Texicerberus amistad Hutchins and Schwartz, 2021

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Suggested Common Name: Boquillas Cerberus
Etymology: amistad = friendship [Spanish], refering to the range of this species along the Rio Grande, the border between Texas (US) and Mexico, and the original author's desire for social justice across the border. Common name refers to the small towns of Boquillas (on the US side, now the Rio Grande Village) and Boquillas de Carmen (on the Mexican side), which named the region this species occurs in.
Taxonomic History: Texicerberus amistad Hutchins and Schwartz, 2021
Size Range: to 2.24mm
Description: (modified from Hutchins, Schwartz & Coleman, 2021) Head 1.3x longer than wide and 0.1x as long as body; lateral margins with 3-4 pairs of dorsal simple setae. Antenna 1 directed anterolaterally, 0.1x length of body; peduncle 3-segmented, segment 1 longer than others with 1 long distal seta, segment 2 with 2 distolateral setae, segment 3 with 1 short distal setae; flagellum 3-segmented, segments shorter than peduncle segments, segments 2-3 subequal in length, segment 3 with apical aesthetasc 0.4x as long as antenna 1 along with 4 simple setae, longest seta 0.9x as long as flagellum segments. Antenna 2 2.5x longer than antenna 1 and 0.2x as long as body; peduncle 6-segmented, 0.3x as long as entire antenna 2, segments 1-2 not visible dorsally, segments 3-6 with short to long lateral and apical simple setae, segment 3 rhombic, widest near midpoint, lacking medial spines, segment 6 with 1 plumose seta; flagellum 8-segmented, segments shorter than peduncle segments, segments 1-7 with 1-3 short simple setae, segment 8 with 3-4 apical simple setae. Maxilliped basis lobe extending past palp segment 1; palp segment 1 shorter than segments 2-5, segments 2-5 subequal in length, segments 2-4 with simple distomedial setae, segment 5 with 3 apical setae. Pereonite 1 0.7x as long as head and as wide or wider than head, tapering posteriorly with 1 anterolateral and 1 lateral simple seta. Pereopod 1 subchelate, inserted anterolaterally; dactyl (with claw) subequal to length to propus, with 1 ventromedial row of short simple setae and 2 ventroapical simple spines, claw long about 0.5x as long as segment; propus about 1.5x longer than wide, palm with 2 proximal robust setae, 3 middle serrate setae and 1 distomedial serrate spiniform seta, along with a distal dense row of short simple setae. Pereonites 2-4 subequal in length, narrower and shorter than pereonite 1, tergites well-developed with medial suture, 1 long simple anterolateral seta and anterior fringe of short simple setae. Pereopods 2-4 inserted anterodosrally; dactyl short, about as long as wide, with 2 short simple distal setae, 2-clawed (1 angulate); propus subcylindrical with 3-4 simple distal setae; carpus long, widest proximally, with 1 short simple proximal setae and 1 short simple and 1 longer plumose distal setae along with a small distal fringe of short setae; merus short with 1 long distal and 1 short setae; ischium long, cylindrical, with short simple setae; basis with 2 long simple and 1 longer plumose setae; coxae rounded, not produced, with 1 anterior simple seta. Pereonite 2 narrower than pereonite 4, 0.9x as wide as long. Pereonite 3 narrower than pereonite 2. Pereonites 5-7 subequal in width, larger than pereonites 2-4, lateral tergites apparently fused anteriorly. Pereopods 5-7 inserted posterodorsally; all segments similar to those of pereopods 2-7 (exc. carpus which lacks distal fringe of short setae). Pereonite 5 lacking setae. Pereonite 6 with 2 pairs of simple setae. Pereonite 7 with 1 pair of simple setae, 2x longer than wide. Pleonites 1-2 tergites simple, covering entire segment, with 1 pair of lateral setae. Pleonite 1 about as wide as long, longer and narrower than pleonite 2. Pleonite 2 wider than long. ♂ pleopod 2 protopod rectangular, about as wide as long; exopod about 0.2x as long as endopod, curved medially; endopod 1.8x longer than protopod and 0.47x as long as telson, not extending past telson tip, elongate, tubular, somewhat involute basally, opening at tip with rows of dense setae in larger individuals. Pleopod 3 uniramous, trapezoidal, longer than wide, apically with 20-30 short simple setae covering insertion of pleopod 4. Pleopod 4 biramous, fleshy; rami short, subequal in length, lacking setae. Telson 1.2x longer than wide, 1.7x longer than pleonite 2; lateral and posterior margins with 3-5 pairs of simple setae, lateral margins subparallel, posterior margin subtrapezidal. Uropod protopod rectangular, about as wide as long, with 4 distal simple setae, tip visible past telson tip; exopod 1/3rd as long as endopod, about 2x longer than wide, with 2 long simple apical setae; endopod narrow-triangular, about 3x longer than wide, 1.5x longer than protopod with 3 short simple lateral setae and 2 long simple apical setae.
Geographic Range: Currently only known from the hyperheos of the Rio Grande in  2 spots in Big Bend National Park (Texas): the mouth of Tornillo Creek (at the western trailhead of the Hot Springs Trail) and at the upper mouth of Boquillas Canyon (near athe Boquillas Canyon Trail). Likely widespread in the region in the hyperhreos of the Rio Grande
Notes: This species is most similar to T. castilloi, which can be differentiated by the proportions of the pereopod 2 propus and the setation of pleopod 3 and the uropods. T. amistad also averages larger than T. castilloi, with the latter reaching 1.5mm. The ranges of the two species do not overlap, with T. amistad occuring in the Big Bend region of Texas (and likely nearby Coahuila) and T. castilloi occuring in the San Marcos spring complex in central Texas.

Sources

Hutchins, B. T., Schwartz, B. F. & Coleman, W. T. (2021). Three new microcerberids (Isopoda: Microcerberidae) from subterranean freshwater habitats in Texas, USA. Journal of Natural History, 55(35-36):2261-2278.

Published: Feb 15, 2023