Free-living marine nematodes of the family Sphaerolaimidae (Chromadoria, Monhysterida) from the mangroves of the Qeshm Island, Persian Gulf Author Tchesunov, Alexei V. Department of Invertebrate Zoology, Faculty of Biology, M. V. Lomonosov Moscow State University, 119991 Moscow, Russia. Author Eskandari, Ali 0000-0003-3902-7422 Department of Plant Protection, Faculty of Agriculture, University of ZanJan, 45371 - 38791, ZanJan, Iran. eskandari.a@znu.ac.ir Author Hosseinvand, Manouchehr 0000-0002-0472-1513 Department of Plant Protection, Faculty of Agriculture, University of ZanJan, 45371 - 38791, ZanJan, Iran. .houseinvand@gmail.com Author Hajializadeh, Parima 0000-0002-5997-7030 Department of Fisheries, Faculty of Marine Science and Technology, University of Hormozgan, Bandar Abbas, Iran. text Zootaxa 2024 2024-06-13 5468 3 523 540 http://dx.doi.org/10.11646/zootaxa.5468.3.6 journal article 298898 10.11646/zootaxa.5468.3.6 f5191cd6-725c-44d5-b66f-8676a68b155c 1175-5326 12189202 ECC85F24-D219-4664-899A-613FB64297DE Sphaerolaimus qeshmensis sp. n. ( Figures 1–2 , 7A–B and Table 1 ) Type material. Holotype male, one paratype male and two paratype females . Holotype male (slide 59/16) and paratype male (slide 50/17) specimens are deposited in the nematode collection of the Center of Parasitology , A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences , Moscow , Russia . Two paratype female specimens are kept in the nematode collection of Department of Invertebrate Zoology , Faculty of Biology , M. V . Lomonosov Moscow State University , Moscow , Russia . All the type specimens are mounted in permanent glycerin slides. Type locality and habitat. Intertidal silty sediment close to Avicennia marina tree, salinity of interstitial water: 33.8 ppt, temperature on the sediment surface: 29.7 °C, north coast of Qeshm Island, Strait of Hormuz, Hormozgan Province , southern Iran , November 2021 , ( 26°48’29.2”N , 55°45’05.5”E ) . Etymology. The species epithet is derived from the type locality, Qeshm Island . Descriptions. Males. Body short and stout, nearly cylindrical. Cuticle thick, with fine cross striations. No apparent lateral cuticular differentiation but borders of the lateral epidermal chords distinctly visible. Anterior end widely conical, and its cuticle not striated. Mouth opening surrounded with six small lips. A circle of six minute inner labial papillae located at the base of the labial region. Outer labial and four cephalic sensilla arranged in a joined circle of ten small setae at the level of the anterior edge of the cheilostoma ribs. Subcephalic setae arranged in eight groups (two dorso- and two ventro-sublateral, two dorso- and two ventrosubmedian) at the level of the anterior edge of the shagreen band. Each subcephalic group consists of three to four setae of various lengths. Somatic setae arranged in eight longitudinal rows; the setae rather long and dense in the preneural region, short and sparse posterior to the nerve ring along the body. Amphideal fovea as an irregular longitudinal oval shape situated at the posterior edge of the shagreen band. Mouth opening leads to the complicated buccal cavity. Major anterior part of the buccal cavity formed by modified somatic cuticle and thus qualified as cheilostoma. Anterior conical part of the cheilostoma further subdivided into two chambers, (1) anterior conical smooth-walled chamber surrounded by lips, and (2) posterior chamber shaped as a truncate cone with fine longitudinal striations (ribbing). There is a circle of tiny light-reflected granules at the anterior edge of the ribbing. The next voluminous barrel-shaped chamber with thick walls of light-refracted spongious material (shagreen band, see also family diagnosis above). Walls of the shagreen band with some light irregular longitudinal areas; posterior edge of the shagreen band projected outwardly into a circular crest. Amphideal area bulges by half into the shagreen band. Posterior wide conical part of the buccal cavity presents a pharyngostoma; it shaped by modified internal cuticle of the pharyngeal tissue. The anterior part of the pharyngostoma, the gymnostoma, is a narrow part just posterior to the shagreen band; gymnostoma walls look like a posteriorward continuation of the shagreen band. Stegostoma, the rearmost part of the buccal cavity, is surrounded with muscular pharyngeal tissue. Spongious rhabdions of the gymnostoma continue posteriorly and are soldered with the cuticle of the stegostoma. The cuticles of the gymnostoma and stegostoma are distinct from one another in the site of contact. Pharynx strongly muscular along its length, almost cylindrical, slightly broadened gradually to the cardia. Inner cuticular lining of the pharynx strong and wide and looks like several stripes because of the irregular width of the cuticle on a transverse section. Cardia hemispheric, with strong internal cuticular lining. Nerve ring at 46–47% of the pharynx length. Ventral gland ampulla and pore just posterior to the nerve ring. Ventral gland cell body not discernible. FIGURE 1. Sphaerolaimus qeshmensis sp. n. , entire view and heads. A: holotype male, entire; B: paratype female, entire; C: paratype female, head; D: holotype male, head. Scale bars: A, B—100 μm; C, D—10 μm. FIGURE 2. Sphaerolaimus qeshmensis sp. n. , holotype male, details. A: anterior body; B: posterior body. Scale bars: 100 μm. TABLE 1. Morphometrics of Sphaerolaimus qeshmensis sp. n. Measurements are in μm.? means that the setae are curved and pressed to body, not measurable.

Characters	Males		Females
Holotype	Paratype 1	Paratype 2	Paratype 3
Body length	1139	1610	1396	1410
Pharynx length	295	323	363	240
Tail length	164	222	195	199
Distance anterior and–vulva	-	-	1084	1048
a	14.4	13.8	12.9	13.1
b	3.9	5.0	3.9	4.2
c	7.0	7.3	7.2	7.1
c’	3.0	2.6	3.0	3.1
V%	-	-	74.3	77.7
Cylindrical portion of tail, %	35	31.4	32	32
Body diameter at level of cephalic setae	26	28	22	29
Body diameter at level of subcephalic setae	34	36	31	38
Body diameter at level of amphids	44	49	52	48
Body diameter at level of nerve ring	75	95	97	94
Body diameter at level of cardia	77	112	102	105
Body diameter at midbody	79	117	108	108
Body diameter at level of cloaca/anus	55	85	65	65
Anterior setae length	1.3	1.5	?	1.4
Subcephalic setae length	3–15	3–16	8–17	6–17
Amphideal fovea width	8	9	7	6
Distance amphideal fovea–cephalic apex	20	22	28	30
Stoma entire length (height)	49	50	51	53
Stoma width at shagreen band	18	19	31	35
Shagreen band width (longitudinal height)	18	20	19	20
Distance cephalic apex–ventral pore	153	186	184	189
Distance nerve ring–ventral pore	20	22	27	18
Spicules length (arc)	116	140	-	-
Spicules length (arc) divided by cloacal diameter	2.1	1.6	-	-
Dorso-caudal apophysis length	22	23	-	-
Caudal terminal setae length	21	22	24	27

Males reproductive organs poorly discernible. Anterior outstretched testis situated to the right of the intestine. Posterior testis not found. Fine-granular vas deferens situated to the right of the intestine. Spicules large, strong, thick-walled, arcuated, with both ends blunt. Gubernaculum consists of a basal trough and paired dorso-caudal apophyses. About eight tiny precloacal midventral supplementary papillae. Tail conico-cylindrical. Tail end thickened and provided with three long terminal setae, one dorsal and two ventro-lateral. A ventro-lateral row of about six setae on conical part of the tail. Females. Amphideal fovea of females notably smaller than that of males. Female reproductive system consists of a single prodelphic outstretched ovary situated to the right of the intestine. Diagnosis. Sphaerolaimus with body length 1139–1610 μm; a = 12.9–14.4, b = 3.9–5.0, c = 7.0–7.3, V% = 74.3–77.7%; subcephalic setae length 3–17 μm, amphideal fovea diameter (width) 6–9 μm situated at the posterior edge of the shagreen band; stoma length 49–53 μm, midstoma width 18–35 μm, height of the shagreen band 18–20 μm; spicules arcuated, 116–140 μm long, gubernaculum with dorso-caudal apophyses 22–23 μm long. Differential diagnosis. Basing on set of characters, the most similar species are: Sphaerolaimus kleini Jensen, 1992 ; S. limosus Fadeeva, 1983 ; S. makrolasius Schulz, 1932 ; and S. micropapillatus Tchesunov & Miljutin, 2006 . All those related species share position of the amphideal fovea at the level of the pharyngostoma, presence of a dorso-caudal apophysis of the gubernaculum and arcuated medium-sized spicules. S. qeshmensis sp. n. differs from S. kleini by significantly smaller amphideal fovea (males: width 8–9 μm versus 12 μm), longer spicules (116–140 μm versus 73–80 μm); from S. limosus by shorter subcephalic setae (males: 3–16 μm versus 7–22 μm), position of the amphideal fovea at the posterior edge of the shagreen band versus at the level of the gymnostoma or further posterior, and longer spicules (116–140 μm versus 85–100 μm); from S. makrolasius by smaller body length (males: 1139–1610 μm versus 2040 μm) and relatively longer spicules (ratio spicules length along the arc divided by cloacal body diameter 1.6–2.1 versus 1.1); from S. micropapillatus by larger amphideal fovea (males: 8–9 μm versus 6–7 μm), longer spicules (116–140 μm versus 63–64 μm) and less prominent, smaller, precloacal supplementary papillae.