Torrenticola pendula 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 pendula Fisher & Dowling sp. n.

Material examined.

HOLOTYPE (♀): from USA, Maine, Washington County, Old Stream, off Route 9, 5.5 km west of Route 192 at Wesley, 6 June 2012, by IM Smith, IMS120012.

PARATYPES (1 ♀; 1 ♂): Maine, USA: 1 ♂ (ALLOTYPE) from Washington County, Old Stream, off Route 9, 5.5 km west of Route 192 at Wesley, 6 June 2012, by IM Smith, IMS120012 • 1 ♀ from Washington County, Old Stream, off Route 9, 5.5 km west of Route 192 at Wesley, 6 June 2012, by IM Smith, IMS120012.

Type deposition.

Holotype (♀), allotype (♂) deposited in the CNC; paratype (1 ♀) deposited in the ACUA.

Diagnosis.

Torrenticola pendula are similar to other members of the Rusetria "Eastern 2-Plates" group ( T. biscutella , T. caerulea , T. delicatexa , T. indistincta , T. malarkeyorum , T. sellersorum , T. tysoni , T. ululata , T. whitneyae , T. microbiscutella , T. feminellai ) in having anterio-lateral platelets fused to the dorsal plate, having dorsal coloration separated into anterior and posterior portions (except T. ululata and T. indistincta ), and being distributed in the east. It is one of only four Eastern 2-Plates that have dark, bold, bluish-purple coloration (also T. tysoni , T. biscutella , and T. sellersorum ). T. pendula can be differentiated from other Eastern 2-Plates (except T. whitneyae and T. feminellai ) by having a more elongate gnathosomal bay (2.42-2.9 in T. pendula , 1.4-2.24 in others) and often by having a dorsal pattern of dark bluish-purple separated into anterior and posterior portions connected medially. In the Rusetria Complex only T. whitneyae and T. magnexa (rarely) has a similar pattern. T. pendula can be differentiated from T. magnexa by having anterio-medial platelets fully fused to the dorsal plate (anterio-lateral platelets partially fused to the dorsal plate in T. magnexa ). T. pendula can be differentiated from T. whitneyae by having a more elongate rostrum (length/width = 2.87-3.06 in T. pendula , 2.41-2.69 in T. whitneyae ). T. pendula can be differentiated from T. feminellai by having less elongate pedipalpal tibiae (length/width = 2.78-3.05 in T. pendula ; 3.63-4.11 in T. feminellai ).

Description.

Female (Figure 188) (n = 2) (holotype measurements in parentheses when available) with characters of the genus with following specifications.

Dorsum - (630-650 (630) long; 490-490 (490) wide) ovoid with bold purple coloration both anteriorly and posteriorly connected medially. Anterio-medial platelets (145-145 (145) long; 45-47.5 (47.5) wide). Anterio-lateral platelets (170-177.5 (170) 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-4 350-350 (350)). Dorsal plate proportions: dorsum length/width 1.29-1.33 (1.29); dorsal width/distance between Dgl-4 1.40-1.40 (1.40); anterio-medial platelet length/width 3.05-3.22 (3.05); anterio-lateral platelet length/width 2.37-2.72 (2.72); anterio-lateral/anterio-medial length 1.17-1.22 (1.17).

Gnathosoma - Subcapitulum (320-335 (335) long (ventral); 242-252 (252) long (dorsal); 147.5-147.5 (147.5) tall) colorless. Rostrum (127.5-137.5 (137.5) long; 42.5-45 (45) wide). Chelicerae (336-347 (347) long) with curved fangs (53-62 (62) long). Subcapitular proportions: ventral length/height 2.17-2.27 (2.27); rostrum length/width 3.00-3.06 (3.06). Pedipalps with tuberculate ventral extensions on femora and genua. Palpomeres: trochanter (45-47.5 (47.5) long); femur (102.5-107.5 (102.5) long); genu (67.5-71.25 (67.5) long); tibia (72.5-75 (75) long; 23.75-25 (25) wide); tarsus (17.5-17.5 (17.5) long). Palpomere proportions: femur/genu 1.51-1.52 (1.52); tibia/femur 0.67-0.73 (0.73); tibia length/width 3.00-3.05 (3.00).

Venter - (770-800 (770) long; 532-557 (557) wide) with bold purple coloration. Gnathosomal bay (187.5-195 (195) long; 75-77.5 (75) wide). Cxgl-4 subapical. Medial suture (10-12.5 (12.5) long). Genital plates (180-186.25 (186.25) long; 168.75-172.5 (168.75) wide). Additional measurements: Cx-1 (290-301 (290) long (total); 110-115 (115) long (medial)); Cx-3 (345-350 (346) wide); anterior venter (145-157.5 (145) long). Ventral proportions: gnathosomal bay length/width 2.42-2.60 (2.60); anterior venter/genital field length 0.78-0.88 (0.78); anterior venter length/genital field width 0.86-0.91 (0.86); anterior venter/medial suture 11.60-15.75 (11.60).

Male (Figure 189) (n = 1) (allotype only) with characters of the genus with following specifications.

Dorsum - (500 long; 380 wide) ovoid with bold purple coloration separated into anterior and posterior portions. Anterio-medial platelets (130 long; 41.25 wide). Anterio-lateral platelets (155 long; 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-4 275). Dorsal plate proportions: dorsum length/width 1.32; dorsal width/distance between Dgl-4 1.38; anterio-medial platelet length/width 3.15; anterio-lateral platelet length/width 2.48; anterio-lateral/anterio-medial length 1.19.

Gnathosoma - Subcapitulum (272.5 long (ventral); 197.5 long (dorsal); 110 tall) colorless. Rostrum (107.5 long; 37.5 wide). Chelicerae (280 long) with curved fangs 50 long). Subcapitular proportions: ventral length/height 2.48; rostrum length/width 2.87. Pedipalps with tuberculate ventral extensions on femora and genua. Palpomeres: trochanter (38.75 long); femur (85 long); genu (58.75 long); tibia (62.5 long; 22.5 wide); tarsus (15 long). Palpomere proportions: femur/genu 1.45; tibia/femur 0.74; tibia length/width 2.78.

Venter - (620 long; 430 wide) with faint purple coloration. Gnathosomal bay (152.5 long; 52.5 wide). Medial suture (72.5 long). Cxgl-4 subapical. Genital plates (126.25 long; 120 wide). Additional measurements: Cx-1 (250 long (total); 100 long (medial)); Cx-3 (300 wide); anterior venter (207.5 long). Ventral proportions: gnathosomal bay length/width 2.90; anterior venter/genital field length 1.64; anterior venter length/genital field width 1.73; anterior venter/medial suture 2.86.

Immatures unknown.

Etymology.

Specific epithet ( pendula ) named for the swinging torture axe described in "The Pit and the Pendulum" by Edgar Allan Poe, most artistic depictions of which resemble the dorsal patterning on this species.

Distribution.

Known only from Washington County, Maine (Figure 187).

Remarks.

Torrenticola pendula groups with other members of the Rusetria Complex with high support. The two specimens (one male and one female) are 6.7% different in COI sequence from each other, suggesting each represents a separate species. However, in addition to similar overall appearance and occurring in the same sample, they also are indistinguishable in characters that are not usually sexually dimorphic (e.g., pedipalp proportions). Because of this, we consider these two specimens as the same species, despite the high COI variability.

In all analyses, T. pendula groups with other eastern members of the Rusetria Complex that have posterio-lateral platelets fused with the dorsal shield, but in both analyses the position of this species within that clade was not well-supported. This species was 17-18% different in COI sequence from sister species.

Based upon overall similarity, fusion of the lateral platelets with the dorsal shield, phylogenetic position, and distribution, we were able to place this species in the Eastern 2-Plate Identification Group.

This species hypothesis is supported by phylogenetic affinity, high divergence between species (17-18%), and by the morphological characters outlined in the diagnosis.