Sensory Setae Research Articles

Statocyst Ultrastructure in the Norwegian Lobster (Nephrops norvegicus).

Statocyst anatomy and fine morphology in Norwegian lobster (Nephrops norvegicus) are studied for the first time using scanning and transmission electron microscopy. N. norvegicus exhibits sensory setae projecting from the statocyst inner cavity floor into a mass of sand granules (statoconia) embedded in a gelatinous substance. The setae are distributed in four areas: a curved field made up of an inner single row and an outer double row that run on a circle around the medial and lateral rim of the central depression, a small setal field in the posterior part, a large setal field, opposite to the small field, and a short row, running internally and lying parallel to the inner single row, next to the small setal field. A study of the fine morphology of the statocyst sensory setae shows that the structure of the setae in the different areas is similar, with a bulb (the proximal portion of the sensillum), a setal shaft, a tooth (the smooth portion of the bulb), a fulcrum (a transverse fold), and filamentous hairs. The hair cells are firmly implanted within the cuticular layer. Although the type of innervation of the statocyst was not determined in the present study, the close taxonomic position of the lobster to that of the crayfish and crab would suggest that the setae in N. norvegicus are pure mechanoreceptors rather than sensory cells.

Two new species of the order Monhysterida (Nematoda) from the sea of China.

Two new marine nematode species belonging to the order Monhysterida are described from the sea of China. Halomonhysterazhangisp. nov. is characterized by its relatively small body size; short anterior sensory setae; small, circular amphidial fovea located at the level of buccal cavity base; funnel-shaped buccal cavity; an excretory-secretory system with a large ventral gland and opening as a very narrow canal just posterior to the level of cephalic setae; slightly curved slender spicules with cephalated proximal end and tapered distal end; rod-like gubernaculum without apophysis; two papilliform precloacal supplements just in front of the cloaca; conico-cylindrical tail with two ventral papillae, each with a seta; and distance between the vulva and anus slightly longer than the tail length. This is the first new species of epiphytic nematode reported in China. The second new species, Stylotheristusflagellicaudatussp. nov., has a relatively shorter body and longer tail; striated cuticle; The anterior sensilla arranged in two circles, the first circle consisting of six inner labial setiform papillae (3-4 µm) and the second circle consisting of 16 long setae (12-19 µm); a transversely oval amphideal fovea; a well-developed muscle around the funnel-shaped buccal cavity; short spicules and a gubernaculum composed of a single piece; and precloacal supplements absent. An updated key to all species of Halomonhystera and pictorial key to all species of Stylotheristus are also given.

The first record larvae of the genus Peltogaster (Rhizocephala: Peltogastridae) with eyes and unilobed male aesthetasc

The complete larval development of Peltogaster lineata Shiino, 1943 (Rhizocephala: Peltogastridae), including five nauplii and one cypris stage, is described and illustrated using SEM. The development took 3.5–4 days at a water temperature of 22–23 °C. Peltogaster lineata has the peltogastrid type of development. Nauplii possess a large and clearly reticulated flotation collar, six pairs of dorsal shield setae with the U-shaped second pair, long segmented frontolateral horns each with two subterminal setae, and a long seta at the antennal basis. The attachment disc in female cyprids has a flap-like extension at the posterior margin. Cyprids of both sexes possess two sensory setae at the attachment disc. The large male aesthetasc is unilobed, the female subterminal aesthetasc terminates into two thin long filamentous processes. Larvae of P. lineata have distinctly visible nauplius eyes.

A new species of the genus Ceriodaphnia Dana, 1853 (Cladocera: Daphnidae) from Eastern Siberia (Russia) that combines morphological features of two species groups.

Taxa of the genus Ceriodaphnia Dana, 1853 (Cladocera: Daphniidae) are ubiquitous in temperate and tropical lakes, and the taxonomy of the genus is confused. Moreover, present keys are often regional and insufficient for the taxonomic assignment of species at a global scale. This communication is aimed at improving our understanding of the C. dubia s.l. species group. We redescribe C. dubia s.l. from Northern Eurasia and describe a new species from Central Yakutia (Eastern Siberia, Russia). In contrast to typical members of the C. dubia group, C. nikolaii sp.nov. has the postabdomen of the parthenogenetic female with preanal margin slightly or strongly projecting and angulated. Moreover, adult males have a pronounced preanal angle and sensory seta of antenna I which is shorter than the longest easthetasc. Our finding challenges current definitions of species groups in Ceriodaphnia. Indeed, a postabdomen shape with a strongly projected preanal angle is characterstic of another group of this genus, namely the C. laticaudata-group. We found a taxon that combines the diagnostic morphological characters of two species groups. Further development of the genus taxonomy must be accompanied by redescriptions of all well-accepted and dubious taxa from their type localities and revisions of populations from other localities of the world.

Parajapyx giecuevasae n. sp., the first Parajapygidae (Diplura) from the Philippines

Parajapyx giecuevasae, n. sp., the first Philippine member of the Parajapygidae and the second reported Diplura from the Philippines, is described from Mt. Makiling, Laguna. It is distinct from other Parajapyx species by having the following combination of characters: mandible with five teeth and three denticles; prescutum of metanotum with 2+1 setae; tergite X with 12+1+12 macrosetae and 10+1+10 normal setae; and subcoxal organ with 4 accompanying setae, 9 glandular setae and 5 sensorial setae.

Pathogenicity, ultra-structural growth and development of green muscardine fungus, Metarhizium anisopliae (Metschnikoff) Sorokin (Ascomycota: Hypocreales) on maize fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

BackgroundThe fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is a devastating pest of maize, difficult to manage using a single pest management tactic. The entomopathogenic fungus (EPF), Metarhizium anisopliae being an eco-friendly component, could be an effective tool for managing this notorious pest owing to its preferred habitat, principally the whorl region.ResultsMetarhizium anisopliae (TNAU-MA-GDU) isolated from FAW was evaluated against 2nd instar larvae of S. frugiperda reared under laboratory conditions. The pathogenicity and infection process were also studied through scanning electron microscope (SEM). The LC50 value for M. anisopliae isolate TNAU-MA-GDU was recorded as 5.8 × 104 spores ml−1 against the second instar larvae of S. frugiperda. SEM observations on the infection process revealed the adherence of the conidia on the head, cuticular ornamentations of the thorax, sensory seta, and legs at 24 h post-infection (hpi). Formation of germ tube and appressoria was observed from 48 hpi with subsequent hyphal development at 72 hpi. Complete networking of mycelium and conidiogenesis observed after 168 hpi.ConclusionAn understanding of fungal–host interactions at the ultramicroscopic levels could reform present tactics for developing hyper-virulent EPF strains.

Sea Lice Are Sensitive to Low Frequency Sounds

The salmon louse Lepeophtheirus salmonis is a major disease problem in salmonids farming and there are indications that it also plays a role in the decline of wild salmon stocks. This study shows the first ultrastructural images of pathological changes in the sensory setae of the first antenna and in inner tissues in different stages of L. salmonis development after sound exposure in laboratory and sea conditions. Given the current ineffectiveness of traditional methods to eradicate this plague, and the strong impact on the environment these treatments often provoke, the described response to sounds and the associated injuries in the lice sensory organs could represent an interesting basis for developing a bioacoustics method to prevent lice infection and to treat affected salmons.

Comparative study of the ditrophic interaction between Beauveria bassiana and Plutella xylostella

In the present investigation, hyperparasitic interaction between B. bassiana, TM (MH590235) and P. xylostella was studied through scanning electron microscopy and chromatographic techniques. Dose-mortality responses showed an increase in mortality of larva with an increase in spore concentration. The LC50 value for B. bassiana isolate TM (MH590235) was 2.4 × 107 spores mL-1. The ditrophic interaction between B. bassiana and P. xylostella after 24h revealed the adherence of conidia on stemmata, sensory setae, maxillary palpi and legs. After 48h post-infection (hpi), germination of the conidia and appressorium formation was observed. Formation of hyphae and initiation of fungal networking was observed at 72 hpi. Complete ramification by mycelia and conidiogenesis of B. bassiana was observed over the mycosed cadaver after 168 hpi. Subsequently, typical sympodial conidiophores of B. bassiana bearing secondary spores were also observed. The metabolome profile of healthy larvae of P. xylostella revealed the presence of non-volatile organic compounds (NVOCs) like docosene, nonadecene, palmitic acid and heneicosane. However, the NVOC profile was different in the P. xylostella larvae hyperparasitized by B. bassiana. The metabolites present in the infected cadaver were phthalate esters, hydroxyquebrachamine and lactones.

A rapid and accurate method for identifying sexuality of Indarbela obliquifasciata Mell (Lepidoptera, Metarbelidae) adults and pupae

The bark-eating caterpillar, Indarbela obliquifasciata Mell has become a major pest of garden plants in Guangzhou, China. However, little is known about the sex identification of either adults or pupae. In this paper, according to a comparative morphological study of 55 adults and their corresponding pupae or puparia, we concluded a rapid and accurate method for identifying its sexuality. The results showed a distinct sexual dimorphism in both adults and pupae. In male adults, the antennae are broadly bipectinate, and the ctenii are long with plumose sensory setae. While in female adults, the antennae are narrowly bipectinate, and the ctenii are short with rare setae. In male pupae, the spines on 8th abdominal segment are distributed in a circle, and segments 4–7 are mobile. While in female pupae, the spines on 8th abdominal segment are partially absent on ventral side, and with a short slit at middle part, and segments 4–6 are mobile. The results of this study are of great significance for the field investigation of the sex ratio of adults and pupae and for the study of female pheromones.

A new Caribbean species of Hylaeanura Arlé, 1966 (Collembola, Neanuridae, Pseudachorutinae).

We here describe a new Collembola species, Hylaeanuraemiliaesp. nov., from the Luquillo Experimental Forest in Puerto Rico. We describe H.emiliaesp. nov. as a distinct species based on the enlarged sensilla s3 in antennal segment IV, the absence of modified sensorial setae in abdominal segment IV and the presence of four setae on each dens. An updated key with illustrations for the identification of worldwide species of the genus is included.

Toxicological and epidemiological studies of scorpion sting cases and morphological characterization of scorpions (Leiurusquin questriatus and Androctonus crassicauda) in Luxor, Egypt.

Scorpion envenomation is a common acute life threatening health problem in developing countries as Egypt. Scorpion venom is a complex structure composed of neurotoxic proteins, salts, acidic proteins, and organic compounds, thereby having of neurologic, cardiovascular, hematologic, and renal side effects, in addition to local effects such as redness, pain, burning, and swelling. The study consisted of two parts to describe demographic characteristics, toxicological manifestations of scorpion sting cases in Luxor, Egypt and morphological characterization of the commonest scorpion species in the studied community for easy rapid identification of scorpion species by doctors from the patient history to provide better choices of management. First part of the study include all cases of scorpion envenomation attending General Hospital of Esna, Luxor, Egypt during the period of scorpion activity 2017, demographic data was collected then cases were assessed for clinical manifestations, ECG, complications and deaths related to scorpion species. Second part: scorpions were collected from areas around patient housing for morphological description of their sense organs and venom apparatus by Scanning Electron Microscopy. A total of 110 cases of scorpion stings were reviewed, males 81 (72.9%) and females 30 (27.1%), with a mean age of 31.9 ± 17.9 years. Localized pain was the most frequent presenting complaint (89 80.2%), vomiting was the commonest clinical symptom (90.9%). All scorpion stings were due to the most endemic species in North Africa, Leiurusquinquestriatus & Androctonuscrassicauda. Death rate among cases was (5.5%) all were Abroug's Grade III. Cardiac dysrhythmia and subsequent pulmonary edema were the commonest cause of death. Clinical manifestations were more sever in Leiurus quinquestriatus stings while death rate was more in Androctonus crassicauda stings. The morphological characterization of the sense organs (eyes, pedipalps, pectines& sensory setae) and venom apparatus of the scorpions L. quinquestriatus & A. crassicauda were described by Scanning Electron Microscopy. Scorpion sting is an acute heath threating in Southern Egypt, Leiurus quinquestriatus & Androctonus crassicauda are most endemic scorpion species in Southern Egypt. More attention for scorpion envenomation in such subtropical hyper desert localities is required to eradicate toxic scorpion species and prevent possible causes of deaths.

Do molecular phylogenies unravel the relationships among the evolutionary young “Brafordian” families (Copepoda; Calanoida)?

Among the most derived calanoid copepod superfamily Clausocalanoidea about half of the genera belong to the so-called “Bradfordian” families that are defined by the presence of sensory setae at the maxilla and maxilliped. Many of these “Bradfordian” taxa are insufficiently well described, because their taxonomy is complicated and phylogenetic relationships are not completely resolved. We therefore aimed to unravel their phylogenetic relationships using molecular multi-gene analyses. We conducted molecular multi-gene analysis on 26 species from 15 genera representing all seven “Bradfordian” families using five gene fragments, the nuclear ribosomal 18S, 28S and internal transcribed spacer 2 DNA, and mitochondrial cytochrome c oxidase subunit I and cytochrome b. The monophyly of “Bradfordians” as one lineage in the superfamily Clausocalanoidea was supported by Maximum Likelihood and Bayesian Inference multi-gene analyses. Except for the support of species belonging to the same genus and specimens belonging to the same species, no phylogenetic relationships among genera and families were supported. The impossibility of resolving phylogenetic relationships among “Bradfordian” genera and families may be due to the young age or fast radiation of “Bradfordians” within the mostly derived calanoid superfamily Clausocalanoidea. Therefore, mutation rates might be not sufficient to track phylogenetic relationships. Evidence on phylogenetic relationships between genera and families remain unresolved after implementing integrated morphological and molecular taxonomic approaches.

Structural optimization and amorphous calcium phosphate mineralization in sensory setae of a terrestrial crustacean (Isopoda: Oniscidea)

Terrestrial isopods possess large sensory setae on their walking legs. Increased fracture resistance of these elongated structures is of crucial importance, making the exoskeleton forming the setae an interesting durable material that may inspire biomimetic designs. We studied the cuticle of the sensory setae with analytical electron microscopy in order to gain detailed insights into its structure and composition at the nanometer scale and identify features that increase the fracture resistance of these minute skeletal elements. The setae are stiff structures formed by mineralized cuticle that are connected to the leg exoskeleton by a non-mineralized joint membrane. Our results demonstrate that different layers of the setal cuticle display contrasting organizations of the chitin-protein fibers and mineral particles. While in the externally positioned exocuticle organic fibers shift their orientation helicoidally in sequential layers, the fibers are aligned axially in the internally positioned endocuticle. In the setal cuticle, layers of structurally anisotropic cuticle likely providing strength in the axial direction are combined with layers of isotropic cuticle which may allow the setae to better resist perpendicular loading. They are further strengthened with amorphous calcium phosphate, a highly fracture resistant mineral rarely observed in invertebrate skeletons.

Probing the settlement signals of Amphibalanus amphitrite

To achieve their reproductive potential, barnacles combine tactile exploration of surface structural properties and integration of cellular signals originating from their antennular sensory setae within a developmentally defined, temporally narrow window of settlement opportunity. Behavioural assays with cyprids coupled with biometric analysis of scanning electron microscopy-acquired images in the presence of specific chemical compounds were used to investigate how settlement on a substratum is altered in response to the presence of these compounds. Impeding tactile exploration was shown which altered cellular signalling and/or induced malformation of anatomical features of the antennular sensory setae, which disrupted the settlement behaviour of the model barnacle species Amphibalanus amphitrite. It is concluded that surface exploration by the cyprids relies on mechanical and nociception-related and calcium-mediated signals while a protein kinase C signalling cascade controls the timely metamorphosis of the cyprids to sessile juveniles.

Low pH Water Impairs the Tactile Sense of the Postlarvae of the Giant Freshwater Prawn Macrobrachium rosenbergii.

The effect of low pH on the tactile sense of Macrobrachium rosenbergii postlarvae was determined in the laboratory by means of two behavioural assays: shelter (netting) occupancy and jumping response to touch stimuli (taps) by a glass micropipette. The postlarvae were acclimated to pH 4, pH 5, pH 6 and pH 7.5 (control) in 45 L aquaria 5–7 d before the experiments. Shelter occupancy decreased with pH and was significantly lower at pH 4 and pH 5 than at pH 6 and in the control. The jumping response instantly followed a tap 93–98% of the time in the control, pH 6 and pH 5 treatments. However, the postlarvae showed significantly lower jumping response (65%) at pH 4, indicating an impaired tactile sense. Low pH 4–5 probably degrades the chitin of the sensory setae and inhibits the surface mechanoreceptors of the prawn postlarvae.

Study on Tullbergiidae of Tibet, China I. Metaphorura, Mesaphorura and Prabhergia (Hexapoda, Collembola).

The Tullbergiidae of Tibet is studied for the first time and the genus Metaphorura Bagnall, 1936 is firstly recorded in China. Metaphorura motuoensis sp. n. from southeastern Tibet is described and illustrated. It is characterized by the presence of 1+1 pseudocelli on thoracic segment I, few vesicles (14 -16) on PAO, pseudocellar formula as 11/111/11111, all pseudocelli of type II, setae p4 on abdominal segment V as microsetae, weakly differentiated sensory seta p3 on abdominal segment V, absence of median process on Abd VI. In addition, Mesaphorura yosii (Rusek, 1967), Mesaphorura hylophila Rusek, 1982, and Prabhergia imadatei Tamura & Zhao, 1996 are recorded in Tibet for the first time. The type specimens of P. imadatei are re-examined and errors in the original description of chaetotaxy are corrected.

Euphilomedes biacutidens (Ostracoda, Myodocopida, Philomedidae), a new species from China Sea.

Ostracods are one of the major groups of marine benthos, inhabiting virtually all oceanic environments worldwide, and a total of 31 species have been recorded in genus Euphilomedes Kornicker, 1967. In the present study, we describe a new species Euphilomedes biacutidens collected from the Taiwan Strait and South China Sea. E. biacutidens sp. nov. differs from the related species of the genus Euphilomedes in having a unique combination of the characteristics of spines on carapace, the filaments on sensory seta, the arrangement of setae on tip of the first antenna, the numbers of setae on appendages, the claws on fifth limb, the teeth on the comb of the seventh limb and furcal claws. It is particularly obvious that it has a bifurcated and pointed ventral corner of the rostrum, two spines on the posterior margin of right valve, a row of teeth along the inner margin of article 3 of the endopod of the second antenna, and some long claws instead of setae on the fifth limb.

A complete survey of normal pores on a smooth shell ostracod (Crustacea): Landmark-based versus outline geometric morphometrics.

Pores and sensilla on ostracod shell have often been used in studies of ontogeny, taxonomy, and phylogeny of the group. However, an analysis of sexual dimorphism and variation between valves in the number and distribution of pores is lacking. Also, such studies have never been done on a widely distributed, morphologically variable, and weakly ornamented freshwater ostracod. Here, we survey pores in one such species, Physocypria kraepelini. We choose 27 homologous pores as landmarks for 2D-geometric morphometric analysis, with the aim to assess intersexual and between valves variation in size and shape relative to the Fourier outline analysis. This species has only simple (Type A) pores with and without a lip, and each pore carries an undivided sensory seta. Our results show that the total number of pores varies (from 270 to 296), but this is not associated with a specific valve. Males carry fewer pores than females, however no sex specific pores are found. Small intrapopulation divergence of the Cyt b molecular marker (1%) indicates that morphological variability is not species related. We found that P. kraepelini exhibits directional asymmetry of size and shape, sexual size dimorphism (SSD) but lacks sexual shape dimorphism (SShD). Two geometric morphometrics methods were congruent in the estimation of SSD, SShD, and directional asymmetry of shape but differ in the statistical evaluation of directional asymmetry of size. Contrary to other animal groups, our study suggests that ostracods have more pronounced directional asymmetry of shape compared to directional asymmetry of size.

Distribution of haploniscids (Isopoda, Asellota, Haploniscidae) in Icelandic waters, with description of Haploniscus astraphes n. sp. from the Iceland basin and the Southeast Atlantic Ocean.

Ten species of Haploniscidae Hansen, 1916 were sampled in Icelandic waters during expeditions in the framework of the BIOICE project. Nine of these were known from the North Atlantic Ocean, i.e. Haploniscus aduncus Lincoln, 1985, H. ampliatus Lincoln, 1985, Haploniscus angustus Lincoln, 1985, H. bicuspis (Sars, 1877), H. foresti Chardy, 1974, H. hamatus Lincoln, 1985, H. spinifer Hansen, 1916, Antennuloniscus simplex Lincoln, 1985 and Chauliodoniscus armadilloides (Hansen, 1916). All but H. bicuspis and H. angustus were restricted to the Atlantic Ocean south of the Greenland-Iceland-Faeroe Ridge (GIF Ridge), while H. bicuspis occurred at considerable depth ranges both north and south of the GIF Ridge. A new species, Haploniscus astraphes n. sp., is described based on material from the Denmark Strait, North Atlantic and the Guinea Basin, South Atlantic. H. astraphes n. sp. belongs to a group of Haploniscus species closely related to the genus Antennuloniscus and shares several characters with species from that genus, especially the spine row on pleopod 1, the stout sensory seta on the carpus of pereopod 7 and characters of the antennae. H. astraphes n. sp. is characterized by a rectangular body shape, the straight frontal margin of the head and the strongly convex posterior margin of the pleotelson.

<i>Rugosuscandona</i>, a New Genus of Candonidae (Crustacea: Ostracoda) from Groundwater Habitats in Texas, North America

Rugosuscandona scharfi gen. nov. sp. nov. is described as a new genus of the family Candonidae from groundwaters of Texas, USA. The new genus differs from its congeners based on the presence of relatively long pore canals with sensory seta on the carapace surface, 6-segmented first antenna (A1), absence of bristles (t setae untransformed) and z setae on second antenna (A2), distinctly shaped male hemipenis and clasping organs, a simple claw-like uropod, and presence of 4+2 whorls on the Zenker's organ. Additionally, reduction in the number of setae and segments of the other soft body parts can be used to differentiate between the new genus Rugosuscandona gen. nov. and its congeners. Therefore, the new genus is currently monotypic. Taxonomic status of the new genus is discussed and compared with living genera of the family.