Creaserinus trinensis, Johnson & Stern & Crandall, 2021

Johnson, Daniel P., Stern, David B. & Crandall, Keith A., 2021, The genus Creaserinus Hobbs, 1973 (Decapoda: Cambaridae) in Texas, Zootaxa 5017 (1), pp. 1-84 : 72-79

Creaserinus trinensis n. sp.

Figs. 3, 5, 6e, k, 7e, i, 8b, d–f, 9–12, 39–42, Tables 1 , 6, 10, 13, 15–17, 31, 32

Diagnosis. Adults with rostrum devoid of marginal spines. Areola obliterated along part of its length. Antennal scale more than twice as long as broad. Cheliped with sufflamen. Lateral margin of chela costate, dorsal surface lacking tubercles on lateral half, ventrolateral surface lacking arched row of prominent setiferous punctations; opposable margin of dactyl with distinct excision in basal half; mesial margin bearing at least 2 rows of tubercles, those of main row extending from base at least two-thirds length of finger. Length of carpus distinctly less than width of palm of chela. Ventral surface of merus with mesial and lateral rows of tubercles. Mesial surface of chela of 2 nd pereiopod bearing prominent tufts of plumose setae. Hooks on ischia of 3 rd pereiopod only. Boss on coxa of 4 th pereiopod, rounded, slightly compressed and scarcely protruding ventrally. Gonopod of form I male lacking proximomesial spur and terminating in two distinct parts (mesial process and central projection). Central projection corneous, bladelike, lacking subapical notch, recurved 125–135° to axis of shaft, with distal part directed caudoproximally with tip never crossing central projection of corresponding gonopod, and base not inclined laterally, length 29.6– 35.2% (x = 32.2, s = 1.3, n = 36) of total gonopod length. Mesial process noncorneous, recurved 110–125° to axis of shaft, proximal half not strongly inflated. Proximal gap between processes usually present. Uropodal endopod with distolateral spine; distomedian spine premarginal. Telson divided with spine on anterolateral flank of suture. Function 6 positive when b refers to Creaserinus trinensis n. sp. and a refers to any of other five Texas species (refer to Tables 6, 10, 13, 16, and 17). Distribution confined to Trinity River Bottomland north of latitude 30.28. Sex ratio of juvenile population (<16 mm CL) not strongly skewed female.

FIG. 39. Creaserinus trinensis n. sp.: (a) lateral and (b) dorsal views of holotype. Specimen exhibits broad-striped phase.

Holotypic male, form I. Eyes pigmented and with faceted cornea, but small. Body subcylindrical, weakly depressed (Figs. 39a, b). Abdomen slightly narrower that cephalothorax (11.2 and 12.6 mm, respectively). Greatest width of carapace near one-fourth length of areola from cervical groove, where slightly greater than height (12.6 and 11.4 mm, respectively).Areola obliterated over most of its length and comprising 41.2% of CL and 48.2% of POCL. Rostrum with slender, convex margins converging from base to poorly delimited acumen; apex corneous, distinctly upturned, and reaching ultimate podomere of antennular peduncle; dorsal surface concave with submarginal rows of punctations and few others scattered in between. Subrostral ridge weak but visible in dorsal aspect to base of acumen. Postorbital ridge slender, well defined, and relatively abruptly terminating anteriorly just posterior to margin of orbit. Cervical spine absent. Very weak branchiostegal tubercle present. Suborbital angle nearly obsolete. Carapace punctate dorsally and weakly granulate-punctate laterally.

Abdomen subequal in length to carapace (25.2 and 25.4 mm, respectively); pleura small with subrounded margins; pleuron of 2 nd segment clearly overlapping that of 1 st. Telson divided and deeply incised laterally; caudolateral angle of cephalic section with pair of spines, more mesial one movable.

Cephalic lobe of epistome subpentagonal, lacking punctations, margins slightly elevated and smooth ventrally; main body with weak fovea. Ventral surface of proximal podomere of antennule with spine at three-fourths length. Antennal peduncle without spines, single flagella present reaching midlength of 2 nd abdominal segment, but distal extremity appears damaged.Antennal scale (Fig. 40f) reaching tip of acumen and almost reaching ultimate podomere of antennular peduncle; lamella broadly rounded distomesially, broadest at four-fifths length, and broader than thickened lateral part. Mandible with cephalic noncorneous, subtuberculiform molar process and caudal corneous, irregular molar process. Ventral surface of ischium of 3 rd maxilliped with long setae mesially and medium-length setae laterally; mesial half of ventral surface of basis bearing long setae.

Right chela of cheliped (Figs. 40a–d) 2.0 times as long as broad, strongly depressed; width of palm 2.0 times length of mesial margin. Latter bearing main row of 6 (left with 7) tubercles, flanked dorsolaterally by group of 6 (left with 6) slightly smaller ones and ventrolaterally by 1 (left with 1). Dorsal surface of palm and fingers bearing setiferous punctations, those of dactyl and fixed finger much more distinct. Lateral margin of propodus costate along distal two-thirds, but broadly rounded proximally. Ventral surface punctate, with punctations more prominent on fingers, single tubercle on margin opposite base of dactyl with one (left with 2) more situated proximolaterally to it. Long conspicuous setae present on proximal half of opposable margin of fixed finger. Dorsal and ventral surfaces of both fingers with well-defined ridges flanked by punctations. Opposable margin of fixed finger with row of 4 (left with 4) tubercles along proximal two-thirds, 2 nd and 3 rd from base largest, 4 th situated more ventrally; single row of minute denticles extending from 3 rd tubercle to corneous tip of finger. Opposable margin of dactyl with prominent excision in proximal third; 2 tubercles borne within excision, a larger one at its distal extremity, and 3 (left with 3) more distal to excision; single row of minute denticles extending from excision to corneous tip of finger. Mesial margin of dactyl with main row of 9 (left with 9) tubercles bordered dorsolaterally by row of 5 (left with 5).

FIG. 40. Creaserinus trinensis n. sp.: (a) dorsal, (b) ventral, (c) lateral, and (d) mesial views of chela; (e) tail; (f) antennal scale; (g) ventral view of merus, (h) proximal podomeres of pereiopods showing hook; and (i) annulus ventralis. a–h from holotype, i from allotype.

Carpus of cheliped 1.4 times as long as broad and 1.4 times as long as palm mesial margin; dorsal surface with longitudinal median trough, flanked with punctations; mesial surface tuberculate with large spine on distal margin; lateral and ventral surfaces punctate; ventral surface with large distomedian spine. Merus with 2 weak tubercles near dorsodistal extremity; mesial and lateral surfaces sparsely punctate; ventral surface (Fig. 40g) with mesial row of 12 tubercles (left with 12) and lateral row of 6 (left with 3), distal row absent. Ischium sparsely punctate with 1 weak tubercle ventromesially (left with 1).

Second pereiopod bearing conspicuous long setae on dorsal and ventral margins of chela and carpus, and proximal half of ventral margin and dorsodistal extremity of merus, and mats of modestly developed plumose setae on mesial faces of palm and carpus.

Hook (Fig. 40h) on ischium of 3 rd pereiopod simple, almost reaching level of basioischial articulation, and not opposed by tubercle on corresponding basis. Coxa of 4 th pereiopod as in “Diagnosis.” Coxa of 5 th pereiopod lacking boss.

FIG. 41. Creaserinus trinensis n. sp.: (a) mesial, (c) ventral, and (e) lateral views of gonopod of holotype; and (b) mesial and (d) lateral views of gonopod of morphotype.

FIG. 42. Creaserinus trinensis n. sp.: mesial views of gonopods of form I male paratypes. Each photo annotated with name of county where collected.

Gonopod (Figs. 41a, c, e) reaching coxa of 3 rd pereiopod when abdomen flexed and obscured by setae extending from surrounding sternum; shaft of appendage straight, otherwise as in “Diagnosis.” Proximal podomere of uropod with both lobes bearing single small spines; endopod with distolateral spine and distinctly premarginal distomedian spine.

Allotypic female. Differing from holotype in nonsecondary sexual characters as follows: abdomen subequal in width to cephalothorax (14.5 and 14.6 mm, respectively); branchiostegal tubercle nearly obsolete; suborbital angle obtuse and weak; abdomen slightly longer than carapace (32.4 and 30.0 mm, respectively); cephalic lobe of epistome subsemicircular, main body with more developed fovea; ventral surface of proximal podomere of antennule with spine slightly distal to midlength; right chela of cheliped 2.1 times as long as broad; width of palm 1.8 times length of mesial margin; latter with main row of 7 (left with 6) tubercles, bordered dorsolaterally by two rows of 6 (left with 7) and 1 (left with 1) and ventrolaterally by row of 1 (left with 1); opposable margin of left fixed finger with row of 5 tubercles; opposable margin of dactyl with 4 (left with 4) tubercles distal to large tubercle delimiting excision; mesial margin of dactyl with main row of 12 (left with 12) tubercles bordered dorsolaterally by row of 5 (left with 6); carpus of cheliped 1.5 times as long as broad and 1.5 times as long as palm mesial margin; ventral surface of merus of cheliped with mesial row of 12 tubercles (left with 15) and lateral row of 6 (left with 4); ischium of cheliped with 2 weak tubercles ventromesially (left with 1); second pereiopod with plumose setae on mesial faces of palm and carpus comparatively weak.

Annulus ventralis (Fig. 40i) 1.8 times as broad as long, cephalically fused to sternum. Caudal and lateral margins elevated (ventrally) and surrounding shallow, cephalic, caudodextrally-directed trough. Short sinus originating at caudomedian extremity, curving sinistrally 30°, then dextrally 150°, before terminating under dextral wall. Postannular sclerite subtriangular, half as wide and half as long as annulus. First pleopod present.

Morphotypic male, form II. Differing from holotype in following respects: areola comprising 38.5% of CL and 45.2% of POCL; suborbital angle weak and obtuse; cephalic lobe of epistome subsemicircular; single flagellum present reaching caudal margin of carapace; right chela of cheliped 2.4 times as long as broad; width of palm 1.6 times length of mesial margin; latter bearing main row of 8 tubercles (left chela regenerated) flanked dorsolaterally by group of 6 slightly smaller tubercles and ventrolaterally by row of 2 tubercles; ventral surface of propodus with row of 3 tubercles proximolaterally situated to tubercle on margin opposite dactyl; opposable margin of fixed finger with row of 5 tubercles along proximal two-thirds, 2 nd and 3 rd from base largest, 5 th situated more ventrally; opposable margin of dactyl with 5 tubercles distal to large tubercle delimiting excision; mesial margin of dactyl with main row of 12 tubercles bordered dorsolaterally by row of 6 tubercles; carpus of cheliped 1.3 times as long as palm mesial margin; dorsal surface of merus of cheliped with 3 weak tubercles near dorsodistal extremity, ventral surface with mesial row of 13 tubercles and lateral row of 5; ischium of cheliped with ventromesial row of 4 weak tubercles; second pereiopod with plumose setae on mesial faces of palm and carpus poorly developed; hook on ischium of 3 rd pereiopod and boss on coxa of 4 th pereiopod both reduced; gonopod (Figs. 41b, d) with central projection noncorneous, both processes more inflated, both recurved 120°.

Type locality. Texas Highway 7, 2.9 km (1.8 mi) west of Trinity River , Leon County, Texas (31.33598, -95.68742). Roadside ditch with extensive water, 30+ m long and up to 25 cm deep. Fenceline lined with trees but surrounding area grassland with only widely scattered trees. Morphotype collected on Farm to Market Road 3126, 120 m south of junction with State Park Road 65, Polk County , Texas (30.65525, -94.99801) .

Disposition of types. The holotype, allotype, and morphotype (nos. 1640961, 1640962, and 1640963, respectively) are deposited in the National Museum of Natural History , Smithsonian Institution. All paratypes remain in DPJ’s collection .

Size. Of 68 form I males for which measurements were made, carapace lengths range from 21.8 to 31.7 (x = 26.2) mm.

Range and specimens examined. Creaserinus trinensis n. sp. has been found at nine sites in six Texas counties, all of which are represented by at least one form I male and seven of which are represented in the molecular phylogeny. All sites are in close proximity to the Trinity River, with distances from the river ranging from 0.16 to 6.4 (x = 2.4) km, but span a distance of some 200 km along the river.

Freestone: 31.9673, 96.0513, I, 6/14/14, DJ490. Leon: 31.3360, 95.6874, I, 5/30/14, 4/23/15, 4/24/15, DJ489, DJ655, DJ664; 31.4388, 95.7550, I, 5/30/14, DJ410. Liberty: 30.4427, 94.8428, I, 3/8/14. Madison: 31.0343, 95.7010, I, 4/24/15, DJ775. Polk: 30.6552, 94.9980, I, 5/5/16, 10/16/18; 30.7342, 95.0749, I, 5/5/16, 11/1/17, 10/16/18, DJ846; 30.8363, 95.1641, I, 5/6/16, 10/16/18. Trinity: 30.8578, 95.1897, I, 5/6/16.

Variations. Variations in a number of key morphometrics and meristics may be found in Tables 6, 10, 13, and 15–17. Additional variations not found in those tables are provided here. All are based on form I males, unless otherwise noted. The rostral margins vary from straight to slightly convex and slightly to distinctly converging. The acumen ranges from distinctly to indistinctly delimited, the distal spine of which is sometimes missing, with no sign of injury. The rostrum L/W ratio ranges from 1.1 to 1.5 (x = 1.3, s = 0.1, n = 58). The ratio of the rostrum L to CL ranges from 16.1 to 20.0% (x = 18.1, s = 0.8, n = 58). The cervical spine varies in form from a small definite spine to a small indistinct bump. The branchiostegal spine varies from acute to obtuse. The suborbital angle varies from small and obtuse to nearly obsolete. The anterior lobe of the epistome varies in shape from semicircular to triangular to subtrapezoidal. The ranges in numbers of tubercles on the various cheliped podomeres include the following: 9–15 (x = 11.2, s = 1.8, n = 17) in the dactyl’s main mesial row, 5–9 (x = 6.9, s = 1.1, n = 90) and 0–2 (x = 0.3, s = 0.7, n = 10) in the 2 rows dorsolaterally flanking it, and 0–1 (x = 0.1, s = 0.3, n = 10) in the ventrolaterally flanking row; 6–8 (x = 7.2, s = 0.9, n = 11) in the main mesial row of the palm, 4–7 (x = 5.8, s = 1.0, n = 11) and 0–3 (x = 1.0, s = 0.9, n = 10) in the rows dorsolaterally flanking it, and 1–3 (x = 1.6, s = 0.7, n = 10) in the ventrolaterally flanking row; 12–15 (x = 13.8, s = 1.0, n = 17) and 3–8 (x = 5.4, s = 1.3, n = 17) in the mesial and lateral rows of the ventral surface of the merus, respectively; and 0–5 (x = 3.2, s = 1.2, n = 90) in the ischium’s ventromesial row. The sufflamen varies from well developed to somewhat reduced. Figure 42 illustrates variation in form I male gonopod. The caudal offset of the MP varies from slightly less than (Fig. 42b) to distinctly greater (Fig. 42a) than that of the CP. The tip of the MP may be acuminate (Fig. 42d) or blunt (Fig. 42m). The proximal separation between the processes may be pronounced (Fig. 42a) or weak (Fig. 42h). The processes may appear separate along their entire lengths (Fig. 42p), or the separation may be broken at midlength (Fig. 42g) or absent along the distal two-thirds (Fig. 42f). The apposable margin of the MP varies from sharply angled (Fig. 42a) to smoothly rounded (Fig. 42g). The annulus ventralis never occurs as a mirrored image of that of the allotype.

Life history notes. Seasonal collection data of Creaserinus trinensis n. sp. ( Table 32 ) exhibit patterns consistent with that of the genus Creaserinus as a whole. Refer to its “Life history notes” for discussion. Neither ovigerous females nor females carrying young have been found.

Ecological notes. This crayfish has been found in pine forest, hardwood forest, mixed forest, rangeland, and open fields; and has been collected from roadside ditches and pools. Sun exposure is full to partly shaded. The species is restricted to the floodplain of the Trinity River, and as such, the topography is flat and the soils are generally readily burrowable.

Etymology. Trinity = Trinity River + ensis (L.) = originating in, alluding to the species’ distribution which is restricted to the bottomlands of the Trinity River.

Crayfish associates. Collected with Creaserinus trinensis n. sp. were the following 10 crayfish taxa: Procambarus (Ortmannicus) acutus (n = 6, 66.7%), Creaserinus clausus (n = 4, 44.4%), Procambarus (Girardiella) curdi (n = 4, 44.4%), Procambarus (Girardiella) ceruleus (n = 2, 22.2%), Lacunicambarus ludovicianus (n = 1, 11.1%), Fallicambarus macneesei (n = 1, 11.1%), Procambarus (Scapulicambarus) clarkii (n = 1, 11.1%), Procambarus (Girardiella) simulans (n = 1, 11.1%), Procambarus (Girardiella) steigmani (n = 1, 11.1%), and Procambarus (Ortmannicus) zonangulus (n = 1, 11.1%).

Suggested Future Research

Suggested future work on the genus Creaserinus includes the following:

• Improvement in sampling in Texas, including the following regions:

o Southwestern coastal plain where many records are not identifiable to species (but presumably are Creaserinus hedgpethi ).

o The vicinity of the isolated Lamar County record.

o The distributional gaps between C. hedgpethi and both C. brevistylus and C. trinensis (to clarify the extent of the gaps).

o The entire Trinity River bottomland (to expand the number of known C. trinensis sites).

o Along the Sabine River from Sabine County to Wood County (to better understand the species richness there).

• Research on the biological cause of sex ratio skewedness of C. limulus .

• Application of more sophisticated whole-genome sequencing or broad genome survey (e.g., Wolfe et al., 2019) techniques to provide additional clarification of relationships of Texas species, including the problematic SW clade of C. clausus .

• Morphological study of females with a goal of discovering characters that would allow species to be distinguished from each other would be very useful, especially for C. limulus given its typical sex ratio skewedness.

• Given that the clades suggested by genetics are largely validated, a tremendous amount of work between Texas and Ontario is necessary to clarify species compositions of the states in between.

A New Ditch Collecting Technique

As far as we are aware, the following technique has not been previously used by astacologists for collecting crayfish. The technique is used for collecting crayfish from ditches containing water, with the targeted ditches being typically those that are frequently dry. Upon arrival at such a ditch, the collector first walks through the water of the ditch, kicking his feet through the water and substrate such that the environment becomes highly disturbed and the water very cloudy. Afterwards, standard dipnet sampling is done, sometimes making several passes along the ditch. The disturbance of the environment apparently entices crayfish occupying burrows with entrances underwater in the ditch to exit their burrows and enter open water. This technique works well for secondary burrowers like Creaserinus , but also works to some degree for primary burrowers such as Fallicambarus and Lacunicambarus . The technique was developed after noticing that when making a second pass with the dipnet in a ditch, it was often more productive than the first and often dramatically so, with the disturbance of the first pass presumably causing the crayfish to enter open water.