Cactodera tianzhuensis, Li & Li & Ni & Shi & Wei & Liu & Zhang & Peng, 2021

Li, Wenhao, Li, Huixia, Ni, Chunhui, Shi, Mingming, Wei, Xuejuan, Liu, Yonggang, Zhang, Yiwen & Peng, Deliang, 2021, A new cyst-forming nematode, Cactodera tianzhuensis n. sp. (Nematoda: Heteroderinae) from Polygonum viviparum in China with a key to the Genus Cactodera, Journal of Nematology 53 (1), pp. 1-15 : 6-9

CaCtOdera tianZhUenSiS n. sp. is named after the type locality of its isolation.

Diagnose and relationships

CaCtOdera tianZhUenSiS n. sp. is characterized by lemon-shaped or rounded cysts that have protruding necks and vulval cones. The cysts are Ca 571 (511– 761) µm long ×454 (361–558) µm wide and with a circumfenestrate vulval cone, vulval denticle present but bullae and underbridge often absent, anus distinct. Cysts containing 90– 160 eggs. Second-stage juveniles are vermiform, slightly curved ventrally and Ca 539 (495–592)µm long, stylet well-developed with the rounded stylet knobs to slightly concave anteriorly. Lateral field with four incisures. Genital primordium situated at 58–63% of body length. Tail gradually tapering to a finely rounded terminus with Ca 54 (47–59) µm long, outline of hyaline portion is V-shaped or U-shaped. Egg shells without visible markings or punctations, body of developed J 2 in eggs folded about five times.

The new species belongs to the genus CaCtOdera , up to now, the genus CaCtOdera contains seventeen species (including C. tianZhUenSiS n. sp.). These species are similar in circumfenestrate fenestration, without bullae and underbridge, lateral field of J2 with four incisures. Morphologically, C. tianZhUenSiS n. sp. is closest to C. thOrnei with many overlapping morphometrics, such as cyst size, the length of J2 body, DGO, stylet, tail and hyaline tail, but differs from C. thOrnei in fenestral diam. (20–32 vs 31–36 μm) for cyst and eggshell surface (smooth vs punctate). C. tianZhUenSiS n. sp. is similar to C. CaCti , but differs from this species in the longer DGO (4.0– 6.5 vs 2.9–4.4μm), the longer length of hyaline tail (22–29 vs 14–21μm) and eggshell surface (smooth vs punctate). In addition, C. tianZhUenSiS n. sp. can be easily distinguished from several species of CaCtOdera , namely C. ChenOpOdiae , C. eremiCa , C. eVanSi , C. galinSOgae , C. milleri , C. rOSae and C. SOlani by eggshell surface smooth vs punctate.

Stage Character

Cyst

n

L (excluding length)

Diam.

L/Diam.

Fenestral diam.

Second-stage juvenile

n

Body length

Body width at mid-body a

b

c

c′

Lip region height

Lip region diam.

Stylet length

Stylet base height

Stylet base width

Median bulb from anterior end (MB)

Holotype Paratype

20

531 571.2 ± 79.1 (511.0–761.0)

429 454.3 ± 56.8 (360.5–558.0) 1.23 1.3 ± 0.1 (1.1–1.6)

22.8 23.4 ± 3.8 (20.0–31.5)

20

538.5 ± 25.0 (494.5–591.5) 23.2 ± 1.4 (20.0–25.0)

23.4 ± 2.0 (20.6–27.2) 3.7 ± 0.3 (3.1–4.2)

10.0 ± 0.8 (8.4–11.6) 3.9 ± 0.3 (3.5–4.5)

4.8 ± 0.4 (4.0–5.0)

10.7 ± 0.8 (9.0–12.0) 24.9 ± 0.8 (22.5–26.0)

2.5 ± 0.3 (2.0–3.0) 5.1 ± 0.54 (4.0–5.5) 77.8 ± 4.2 (69.5–85.0)

Opening of dorsal pharyngel gland from 4.9 ± 0.5 (4.0–6.5)

stylet base ( DGO)

Excretory pore from anterior end ( EP) Median bulb width ( MBW)

Diam. at anus

Tail length

Hyaline portion tail

L/ MB

TL/H

111.2 ± 6.2 (97.5–124.0) 11.8 ± 1.1 (9.5–13.5) 13.8 ± 0.5 (11.5–15.0)

54.1 ± 3.6 (46.5–59.0) 25.8 ± 2.1 (21.5 –28.5)

6.9 ± 0.5 (6.1–8.0)

2.1 ± 0.2 (1.8–2.4) Egg

n

Length

Width Length/Width

20 117.9 ± 11.6 (101.5–144.0)

51.3 ± 4.1 (41.0–61.5) 2.3 ± 0.3 (1.9–2.9)

Note: All measurements are in μm, and in the form: mean ± standard (range).

It can be distinguished from C. radiCale , C. Salina and C. tOrreyanae by vulval denticles present vs absent.

Any other species than mentioned above of the genus CaCtOdera , C. tianZhUenSiS n. sp. can be distinguished from C. aCnidae by shorter fenestral diam. (20–32 vs 30–33μm), longer J2 body length (495–592 vs 361–448μm), DGO (4.0–6.5 vs 2.5– 3.0 μm), and tail length (47–59 vs 43–48 μm). It differs from C. amaranthi by longer J2 body length (495–592 vs 340–460 μm), stylet length (23–26 vs 20–21μm), tail length (47–59 vs 43–48μm), and hyaline tail length (22–29 vs 12–16 μm). C. tianZhUenSiS n. sp. is different from C. eStOniCa by a smaller L/W cyst ratio (1.1–1.6 vs 2.0–2.4), longer J2 body length (495–592 vs 426– 465μm), DGO (4.0–6.5 vs 3.4–4.3 μm), tail length (47–59 vs 36–44 μm), and hyaline tail length (22–29 vs 14–21 μm). It differs from C. WeSSi by smaller L/W cyst ratio (1.1–1.6 vs 1.2–2.3), longer J2 body length (495–592 vs 426–465μm), stylet length (23–26 vs 20–22μm), tail length (47–59 vs 43–50μm), and hyaline tail length (22–29 vs 17–24μm).

In addition, comparative important morphological and morphometric characters of C. tianZhUenSiS n. sp. with sixteen valid species of the genus CaCtOdera are listed in Table 2.