Sinaxonopsis unicucrus Yi & Jin, 2012

JiaK, Lan, LiK, Hai-Tao & K, Jian-Jun Guo, 2024, Two species representing a rare genus Sinaxonopsis (Acari, Hydrachnidiae, Aturidae) from China, with discussion of some taxonomic features, Acarologia 64 (2), pp. 554-574 : 555-565

publication ID	https://doi.org/ 10.24349/orqe-mqh
publication LSID	lsid:zoobank.org:pub:27F5A3C9-FC58-47CA-AE05-6309DF752E46
persistent identifier	https://treatment.plazi.org/id/03E28502-3828-3946-FE59-FA28FC06FAFC
treatment provided by	Felipe
scientific name	Sinaxonopsis unicucrus Yi & Jin, 2012
status

Treatment

( Figures 1–12 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 View Figure 8 View Figure 9 View Figure 10 View Figure 11 View Figure 12 )

Habitat — Slow flow of stream, many pebbles covered by mosses at the bottom.

Material examined — 3♂, 9♀, Baotianman National Nature Reserve, Nanyang City,

Henan Province, P. R. China (33°46′73″ N, 111°89′98″ E, 555 m a.s.l.), collected by Hai-Tao

Li, 11-VI-2021. Slides No. HN-AT-2021061101–2021061112.

Description — Male (n=3). Idiosoma oval, slightly truncate at anterior end; dorsal and ventral shield present and this last with a conspicuous concavity ( Figures 1 View Figure 1 and 2 View Figure 2 ). In dorsal view ( Figures 1A View Figure 1 and 2A View Figure 2 ): dorsal shield formed by one pair of anterior platelets and a large posterior plate; anterior platelets bearing the lateral eyes, O 2, A 2 and D 1 ; posterior plate bearing six pairs of glandularia (D 2 –D 4, L 2 –L 3 and V 4), setae of A 2, D 1 –D 3, L 2 –L 3 all far away from glands, numerous longitudinal stripes, and two eyepatch-like violet spots, of which the anterior one is larger and covering almost 1/3 of the entire dorsal shield, and the posterior one situated at the end of the body; excretory pore protruding, located at the posterior end of the dorsal shield. In ventral view ( Figures 1B View Figure 1 and 2B View Figure 2 ): coxal plate single; tips of Cx-I not extending beyond the frontal margin; Cx-IV with distinct suture lines; suture line of Cx-III/IV ending medially to

IV-L insertions and not reaching the medial line; C 2 located at the posterior margin of Cx-II where suture line of Cx-II/III convex latero-posteriorly ( Figure 3C View Figure 3 ); Cx-IV well extended posteriorly with round posterior margin and laterally with a ridge; IV-L basal segmental fossa without ankles. Genital field ( Figure 3A View Figure 3 ) triangular and slightly depressed, fused to ventral shield; gonopore elongated and somewhat projecting, anteriorly with several genital hairs; with multiple acetabula located on both sides of gonopore to the posterolateral area of idiosoma; C 4 located at either side of posterior part of genital pore ( Figure 3E View Figure 3 ).

Gnathosoma with pointed dorsal apodemed, ventral apodeme blunt and almost equal in length, with two pairs of setae at the tip of the rostrum ( Figure 3B View Figure 3 ). Cheliceral two-segmented, chelicera claw curved knife in shape ( Figure 1G View Figure 1 ).

Palp five-segmented ( Figure 4 View Figure 4 ); P-1 with one dorsal seta on the inner side; P-2 with two dorsal setae on the outer side, three dorsal setae on the inner side; P-3 short, with three dorsal setae on the outer side; P-4 longest, basally and distally concave on venter, medially convex with a pair of long setae.

Legs six-segmented; ventral margin of I-L-6 and II-L-6 with dense small setae; claws with one dorsal and one ventral clawlet ( Figures 5 View Figure 5 , 8A and 8B View Figure 8 ); III-L and IV-L exhibiting significant sexual dimorphism; III-L-4 with four large setae at the end of the outer side, two of which are blunt and cylindrical; III-L-5 ending in one large cylindrical seta curved towards the ventral surface on the outer side; III-L-6 ventrally curved, with a pair of heteromorphic claws ( Figures 6 View Figure 6 and 8C View Figure 8 ). IV-L-4 with a developed irregular protrusion and four large setae at the end of the outer side, the two last of which are blunt and cylindrical; IV-L-5 with one cylindrical seta at the end; lateral margin with a row of setae neatly arranged; IV-L-6 terminally enlarged, with a particularly well-developed dorsal process; features of the claws the same as I-L and II-L ( Figures 7 View Figure 7 and 8A View Figure 8 ).

Female (n=9). Characteristics almost similar to male, except for the following: from the lateral view, the ventral margin of idiosoma straight, without concavity ( Figure 1F View Figure 1 ); genital field well developed and situated at the ventral end of the body ( Figures 1E View Figure 1 , 2E View Figure 2 and 10A View Figure 10 ); gonopore large and terminally located ( Figure 10B View Figure 10 ); V 3 more anteriorly located, and lateral to the genital field ( Figures 10A and 10E View Figure 10 ), and C 4 located anteriorly on both sides of the gonopore ( Figure 10C View Figure 10 ). III-L-4 terminally with one long swimming seta and several additional setae; III-L-5 with two long swimming setae and two short pointed setae ( Figures 12A and 12B View Figure 12 ); IV-L-4 terminally with one long swimming seta and six large additional setae; IV-L-5 terminally with two long swimming setae and five large additional setae, and with a row of setae inserted on lateral margins ( Figures 12C and 12D View Figure 12 ).

Measurements — Male (n=3). Idiosoma L/W 521 (521–566)/442 (442–497); anterior platelets L/W 221 (221–222)/78 (78–89), posterior plate L/W 407 (407–444)/411 (411–446); gnathosomal bay L 136 (136–152); gonopore L/W 71 (71–72)/21 (21–24), ratio 3.36 (3.0–3.36). gnathosoma vL 127 (127–139), dL 145 (145–146); chelicera total L 141 (141–168), claw L 50 (50–52), basal segment L 107 (107–123), L basal segment/claw ratio 2.14 (2.14–2.45). Palp: dL/H, dL/H ratio: P-1, 42 (42–43)/27 (27–29), 1.44 (1.44–1.59); P-2, 83 (83–84)/29 (29–30),

– Lateroglandularia 3 (L 3).

2.88 (2.80–2.88); P-3, 45 (42–45)/25 (25–26), 1.79 (1.61–1.79); P-4, 120 (120–124)/23 (21–

23), 5.32 (5.32–5.83); P-5, 46 (46–47)/17 (17–18), 2.61 (2.61–2.79); Legs: dL of I-L-1–6:

57 (57–58), 59 (55–59), 78 (78–83), 116 (116–119), 143 (143–144), 149 (149–156); dL of

II-L-1–6: 56 (56–59), 60 (60–62), 88 (88–91), 131 (131–133), 164 (161–164), 170 (166–170);

dL of III-L-1–6: 78 (78–80), 61 (56–61), 94 (94–106), 102 (99–102), 195 (195–198), 182 (177–182); dL of IV-L-1–6: 98 (98–123), 134 (122–134), 192 (192–207), 103 (103–113), 230 (225–230), 198 (198–206).

Female (n=9). Idiosoma L/W 572–654/463–525; anterior platelets L/W 217–238/76–84, posterior plate L/W 455–507/430–489; gnathosomal bay L 159–171, gnathosoma vL 122–146, dL 146–158. Palp: dL of P-1–5, 47–51, 82–94, 41–45, 114–125, 44–45. Legs: dL of I-L-1–6: 47–56, 50–56, 63–70, 94–105, 113–122, 118–134; dL of II-L-1–6: 51–53, 52–57, 69–73,108–

111, 131–144, 138–146; dL of III-L-1–6: 56–63, 54–55, 72–74, 107–116, 138–141, 143–145;

dL of IV-L-1–6: 94–109, 76–85, 109–119, 112–124, 148–164, 136–155. Remarks — The specimens from Henan Province were identified as S. unicucrus Yi &

Jin, 2012 due to the following characteristics: (1) dorsal shield formed by one pair of anterior platelets and a large posterior plate; (2) III-L-4 with two blunt and cylindrical setae at the end; (3) III-L-5 terminally with one large cylindrical seta curving toward the ventral surface; (4) III-L-6 with a pair of heteromorphic claws; (5) IV-L-4 with a developed irregular protrusion and four large setae at the end; (6) IV-L-5 with well-developed protrude collar and three heteromorphic setae at the end, the nearest to the back is cylindrical and much thicker than the other two; (7) IV-L-6 with a particularly well-developed dorsal process ( Yi and Jin 2012).

The species was firstly discovered in Anhui Province, which is the neighbor of Henan Province. Meanwhile, the species was redescribed in this paper, due to the lack of some important characteristic information, e.g. the glandularia, the patches of the large posterior dorsal plate, etc.

Distribution — China (Anhui, Henan).