Thalassaphorura qixiaensis, Yan, Haijuan, Shi, Shidi & Chen, Jianxiu, 2006

Yan, Haijuan, Shi, Shidi & Chen, Jianxiu, 2006, A new species of the genus Thalassaphorura from East China (Collembola: Onychiuridae), Zootaxa 1369, pp. 35-41 : 36-40

Thalassaphorura qixiaensis sp. nov.

( Figures 1–16 )

Type material

HOLOTYPE: male (mounted on slide), China: Jiangsu Province: Nanjing: Qixiashan Park, alt. 440m, 14­X­1994, collection number C8420, collected by CHEN Jian­xiu. PARATYPES: 12 males and 78 females, C8419; all data as the holotype. All deposited in the Department of Biology, Nanjing University.

Description

Maximum body length: male 1.25 mm, female 1.72 mm. Body shape: cylindrical, Abd III and IV slightly swollen. Body color: pale yellow in alcohol. Integumental granulation fine and almost uniform. Dorsal granules 1.5–2.0 µm in diameter, ventral ones slightly smaller than those on dorsal side.

Pseudocelli (pso) arranged dorsally as 32/233/33343 ( Fig. 1 a), ventrally as 2/000/ 0 112. Cephalic dorsal chaetotaxy with seta d0 present and 3+3 setae between posterior inner pso. Post antennal organ (PAO) consisting of 21–30 simple, separate vesicles arranged vertically to long axis of organ, around narrow central granule­free groove ( Fig. 6 ). Antennal base not clearly demarcated, with 3 pseudocelli. Labral setae 4/1, 4, 2 ( Fig. 7 ). Labial palp with 5 papillate terminal sensilla, setae A & C thick and blunt (AC type after Fjellberg, 1999). Labial proximal setae 7. Labial triangular setae as 4 (E, F, G, and f) and 5 (b, c, d, e, e’) respectively in basomedian and basolateral fields (D’ Haese, 2003) ( Fig. 3 ). 4+4 setae present along ventral groove on mentum ( Figs. 2 ). Antennae cylindrical, 0.7–0.9 times length of cephalic diagonal. Length ratio of antennal segments as I: II: III: IV = 1: 1.3–2.5: 1.3–2.5: 3.6–5.2. Ant. III organ with 5 guard setae, 5 papillae, 2 subequal sensory rods and 2 straight, smooth, paddle­like clubs ( Fig. 5 ). Microsensillum (ms) of Ant. III present on lateral side and slightly behind sense organ ( Figs. 4 & 5 ). Ant.

IV without visible blunt sensory setae; subapical sense peg small, slightly expanded, beset in a shallow pit; ms on lateral side, at about 2/5 length from base.

Body chaetotaxy usually symmetrical. All setae smooth and in different sizes. Dorsal setae arranged roughly in 1 row on Th. I and 3 rows on Th. II­Abd. V. Sensilla not distinctly differentiated and invisible. Th. II–III respectively with 1+1 ms dorso­laterally. Abd. IV with median seta m0. Abd. V with a0. Abd. VI with 2 median setae (a0 and p0), a0 longer than a1 and about 1/2 length of a2 ( Fig. 1 a). Each thoracic segment ventrally with 1+1 setae between legs.

Subcoxal pso as 2, 2, 2 ( Fig. 1 a). Tibiotarsus with 9 setae in whorl 1 (distal whorl), 8 in whorl 2 (upper whorl) and 1 long anterior seta at base ( Fig. 9 ). Unguis without teeth. Unguiculus narrow and pointed, without basal inner lamella, and 0.7–0.9 times as long as inner edge of unguis ( Fig. 8 ).

Ventral tube with 6+6 or 7+7 setae (7+ 7 in 5 of 37 specimens) ( Fig. 10 ). Remnant of furca bearing 4 setulae arranged nearly in square and surrounded by 4 larger setae ( Fig. 11 ). Male ventral organ with 6–12 setae on Abd. II and 7–10 on Abd. III, usually arranged asymmetrically; setae short, broad and thin with apex pointed, ( Figs. 12 & 13 ). Genital plate with 42–55 small setae in male and 20–23 in female ( Figs. 14 & 15 ). Setae on anal valves as in Fig. 16 ; upper valve with 3, 2, 5 setae, 2 of 5 in posterior row very long. Anal spines strong, set on distinct papillae, about 4/5 times as long as inner edge of hind unguis ( Figs. 1 a & 1b).

Ecology

Under leaf litter, stones and bricks in deciduous forest.

Etymology

The new species is named after the type locality: Qixiashan Park.

Discussion

Morphologically, the new species is most similar to Th. encarpata , a species widely spread in North America, Europe and Hawaii. However, it differs from the latter in labial palp which is of AC type rather than A type and 7 labial proximal setae rather than 6 (after Fjellberg, 1999). The new species is gamogenetic since 13 males among 91 specimens were found in the present study while Th. encarpata is definitely parthenogenetic ( Christiansen & Bellinger1998).

The new species has the same dorsal and ventral pso formulae with the following 5 species: Th. franzi ( Stach, 1946) , Th. lifouensis ( Thibaud & Weiner, 1997) , Th. kwona ( Thibaud & Lee, 1994) , Th. tovtrensis (Kaprus’ & Weiner, 1994), and Th. zschokkei (Handschin, 1920) . However, it differs from the latter species by the characters in table 1.

The new species is also similar to the four known Chinese species, however, it is readily distinguished from them by the characters shown in table 2.

We are very grateful to Dr. R. J. Pomorski from Wrocaw University in Poland for his helpful comments on the manuscript and supply of literature. The present study was supported by the National Natural Science Foundation of China (No. 30370175).

Figures

FIGURES 1 – 6. Thalassaphorura qixiaensis sp. nov. 1, Dorsal chaetotaxy (1 a) and enlargement of anal spine (1 b). 2, Ventral side of head with pseudocelli and chaetotaxy. 3, Left side of labium. 4, Antenna, dorsal view. 5, Ant. III sense organ and microsensillum. 6, PAO and anterior cephalic pso.

FIGURES 7 – 16. Thalassaphorura qixiaensis sp. nov. 7, Labrum. 8, Apex of hind leg, lateral view. 9, Chaetotaxy of hind tibiotarsus, ventral view. 10, Ventral tube, lateral view. 11, Remnant of furca. 12, Male ventral organ. 13, Enlargement of setae in male ventral organ. 14, Male genital plate. 15, Female genital plate. 16, Anal region.