Paratrichodorus asidonaensis, Decraemer & Archidona-Yuste & Clavero-Camacho & Vovlas & Cantalapiedra-Navarrete & Alba & Ruiz-Cuenca & Castillo & Juan & Palomares-Rius, 2024

Decraemer, Wilfrida, Archidona-Yuste, Antonio, Clavero-Camacho, Ilenia, Vovlas, Alessio, Cantalapiedra-Navarrete, Carolina, Alba, Ruiz-Cuenca, Castillo, Pablo, Juan & Palomares-Rius, 2024, Unravelling cryptic diversity in the Paratrichodorus allius- group species complex to resolve eight new species of the genus and new insights on the molecular phylogeny % Nematoda: Trichodoridae), Zoological Journal of the Linnean Society 202 (3), pp. 1-44 : 21-25

Paratrichodorus asidonaensis sp. nov. Decraemer et al.

( Figs 3H , 10 , 11 ; Table 6 )

Zoobank registration: urn:lsid:zoobank.org:act:3BDC36BC-3F6E-4C09-9CBC-1ABF082A8978

Type material: Holotype. A female was chosen as holotype because males were rare; only two males (one dorso-ventral position) were found among 23 females and juveniles. Female extracted from soil samples collected from the rhizosphere of wild olive ( Olea europaea ssp. sylvestris ) at Medina Sidonia, Cádiz province, southern Spain (36°19 ʹ 55.2 ʹʹ N latitude, 5°51 ʹ 18.0 ʹʹ W longitude) by J. Martín Barbarroja and G. León Ropero, mounted in pure glycerine and deposited in the nematode collection of Ghent University, Ghent, Belgium (slide number UGMD 104459 ).

Paratypes: Female paratypes extracted from soil samples collected from the rhizosphere of wild olive at Medina Sidonia , Cádiz , southern Spain, were deposited in the following nematode collections: Ghent University, Ghent, Belgium (slide numbers male and females paratype UGMD 104459 , UGMD 104460 ); and one female paratype at the USDA Nematode Collection, Beltsville, MD, USA (collection number T-8019p ).

Additional material examined: An additional population was collected also in the rhizosphere of wild olive at Benalup-Casas Viejas, Cádiz province, Spain (36°18 ʹ 27.74 ʹʹ N latitude, 5°52 ʹ 56.40 ʹʹ W longitude).

Etymology: The species epithet refers to Asidona the visigothic name of Medina Sidonia, the type locality where the type specimens were collected.

Description of female: Body short (average <550 µm), straight, slightly tapered anteriorly to a low, rounded lip region with protruding double papillae (four cephalic and two subdorsal and subventral outer labial papillae), cuticle swollen (average 4 µm). Onchiostyle medium-sized (average 41 µm long). Pharynx at posterior isthmus widened to a posterior bulb, usually with a short (5–15 µm) dorsal overlap by the intestine or a combined short ventrosublateral overlap of pharyngeal glands (3; 15 µm) and dorsal intestinal overlap (5; 7 µm); dorsal gland nucleus variable in position but mostly in the anterior third of the bulb. Nerve ring close to pharyngostom; SE-pore opposite posterior isthmus or anterior pharyngeal bulb. Rectum nearly vertical, anus terminal.

Reproductive system didelphic, amphidelphic, with ovaries reflexed; sperm cells small with oval nucleus (about 2 µm long), accumulated at the tip of the ovary flexure (i.e. at level ovarial sac). Vulva a short longitudinal slit (2 µm) in ventral view, located posterior midbody at about 60% of total body length from anterior end. Vagina low, wide, rounded, half as long as wide and occupying less than one-fifth of the corresponding body diameter; vaginal sclerotized pieces minute (1.0–1.5 µm), triangular, obliquely oriented and about 2.5 µm apart; vaginal constrictor muscles weakly developed. No (sub)lateral body pores observed. Tail almost non-existant due to terminal anus and a pair of terminal caudal pores.

Description of male: Apparently rare (only one specimen found). Body straight, cigar-shaped with swollen cuticle (5 µm) upon fixation. Digestive system with minute dorsal intestinal overlap (5 µm) of pharynx. No ventromedian or lateral cervical papillae; SE-pore opposite narrow pharyngeal region. Nerve ring close to pharyngostom. Reproductive system monorchic, germinal zone 22-µm long, sperm cells small with oval-shaped nucleus (2.5 × 1.5 µm). Spicules almost straight with slightly knob-like marked capitulum, blade with fine transverse striae, except at extremities, and slightly tapered towards a fine distal tip. Copulatory muscles hardly developed; capsule of suspensor muscles thin. Bursa narrow, extending from shortly anterior to retracted spicule to mid-tail. Three precloacal supplements, posterior two (SP1 and SP2) opposite distal half or spicules; SP3 about three body widths anterior to cloacal opening and non-protruding. Tail with pair of well-developed postcloacal supplements close to cloacal opening, the latter with a protruding anterior lip flap. A pair of posterior caudal pores subterminally, i.e. posterior to the posterior precloacal supplements. Tail tip cuticle 3.5 µm, hardly thickened.

Description of juveniles: One third-stage juvenile was observed. Largely similar to female, except for adult characteristics; reserve stylet 17 µm and genital primordium 32 µm long.

Code oithin the tabular identification key (based on: Decraemer and Baujard 1998): For females: A100 i.e. A111 (average, min, max), B21, C1, D1, E23, F34, G3, H5, I1, J1, K2, L33, M1, N2, O3, P2, Q4, R2, S1, T1. For male: A100, B2, C1, D0, E0, F3, G2, H2, I3, J1, K2, L2, M27, N2, O1, P1.

Diagnosis and relationships: Paratrichodorus asidonaensis sp. nov. is small (<550 µm on average, type population). It is characterized in female mainly by characteristics of the female reproductive system with a very short (less than one-fifth of corresponding body width), wide, rounded vagina, sclerotized vaginal pieces obliquely orientated, well-separated, small (1–1.5 µm), triangular in optical section, the vulva located at about 60% of body length from anterior end with longitudinal slit-like shape in ventral view and the unusual accumulation of sperm in the ovarial sac at the flexure of ovaries. Males are rare and are characterized by the absence of ventromedian and lateral cervical papillae, vas deferens with small oval sperm, the presence of three ventromedian precloacal supplements, of which the posterior two are located within the posterior half of the medium-sized (35 µm) retracted spicules; a narrow bursa extends from shortly anterior to retracted spicules, till mid-tail (length less than one anal body width).

Based upon the tabular identification keys for females (Decraemer and Baujard 1998), sorting on primary features D, C, followed by L and K, resulted in a classification of the new species in subgroup 1-12. Further sorting on feature P (type of sperm cell), followed by feature O (location of sperm), groups P. asidonaensis sp. nov. with P. allius . Both species possess sperm in ovarial sac, have a comparable onchiostyle length and males are rare. The new species can hardly be distinguished from P. allius with a similar onchiostyle length (37–43 µm vs. 37–48 µm) but a somewhat shorter body length compared with the type population of P. allius (480–565 µm vs. 640–780 µm). However, P. allius was considered a senior synonym of P. tansaniensis Siddiqi 1974 by Sturhan (1989) because the main differential features, i.e. the slightly shorter body and onchiostyle length in P. tansaniensis , cannot be used because of the considerable impact of fixation (see Discussion). Considering that features K and L may show some variation, we should also consider here P. rhodesiensis , although, in general, feature L (distance between sclerotized pieces is smaller) and specimens also possess sperm at the level of the ovarial sac ( Decraemer 1989). However, P. rhodesiensis shows more rounded sclerotized pieces.

For males, sorting of the data primarily on feature D (number of CP) and feature F (number of SP), places the new species in group 4 in Decraemer and Baujard (1998) together with P. rhodesiensis , P. teres , P. lobatus (2 SP), P. namibiensis (2 SP), and previously described new species P. tarifaensis sp. nov.. The new species most closely resembles P. rhodesiensis in the short body length [475 µm (N = 1) vs. 360–690 µm in type population of P. rhodesiensis ] and in onchiostyle length (42 µm vs. 39–43 µm) but differs in shorter spicule length (35 µm vs. 42–44 µm), presence of dorsal intestinal overlap vs. ventrosublateral overlap of pharyngeal glands. Paratrichodorus asidonaensis sp. nov. differs from P. teres in slightly shorter body length [480–565µm vs. 720–860 µm in populations from The Netherlands and Belgium; see: Decraemer and De Waele (1981); no males in P. teres type population] and spicule length (35 µm vs. 45–52 µm in P. flevensis population; P. flevensis syn. of P. teres ), in presence of dorsal intestinal overlap vs. ventrosublateral, or variable, marked manubrium and sperm structure (non-fibrillar appearance in testis). However, P. teres in the literature shows some variations indicating that we are probably dealing with a species complex (see general discussion). Paratrichodorus asidonaensis sp. nov. differs from P. lobatus and P. namibiensis apart from the common 3 SP vs. 2 SP and rarely 3 SP in P. lobatus and P. namibiensis , also in shorter body, shorter spicules, and different pharyngo-intestinal junction with anterior dorsal intestinal overlap vs. ventral pharyngeal overlap or a combined ventral and dorsal overlap respectively. In the sample from Benalup-Casas Viejas from the rhizosphere wild olive, P.asidonaensis sp. nov. was found together with female specimens from P. tarifaensis sp. nov., all possessing a rather short onchiostyle and similar low, oval shape of vagina, shape of vaginal sclerotized pieces in optical section and sperm in ovarial sac, but differing by males being rare in the former and by its small body size and spicules, but well separated by molecular markers (see below), confirming another case of cryptic diversity.

Figures

Figure 3. Line drawings for comparison of vagina in the Paratrichodorus allius species-complex group. A* B* P. uliaensis sp.nov.; C* D. P. benalupensis sp. nov.; E* P.hinogerus sp. nov.; F* G* P.tarifaensis sp. nov.; H* P.asidonaensis sp.nov.; I* P. rocianerus sp. nov.; J* P.litoralis sp. nov.; K* L* P. paraallius sp. nov.; M–P* P.allius based on Sturhan %1989); Q* P.allius* paratype; R* S* P.teres* paratypes.

Figure 10. Line drawings of Paratrichodorus asidonaensis sp. nov.. Females.A* total view holotype. B* pharyngeal region holotype.C* reproductive system holotype.D* ovarial sac with sperm* anterior branch paratype.E* tail region holotype. F* vagina region* paratype.Male paratype. G* pharyngeal region. H* posterior body region with reproductive system. Scale bars = 20 µm.

Figure 11. Light micrographs of Paratrichodorus asidonaensis sp. nov.. Male paratype.A* total view; B* testis germinal zone. Female holotype.D* pharyngeal region.E* reproductive system.F* vagina region. G* tail region. Scale bars A = 100 µm; B* C* F* G = 10 µm; D* E = 20 µm.