 5.3 km W Poughkeepsie, 36.07624, -91.53778 (WGS84), 03- Sep-2010, coll: BK Wagner, CMNH-38766, 3 MII, 1 Fjuv. (8). Strawberry River upstream of Piney Fork, 6.9 km WNW Poughkeepsie, 36.09137, -91.55379 (WGS84), 09-Aug-2011, coll: BK Wagner, CMNH-38767, 1 MII, 1 F. MISSOURI: Howell County: (9). West Fork Spring Creek at Hwy-142 bridge, 4.9 km W Lanton, 36.5114, -91.85616 (WGS84), 18-Sep-1984, coll: WL Pflieger, INHS-12343, 13 MI, 8 F; 1984-03-22, coll: WL Pflieger and HV Wheeler, INHS-12822, 2 MI. Additional Collections (examined but not measured): ARKANSAS: Fulton County: (10). South Fork Spring River at Sunrise Road crossing, 1.0 km ESE Sturkie, 36.455383, -91.86197 (WGS84), ??-???-2010, MDC Crayfish Crew, CMNH-38769, 1 MII, 1 F. (11). Spring River upstream of Bayou Access, 7 km S Mammoth Spring, 36.433396, -91.52714 (WGS84), 15-Apr-2017, coll: JW Fetzner Jr., CMNH- 38759, 2 MI, 3 MII. Lawrence County: (12). Spring River at the AGFC Imboden boat ramp, 0.6 km ENE Imboden, 36.203904, -91.167702 (WGS84), ??-???-2010, coll: MDC Crayfish Crew, CMNH-38768, 1 MII, 1 Fjuv. Sharp County: (13). Spring River at Hardy Beach, 1.0 km ESE Hardy, 36.31236, -91.4724 (WGS84), 24-Aug-2011, coll: MDC Crayfish Crew, CMNH-38770, 5 MII, 5 F. (14). South Fork Spring River at Griffith Park, 2.5 km WSW Hardy, 36.30947, -91.5097 (WGS84), 14-Apr-2017, coll: JW Fetzner Jr., BK Wagner and D Filipek, CMNH- 38758, 4 MII, 1 F; 36.30948, -91.50984 (WGS84), 24-Aug-2011, coll: MDC Crayfish Crew, CMNH-38771, 5 MII, 5 F. For a few additional published localities for this species (as Orconectes eupunctus) see Flinders & Magoulick (2005) and examine Figure 11 (gray dots) herein. Additional historical records from the Strawberry River depicted on the map (Fig. 10) are from the AGFC crayfish distribution database (B.K. Wagner, personal communication).
Size. The largest specimen examined was a 38.1 mm CL Form-II male. Females (n = 29) ranged in size from 16.5 to 36.3 mm CL ( = 25.6 mm). Form-I males (n = 27) ranged from 16.1 to 32.5 mm CL ( = 23.2 mm). Form- II males (n = 20) ranged from 15.6 to 38.1 mm CL ( = 25.1 mm).
Color. Base color of dorsal and lateral surfaces of cephalothorax dark brown to dark orange, fading to cream near ventral edges. Portion anterior to cephalic groove light brown to olivaceious green. Black saddle just anterior to cephalic groove, with black dot appearing just posterior to cephalic groove in center of triangle produced by the cephailc groove and the branchiocardial grooves (= areola). An additional black saddle crossing the juncture of posterior edge of carapace and anterior edge of abdomen, roughly equally divided onto both surfaces. Lateral sides of first abdominal pleuron with orangish, cream or yellowish patch that interrupts the saddle, making these patches stand out. Dorsal surface of abdomen with posteriorly tapering black stripe, fading out just before reaching tailfan. Lateral surfaces of abdomen light orange/brown to light yellowish orange. Tailfan olivaceous green with light orange highlights. Walking legs olivaceous green with hints of light orange at articulation joints, fading to light orange near junction with body. Chelae and carpus overall olivaceous green, with some individuals more infused with light orange closer to lateral margin of palm, thus making the dactyl and propodus appear a darker green than palm region. Tips of both fingers light orange to light red, then quickly transitioning into olivaceous green. Spines and tubercles on chela carpus same color as base color. First quarter of anterior part of merus olivaceous green, the remainder cream colored. Ventral surfaces of cephalothorax and abdomen cream to white with hints of light orange on basal segment of walking legs. Ventral surface of chelae are mostly cream colored, especially on lateral half, but mesial one third can be light olivaceous green. In Form-II males, the first and second pleopods have hints of light orange (similar to base of walking legs), with the tips of the first pleopod darker orange.
On very rare occasion, variant individuals that are bright orange in color over the entire body surface have been reported in the Strawberry River basin (B.K. Wagner, personal communication).
Habitat and life history notes. Faxonius roberti occurs in mainstem streams of fourth order or larger, with substrates of cobble and gravel. Within these streams, the species was most commonly encountered in cobble in areas with moderate to fast flow. The cobble under which the species occurred was variable in size, ranging from 5 cm 2 to 20 cm 2. It seemed to be most commonly encountered in riffle areas.
While occurrence data are only limited to currently available museum collections, they indicate that Form-I males are present in the population during the months of March, April, May, September and October. Form-II males were recorded during April, May, August and September. No ovigerous females were available in collections, however, the Allotype female, which was collected in mid-April, did carry 212 young attached to the underside of her abdomen.
Etymology. It is our great pleasure to name this species in honor of Robert (Bob) J. DiStefano of the Missouri Department of Conservation (MDC). Bob has worked tirelessly over his career to help understand and conserve the crayfish fauna of the Ozarks in general, and Missouri in particular, so it is fitting that this Ozarkian species be named in his honor. This new species should not be confused with “ Orconectes bobi ”, the ficticious species name assigned to Bob when he was wearing his full crayfish costume while conducting public outreach programs for the MDC.
Crayfish associates. The following species were collected from habitats containing Faxonius roberti, new species: Faxonius ozarkae (Williams, 1952); Faxonius marchandi (Hobbs, 1948) and Cambarus hubbsi Creaser, 1931.
Variation. In addition to the range of ratios and counts given in the Diagnosis section, several ontogenetic variations were observed in F. roberti new species, none of which show a geographic pattern of variation. The number of palmar tubercle rows is variable, usually with two but sometimes a partial third row being present. The marginal spines of the rostrum varied between pronounced spines, weak spines and tubercles. The cervical spines ranged from zero to two, with one being most common (95%). In one individual, the spine was replaced with a tubercle.
Comparisons. Faxonius roberti, new species, differs from all other members of the genus by possessing a unique combination of Form-I first pleopod characters. The Form-I male pleopod of F. roberti, new species, is most similar in length and general shape to other members of the former subgenus Crockerinus Fitzpatrick, 1987, which occur throughout the central and eastern United States. This subgenus, and all other subgenera formerly in the genus Orconectes, were not recognized by Crandall and De Grave (2017) in their world classification of freshwater crayfish based on recent phylogenetic evidence. All members of the former subgenus Crockerinus generally possessed short, straight first pleopod elements which may or may not curve at their distal tips and a central projection accounting for between 20 and 33% of the total first gonopod length. Faxonius roberti differs from all other Crockerinus members occurring west of the Mississippi River in possessing a Form-I first pleopod mesial process that is equal in width at its base to the central projection, which tapers to an acute tip, and is not curved caudodistally.
Relationships. See the Phylogenetics text in the Results section for a discussion of the relationships of this species to other taxa. See also Fig. 2.
Common name. The suggested common or vernacular name for this species is the Spring River Crayfish, which is in reference to its affinity for the mainstem channels of the two spring-fed rivers where the species occurrs.
Conservation status. Given F. roberti’ s limited distribution in only two major Black River drainages and the known introduction of the non-native Ringed Crayfish (F. neglectus) in portions of the Spring River drainage (Larson & Magoulick 2008), we recommend a status of Vulnerable following the criteria of the American Fisheries Society as outlined by Taylor et al. (2007). These same factors warrant a classification as Vulnerable following the criteria of the International Union for the Conservation of Nature (IUCN).
description: Published as part of Fetzner Jr, James W. & Taylor, Christopher A., 2018, Two new species of freshwater crayfish of the genus Faxonius (Decapoda: Cambaridae) from the Ozark Highlands of Arkansas and Missouri, pp. 491-520 in Zootaxa 4399 (4) on pages 500-507, DOI: 10.11646/zootaxa.4399.4.2, http://zenodo.org/record/1206820