Deontolaimus paraguillei, Holovachov, Oleksandr & Boström, Sven, 2015

Holovachov, Oleksandr & Boström, Sven, 2015, Swedish Plectida (Nematoda). Part 10. The genus Deontolaimus de Man, 1880, Zootaxa 4034 (1), pp. 1-44 : 19-25

Deontolaimus paraguillei sp. n.

( Fig. 9 ; Table 5 )

Type material examined. Holotype male (slide # Type-8776) deposited in the invertebrate type collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Type locality. Soft bottom 352–374 m deep, Skagerrak off the west coast of Sweden (N 58° 19' 15.6'' –20.9'', E 10° 29' 33.5'' –34.0''), 10 September 2012, legit "Inventering Bratten" (one male).

Additional material examined. Three males and two females (slides # 148131–148135) deposited in the general invertebrate collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Habitat and locality. Coarse sediment with algae from 45–55 m deep, Skagerrak off the west coast of Sweden (N 58° 17' 32'', E 11° 11' 24''), 0 9 August 2011, legit O. Holovachov (two females); soft bottom 221–260 m deep, Skagerrak off the west coast of Sweden (N 58° 28' 28.0'' –31.1'', E 10° 33' 19.1'' –23.8''), 11 September 2012, legit "Inventering Bratten" (one male); soft bottom 139–153 m deep, Skagerrak off the west coast of Sweden (N 58° 34' 21.3'' –16.6'', E 10° 38' 11.2'' –29.4''), 12 September 2012, legit "Inventering Bratten" (one female).

Description. Adult. Body slender, cylindrical over most of its length, tapering anteriorly in anterior half of pharyngeal region and posteriorly on tail; usually strongly ventrally curved upon fixation, especially so in posterior part. Cuticle annulated; annules without ornamentation. Lateral field present, single cuticular ridge weakly demarcated by two lines extending from intestinal region to posterior part of tail, in some specimens discernible only along posterior body end. Crystalloids absent. Body pores and epidermal glands absent. Somatic sensilla present, equally distributed along entire body; anterior-most somatic sensilla are located short distance posterior to amphid, at level with onchiostyle base. Labial region rounded, continuous with body contour; lips fused. Annulation along anterior-most part of body very weak; anterior-most annule appearing posterior to amphid and cephalic sensilla bases. One circle of labial sensilla visible on the anterior surface of labial region, they are small papilliform. Cephalic sensilla setiform, equal to 0.2–0.3 labial region diameter in length, their bases are located at level with middle or posterior edge of amphid. Subcephalic and cervical sensilla absent. Amphidial fovea ventrally-unispiral, making one turn, located at level with cephalic sensilla bases. Ocelli absent. Nerve ring surrounding pharynx at anterior two-fifth of its length. Hemizonid not seen. Secretory-excretory system present; renette cell located on left-hand side of body along anterior part of intestine; it extends anteriorly along ventral side of pharynx and forms excretory ampulla just posterior to nerve ring level. Excretory canal weakly cuticularised, extends from excretory ampulla for a short distance and opens to exterior on ventral side, at level with or just posterior to nerve ring. Oral opening terminal. Buccal cavity uniformly tubular: cheilostom barrel-shaped; stegostom tubular, with large dorsal onchiostyle. Onchiostyle with bluntly rounded tip and subcylindrical body. Pharynx muscular in its anterior part and glandular in its posterior part, cylindrical anteriorly, expanding posteriorly; not subdivided into sections; without bulbs; valvular apparatus absent. Dorsal pharyngeal gland orifice opens at base of onchiostyle; orifices of subventral pharyngeal glands indistinct. Cardia short, embedded in intestine. Tail similar in shape in both sexes (more curved ventrad in male) elongate-conoid, ventrally curved. Three caudal glands present, their nuclei are incaudal. Spinneret long conoid, slightly curved dorsad, functional.

Male. Reproductive system diorchic, both testes outstretched. Spicules paired, symmetrical, with arcuate subcylindrical shaft and small manubrium; manubrium is ventrally inclined. Gubernaculum present, plate-like, with paired dorsocaudal apophysis. Alveolar supplements present along entire body, very small, extending from anterior body end to about three body diameters in front of cloaca. Tubular supplements absent. Midventral precloacal sensilla absent. Two small postcloacal sensilla present, located subventrally at level of middle of tail length, discernible only by their nerve endings; sclerotized lamina absent. Tail with three pairs of papilliform sensilla: first (counting from cloaca) subventral pair located short distance posterior to cloacal opening, second subventral pair located at middle of tail length, and third sublateral pair located at posterior one-fourth of tail length.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 107–145 µm long (equal to 5.9–7.7% of total body length), located on right-hand side of intestine (n = 2), posterior genital branch 193–207 µm long (equal to 10.7–11% of total body length), located on left-hand side of intestine (n = 2). Oviduct short. Spermathecae filled with sperm. Uterus voluminous. Vagina straight, 0.3 times vulval body diameter long. Weak epiptygmata-like structure seen in one female but not in the other. Pars refringens vaginae and sensitive structures around vulva absent. Rectum 1.0–1.2 anal body diameters long.

Diagnosis. Deontolaimus paraguillei sp. n. is characterized by 1.4–1.8 mm long body; anterior-most somatic sensilla located at level with onchiostyle; cephalic sensilla equal to 0.2–0.3 labial region diameter in length; amphidial fovea ventrally-unispiral with one turn, located at level with cephalic sensilla bases; excretory pore located just posterior to nerve ring level; onchiostyle with bluntly rounded tip and subcylindrical body; male with alveolar supplements extending from anterior end to to about three body diameters in front of cloaca, tubular supplements absent; spicules 42–46 µm long; and didelphic female reproductive system.

Remarks. The current specimens are similar to Deontolaimus guillei (de Bovee, 1977) comb. n. in the morphology of the labial region (unispiral amphid, cephalic sensilla bases located at level with posterior edge of amphid) and relatively long acute spinneret. The two species can be separated by the following characters: body length (1.37–1.87 mm in D. paraguillei sp. n. vs 2.72–3.17 mm in D. guillei ) and other body measurements, cephalic setae length (2 µm in D. paraguillei sp. n. vs 6 µm in D. guillei ), tail length (c' = 4.3–5.4 in D. paraguillei sp. n. vs c' = 2.4–3.2 in D. guillei ), spicule length (42–46 µm in D. paraguillei sp. n. vs 63–65 µm in D. guillei ), and gubernaculum length (6–8.5 µm in D. paraguillei sp. n. vs. 12–13 µm in D. guillei ).

Deontolaimus paraguillei sp. n. is close to D. tardus in body size, length and position of cephalic setae, and shape of the amphid. These two species can be separated by the tail length (c'= 4.3–5.4 in D. paraguillei sp. n. vs c'= 2.5–3.1 in C. tardus ), length of spicules (42–46 µm in D. paraguillei sp. n. vs 58–59 µm in C. tardus ), and distribution of alveolar supplements in males (along most of the body length in D. paraguillei sp. n. vs along the pharyngeal region and anterior-most part of intestine in C. tardus ).

Type material. Holotype male (slide # Type-8777), and one male and three female paratypes (slide # Type-8778) deposited in the invertebrate type collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Type locality. Coarse sediment with algae from 45–55 m deep, Skagerrak off the west coast of Sweden (N 58° 17' 32'', E 11° 11' 24''), 0 9 August 2011, legit O. Holovachov (two males and three females).

Description. Adult. Body slender, cylindrical over most of its length, tapering anteriorly in anterior half of pharyngeal region and posteriorly on tail; usually strongly ventrally curved upon fixation, especially so in posterior part. Cuticle annulated; annules without ornamentation. Lateral field present, single cuticular ridge demarcated by two lines extending from anterior part of intestinal region to middle of tail. Crystalloids absent. Body pores and epidermal glands absent. Somatic sensilla present, equally distributed along entire body; anterior-most somatic sensilla are located short distance posterior to amphid, at level with onchiostyle shaft. Labial region rounded, continuous with body contour; lips fused. Annulation along anterior-most part of body very weak; anterior-most annule appearing posterior to amphid and cephalic sensilla bases. One circle of labial sensilla visible on the anterior surface of labial region, they are small papilliform. Cephalic sensilla setiform, equal to 0.2–0.3 labial region diameter in length, their bases are located at level with posterior edge of amphid. Subcephalic and cervical sensilla absent. Amphidial fovea ventrally-unispiral, making one turn, located just in front of cephalic sensilla bases. Ocelli absent. Nerve ring surrounding pharynx at anterior two-fifth of its length. Hemizonid not seen. Secretory-excretory system present; renette cell located on left-hand side of body along anterior part of intestine; it extends anteriorly along ventral side of pharynx and forms excretory ampulla just posterior to nerve ring level. Excretory canal weakly cuticularised, extends from excretory ampulla for a short distance and opens to exterior on ventral side, at level with or just posterior to nerve ring. Oral opening terminal. Buccal cavity uniformly tubular: cheilostom barrel-shaped; stegostom tubular, with large dorsal onchiostyle. Onchiostyle in females with triangular tip with bluntly rounded apex and strongly sclerotized dorsal edge, and subcylindrical body. Male onchiostyle less robust. Pharynx muscular in its anterior part and glandular in its posterior part, cylindrical anteriorly, expanding posteriorly; not subdivided into sections; without bulbs; valvular apparatus absent. Dorsal pharyngeal gland orifice opens at base of onchiostyle; orifices of subventral pharyngeal glands indistinct. Cardia short, embedded in intestine. Tail similar in shape in both sexes (longer and more curved ventrad in male), conoid, ventrally curved. Three caudal glands present, their nuclei are incaudal. Spinneret conoid, slightly curved dorsad, functional.

Male. Reproductive system diorchic, both testes outstretched. Spicules paired, symmetrical, with arcuate subcylindrical shaft and small manubrium; manubrium is ventrally inclined. Gubernaculum present, plate-like, without apophysis. Alveolar supplements present along anterior body half, extending from anterior body end to anterior part of intestine, they are small and located at the bottom of a narrow ventral groove. Tubular supplements absent. Midventral precloacal sensilla absent. Single (?) postcloacal sensillum present, located subventrally at level of posterior one-third of tail length; sclerotized lamina absent. Tail with four pairs of papilliform sensilla (clearly observed in one male only): first (counting from cloaca) subventral pair located short distance posterior to cloacal opening, second subventral pair located about one body diameter posterior to cloacal opening, third subventral pair located at posterior two-fifth of tail length, and fourth sublateral pair located close to tail terminus.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 72 µm long (equal to 10% of total body length), located on right-hand side of intestine (n = 3), posterior genital branch 45–79 µm long (equal to 5.9–11% of total body length), located on left-hand side of intestine (n = 3). Oviduct short. Spermathecae indistinct. Uterus voluminous. Vagina straight, 0.2–0.3 times vulval body diameter long. Epiptygmata, pars refringens vaginae and sensitive structures around vulva absent. Rectum 0.8–1.2 anal body diameters long.

Diagnosis. Deontolaimus timmi sp. n. is characterized by having body 0.7–0.9 mm long; anterior-most somatic sensilla located at level with onchiostyle; cephalic sensilla equal to 0.2–0.3 labial region diameter in length; amphidial fovea ventrally-unispiral with one turn, located just in front of cephalic sensilla bases; excretory pore located just posterior to nerve ring level; onchiostyle with triangular tip with bluntly rounded apex and strongly sclerotized dorsal edge, and subcylindrical body; male with alveolar supplements extending from anterior end to anterior part of intestine, tubular supplements absent; spicules 28 µm long; didelphic female reproductive system.

Remarks. Timm (1963) described Camacolaimus tardus (now placed in the genus Deontolaimus ) from the Arabian Sea, which was noticeably smaller than the specimens described by de Man (1889): 0.76–1.15 mm vs 2.1– 2.5 mm. Upon re-examination of type material of de Man and recently collected specimens of D. tardus several other differences were noticed: onchiostyle length (15–16 µm in Timm's specimens vs 20–23 µm in D. tardus ), spicule length (35 µm in Timm's specimens vs 58–59 µm in D. tardus ), and shape of spinneret (narrow in Timm's specimens vs. broad in D. tardus ), suggesting that the population from Arabian sea does not belong to D. tardus .

One of the populations found in Swedish coastal waters closely resembles Timm's description in body size and major measurements, shape of anterior body end, gubernaculum and spinneret, differing only in slightly shorter onchiostyle (7–11 µm in recent specimens vs 15–16 in specimens described by Timm), spicules (28 µm in recent specimens vs 35 in specimens described by Timm) and gubernaculum (6–8 µm in recent specimens vs 12 in specimens described by Timm). The new name, Deontolaimus timmi sp. n., is proposed to accommodate both populations and separate them from the other valid species of Deontolaimus .

Another population originally described under the name C. tardus (now placed in the genus Deontolaimus ) is from the North Sea ( Lorenzen 1969; Platt & Warwick 1988). It is similar to Deontolaimus timmi sp. n. in body size and general measurements, but can easily be separated from D. timmi sp. n. in having no lateral alae (vs present in D. timmi sp. n.), longer cephalic setae (equal to 0.6 vs 0.2–0.3 labial region diameter in length), shorter spicules (20–21 µm vs 28–35 µm in D. timmi sp. n.), gubernaculum with strong dorsocaudal apophysis (vs without apophysis). The systematic position of the population described by Lorenzen (1969) under the name C. tardus will be discussed below.

Deontolaimus timmi sp. n. is similar to D. papillatus in general body size and most measurements. These two species can be easily separated by the shape and size of alveolar supplements (small and hard to discern in D. timmi sp. n. vs distinct, obvious even under lower magnification in D. papillatus ).

Figures

FIGURE 9. Deontolaimus paraguillei sp. n. male (A – D) and female (E – H). A: Pharyngeal region, median section; B: Male posterior region; C & E: Anterior end, median section; D & F: Anterior end, surface view; G: Female tail; H: Female reproductive system. Scale bar: A – H = 20 µm.

Tables

TABLE 5. Morphometrics of Deontolaimus paraguillei sp. n. compared to D. guillei (de Bovee, 1977) comb. n. based on literature data and specimens from the Swedish coast (all measurements are in µm, except for the ratios a, b, c, c', V, T, NR, EP).

	D. guillei	Deontolaimus paraguillei sp. n.
	2 ♂♂ 1 ♀	Holotype ♂ 3 ♂♂ 2 ♀♀
Body length	2732; 2720 3170	1734 1376–1628 1872; 1810
a	66.6; 64.5 75.4	55.2 55.1–63.3 41.6; 36.2
b	8.8; 8.9 9.9	7.6 6.6–7.6 7.9; 8.1
c	22.4; 25.9 26.4	14.9 13.6–15.7 17.0; 16.4
c'	3.2; 2.4 3	4.4 4.3–5.0 5.4; 4.6
V(%) or T(%)	? 41.3	46.2 46.5–93.6 47.3; 48.4
Body diameter	41; 42 42	31.5 25–26.5 45; 50
Pharynx length	310; 305 320	230 209–228 237; 222
Tail length	122; 105 120	116 101–118 110; 110
Anal or cloacal body diam.	37; 43 41	26.5 21.5–23.5 20.5; 24
Labial region diameter	13; 14 15	10 8.5–9 9; 10
Cephalic setae length	6; 6 6	2 2 2
Setae bases from ant. end	??	5 3–4 3.5; 3
Amphid from ant. end	??	3 1.5–3 3; 1.5
Amphid width	4; 4 4	3.5 3.5 3.5; 3
Onchiostyle	32; 31 29	15 9–12 11; 11.5
Anterior-most body pore	??	15 13.5–14 11.5; 10
Nerve ring from ant. end	??	97 86–89 92; 94
NR (% of pharynx length)	??	42.1 40.6–42.4 38.8; 42.3
Excretory pore from ant. end	??	? 86–92 97; 94
EP (% of pharynx length)	??	? 40.6–44.0 40.7; 42.3
Vagina length	–?	– – 11.5; 13
Rectum length	–?	– – 24; 25
Spicule length	65; 63 –	43 42–46 –
Gubernaculum length	12; 13 –	6 6.5–8.5 –
Apophysis length	? –	4 3.5–4 –
Ant. alveolus from ant. end	? –	25 15–24 –
Post. alveolus from post. end	? –	65? –
Number of alveoli	??	pres. pres. 0
Deontolaimus timmi sp. n. (Fig. 10; Table 6)