Torrenticola biscutella Fisher & Dowling

Fisher, J. Ray, Fisher, Danielle M., Skvarla, Michael J., Nelson, Whitney A. & Dowling, Ashley P. G., 2017, Revision of torrent mites (Parasitengona, Torrenticolidae, Torrenticola) of the United States and Canada: 90 descriptions, molecular phylogenetics, and a key to species, ZooKeys 701, pp. 1-496 : 1

Torrenticola biscutella Fisher & Dowling sp. n.

Material examined.

HOLOTYPE (♀): from USA, Arkansas, Montgomery County, South Fork Ouachita River, access off County Road 17 at Forest Road 903, 29 Jul 2011, by IM Smith, IMS110040, DNA 1263.

PARATYPES (4 ♀; 3 ♂): Arkansas, USA: 1 ♂ (ALLOTYPE) from Montgomery County, Ouachita River (34°34'53.20"N, 93°53'0.16"W), 5 Oct 2007, by AJ Radwell, & HW Robison, AJR070300A • 2 ♂ Montgomery County, Ouachita River (34°34'53.20"N, 93°53'0.16"W), 5 Oct 2007, by AJ Radwell, & HW Robison, AJR070300A • 3 ♀ from Montgomery County, South Fork Ouachita River, access off County Road 17 at Forest Road 903, 29 Jul 2011, by IM Smith, IMS110040 • Missouri, USA: 1 ♀ from Crawford County, Huzzah Creek, Red Bluff campground, off Road V east of Davisville, 23 Jul 2011, by IM Smith, IMS110029.

Type deposition.

Holotype (♀), allotype (♂), and some paratypes (2 ♀; 1 ♂) deposited in the CNC; other paratypes (2 ♀; 1 ♂) deposited in the ACUA.

Diagnosis.

Torrenticola biscutella are similar to other members of the Rusetria "Eastern 2-Plates" group ( T. caerulea , T. delicatexa , T. feminellai , T. indistincta , T. malarkeyorum , T. microbiscutella , T. pendula , T. sellersorum , T. tysoni , T. ululata , and T. whitneyae ) in having anterio-lateral platelets fused to the dorsal plate, having dorsal coloration separated into anterior and posterior portions (except T. indistincta and T. ululata ), and being distributed in the east. It is one of only four Eastern 2-Plates that have dark, bold, bluish-purple coloration (also T. pendula , T. sellersorum , and T. tysoni ). Torrenticola biscutella can be differentiated from T. caerulea , T. ululata , T. indistincta , and T. feminellai by dorsal coloration and pattern. T. biscutella can be differentiated from T. tysoni by having a stockier rostrum (length/width = 2.55-2.83 in T. biscutella , 3.06-3.50 in T. tysoni ). Female T. biscutella can be differentiated from female T. malarkeyorum by having a shorter subcapitulum (ventral length = 290-315 in T. biscutella , 317.5-335 in T. malarkeyorum ). Male T. biscutella can be differentiated from male T. malarkeyorum by having a slightly rounder dorsum (length/width 1.37-1.42 in T. biscutella , 1.42-1.56 in T. malarkeyorum ). Additionally, although T. biscutella and T. malarkeyorum have the same dorsal coloration and pattern, often the coloration is bold in T. biscutella and faint in T. malarkeyorum . Female T. biscutella can be differentiated from female T. delicatexa by having a shorter genital field (152.5-167.5 in T. biscutella , 175-198 in T. delicatexa ) and male T. biscutella can be differentiated from male T. delicatexa by having a slightly rounder dorsum (length/width = 1.37-1.42 in T. biscutella , 1.44-1.56 in T. delicatexa ). Female T. biscutella can be differentiated from female T. sellersorum by anterior venter/genital field length (0.82-0.88 in T. biscutella , 0.69-0.77 in T. sellersorum ). Male T. biscutella can be differentiated from male T. sellersorum by having slightly stockier anterio-lateral platelets (length/width = 2.58-2.74 in T. biscutella , 2.76-3.00 in T. sellersorum ). T. biscutella can be differentiated from T. pendula by having a stockier gnathosomal bay (1.55-1.85 in T. biscutella , 2.42-2.9 in T. pendula ); more elongate tibiae (3.11-3.45 in T. biscutella , 2.78-3.05 in T. biscutella ); and by dorsal pattern. T. biscutella can be differentiated from T. microbiscutella by having a more ovoid dorsum (length/width = 1.33-1.42 in T. biscutella , 1.63-1.75 in T. microbiscutella ) and by anterior venter/genital field width (♀ = 0.84-0.91 in T. biscutella , 1.25-1.33 in T. microbiscutella ; ♂ = 1.68-1.80 in T. biscutella and 1.95-2.29 in T. microbiscutella ). T. biscutella can be differentiated from T. whitneyae by having more elongate pedipalpal tibiae (3.11-3.45 in T. biscutella , 2.42-2.95 in T. whitneyae ) and by anterior venter/genital field length (♀ = 0.82-0.88 in T. biscutella , 0.59-0.75 in T. whitneyae ; ♂ = 1.55-1.76 in T. biscutella and 1.37-1.43 in T. whitneyae ).

Description.

Female (Figure 25) (n = 4) (holotype measurements in parentheses when available) with characters of the genus with following specifications.

Dorsum - (560-630 (560) long; 420-455 (420) wide) ovoid with bluish-purple coloration separated into anterior and posterior portions, and bold or faint orange medially. Anterio-medial platelets (122.5-135 (122.5) long; 40-45 (40) wide). Anterio-lateral platelets (140-170 (140) long; 62.5-75 (62.5) wide) fused to dorsal plate. Dgl-4 much closer to the edge of the dorsum than to the muscle scars (distance between Dgl-4 300-330 (300)). Dorsal plate proportions: dorsum length/width 1.33-1.38 (1.33); dorsal width/distance between Dgl-4 1.38-1.40 (1.40); anterio-medial platelet length/width 3.00-3.31 (3.06); anterio-lateral platelet length/width 2.24-2.48 (2.24); anterio-lateral/anterio-medial length 1.14-1.28 (1.14).

Gnathosoma - Subcapitulum (290-315 (290) long (ventral); 207-240 (208) long (dorsal); 137.5-155 (137.5) tall) colorless. Rostrum (110-125 (110) long; 42.5-47.5 (42.5) wide). Chelicerae (286-335 (286) long) with curved fangs (55-70 (56) long). Subcapitular proportions: ventral length/height 2.02-2.11 (2.11); rostrum length/width 2.56-2.67 (2.59). Pedipalps with tuberculate ventral extensions on femora and genua. Palpomeres: trochanter (43.75-50 (43.75) long); femur (107.5-122.5 (107.5) long); genu (65-72.5 (65) long); tibia (80-86.25 (80) long; 23.75-25 (23.75) wide); tarsus (20-20 (20) long). Palpomere proportions: femur/genu 1.59-1.74 (1.65); tibia/femur 0.69-0.74 (0.74); tibia length/width 3.35-3.45 (3.37).

Venter - (660-740 (660) long; 488-544 (489) wide) with faint bluish-purple coloration. Gnathosomal bay (151.25-172.5 (151.25) long; 97.5-100 (100) wide). Cxgl-4 subapical. Medial suture absent. Genital plates (152.5-167.5 (152.5) long; 142.5-160 (142.5) wide). Additional measurements: Cx-1 (274-309 (275) long (total); 118-135 (121) long (medial)); Cx-3 (319-392 (319) wide); anterior venter (130-147.5 (130) long). Ventral proportions: gnathosomal bay length/width 1.55-1.73 (1.55); anterior venter/genital field length 0.82-0.88 (0.85); anterior venter length/genital field width 0.84-0.91 (0.91).

Male (Figure 26) (n = 3) (allotypic measurements in parentheses when available) with characters of the genus with following specifications.

Dorsum - (430-445 (440) long; 310-315 (310) wide) ovoid with bluish-purple coloration separated into anterior and posterior portions, and bold or faint orange medially. Anterio-medial platelets (97.5-97.5 (97.5) long; 33.75-36.25 (35) wide). Anterio-lateral platelets (122.5-130 (130) long; 45-50 (47.5) wide) fused to dorsal plate. Dgl-4 much closer to the edge of the dorsum than to the muscle scars (distance between Dgl-4 230-242.5 (230)). Dorsal plate proportions: dorsum length/width 1.37-1.42 (1.42); dorsal width/distance between Dgl-4 1.30-1.35 (1.35); anterio-medial platelet length/width 2.69-2.89 (2.79); anterio-lateral platelet length/width 2.58-2.74 (2.74); anterio-lateral/anterio-medial length 1.26-1.33 (1.33).

Gnathosoma - Subcapitulum (230-235 (235) long (ventral); 175-177.5 (177) long (dorsal); 20-20 (20) tall) colorless. Rostrum (85-92.5 (92.5) long; 30-36.25 (36.25) wide). Chelicerae (225-241 (241) long) with curved fangs (45-50 (46) long). Subcapitular proportions: ventral length/height 2.29-2.47 (2.29); rostrum length/width 2.55-2.83 (2.55). Pedipalps with tuberculate ventral extensions on femora and genua. Palpomeres: trochanter (23.75-37.5 (37.5) long); femur (85-90 (90) long); genu (52.5-55 (55) long); tibia (68.75-72.5 (72.5) long; 21.25-22.5 (22.5) wide); tarsus (17.5-20 (20) long). Palpomere proportions: femur/genu 1.62-1.64 (1.64); tibia/femur 0.81-0.82 (0.81); tibia length/width 3.11-3.24 (3.22).

Venter - (510-525 (525) long; 335-380 (336) wide) with faint bluish-purple coloration. Gnathosomal bay (115-122.5 (122.5) long; 65-67.5 (67.5) wide). Cxgl-4 subapical. Medial suture (60-65 (65) long). Genital plates (102.5-110 (102.5) long; 100-100 (100) wide). Additional measurements: Cx-1 (215-226 (226) long (total); 99-110 (100) long (medial)); Cx-3 (252-275 (252) wide); anterior venter (167.5-180 (180) long). Ventral proportions: gnathosomal bay length/width 1.70-1.85 (1.81); anterior venter/genital field length 1.55-1.76 (1.76); anterior venter length/genital field width 1.68-1.80 (1.80); anterior venter/medial suture 2.68-2.83 (2.77).

Immatures unknown.

Etymology.

Specific epithet ( biscutella ) refers to the appearance of only two anterio-dorsal platelets due to the fusion of lateral platelets with the dorsal shield (bi-, L. two; scutella, L. little plate).

Distribution.

Interior Highlands (both Ozarks and Ouachitas), likely endemic (Figure 24).

Remarks.

Torrenticola biscutella groups with other members of the Rusetria Complex with high support and specimens of this species were less than 2% different in COI sequence from each other. In all analyses, T. biscutella groups with two other morphologically similar species: T. malarkeyorum and T. caerulea . These three species are 3-5% different from each other in COI sequence. The three of these species are morphologically similar to the more distantly-related T. delicatexa . Of these four species, the range of T. biscutella only overlaps with T. malarkeyorum in the Ozark Mountains and these species are easily differentiated by color. T. biscutella is the only one of these four species known from the Ouachita Mountains, and it is not known from east of the Mississippi River, where the other three species are distributed (only T. malarkeyorum is known from west of the Mississippi River).

Based upon overall similarity, dorso-lateral platelet fusion, and distribution, we were able to place this species within the Eastern 2-Plate Identification Group.

This species hypothesis is supported by biogeography, low COI divergence within the species (0-2%) and high divergence between species (3-15%), and by morphological characters outlined in the diagnoses.