Atractides castor Gerecke 2021, sp. nov.
Creators: name: Gerecke, Reinhard
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Trombidiformes
Hygrobatidae
Atractides
Atractides castor

description: Atractides (s. str.) castor sp. nov.   
(Figs 6-7; 31 U-V)  
 Type series: Holotype ♂, SMF, Sicilia: I 652, Nebrodi (ME), Caronia, spring near Case Crocitti, 850 m, UTM VC 489 018, 24.06.1988, slide. Paratypes: same site and date, 1/1/0 slide (NHMW); 0/1/0 slide, 7/13/0 in liquid (SMF).   
 Further material: Calabria: I 1064 b, 3/14/0 (3/3/0 slide); I 1103, 1/2/0 (1/1/0 slide); I 1104, 1/0/0 slide; I 1106, 0/1/0 slide; I 1107, 4/15/0 (2/2/0 slide); I 1110, 2/4/0 (1/1/0 slide); I 1126, 10/12/0 (1/2/0 slide); I 1127 b, 5/6/0 (1/1/0 slide); I 1130, 1/2/1; I 1131, 6/20/0 (1/1/0 slide); I 1134, 3/2/0; I TG 18-03a, 0/1/0; Sardegna: I TG 15-03, 1/1/1 slide; Sicilia: Etna, Nebrodi, Peloritani; I 59, 0/1/0 slide; I 517, 3/0/0 slide; 531, 3/0/0 (1/0/0 slide); I 545, 0/2/0 (0/1/0 slide); I 568, 1/0/0 slide; I 594, 2/0/0 (1/0/0 slide); I 596, 0/2/0 (0/1/0 slide); I 605, 1/0/0 slide; I 617, 0/2/0 slide; I 627, 0/1/0 slide; I 628, 1/1/0 (1/0/0 slide); I 642, 0/1/0 slide; I 647, 0/2/0 slide; I 652, 9/15/0 (2/2/0 slide); I 657, 1/0/0 slide. 27 sites, 169 specimens.   
 Previous records, published under the name of A. allgaier (see Gerecke 2014b): Corsica: F 35, 1/0/0; F 79, 0/3/0; F 83b, 1/5/0; F 84, 3/3/0. Sardegna: I 1155, 1/0/0; I 1159, 0/1/0; I 1160, 1/0/0; I 1162, 1/0/0; I 1172, 1/0/0.   
Diagnosis: Dorsal integument lineated; muscle insertions and excretory pore, smooth; Vgl-1+2 close to each other, often fused, but occasionally separate as a matter of individual variability (Fig. 6 C). Genital field with Ac in a weakly curved line (Figs 6 D, 7 C). Proportions of I-L (Figs 6 A, 7 A) and palps (Figs 6 B, 7 B) with weakly developed sexual dimorphism. I-L-5 distinctly enlarged near insertion of S-1, distance S-1-2 wide, S-1 long and slender, apically enlarged and truncated, the adaxial margin in central part weakly protruding, at distal edge forming an obtuse extension; S-2 with an obliquely truncated tip. I-L-6 curved, with subparallel dorsal and ventral margins. P-4 maximum H on the level of proximoventral seta, sword seta near distoventral seta. Males: Genital field anterior margin convex, posterior margin slightly concave (Fig. 6 C-D). Palp stout, P-2 ventral margin distally forming an obtuse angle (Fig. 6 B). Females: Palp slenderer than in male, P-2 ventral margin straight to very weakly convex, ventrodistal angle acute (Fig. 7 B).  
Description: Dorsal integument strongly lineated; lateral eyes well developed and pigmented; dorsal and posteroventral muscle insertions, as well as excretory pore, smooth; glandularia not extended, diameter about 25. Vgl-1+2 close to each other, generally in touch, in mature specimens often fused (individual variability: frequently fused on one side, but separate on the other). Coxal plates in three groups. Posterior margin of Cx-I+II broadly convex, posterior apodemes of Cx-I forming an obtuse angle. I-L-5 distinctly enlarged near insertion of S-1, ventral seta close to distoventral edge (distal L 8-14 % total L); distance S-1-2 wide, S-1 apically widened and truncated, the adaxial side weakly protruding in central part and forming an obtuse extension at distal edge; S-2 distinctly stouter, maximum width in basal third, with an obliquely truncated tip. I-L-6 curved, proximally only slightly thicker than in the centre and apically. Genital field with Ac in a weakly curved line. Gnathosoma with short rostrum, chelicera normal in proportions (L/H 4.7-5.5, basal segment/claw ratio 2.1-2.6). P-4 maximum H on the level of proximoventral seta, sword seta near distoventral seta; seta insertions dividing margin into two subequal and one shorter sector(s) (relative length in %: 23-42/31-54/13-23).  
 Fig. 6: Atractides castor sp. nov., type series ♂ (I 652). A, I-L-5/6; B, palp; C, venter; D, genital field. Scale bars: 100 µm.   
Males (n = 10): Idiosoma L/W 400-500/300-400; coxal field L/Cx-III W 240-270/270-300, Cx-I+II mL 70-90, lL 160-180, W 210-240 (mL/W ratio 0.30-0,40). Genital field broadly rounded (L/W 72-90/80-102, ratio 0.85-0.95) with about 15 pairs of setae; Ac-1-3 maximum diameter 16-28, 19-28, 14-24, gonopore L 45-55; anterior margin weakly convex, posterior margin very weakly concave. I-L with segments 3 and 4 forming broadly protruding, rounded distal sheaths covering the base of the subsequent segment. I-L-5 dL/vL 144-168/80-92, ratio 1.65-1.91, dorsal and ventral margins equally diverging from the base to S-1 insertion, ventral seta near S-1 (distance to distoventral edge 14 to 29 % vL); HA 40-50, HB 45-54, HC 68-80, ratio dL/HB 2.9-3.4. L (L/W) S-1, 90-108 (10.3-12.3), S-2, 63-73 (5.8-7.7), distance S-1-2, 28-43, ratio S-1 L/distance S-1-2, 1.4-1.5. I-L-6 L 122-152, HA 19-23, HB 16-18, HC 15-18, ratio L/HB 7.2-8.6; ratio I-L-5 dL/I-L-6 L 1.1-1.2. Palp rather stout, total L 225-261; proportions of segments (L/H, ratio, % total L): P-1, 24-28/21-25, 1.0-1.2, 10-12; P-2, 50-58/43-48, 1.15-1.35, 22-24; P-3, 45-60/34-38, 1.2-1.7, 19-23; P-4, 76-88/29-36, 2.2-3.0, 33-35; P-5, 25-30/9-13, 1.0-3.0, 11-12; L ratio P-2/P-3, 0.96-1.22, P-2/P-4, 0.63-0.72; P-3/P-4, 0.55-0.69. P-2 ventral margin projecting in distal part to form an obtuse angle; P-3 ventral margin nearly straight, P-4 maximum H on the level of proximoventral seta, position of sword seta in distal part, but rather variable (ratio distance to proximal/distal edge 1.8-3.0).  
Females (n = 11): Idiosoma L/W 490-700/370-530; coxal field L/Cx-III W 275-310/320-385, Cx-I+II mL 80- 100, lL 180-210, W 260-340 (mL/W ratio 0.24-0,40). Genital field (L 120-180) with bean-shaped acetabular plates (L/W 84-100/24-34, ratio 2.8-3.7); Ac-1-3 maximum diameter 16-32, 14-34, 20-28, pregenital sclerite a slender Napoleon-hat shape. I-L-3/-4 not forming distal sheaths. I-L-5 more inflated than in males, dL/vL 192-212/88-104, ratio 2.00-2.27, dorsal and ventral margins equally diverging from the base to S-1 insertion, ventral seta very close to S-1 (distance to distoventral edge 8 to 14 % vL); HA 60-70, HB 65-74, HC 108-120, ratio dL/HB 2.8-3.2. L (L/W) S-1, 133-148 (11.6-14.0), S-2, 83-93 (5.2-7.4), distance S-1-2, 58-63, ratio S-1 L/distance S-1-2, 1.4-1.7. I-L-6 L 184-196, HA 20-24, HB 15-21, HC 15-20, ratio L/HB 9.2-12.5; ratio I-L-5 dL/ I-L-6 L 1.0-1.2. Palp slenderer than in males, total L 270-300; proportions of segments (L/H, ratio, % total L): P-1, 25-33/25-30, 0.9-1.2, 9-12; P-2, 55-68/45-48, 1.2-1.4, 20-23; P-3, 63-73/35-38, 1.8-2.0, 23-24; P-4, 90-103/25-29, 3.2-3.6, 32-34; P-5, 28-34/10-14, 2.1-3.3, 10-11; L ratio P-2/P-3, 0.83-0.96, P-2/P-4, 0.60-0.71; P-3/P-4, 0.69-0.76. P-2 ventral margin straight, but forming a rounded distal edge; P-3 ventral margin straight, P-4 sword seta insertion: ratio distance to proximal/distal edge 2.3-3.3.  
 Derivatio nominis: See below, under Atractides pollux sp. nov.   
 Remarks: Atractides castor is similar to A. allgaier in the combination of a lineated integument, smooth muscle insertions and excretory pore, and I-L with enlarged penultimate segment bearing an apically strongly broadened sword seta S-1. Atractides allgaier (in parentheses) differs from the new species mostly in two aspects: (1) different proportions of the terminal segments of I-L, with I-L-5 shorter (dL in males 132-145, in females 178-188), but having a relatively longer ventral margin (ratio dL/vL in males 1.45-1.63, in females about 1.8) and sword setae more close to each other (S- 1-2 in males 17-25, in females 42-47); (2) palp segments generally more slender, segment P-3 relatively longer (L/H ratio P- 3 in females 2.1, in males 1.7; P-3 rel. L 24-25 %, P-3/P-4 ratio in males 0.73, in females 0.78). Male A. allgaier are furthermore clearly distinguished by the absence of a distoventral projection of P-2. Furthermore, a fusion of Vgl-1+2, frequently found in males and females of the new species, has never been observed in A. allgaier.   
Under the last point of view, specimens from Corsica and Sardinia are characteristic in having Vgl-1/2 always separate. Instead, they agree in the variability of most measurements and proportions of idiosoma sclerites and appendages.  
Habitat: Crenobiont. In shadowed rheohelocrenes at medium and higher altitude (430 to 1500 m); at two occasions, single finds in low order streams (I 1104, I 627).  
Distribution: Calabria, Pollino and neighbouring mountains; Sicily (here restricted to the north-eastern mountains); Corsica and Sardinia.  
 Fig. 7: Atractides castor sp. nov., paratype ♀ (I 652). A, I-L-5/6; B, palp; C, genital field. Scale bar: 100 µm.
description: Published as part of Gerecke, Reinhard, 2021, The water mites of the family Hygrobatidae (Acari, Hydrachnidia) in Italy, pp. 1-85 in Zootaxa 5009 (1) on pages 13-15, DOI: 10.11646/zootaxa.5009.1.1, http://zenodo.org/record/5157635