Labial Sensilla Research Articles

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).

ДВА НОВЫХ ДЛЯ НАУКИ ВИДА ОНХОЛАЙМИД (NEMATODA, ENOPLIDA, ONCHOLAIMIDAE) С КОРАЛЛОВЫХ РИФОВ ВО ВЬЕТНАМЕ

Two new for science species of the family Oncholaimidae Dujardin, 1845, found in coral reefs in Vietnam, are described and illustrated. Oncholaimus securus sp. n. is close to O. longispiculosus Gerlach, 1955 according to presence of papilla on tail and spicules length. It differs from it by the longer and thinner body, shorter pharynx and wider labial region. Viscosia graciloides sp. n. in body size and length of spicules is close to V. erasmi Furstenberg, Vincx, 1989, V. macrobursata Keppner, 1987 and V. dossena Leduc, Zhan, 2023. It differs from these species by the form of outer labial sensillae, thinner body, narrower labial region and shorter stoma.

Two New Nematode Species, Desmolaimus magnus sp. nov. (Monhysterida, Linhomoeidae) and Metadesmolaimus robustus sp. nov. (Monhysterida, Xyalidae), from the Yellow Sea, China with Phylogenetic Analyses within Linhomoeidae and Xyalidae

Two new species are described from the Rizhao coast along the Yellow Sea. Desmolaimus magnus sp. nov. is characterized by its relatively large body size, faintly striated cuticle, four long cephalic setae, a wide buccal cavity with cuticularized transverse rings, an amphidial fovea at the junction of the buccal cavity and pharynx, a pharynx without a bulb, curved spicules, a gubernaculum with a dorso–caudal apophysis, and an elongated conical tail. Metadesmolaimus robustus sp. nov. is characterized by its relatively large body size, coarsely striated cuticle, spacious buccal cavity with cuticularized rings, six inner labial sensilla setiform, six outer labial setae, and four long cephalic setae. The pharynx is notably muscularized, and the spicules are straight and jointed with a slightly swollen proximal end and a hooked distal end. The gubernaculum is brownish and comma–shaped, and the tail is conico–cylindrical with terminal setae. Phylogenetic analyses using maximum–likelihood and Bayesin inference, based on small subunit and D2–D3 fragment of large subunit rDNA sequences, place Desmolaimus magnus sp. nov. within the framework of the family Linhomoeidae and Metadesmolaimus robustus sp. nov. within Xyalidae. Topology trees at the family level show genera Desmolaimus and Metadesmolaimus as paraphyletic groups, the genus Terschellingia as a monophylectic group, the genus Theristus as a monophylectic group based on SSU sequence, the genus Daptonema as a monophylectic group based on LSU sequence.

Description of Bolbolaimus major sp. nov. (Nematoda), from the Yellow Sea, China and phylogenetic analysis in Microlaimidae.

Bolbolaimus major sp. nov. is described from Rizhao coast along the Yellow Sea. The new species is characterized by relatively large body size, cuticle strongly annulated, six outer labial sensilla setiform, four cephalic setae long, buccal cavity wide with one large dorsal tooth and two small subventral teeth, amphidial fovea unispiral shaped oval in males and circular in females, spicules curved with swollen proximal end, gubernaculum with anterior-hooked dorso-caudal apophysis, and tail conical with short spinneret. A phylogenetic analysis of maximum-likelihood and Bayesin inference based on rDNA sequences confirms the taxonomic position of Bolbolaimus major sp. nov. within the family Microlaimidae. Tree topology in Microlaimidae shows genus Microlaimus as polyphyletic group and genera in Microlaimidae are closely related.

Microstructural Adaptation for Prey Manipulation in the Millipede Assassin Bugs (Hemiptera: Reduviidae: Ectrichodiinae).

Species in Ectrichodiinae are known for their prey specialization on millipedes. However, knowledge of the morphological adaptations to this unique feeding habit was limited. In the current study, we examined the microstructures of the antennae, mouthparts, and legs of four millipede feeding ectrichodiines, Ectrychotes andreae (Thunberg, 1888), Haematoloecha limbata Miller, 1953, Labidocoris pectoralis (Stål, 1863), and Neozirta eidmanni (Taueber, 1930), and compared them with those of three species of tribelocephalines, a group closely related to Ectrichodiinae. On the antennae, we found four types of antennal sensilla. On the mouthparts, we recognized four types of labial sensilla. Sampled ectrichodiines have distinctly more and denser slightly transverse ridges on the external side of mandibles than tribelocephalines. E. andreae and H. limbata possess numerous small papillae fringed with densely arranged finger-print-like grains on the trochanter and femur; these probably facilitate the immobilization of prey. Overall, our study illustrates, at a microstructural level, the remarkable morphological adaption of prey manipulation in ectrichodiine, and has enhanced our understanding about stenophagy in the family Reduviidae.

Description of two new species of Nematoda: Litinium macramphida sp. nov. (Oxystominidae) and Cyartonema breviseta sp. nov. (Cyartonematidae) from the Yellow Sea, China.

Two new species of Nematoda, Litinium macramphida sp. nov. and Cyartonema breviseta sp. nov. are described from the Yelllow Sea. Litinium macramphida sp. nov. is characterized by body relatively long, inner and outer labial sensilla setiform with same length, amphideal fovea large and drop-shaped with amphideal aperture ovoid, spicules short and wide, gubernaculum simple and boat shaped, two precloacal supplements, and tail conical with rounded tip. Cyartonema breviseta sp. nov. is characterized by body short and slender, four cephalic sensilla papilliform, amphideal fovea circular and large, spicules curved and sickle-shaped, gubernaculum with dorsal-caudal apophysis and posterior end anteriorly hooked, and tail conical.

Scanning Electron Microscopy of Antennae and Mouthparts of Mezira yunnana Hsiao (Hemiptera: Aradidae): Specialized Microstructures Reflecting Adaptation to Mycetophagy.

Many species of the family Aradidae (also known as flat bugs) feed on fungal mycelia and fruiting bodies. In order to better understand the morphological adaptation to this unique feeding habit, we examined the microstructure of antennae and mouthparts of an aradid species, Mezira yunnana Hsiao, using scanning electron microscope, and documented the fungal feeding process under laboratory conditions. The antennal sensilla include three subtypes of sensilla trichodea, three subtypes of sensilla basiconica, two subtypes of sensilla chaetica, sensilla campaniformia, and sensilla styloconica. The apex of the second segment of flagellum has a large number of various sensilla forming a sensilla cluster. The labial tip is distally constricted, which is rarely observed in other Pentatomomorpha species. The labial sensilla include three subtypes of sensilla trichodea, three subtypes of sensilla basiconica, and a sensilla campaniformia. The tip of the labium has only three pairs of sensilla basiconica III and small comb-shaped cuticular processes. The external surface of the mandibular apex has 8-10 ridge-like central teeth. A series of key morphological structures associated with mycetophagous feeding habit were identified, which will facilitate future studies on adaptive evolution of species in Pentatomomorpha as well as in other heteropteran lineages.

Gammarinema scyllae sp. n. and Monhystrium mangrovi sp. n. (Nematoda: Monhysteridae) from land crabs from New Caledonia

Two new species of nematodes associated with crabs are described from New Caledonia. Gammarinema scyllaesp. n. from the gill chambers of Scylla serrata (Forsskål) is characterised by 3–4 mm long body, small outer labial and cephalic sensilla, distinct ocelli, short straight spicules and sub-cylindrical tail. Monhystrium mangrovisp. n. from the gill chambers and body cavity of mangrove crab Neosarmatium sp. is characterised by 1–1.4 mm long body; outer labial sensilla longer than cephalic sensilla, amphid located at level with posterior stoma chamber, denticles in posterior stoma chamber and five pairs of genital papilla on tail. Phylogenetic relationships of two new species and other nematodes from the family Monhysteridae are analysed based on 18S and partial 28S rDNA sequences.

Ultrastructural Variations of Antennae and Labia Are Associated with Feeding Habit Shifts in Stink Bugs (Heteroptera: Pentatomidae).

Simple SummaryStink bugs (Pentatomidae) are one of the most diverse insect groups in suborder Heteroptera (Hemiptera). They are either plant feeders or predators, comprising series of invasive agricultural pests and natural enemies with great economic importance. Species of stink bugs possess various antennal and mouthpart traits apparently related with feeding habits, but key morphological traits associated with feeding habit shift remain largely unexploited. In this study, we compare the ultrastructures of antennae, labia, and mandibular and maxillary stylets of 17 pentatomid species, representing both phytophagous and predatory species chosen from four subfamilies. We identify a set of key ultrastructural characteristics closely associated with feeding habit transition in stink bugs and discuss their adaptative implications in an evolutionary aspect.The family Pentatomidae (stink bugs) is one of the largest groups in Heteroptera, containing many important pests and natural enemies. They exhibit highly diversified feeding habits and related structural modifications, but the key morphological characteristics associated with feeding habit radiation remain unclear. In the current study, we address this question by analyzing morphological variations of feeding related organs. We compare the ultrastructures of antennae and mouthparts across the chosen 17 species in Pentatomidae, representing both plant feeders and predators from four subfamilies. A strong association between ultrastructural adaptation and feeding habit transition has been revealed. The long, sharp, and hook-like mandibular teeth and maxillary barbs are exclusively present in predatory Pentatomidae, suggesting their tight association with the shift of feeding habit from phytophagy to predation. Significant differences between phytophagous and predatory species are also found in antennal and labial sensilla types and arrangements, implying their important function in food selection. Our data identify a series of key morphological structures associated with feeding habit variations among stink bugs, which will facilitate future studies on adaptive evolution of feeding habits, utilization, and population control of economic species in Pentatomidae as well as in other heteropteran lineages.

New free-living nematode species and records (Chromadorea: Plectida and Desmodorida) from the edge and axis of Kermadec Trench, Southwest Pacific Ocean.

One new nematode species is described and two new species records are provided from the edge (6,080 m depth) and axis (7,132 m) of Kermadec Trench, Southwest Pacific. Leptolaimus hadalis sp. nov. is characterised by medium body 587–741 μm long, labial region not offset from body contour, inconspicuous labial sensilla, amphid located 12–19 μm from anterior end, female without supplements, male with four tubular precloacal supplements (alveolar supplements absent), tubular supplements almost straight with dentate tip, arcuate spicules and weakly cuticularized dorsal gubernacular apophyses strongly bent distally. In a previously published ecological survey of Kermadec Trench, L. hadalis sp. nov. was the most abundant species in a core obtained at 8,079 m water depth and third most abundant species in a core obtained at 7,132 m, while only one individual was found at 6,096 m depth, and none at 9,175 m depth (Leduc & Rowden, 2018). Alaimella aff. cincta and Desmodora aff. pilosa are recorded for the first time from the Southwest Pacific region. Prior to the present study, Alaimella had only been recorded from coastal locations and from the Weddell sea to a depth of 2,000 m. The record of Desmodora aff. pilosa at 6,080 m depth is the deepest record of a Desmodora species to date, although unidentified Desmodora specimens have been found as deep as 6,300 m in the South Sandwich Trench. The morphology of the Kermadec Trench Alaimella aff. cincta and Desmodora aff. pilosa specimens bear a strong resemblance to their respective type populations from the Northern Hemisphere, but further morphological and molecular data are required to ascertain whether they in fact represent distinct species.

A new genus and species of the family Microlaimidae (Nematoda: Chromadorea) from intertidal sand of the Jeju Island, South Korea

As a part of the study of marine nematofauna of a sandy intertidal zone of Jeju Island (South Korea), a number of species have been proven as new for science. Here a new species representing a new genus of the family Microlaimidae (Chromadorea), Jejulaimus sinyangensis gen. n., sp. n. is described. The new monotypic genus is characterized by head set off abruptly from the body; anterior sensilla pattern 6+10, where six outer labial setiform sensilla together with four longer cephalic setiform sensilla are integrated in a common crown; pharyngostoma armed with a dorsal tooth and surrounded by convex muscular pharyngeal tissue, forming an anterior pharyngeal bulb which is distinctly set off from the rest of the pharynx; terminal pharyngeal bulb oval; ventral pore and ampulla of the excretory-secretory gland situated just posterior to the nerve ring; an only anterior testis present. The new genus bears some resemblance to the genera Bolbolaimus, Pseudomicrolaimus and Spirobolbolaimus in having an anterior pharyngeal bulb and in the position of the ventral pore of the excretory/secretory gland, but differs from them by anterior sensilla pattern 6+10, absence of subventral teeth in buccal cavity, and monorchic condition of male reproductive system.

Two new species of nematodes from shallow and deep-water sediments in the South China Sea.

Two new species of free-living marine nematodes from the South China Sea are described: Gomphionema setiforme sp. nov. from intertidal sediment and Paracomesoma longissimum sp. nov. from upper continental slope sediment. Gomphionema setiforme sp. nov. is characterized by the punctated cuticle without lateral differentiation and cuticular pores; short cephalic setiform sensilla; spiral amphideal fovea with 4 turns close to the anterior body extremity; large cuticularized buccal cavity with a massive dorsal tooth; pharynx with a large posterior bulb; short, curved spicules; knife-like gubernaculum without apophyses and 11 cup-shaped precloacal supplements. Paracomesoma longissimum sp. nov. is characterized by cuticle with transverse rows of fine punctuations without lateral differentiation; buccal cavity with three teeth; lateral outer labial setiform sensilla 1.5 times as long as the other four outer labial setiform sensilla; spiral amphideal fovea with 2.5 turns; spicules 350360 m long or 15.716 times cloacal body diameter; plate-like gubernaculum without apophyses and 2528 papilliform precloacal supplements.

Litinium gludi sp. nov. (Nematoda, Oxystominidae) from Kermadec Trench, Southwest Pacific Ocean

Recent work on the taxonomy of nematodes in Southwest Pacific Ocean trenches has led to the discovery of taxa which so far appear to be restricted to the oceans’ deepest environments. Here, Litinium gludi sp. nov. is described based on specimens obtained from a deep basin within the Kermadec Trench at 9540 m water depth. The new species differs from other species of the genus in having a conico-cylindrical tail, papillose labial sensilla, and heart- or leaf-shaped amphideal fovea. Both SSU and LSU phylogenetic analyses provide strong support for the placement of the new species within a clade containing both Thalassoalaimus and Litinum, and within Oxystomininae, which is consistent with the structure of the female reproductive system with only one posterior ovary in this subfamily. Our molecular analyses also indicate that the new species is most closely related to Thalassoalaimus despite lacking a caudal capsule, the main trait characterizing the latter genus, and despite being most morphologically similar to Litinium, particularly in the unusual shape of the amphideal fovea. However, given the changing definitions of the closely-related genera Thalassoalaimus and Litinium in recent years, available GenBank sequences may have been misidentified, which makes the interpretation of molecular phylogenetic analyses problematic. Given the current morphological definitions of Litinium and Thalassoalaimus, we choose to place the new species within Litinium, despite the apparently contradictory findings of molecular phylogenetic analyses. The placement of Cricohalalaimus in a clade with Thalassoalaimus and Litinium in both SSU and LSU analyses indicates that this genus should be placed within the Oxystomininae and not the Halalaiminae as in the current classification. This new proposed grouping is consistent with variation in the structure of the female reproductive system, a feature which appears more taxonomically informative than amphid shape for subfamily-level classification.

Ultra structural study on different sensory structure and some associated body parts of mango mealy bug, Drosicha mangiferae (G.) by scanning electron microscopy

Ultra structural study on different sensory structure and some associated body parts of mango mealy bug, Drosicha mangiferae (G.) by scanning electron microscopy

Differential Thresholds of Proteasome Activation Reveal Two Separable Mechanisms of Sensory Organ Polarization in C. elegans.

Cephalization is a major innovation of animal evolution and implies a synchronization of nervous system, mouth, and foregut polarization to align alimentary tract and sensomotoric system for effective foraging. However, the underlying integration of morphogenetic programs is poorly understood. Here, we show that invagination of neuroectoderm through de novo polarization and apical constriction creates the mouth opening in the Caenorhabditis elegans embryo. Simultaneously, all 18 juxta-oral sensory organ dendritic tips become symmetrically positioned around the mouth: While the two bilaterally symmetric amphid sensilla endings are towed to the mouth opening, labial and cephalic sensilla become positioned independently. Dendrite towing is enabled by the pre-polarized sensory amphid pores intercalating into the leading edge of the anteriorly migrating epidermal sheet, while apical constriction-mediated cell–cell re-arrangements mediate positioning of all other sensory organs. These two processes can be separated by gradual inactivation of the 26S proteasome activator, RPN-6.1. Moreover, RPN-6.1 also shows a dose-dependent requirement for maintenance of coordinated apical polarization of other organs with apical lumen, the pharynx, and the intestine. Thus, our data unveil integration of morphogenetic programs during the coordination of alimentary tract and sensory organ formation and suggest that this process requires tight control of ubiquitin-dependent protein degradation.

Bursaphelenchus juglandis n. sp. (Nematoda: Aphelenchoididae), an associate of walnut twig beetle, Pityophthorus juglandis, the vector of thousand cankers disease

Summary Bursaphelenchus juglandis n. sp. was isolated from the walnut twig beetle, Pityophthorus juglandis, and walnut trees, Juglans spp. with symptoms of thousand cankers disease, in California, USA. Based on analysis of three rRNA genes and morphological features (three lines in lateral field, small arched vulval flap in female, broad spicule with two lines along blade and small cucullus, digitate dorsally bent condylus, male tail pattern of five papilliform papillae and one pair of glandpapillae (P5), and curved conical female tail), the new species belongs to the Abietinus group within Bursaphelenchus. It differs from similar species of this group by the presence of a cephalic disc with lateral labial sensilla at the disc border, and in having thick spicules with the capitulum surface almost parallel to a virtual direct line extending from the spicule end. An emended diagnosis, tabular polytomous identification key and compendium of species with the lists of their vectors, plant hosts, and distribution are provided for the Abietinus group. The diagnostics of the propagative developmental stages is given, including sex differences; the transmission dauer stage was identified as the third stage and its description given with sexual differences. A molecular phylogeny of Bursaphelenchus is provided based on partial 18S rRNA, ITS rRNA and the D2-D3 expansion fragments of 28S rRNA gene sequences. A PCR with a species-specific primer was developed for detection of B. juglandis n. sp.

Two New Species of Free-Living Marine Nematodes of the Desmodoridae from Mangrove Wetlands of Xiamen Bay, China

Mangroves are unique in their biodiversity, but studies on their meiobenthic biodiversity in China are scarce. Despite the importance of mangroves, little work has been done on the classification of nematodes in mangrove wetlands. Fujian Province is the most northern point of China’s natural mangrove distribution, and it is also one of the provinces with the earliest constructed mangrove forest. In this paper, two new free-living marine nematode species of Desmodoridae from the Xiamen mangrove wetlands in China are described. Metachromadora xiamenensis sp. nov. is characterized by a cylindrical body, and smooth head capsule set off from the rest of the body. The cuticle is finely annulated and thickened at the midbody. Lateral ridges run from the posterior end of the pharynx to the middle of the tail. The amphid foveae is loop shaped and opens at the top with a double contour amphidial, pharynx with bipartite cuticularized internal cavity. There are 18 tubular precloacal supplements and tail with three small protuberances. Molgolaimus euryformis sp. nov. is characterized by a relatively short and plump body with finely annulated cuticle, which is particularly obvious in the tail. The head is small and wide with intensive striates. The inner and outer labial sensilla are indistinct with short spicules and ventral apophysis, a gubernaculum with a block-shaped hook, a swollen conical-cylindrical tail and an absence of precloacal supplements.

A new free-living marine nematode species of the genus <i>Phanoderma</i> Bastian, 1865 (Enoplida: Phanodermatidae) from the East Sea, Korea

A new species of free-living marine nematode is described from intertidal sediments of the East Sea, Korea. Phanoderma koreense sp. nov. is characterized by the presence of well-developed pharyngeal and cephalic capsule, six inner labial sensilla present as minute papillae around with circular groove, long and slender spicules with 4-5 serrated distal end, located at the base of the precloacal supplement, a series of eight to nine stout and short setae on the ventral cloacal region and conico-cylindrical tail with two pairs of blunt setae. In this study, we provide taxonomic descriptions and illustrations of a new species by differential interference contrast microscope and a pictorial key to the valid species of Phanoderma Bastian, 1865. This is the first record of the genus Phanoderma in the East Sea, Korea.

Morphological study of the labial sensilla in Nabidae (Hemiptera: Heteroptera: Cimicomorpha)

The study presents new data on the morphology and distribution of the labial tip sensilla of six species of two nabid subfamilies—Protosteminae and Nabinae (Heteroptera: Cimicomorpha), which were obtained using a scanning electron microscope. In both taxa, there are five morphologically distinct types of sensilla on the tip of the labium: peg sensilla with a terminal pore, nonporous peg sensilla, elongated placoid sensilla with wall pores (multiporous), and trichoid sensilla. In addition, oval plate sensilla with a terminal pore (Tp-opls) were observed in the genus Himacerus. Campaniform sensilla and nonporous chaetic sensilla were observed on the surface of the last segment of the labium in all of the studied species. Over a dozen trichoid sensilla were scattered on the last segment of the labium only in the genus Prostemma. Based on their external structure, it is likely that these sensilla are chemosensitive and mechanosensitive. The oval plate sensilla with a Tp-opls (gustatory) in Himacerus (Nabinae) represent a morphological novelty that probably evolved independently of other nabids.

Campydoroides manautei gen. et sp. nov. from New Caledonia and a reappraisal of the suborder Campydorina (Nematoda)

The new genus and species Campydoroides manautei Holovachov gen. et sp. nov. is placed in the suborder Campydorina and is characterised by a transversely striated cuticle without lateral alae, body pores or epidermal glands; somatic sensilla only on pharyngeal region and on tail; a truncate labial region with papilliform inner labial, outer labial and cephalic sensilla; a stirrup-shaped amphid with transverse slit-like opening; a conoid stoma with strongly cuticularised walls and large protrusible dorsal tooth; a cylindrical pharynx with distinct basal bulb but without valves; a large ovoid cardia; didelphic, amphidelphic female gonads with antidromously reflexed ovaries and without spermatheca; a transverse vulva; a straight vagina without pars refringens vaginae or epiptygmata; an elongate tail with caudal glands and spinneret. The new genus is similar to the genera Campydora Cobb, 1920 and Udonchus Cobb, 1913 in having papilliform labial and cephalic sensilla, a stirrup-shaped amphid with a transverse slit-like opening, a stoma with a well-developed protrusible dorsal tooth, and a muscular pharynx with a strongly developed basal bulb, but can be easily separated from both in details of a stoma morphology. The systematics of the suborder Campydorina is revised. Halirhabdolaimus Siddiqi, 2012 is synonymised with Syringolaimus de Man, 1888.