Species Of Free-living Marine Nematodes Research Articles

Description of Amphimonhystrella sinica sp. nov. and Cobbia zhangi sp. nov. of the family Xyalidae (Nematoda: Monhysterida) from the Yellow Sea, China

Two new species of free-living marine nematodes belonging to the family Xyalidae are described from the Yellow Sea, China. Amphimonhystrella sinica sp. nov. is characterized by rhomboid-shaped buccal cavity, circular amphidial fovea relatively far from anterior end of body, slender L-shaped spicules with cephalated proximal end and hooked distal end, tubular gubernaculum with ventrally curved apophyses, slender tail conico-cylindrical with half cylindrical distal part. Cobbia zhangi sp. nov. is characterized by having three similar equal-sized teeth, anterior sensilla arrangement 6+10, slightly curved spicules cephalated proximally and tapered distally, gubernaculum rod-like without apophysis, tail with posterior three fourths filiform part. Updated dichotomous keys to species of Amphimonhystrella and Cobbia are given. Considering the descriptions in the present work, the two genera contain now 9 and 12 valid species, respectively; this study complemented the species diversity of nematodes in Chinese sea area.

Three new species of free-living marine nematodes of the Microlaimus genus (Nematoda: Microlaimidae) from the continental shelf off northeastern Brazil (Atlantic Ocean).

Three new species of the Microlaimus genus (Nematoda: Microlaimidae) are described from sample sediments collected in the South Atlantic, along the Continental Shelf break of Northeastern Brazil. Microlaimus paraundulatus sp. n. possesses four setiform cephalic sensillae, a buccal cavity with three small teeth, arched and slender spicules and a wave-shaped gubernaculum. Microlaimus modestus sp. n. is characterized by four small cephalic sensillae, a buccal cavity with three teeth (one large dorsal tooth), cephalated spicules and a strongly arched gubernaculum in the distal region. Microlaimus nordestinus sp. n. is characterized by the following set of features: relatively long body, eight rows of hypodermal glands that extend longitudinally along the body and a funnel-shaped gubernaculum surrounding the spicules at the distal end. An amendment of the diagnosis is proposed for the genus.

Two new species of Promonhystera Wieser, 1956 (Nematoda: Monhysterida: Xyalidae) from the South China Sea.

Two new species of free-living marine nematodes from the littoral sediment of the South China Sea are described as Promonhystera papilla sp. nov. and Promonhystera fluctispicula sp. nov. Both new species are characterized by striated cuticle; circular amphideal fovea; anterior sensilla in two circles, inner labial sensilla setiform; funnel-shaped buccal cavity; elongated spicules and conico-cylindrical tail. P. papilla sp. nov. is different from all known species of the genus by longer body length (more than 2.1mm versus less than 1.5 mm in other species), longer spicules (sp/a.b.d. = 4.14.6 versus 2.7) and males with three papilliform precloacal supplements and one small postcloacal papilla (versus absence) and gubernaculum boot-shaped. P. fluctispicula sp. nov. is similar to P. tricuspidata Wieser, 1956 in having similar waved spicules but differs from the latter species by tail conico-cylindrical (versus conical) and simple plate-like gubernaculum without tooth (versus gubernaculum with four distal teeth).

Two new records of free-living marine nematodes (Nematoda: Enoplida: Ironidae and Monhysterida: Xyalidae) from India

Two species of free-living marine nematodes were collected from the intertidal areas of East Coast of India namely, Conilia sinensis Chen and Guo, 2015 and Corononema parvum Nicholas and Stewart, 1995, both species are new records for the Indian fauna. Previously, the genus Conilia Gerlach, 1956 was known from Santos Beach, South Japan, East China Sea and Korea. The genus Corononema Nicholas and Stewart, 1995 was known only from Australia and Thailand and very recently reported from off the coast of Vietnam. Both the genera are being reported for the first time from India. The species are described and photomicrographed.

Two new species of Sabatieria de Rouville, 1903 (Nematoda: Araeolaimida: Comesomatidae) from the Southern Ocean.

Two new free-living marine nematode species of the genus Sabatieria de Rouville, 1903 are described from the Southern Ocean using morphological and molecular data. Sabatieria brevicaudata sp. nov. is characterized by body length 14761740 m, short cephalic setae, 1324% corresponding body diameter long, lateral differentiation of body cuticle with only slightly coarser punctations, spiral amphidial fovea with 3 turns, spicules arcuated and 1.31.6 cloacal body diameter long, slightly arcuated gubernacular apophyses, and twelve precloacal supplements, in the form of small pores. Sabatieria multipora sp. nov. is characterized by body length 21392324 m, short cephalic setae (47 m long, 3040% corresponding body diameter long), cuticle with lateral differentiation of distinctly coarser punctations extending from anterior edge of amphidial fovea to anterior of intestine and in the tail region, spiral amphidial fovea with 3 turns, males with spicules 1.92.0 cloacal body diameter long, seventeen fine tubular precloacal supplements with distance between adjacent supplements increasing towards anterior, and with curved gubernacular apophyses. We obtained 18S rDNA and 28S rDNA sequences from the two new species, which are both closely related to other species of Sabatieria. Our analyses also show that several genera of Comesomatidae Filipjev, 1918 do not form monophyletic clades.

Three New Species of Free-Living Marine Nematodes of the Order Enoplida Filipjev, 1929 (Nematoda) from the Yellow Sea, China

Three new nematode species belonging to the order Enoplida were discovered in the muddy and sandy sediment along the Shandong peninsula coast of the Yellow Sea during a biodiversity investigation of marine nematodes in the Yellow Sea. They are named Belbolla octobulba sp. nov., Ironella gracilis sp. nov. and Oxystomina longiseta sp. nov. Belbolla octobulba sp. nov. is characterized by having eight pharyngeal bulbs; spicules arcuate, broad and even; gubernaculum with a pair of dorso-caudal apophyses, about a third of the length of spicule; and two winged precloacal supplements. Ironella gracilis sp. nov. differs from known species by body slender, buccal cavity divided into conical vestibulum and cylindrical posterior portion, three sclerotized teeth located in the vestibulum; both circles of outer labial setae and cephalic setae 10 µm apart; elongated spicules weakly arcuate with central strip and cephalate proximal end; gubernaculum conical without apophysis; and a tubular precloacal supplement with a long seta at its anterior end. Oxystomina longiseta sp. nov. can be distinguished from other known species by the relatively long outer labial setae and cephalic setae; arcuate spicules expanded proximally with a median rib; gubernaculum small and oblong; and two unequal precloacal supplementary setae, anterior one short, posterior one very long. Updated keys to eighteen species of Belbolla and keys to four species of Ironella are given.

Three new free-living marine nematode species of the family Comesomatidae from Mangrove wetlands in Jinmen County, Taiwan.

Three new free-living marine nematodes, belonging to the genera Dorylaimopsis, Comesoma and Paracomesoma are described from the mangrove wetlands of western Taiwan Island. Dorylaimopsis jinmendaoica sp. nov. is characterized by having a cuticle with lateral differentiation of longitudinal rows of two rows of larger dots in the middle of the body, a spiral amphideal fovea with 2.52.75 turns, excretory pore anterior to nerve ring and 1721 fibriform precloacal supplements. Comesoma quattuordecimsupplementata sp. nov. is characterized by having a spiral amphideal fovea with 2.52.75 turns and 14 fibriform precloacal supplements. Paracomesoma paralissum sp. nov. is characterized by having a spiral amphideal fovea with 3.0 turns and 40 fibriform precloacal supplements. Differentiating characteristics of all known male Dorylaimopsis, Comesoma and Paracomesoma species are also given.

A new species of free-living marine nematode, Fotolaimus cavus sp. nov. (Nematoda, Oncholaimida, Oncholaimidae), isolated from a submarine anchialine cave in the Ryukyu Islands, southwestern Japan

Fotolaimus cavussp. nov. was described from a submarine anchialine cave called Akuma-no-yakata on the Shimoji Island, Miyako Island Group, Ryukyu Islands, southwestern Japan. This is the first free-living marine nematode isolated from a submarine cave in Japan, and the third species of the genus Fotolaimus. This new species differs from its congeners by its small body size, wide amphids, long buccal cavity, long conico-cylindrical tail, and proximally curved gubernaculum. We provide amended dichotomous keys to genera in the subfamily Oncholaiminae and species in Fotolaimus. We also analyzed partial DNA sequences encoding ribosomal small subunit RNA and cytochrome c oxidase subunit I from Fotolaimus cavussp. nov. and six other species of Oncholaimidae collected from Japanese waters. The phylogenetic tree based on the ribosomal small subunit RNA sequences using maximum likelihood analysis suggested a close relationship between Fotolaimus and Wiesoncholaimus as well as Oncholaimus. The topology of the tree was similar to those from previous studies; however, it suggested a new phylogenetic position of Adoncholaimus as a sister clade for Viscosia and Oncholaimus.

Three new free-living marine nematode species of Subsphaerolaimus Lorenzen, 1978, Halichoanolaimus de Man, 1886 and Belbolla Andrssy, 1973 from mangrove wetlands in Taiwan.

Three new species of free-living marine nematodes belonging to the genera Subsphaerolaimus, Halichoanolaimus and Belbolla are described from the mangrove wetlands of western Taiwan Island. Subsphaerolaimus danshuiensis sp. nov. is characterized by a body length of 13451693 m, subcephalic setae 22.565.0 m long, cervical setae 16.533.0 m long, an L-shaped spicule 66.976.4 m long, and a gubernaculum with a caudally-dorsally directed apophysis 16.423.0 m long. Halichoanolaimus sicaoensis sp. nov. is characterized by an amphidial fovea with 3.53.75 turns, a conico-cylindrical tail with the cylindrical portion approximately 3/4 of the total tail length, and 1314 not equidistant papillose precloacal supplements. Belbolla forkyspicula sp. nov. is characterized by seven oesophageal bulbs, a short tail, a spicule with a proximal fork, and two winged supplements. Differentiating characteristics of the genera Subsphaerolaimus, Halichoanolaimus and Belbolla are provided. Types are deposited in the College of Fisheries, Jimei University.

Machine learning algorithms accurately identify free-living marine nematode species.

Identifying species, particularly small metazoans, remains a daunting challenge and the phylum Nematoda is no exception. Typically, nematode species are differentiated based on morphometry and the presence or absence of certain characters. However, recent advances in artificial intelligence, particularly machine learning (ML) algorithms, offer promising solutions for automating species identification, mostly in taxonomically complex groups. By training ML models with extensive datasets of accurately identified specimens, the models can learn to recognize patterns in nematodes' morphological and morphometric features. This enables them to make precise identifications of newly encountered individuals. Implementing ML algorithms can improve the speed and accuracy of species identification and allow researchers to efficiently process vast amounts of data. Furthermore, it empowers non-taxonomists to make reliable identifications. The objective of this study is to evaluate the performance of ML algorithms in identifying species of free-living marine nematodes, focusing on two well-known genera: Acantholaimus Allgén, 1933 and Sabatieria Rouville, 1903. A total of 40 species of Acantholaimus and 60 species of Sabatieria were considered. The measurements and identifications were obtained from the original publications of species for both genera, this compilation included information regarding the presence or absence of specific characters, as well as morphometric data. To assess the performance of the species identification four ML algorithms were employed: Random Forest (RF), Stochastic Gradient Boosting (SGBoost), Support Vector Machine (SVM) with both linear and radial kernels, and K-nearest neighbor (KNN) algorithms. For both genera, the random forest (RF) algorithm demonstrated the highest accuracy in correctly classifying specimens into their respective species, achieving an accuracy rate of 93% for Acantholaimus and 100% for Sabatieria, only a single individual from Acantholaimus of the test data was misclassified. These results highlight the overall effectiveness of ML algorithms in species identification. Moreover, it demonstrates that the identification of marine nematodes can be automated, optimizing biodiversity and ecological studies, as well as turning species identification more accessible, efficient, and scalable. Ultimately it will contribute to our understanding and conservation of biodiversity.

Two new species of Chromadorida (Nematoda) from the intertidal zone of the Yellow Sea, China

ABSTRACT Two new species of free-living marine nematodes were discovered off the coast of the Yellow Sea, China, and they are described here as Actinonema diplobulba sp. nov. and Nannolaimoides brevicaudatus sp. nov. Actinonema diplobulba sp. nov. is characterised by amphideal fovea transverse oval-shaped, pharynx with double posterior bulbs, single spicule slender, arcuate with cephalated proximal end, gubernaculum spinous, and extra hammer-shaped lateral pieces (telamon) present. This species is distinguished from its congeners in having double pharyngeal bulbs and both spicule and telamon. Nannolaimoides brevicaudatus sp. nov. is characterised by a slender body with irregular lateral differentiation, multispiral amphideal fovea with five turns and close to anterior end, spicules arcuate with bent proximal end and tapered distal end, gubernaculum expanded distally and tapered proximally, a precloacal papilla and 14 button-shaped precloacal supplements almost equally arranged, and a conico-cylindrical tail 4.3–4.9 times as long as cloacal body diameter. This species differs from its congeners by having a precloacal papilla and 14 button-shaped precloacal supplements, and a comparatively short conico-cylindrical tail. http://www.zoobank.org/urn:lsid:zoobank.org:pub:D74795FE-168E-4F7F-A78C-08EF5B9783A9

Two new and one known free-living marine nematode species of the family Axonolaimidae from coastal wetlands in western Taiwan

Free-living marine nematodes, two new and one known, belonging to the genera Parodontophora and Axonolaimus are described from the coastal wetlands of western Taiwan Island. Parodontophora jinmendaoicasp. nov. is identified by having an amphid 3–4 times the length of the buccal cavity, with precloacal supplements present and a distinct pointed terminal end without terminal setae on the tail. Parodontophora microssp. nov. is characterized by having an amphid 1.0–1.5 times the length of the buccal cavity, with precloacal supplements present and a distinct pointed terminal end without terminal setae on the tail. In addition, we found Axonolaimus arcuatus (Schuurmans Stekhoven, 1950). This species is identical to that reported by Schuurmans Stekhoven, Gerlach and Boucher. This species is characterized by a double conical mouth, 4 head setae, a horseshoe-shaped amphid (dorsal and ventral amphid almost equal in length and parallel), an L-shaped spicule and an apophysis of gubernaculum. Comparison of characteristics of Axonolaimus arcuatus from different reports and differentiating characteristics of all known male Parodontophora species are given. Types are deposited in the College of Fisheries, Jimei University.

Two new species of genus Tripyloides (Nematoda, Enoplida, Tripyloididae) from the Chinese sea area

Abstract Two new free-living marine nematode species of genus Tripyloides were discovered in intertidal sediments along Rudong coast of the Yellow Sea and on Qi′ao Island of the South China Sea, respectively. They are described here as Tripyloides conicus sp. nov. and Tripyloides boucheri sp. nov. T. conicus sp. nov. is characterized by outer labial setae two-segments, amphideal fovea circular, buccal cavity with four chambers and with a distinct tooth at the bottom, spicules slender and straight, gubernaculum kidney-like with two lateral denticles at distal end, tail sexual dimorphism (elongated conical in males, conico-cylindrical in females). T. boucheri sp. nov. is characterized by body size small, outer labial setae stout, two-segments, amphidial fovea small, circular, narrow conical buccal cavity without distinct tooth, male with papilliform precloacal supplements, spicules slender, gubernaculum with two lateral denticles at distal end, tail conico-cylindrical and not swollen terminally. An updated dichotomous key for fifteen species of the genus is also given.

Three newly recorded free-living marine nematode species (Nematoda: Chromadorea) from Korea

Three newly recorded free-living marine nematode species (Nematoda: Chromadorea) from Korea

Two New Free-Living Marine Nematode Species of the Genus Haliplectus Cobb, 1913 (Haliplectidae) from Mangroves of Shenzhen, Guangdong Province, China

This study presents two new free-living marine nematodes, Haliplectus major sp. nov. and Haliplectus futianisus sp. nov., from a mangrove reservation in Shenzhen, China. Haliplectus major sp. nov. can be distinguished by its total body length of 1615–1998 µm; a cuticle annulated with eight rows of cuticle pores; amphidial fovea at 9–12 µm from the anterior end; a bipartite basal bulb with striated valve plates in both sexes; five to seven closely spaced precloacal supplements in males; a didelphic reproductive system in females, with the vulva at 49.64–52.37% of body length; and sexual dimorphism in tail shape, arcuate-conoid and 2.3–3.2 times anal body diameter long in males and elongate-conid and 3.5–4.2 times anal body diameter long in females. Haliplectus futianisus sp. nov. is characterized by a total body length of 574–655 µm; a cuticle annulated with eight rows of cuticle pores; amphidial fovea at 8–11 µm from the anterior end; a monopartite basal bulb with unstriated valve plates in both sexes; an absence of precloacal supplements in males; and a didelphic reproductive system in females, with the vulva at 42.33–45.63% of body length. The identification was confirmed by analyzing morphological characteristic and 18S rRNA gene sequences. The maximum likelihood (ML) topology was regarded as morphological evidence of H. major sp. nov. and H. futianisus sp. nov. being two distinct species.

Taxonomic revision of the free-living marine nematode genus Deontostoma (Enoplida: Leptosomatidae) and inclusion of a new species from the Southern Ocean

Summary A new species of free-living marine nematode, Deontostoma quadridentatum sp. nov., is described from a deep-sea sediment sample collected off the South Orkney Islands, the Southern Ocean, during a cruise (KH-19-6-Leg 4) conducted on the R/V Hakuho-Maru. Deontostoma quadridentatum sp. nov. differs from its congeners by the possession of: i) a cephalic capsule with a smooth posterior edge and without intralobar lacunae; ii) interlobar fenestrae with two posterior incisions; iii) four odontia on each mandible; iv) three onchia; v) spicules with velum and lateral process; vi) gubernacula with a hollow triangular crus, vii) one ventromedian supplement; viii) two precloacal subventral rows consisting of 8-10 setae and 12-20 papillae; and ix) by the lack of ocelli. Partial 18S rRNA and cytochrome c oxidase subunit I gene sequences were determined for D. quadridentatum sp. nov., and the diagnosis of Deontostoma and the dichotomous keys to the subfamilies of Leptosomatidae, genera of Deontostomatinae, and species of Deontostoma were revised. Two known species, Triceratonema montredonense comb. nov. and Triceratonema papillosum comb. nov., were transferred from Deontostoma. Our molecular phylogenetic analysis did not clarify the position of Deontostoma quadridentatum sp. nov., but we placed this species into Deontostoma based on morphological observations. We also tried to find a relationship between distribution and morphological characteristic because it seems that there are two phylogenetic lineages that exist in Deontostoma based on the distribution of all species. However, no such relationships could be found from our literature survey.

Two New Species of Free-Living Marine Nematode of the Genus Anticyathus Cobb, 1920 (Linhomoeidae) from Mangroves Sediment of Shenzhen and Shantou, China

Two new species belonging to the genus Anticyathus were discovered during an ecological investigation of mangrove sediment in China. Anticyathus shenzhensis sp. nov. and Anticyathus communis sp. nov. are both characterized by: annulated cuticles; ten cephalic setae in a circle; buccal cavity lined with six longitudinal reinforcements; amphids in broken circles or cryptic spirals, located at the very anterior of the head; pharynx with anterior cuticularized, gradually enlarging in posterior portion but without bulb; conical tail; arcuate spicules, the distal ends pointed, gradually broadening towards the proximal; gubernaculum has a dorsal–caudal apophysis; female with two opposed, outstretched ovaries. Anticyathus shenzhensis sp. nov. can be distinguished by ten cephalic setae of length about 2–4 µm; amphids diameter about 20–29% of corresponding body diameter; pharynx occupy 0.07–0.10 times of body length; cardia length about 25 µm; tail length 2.5–3.4 times of anal body diameter (abd) in males and 3.4–4.7 abd in females; spicules length 51–59 µm as arc and 0.71–1.04 abd; apophysis length 18–19 µm; female vulva at 52–56% of body length. Anticyathus communis sp. nov. is identified by ten cephalic setae length about 3–5 µm; amphids diameter about 20–32% of corresponding body diameter; cardia 17–27 µm long; tail length 3.6–4.5 abd in male, 5.3–5.5 abd in female; spicules proximal with distinctly cephalated, 0.74–0.96 abd; gubernaculum shape of “L”, consisting of sleeves around spicule and dorsal–caudal apophysis; five to seven pre-anal and seven to ten post-anal almost invisible papilla or papillae-like setae occur on each ventrally submedian line on the posterior body part of male; the tip of male tail with three slight elevation; female vulva at 52% of body length. A dichotomous key for the genus Anticyathus is given and 39 sequences of 18S rRNA gene from ten individuals of Anticyathus shenzhensis sp. nov. are provided in Genbank database.

Three new species of free-living marine nematodes from the central basin of the South China Sea

ABSTRACT Three new species of free-living nematodes were discovered in the central basin of the South China Sea and are described here as Elzalia longicaudata sp. nov., Minolaimus distalamphidus sp. nov. and Setoplectus minor sp. nov. Elzalia longicaudata sp. nov. is characterised by a longer tail and longer buccal cavity relative to other members of the genus; presence of a circle of four cervical setae; spicules slender and long, which curve as the body bends; and simple gubernaculum with only one section of dorsal apophysis. Minolaimus distalamphidus sp. nov. can be distinguished from congeners by the male having lateral differentiation with six longitudinal rows of large dots; multispiral amphideal fovea with 8.5 turns; pharynx cylindrical without bulb; spicules slightly arcuate; gubernaculum rod-like without apophysis; about 17 sucker-shaped precloacal supplements; and tail conical with long filiform posterior portion. Setoplectus minor sp. nov. differs from its congeners by small body size, anterior third of pharyngeal region attenuated; cephalic setae 2 µm long; amphidial aperture circular or oval; tail elongated conical; male with a single papilliform precloacal supplement. Updated identification keys for species of the three genera are also given. http://www.zoobank.org/urn:lsid:zoobank.org:pub:623BC44A-A07F-420E-AA41-271CF85F64C6

A New Species of Free-living Marine Nematode (Ptycholaimellus: Chromadoridae: Chromadorida: Nematoda) from Mangrove Wetlands in China.

This study presents a new species of free-living marine nematode, Ptycholaimellus luoyang sp. nov., from mangrove wetlands in China. The identification was confirmed by analyzing morphological characteristics and three genes: COI, 18S rDNA, and 28S rDNA. This species is distinguished from allied species by its short cephalic setae, cylindrical pharynx with anterior swelling, sclerotized transverse ridges occurring near the dorsal tooth, rod-like gubernaculum and proximal, arch-like, slightly waved, middle curved, and distally pointed spicules. The Bayesian topology was regarded as morphological evidence of P. luoyang sp. nov. being a distinct species. Interspecific and intrageneric thresholds of the K2P distance divergence have been presented here for the first time.

A new species of free-living marine nematode, Diplolaimella ariakensis n. sp. (Nematoda: Monhysteridae) from the Ariake Sea, Japan

Summary A new species of free-living marine nematode, Diplolaimella ariakensis n. sp., is described from a muddy tidal flat of the Ariake Sea, southern Japan. Diplolaimella ariakensis n. sp. differs from its congeners by the following: presence of ocelli, absence of denticles in the buccal cavity, a long tail (11-14 cloacal body diam., c = 3.2-4.0 in male, 17-21 anal body diam., c = 2.9-3.4 in female), spicules as long as 1.4-1.8 cloacal body diam., gubernaculum 0.4-0.5 cloacal body diam. long with a dorsocaudal apophysis 0.5-0.7 cloacal body diam. long, presence of a precloacal supplement, absence of postcloacal papillae, presence of seven pairs of body pores in male, and the anterior position of the vulva (V = 43-46). A dichotomous key to Diplolaimella species is provided. Almost full-length 18S rRNA and partial cytochrome c oxidase subunit I gene sequences were determined for D. ariakensis n. sp. A maximum likelihood tree of 18S sequences supported a close relationship between D. ariakensis n. sp. and D. dievengatensis.