Geocenamus paniculoides ( Vovlas & Esser, 1990 ) Brzeski, 1998

Ghaderi, Reza & Karegar, Akbar, 2016, One new and three known species of Geocenamus Thorne & Malek, 1968 (Nematoda: Merliniidae) from Iran, Zootaxa 4079 (2), pp. 151-178 : 155-158

Geocenamus paniculoides ( Vovlas & Esser, 1990) Brzeski, 1998

( Table 2 ; Figs 2 , 5 K– O, 6 F–J, 8 E)

A population of G. paniculoides was collected during the present study ( Table 2 ) with morphological and morphometric characters that fit well with the original description ( Vovlas & Esser, 1990).

Geocenamus paniculoides can be distinguished from the closely related species G. t a r t u e n s i s by a smaller number of annuli between the stylet knob base and the lip constriction (8–9 vs. 21), shorter stylet (19–21 vs. 24 µm), presence of males and higher c' value (2.2–2.8 vs. 1.9). It is pointed out ( Vovlas & Esser 1990) that the population studied by Brzeski (1968) is not conspecific with G. tartuensis . Subsequently, Brzeski (1991), after Present study

Character\Pοpulatiοn vοvlas & Esser 1990

(pοmegranate, Nοurabad-Shiraz rοad, Fars prοvince)

24♀ Cv 6♂ 30♀ 20♂ studying paratypes of both species plus several other populations, concluded that G. paniculoides should be considered as a junior synonym of G. t a r t u e n s i s. However, our results based on morphological characters (see below) and phylogenetic analysis ( Ghaderi et al. 2014) support the validity of G. paniculoides as a separate species. This taxon differs from G. tartuensis by its hemispherical and distinctly off-set head with a deep constriction (vs. conoid-truncate, usually narrower than the adjacent body and continuous or slightly off-set by a shallow groove); weakly developed cephalic framework (vs. more developed framework showing longer outer extensions); relatively shorter stylet (18.0–21.8 vs. 20.6–24.1 µm); and less distinct refractive inner cuticle layer at tail terminus (vs. more distinct and thicker).

The other species, G. siddiqii , shows some affinities with G. paniculoides in the shape of cephalic region, refractive basal ring of the cephalic framework and tail shape, but it can be distinguished from G. paniculoides by having wider cuticular annuli, bi-lobed spermatheca, annulated tail terminus, relatively longer body and larger spicules. However, few specimens with bi-lobed spermatheca and annulated tail terminus were also observed in the population of G. paniculoides from Iran.

Figures

FIGURE 2. Geocenamus paniculoides from Iran; A, C – E & G – K (female), B, F & L (male). A & B: Pharyngeal region; C – F: Anterior end; G: Part of reproductive system; H: Cross section at mid-body; I: Cuticle and lateral field; J – L: Tail.

FIGURE 5. Anterior end of Geocenamus species from Iran; A – D, F – I, K – N & P – S (female), E, J, O & T (male). A – E: G. conicaudatus n. sp.; F – J: G. rugosus; K – O: G. paniculoides; P – T: G. tartuensis. All scale-bars = 10 µm.

Tables

TABLE 2. Mοrphοmetric characters οf Geocenamus paniculoides frοm Iran and cοmparisοn with the οriginal descriptiοn (measurements are in μm).

L	820 ± 72.4 (680-942)	8.8 780 ± 33.0 (734-819)	853 (771-918)	860 (780-940)
a	30.4 ± 2.3 (27.7-38.8)	7.4 33.6 ± 1.5 (31.1-35.2)	30 (26-34)	32 (30-35)
b	5.5 ± 0.4 (4.7-6.1)	7.5 5.4 ± 0.3 (4.9-5.7)	5.2 (4.5-6.2)	5.5 (5.0-6.2)
c	17.6 ± 1.3 (15.4-20.1)	7.3 14.7 ± 0.6 (13.9-15.6)	18 (16-19)	15 (14-18)
c'	2.5 ± 0.2 (2.0-2.9)	8.8 3.4 ± 0.2 (3.1-3.7)	2.5 (2.2-2.8)	2.9 (2.7-3.2)
v	55.7 ± 1.5 (52.4-58.1)	2.7 -	53 (50-58)	-
Stylet	19.8 ± 0.9 (18.0-21.8)	4.5 19.1 ± 0.5 (18.7-19.8)	20.0 (19-21)	20 (19-21)
m	51.4 ± 1.9 (46.0-55.1)	3.6 50.6 ± 1.2 (48.9-51.9)	50-52	-
Pharynx	150 ± 11.7 (130-170)	7.8 144 ± 6.0 (138-154)	-	-
MB	47.5 ± 1.8 (43.6-50.6)	3.8 48.2 ± 1.0 (46.6-49.4)	-	-
S. E. pοre	120 ± 7.9 (100-135)	6.5 116 ± 6.5 (110-127)	127 (117-135)	125 (116-132)
Basal bulb length	32.1 ± 3.6 (26.0-38.7)	11.2 28.9 ± 2.0 (26.0-32.0)	-	-
Basal bulb width	13.5 ± 1.1 (11.2-16.3)	8.0 12.0 ± 0.5 (11.4-12.5)	-	-
Head-vulva	456 ± 35.2 (378-519)	7.7 -	-	-
Τail length	46.6 ± 4.5 (36.0-54.3)	9.6 53.1 ± 4.4 (47.2-59.0)	49 (39-58)	-
BW	27.0 ± 2.0 (23.5-30.0)	7.5 23.3 ± 1.3 (21.0-24.6)	-	-
Annuli width	2.1 ± 0.2 (1.8-2.5)	8.4 1.9 ± 0.1 (1.8-2.2)	-	-
Τail annuli	25.4 ± 2.8 (20-29)	11.1 -	21-32	-
Phasmid⁄tail %	34.8 ± 5.0 (22.4-42.9)	14.4 41.5 ± 5.7 (34.8-47.8)	-	-
Spicules	-	- 25.9 ± 1.5 (24.5-28.5)	-	26 (24-27)
Gubernaculum	-	- 9.3 ± 1.4 (7.0-11.0)	-	11 (10-12)