Parajapyx pauliani Pages , 1959

Bu, Yun, Gao, Yan, Potapov, Mikhail B. & Luan, Yun-Xia, 2012, Redescription of arenicolous dipluran Parajapyx pauliani (Diplura, Parajapygidae) and DNA barcoding analyses of Parajapyx from China, ZooKeys 221, pp. 19-29 : 21-24

Parajapyx pauliani Pages, 1959 Figs 1-17Tables 23

Material examined.

4 females, South China, Hainan Island, Sanya city, shingly beach of Ximaozhou island (samples No. 6 and 8), 18°14'N, 109°22'E, 5-IV-2011; 1 female, from sand beach of the Ximaozhou Island (sample No. 17), 6-IV-2011; 2 female, South China, Hainan Island, Changjiang County, Changhua town, from sand beach of Qizi Bay (sample No. 54), 19°21'N, 108°40'E, 7-IV-2011, coll. Y. Bu, C. W. Huang, M. B. Potapov and N. A. Kuznetsova. All specimens are kept at Institute of Plant Physiology & Ecology, CAS.

Redescription.

Body length and width of adult female 2.8-3.0 mm, and 0.3-0.35 mm, respectively (four specimens, antenna and cerci not included). Tegument smooth, without ornamentation (Fig. 1).

Head.

Length 0.23-0.25 mm, width 0.23-0.25 mm. Dorsal side with 5+5 interior (Di), 5+5 exterior (De), and 10+10 lateral setae (Dl) (only show five on the picture), without front setae (Fig. 2). Labrum with two pairs of medial setae (1+1 M and 1+1 n), 6+6 m. On ventral side internal lobe (li) with 1+1 m; external lobe (le) with 9 +9 setae; coxae (cx) with 1 M and 3n; labial palpus absent, replaced with 1 M accompanied by two normal seate; admentum with 11 setae, 3 M and 8 n; pli oral region with 4-5 setae; submentum with 2+2 setae (Fig. 3).

Mouthparts. Lacinia composed by five lobes, the first lobe (distal) is very acute and smooth, and the following four larger and pectinate. Mandible with five teeth and three denticles between them. Maxillary palpus with 10 n and 2 m setae.

Antenna with 21 segments, length 0.8 mm. Antenna segment I with seven microsetae dorsally and 5 setae, Ant. II and III each with 9 setae, Ant. IV with 11 setae, Ant. I-IV without sensilla and trichobothria, Ant. V with two bacilliform sensilla (BS) and 14-17 setae, Ant. VI with three BS and 16-18 setae, Ant. VII with three BS and 17-20 setae; Ant. VIII-XIX each with 4 BS and 18-28 setae, Ant. XX with 6 BS and 34-35 setae, Ant. XXI with eight BS and four placoid sensilla, and 55-60 seate. Single microsensillum asymmetrically present on Ant. IX-XIII, XVII, and XIX.

Thorax. Chaetotaxy of thorax as show in Table 2, 3. Pro-, meso- and metanotum each with 5+5 M setae and 6-17 n setae (Figs 4-6). Pro-, meso- and metasternum as show in Figs 7-9. Leg III length 0.3 mm, coxa with 1 M, 3 n and 2 m; trochanter with 1 M and 2 n dorsally, 1 m ventrally; femur with 10 n and 3 m setae; tibia with 8 n; tarsus with 10 n; claw symmetrical and with single medial unguis.

Abdomen. Chaetotaxy of the abdomen as shown in Table 2 and 3. Urotergite I (Fig. 12): prescutum with 4+4 m and 2+2 n, scutum with 6+6 m, 5+5 M and (10-14)+(9-14) n. Urotergites II-VII (Figs 13-14): prescutum with 4+4 m and 2+2 n, scutum with (6-8)+(6-8) m, 8+8 M and (9-18)+(9-19) n. Urotergite VIII with 12+12 m, 8+8 M and (9-10)+2(3)+(7-13) n. Urotergite IX with 7+7 m, 3+3 M and 2+1+2 n. Urotergite X with 4+4 m, 6+1+6 M and (6-8)+(6-8) n.

Urosternite I (Fig. 15): prescutum with 2+2 m and 5 +5 n, scutum with 5+5 m, 10+10 M and (10-18)+1(2)(3)+(11-18) n. Subcoxal organ composed by 10-13 setae, including 6-8 slender glandular setae and 4-5 sensory setae, without medial glandular organ (Fig. 11). Urosternites II to VII (Figs 16-17): prescutum with 4 +4 m and (5-7)+1+(5-7) n setae, scutum with 5 +5 m, 12 +12 M, (7-12) + 2(3)+(6-11) n. Urosternite VIII with 4+4 m, 2 +2 M, (4-5)+(4-5) n. Urosternite IX with 4+4 m, 2 +2 M and 3+3 n. Urosternite X with 4 +4 m, 6+6 M and 3+1+3 n. Eversible vesicles present on the urosternites II-III, diameter 32-37 μm. Styli on urosternites I-III each with one short sensilla and one m seta, on urosternites IV-VII with single seta m. Female genital papilla with 10+2+10 n.

Cerci (Fig. 10) singly segmented, symmetrical, with five distinct internal teeth, crooked; t3 larger than others; interval between t1-t2 as two times as t2-t3 and t3-t4; t2-t4 with shoulder, dorsal side with 9 M, 5 n and 5 m, ventral side with7 M, 3 n and 3 m; each cercus with 7-8 evaporation plates.

Distribution.

So far, the species is known only from two localities: Hainan, China and Madagascar.

Remarks.

Parajapyx pauliani is characterized by the antenna with 21 segments, nota each with 5+5 M setae and numerous normal setae, urotergites II-VII each with 8 +8 M setae and numerous normal setae, and prescutum of urotergites II-V each with 2+2 normal setae. Ithas more normal setae than in other congeners. The numbers of M and m setae are relatively stable, but the numbers of normal setae are quite variable in different individuals.

Littoral habitat of Parajapyx pauliani

Three intertidal locations where Parajapyx pauliani was found are shown in Figs 18-20. All habitats are positioned lower than supralittoral, devoid of halophytes, and are directly influenced by sea water. The animal lives in shingly or sand beaches (Figs 18-20), between particles of different size: from 9 mm (with the whole variation from 5 to 16 mm, n=100) to 1.5 mm (1.0-2.3 mm, n=150) in diameter. Parajapyx pauliani appears to be a dipluran member of a genuine littoral community and is often associated with collembolan species like Yuukianura sp., Isotogastrura trichaetosa Potapov et al. 2011, Thalassaphorura sp., Oudemansia sp., Acherontiella sp., Archisotoma sp.

The DNA barcoding

The DNA barcoding of 18 individuals from five Parajapyx species from China were sequenced, and deposited in GenBank (the accession numbers showed in Table 1). The genetic divergence between individuals of the same species is 1.9% in average, with span 1.5-5.3%, and it is 19.1% in average, with span 16.3-21.3% between different Parajapyx species.

The Neighbour-joining tree was constructed based on the barcoding sequences (Fig. 21). Parajapyx pauliani is clustered with Parajapyx isabellae . Parajapyx isabellae and Parajapyx emeryanus are valid species respectively well supported by barcoding analyses. Two individuals of Parajapyx isabellae (Syn. Parajapyx paucidentis ) (teeth absent on the cerci) clustered together with five individuals of Parajapyx isabellae (teeth present on the cerci). The genetic divergence between Parajapyx isabellae (Syn. Parajapyx paucidentis ) and Parajapyx isabellae is only 1.7% in average (with span 0.8-2.6%). In addition, individuals of Parajapyx yangi and Parajapyx hwashanensis clustered together with high support value, and the genetic divergence between them is low (0.2%).