Phanodermopsis nana, Zograf, Julia K., Trebukhova, Yulia A. & Pavlyuk, Olga N., 2015

Zograf, Julia K., Trebukhova, Yulia A. & Pavlyuk, Olga N., 2015, Description of new species of Phanodermopsis (Enoplida, Phanodermatidae) with key to genera of family Phanodermatidae and pictorial key to Phanodermopsis species, Zootaxa 4032 (3), pp. 277-289 : 282-288

Description of Phanodermopsis nana sp. n.

( Figures 3–5 )

Measurements. Table 1 .

Material examined. Holotype male: deep-sea (the Sea of Japan), from 2697 m sampled with box-corer, found in silt-clay, 0–5 cm profile, collected by Trebukhova Yu.A. on August, 17th 2010. Slide is kept in Museum of A.V. Zhirmunsky Institute of Marine Biology, Vladivostok, Russia (N MIMB 30356)

Paratypes: 5 males and 5 females. N MIMB 30357, N MIMB 30358, N MIMB 30359, N MIMB 30360; same collection data.

Description. Body stout, narrowing to the anterior end. Cuticle 2–5 µm thick. Width of the body almost equal along trophico-genital portion. Head slightly set-off. Lips are fused. Six small inner labial papillae. Six outer labial and four cephalic setae into two separate circles. Somatic setae not found. Amphideal aperture as a trasverse slit, situated at the level of cephalic setae. Ocelli absent. Cephalic capsule weakly developed, ca 10 µm long. Pharyngeal capsule with small protrusions at the anterior end. Pharynx muscular, enlarged at the posterior end, with small cardia. Renette cell was not observed, secretory-excretory pore 58–70 µm from anterior end. Tail short, comprising anterior conical (62%) and posterior filiform (38%) parts. Five incaudal caudal glands, spinerette was not observed.

Male: Body length 2922–3082 µm. Outer labial sensillae 15–17 µm long, cephalic setae 13 µm long. Amphid 35.5% of corresponding body diameter. Distance from anterior end to amphid 9–11 µm. Secretory-excretory pore in front of nerve ring, distance from anterior end to pore 11.5% of pharynx length. Two opposing testes. Spicules paired, slightly bent, 1.5 anal diameters long. Capitulum cup-shaped. Gubernaculum small, wing-shaped, without apophysis. Supplementary organ absent.

Female: Similar to males. Two opposing reflexed ovaries. Two to four eggs in uteri. Vulva at mid-body length or slightly shifted posteriorly (V% = 51–59%). Tail shorter than in males.

Diagnosis and relationships. Phanodermopsis nana sp. n. is characterized by having a small body size compared to congeneric species, long anterior sensilla and short tail. It differs from other representatives of the genus by the De Man’s ratios ( Table 2), curved spicules and presence of a gubernaculum.

Of 10 described Phanodermopsis species, males are known only for P. ingrami Mawson, 1958 and P. caudatum Filipjev, 1927 . However, the description of P. caudatum is short and incomplete and comparison with P. nana sp. n. is not possible. The new species differs from P. ingrami in body length (~ 7000 µm in P. ingrami vs ~ 3000 µm in P. nana sp. n.). The De Man’s ratios are smaller in P. nana sp. n. (a= 35, b = 7.3, c = 28 in P. ingrami vs a = 19–23, b = 5.3–5.9, c = 19–21 in P. nana sp. n) and the outer labial setae are longer (1 corresponding body diameter) than in P. ingrami (1/2 corresponding body diameter). The vulva is more posterior in P. ingrami (V% = 58–61%) than in P. nana sp. n. (V% = 51–58%).

Etymology. The species name Latin “nano” means small, referring to the small size of the nematodes compared to other representatives of the genus.

Taxonomic remarks. The genus Phanodermopsis contains 11 species, only three of which (including P. nana sp. n.) have been adequately described. All other species were described from females or juveniles and should be considered as species inquirendae. Phanodermopsis necta Gerlach, 1957 was transferred to Phanoderma on the basis of the presence of a supplementary organ ( Lorenzen 1981). Phanodermopsis pigmentatum was transferred to Klugea Filipjev, 1927 on the basis of the presence of ventral and caudal glands ( Wieser 1953). From observation of the new species and P. ingrami , we have concluded that the main difference between Phanodermopsis and Crenopharynx is the length of spicules: long spicules (more than two anal body diameters in length) are characteristic of Crenopharynx species while short spicules (less or equal 2 anal body diameters) are characteristic of Phanodermopsis species. Given this, P. longisetae Chitwood, 1936 with extremely long spicules (5.2 anal body diameters) should be transferred to the genus Crenopharynx .

Phanodermopsis caudatum Filipjev, 1927 was re-described by Schuurmans Stekhoven (1946) and measurements of males were added. However, no description or illustrations of the males’ copulatory apparatus was provided, so it is not possible to discuss the position of this species among Phanodermatidae .

Because the representatives of the genus are mostly poorly described, the search for males of known species is essential. To facilitate future searches, we provide a pictorial key ( Fig. 6 ) to species of Phanodermopsis .

Species L a b c

P. nana sp.n. (males, females) 3000–3400 19–22.3 5.3–5.9 19– 21 P. attenuatum Wieser,1953 (females) 6500 23.3 3.6 16.5 P. caudata Filipjev, 1927 (females) 7000–7600 42–59 3.2–3.5 15.7 P. conicauda Filipjev, 1946 (females) 4900 - - -

P. cylindrocaudata Kreis,1928 (female) 3400 70.6 5.5 21.9 P. groenlandica, Ditlevsen. 1926 (female) 5180 43.2 5.2 47.1 P. ingrami, Mawson, 1958 (male, female) 7000–7300 35 7.3 28

P. longicauda ( Schuurmans Stekhoven,1950) juvenile 2800 59.5 3.1 14.3 P. obtusicauda, Filipjev, 1946 (females) 4000 38 4.5 57

P. reducta Filipjev, 1927 (females) 5270 62 2.8 35

P. suecica, Allgen, 1953 (juvenile) 2400 22.05 3.8 19.43

continued.

Species V% TL spic OLS amph D P. nana sp.n. (males, females) 53.7–58.9 151–159 126.7 11–15 5.1 P. attenuatum Wieser,1953 (females) 55.4 393 - 13 - P. caudata Filipjev, 1927 (females) 58 477 - - - P. conicauda Filipjev, 1946 (females) - - - 14–15 3.5 P. cylindrocaudata Kreis,1928 (female) 59.5 155.2 - - - P. groenlandica, Ditlevsen. 1926 (female) - - - - - P. ingrami, Mawson, 1958 (male, female) 57 261 75–80 - - P. longicauda ( Schuurmans Stekhoven,1950) juvenile - 153 - - - P. obtusicauda, Filipjev, 1946 (females) 61

P. reducta Filipjev, 1927 (females) 55

P. suecica, Allgen, 1953 (juvenile) -

Figures

FIGURE 3. Phanodermopsis nana sp. n. A. Holotype male. Total body. B. Allotype female. Total body. C. Holotype male. Anterior end with amphid. D. Holotype male. Tail with spicules and gubernaculum. E. Spicules with gubernaculum. Scale bars: A, B = 500 µm; C = 20 µm; D = 100 µm; E = 50 µm.

FIGURE 4. Phanodermopsis nana sp. n. A – C: DIC. D: LSM. A. Male head with amphid, lateral view. B. Male head with buccal cavity and cephalic capsule, lateral view. C. Male tail, lateral view. D. Spicules and gubernaculum. Scale bars: A, B = 20 µm; C, D = 50 µm.

FIGURE 5. Phanodermopsis nana sp. n. SEM. A. Head of the female. Lateral view. B. Head of the female. Apical view. C. Tail of the female. Lateral view. Scale bars: A, B = 2 µm; C = 20 µm.

FIGURE 6. Pictorial key to the identification of Phanodermopsis species. All drawings redrawn from original description. Not to scale.

Tables

TABLE 1. Morphometrics of Phanodermopsis nana sp. n. All measurements are given as a mean value ± standard deviation with ranges between brackets, in µm.

Male holotype	5 male	5 female
L 2922	3022±73.1 (2922–3082)	3183±244.3 (2931–3447)
a 22.2	22.9±3.1 (20.1–26.2)	19.3±4.2 (16.7–25.5)
b 4.8	5.3±0.1 (4.8–5.4)	5.9±0.3 (5.4–6.3)
c 17.2	19±1.3 (17.2–20.6)	21.1±1.3 (19.3–22.3)
c' 1.9	1.7±0.3 (1.5–2)	2±0.3 (1.7–2.4)
TL 170	159±10.3 (148–170)	152±15.7 (139–172)
M 132	134±20.8 (112–153)	169±26.5 (131–191)
HD 17	17±1 (16– 18)	15±2.8 (11.6–18.1)
a.b.d. 88	93±15 (79–109)	78±6.2 (72–86)
OLS 17	16±1 (15–17)	16±2.8 (15–19)
CSL 14	14	13±3 (11–15)
E-abe 58	66± 6.8 (58–71)	67±1.7 (65–69)
gub 24	29±1.5 (24–31)
NR 277	256±14.1 (243–277)	254±35.9 (210–290)
ph L 606	574±8.1 (566–606)	539±46.9 (469–568)
ph ebd 116	115±15.4 (100–130)	124±19.2 (99–145)
s’ 1.4	1.5±0.3 (1.2–1.7)
spic 127	142±15.9 (127–160)
Egg (length x width)		120 x 140
V		1707±114.3 (1550–1825)
V%		53.7±3.5 (51.2–58.9)
GL		942±135.6 (809–1066)
amph D 5	5±0.9 (5–5.2)	6±0.8 (5.4–6.6)
A-a.b.e. 11	10±1.2 (9–11)	10±1 (10–11)