Orconectes (Buannulifictus) texanus
Creators: name: Johnson, Daniel P.
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Cambaridae
Orconectes
Orconectes texanus

description: Orconectes (Buannulifictus) texanus
Texas River Crayfish
new species
Figs 6, 25–34, Tables 5–8
Cambarus palmeri longimanus, Faxon, 1898 [in part]
Orconectes palmeri longimanus, Hobbs, 1942 [in part]
Orconectes (Buannulifictus) palmeri longimanus, Fitzpatrick, 1987 [in part]
Diagnosis. Body pigmented, eyes well developed. Rostrum with marginal spine, lacking median carina. Carapace with single cervical spine. Areola obliterated and constituting 31.5 to 33.8 (mean 32.6 ± 0.7) percent of total carapace length (43.1 to 46.9, mean 44.5 ± 1.1, percent postorbital carapace length). Suborbital angle obtuse. Ischium of third pereiopod in first form male with simple strong hook reaching basioischial articulation. Gonopod of first form male with two processes, reaching midlength of coxa of 2nd pereiopod when abdomen flexed; central projection corneous, mesial process not; cephalic shoulder near base of central projection absent or weak; central projection constituting 34.5 to 45.7 (mean 40.9 ± 2.3) percent of appendage length, longer than mesial process; both processes curved caudally, central projection tip directed 90 degrees to axis of shaft, that of mesial process directed 45 to 90 degrees. Postorbital ridge and merocarpal articular condyles conspicuously bright red. Body not heavily freckled.
Holotypic male, form I. Cephalothorax (Fig. 25, 26 a, b) subcylindrical, slightly depressed. Abdomen slightly narrower than cephalothorax (16.5 and 18.2 mm, respectively). Areola obliterated. Cephalic section of carapace 2.2 times as long as areola, latter obliterated and comprising 31.5% of total length of carapace (43.1% of postorbital carapace length). Surface of carapace punctate dorsally and granulate laterally.
Rostrum with margins slightly converging, not distinctly thickened, and terminating in well-developed, upturned marginal spines; upper surface deeply concave, lacking median carina, marginal row of heavy punctations, otherwise apunctate; acumen relatively long with upturned tip. Postorbital ridge strong, grooved dorsolaterally, and bearing anterior spine. Suborbital angle obtuse. Brancheostegal spine present.
Abdomen slightly longer than carapace (40.0 and 38.7 mm, respectively). Cephalic section of telson (Fig. 26 i) with two spines on margins, lateral ones fixed.
Cephalic lobe of epistome campanulate, with slightly thickened irregular margins; main body of epistome with distinct, elongate fovea. Ventral surface of proximal podomere of antennular peduncle with spine at twothirds distance from proximal margin. Antennal peduncle with well developed spine on both basis and ischium; flagellum reaching beyond distal margin of telson by length of telson. Antennal scale (Fig. 26 j) 3.3 times as long as broad, widest at midlength. Third maxilliped extending to spine on proximal podomere of antennule.
Right chela (Figs. 26 c–f) depressed, palm inflated and gaping; palm about 1.4 times as broad as length of mesial margin; latter comprising 26% total chela length; dorsal, lateral and ventral surfaces of palm covered with punctations with a few small tubercles dorsomesially. Mesial margin of palm with two rows of tubercles, 9 in the upper row and 8 in the lower (left chela with 6 upper, 8 lower). Immovable finger strongly punctate on dorsal and ventral surfaces; lateral margin with well-defined single row of punctations bordered on both sides by apunctate low ridges; dorsal surface with pronounced groove bordering mesial margin and weak groove bordering lateral margin; opposable margin with row of 12 tubercles (12 on left chela) on proximal two thirds and minute denticles on distal half, base bearing minor plumose setae. Dactyl dorsally and ventrally punctate, dorsum with broad relatively apunctate low median ridge, and low groove bordering opposable margin; mesial margin with three rows of tubercles, those of middle row largest, dorsal row smaller and ventral row poorly developed; ventral surface with broad low apunctate median ridge; opposable margin with row of 16 tubercles along proximal 4/5ths, with minute denticles on distal half.
Carpus of cheliped longer than broad; dorsally with oblique furrow; all surfaces weakly punctate with simple tubercles dorso- and ventromesially; spiniform tubercles are at the following locations: 2 on mesial margin, 1 on distal ventral margin and 1 on ventrolateral articular condyle.
Dorsal, mesial and lateral surfaces of merus weakly and sparsely punctate; ventral surface (Fig 26 g) with two rows of tubercles generally increasing in size distally, lateral row of 5 and mesial row of 12; additional spiniform tubercles are found at the following locations: 2 on distal half of dorsal surface and 1 on the ventrolateral distal margin. Lower surface of ischium with 2 small tubercles, otherwise weakly punctate.
Hook on ischium (Fig 26 h) and gonopod (Figs. 27 a–c) as described in "Diagnosis". Uropod (Fig. 26 i) with both lobes of basal podomere bearing single acute spines; mesial ramus with well developed median carina terminating in distinctly premarginal spine; distolateral spine well developed.
Allotypic female. Differing from holotype, other than in secondary sexual characteristics, in following respects: cephalic section of carapace 2.0 times as long as areola, latter comprising 33.0% of total length of carapace (43.6% of postorbital carapace length); dorsal surface of rostrum with widely scattered weak punctations; abdomen distinctly longer than carapace (45.4 and 40.6 mm, respectively); flagellum reaching distal margin of telson; antennal scale 2.8 times as long as broad; right chela palm mesial margin comprising 29% total chela length; carpus of cheliped with 3 spines on mesial margin; ventral surface of merus with mesial row of 10 tubercles; and lower surface of ischium with 1 small tubercle. Margin of annulus ventralis (Fig. 28) semicircular caudally, angular cephalically and laterally, with cephalolateral margins straight; sinus originates near midline of cephalic margin, extends and opens up to dextral side, extends across midline to sinistral side, then back to midline where it closes, then extends with minor sinuosity to midline of caudal margin where is terminates on a small protrusion; surface wrinkled; cephalic 40% uncalcified; annulus 1.24 times as wide as postannular sclerite; latter with straight caudal margin, curved cephalic margin, and a width/ length ratio of 3.0.
Morphotypic form II male. Differing from holotype, other than in secondary sexual characteristics, in following respects: cephalic section of carapace 2.1 times as long as areola, latter comprising 32.4% of total length of carapace (44.5% of postorbital carapace length); tip of acumen not distinctly upturned; flagellum reaching only to sixth abdominal segment, probably due to damage; antennal scale 2.8 times as long as broad; palm of left chela (right regenerated) 1.1 times as broad as length of mesial margin; latter comprising 28% total chela length; mesial margin of palm with 8 tubercles in upper row and 9 lower row; opposable margin of dactyl with row of 16 tubercles; carpus with two additional spiniform tubercles on distolateral margin; ventral surface of merus with lateral row of 4 tubercles and mesial row of 8; dorsal surface of distal half merus with 3 spines, with 3 more on distodorsal margin; lower surface of ischium with 1 tubercle; hook on ischium of third pereiopod well developed, but not as hooked as holotype and not reaching basioischial articulation. Gonopod (Figs. 27 d–e) with both processes noncorneous, thicker and relatively much shorter than holotype; central projection comprises 22.5% total appendage length and is distinctly longer than mesial process, both tips curved caudally with tip of central projection directed about 60 degrees to axis of shaft, that of mesial process 45 degrees.
Color notes. Holotype (Fig. 25): Basic coloration light brown. Cephalic section of carapace darkened on rostrum and caudal fourth; postorbital ridge prominently bright red; rostral margin caudally dull red grading anteriorly to orange-tan at marginal spine; margin of acumen dull yellow; cervical groove blue gray; antennal region yellow-tan. Thoracic region with obscure very fine speckling dorsally, with lateral tubercles light; laterally with well-defined dark brown kidney-shaped blotches caudally flanking the cervical groove; almost indiscernible dark, ventrolateral, longitudinal stripe; caudal margin black, grading to gray on ventrolateral margin. Caudal margins of terga black and tinged with red (more red on caudalmost segments), grading to gray on pleura caudal margins; obscure light marks on cephalolateral margins of terga. Telson and uropod rami with red caudal margins; proximal podomeres of uropod and cephalolateral corners of telson with red marks. Antennal scale dark brown mesially and on lateral margin, otherwise light tan. Cheliped dorsally tan with distinct dark brown to black spots on carpus, palm and proximal third of fixed finger; fingers tipped with yellow, grading proximally to cream, then to light blue-gray, then to the normal tan at a about half distance from base; merus blue-gray on distal third, cream otherwise; merocarpal articular condyles distinctly bright red, especially on cheliped; ischiomeral articulations less distinctly red to red tinged; propodactyl articulation of cheliped red tinged; coxobasial articular condyles of pereiopods 1 trough 4 and proximomesial margin of basioischial segment of cheliped distinctly red. Ventor mostly cream, with a few pale blue markings.
The color pattern of this species is remarkably uniform across its range with only relatively minor variations seen. This assessment is based on dorsal and lateral body photos of 78 living specimens (14 Sabine, 17 Neches, 19 Trinity, 7 San Jacinto, 21 Navasota), in addition to hundreds of observations in the field. The body of most specimens varies from unspeckled to obscurely speckled; however a few specimens show moderate levels of speckling and a single specimen from the Sabine River was heavily speckled, mostly in the thoracic region. In a small minority of specimens the thoracic region of the carapace has a distinct, dark, ventrolateral, longitudinal stripe. The postorbital ridge is usually solid red with light corneous spine on tip, but in some cases, especially in the Navasota River, the caudal fourth is yellow. In a few cases indistinct dorsolateral dark spots are present on the first and sometimes 2nd abdominal segment. In most specimens, particularly younger ones, the fingers of the cheliped are distinctly tipped with red, and are a more vivid blue at midlength; these colors appear to fade with age. The spots on the cheliped show considerable variation in size, number and density.
Type locality. Trinity River just downstream of the spillway of the Lake Livingston dam, Polk County, Texas (30.62590° N, 95.00848° W). The area is highly oxygenated and has an abundance of large flat rocks, underwhich most of the specimens were found.
Disposition of types. The holotype, allotype and morphotype (ɗI, Ψ, ɗII) are deposited in the National Museum of Natural History (Smithsonian Institution), nos. 1145311, 1145312 and 1145313, respectively. Paratypes are deposited in the Illinois Natural History Survey Crustacean Collection.
Size. The largest specimen available is a female from the San Jacinto River in Montgomery County, Texas, having a carapace length of 49.7 (postorbital length 35.5) mm. The largest and smallest first form males have corresponding sizes of 41.6 (31.6) mm and 20.8 (14.9) mm and are from the Navasota River (Robertson County) and the Neches River (Shelby County), respectively. Neither ovigerous females nor ones carrying young have been collected.
Range and specimens examined. Examined as part of this study were 59 form I males, 66 adult or large immature females and an uncounted number of form II males and juveniles, spanning the following six drainage basins: Sabine River, Neches River, Neches-Trinity coastal basin, Trinity River, San Jacinto River and Navasota River (tributary of Brazos River). The species has been collected at 154 sites in 34 counties (Fig. 6) as follows (number of sites in parentheses): Anderson (2), Angelina (2), Brazos (7), Cherokee (5), Ellis (2), Freestone (4), Gregg (3), Harris (2), Houston (18), Jasper (1), Jefferson (1), Kaufman (1), Leon (15), Liberty (4), Madison (6), Montgomery (13), Nacogdoches (3), Navarro (2), Newton (4), Panola (3), Polk (12), Rains (1), Robertson (4), Rusk (2), Sabine (1), San Augustine (2), San Jacinto (9), Shelby (2), Smith (2), Trinity (8), Tyler (1), Van Zandt (2), Walker (6) and Wood (4). The high density of localities in the western half of the range is the result of this area being heavily surveyed during the peak of juvenile abundance in May and June. The Neches and Sabine systems were mostly surveyed only in the main channels during late summer and fall when abundance is low. Prior to this study, the species (as O. p. longimanus) was known from only 7 counties, based on museum specimens and information in Johnson and Johnson (2008).
Variations. This species shows significant geographic variation in the gonopod (Figs. 29 a–x, 30a–o) and profound variation in the annulus ventralis (Figs. 32–34). The gonopod varies in process length, ratio of central projection caudal offset to total appendage length, and the form of curvature of the central projection. The process lengths (Table 5) are relatively long in the Neches and Trinity basins, and short in the Sabine, San Jacinto and Navasota basins. The ratio of central projection caudal offset to total appendage length (Fig 1 a, Table 6) increases from east to west. The taper of the central projection (Fig. 1 c, Table 7) varies slightly, with the Trinity and Neches showing the largest and smallest values.
TABLE 5. Ratio of central projection length to total appendage length (see Fig. 1 b) of Orconectes texanus. Drainage Range Mean
Sabine 34.5–40.8 38.3 ± 1.7
Neches 41.4–45.7 43.5 ± 1.3
Trinity 41.6–43.9 42.6 ± 1.5
San Jacinto 38.5–40.8 39.9 ± 0.8
Navasota 38.4–41.8 40.2 ± 1.0
TABLE 6. Ratio of central projection caudal offset to total appendage length (see Fig. 1 a, b) of Orconectes texanus.
Geographic variation of the annulus ventralis by basin is as follows. Sabine (Figs. 32 a–h): Annulus fairly uniform, caudal margin usually angled, sometimes rounded; cephalic margin angled to rounded; sinus with single long, narrow, laterally-directed lobe and usually no fossa, but sometimes small opening in sinus; pillow structure always present in cephalic 40%. Neches (Figs. 32 i–x): Caudal margin usually rounded but sometimes slightly angled; cephalic margin rounded to subangled; sinus usually with two significant lobes, sometimes one; definite fossa on cephalic half often present, especially for larger specimens; pillow or subpillow structure cephalically present in one third of specimens, but never so pronounced as in Sabine; Trinity (Fig. 33): Caudal margin distinctly rounded in large majority of specimens, sometimes angled; cephalic margin always angled; large fossa located on cephalic half always present and bordered by thin cephalic rim; pillow structure never present; fossa usually with a long straight, oblique caudolateral rim forming part of border and oblique ridge extending from opposite cephalolateral margin into fossa, but variable; San Jacinto (Figs. 34 a–l): outline always rhombic, wide in relation to postannular sclerite, with caudolateral margins slightly concave in half of specimens; fossa without oblique caudolateral margin like seen in most Trinity specimens. Navasota (Figs. 34 m–t): Similar to San Jacinto, but usually narrower in relation to postannular sclerite and never with concave caudolateral margins.
TABLE 7. Central projection taper expressed as the ratio of the tip width to base width (see Fig. 1 c) of Orconectes texanus.
TABLE 8. Measurements (mm) of Orconectes texanus.
Although the annulus ventralis varies greatly, with the typical form of most basins distinct from that of other basins, the variation within each basin is great and some overlap of characters exists. This alludes to a lack of genetic isolation of the basins. Note that the annuli of the Sabine and Trinity are entirely distinct, but that of the intermediate basin, the Neches, shows some characteristics of both: some have the cephalic pillow structure of the Sabine and many have a more rounded caudal margin and a more distinct cephalic fossa with narrower cephalic rim approaching that of the Trinity. The annulus outline and fossa shape of the Trinity specimens is on average greatly different from that of the San Jacinto and Navasota systems, both of which border the Trinity on the west; however they are not entirely distinct. Although no annuli have been found in either the Navasota or San Jacinto system that approach the typical form of the Trinity, a few Trinity annuli show characteristics that fall within the range of variation of the Navasota and San Jacinto basins. Both the Navasota and San Jacinto basins show little variation in annulus ventralis structure and that present can be largely attributed to size, with larger specimens possessing relatively narrower annuli.
Relationships. The proximity of ranges and very similar gonopod structure allude to a close relationship between Orconectes texanus, Orconectes occidentalis and O. palmeri longimanus. That the three were previously all long considered to be O. p. longimanus indicates the difficulty of separating them. The relationship of O. texanus and O. occidentalis was previously discussed under "Relationships" for the latter.
O. p. longimanus differs from O. texanus in the following respects: The ratio of central projection caudal offset (Fig. 1 a) to total appendage length, ranges from 20.6% to 22.2% (mean 21.3% ± 0.6%, N=10) compared to 22.4% to 33.5% (mean 28.1% ± 2.5%, N=58) in O. texanus; the differences in this character can be readily seen by comparing Figures 30 p–w with Figures 29 a–x and 30a–o. The gonopod has on average a much less tapered central projection; the ratio of tip width to base width (Fig. 1 c) varies from 21% to 34% (mean 28.9% ± 4.4%, N=10) compared to 9% to 24% (mean 14.8% ± 3.0%, N=52) in O. texanus; although the range is slightly overlapping, the average ratio for O. texanus is half that of O. p. longimanus. In comparison to this difference, note the small variation by basin of O. texanus shown in Table 7. Partially illustrating this character is Figure 31, which shows the distal 20% of central projections for the series of O. p. longimanus specimens examined and that for the type series of O. texanus.
The annulus ventralis of O. p. longimanus has a different structure than that of any of the geographic variants of O. texanus. The most significant comparison is with the Sabine basin population, since it is the only basin containing O. texanus that shares part of its boundary with the Sulphur River basin (which is the source of the large majority of the O. p. longimanus specimens used in this analysis); the annuli ventralis of those specimens (Figs. 32 a–h) show no similarity to the O. p. longimanus annuli (Figs. 14 a–p); the sinus with its single, large narrow lobe is very different and its cephalic pillow structure is never present in O. p. longimanus. A second useful comparison is with the Trinity basin population of O. texanus, since both species occur in the basin and in relatively close proximity, with the closest separation being 60 km (O. p. longimanus occurs in the East Fork of the Trinity River and in Honey Creek in Grayson and Collin counties). Although only 2 annuli from relatively mature specimens of this population were examined, they appear consistent with those from the Sulphur River. The annulus ventralis of the Trinity specimens of O. texanus has a more open, differently shaped fossa with a thin cephalic rim; caudally the sinus is slightly sinuous, often forking and usually terminating in a protrusion on the caudal margin, while that of O. p. longimanus is largely simple, straight and without the caudal protrusion; the surface is often wrinkled, while that of O. p. longimanus is usually very smooth or occasionally dimpled.
The color patterns of the two species, based on examination of 20 photos of O. p. longimanus and 78 photos of O. texanus in addition to many wild observations of both species, is distinctly different and so much so that there has never been a question as to the identity of a specimen seen by the author in the wild (see Figs. 25 and 16). O. p. longimanus lacks the prominent red postorbital ridge of O. texanus, although a minor amount of red is often present. The color of fingers of the cheliped is bright red at the tips and grades proximally to black, then to bluish black; while in O. texanus the color varies from red to yellow at the tips, depending on age, and grades proximally to cream then to blue or pale blue. The kidney shaped blotches located dorsolaterally just caudal to the cervical groove are usually absent, but may be obscure (as in the illustrated specimen); in O. texanus they are always distinct. The articular condyles of all pereiopod articulations more distinctly red than in O. texanus; the ventral surface has much more extensive red markings; and all spines on the telson and uropod are red (white in O. texanus). The body of mature specimens never has dark speckling; in O. texanus the body frequently has obscure dark speckling, which may be fine or coarse. The great differences in color patterns of the two species seems even more significant when one considers that a wide array of species, spanning two subgenera (albeit questionable), have color patterns apparently indistinguishable from O. texanus; including O. (Hespericambarus) hathawayi, O. (H.) maletae, and O. (H.) perfectus; or more similar than that of O. (Buannulifictus) p. longimanus, including O. (B.) p. creolanus, O. (B.) p. hobbsi and O. (B.) occidentalis.
Photographs of O. p. longimanus have been examined from many locations in the Red River system, including the following: Red River (Johnson and Johnson, 2008); Sulphur River; Lake Columbia, Arkansas; and LeFlore County, Arkansas (Chris Taylor, pers. comm.). These photos show a high degree of color pattern uniformity within the system, with characteristics very similar to that of Figure 16.
O. p. palmeri from near the type locality (Reelfoot Lake, Obion County, Tennessee) appears to be in many respects more similar to O. texanus than is O. p. longimanus. The ratio of central projection caudal offset to total appendage length (Fig. 1 a) and central projection’s taper (Fig. 1 c) fall well within the range of O. texanus and the gonopods appear indistinguishable. It can only be weakly differentiated in the following respects: The annulus ventralis (Fig. 35) often has a large, deep, crosswise but slightly oblique fossa reminiscent of that of O. virilis (Figs. 35 a–c, 35d approaching that form) and not seen in O. texanus; however about half the annuli examined (Figs 35 d–f) are not distinctly different from that of O. texanus. The color pattern of the specimen in the single photo available for the vicinity, which is from Hickman County, Kentucky, approximately 30 km from the type locality (Taylor and Schuster, 2004), shows several characters never seen in O. texanus including a dark lateral longitudinal stripe, a dark blotch laterally flanking the caudal section of the branchiocardiac groove and a lack of red on the merocarpal articulations. Additionally, a series of distinct paired spots are present on all abdominal segments; similar spots are present in only a small minority of O. texanus specimens and never so distinct and usually virtually indiscernible.
Pflieger (1996) illustrates a specimen of O. palmeri from Dunklin County, Missouri. This location is also relatively close to the O. p. palmeri type locality (80 km), but is west of the Mississippi and as such may be considered to be in the so called O. p. palmeri / O. p. longimanus intergrade zone as defined by Williams (1954). The color pattern of this specimen is also quite distinct from that of O. texanus and shares much in common with the aforementioned Kentucky O. p. palmeri specimen but differs in the following respects: it is more speckled, it lacks the dark blotch flanking the caudal section of the branchiocardiac groove and the lateral carapace stripes are obscure or broken (unclear from photo).
A photo of a crayfish from Mississippi (Chris Lukhaup pers. comm.) identified as O. p. palmeri shows a color pattern very different from that of the two previously discussed specimens and very close to that of O. texanus. In that specimen, the postorbital ridge and merocarpal articulation are distinctly red and the kidneyshaped blotch caudally flanking the cervical groove is present, although less pronounced than in O. texanus. Similarly patterned is a specimen from the Saline River basin in central Arkansas (C. Lukhaup pers. comm.). That specimen would likely fall into the range of O. p. palmeri / O. p. longimanus intergrades.
Given the high degree of color pattern uniformity of O. palmeri relatives in the western part of the range (e.g., O. occidentalis, O. texanus and O. p. longimanus in the Red River system), the large differences of that near the O. p. palmeri type locality compared with that of Mississippi and central Arkansas seem significant. Studies of how these populations relate to O. texanus, O. p. palmeri and O. p. longimanus need to be investigated; however, given the large distance of those locations from any type locality and with them occurring far from the boundaries of Texas, clarification of such is considered beyond the scope of this study.
With evidence of O. texanus and O. p. longimanus being separate species and with the latter currently considered conspecific with O. p. palmeri, the definition of O. texanus as a valid species seems appropriate at this time. If in the future O. p. palmeri and O. p. longimanus are raised to full species, the relationship of O. palmeri with O. texanus would need to be more closely examined. In the case of O. palmeri being a full species, the ranges of it and O. texanus would be separated by a large distance, with O. longimanus, O. maletae, and O. hathawayi occupying the intermediate area. This, along with the aforementioned minor character differences, may also be sufficient for O. texanus and O. palmeri to be considered separate species
Etymology. Texanus after the state of Texas, which encompasses the majority of the species’ range.
Associates. The species has been found with the following associates: Cambarellus puer, C. shufeldtii, Cambarus ludovicianus, Fallicambarus fodiens, Procambarus acutus, P. c l a r k i i, P. dupratzi, P. kensleyi, P. nigrocinctus, and P. s i m u l a n s.
description: Published as part of Johnson, Daniel P., 2010, Four new crayfishes (Decapoda: Cambaridae) of the genus Orconectes from Texas, pp. 1-45 in Zootaxa 2626 on pages 31-44, DOI: 10.5281/zenodo.276049