Steinernema africanum n. sp. (Rhabditida, Steinernematidae), a New Entomopathogenic Nematode Species Isolated in the Republic of Rwanda

Characters	Male first generation		Male second generation	Female first generation	Female second generation	Infective juvenile
Specimen type	Holotype	Paratype	Paratype	Paratype	Paratype	Paratype
n	1	15	15	15	15	15
Body length (L)	1,300	1,202.2 ± 141.4 (977‒1,400)	955.4 ±92.8 (831‒1,213)	3,319.1 ± 763.2(2,469‒5,033)	1,620.0 ±487.6 (924‒2,311)	750.9 ± 39.8 (690‒802)
a (L/BD)	9.9	10.3 ±0.9 (9.1‒11.6)	17.0 ±1.6 (14.3‒19.0)	18.0 ±3.9 (13.2‒27.0)	13.5 ±1.0 (12.1‒15.7)	28.0 ± 2.4 (23.2‒30.4)
b (L/NL)	8.8	8.4 ± 0.8 (7.2‒9.6)	7.3 ± 0.6 (6.6‒8.5)	17.4 ±3.7 (12.8‒23.9)	10.1 ±2.1 (7.2‒12.9)	4.9 ± 0.5 (4.3‒6.3)
c (L/TL)	28.3	29.0 ± 3.3 (24.5‒33.9)	29.7 ± 2.9 (25.8‒35.7)	74.1 ± 17.6 (50.6‒103.9)	33.5 ±11.7 (16.5‒50.9)	11.9 ± 1.3(10.3‒14.9)
c' (TL/ABW)	0.9	1.0 ±0.1 (0.9‒1.1)	1.0 ±0.1 (0.7‒1.1)	0.9 ±0.1 (0.7‒1.0)	1.5 ±0.3(1.2‒2.3)	3.7 ± 0.4 (2.9‒4.2)
T(MR/L × 100),	94	87.3 ± 11.8 (65‒99)	71.6 ± 13.4 (58‒96)	52.0 ± 2.7 (50‒57)	56.0 ± 1.9 (53‒58)	‒
V (VA/L × 100)
Lip region diameter	21	19.5 ±3.2(13‒25)	15.1 ±1.6 (11‒17)	24.9 ±3.3(19‒31)	22.3 ±6.5 (14‒34)	6.1 ± 0.7 (5‒7)
Stoma length	9	7.5 ±2.1 (5‒11)	6.7 ± 1.2 (5‒9)	12.8 ± 2.9 (8‒19)	11.1 ± 2.4 (8‒16)	17.6 ± 4.4 (10‒23)
Corpus length	84	83.5 ± 5.2 (72‒90)	69.9 ± 3.3 (65‒76)	91.9 ± 8.1 (77‒108)	83.0 ± 14.0 (62‒101)	85.5 ± 8.1 (72‒97)
Isthmus length	26	20.8 ± 3.3 (14‒26)	22.4 ± 2.7 (18‒28)	27.6 ± 5.6 (21‒40)	23.8 ± 7.1 (11‒35)	27.6 ± 5.4 (19‒37)
Bulb length	28	29.2 ± 3.7 (25‒38)	26.9 ± 2.6 (22‒32)	45.1 ± 6.6 (37‒58)	33.3 ± 4.7 (24‒42)	22.8 ± 2.0 (18‒26)
Cardia length	11	8.7 ±1.5 (6‒11)	5.8 ±1.8 (4‒11)	11.5 ± 3.1 (8‒19)	7.7 ± 2.7 (4‒12)	‒
NR to anterior	95	91.5 ± 8.1 (79‒104)	83.5 ± 7.6 (74‒101)	105.4 ± 14.9 (79‒130)	96.4 ± 19.8 (69‒124)	117.7 ± 11.5 (87‒132)
EP to anterior	105	93.4 ± 12.4 (69‒109)	91.2 ± 6.7 (83‒104)	89.4 ± 14.3 (67‒111)	83.6 ± 11.6 (61‒104)	59.3 ± 4.2 (54‒68)
PL	138	134.7 ± 5.4 (123‒142)	123.5 ± 5.6 (117‒135)	169.6 ± 8.8 (158‒188)	140.9 ± 19.7 (113‒167)	137.2 ± 9.2 (113‒153)
NL(Stoma+PL)	147	142.5 ± 4.4 (132‒147)	131.1 ±5.6 (124‒143)	185.3 ± 7.9 (170‒201)	152.6 ± 21.6 (122‒181)	154.4 ± 12.0 (123‒167)
BD at neck base	73	65.7 ± 10.8 (41‒76)	44.7 ± 11.4 (37‒73)	124.4 ± 9.3 (113‒153)	77.5 ± 17.4 (47‒105)	26.1 ±1.6(21‒29)
BD at midbody	131	114.8 ± 17.9 (65‒131)	54.1 ± 5.2 (39‒59)	181.0 ± 14.8 (154‒208)	114.7 ± 37.3 (59‒167)	26.9 ± 1.6 (25‒32)
Anal BD (ABW)	50	41.9 ± 5.5 (33‒50)	34.8 ± 5.7 (30‒48)	52.4 ± 8.2 (37‒70)	33.9 ± 5.8 (26‒43)	17.2 ± 1.1 (16‒20)
Vagina length	‒	‒	‒	20.8 ± 6.3 (11‒33)	24.2 ± 11.9 (10‒49)	‒
VA end	‒	‒	‒	1,767.1 ± 445.4 (1,284‒2,411)	905.9 ± 266.0 (516‒1,217)	‒
Rectum length (RL)	‒	‒	‒	46.4 ± 8.8 (33‒63)	37.3 ± 14.3 (20‒64)	28.3 ± 3.9 (23‒38)
Tail length (TL)	46	41.1 ± 4.0 (34‒46)	33.9 ± 4.8 (28‒46)	44.6 ± 5.9 (35‒55)	49.7 ±5.7 (40‒60)	64.0 ± 7.1 (52‒72)
Tail hyaline length (H)	‒	‒	‒	7.4 ± 2.6 (4‒11)	12.2 ± 3.8 (6‒19)	22.5 ± 3.7 (17‒27)
SL	72	71.1 ± 3.6 (65‒76)	59.5 ± 4.8 (53‒68)	‒	‒	‒
GL	42	42.5 ± 4.2 (32‒49)	32.6 ± 5.7 (25‒46)	‒	‒	‒
Stoma length/lip region width	0.4	0.4 ± 0.1 (0.2‒0.7)	0.4 ± 0.1 (0.3‒0.5)	0.5 ± 0.1 (0.3‒0.6)	0.5 ± 0.1 (0.3‒0.7)	2.9 ± 0.6 (1.5‒3.7)
NR% (NR/NL × 100)	65	63.9 ± 4.9 (56‒71)	63.7 ± 3.5 (60‒71)	56.9 ± 7.9 (43‒65)	63.2 ± 8.5 (43‒69)	76.3 ± 5.8 (69‒90)
D % (EP/NL × 100)	71	65.1 ± 7.2 (52‒74)	69.6 ± 2.7 (67‒75)	48.3 ± 8.4 (36‒62)	55.5 ± 9.7 (49‒79)	38.1 ± 2.7 (34‒46)
E% (EP/TL × 100)	228	224.6 ± 22.7 (197‒261)	284.3 ± 34.5 (243‒345)	204.8 ± 44.9 (132‒281)	170.9 ± 33.4 (122‒221)	94.7 ± 17.4 (79‒129)
Rectum % (RL/ABD × 100)	‒	‒	‒	90.4 ± 19.7 (58‒112)	108.1 ±29.3 (74‒163)	164.3 ± 17.1 (128‒211)
H % (H/TL × 100)	‒	‒	‒	15.7 ± 5.1 (8‒20)	21.6 ± 11.7 (12‒40)	35.2 ± 3.4 (28‒39)
SW% (SL/ABD × 100)	144.0	172.3 ± 21.3 (144‒197)	177.2 ± 19.8(142‒217)	‒	‒	‒
GS % (GL/SL × 100)	58	59.9 ± 5.9 (49‒68)	54.7 ± 7.1 (46‒68)	‒	‒	‒
Male reproductive system (MR)	1,218	1,044.3 ± 240.9 (639‒1,371)	692.9 ± 172.4 (553‒1,166)
Testis reflexion	281	280.2 ± 66.3 (116‒352)	159.7 ± 64.6 (89‒273)	‒	‒	-
Mucron	5.1	4.8 ± 0.7 (4.0-5.3)	7.3 ± 2.5 (5-10)	4.4 ± 0.7 (3.7-5.0)	Absent	-

[i] All characters are in μm (except ratios and percentages) and given as mean ± s.d. (range).

BD, body diameter; EP, excretory pore; GL, gubernaculum length; IJs, infective juveniles; NL, neck length; NR, nerve ring; PL, pharynx length; SL, spicule length; VA, vulva-anterior end.

Line drawings of *Steinernema africanum* n. sp. IJ. **(A)** Stoma and pharynx region. **(B)** Anterior end. **(C)** Entire IJ. **(D)** Posterior end. IJ, infective juvenile.

Line drawings of first- and second-generation *Steinernema africanum* n. sp. females. **(A–E)** First-generation female: **(A)** Stoma and pharynx region; **(B)** Lip region and stoma; **(C)** Vagina region; **(D)** Posterior end; **(E)** Entire female. **(F–I)** Second-generation female: **(F)** Stoma and pharynx region; **(G)** Lip region and stoma; **(H)** Vagina region; **(I)** Posterior end.

Line drawings of first- and second-generation *Steinernema africanum* n. sp. males. **(A–D)** First-generation male: **(A)** Stoma and pharynx region; **(B)** Lip region and stoma; **(C)** Entire male; **(D)** Posterior end. **(E–H)** Second-generation male: **(E)** Stoma and pharynx region; **(F)** Lip region and stoma; **(G)** Entire male; **(H)** Posterior end.

Light microscope micrographs of first-generation adults and IJ of *Steinernema africanum* n. sp. **(A, B)** Stoma and pharynx region of female and male, respectively. **(C–E)** Lip region and stoma of female, male and IJ, respectively. **(F)** Vagina region. **(G–I)** Entire female, male and IJ, respectively. **(J)** Posterior end of a female. **(K, L)** Posterior end of males. Pictures are in right lateral view. IJ, infective juvenile.

Light microscope micrographs of second-generation adults and IJ of *Steinernema africanum* n. sp. **(A–C)** Stoma and pharynx region of female, male and IJ, respectively. Black arrow pointing the EP, white arrow pointing the bacteria sac. **(D)** Vagina region. **(E, F)** Entire female and male, respectively. **(G, H)** IJ bacterial sac and lateral field, respectively. **(I–K)** Posterior end of female, male, and IJ, respectively. Pictures are in right lateral view. EP, excretory pore; IJ, infective juvenile.

Scanning electron microscope micrographs of first-generation adults of *Steinernema africanum* n. sp. **(A, B)** Lip region of a female and a male, respectively, in lateral view. Arrows pointing the amphids (C: cheilostom, G: gymnostom, S: stegostom, cp: cephalic papillae, and lp: labial papillae). **(C)** Male posterior end in sub-ventral view – GP, MP, ph. **(D, E)** Lip region of a female and a male, respectively, in frontal view. **(F, G)** EP of a female and a male, respectively. **(H)** Vulva. **(I)** Male posterior end in sub-ventral view – GP, MP, ph. **(J)** Male posterior end in sub-ventral view – GP, MP. **(K)** Female anus. Arrow pointing a post-anal pore. **(L, M)** Female tail in lateral and ventral views, respectively. Black arrow pointing a post-anal pore, white arrows pointing the phasmids. EP, excretory pore; GP, genital papillae; MP, mid-ventral papilla; ph, phasmid.

Table 2

Comparative morphometrics of Steinernema africanum n. sp. IJs.

Species	Reference	L	BD	EP	NR	NL	TL	a	b	C	c'	D%	E%	H%
S. africanum	Present study	751	27	59	117	154	64	28	4.9	12	3.7	38	94	35
		(690‒802)	(25‒32)	(54‒68)	(87‒132)	(123‒167)	(52‒72)	(23‒30)	(4.3‒6.3)	(10‒15)	(2.9‒4.2)	(34‒46)	(79‒129)	(28‒39)
S. akhursti	Qiu et al. (2005)	812	33	59	90 (83‒95)	119	73	24	6.8	11	3.5	47	77	52
		(770‒835)	(33‒35)	(55‒60)		(115‒123)	(68‒75)	(23‒26)	(6.6‒7.2)	(10‒12)	(3.3‒3.7)	(45‒50)	(73‒86)	(49‒56)
S.	Ma et al. (2012)	843	30	62	87 (72‒97)	125	73	28	6.8	12	4.3	49	81	39
cholashanense		(727‒909)	(26‒35)	(59‒65)		(110‒138)	(60‒80)	(24‒34)	(6.1‒7.2)	(10‒14)	(3.5‒5.0)	(46‒53)	(76‒91)	(33‒47)
S. citrae	Stokwe et al. (2011)	754 (623‒849)	26 (23‒28)	56 (49‒64)	98 (83‒108)	125 (118‒137)	71 (63‒81)	30 (25‒34)	6.0 (5.1‒7.1)	15 (13‒17)	NA	44 (39‒58)	110 (85‒132)	43 (37‒50)
S. feltiae	Nguyen et al.	849	29	63	113	136	86	30	6.4	10	4.8	46	74	44
	(2007)	(766‒928)	(22‒32)	(58‒67)	(108‒117)	(130‒143)	(81‒89)	(27‒34)	(5.8‒6.8)	(9.4‒11)	(4.5‒5.1)	(44‒50)	(67‒81)	(37‒51)
S. hebeiense	Chen et al.	658	26	48	78 (73‒83)	107	66	26	6.2	10	NA	45	72	43
	(2006)	(610‒710)	(23‒28)	(43‒51)		(100‒111)	(63‒71)	(24‒28)	(5.7‒6.7)	(9.4‒11)		(40‒50)	(65‒80)	(32‒50)
S. ichnusae	Tarasco et al.	866	31	63	102	138	81	28	6.3	11 (9‒12)	4.6	46	77	48
	(2008)	(767‒969)	(27‒35)	(59‒68)	(94‒108)	(119‒148)	(76‒89)	(24‒32)	(5.6‒6.9)		(4.2‒5.1)	(42‒49)	(68‒83)	(44‒50)
S. jollieti	Spiridonov et al. (2004)	711	23	60	NA	123	68	31	5.7	10.5	4.5 (NA)	48	88 (NA)	55
		(625‒820)	(20‒28)	(53‒65)		(115‒135)	(60‒73)	(25‒34)	(4.9‒6.4)	(9‒12)		(46‒50)		(46‒60)
S. kraussei	Nguyen et al.	951	33	63	105	134	79	29 (NA)	7.1 (NA)	12.1 (NA)	3.9 (NA)	47 (NA)	80 (NA)	38
	(2007)	(797‒1,102)	(30‒36)	(50‒66)	(99‒111)	(119‒145)	(63‒86)							(35‒40)
S. kushidai	Mamiya (1998)	589	26	46	76 (70‒84)	111	50	23	5.3	11.7	NA	41	92 (NA)	NA
		(424‒662)	(22‒31)	(42‒50)		(106‒120)	(44‒59)	(19‒25)	(4.9‒5.9)	(10‒13)		(38‒44)
S. litorale	Yoshida, (2004)	909	31	61	96	125	83	30	7.3	11	4.5	49	73	33 (NA)
		(834‒988)	(28‒33)	(54‒69)	(89‒104)	(114‒133)	(72‒91)	(27‒31)	(6.7‒7.9)	(10‒11.9)	(3.8‒5.4)	(44‒56)	(68‒84)
S. nguyeni	Malan et al.	737	25	52	80 (74‒86)	110	67	29	6.7	11	4.3	48	79	27
	(2016)	(673‒796)	(22‒28)	(47‒58)		(101‒121)	(61‒73)	(27‒33)	(6.2‒7.4)	(10‒12)	(2.8‒4.8)	(43‒57)	(70‒86)	(20‒31)
S. oregonese	Liu and Berry, (1996)	980	34	66	NA	132	70	30	7.6 (6‒8)	14	4.7 (NA)	50	100	31
		(820‒1,110)	(28‒38)	(60‒72)		(116‒148)	(64‒78)	(24‒37)		(12‒16)		(40‒60)	(90‒110)	(30‒33)
S. populi	Tian et al. (2022)	1,095	36	77	106	149	64	30	7.4	17	2.8	52	121	35
		(973‒1,172)	(33‒41)	(70‒86)	(98‒113)	(134‒159)	(55‒72)	(24‒33)	(6.8‒8.5)	(15‒20)	(2.4‒3.3)	(47‒61)	(105‒140)	(26‒44)
S. puntauvense	Uribe-Lorfo	670	33	25	54 (46‒69)	94	54	20	6.1	12	NA	42	44	54
	et al. (2007)	(631‒728)	(31‒38)	(20‒30)		(81‒103)	(51‒59)	(17‒23)	(7.1‒7.9)	(11‒13)		(25‒50)	(35‒56)	(52‒55)
S. sandneri	Lis et al. (2021)	843	27	56	103	138	75	31	6.1	11.2	NA	40	74	34
		(708‒965)	(23‒32)	(44‒64)	(83‒118)	(123‒151)	(64‒86)	(27‒34)	(5.5‒6.9)	(11‒13)		(36‒45)	(63‒86)	(23‒40)
S. sangi	Phan et al. (2001)	753	35	52	91 (78‒97)	127	81	22	5.9	9.3	4.5 (NA)	40	62	49
		(704‒784)	(30‒40)	(46‒54)		(120‒138)	(76‒89)	(19‒25)	(5.6‒6.3)	(9‒10)		(36‒44)	(56‒70)	(44‒52)
S. silvaticum	Sturhan et al. (2005)	860	30	62	96	121	75	29	7.3	11.4	4.0	50	‒	46
		(670‒975)	(26‒35)	(51‒73)	(75‒109)	(100‒141)	(63‒86)	(23‒33)	(6.3‒7.7)	(10‒13)	(3.1‒4.9)	(46‒56)		(37‒53)
S. tielingense	Ma et al. (2012)	915	35	69	98	128	81	295	73	11	4	49	23	58
		(824‒979)	(32‒38)	(64‒73)	(90‒105)	(120‒135)	(74‒85)	(27‒31)	(67‒79)	(10‒12)	(3.5‒4.6)	(44‒56)	(68‒84)	(53‒64)
S. texanum	Nguyen et al. (2007)	756	30	59	92	115	73	25	6.5	10.4	3.3	51	81	59
		(732‒796)	(29‒34)	(52‒62)	(84‒102)	(111‒120)	(60‒79)	(22‒27)	(6.2‒7.0)	(10‒13)	(3.3‒4.6)	(46‒53)	(76‒88)	(53‒69)
S. xinbinense	Ma et al. (2012)	694	30	51	86 (75‒90)	116	73	24	6.1 (5‒7)	9.7	4.2 (3‒5)	44	71	35
		(635‒744)	(28‒31)	(46‒53)		(109‒125)	(65‒78)	(21‒25)		(8‒11)		(40‒47)	(65‒78)	(30‒42)
S. xueshanense	Mrácek et al.	860	30	67	91 (81‒96)	135	87	28	6.4	9.9	4.6	50	78	51
	(2009)	(768‒929)	(29‒33)	(60‒72)		(130‒143)	(80‒92)	(26‒32)	(5.8‒7.0)	(9‒11)	(3.8‒5.1)	(46‒52)	(70‒90)	(46‒55)
S. weiseri	Mrácek et al.	740	25	57	84 (72‒92)	113	60	29	6.6	12	3.7	51	95 (NA)	22
	(2003)	(586‒828)	(24‒29)	(43‒65)		(95‒119)	(49‒68)	(25‒33)	(5.7‒7.2)	(10‒14)	(3.2‒4.1)	(44‒55)		(18‒24)

[i] All measurements are in μm (except ratios and percentages).

BD, body diameter; EP, excretory pore; IJs, infective juveniles; NL, neck length; NR, nerve ring.

Table 3

Comparative morphometrics of first‒generation Steinernema africanum n. sp. males. All measurements are in micrometer (except ratios and percentages).

Species	L	BD	EP	NR	NL	TL	SL	GL	a	b	c	c'	D%	SW%	GS%
S. africanum	1,202	115	93	92	143	41	71	43	10	8	29	1.0	65	172	60
	(977‒1,400)	(65‒131)	(69‒109)	(79‒104)	(132‒147)	(34‒46)	(65‒76)	(32‒49)	(9‒12)	(7‒12)	(25‒34)	(0.9‒1.1)	(52‒74)	(144‒197)	(49‒68)
S. akhursti	1,589	131	102	136	182	35	90	64	NA	NA	NA	NA	56	180	71
	(1,350‒1,925)	(115‒150)	(93‒113)	(120‒163)	(168‒205)	(30‒40)	(85‒100)	(58‒68)					(52‒61)	(140‒200)	(65‒77)
S.	1,428	137	99	106	152	35	66	39	11	9.3	41	0.7	64	115	71
cholashanense	(1,070‒1,778)	(73‒204)	(75‒135)	(91‒126)	(135‒173)	(29‒43)	(60‒71)	(32‒45)	(9‒24)	(8‒11)	(36‒51)	(0.6‒0.9)	(50‒85)	(92‒144)	(61‒85)
S. citrae	1,154	103	81	106	139	25	65	44	NA	NA	NA	NA	58	198	68
	(1,028‒1,402)	(87‒113)	(64‒92)	(92‒119)	(123‒155)	(17‒31)	(57‒80)	(32‒59)					(47‒67)	(156‒233)	(48‒89)
S. feltiae	1,612 (1,414‒1,817)	75 (60‒90)	115 (110‒126)	69 (55‒87) a	170 (164‒180)	89 (37‒43)	70 (65‒77)	41 (34‒47)	11.5 (NA)	9.5 (NA)	41.3 (NA)	0.8 (NA)	60 (51‒64)	113 (99‒130)	59 (52‒61)
S. hebeiense	1,177	86	64	84 (78‒93)	126	30	57	46	14	9	39	0.8	51	140	80
	(1,036‒1,450)	(74‒98)	(58‒73)		(118‒132)	(24‒35)	(51‒63)	(38‒50)	(12‒17)	(8‒11)	(30‒49)	(0.6‒0.9)	(48‒59)	(120‒170)	(60‒90)
S. ichnusae	1,341	137	101	NA	165	40	66	44	22	8.2	34	0.8	62	139	67
	(1,151‒1,494)	(73‒204)	(94‒108)		(135‒173)	(33‒48)	(64‒67)	(43‒46)	(20‒29)	(7‒9)	(29‒39)	(0.8‒0.9)	(59‒65)	(120‒162)	(64‒69)
S. jollieti	1,662	115	98	NA	156	33	64	54	15	11	51	0.8 (NA)	64	145 (NA)	84 (NA)
	(1,296‒1,952)	(98‒135)	(83‒110)		(110‒168)	(24‒38)	(55‒70)	(45‒60)	(12‒19)	(8‒14)	(53‒86)		(53‒83)
S. kraussei	1,400	128	81	105	153	39	49	33	11	9 (NA)	37 (NA)	0.9 (NA)	53 (NA)	110 (NA)	67 (NA)
	(1,200‒1,600)	(110‒144)	(73‒99)	(95‒122)	(137‒178	(36‒44)	(42‒53)	(29‒37)
S. kushidai	1,400	97	84	129	167	33	63	44	NA	NA	NA	NA	51	150 (NA)	70 (NA)
	(1,200‒1,900)	(75‒156)	(71‒105)	(120‒137)	(156‒189)	(30‒40)	(48‒72)	(39‒60)					(42‒59)
S. litorale	1,360	96	96	114	147	34	75	53	14	9.3	41	0.8	40	174	71
	(1,230‒1,514)	(82‒111)	(77‒107)	(94‒128)	(133‒163)	(26‒41)	(67‒89)	(44‒64)	(12‒16)	(8‒10)	(33‒56)	(0.6‒0.9)	(34‒56)	(154‒200)	(62‒81)
S. nguyeni	997	82	59	91	124	21	66	43	12	8	46	0.7	48	215	66
	(818‒1,171)	(58‒106)	(47‒71)	(70‒103)	(112‒144)	(18‒25)	(58‒75)	(30‒55)	(11‒15)	(7‒10)	(38‒53)	(0.6‒0.8)	(38‒57)	(185‒279)	(46‒81)
S. oregonense	1,680	138	112	111	154	29	71	56	NA	NA	NA	0.6 (NA)	73	151 (NA)	79 (NA)
	(1,560‒1,820)	(105‒161)	(95‒139)	(101‒133)	(139‒182)	(24‒32)	(65‒73)	(52‒59)					(64‒75)
S.	1,591	119	94	115	140	33	77	34	NA	NA	NA	NA	67	170	65
puntauvense	(1,010‒1,931)	(101‒139)	(68‒114)	(104‒128)	(130‒159)	(28‒40)	(71‒81)	(30‒40)					(45‒85)	(140‒200)	(55‒75)
S. sandneri	1,461	155	80	126	157	41	60	44	10	9.3	37	NA	51	111	79
	(1,206‒1,635)	(124‒178)	(64‒92)	(112‒138)	(148‒170)	(35‒46)	(53‒65)	(39‒50)	(9‒11)	(8‒10)	(31‒42)		(42‒59)	(97‒127)	(61‒83)
S. sangi	1,774	159	82	126	166	32	63	40	NA	NA	NA	NA	49	150	60
	(1,440‒2,325)	(120‒225)	(67‒99)	(109‒166)	(150‒221)	(27‒42)	(58‒80)	(34‒46)					(42‒63)	(120‒160)	(50‒70)
S. silvaticum	1,090	65	79	119	142	34	51	37	17	7.7	34	1.0	60	155 (NA)	73 (NA)
	(975‒1,270)	(52‒78)	(71‒92)	(90‒126)	(116‒168)	(20‒47)	(42‒64)	(30‒43)	(14‒20)	(8‒9)	(24‒55)	(0.8‒1.4)	(45‒63)
S. tielingense	1,778	129	114	112	160	26	88	62	11	11	70	0.5	71	191	73
	(1,430‒2,064)	(111‒159)	(94‒133)	(96‒132)	(145‒173)	(22‒33)	(79‒98)	(49‒70)	(11‒18)	(9‒13)	(57‒85)	(0.3‒0.6)	(64‒78)	(176‒212)	(59‒82)
S. texanum	1,296	99	90	104	135	23	60	45	NA	NA	NA	NA	67	157	75
	(1,197‒1,406)	(81‒116)	(79‒100)	(94‒114)	(123‒147)	(19‒30)	(55‒66)	(39‒53)					(58‒73)	(127‒203)	(62‒84)
S. xinbinense	1,265	103	68	106	149	37	56	35	12	8.5	34	0.9	45	137	63
	(1,133‒1,440)	(90‒126)	(57‒75)	(91‒120)	(138‒159)	(30‒41)	(49‒62)	(30‒41)	(11‒13)	(7‒9)	(31‒39)	(0.7‒1.0)	(41‒50)	(114‒156)	(54‒72)
S.	1,589	144	128	NA	160	38	76	49	NA	NA	NA	NA	80	152	64
xueshanense	(1,313‒2,040)	(97‒159)	(113‒137)		(151‒175)	(29‒48)	(66‒91)	(41‒60)					(73‒87)	(93‒172)	(58‒95)
S. weiseri	1,180	112	70	99	141	25	68	53	11	8	48	0.7	49	180	80
	(990‒1,395)	(84‒138)	(57‒84)	(94‒115)	(134‒154)	(19‒32)	(62‒72)	(46‒57)	(9‒12)	(7‒10)	(36‒64)	(0.6‒0.9)	(39‒60)	(150‒240)	(70‒85)

[i] According to Aksary et al. (2020).

BD, body diameter; EP, excretory pore; GL, gubernaculum length; NR, nerve ring; NL, neck length; SL, spicule length.

Table 4

Comparative morphometrics of first‒generation Steinernema africanum n. sp. females. All measurements are in micrometer (except ratios and percentages).

Species	L	BD	EP	NR	NL	TL	a	b	c	c'	V	ABD	D%	Mucron
S. africanum	3,205	180	89	105	185	45	18	17	74	0.9	52	52	48	Present
	(2,469‒4,215)	(154‒194)	(67‒111)	(79‒130)	(170‒201)	(35‒55)	(13‒27)	(13‒24)	(51‒104)	(0.7‒1.0)	(50‒57)	(37‒70)	(36‒62)
S. akhursti	7,283	239	126	164	239	49	29b (NA)	31b (NA)	141b	0.6b(NA)	51	86	53 (NA)	Present
	(5,625‒9,000)	(200‒270)	(113‒138)	(150‒175)	(213‒258)	(38‒63)			(NA)		(48‒53)	(68‒100)
S.	4,692	255	129	190	196	57	13	25	83	0.8	53	77	50	Present
cholashanense	(3,232‒6,363)	(156‒332)	(111‒148)	(176‒223)	(181‒231)	(46‒70)	(13‒23)	(18‒32)	(62‒119)	(0.6‒1.0)	(50‒57)	(54‒105	(29‒65)
S. citrae	3,087	175	75	151	215	44	NA	NA	NA	NA	54	62	37	Present
	(2,038‒4,019)	(137‒212)	(54‒90)	(130‒179)	(189‒220)	(33‒60)					(50‒59)	(43‒79)	(27‒46)
S. feltiae	3,380	204	82	84 (70—97)a	237	52	17	14	65	1.0	56	52	46	Present
	(3,095‒3,774)	(170‒254)	(68‒97)a		(197‒304)	(39‒70)	(14‒20)	(12‒17)	(49‒88)	(0.7‒1.2)a	(44‒57)	(47‒62)	(40—54)a
S. hebeiense	3,465	167	65	104	147	35	21	24	103	0.7	54	53	45	Absent
	(3,972‒4,254)	(142‒245)	(48‒95)	(88‒123)	(133‒158)	(25‒50)	(17‒25)	(21‒29)	(67‒129)	(0.5‒0.9)	(50‒57)	(45‒65)	(36‒66)
S. ichnusae	5,514	269	126	NA	239	60	21	23	93	0.8	53	80	53	Present
	(4,547‒6,186)	(242‒323)	(106‒156)		(215‒262)	(51‒79)	(17‒24)	(21‒26)	(68‒113)	(0.6‒1.0)	(51‒57)	(70‒94)	(47‒63)
S. jollieti	5,148	259	111	NA	214	43	20	26	128	NA	51	NA	52	Present
	(3,746‒6,030)	(219‒298)	(96‒136)		(184‒310)	(31‒55)	(15‒24)	(19‒31)	(72‒185)		(44‒56)
S. kraussei	4,200	240	87	137	192	48	17	22	88	NA	54	45	45	Present
	(2,500‒5,400)	(153‒288)	(66‒99)	(127‒146)	(178‒205)	(33‒59)						(39‒50)
S. kushidai	3,500	175	91	124	227	38	NA	NA	NA	NA	56	64	40	Absent
	(2,100‒4,700)	(54‒59)	(78‒105)	(111‒144)	(204‒255)	(30‒45)					(54‒59)	(54‒84)	(37‒46)
S. litorale	4,462	191	88	146	196	39	23	23	117	0.6	56	62	45	Present
	(3,930‒5,048)	(175‒215)	(65‒105)	(130‒165)	(185‒213)	(25‒60)	(21‒26)	(20‒26)	(78‒157)	(0.5‒0.9)	(0.5‒0.9)	(55‒75)	(33‒57)
S. nguyeni	4,775	178	72	113	169	32	21	22	119	0.7	56	178	43	Absent
	(2,290‒5,361)	(130‒216)	(49‒98)	(84‒139)	(137‒194)	(20‒67)	(15‒30)	(15‒30)	(53‒165)	(0.6‒1.1)	(52‒63)	(130‒216)	(30‒56)
S. oregonense	5,200	242	103	147	210	37	NA	NA	NA	0.7 (NA)	52	56	49	Absent
	(4,400‒6,200)	(217‒268)	(217‒268)	(129‒162)	(186‒220)	(28‒46)					(46‒56)	(42‒79)	(43‒57)
S.	6,198	198	70	135	192	49	NA	NA	NA	NA	53	76	37	Present
puntauvense	(3,687‒8,335)	(181‒221)	(51‒85)	(123‒146)	(141‒206)	(41‒66)					(51‒55)	(57‒102)	(25‒45)
S. sandneri	4,628	210	84	147	185	147	22	25	102	NA	54	94	46	P‒esent
	(4,244‒5,014)	(181‒261)	(61‒102)	(132‒158)	(173‒194)	(32‒61)	(17‒25)	(24‒27)	(75‒140)		(49‒57)	(62‒122)	(36‒54)
S. sangi	6,030	336	101	158	229	49	NA	NA	NA	NA	51	111	44	P‒esent
	(4,830‒7,200)	(270‒360)	(80‒121)	(140‒170)	(216‒240)	(936‒62)					(43‒530)	(84‒140)	(35‒51)
S. silvaticum	2,150	116	69	113	146	45	19	15	49	1.3	52	35	47	Absent
	(1,520‒3,290)	(50‒175)	(50‒175)	(50‒175)	(121‒188)	(33‒79)	(15‒41)	(10‒18)	(34‒80)	(1.0‒1.8)	(44‒57)	(26‒53)	(33‒79)
S. texanum	3,058	163	88	122	172	40	NA	NA	NA	NA	52	60	NA	Absent
	(2,720‒3,623)	(130‒202)	(78‒107)	(111‒135)	(160‒189)	(30‒52)					(50‒55)	(50‒71)
S. tielingense	6,190	251	84	136	202	45	23	29	117	0.6	51	69	41	Absent
	(4,028‒8,538)	(200‒307)	(82‒103)	(111‒144)	(186‒263)	(40‒69)	(17‒32)	(21‒45)	(72‒158)	(0.5‒0.9)	(49‒54)	(56‒92)	(32‒49)
S. xinbinense	4,037	176	80	126	186	40	22	22	106	0.6	52	61	40	Present
	(3,025‒5,121)	(159‒200)	(70‒87)	(106‒141)	(167‒192)	(30‒53)	(19‒25)	(17‒26)	(79‒123)	(0.5‒0.8)	(46‒57)	(50‒67)	(38‒45)
S.	5,092	257	148	NA	230	55	NA	NA	NA	NA	54	84	NA	Present
xueshanense	(4,181‒8,181)	(182‒343)	(117‒148)		(196‒274)	(43‒66)					(52‒62)	(38‒72)
S. weiseri	4,610	223	80	125	184	42	21	25	111	0.7	53	63	NA	Present
	(3,780‒5,940)	(202‒263)	(75‒86)	(108‒154)	(162‒226)	(38‒59)	(17‒29)	(22‒31)	(87‒156)	(0.5‒0.8)	(50‒58)	(51‒80)

[i] ^aAccording to Aksary et al. (2020).

^bCalculated from Allotype

BD, body diameter; EP, excretory pore; NR, nerve ring; NL, neck length.

Scanning electron microscope micrographs of second-generation adults and IJ of *Steinernema africanum* n. sp. **(A–C)** Lip region of female, male, and IJ in lateral view, respectively. Arrows pointing the amphids (C: cheilostom, G: gymnostom, S: stegostom, cp: cephalic papillae, lp: labial papillae). **(D–F)** Lip region of female, male, and IJ in frontal view, respectively. Black arrows point to the amphids, white arrow points to the dorsal gland opening. **(G)** EP of female. **(H)** Male posterior region in lateral view – GP, MP, ph. **(I)** EP of IJ. **(J)** Vulva. **(K)** IJ lateral field. **(L, M)** Female tail (arrows pointing the phasmids). **(N)** Male posterior region in lateral view. **(O, P)** IJ tail in lateral and ventral views, respectively. Arrows pointing the phasmids. EP, excretory pore; GP, genital papillae; MP, mid-ventral papilla; ph, phasmid.

Phylogenetic relationships between the newly described *Steinernema africanum* n. sp. and other *Steinernema* species. Maximum-likelihood phylogenetic tree reconstructed from: **(A)** the nucleotide sequences of the ITS rRNA. A total of 705 nucleotide positions, flanked by primers 18S and 26S, were analyzed; **(B)** the nucleotide sequences of the D2–D3 expansion segments of the 28S rRNA. A total of 786 nucleotide positions, flanked by primers D2F and 536, were analyzed; **(C)** the nucleotide sequences of the COI gene. A total of 567 nucleotide positions, flanked by primers LCO-1490 and HCO-2198, were analyzed; and **(D)** the nucleotide sequences of the mitochondrial 12S rRNA gene. A total of 467 nucleotide positions, flanked by primers 505F and 506R, were analyzed. Numbers at nodes represent bootstrap values based on 100 replications. Bars represent average nucleotide substitutions per sequence position. NCBI accession numbers of the nucleotide sequences used for the analyses are shown next to the species names. COI, cytochrome oxidase subunit I; ITS, internal transcribed spacer; NCBI, National Center for Biotechnology Information.

Phylogenetic relationships between the *Xenorhabdus* symbiont isolated from *Steinernema africanum* n. sp. and other *Xenorhabdus* species. Phylogenetic trees were built based on core genome sequences. A total of 1,719,910 nucleotide positions were used in the analyses. Numbers at the nodes represent SH-like branch supports. Bar represents 0.05 nucleotide substitutions per sequence position. Accession numbers of the genome sequences used for the reconstruction are shown in Table S1 in Supplementary Material.

Table S1

National Center for Biotechnology Information (NCBI) accession numbers of the sequences used in this study.

Strain	Genome
Xenorhabdus sp. XENO-1	JAMGSK01
X. beddingii Q58^T	MUBK01
X. bovienii T228^T	JANAIF01
X. budapestensis DSM 16342^T	NIBS01
X. cabanillasii USTX62^T	QTUB01
X. doucetiae FRM16^T	FO704550
X. eapokensis DL20^T	MKGQ01
X. ehlersii DSM 16337^T	NIBT01
X. griffiniae BMMCB	LDNM01
X. hominickii KE01^T	NJAI01
X. indica DSM 17382T	NKHP01
X. innexi DSM 16336^T	NIBU01
X. ishibashii GDh7^T	NJAK01
X. japonica DSM 16522^T	FOVO01
X. khoisanae MCB	LFCV01
X. koppenhoeferi USNJ01^T	FPBJ01
X. kozodoii SaV^T	NJCX01
X. lircayensis VLS^T	JACOII01
X. mauleonii VC01^T	NITY01
X. miraniensis Q1^T	NITZ01
X. nematophila ATCC 19061^T	FN667742
X. poinarii G6^T	FO704551
X. stockiae TH01^T	NJAJ01
X. szentirmaii DSM 16338^T	NIBV01
X. thuongxuanensis 30TX1^T	MKGR01
X. vietnamensis VN01^T	MUBJ01

Pairwise comparisons of the ITS nucleotide sequences. **(A)** Sequence similarities (%). **(B)** Number of nucleotide differences (bp). A total of 808 nucleotide positions, flanked by primers 18S and 26S, were analyzed. NCBI accession numbers of the nucleotide sequences used for the analyses are shown next to the species names. ITS, internal transcribed spacer; NCBI, National Center for Biotechnology Information.

Pairwise comparisons of the nucleotide sequences of the D2–D3 expansion segments of the 28S rRNA. **(A)** Sequence similarities (%). **(B)** Number of nucleotide differences (bp). A total of 786 nucleotide positions, flanked by primers D2F and 536, were analyzed. NCBI accession numbers of the nucleotide sequences used for the analyses are shown next to the species names. NCBI, National Center for Biotechnology Information.

Pairwise comparison of dDDH scores (%) of *Xenorhabdus* strains. A total of 1,719,910 nucleotide positions were used in the analyses. Accession numbers of gene sequences used are shown in Table S1 in Supplementary Material. dDDH, digital DNA–DNA Hybridization.

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DOI: https://doi.org/10.2478/jofnem-2022-0049 | Journal eISSN: 2640-396X | Journal ISSN: 0022-300X

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Language: English

Submitted on: Jun 7, 2022

Published on: Oct 26, 2022

Published by: Society of Nematologists, Inc.

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© 2022 Ricardo A. R. Machado, Aashaq Hussain Bhat, Joaquín Abolafia, Ebrahim Shokoohi, Patrick Fallet, Ted C. J. Turlings, Eustachio Tarasco, Vladimír Půža, Joelle Kajuga, Xun Yan, Stefan Toepfer, published by Society of Nematologists, Inc.
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 54 (2022): Issue 1 (February 2022)

Steinernema africanum n. sp. (Rhabditida, Steinernematidae), a New Entomopathogenic Nematode Species Isolated in the Republic of Rwanda

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Table 1

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Table 2

Table 3

Table 4

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Figure 9

Table S1

Figure S1

Figure S2

Figure S3

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