A new genus with three new species of free-living marine nematodes of the subfamily Desmodorinae (Nematoda: Desmodoridae), from the continental shelf off northeastern Brazil
Author
Larrazábal-Filho, Alexandre L.
Author
Neres, Patrícia F.
Author
Silva, Maria Cristina Da
Author
Esteves, André M.
text
Zootaxa
2019
2019-06-13
4615
2
321
342
journal article
26506
10.11646/zootaxa.4615.2.5
f2ea6903-8250-4cef-b245-7d0358639a32
1175-5326
3244718
41436B41-169B-4228-AAEC-29C26BCFD77A
Spinonema cuticulatum
gen. et sp. n.
(
Table 1
,
Figures 3–5
)
Type material:
Holotype
,
Male adult
MNRJ 396
(
05°00’12.7’’S
036°23’27.7’’W
) collected in
June 2009
from the
Potiguar Basin
, between 30 and
45 m
deep.
Faciology
: fine to coarse bioclastic sand.
Gear
:
Van Veen
grab.
Paratype
female:
Adult,
MNRJ 397
(
05°01’36.1’’S
036°24’32.4’’W
) collected in
June 2009
from the
Potiguar Basin
, between 30 and
45 m
deep.
Faciology
: fine to coarse bioclastic sand.
Gear
:
Van Veen
grab
.
Other
paratypes
:
2 females
(198-199
LMZOO-UFPE
),
5 males
(200-204
LMZOO-UFPE
) and
5 juveniles
. Two in second stage of development (J2) and three in first stage of development (J1) (205
LMZOO-UFPE
) collected on same date as
holotype
. Juvenile stages were identified based on the developmental stage of the reproduc- tive system, based on
Bird and Bird (1991)
.
Etymology.
The species name refers to the ornate cuticle.
Description. Male
Holotype
(
Figures 3
and
4
).
Body cylindrical, yellowish brown. Cephalic capsule present. Cuticle coarsely annulated, with irregularly distributed vacuoles that start to appear from 9
th
(9-15
th
for
paratypes
) cuticular annule. The vacuoles are in the inner layer of the cuticle and not in its exterior. Annuli ornamented similarly to those in members of family
Epsilonematidae
. Annulations absent on tail end with vacuoles. Cuticle with lateral alae C-shaped, thicker than rest of body (
Figures 3
and
4
). Lateral alae begin
422 µm
(
378-467 µm
for
paratypes
) from head.Annules
3 µm
wide in anterior region,
2 µm
at midline and
3 µm
in posterior region. Somatic setae indistinct or barely visible in pharyngeal region. Few somatic setae and papillae irregularly distributed along body. Dorsal spine strongly cuticularized, located on 18
th
(for all specimens) cuticular annule (pharynx region), consisting of cuticular projection (
Figures 3C
and
4A
). Inversion of direction of annuli occus after 81
rd
(77-83
rd
for
paratypes
) cuticular annule. Head triangular. Cephalic capsule long and well-developed, with thick cuticle without annulations. Anterior sensilla arrangement: six inner and six outer labial sensilla, both papilliform. Four cephalic setiform sensilla positioned at midlevel of
fovea amphidialis
.
Fovea amphidialis
spiral (1.25 turns for all specimens), occupying 65% (46-70% for
paratypes
) of head diameter. Oral cavity with one small dorsal tooth and one small ventral tooth. Pharynx cylindrical, with muscular pyriform endbulb. Ventral gland and secretory-excretory pore not observed. Cardia inserted in intestine. Reproductive system monorchic, with single anterior testis situated to left of intestine, outstretched. Only one midventral precloacal setae present. Spicules short, arched, and capitulum hook-shaped (
Figure 3F
). Broad
velum
present. Gubernaculum simple, without apophysis. Three ejaculatory glands and three caudal glands. Tail short, conical, with vacuoles. Spinneret short.
Paratype
females (
Figures 4
and
5
).
Similar to male in body size, with minor differences: vacuoles present in cuticle appear on 15-18
th
annule. Inversion of direction of annuli occurring after 74-79
th
cuticular annule. Lateral alae begin
377-423 µm
from head. Reproductive system with paired ovaries, opposite and reflexed antidromously; both genital branches to right of intestine. Vulva as simple transverse slit-like aperture. Vagina vera slightly cuticularized. Vagina uterina surrounded by constrictor muscle. No egg found in uterus (
Figure 5D
). Vulva located at 39-40% of total body length from anterior end. Tail conical.
Juveniles (
Figure 5
).
Very similar to adults, except lacking lateral alae.
Fovea amphidialis
is very similar to the adults. Five juveniles were found, three in stage 1 and two in stage 2.
FIGURE 3.
Spinonema cuticulatum
gen. et sp. n.
Holotype MNRJ 396.
A
and
C
: anterior region;
B
: overview;
E
: lateral alae (ANT anterior part and POS posterior part);
D
and
F
: copulatory apparatus;
G
: tail region;
H
: Inversion of direction of annuli.
FIGURE 4.
Spinonema cuticulatum
gen. et sp. n.
A
,
B
and
E
Holotype MNRJ 396;
A
: Cephalic region;
B
: Spicules;
E
: Lateral alae (ANT anterior part and POS posterior part).
C
and
D
Paratype female MNRJ 397;
C
: Cephalic region;
D
: Tail region.
FIGURE 5.
Spinonema cuticulatum
gen. et sp. n.
Paratype female MNRJ 397.
A
: overview;
B
and
C
: anterior region;
D
: ovary and vulva opening;
G
: tail region.
E
and
F
: juvenile in stage 1, anterior region.
TABLE 1
. Measurements (µm) of
Spinonema cuticulatum
gen. et sp. n.
in the Potiguar Basin, Brazil. “-“ = not applicable. The mean and standard deviation are followed by the range for paratype measurements.
| Sex |
Male |
Male |
Females |
Juvenile |
| Holotype |
Paratypes |
Paratypess |
Paratypes |
| Number of specimens |
1 |
5 |
3 |
5 |
| Body length |
825.5 |
884±89(812.5–1066) |
774(747.5–806) |
612±73(530–720) |
| Pharynx length |
99 |
105±14(87–133.5) |
113(102–134.5) |
94±10(82–106) |
| Maximum body diameter |
28.5 |
38±30(23.5–34.5) |
36(30-39) |
26±4(21–30) |
| Anal body diameter |
24 |
22±2(19.5–24) |
25(24–25.5) |
19±2(17–21) |
| Tail length |
76.5 |
82±8(69–91.5) |
81(76.5–84) |
74±8(67–85) |
| Length of unstriated tail tip |
19.5 |
23±2(20–26) |
31(29-32) |
37±3(32–41) |
| Spine length |
13.5 |
14±2(13–18) |
14(13.5–15) |
12±2(9–15) |
| Head diameter |
22.5 |
20±5(13.5–30) |
18(16.5–19.5) |
13±2(10–15) |
| Cephalic capsule length |
22.5 |
21±3(15–22.5) |
19(16.5–19.5) |
10±2(8–12) |
| Spicule length along arc |
33 |
40±9(33–43.5) |
- |
- |
| Gubernaculum length |
15 |
17±2(13–19.5) |
- |
- |
| Velum length |
29 |
31±2(29–31.2) |
- |
- |
| Lateral alae length |
268.5 |
286±36(214–310.5) |
228(224–235.5) |
| Length of cephalic setae |
3 |
4±0(3–4) |
3(3–3.2) |
4±1(3–5) |
| Percentage of bulb diameter (cbd)* |
63 |
59±5(50–64) |
68(60–75) |
55±5(50–63) |
|
Diameter of
fovea amphidialis
in % of
|
65 |
60±11(46–70) |
44(41–46) |
53±8(41–62) |
| cephalic capsule width Distance from anterior end to the vulva |
- |
- |
557(552.5–559) |
- |
| V% |
- |
- |
40(39–40) |
- |
| Striation of the cuticle |
5 |
5±0(4.5–5) |
4.5(4.5) |
5±0(5) |
| Ring with the spine |
18 |
18±0(18) |
18(18) |
18±1(17–19) |
| Ring with the inversion of direction of |
81 |
80±2(77–83) |
76(74–79) |
- |
| annulation a |
29 |
33±2(29–35.5) |
22(19.5–25) |
24±3(20.5–27) |
| b |
8 |
8±0(8–10) |
6(5.5–8) |
7±0(6–7) |
| c |
11 |
11±1(10–12) |
9(9.5) |
4±1(3.5–5) |
*corresponding body diameter
Diagnosis.
Spinonema cuticulatum
gen. et sp. n.
is characterized by the annulated cuticle with vacuoles along the body, a spiral
fovea amphidialis
(1.25 turns), one dorsal spine in pharyngeal region, lateral alae, spicules arched with the capitulum hook-shaped,
velum
present, and three ejaculatory glands.
Relationships
.
Spinonema cuticulatum
gen. et sp. n.
is similar to
Desmodora
in the presence of a spiral
fovea amphidialis
(e.g.
Desmodora communis
(
Bütschli 1874
)
;
Desmodora coniseta
(Schuurmans Stekhoven, 1950)
;
Desmodora ignava
Gagarin & Klerman 2008
), arched spicules with a
velum
(
Desmodora granulata
Vincx
& Gour- bault 1989;
Desmodora marci
Verschelde, Gourbault & Vincx 1998
;
Desmodora masira
Warwick 1973
) and the buccal cavity with one dorsal and one ventral tooth (seldom present in
Desmodora
). It differs from
Desmodora
in the morphology of the cuticle:
S. cuticulatum
gen. et sp. n.
has an annulated cuticle with lateral alae and a pharyngeal dorsal spine. The new species is comparable to
Croconema
Cobb,
1920
in having the cephalic capsule offset and strongly annulated, and in some species in the presence of a
velum
(e.g.
Croconema otti
Gourbault & Vincx 1990
). It can be distinguished from
Croconema
by the absence of somatic and subcephalic setae. Another similar genus is
Desmodorella
in the spiral shape of the
fovea amphidialis
(e.g.
Desmodorella filispiculum
(
Lorenzen 1976
)
;
Desmodorella papillostoma
(
Murphy 1962
)
;
Desmodorella perforata
(
Wieser 1954
)
and the ornamentation on the cuticle, but differs mainly in the
type
of ornamentation. In
Desmodorella
the ornamentation consists of longitudinal rows of spines on the cuticle; whereas in
S. cuticulatum
gen. et sp. n.
the ornamentation consists of lateral alae in the form of a ridge. Thus, this species can be distinguished from any other species/genus by the combination of three characteristics: annulated cuticle with vacuoles, pharyngeal dorsal spine, and lateral alae.