Setal morphology of grooming appendages in the spider crab,Libinia dubia

In crustaceans, grooming behaviors decrease fouling by removing debris from the exoskeleton and body structures; these grooming behaviors improve respiration, sensory reception, movement, and reproduction. Setal morphologies of the following grooming appendages in the decapod crustacean spider crab Libinia dubia are examined including the first pereiopod (cheliped), first, second, and third maxillipeds (mouthparts), and first, second, and third epipods (internal extensions of the maxillipeds). The objective of this study was to describe setal morphologies of these grooming appendages and to elucidate possible functions and efficiencies of setal structures. Spider crabs are hypothesized to have elaborate setal morphologies, mainly for cleaning specialized decorating setae as well as for cleaning inside the gill chamber, which has a higher likelihood of becoming fouled compared to other decapods such as shrimps. Fourteen setal types are documented and included several varieties of serrate and pappose setae as well as simple setae, cuspidate setae, papposerrate setae, and canoe setae. Maxillipodal epipods in the gill chamber are free of fouling, suggesting the setation on the third maxilliped protopod has an efficient functional morphology in removing debris before water enters the gill chamber. Serrate setae may function for detangling and separating structures whereas pappose setae may function for fine detailed grooming. The cheliped is the only grooming appendage that can reach decorating setae and it contains only pappose setae; thus decorating setae is not likely groomed in a manner that would greatly decrease fouling. J. Morphol. 277:1045–1061, 2016. © 2016 Wiley Periodicals, Inc.     

Setal morphology of the grooming appendages of Macrobrachium rosenbergii (Crustacea: Decapoda: Caridea: Palaemonidae) and review of decapod setal classification

Setae are vital in grooming activities and aiding in the removal of epibionts and sedimentary fouling from the body surfaces of decapod crustaceans. Thus, the setal structures and their arrangement on the grooming appendages and sensory structures of the commercially important shrimp, Macrobrachium rosenbergii, were examined using scanning electron microscopy. Macrobrachium rosenbergii is extensively grown in aquaculture and exhibits unique male morphological forms, termed morphotypes. The three male morphotypes are termed blue‐clawed males, orange‐clawed males, and small‐clawed or undifferentiated males and all three differ in their dominance, behavior, body morphology, and reproductive success. Seven setal types, two of which have never been described in the literature, are identified on the grooming appendages (third maxillipeds, first, second, and fifth pereopods) and antennae: simple, serrate, serrulate, spiniform, pappose, crinoid, and spinulate. The latter two setae are newly identified. Certain setal types, such as serrate and serrulate setae were located and associated with specific grooming appendages such as the first pereopods. The types of setae on the grooming appendages varied among females and male morphotypes and the novel setal types (crinoid and spinulate) were found only on two of the male morphotypes. A literature review of terminology related to the structure of setae and setal types in decapod crustaceans is offered as the usage of various terms is ambiguous and conflicting in the literature. The intention of this review is to provide future authors with a comprehensive collection of terms and images that can be used to describe various aspects of setal morphology in decapods. J. Morphol. 275:634–649, 2014. © 2014 Wiley Periodicals, Inc.     

The idiosomal chaetotaxy of astigmatid mites

Within the Astigmata, setal homologies with the general chaetotaxic systems developed for acariform mites by F. Grandjean have never been convincingly established. This study deals with all body regions, exclusive of legs and gnathosoma, mostly utilizing as models astigmatid species from three different families. Six hypotheses which attempt to explain the ontogeny of segments, setae and cupules in the caudal bend region are compared using three-dimensional views obtained by scanning electron microscopy. The hypotheses are evaluated by in-group comparisons testing their consistency with presumed segmental boundaries, and by out-group comparisons with oribatid mites. The strongest, most parsimonious hypothesis suggests that larval astigmatid mites possess segment F, but not its setae, and the two pairs posterior to segment F are h _l and h ₂, whilst the five setae added in the protonymph are h ₃, f ₂ and ps _1–3. Six pairs of structures on the deutonymphal anal plate are identified as modified setae, and evidence supporting their homologies with setae of other instars is discussed for the first time. A comparison of the principal chaetotaxic systems used for the dorsal and anal regions of the Astigmata is presented. Application of Grandjean's setal signatures to these regions, as well as to the coxisternal and genital regions, is discussed and illustrated by examples.     

Prey finding behavior and mechanosensilla of larval Toxorhynchites brevipalpis Theobald (Diptera : Culicidae)

Behavioral experiments demonstrated that starved 3rd-instar Toxorhynchites brevipalpis (Diptera : Culicidae) will attack a glass probe in response to vibrations alone. Frequencies in the range of 80–200 Hz elicited 85% of the attacks. The observation that most attacks occurred while the larva was drifting forward towards the probe, substantiates that the predatory behavior of these organisms is basically opportunistic.The main setae on the thorax and abdomen arise from setal support plates and are of 4 general morphological types: dendritic, smooth, spinulate spiniform, and unbranched aciculate setae. The numbers and lengths of the setae on 3rd- and 4th-instar larvae are given. Each seta is innervated by a bipolar neuron with a tubular body in the dendrite, a characteristic of mechanosensilla. By virtue of their abundance and location, it seems probable that one or more types of these setae sense the water vibrations capable of eliciting an attack response.The tubular bodies of the 4 types of setae are somewhat unusual in that they lack electron-dense material, except near sites of attachment of the microtubules to the dendritic membrane, yet possess a large number of complexly arranged microtubules. Among the setal types, variations were observed in the prominence of microtubular attachment sites, proportion of tubules associated with the sites, and orientation of microtubules. In spinulate spiniform setae, the arrangement of microtubules varies within the same tubular body; peripherally most of the microtubules are in one direction with little convergence and have only one distinct attachment site, whereas medially they converge considerably resulting in 2 groups, each associated with its own well-defined site.The attachment sites, which presumably through linkage with the dendritic membrane provide a means of initiating depolarization, are associated with the distal ends of almost all of the microtubules. This suggests that in these tubular bodies depolarization may be initiated through mechanical force acting along the length of the microtubules, that is, stretching and/or compression.     

Studies on Pogonophora. 4. Fine structure of the cuticle and epidermis

The fine structure of the integument in several species of Pogonophora has been examined by electron microscopy. The cuticle over the main body is composed of several layers of orthogonally arranged fibres embedded in an amorphous matrix. It is regularly traversed by microvilli from underlying epidermal cells. Toothed bristles of the annuli and setae of the anchor are composed of closely packed fibrous cylinders wrapped in a cortical material. In fine structure the cuticle, setae, toothed bristles (or setae) and setal sacs forming the setae closely resemble the corresponding structures in annelids. The cuticle is maximally thick over the forepart (protosome + mesosome) ; it is very thin and non-fibrous over the surface of the metameric papillae and over extensive areas of post-metameric trunk. The possibilities of a collagenous nature of the cuticle fibres and their mode of secretion by the epidermal cells are discussed. The organization of various cell-types forming the epidermis over the entire animal is examined. Possible functions of these cell-types are discussed. Notable amongst these are 'possible zymogen cells' and some absorptive cells. The intriguing question of nutrition in these gut-less tubiculous animals is re-examined in the light of present observations.     

Three new species of the subgenus Neoribates (Neoribates) (Acari,Oribatida, Parakalummidae) from Nepal

Three new parakalummid mites of the subgenus Neoribates (Neoribates), N. (N.) parabulanovae sp. n., N. (N.) paramacrosacculatus sp. n. and N. (N.) pararotundus sp. n., are described from Nepalese soils. Neoribates (Neoribates) parabulanovae sp. n. is morphologically most similar to N. (N.) bulanovae Grishina, 2009, N. (N.) rotundus Aoki, 1982 and N. (N.) setiger Balogh & Mahunka, 1978, however, it differs from N. (N.) bulanovae by the body length, body and leg integument, morphology of bothridial setae, absence of aggenital setae, length of interlamellar setae and location of adanal setae ad₃; from N. (N.) rotundus by the body size, body integument, morphology of bothridial setae and length of interlamellar setae; from N. (N.) setiger by the body size, number of genital setae and absence of aggenital setae. Neoribates (Neoribates) paramacrosacculatus sp. n. is morphologically most similar to N. (N.) macrosacculatus Aoki, 1966, however, it differs from the latter by the body size, body integument, length and morphology of bothridial setae, number of genital setae, absence of lamellar setae and length of interlamellar setae. Neoribates (Neoribates) pararotundus sp. n. is morphologically most similar to N. (N.) rotundus, however, it differs from the latter by the number of notogastral setal alveoli, body integument and length of interlamellar setae.     

Functional morphology of the muscles in Philodina sp. (Rotifera: Bdelloidea)

Whole-mounts of Philodina sp., a bdelloid rotifer, were stained with fluorescent-labeled phalloidin to visualize the musculature. Several different muscle types were identified including incomplete circular bands, coronal retractors and foot retractors. Based on the position of the larger muscle bands in the body wall, their function during creeping locomotion and tun formation was inferred. Bdelloid creeping begins with the contraction of incomplete circular muscle bands against the hydrostatic pseudocoel, resulting in an anterior elongation of the body. One or more sets of ventral longitudinal muscles then contract bringing the rostrum into contact with the substrate, where it presumably attaches via adhesive glands. Different sets of ventral longitudinal muscles, foot and trunk retractors, function to pull the body forward. These same longitudinal muscle sets are also used in `tun' formation, in which the head and foot are withdrawn into the body. Three sets of longitudinal muscles supply the head region (anterior head segments) and function in withdrawal of the corona and rostrum. Two additional pairs of longitudinal muscles function to retract the anterior trunk segments immediately behind the head, and approximately five sets of longitudinal retractors are involved in the withdrawal of the foot and posterior toes. To achieve a greater understanding of rotifer behavior, it is important to elucidate the structural complexity of body wall muscles in rotifers. The utility of fluorescently-labeled phalloidin for the visualization of these muscles is discussed and placed in the context of rotifer functional morphology.     

Fiber‐type composition in the perivertebral musculature of lizards: Implications for the evolution of the diapsid trunk muscles

The perivertebral musculature of lizards is critical for the stabilization and the mobilization of the trunk during locomotion. Some trunk muscles are also involved in ventilation. This dual function of trunk muscles in locomotion and ventilation leads to a biomechanical conflict in many lizards and constrains their ability to breathe while running (“axial constraint”) which likely is reflected by their high anaerobic scope. Furthermore, different foraging and predator‐escape strategies were shown to correlate with the metabolic profile of locomotor muscles in lizards. Because knowledge of muscle's fiber‐type composition may help to reveal a muscle's functional properties, we investigated the distribution pattern of muscle fiber types in the perivertebral musculature in two small lizard species with a generalized body shape and subjected to the axial constraint (Dipsosaurus dorsalis, Acanthodactylus maculatus) and one species that circumvents the axial constraint by means of gular pumping (Varanus exanthematicus). Additionally, these species differ in their predator‐escape and foraging behaviors. Using refined enzyme‐histochemical protocols, muscle fiber types were differentiated in serial cross‐sections through the trunk, maintaining the anatomical relationships between the skeleton and the musculature. The fiber composition in Dipsosaurus and Acanthodactylus showed a highly glycolytic profile, consistent with their intermittent locomotor style and reliance on anaerobic metabolism during activity. Because early representatives of diapsids resemble these two species in several postcranial characters, we suggest that this glycolytic profile represents the plesiomorphic condition for diapsids. In Varanus, we found a high proportion of oxidative fibers in all muscles, which is in accordance with its high aerobic scope and capability of sustained locomotion. J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.     

Morphology and distribution of setae on the antennules of the Caribbean spiny lobster Panulirus argus reveal new types of bimodal chemo-mechanosensilla

This study describes the morphology and distribution of setae on the lateral and medial flagella of the antennules of the spiny lobster Panulirus argus in an effort to identify antennular chemoreceptors in addition to the well-studied aesthetasc chemosensilla. Setae were examined using light and electron microscopy, and their distribution on flagellar annuli was analyzed. We identified ten setal types based on external morphology: hooded, plumose, short setuled, long simple, medium simple, short simple, aesthetasc, guard, companion, and asymmetric setae, with the last four types being unique to the "tuft" located on the distal half of the lateral flagellum. The three setal types whose ultrastructure was examined--hooded, long simple, and medium simple setae--had characteristics of bimodal (chemo-mechanoreceptive) sensilla. The antennules have four distinct annular types based on their setal complement, as shown by cluster analysis. This basic distribution of non-tuft setal types is similar for both lateral and medial flagella. Annuli in the tuft region have tuft setal types superimposed on a basic organization of non-tuft setal types. These results show that the antennules possess a diverse set of setae, that these setae have a highly ordered arrangement on the antennules, that at least four (and probably many more) of these setal types are chemosensilla, and suggest that most antennular chemosensilla are bimodally sensitive.     

Ultrastructure and development of forked and capillary setae in the polychaetes Orbinia bioreti and Orbinia latreillii (Annelida: Orbiniidae)

Abstract. Recent investigations into chaetogenesis of certain types of annelid setae provide important results for unravelling the phylogenetic relationships within several taxa of poly-chaetous annelids. This paper presents data on ultrastructure and development of 2 types of orbiniid setae. The analysis of the crenulate capillaries in Orbinia latreillii reveals a formation process which clearly differs from the development of Equisetum -like setae of lingulid bra-chiopods. For the investigation of forked setae, which up to now have been neglected in the discussion on the phylogenetic significance of annelid setae, notopodial setal sacs of O. latreillii and O. bioreti were studied by light- and electron microscopy. In the setal sacs, stages of forked setae are restricted to a dorsocaudal pouch, which represents the site of setal formation. The 2 diverging, stout tines of the fork bear spines on their inner margins, each of which is preformed by a single microvillus. After retraction of the microvilli, a characteristic pattern of the setal canals inside of the spines remains. The present study belongs to a series of comparative studies into chaetogenesis of forked setae. These special setae are also found in other orbiniid taxa as well as some paraonids, scalibregmatids, and nephtyids. Ultrastructural investigations into the development of these forked setae might suggest homology.     

Comparative morphology of the somatic musculature in species of Hexarthra and Polyarthra (Rotifera, Monogononta): Its function in appendage movement and escape behavior

Species of Hexarthra and Polyarthra are freshwater rotifers with well-known escape behaviors that result from interactions with planktonic predators. Both rotifers bear a suite of mobile appendages that function in evasive maneuvers and saltatory jumps through the water column, but the anatomical and functional bases of these actions are poorly understood. Here, we use a combination of phalloidin staining, confocal laser scanning microscopy, and video analysis to describe the morphology of the somatic muscles that supply the mobile appendages in order to understand how they function in escape behavior. Results show that species of Hexarthra, which bear six radially distributed limbs, possess a highly complex trunk musculature that supplies the inside of each limb with its own abductor and adductor muscles, i.e., a direct muscle supply. The singular dorsal and ventral limbs each receive a pair of large abductor and adductor muscles (four muscles total per limb), while the paired dorsolateral and ventrolateral limbs each receives three muscles (two abductors, one adductor per limb). Contraction of the abductor muscles creates a power stroke in the form of an anterior sweep of the limbs, which leads to a three-dimensional tumbling of the rotifer through the water column. Alternatively, species of Polyarthra possess 12 blade-like appendages that are arranged into four equal bundles; each bundle receives an indirect muscle supply that attaches to the shoulder of the paddles. A single longitudinal paddle muscle supplies each dorsolateral bundle, while a pair of longitudinal paddle muscles supplies each ventrolateral bundle. Contraction of these muscles, whether singly or in concert, functions to abduct the paddles in a power stroke, leading to rotation of the body and movement of the rotifer. The recovery stroke is hypothesized to be a multi-step process that begins with reorientation of the appendages prior to adduction, followed by contraction of various muscles to antagonize the paddle muscles. In total, these observations reveal novel complexities in the rotifer muscular system that aids our understanding of the biophysics of predator avoidance in appendage-bearing rotifers.     

The setae of Austropotamobius pallipes (Crustacea: Astacidae)

The author presents here the results of an introductory study into the setal armature of the British species of crayfish, Austropotamobius pallipes (Lereboullet, 1858). Using an ordinary optical microscope, it is demonstrated that a considerable variety of setae exist on the body and appendages of A. pallipes. These setae are described, and their distribution indicated. The setae fall into two main groups:
(1) Setae with relatively thick walls and inconspicuous ampulla, and having no basal septum.
(2) Those setae with relatively thin walls, a well-developed ampulla and basal septum. Further subdivisions of these two groups are made on the bases of outgrowths and outlines of the setal wall. Finally, the significance of the distribution and the variation, is discussed in relation to crayfish behaviour and function, linking the observed morphological facts with the results of some current electro-physiological experiments performed on related decapods.     

Neuromuscular development in Novocrania anomala: evidence for the presence of serotonin and a spiralian-like apical organ in lecithotrophic brachiopod larvae

SUMMARY The phylogenetic position of Brachiopoda remains unsettled, and only few recent data on brachiopod organogenesis are currently available. In order to contribute data to questions concerning brachiopod ontogeny and evolution we investigated nervous and muscle system development in the craniiform (inarticulate) brachiopod Novocrania anomala . Larvae of this species are lecithotrophic and have a bilobed body with three pairs of dorsal setal bundles that emerge from the posterior lobe. Fully developed larvae exhibit a network of setae pouch muscles as well as medioventral longitudinal and transversal muscles. After settlement, the anterior and posterior adductor muscles and delicate mantle retractor muscles begin to form. Comparison of the larval muscular system of Novocrania anomala with that of rhynchonelliform (articulate) brachiopod larvae shows that the former has a much simpler muscular organization. The first signal of serotonin-like immunoreactivity appears in fully developed Novocrania anomala larvae, which have an apical organ that consists of four flask-shaped cells and two ventral neurites. These ventral neurites do not stain positively for the axonal marker α-tubulin in the larval stages. In the juveniles, the nervous system stained by α-tubulin is characterized by two ventral neurite bundles with three commissures. Our data are the first direct proof for the presence of an immunoreactive neurotransmitter in lecithotrophic brachiopod larvae and demonstrate the existence of flask-shaped serotonergic cells in the brachiopod larval apical organ, thus significantly increasing the probability that this cell type was part of the bauplan of the larvae of the last common lophotrochozoan ancestor.     

Inonotus taiwanensis sp. nov. (Basidiomycota) from Taiwan

Inonotus taiwanensis (Hymenochaetales) is described as a new species collected from southern Taiwan, and all specimens grew on the trunk of Trema tomentosa. This new species is characterized by having resupinate, effuse-reflexed to pileate basidiocarps, bright yellow context, long setal hyphae in context and trama, setae in hymenium and trama, and fairly small basidiospores. Maximum likelihood and Bayesian inference phylogenies inferred from both sequences of 28S and internal transcribed spacer (ITS) region of rDNA indicated that I. taiwanensis forms a distinct clade within Inonotus, and the species is sister to I. tricolor. The comparison of morphological differences among I. taiwanensis and some closely related Inonotus spp. is presented.     

Surface structures of the antennular flagella of the hermit crab Pagurus alaskensis (Benedict): A light and scanning electron microscopy study

The surface structures of the antennular flagella of Pagurus alaskensis are described in detail. Attention is directed towards the surface morphology of two types of possible sensilla: (1) exoskeletal pores (1.0–3.0 μm in diameter); (2) setae of various kinds. In addition, small (0.1–0.2 μm) pits occur in the exoskeleton which are not considered to be sensory in function. The exoskeletal pores are found at fairly specific locations on both the inner and outer flagella, particularly on the short segments of the outer flagella. Neither the inner nor the outer flagella are bilaterally symmetrical with respect to their setal armature. On the outer flagellum six groups of setae may be distinguished: lateralmesial; dorsal; ventral; accessory; aesthetasc; setae of the distal segment. On the inner flagellum setae of the mesial and lateral rows form distinctive groups. The morphology, orientation and locations of all the flagellar setae are defined and where possible the numbers of the various morphological types within the specific setal groups are given. It is noteworthy that many setal types have obvious apical pores and yet no pores could be found in the chemoreceptive aesthetasc setae. The functions of the various setae are discussed in relation to their topographical position and to existing electrophysiological and behavioral data. Some suggestions are made about future experiments to demonstrate the central connections of specific sensilla or groups of sensilla and to show their significance in the whole animal.     

Ultrastructure of mediodorsal setae in biting midge larvae of the genus Atrichopogon Kieffer with notes on their biological significance (Diptera: Ceratopogonidae)

The ultrastructure of the strong mediodorsal setae in terrestrial stage IV larvae of Atrichopogon (Meloehelea) oedemerarum and A. (M.) meloesugans was examined using light, scanning and transmission electron microscopy. Serrated setae placed on prominent processes are distributed in pairs on all thoracic and abdominal segments. Setae are innervated by a single dendrite and their surface has no pores. The trichogen cell is not retracted from the setal lumen on completion of the hair-forming process but fills the mediodorsal seta also when the larval cuticle is fully sclerotised. Such a phenomenon was previously reported in terrestrial larvae of the genus Forcipomyia. We suggest that the mediodorsal setae described in Atrichopogon are plesiotypic mechanoreceptors for the subfamily Forcipomyiinae. They are preserved in the truly terrestrial larvae of Atrichopogon, but modified to secretory setae in the genus Forcipomyia. Both genera bearing distinct mediodorsal setae have developed functional tracheal gills, unknown in other biting midges.     

Response of the trunk muscles to training assessed by magnetic resonance imaging and muscle strength.

A group of 12 sedentary medical students (1 man and 11 women aged 21-27 years) participated in a strength training programme for the trunk muscles lasting 18 weeks. The maximal isometric flexion and extension forces of the trunk muscles were measured before the training and at 18 weeks by dynamometer. The cross-sectional area of the back muscles, i.e. erector spinae, multifidus and psoas muscles, was measured from magnetic resonance images (spin echo sequence TR/TE 1500/80, slice thickness 10 mm) obtained at the L4-L5 disc level before the training, at 11 and 18 weeks. During training, no significant change in the body mass or body fat content was found. Muscle forces or muscle cross-sectional area were not related to body mass. There was a significant increase in both trunk muscle cross-sectional area (psoas muscle P < 0.001 and back muscles P < 0.01) and trunk muscle forces (flexion and extension forces P < 0.01) during the training but no direct association between the muscle cross-sectional area and strength of the flexors and extensors was detected before or after the training.     

Behaviour, Setal Inversion and Phylogeny of Sabellida (Polychaeta)

The path taken by the faecal groove, following two right angle bends, appears inefficient in Sabellidae. It fits well with the thoracic folds of serpulids and follows a gentle spiral in caobangiids, but only in spirorbids is it of obvious adaptive value, being suited to life in a coiled tube. The associated setal inversion is not necessary for locomotion, which does not depend wholly on setal leverage, except in the smaller Fabriciinae where long-shafted uncini also thrust actively against the elastic tube wall. The collar setae of spirorbids and some serpulids thrust anteriorly, giving some backward movement, but such motion is mainly by body contraction. Short uncini are virtually passive, engaged by opposing setae acting as distance pieces. Some broad bladed setae have a hollow structure around a central core. Pick-axe setae of Sabellinae may have developed to counteract the thrust of respiratory peristalsis. This is not seen in spirorbids and serpulids, the thoracic folds of which are a sufficient respiratory supplement to the tentacles. — Numbers of thoracic segments in Sabellidae range from 1 to 16, and the abdomen becomes vestigial in some Fabriciinae. Abdominal inversion is important to spirorbids but not to sabellids, which are more varied. It seems that the former are archaic and the latter had a coiled ancestry. Sabellariids also show abdominal inversion suggesting a distant relationship with Sabellida.