Schistonchus altissimus, Zeng & Ye & Huang & Li & Giblin-Davis, 2013

Zeng, Yongsan, Ye, Weimin, Huang, Jianghua, Li, Changhui & Giblin-Davis, Robin M., 2013, Description of Schistonchus altissimus n. sp. (Nematoda: Aphelenchoididae), an associate of Ficus altissima in China, Zootaxa 3700 (4), pp. 561-572 : 565-570

Description of Schistonchus altissimus 1 n. sp.

(Figs 3, 4)

Measurements. See Table 1 .

Material examined. Holotype male, paratype male, paratype entomophilic female and paratype reproductive female deposited in the Department of Nematology, University of California, Riverside, CA, USA.

Type materials were collected from phase C–D syconia from a single tree of Ficus altissima in the residential area of Huajingxincheng , Guangzhou, (23°8’45.50”N, 113°21’48.50”E), Guangdong Province, P. R. China, on November 22, 2012.

One paratype each of a male, entomophilic female and reproductive female deposited at the Department of Nematology , University of California, Davis, CA, USA; and the Nematology Laboratory, USDA, ARS, Beltsville, MD, USA, and the remaining type materials were deposited in the Plant Pathology Laboratory, Department of Plant Protection , Zhongkai University of Agriculture and Engineering, Guangzhou, P. R. China.

Description. Males (from figs). Body cylindrical, posterior end strongly curved ventrally when heat-killed. Cuticle with fine annulation, annuli about 1 µm wide at mid-body. Three incisures visible in lateral field under light microscopy. Head slightly offset. Amphids prominent, situated laterally on the head, 3–4 µm from anterior. Amphid structure indistinct under light microscope. Stylet 15–18 µm long, robust, conus 57–75% of total stylet length, with strong, sub-diamond-shaped basal swellings (knobs) smoothly connected to shaft. Procorpus subcylindroid, 1.5–2.0 times as long as stylet. Metacorpus well-developed with valve posterior to centre. Excretory pore (EP) near the lip or head. Dorsal pharyngeal gland well-developed with one lobe, overlapping intestine, one gland nucleus observed. Pharyngo-intestinal junction with small and vague valve apparatus just posterior to metacorpus. Dorsal pharyngeal gland orifice indistinct under light microscope. Deirids and hemizonid not observed. Testis usually reflexed to left of intestine, anterior part usually reflexed once to right, vas deferens not clearly differentiated from seminal vesicle in specimens with less developed reproductive systems. Sperm amoeboid (4–5 µm by 2–3 µm). Spicules slender, paired, separate, hook-shaped with a thorn-shaped rostrum, arcuate. Capitulum strongly bent towards the lamina or depressed. Condylus small, rounded, rostrum prominent, conical to pointed, lamina dorsal line smoothly and symmetrically curved, calomus smoothly curved, junction of rostrum and calomus slightly angular to smoothly rounded. Spicule tip finely rounded, with cucullus. Gubernaculum absent. Three pairs of papilla-shaped subventral caudal papillae, one pair adcloacal, one pair postcloacal mid-distance between cloacaand tail tip, one pair near tail tip. Tail conoid, length 1.6 times cloacal body diam., tail tip rounded, without a mucron. Bursa or bursal flap absent.

Entomophilic female from figs (presumed to be associated with fig wasp pollinators for dispersal): Body cylindrical, straight or slightly ventrally arcuate when heat-killed. Cuticle, lateral field, head, stylet, pharynx and intestine similar to male. EP 7–11 µm posterior to anterior end, near the lip or head. Deirids, hemizonid and phasmids not observed. Vulva posteriorly situated at 69–77% of total body length. Vagina slightly anteriorly directed. Ovary situated on left of intestine, monodelphic, prodelphic, outstretched, without reflex. Uterus long, smooth, crustaformeria absent. Oviduct with ovoid spermatheca filled with sperms, Oocytes in single file throughout most of ovary. Post-uterine sac (PUS) short, one-third vulval body diam. (VBD) long. Tail bluntly conoid, length 3.1–4.7 times body diam. at anus (ABD), tail tip broadly rounded with a mucron.

Reproductive female (from figs): Body ventrally arcuate or C-shaped when heat-killed. Features of cuticle, lateral field, head, stylet, pharynx, EP and tail similar to entomophilic female. Vulva posteriorly located at 70–77% of total body length, vulval lips slightly protruding. Ovary situated on left of intestine, anterior part usually reflexed once to right, monodelphic, prodelphic, well-developed. Uterus long, smooth, crustaformeria absent. Oviduct with ovoid spermatheca. Oocytes in single file throughout most of ovary. PUS length one-third diameter of body at vulva (VBD). Tail conoid, length 2.2–4.8 times ABD, tail tip rounded with a mucron.

Diagnosis and relationships. Schistonchus altissimus n. sp. is typologically characterised by the combined characters of a short PUS (4.5–8 µm or 0.1–0.4 VBD long), and conoid tail with a mucron in females; excretory pore located near the lip or head; amoeboid sperm, conoid tail without mucron, three pairs of subventral papillae, no gubernaculum, strongly recurved spicules with a thorn-shaped rostrum and capitulum strongly bent towards the lamina and a cucullus on the tip in males. It is also distinguished by its biogeography and Ficus host species, being collected from F. altissima in southern China in association with the pollinator fig wasp E. altissima . Its status as a distinct species is corroborated by unique molecular sequences of partial SSU and the LSU D3 expansion segment ( Figs 1 , 2 ).

Schistonchus altissimus n. sp. is typologically distinguished from all other described species except S. microcarpus by having a spicule with a cucullus on the tip. It has a PUS 0.1–0.4 VBD long in females. Species with a similar PUS are S. aculeata and S. microcarpus , which also have a PUS <0.4 VBD in reproductive females. Schistonchus altermacrophylla , S. aureus , S. laevigatus , S. centerae , S. virens , S. hirtus and S. benjamina have a PUS 0.4–0.6 VBD long in reproductive females, i.e., tend to be slightly longer. Schistonchus superbus , S. africanus Vovlas, Troccoli, van Noort & van den Berg 1998 , S. fleckeri Davies, Bartholomaeus, Kanzaki, Ye & Giblin-Davis 2013 , S. racemosa Reddy & Rao 1986 , S. caprifici and S. cassowaryi Davies, Bartholomaeus, Kanzaki, Ye & Giblin-Davis 2013 , have a PUS 0.7–1.0 VBD long in females, i.e., longer again. Females of all other reported species of Schistonchus , including S. guangzhouensis , S. baculum , S. macrophylla , S. osmani Anand 2002 and S. hispida Kumari & Reddy 1984 have a PUS>1.0 VBD long.

In having the EP opening near the lips or head, S. altissimus n. sp. is similar to S. aculeata , S. altermacrophylla , S. aureus , S. benjamina , S. centerae , S. fleckeri , S. laevigatus , S. microcarpus and S. virens . However, S. altissimus n. sp. differs from S. aculeata by having a longer stylet (17–22 vs 13–17 µm) in reproductive females, and a spicule tip with vs without a cucullus in males; from S. altermacrophylla by having a shorter PUS (£0.4 vs 0.6 VBD long) in females, a smaller spicule (12–16 vs 18–24 µm), spicule tip with vs without cucullus, and tail tip without vs with mucron in males; from S. aureus by a shorter PUS (£0.4 vs 0.4–0.6 VBD long) in females, spicule tip with vs without cucullus, and tail tip without vs with mucron in males; from S. benjamina by having a shorter PUS (£0.4 vs 0.4–0.6 VBD long), fewer incisures in the lateral field (3 vs 4), spicule tip with vs without cucullus in males, and reproductive system with crustaformeria absent vs present, with spermatheca vs no true spermatheca in reproductive females; from S. centerae by possessing a shorter PUS (£0.4 vs 0.4–0.5 VBD long), a smaller spicule (12–16 vs 24–26 µm), and spicule rostrum distinct vs indistinct, and tip with vs without cucullus in males; from S. fleckeri by having fewer incisures in the lateral field (3 vs 4), spicule tip with vs without cucullus, tail tip without vs with mucron in males, and tail tip with vs without a mucron in females; from S. laevigatus by having a shorter PUS (£0.4 vs 0.4–0.6 VBD long) in females, and spicule tip with vs without cucullus in males; from S. microcarpus by having a smaller spicule (12.0–16.0 vs 16.0–18.5 µm), 3 distinct vs indistinct incisures in the lateral field, and tail tip in males without two morphotypes vs with two morphotypes; and from S. virens by having a longer stylet (16–22 vs 14–16 m) in females, and spicule tip with vs without cucullus in males.

Schistonchus altissimus n. sp. has amoeboid sperm similar to S. aculeata , S. africanus , S. altermacrophylla , S. aureus , S. baculum , S. benjamina , S. cassowaryi , S. centerae , S. fleckeri , S. fistulosus , S. guangzhouensis , S. hirtus , S. laevigatus , S. microcarpus , S. superbus and S. virens , but differing from the ‘flagellate’ sperm of S. caprifici , S. macrophylla , S. osmani , and S. racemosa .

Males of S. altissimus n. sp. have three pairs of papillae (one pair adcloacal, one pair halfway between cloacal aperture and tail terminus, and one pair near the tail tip), similar to the arrangement in S. aculeata , S. aureus , S. benjamina , S. fistulosus , S. fleckeri , S. hirtus , S. laevigatus , S. microcarpus and S. virens . However, it differs from the situation in S. africanus , S. altermacrophylla , S. caprifici , S. centerae and S. macrophylla , in which one pair is precloacal, one pair adcloacal, and one pair postcloacal, and from S. cassowaryi in which one pair is pre-cloacal, one almost lateral at mid-tail, and one subventral near the tail tip.

Figures

FIGURE 1. The 10001st Bayesian tree inferred from 18S under GTR+I+G model (-lnL=11975.4033; freqA=0.2441; freqC=0.2019; freqG=0.2693; freqT=0.2847; R(a)=1.2631; R(b)=2.7232; R(c)=1.4524; R(d)=0.8901; R(e)=4.1822; R(f)=1; Pinva=0.2115; Shape=0.6746). Posterior probability values exceeding 50% are given on appropriate clades.

FIGURE 2. The 10001st Bayesian tree inferred from D3 under GTR+I+G model (-lnL=2302.1172; freqA=0.2692; freqC=0.1707; freqG=0.2793; freqT=0.2809; R(a)=1.2318; R(b)=4.7041; R(c)=2.0052; R(d)=0.951; R(e)=7.4182; R(f)=1; Pinva=0.3515; Shape=0.568). Posterior probability values exceeding 50% are given on appropriate clades.