Biodiversity Data Journal :
Taxonomic paper
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Corresponding author:
Academic editor: Vlada Peneva
Received: 26 Jul 2015 | Accepted: 31 Aug 2015 | Published: 03 Sep 2015
© 2015 Oleksandr Holovachov
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Holovachov O (2015) Description of Aegialoalaimus bratteni sp. n. from Skagerrak and a review of the genus (Aegialoalaimidae, Nematoda incertae sedis). Biodiversity Data Journal 3: e5738. https://doi.org/10.3897/BDJ.3.e5738
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The genus Aegialoalaimus de Man, 1907 includes 12 nominal species, of which three species are considered valid, two species were transferred to other genera and seven species have uncertain taxonomic status.
New species, Aegialoalaimus bratteni sp. n. was found in Skagerrak off the west coast of Sweden. It is particularly characterized by the 1.5-1.8 mm long body, short papilliform cephalic sensilla, excretory pore opening just posterior to nerve ring level, spicules that are straight in shape, supplements and gubernaculum absent, separating it from other valid species of the genus. It can be further differentiated from Aegialoalaimus elegans in having longer body (1.5-1.8 mm in A. bratteni sp. n. vs 0.8-1.3 mm in A. elegans), shape and size of spicules (straight and 22-29 µm long in A. bratteni sp. n. vs arcuate and 34 µm long in A. elegans), absence of precloacal supplements (vs seven-eight in A. elegans), absence of gubernaculum (vs present in A. elegans); from A. setosa in having shorter tail (c´=2.6-3.1 in A. bratteni sp. n. vs c´=4.2 in A. setosa), shorter cephalic sensilla (0.5-1.0 µm in A. bratteni sp. n. vs 9 µm in A. setosa), shape and size of spicules (straight and 22-29 µm long in A. bratteni sp. n. vs arcuate and 40-45 µm long in A. setosa), absence of precloacal supplements (vs eight in A. setosa), absence of gubernaculum (vs present in A. setosa); from A. leptosoma in having longer body (1.5-1.8 mm in A. bratteni sp. n. vs 0.5-0.7 mm in A. leptosoma) and other measurements, shape of spicules (straight in A. bratteni sp. n. vs arcuate in A. leptosoma), absence of precloacal supplements (vs three-five in A. leptosoma), absence of gubernaculum (vs present in A. leptosoma). Type specimens of Aegialoalaimus cylindricauda Allgén, 1933 and A. paratenuicaudatus Allgén, 1959 are redescribed and taxonomic status of these two species is re-evaluated. A taxonomic review, tabular compendium and identification key for species of the genus Aegialoalaimus are also given.
Aegialoalaimidae, Bratten, new species, revision, Skagerrak, Sweden, taxonomy
The genus Aegialoalaimus de Man, 1907 was originally described based on single species Aegialoalaimus elegans de Man, 1907 from the North Sea (
Bottom sediment samples were collected in several locations in the southern part of the Skagerrak designated as Bratten area. All samples were collected with the bottom dredge and further sieved in the lab before fixation. Nematodes were extracted from samples using a decanting and sieving method (smallest mesh sizes: 45 µm or 70 µm). Fresh water was used during sieving to induce osmotic shock in nematodes so they will detach from the substrate. Samples were immediately fixed in 4% formaldehyde. Formaldehyde-preserved specimens were transferred to pure glycerine using
Abbreviations used in the text are as follows: L = overall body length; a = body length / greatest body diameter; b = body length / pharyngeal region length; c = body length / tail length; c' = tail length / cloacal body diameter; T = length of main gonad (excluding flexures) / body length (expressed in %).
Type specimens of Aegialoalaimus cylindricauda Allgén, 1933 (SMNH Type-3559) and A. paratenuicaudatus Allgén, 1959 (SMNH Type-8762) from the invertebrate collection of the Swedish Museum of Natural History (SMNH) were used in this study. Despite considerable search efforts, type material of the following species cannot be located in the collection of C. Allgén: A. conicaudatus Allgén, 1959, A. punctatus (Allgén, 1929), A. sabulicola Allgén, 1933 and A. tenuicaudatus Allgén, 1932.
Measurements. Male holotype: L=1754 µm, a=38.1, b=9.6, c=15.4, c´=2.9, T=62.8%. Male paratype: L=1733 µm, a=35.4, b=9.2; c=13.8, c´=3.1, T=54.9%. Additional male: L=1492 µm, a=?, b=8.6, c=13.0, c´=2.6, T=53.8%.
Male. (Fig.
Pharyngeal region is 174-189 m long. Nerve ring surrounds the pharynx at 55.0-58.2% of its length. Hemizonid located at the level with the nerve ring. Secretory-excretory system present; renette cell located on ventral and ventrosublateral sides of the body along the posterior part of pharynx; it extends anteriorly and forms small excretory ampulla just posterior to the nerve ring level. Excretory canal absent, excretory ampulla opens to the exterior on ventral side of the body, at the level with the nerve ring, at 52.9-66.6% of the pharyngeal region length.
Oral opening terminal. Buccal cavity is weakly developed; cheilostom is a narrow tube 3-5 µm long; pharyngostom is indistinguishable from the sclerotized lumen of the pharynx. Pharynx divided into two sections: anterior tubular part and posterior (basal) bulb. Tubular part of the pharynx is 138-151 µm long and 3-4 µm wide; it is surrounded by thin sheath of tissue. Basal bulb is strongly muscularized; 30-33 µm long and 24-28 m wide. Nucleus of the dorsal pharyngeal gland is visible in the middle of the dorsal sector of the basal bulb. Subventral pharyngeal glands indistinct. Pharyngeal gland orifices indistinct. Cardia is 15-18 µm long, its posterior part is embedded in the intestine.
Reproductive system is diorchic, both anterior and posterior testes are outstretched anteriad. Spicules are 20-29 µm long, paired and symmetrical, straight in shape; with conoid shaft and small funnel-shaped manubrium. Gubernaculum absent. Supplements absent. Tail is 114-126 µm long, conoid to subcylindrical in shape, straight or weakly curved ventrad; with bluntly rounded terminus. Caudal glands present, they open to the exterior through common spinneret. Caudal gland nuclei are incaudal.
Female. Not found.
Aegialoalaimus bratteni sp. n. is particularly characterized by 1.5-1.8 mm long body, short papilliform cephalic sensilla, excretory pore opening just posterior to the nerve ring level, straight spicules, supplements and gubernaculum absent.
The new species can be differentiated from:
Aegialoalaimus elegans (as described by
A. setosa (as described by
A. leptosoma (as described by
Further characters separating all species of the genus are listed in Table
Diagnostic characters of valid species of the genus Aegialoalaimus de Man, 1907 and A. elegans sensu
Character |
A. elegans de Man, 1907 |
A. leptosoma Gagarin, 2012 |
A. setosa Bouwman, 1981 |
A. elegans sensu Bussau 1993 |
A. bratteni sp. n. |
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Body length (mm) |
0.8-1.3 |
0.5-0.7 |
1.4-1.8 |
0.4-0.6 |
1.5-1.8 |
Tail length (µm) |
81-102 |
54-68 |
≈130 |
45-75 |
114-126 |
c' |
3.0-5.0 |
3.1-4.0 |
5.0-6.0 |
4.2 |
2.6-3.1 |
Cephalic setae length (µm) |
1.0-6.0 |
1.5-2.0 |
≈9 |
2.0 |
0.5-1.0 |
Spicules length (µm) |
34 |
23-24 |
40-45 |
15 |
22-29 |
Supplements |
7-8 |
3-5 |
8 |
? | absent |
Excretory pore in male |
nerve ring level |
? |
nerve ring level |
nerve ring level |
nerve ring level |
Excretory pore in female |
cephalic setae bases |
? | ? | ? | NA |
Spicule shape |
arcuate |
arcuate |
arcuate with notch |
arcuate with notch |
straight |
Gubernaculum | present | present | present | present | absent |
The only type specimen is preserved but its internal structures are poorly visible.
The original description is based on single female specimen (
The only type specimen is poorly preserved, its anterior end is dried out.
The original description is based on single female specimen (
Dichotomous key to species of Aegialoalaimus de Man, 1907 |
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1 | Cephalic setae long, 9 µm or equal to 1/2 of the corresponding body diameter | A. setosa |
– | Cephalic setae short, 1-6 µm long, less than 1/3 of the corresponding body diameter2 | 2 |
2 | Spicules straight, gubernaculum and supplements absent | A. bratteni sp. n. |
– | Spicules arcuate, gubernaculum and supplements present | 3 |
3 | Male with 3-5 precloacal supplements | A. leptosoma |
– | Male with 7-8 precloacal supplements | A. elegans |
= Tubuligula Boucher & Helléuët, 1977 op. Jensen, 1978
Cuticle smooth or finely annulated. Lateral alae absent. Epidermal glands absent. Somatic sensilla present. Labial region rounded, continuous with body contour. Inner labial sensilla indistinct. Outer labial sensilla pore-like or papilliform, located on outer surface of lips. Cephalic sensilla papilliform or setiform, located at base of labial region, anterior to amphid. Amphidial aperture circular. Subcephalic and cervical sensilla, deirid and ocelli absent. Secretory-excretory system present; renette cell located opposite to ventral side of pharynx, cardia or anterior part of intestine. Excretory ampulla present. Excretory duct very short, opens to exterior at level with cephalic setae in females and at level of nerve ring in males. Stoma small, undifferentiated. Pharynx divided into anterior long tubular section with strongly sclerotized lumen and weakly developed tissue, and strongly muscularized oval basal bulb. Cardia cylindrical or conoid, partly enveloped by intestinal tissue in its posterior part. Female reproductive system didelphic, amphidelphic, ovary branches reflexed antidromously. Spermatheca present, axial. Vulva equatorial, transverse. Vagina thick; pars refringens vaginae absent. Male reproductive system diorchic, both testes outstretched. Spicules symmetrical, straight or arcuate; gubernaculum present or absent. Copulatory apparatus composed of a row of midventral precloacal sensilla (absent in one species). Postcloacal sensilla absent. Tail similar between sexes, conoid or subcylindrical with rounded terminus. Three caudal glands present, open via common spinneret.
Aegialoalaimus elegans de Man, 1907 (type by monotypy).
= Tubuligula roscoffensis Boucher & Helléuët, 1977 op. Jensen, 1978
nec Aegialoalaimus elegans sensu Bussau, 1993
Aegialoalaimus setosa Bouwman, 1981
Aegialoalaimus leptosoma Gagarin, 2012
Aegialoalaimus bratteni sp. n.
Aegialoalaimus conicaudatus Allgén, 1959
Aegialoalaimus cylindricauda Allgén, 1933
Aegialoalaimus paratenuicaudatus Allgén, 1959
Aegialoalaimus punctatus (Allgén, 1929)
= Kreisia punctata Allgén, 1929
Aegialoalaimus sabulicola Allgén, 1933
Aegialoalaimus tenuicaudatus Allgén, 1932
Aegialoalaimus tenuis Kreis, 1928
Aegialoalaimus amphibulbosus Gerlach, 1955 – Setoplectus amphibulbosus (Gerlach, 1955)
Aegialoalaimus brevicaudatus Kreiss, 1924 – Paraterschellingia brevicaudata (Kreiss, 1924)
Type material of this species could not be located in the collection of C. Allgén. Description and illustrations of this species do not provide sufficient information to be able to assign this species to any nematode genus or family (
Population of Aegialoalaimus elegans described by
Type material of this species could not be located in the collection of C. Allgén. Aegialoalaimus punctatus (Allgén, 1929) was originally described as Kreisia punctata Allgén, 1929. Description and illustrations of this species do not provide sufficient information to be able to assign this species to any nematode genus or family (
Type material of this species could not be located in the collection of C. Allgén. Description and illustrations of this species do not provide sufficient information to be able to assign this species to any nematode genus or family (
Type material of this species could not be located in the collection of C. Allgén. Description and illustrations of this species do not provide sufficient information to be able to assign this species to any nematode genus or family (
Aegialoalaimus tenuis Kreis, 1928 most probably should be placed in the family Microlaimidae based on the following characters: pharynx cylindrical in its anterior part, with basal bulb, muscularized along its entire length; reproductive system didelphic, gonads outstretched (
This research was supported by a grant from the Swedish Taxonomy Initiative. Sampling in the Skagerrak was conducted using the vessel “Skagerak” and facilities of the Sven Lovén Centre for Marine Sciences in Kristineberg. "Inventering Bratten" was an interdisciplinary inventory project also financially supported by the Swedish Taxonomy Initiative.
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