Acantholaimus marliae
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Ordo: Desmodorida
Familia: Comesomatidae
Genus: Acantholaimus
Name
Acantholaimus marliae Manoel, Alex, 2017 – Wikispecies link – Pensoft Profile
- Acantholaimus marliae Manoel, Alex, 2017, Zootaxa 4258: 259-266.
Materials Examined
Brazil National Museum Brazil Meiofauna Laboratory
Etymology
Etymology. The species name is given in tribute to Marli Maria da Silva, mother of the first author.
Materials Examined
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.
Description
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
Diagnosis.Acantholaimus marliae sp. 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 arthrochaeta Miljutina & 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. marliae sp. n.). The largest of the four subventral teeth is also similar in length (5 µm in A. arthrochaeta and 3–5 µm in A. marliae sp. n.). The length of the spicules (31–41 µm in A. arthrochaeta and 32 µm in A. marliae sp. n.) and anal body diameter (20–38 µm in A. arthrochaeta and 21–34.5 µm in A. marliae sp. n.) are also similar. However, A. arthrochaeta has distinct
characteristics such as a longer body without the tail (839–1055 µm vs 582–804 µm in A. marliae sp. n.), and lateral differentiation extending along the entire body (except filiform part of tail); while in A. marliae sp. 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. marliae sp. 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. marliae sp. 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. marliae sp. 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. marliae sp. n.).
Taxon Treatment
- Manoel, Alex; Silva, Maria Cristina Da; Esteves, André M.; 2017: 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 genus, Zootaxa 4258: 259-266. doi
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