First record of spiral fovea amphidialis in Acantholaimus (Chromadoridae: Nematoda), with a description of a new species from shallow sediments of the South Atlantic and an emended diagnosis of the genusAuthorManoel, AlexAuthorSilva, Maria Cristina DaAuthorEsteves, André M.textZootaxa201742583257270journal article3314410.11646/zootaxa.4258.3.304554432-c5a6-4c7f-8160-1dc299c106471175-5326569755AD166CBA-0191-4C8E-ABDC-31B60C6D5758Acantholaimus marliaesp. n.
(
Table 1
;
Figs 2–7
)
Material studied.
Type
specimens:
The
holotype
and one
paratype
(female) are deposited in the
National Museum
of
Rio de Janeiro
(
MNRJ
),
Brazil
.
The juvenile
paratypes
and
paratype
females are deposited in the
Meiofauna Laboratory
,
Zoology Department
, Universidade Federal de
Pernambuco
(LMZOO-UFPE),
Brazil
. Holotype male (MNRJ 350); allotype female (MNRJ 351); two paratype females (186–187 NM LMZOO-UFPE) and three juveniles (188–190 NM LMZOO-UFPE).
Type locality.
Material collected in
June 2009
, from the Potiguar Basin (03°00’00”S, 038°45’00”W). Sediment: fine to coarse bioclastic. Sampling: Van Veen grab.
Etymology.
The species name is given in tribute to Marli Maria da Silva, mother of the first author.
FIGURE 2.Acantholaimus marliaesp. n.
: (A) holotype male, overview; (B) anterior region (cuticular pores, cephalic arrangement and
fovea amphidialis
); (C) anterior region (buccal cavity); (D) anterior region (pharyngeal region and nerve ring); (E) spicules and gubernaculum.
FIGURE 3.Acantholaimus marliaesp. n.
: (A) holotype male,
anterior region; (B) cuticle (dots arranged in transverse
rows);
(C) cuticle (lateral differentiation); (D) anterior region (arrow
indicating position of
fovea amphidialis
); (E) anterior
region
(buccal cavity); (F) spicules; (G) gubernaculum.
Holotype
male
. Body cylindrical and attenuated at extremities, 684 µm long excluding tail (
Figs 2
A, 3A). Cuticle densely punctuated with dots arranged in transverse rows (
Figs 2
B, 3B). Lateral differentiation beginning at posterior border of
fovea amphidialis
, extending over pharynx until rear bulb portion, absent on rest of body. Lateral differentiation with larger dots, dispersed and more widely spaced than median ones, which are more densely arranged (Fig 3C). Cuticular pores oval and randomly scattered, extending along entire body length. Anterior sensilla difficult to see (first and second rings) and arranged according to following pattern 6+6+4: six inner labial papilliform sensilla, six outer labial papilliform sensill and four cephalic setiform sensilla (25 µm long), corresponding to 89% of head diameter (
Fig 2
B). Ventrally spiral
fovea amphidialis
(about 1.5 turns) located below cephalic setae and with transversely wider spiral shape, 7 µm in height and 13 µm wide, comprising 48% of corresponding body diameter and located 10 µm behind anterior end (
Figs 2
B, 3D). Two pairs of cervical setae 11- 15 µm, located posterior to each
fovea amphidialis
. Somatic setae (arranged in four sublateral longitudinal rows) present from posterior end of
fovea amphidialis
along entire body except for filiform part of tail. Buccal cavity relatively long. Cheilostom possesses 12 rugae. Five solid teeth, one large dorsal tooth measuring 6 µm and four small subventral teeth (
Figs 2
C, 3E). Most protuberant of subventral teeth (3 µm) shaped as "bottle opener". Remaining three teeth tiny and difficult to see. Pharyngostom about 9 µm long. Pharynx (130 µm long) muscular, cylindrical, expanded at level of pharyngostom, and forming well-developed basal bulb (39 µm diameter) at its proximal end, occupying 77% of corresponding body area (
Fig 2
D). Cardia embedded in intestine. Nerve ring situated at 41% of the pharyngeal region length (
Fig 2
D). Ventral gland and secretory-excretory pore not observed. Reproductive system with single anterior outstretched testis on right-hand side of intestine (155 µm), occupying about 25% of body length (excluding tail). Spicules curved, expanded and flattened in proximal portion (
Figs 2
E, 3F). Gubernaculum in form of tapered rod, its proximal portion slightly curved; bifurcated at its distal end (
Figs 2
E, 3G). Apophysis absent. Precloacal supplements absent. Three caudal glands. Tail conical-cylindrical with long filiform portion, with two rows of circular pores; distal portion of the tail is broken off.
Allotype
female
. Largely similar to male, except somatic setae that are generally absent (fewer somatic setae than in
holotype
, seen only in female
paratype
2, arranged similarly to those in male). Body measuring 804 µm in length to anal region, and maximum diameter 54 µm (
Figs 4
A, 5A). Cuticular pores over entire body, with similar size, shape and arrangement to those in male. Outer labial and cephalic sensilla equivalent to 20% and 74.5% respectively of corresponding body diameter (
Fig 4
B).
Fovea amphidialis
with same measurements as in male, and occupying 46% of corresponding body width (
Figs 4
B, 5B). Buccal cavity similar to that of male (
Figs 4
B, 5C). Pharyngostom about 9 µm long. Pharynx similar to that of male (
Fig 4
C). Nerve ring at 47% of the pharyngeal region length. Basal bulb occupying 75% of corresponding body area. Ventral gland and secretory-excretory pore not observed. Cardia embedded in intestine. One nematode (unidentifiable) observed in gut contents. Vulva located 516 µm from anterior end, at 64% of body length excluding tail (
Fig 5
D). Two opposite, reflexed and antidromous ovaries (anterior ovary lying to right of intestine, posterior ovary to left of intestine) (
Figs 5
E, 5F). Anterior and posterior ovary measuring respectively 220 and 320 µm. In reproductive ducts of
allotype
, a large spermatozoa (
24 x 21
µm) was found. This structure is most clearly visible in reproductive ducts of
paratype
1 (
Figs 4
D, 5G, 5H), where two spermatozoids were found, measuring about
30 x 20
µm (
Fig 4
E). Three caudal glands. Tail conicalcylindrical with long filiform portion, with two rows of circular pores; distal portion of the tail is broken off.
Paratype
juvenile.
The juveniles analyzed may be in the early stage of development, because the genital primordium is not visible. Juvenile sharing features of both adults. Body cylindrical and attenuated at extremities (618 µm long) (
Figs 6
A, 7A). Cuticle densely punctuated with dots arranged in transverse rows, but without lateral differentiation (
Fig 6
B). Cuticular pores not observed (except on filiform part of tail). First and second sensilla circles, as well as nerve ring and secretory-excretory pore not visible.
Fovea amphidialis
occupying 49% of corresponding body width (
Figs 6
C, 7B). Somatic setae arranged similarly to male, though fewer in number. Buccal cavity similar to that seen in adults (
Figs 6
C, 7C). Pharyngostom approximately 7 µm long. Pharynx similar to that in adults (93 µm), however, with narrowing at 39% of length. Basal bulb occupying 76% of corresponding body area. Tail conical-cylindrical with filiform end portion (
Figs 6
D, 7D), with two rows of circular pores. Spinneret short.
Diagnosis.Acantholaimus marliaesp. n.
is characterized by possessing numerous somatic setae arranged in four sublateral longitudinal rows, buccal cavity with five solid teeth (four subventral and one dorsal), the largest tooth dorsally located and the most protuberant tooth between the subventral shaped as a "bottle opener". It differs from all other species of the genus in having a spiral
fovea amphidialis
, wider than long, here considered as a differential characteristic and unique for the genus.
Differential diagnosis.
The new species shares with
Acantholaimus arthrochaetaMiljutina & Miljutin, 2012
the following features: the arrangement of the somatic setae along the body (4 sublateral longitudinal rows); dorsal tooth well developed and of similar length (5–6 µm in
A. arthrochaeta
and 6–7 µm in
A. marliaesp. n.
). The largest of the four subventral teeth is also similar in length (5 µm in
A. arthrochaeta
and 3–5 µm in
A. marliaesp. n.
). The length of the spicules (31–41 µm in
A. arthrochaeta
and 32 µm in
A. marliaesp. n.
) and anal body diameter (20–38 µm in
A. arthrochaeta
and 21–34.5 µm in
A. marliaesp. n.
) are also similar. However,
A. arthrochaeta
has distinct
FIGURE 4.Acantholaimus marliaesp. n.
: (A) allotype female, overview; (B) anterior region (buccal cavity, cuticle, cuticular pores, cephalic arrangement and
fovea amphidialis
); (C) anterior region (pharyngeal region and nerve ring); (D) paratype 1 female (ovaries and large spermatozoa); (E) Spermatozoa (found in paratype1).
FIGURE 5.Acantholaimus marliaesp. n.
: (A) allotype female, anterior region; (B) anterior region (arrow indicating position of
fovea amphidialis
); (C) anterior region (buccal cavity); (D) vulva region; (E) anterior branch; (F) posterior branch; (G) paratype 1 female, anterior branch (arrow indicating large spermatozoa); (F) paratype 1 female, posterior branch (arrow indicating large spermatozoa).
FIGURE 6.Acantholaimus marliaesp. n.
: (A) paratype juvenile, overview; (B) anterior region (pharyngeal region); (C) anterior region (cuticle, cephalic arrangement,
fovea amphidialis
and buccal cavity); (D) anterior region; (E) terminal portion of tail.
FIGURE 7.Acantholaimus marliaesp. n.
: (A) paratype juvenile, anterior region; (B) anterior region (cuticle; arrow indicating position of
fovea amphidialis
); (C) anterior region (buccal cavity); (D) filiform portion of tail.
characteristics such as a longer body without the tail (839–1055 µm
vs
582–804 µm in
A. marliaesp. n.
), and lateral differentiation extending along the entire body (except filiform part of tail); while in
A. marliaesp. n.
the lateral differentiation begins at the posterior border of the
fovea amphidialis
, extends over the pharynx until basal bulb level and is absent on the rest of the body. In
A. arthrochaeta
the pharynx forms a poorly developed bulb, whereas
A. marliaesp. n.
has a well-developed basal bulb; in the former, the anterior sensilla are jointed (inner labial sensilla bipartite, outer labial sensilla tripartite), whereas in
A. marliaesp. n.
these structures are not jointed; and in
A. arthrochaeta
the somatic setae are sometimes clavate, whereas the new species has only setae of edged form. Furthermore, the testis occupies about 40–50% of the pre-anal body length, whereas in
A. marliaesp. n.
it occupies about 25%. The spicules described for
A. arthrochaeta
are more curved, longer when measured along an arc (41–56 µm
vs
36 µm in
A. marliaesp. n.
).
Acantholaimus maksGerlach, Schrage & Riemann, 1979
shares with the new species features such as: the number of teeth in the buccal cavity (5), dorsal tooth well developed and of similar length (6 µm in
A. maks
and 6– 7 µm in
A. marliaesp. n.
), diameter of the
fovea amphidialis
(11–14 µm and 11–13 µm
A. marliaesp. n.
), as well as the percentage that this structure occupies in the corresponding area of the body (37–50% and 37–49% in
A. marliaesp. n.
); and anal body diameter (27–45 µm and 24–35 µm in
A. marliaesp. n.
). Yet,
A. maks
differs from
A. marliaesp. n.
in the following features: longer body without tail (
1180–1307
µm
vs
582–804 µm in
A. marliaesp. n.
); lateral differentiation absent; longer spicules along the chord (45–60 µm
vs
32 µm in
A. marliaesp. n.
); and the testis occupying 40% of the pre-anal body length, whereas the corresponding structure occupies about 25% in
A. marliaesp. n.
The species of
Acantholaimus
first described from shallow water,
A. polydentatusGerlach, 1951
shares with the new species: the length of the cephalic setae (20–22 µm in
A. polydentatus
and 21–25 µm in
A. marliaesp. n.
); maximum diameter of the body (22–48 µm and 24–54 µm in
A. marliaesp. n.
); index b’ (4–5 and
3–5 inA. marliaesp. n.
); ratio %v’ (70% and 63–73% in
A. marliaesp. n.
); and numerous somatic setae occurring over the entire the body except the filiform portion of the tail. However, these species differ in the shape and proportion occupied by the
fovea amphidialis
(50–70% in
A. polydentatus
vs
37–49% in
A. marliaesp. n.
) and the distance of this structure from the anterior end (5 µm in
A. polydentatus
vs
10–16 µm
A. marliaesp. n.
). Moreover, in
A. polydentatus
the spicules are smaller (24 µm along the chord in
A. polydentatus
vs
31.5 µm along the chord in
A. marliaesp. n.
) and the gubernaculum is absent.