Observations on torquaratorid acorn worms (Hemichordata,Enteropneusta) from the North Atlantic with descriptions of a new genus and three new species

Enteropneusts in the family Torquaratoridae were imaged using still and video cameras in the deep North Atlantic and then collected by remotely operated vehicles. From this material, we describe Yoda purpurata n. gen, n. sp., Tergivelum cinnabarinum n. sp., and Allapasus isidis n. sp. Individuals of the first two species were browsing completely exposed on the sea floor, whereas the specimen of the last species was encountered floating ~1 m above the sea floor. Living specimens of Y. purpurata were 12–19 cm long and had a dark reddish‐purple proboscis, collar, and genital wings (folded dorsally over the anterior region of the trunk). Members of this species were hermaphrodites (the first ever discovered in the phylum Hemichordata), with numerous separate testes and ovaries in the genital wings. Living specimens of T. cinnabarinum were 12–26 cm long and had a cinnabar‐colored proboscis, collar, and back veils (arising from the anterior region of the trunk); sexes were separate, and body shape and internal morphology closely resemble those of its brown congener, T. baldwinae, from the eastern Pacific. The only specimen of A. isidis collected was a male 13 cm long and pale yellow when alive. Its body shape was proportionally shorter and broader than that of its orange congener, A. aurantiacus, from the eastern Pacific, but the internal anatomy of the two species is virtually identical. [Correction made after online publication August 21, 2012 to correct species name in preceding sentence.]     

Adaptations for nectar‐feeding in the mouthparts of long‐proboscid flies (Nemestrinidae: Prosoeca)

The insects with the longest proboscis in relation to body length are the nectar‐feeding Nemestrinidae. These flies represent important pollinators of the South African flora and feature adaptations to particularly long‐tubed flowers. The present study examined the morphology of the extremely long and slender mouthparts of Nemestrinidae for the first time. The heavily sclerotized tubular proboscis of flies from the genus Prosoeca is highly variable in length. It measures 20–47 mm in length and may exceed double the body length in some individuals. Proximally, the proboscis consists of the labrum–epipharynx unit, the laciniae, the hypopharynx, and the labium. The distal half is composed of the prementum of the labium, which solely forms the food tube. In adaptation to long‐tubed and narrow flowers, the prementum is extremely elongated, bearing the short apical labella that appear only to be able to spread apart slightly during nectar uptake. Moving the proboscis from resting position under the body to a vertical feeding position is accomplished in particular by the movements of the laciniae, which function as a lever arm. Comparisons with the mouthparts of other flower visiting flies provide insights into adaptations to nectar‐feeding from long‐tubed flowers. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Brief communication: Three‐dimensional motion analysis of hindlimb during brachiation in a white‐handed gibbon (Hylobates lar)

In brachiating gibbons, it is thought that there is little movement in the hindlimb joints and that lateral body movement is quite limited. These hypotheses are based on naked‐eye observations, and no quantitative motion analyses of the hindlimbs have been reported. This study quantitatively describes the three‐dimensional movements of the lower trunk and distal thigh during continuous‐contact brachiation in a white‐handed gibbon (Hylobates lar) to evaluate the roles of the trunk and hindlimb. The results revealed that the lower trunk moved both laterally and vertically. The lateral movement of the lower trunk resulted from the lateral inclination of the trunk by gravity. The vertical movement of the trunk was converted into forward velocity, indicating an exchange between potential and kinetic energy. We also observed flexion and extension of the hip, although the excursion was within a small range. In addition, the lateral movement of the hindlimb in thedirection opposite to that of trunk movement helped to reduce the lateral sway of the body. These results suggest that during continuous‐contact brachiation a gibbon uses hip flexion and extension motions to increase the kinetic energy in the swing. In addition, fine motions of the hip may restrict the lateral sway of the center of body mass. Am J Phys Anthropol 142:650–654, 2010. © 2010 Wiley‐Liss, Inc.     

New material of the oldest known scalidophoran animal Eopriapulites sphinx

Eopriapulites sphinx is the oldest known scalidophoran animal and so far the only cycloneuralian body fossil from the Cambrian Fortunian Stage. The hexaradial symmetry exhibited by the arrangement of its pharyngeal teeth, coronal scalids and introvert scalids expand our knowledge on the early evolution of cycloneuralians. The holotype and only specimen is a fragment with the proboscis and the anterior trunk part preserved, but the posterior trunk part is missing. Here, we report three-dimensionally phosphatized worm trunk fragments from the same locality and horizon yielding E. sphinx. They are regarded as conspecific with E. sphinx based on co-occurrence and identical annulations, and provide key information on the trunk morphology. E. sphinx is completely reconstructed here as a long vermiform animal with densely annulated trunk and no caudal outgrowths. An updated phylogenetic analysis supports that E. sphinx is a stem-lineage derivative of Scalidophora and also indicates that the hexaradial symmetry of Eopriapulites might have evolved independently from that of Nematoida.     

Fiber‐type distribution of the perivertebral musculature in Ambystoma

Many salamanders locomote in aquatic and terrestrial environments. During swimming, body propulsion is solely produced by the axial musculature generating lateral undulations of the trunk and tail. During terrestrial locomotion, the trunk is oscillated laterally in a standing wave, and body propulsion is achieved by concerted trunk and limb muscle action. The goal of this study was to increase our knowledge of the functional morphology of the tetrapod trunk. We investigated the muscle‐fiber‐type distribution and the anatomical cross‐sectional area of all perivertebral muscles in Ambystoma tigrinum and A. maculatum. Muscle‐fiber‐type composition was determined in serial cross‐sections based on m‐ATPase activity. Five different body segments were investigated to test for cranio‐caudal changes along the trunk. The overall fiber‐type distribution was very similar between the species, but A. tigrinum had relatively larger muscles than A. maculatum, which may be related to its digging behavior. None of the perivertebral muscles possessed a homogeneous fiber‐type composition. The M. interspinalis showed a distinct layered organization and may function to ensure the integrity of the spine (local stabilization). The M. dorsalis trunci exhibited the plesiomorphic pattern for notochordates in having a distinct superficial layer of red and intermediate fibers, which covered the central white fibers; therefore, it is suggested to function as a mobilizer and a stabilizer of the trunk, but, may also be involved in modulating body stiffness. Similarly, the M. subvertebralis showed clear regionalizations, implying functional subunits that can stabilize and mobilize the trunk as well as modulate of body stiffness. Cranio‐caudally, neither the fiber‐type composition nor the a‐csa changed dramatically, possibly reflecting the need to perform well in both aquatic and terrestrial habitats. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.     

Proximal fate marker homothorax marks the lateral extension of stalk‐eyed fly Cyrtodopsis whitei

The placement of eyes on insect head is an important evolutionary trait. The stalk‐eyed fly, Cyrtodopsis whitei, exhibits a hypercephaly phenotype where compound eyes are located on lateral extension from the head while the antennal segments are placed inwardly on this stalk. This stalk‐eyed phenotype is characteristic of the family Diopsidae in the Diptera order and dramatically deviates from other dipterans, such as Drosophila. Like other insects, the adult eye and antenna of stalk‐eyed fly develop from a complex eye‐antennal imaginal disc. We analyzed the markers involved in proximo‐distal (PD) axis of the developing eye imaginal disc of the stalk‐eyed flies. We used homothorax (hth) and distalless (dll), two highly conserved genes as the marker for proximal and distal fate, respectively. We found that lateral extensions between eye and antennal field of the stalk‐eyed fly's eye‐antennal imaginal disc exhibit robust Hth expression. Hth marks the head specific fate in the eye‐ and proximal fate in the antenna‐disc. Thus, the proximal fate marker Hth expression evolves in the stalk‐eyed flies to generate lateral extensions for the placement of the eye on the head. Moreover, during pupal eye metamorphosis, the lateral extension folds back on itself to place the antenna inside and the adult compound eye on the distal tip. Interestingly, the compound eye in other insects does not have a prominent PD axis as observed in the stalk‐eyed fly.     

The anatomy, life habits, and later development of a new species of enteropneust, Harrimania planktophilus (Hemichordata: Harrimaniidae) from Barkley Sound

A new species of enteropneust, Harrimania planktophilus, lives intertidally and subtidally in mixed sediments in Barkley Sound, British Columbia, Canada. H. planktophilus has a long proboscis skeleton extending into the pharyngeal region. The collar (mesosome) has complete dorsal and ventral mesenteries. The trunk (metasome) has four distinct regions that can be recognized externally: the branchial region, esophageal region, hepatic region, and an undifferentiated intestinal region leading to the anus. The dorsal pharynx is large and has long gill slits without synapticles. Posterior to the gills is a constriction followed by a short esophageal region and a long gonadal region. The paired dorsolateral gonads extend almost to the end of the trunk. Eggs in the ovaries appear amber yellow, and the testes appear slightly paler. The trunk terminates at an anus with a well-developed sphincter muscle. H. planktophilus forms long sinuous burrows that are semipermanent and shared. Females deposit a tubular egg mass in a burrow in which the embryos develop directly into juveniles. Gastrulation appears to be by invagination, followed by a ciliated stage that has a telotrochal swimming band, suggesting that the ancestor to H. planktophilus developed via a tornaria larva. The juveniles emerge from the egg membrane with a ventral post-anal tail and assume an interstitial burrowing life habit. The post-anal tail, mode of development, small size and correlated simplification in body plan suggest that H. planktophilus is closely related to Saccoglossus, and together these worms may be sister taxa to the colonial Pterobranchia. A taxonomic key is provided to the enteropneust genera, and to the species of Harrimania:     

Finding the neck–trunk boundary in snakes: Anteroposterior dissociation of myological characteristics in snakes and its implications for their neck and trunk body regionalization

The neck and trunk regionalization of the presacral musculoskeletal system in snakes and other limb‐reduced squamates was assessed based on observations on craniovertebral and body wall muscles. It was confirmed that myological features characterizing the neck in quadrupedal squamates (i.e., squamates with well‐developed limbs) are retained in all examined snakes, contradicting the complete lack of the neck in snakes hypothesized in previous studies. However, the posterior‐most origins of the craniovertebral muscles and the anterior‐most bony attachments of the body wall muscles that are located at around the neck–trunk boundary in quadrupedal squamates were found to be dissociated anteroposteriorly in snakes. Together with results of a recent study that the anterior expression boundaries of Hox genes coinciding with the neck–trunk boundary in quadrupedal amniotes were dissociated anteroposteriorly in a colubrid snake, these observations support the hypothesis that structures usually associated with the neck–trunk boundary in quadrupedal squamates are displaced relative to one another in snakes. Whereas certain craniovertebral muscles are elongated in some snakes, results of optimization on an ophidian cladogram show that the most recent common ancestor of extant snakes would have had the longest craniovertebral muscle, M. rectus capitis anterior, that is elongated only by several segments compared with that of quadrupedal squamates. Therefore, even such a posteriorly displaced “cervical” characteristic plesiomorphically lies fairly anteriorly in the greatly elongated precloacal region of snakes, suggesting that the trunk, not the neck, would have contributed most to the elongation of the snake precloacal region. A similar dissociation of structures usually associated with the neck–trunk boundary in quadrupedal squamates is observed in limb‐reduced squamates, suggesting that these forms and snakes may share a developmental mechanism producing modifications in the anterior–posterior patterning associated with body elongation. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

Acanthocephalus?amini n. sp. (Acanthocephala: Echinorhynchidae) from the freshwater fish Cichlasoma?urophthalmus (Günther) (Cichlidae) in Mexico

Acanthocephalus amini n. sp. (Palaeacanthocephala: Echinorhynchidae) is described from the intestine of Cichlasoma urophthalmus (Günther) (Pisces: Cichlidae) collected in the Río Champotón, a river in Campeche State, Mexico. It is the fourth species of Acanthocephalus Koelreuther, 1771 described from North American freshwater fishes, although two other species are known from South America. The new species is distinguished from other members of Acanthocephalus by features of its trunk, which is small, clavate, slightly expanded medially and bluntly pointed posteriorly. It is further distinguished by having a cylindrical proboscis armed with 13–14 longitudinal rows of 11–12 stout hooks; the apical and medial proboscis hooks are almost uniform in size and shape, decreasing in size towards the base; the posteriormost hooks are smaller, straighter and more slender than the anterior and middle hooks; and the lateral rows of hooks are more widely spaced, forming a conspicuous longitudinal area devoid of hooks. Furthermore, the lemnisci are saccate and shorter than the proboscis receptacle; and the neck is very short with a thick collar of trunk tegument, which encircles the base of proboscis. In males, the testes are in the middle third of trunk, diagonal, spherical and small relative to the body size, and there are six clavate cement glands. In females, the uterus forms a conspicuous, elongate, cylindrical egg reservoir. The new species is most similar to A. alabamensis Amin & Williams, 1983, but can be distinguished by its swollen, clavate trunk, the largest proboscis hooks being present apically and medially, smaller testes, a shorter male reproductive system relative to body size and females with a prominent uterus. They have different hosts and geographical distribution. The new species can be differentiated from Brasacanthus sphoeroides Thatcher, 2001, a similar species in a monotypic echinorhynchid genus, because the latter is larger, has smaller proboscis hooks and its lemnisci are longer than the receptacle.     

Co‐ordinate synthesis and protein localization in a bacterial organelle by the action of a penicillin‐binding‐protein

Organelles with specialized form and function occur in diverse bacteria. Within the Alphaproteobacteria, several species extrude thin cellular appendages known as stalks, which function in nutrient uptake, buoyancy and reproduction. Consistent with their specialization, stalks maintain a unique molecular composition compared with the cell body, but how this is achieved remains to be fully elucidated. Here we dissect the mechanism of localization of StpX, a stalk‐specific protein in Caulobacter crescentus. Using a forward genetics approach, we identify a penicillin‐binding‐protein, PbpC, which is required for the localization of StpX in the stalk. We show that PbpC acts at the stalked cell pole to anchor StpX to rigid components of the outer membrane of the elongating stalk, concurrent with stalk synthesis. Stalk‐localized StpX in turn functions in cellular responses to copper and zinc, suggesting that the stalk may contribute to metal homeostasis in Caulobacter. Together, these results identify a novel role for a penicillin‐binding‐protein in compartmentalizing a bacterial organelle it itself helps create, raising the possibility that cell wall‐synthetic enzymes may broadly serve not only to synthesize the diverse shapes of bacteria, but also to functionalize them at the molecular level.     

Skeletal anatomy of the extinct shark Paraorthacodus jurensis (Chondrichthyes; Palaeospinacidae), with comments on synechodontiform and palaeospinacid monophyly

The skeletal morphology of Paraorthacodus jurensis, a Late Jurassic neoselachian from Nusplingen, is described based on the incomplete holotype and a newly discovered almost complete specimen. For the first time, the postcranial skeleton could be investigated. Paraorthacodus is characterized by a monognath dental heterodonty and tearing‐type dentition. The number of lateral cusplets in the lateral teeth differs between the holotype and the new specimen, possibly indicating sexual dimorphism. Clasper organs are not preserved in either of the two specimens. The notochord is sheathed by about 123 well‐calcified vertebral centra. The posterior‐most caudal vertebrae are lacking. The transition from monospondylous thoracic to diplospondylous abdominal vertebrae occurs at centra 48 and 49. The origin of the caudal fin is at the 80th centrum. Most conspicuous is the presence of a single spineless dorsal fin. In this respect, Paraorthacodus differs from most palaeospinacids, but resembles Macrourogaleus. Palidiplospinax possibly is sister to a group comprising Synechodus, Paraorthacodus, and Macrourogaleus (the Palaeospinacidae). A reinterpretation of dental and skeletal characters of synechodontiform taxa indicates that Synechodontiformes and Palaeospinacidae are monophyletic groupings of basal neoselachians. Synechodontiformes is probably sister to all living elasmobranchs.     

Comparing wing loading,flight muscle and lipid content in ant‐attended and non‐attended Tuberculatus aphid species

Although all Tuberculatus aphids possess wings, some species associated with ants exhibit extremely low levels of dispersal compared with those not associated with ants. Furthermore, phylogenetic interspecific comparisons find significantly higher wing loading (i.e. higher ratio of body volume to wing area) in ant‐attended species. This observation indicates that ant‐attended species may allocate more of their body resources to reproductive traits (i.e. embryos) rather than flight apparatus (i.e. wings, flight muscle and lipid). The present study focuses on two sympatric aphid species and aims to investigate the hypothesized trade‐off in resource investment between fecundity and the flight apparatus; specifically, the ant‐attended Tuberculatus quercicola (Matsumura) and non‐attended Tuberculatus paiki Hille Ris Lambers. Species differences are compared in: (i) morphology, (ii) embryo production, (iii) triacylglycerol levels and (iv) wing loading and flight muscle. The results show that T. quercicola has a larger body volume, higher fecundity and higher wing loading compared with T. paiki, which has a smaller, slender‐shaped body, lower fecundity and lower wing loading. No significant difference is found between the species with respect to the percentage of triacylglycerol content in dry body weight. The flight muscle development is significantly lower in T. quercicola than in T. paiki. These results indicate that the additive effect of higher wing loading and the lower amount of flight muscle development in T. quercicola may increase the physical difficulty of flight, and hence be responsible for its lower dispersal ability. The trade‐off between fecundity and dispersal documented in wing‐dimorphic insects may therefore be applicable to T. quercicola, which has fully developed wings.     

Opisoma excavatum Boehm,a Lower Jurassic photosymbiotic alatoform‐chambered bivalve

Alatoform bivalves are a polyphyletic group characterized by antero‐posteriorly compressed shells and a ventro‐lateral wing originating from a tight fold of the shell wall. This bizarre shell morphology is interpreted as an adaptation for algal photosymbiosis in heliophilous bivalves. The group contains the living heart cockle Corculum together with four extinct genera ranging in age from the Permian to the Jurassic. The Jurassic alatoform bivalve is Opisoma, which has an aragonitic shell that is divided into two regions, both with different functions: one for stabilization, the other for hosting symbionts. The dorsal part of the shell is massive and played the stabilization role. The ventral part has a very thin and fragile shell that permitted the transmission of light into the internal tissues harbouring photosymbionts. The morphology of this delicate ventral part has thus far remained obscure, due to lack of preservation. Accumulations of Opisoma excavatum Boehm with exquisitely preserved shells containing the fragile winged ventral parts are common within the Pliensbachian shallow‐water, lagoonal carbonate succession of the Rotzo Formation of northern Italy. The wings have internal curved chambers limited by septa parallel to the wing edge. The shell of the ventral part consists of irregular fibrous prismatic and homogeneous structures which progressively infill the chambers. As the chambered wings are analogous structures among alatoform bivalves, they are no longer considered a taxonomic character. According to the observed shell orientation in the field and the consequent organization of the soft parts, Opisoma had an opisthogyrate shell.     

Saccoglossus testa from the Mazon Creek fauna (Pennsylvanian of Illinois) and the evolution of acorn worms (Enteropneusta: Hemichordata)

The limited fossil record of enteropneust hemichordates (acorn worms) and the few external features that distinguish the four families have provided a challenge to our understanding of the evolution of the group and their various feeding adaptations. The middle Pennsylvanian Saccoglossus testa sp. nov. from the Mazon Creek, Westfalian D Carbonate Formation, Francis Creek Shale of northern Illinois provides evidence for the exploitation of surface sediments. Saccoglossus testa has a long proboscis characteristic of the extant genus Saccoglossus, a specialist in surface deposit feeding. The collar is as long as it is wide. The anterior trunk lacks a distinctively wide branchial region. These three features distinguish it from its sympatric enteropneust species Mazoglossus ramsdelli Bardack that has a proboscis characteristic of an infaunal deposit feeder. It is the seventh known species of fossil enteropneust, including a resting trace of a Lower Triassic fossil that has collar lips that characterize the extant deep‐sea family Torquaratoridae, and which represents a second parallel evolution of surface deposit feeding. An analysis of the seven fossils shows that the earliest Enteropneusta had a relatively simple harrimaniid‐like body plan, and that the spengelid, the torquaratorid and lastly the most complex ptychoderid body plan appeared in that chronological order.     

Organisation of the praesoma in Acanthocephalus anguillae (Acanthocephala, Palaeacanthocephala) with special reference to the muscular system

The organisation of the praesoma in the parasite Acanthocephalus anguillae was studied on the light and electron microscopic level, with emphasis on the morphology of the musculature. The study was compiled to add new data to the ground pattern of the Acanthocephala for analysis of the phylogenetic relationships within the Gnathifera. In A. anguillae the praesomal epidermis and lemnisci form a coherent syncytium, separated from the epidermis of the trunk. Hooks are seen to be derivatives of the subepidermal basal lamina and are covered by the praesomal epidermis. The praesomal circular body wall musculature forms a network of anastomosing muscle fibres that lines the proboscis; a praesomal longitudinal body wall musculature does not exist. The truncal circular and longitudinal body wall musculature rise up to the praesomal proboscis. The unpaired proboscis retractor, consisting of longitudinal circomyar fibres, forms an outer and an inner concentric tube; the latter extends through the entire praesoma and penetrates the receptacle wall. The sack-like receptacle is surrounded by a receptacle constrictor. The nervous system of the praesoma consists of a prominent cerebral ganglion, three nerves which extend anteriorly, ramify and end within the praesomal musculature, and two strong lateral posterior nerves. A. anguillae lacks an apical organ, lateral organs and a support cell. Many of the features present in the praesoma of A. anguillae can be assumed as ground-pattern characteristics of the Acanthocephala. Accepted: 22 January 2001     

VALVE MORPHOGENESIS IN THE CENTRIC DIATOM PROBOSCIA ALATA SUNDSTROM1

Valve morphogenesis in Proboscia alata Sundstrom was followed in living cells and during treatment with antiactin and antimicrotubule drugs. Once cleaved, sibling cells rounded up and retracted. Soon, a granular organizing center (OC) appeared adjacent to the stub of the initiated valve. Silicification started within a silicon deposition vesicle (SDV) adjacent to the OC. The elongating valve was initially tubular and sealed at one end, creating the proboscis of the conical valve. The edge of the SDV and thinnest region of the forming valve was lined by a sleeve of bundled microtubules (MTs) that terminated short of the older more rigid part of the valve. The growing proboscis of living cells treated with the anti‐MT drug oryzalin became grossly distorted. EM revealed dense material lining the growing edge of the SDV; immunofluorescence microscopy showed a ring of actin here. Applied to living cells, the antiactin drug cytochalasin D caused the very young proboscis to collapse; in older valves, the base of the proboscis expanded. Thus, valve morphogenesis appeared controlled by the MT cytoskeleton, keeping the proboscis straight while actin molded its conical outline. At the tip of the proboscis was a slit resembling a labiate process. Its morphogenesis involved striated fibers and two MTs, reminiscent of the fibers and MTs associated with raphe morphogenesis. In contrast to spine‐like processes that elongate by tip growth, the tip of the proboscis was formed first, and the consequent “antitip growth” suggests the tip was originally the center of the valve face.     

Segment number,body length,and latitude in geophilomorph centipedes: a ‘converse‐Bergmann’ pattern

There is a negative relationship between trunk segment number and latitude among geophilomorph centipedes in general. A similar relationship is known to exist within the most intensively‐studied geophilomorph species, Strigamia maritima, and also within several other species from this group. Previously, it was considered that this relationship did not involve body length; instead, individuals of S. maritima with more segments were considered to be more finely subdivided (not longer) than those with fewer segments. This incorrect interpretation arose from the difficulty of reliably separating post‐embryonic stages and thus of making a simple and direct comparison. In the present study, we build on recent work that facilitates such comparisons; and we show conclusively that individuals with more segments are longer. Our finding means that it is now possible to connect the work on S. maritima in particular, and on geophilomorph centipedes in general, with the debate about Bergmann's ‘rule’: the proposal that body size increases with increasing latitude. There is a clear ‘converse‐Bergmann’ pattern, as has been found in several other taxa. We propose an adaptive hypothesis that may explain why geophilomorphs show this pattern. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Morphology and ontogeny of multiple lateral‐line canals in the rock prickleback,Xiphister mucosus (Cottiformes: Zoarcoidei: Stichaeidae)

The structure and ontogeny of lateral‐line canals in the Rock Prickleback, Xiphister mucosus, were studied using cleared‐and‐stained specimens, and the distribution and morphology of neuromasts within lateral‐line canals were examined using histology. X. mucosus has seven cephalic canals in a pattern that, aside from four branches of the infraorbital canals, is similar to that of most teleostean fishes. Unlike most other teleosts, however, X. mucosus features multiple trunk lateral‐line canals. These include a short median posterior extension of the supratemporal canal and three paired, branching canals located on the dorsolateral, mediolateral, and ventrolateral surfaces. The ventrolateral canal (VLC) includes a loop across the ventral surface of the abdomen. All trunk canals, as well as the branches of the infraorbitals, are supported by small, dermal, ring‐like ossifications that develop independently from scales. Trunk canals develop asynchronously with the mediodorsal and dorsolateral canals (DLC) developing earliest, followed by the VLC, and, finally, by the mediolateral canal (MLC). Only the mediodorsal and DLC connect to the cephalic sensory canals. Fractal analysis shows that the complexity of the trunk lateral‐line canals stabilizes when all trunk canals develop and begin to branch. Histological sections show that neuromasts are present in all cephalic canals and in the DLC and MLC of the trunk. However, no neuromasts were identified in the VLC or its abdominal loop. The VLC cannot, therefore, directly function as a part of the mechanosensory system in X. mucosus. The evolution and functional role of multiple lateral‐line canals are discussed. J. Morphol. 276:1218–1229, 2015. © 2015 Wiley Periodicals, Inc.     

Proboscis musculature in the butterfly Vanessa cardui (Nymphalidae, Lepidoptera): settling the proboscis recoiling controversy

Krenn, H. W. 2000. Proboscis musculature in the butterfly Vanessa cardui (Nymphalidae, Lepidoptera): settling the proboscis recoiling controversy. —Acta Zoologica (Stockholm) 81 : 259–266 The proboscis of Vanessa cardui (Nymphalidae) contains two basal galeal muscles and two different series of numerous oblique muscles. Both muscle series extend from the proximal region up to the tip‐region; the individual muscles of each series run a constant course throughout the proboscis. In contrast to other butterflies, the knee bend region does not have additional types of muscles. The analysis of shock‐frozen proboscises reveals that the dorsal wall is arched outwardly in the uncoiled, feeding position whereas in the coiled, resting position the dorsal proboscis wall is flat or concave. This results in a significantly greater cross‐sectional area due to the significantly greater dorso‐ventral diameter in uncoiled proboscises. After freezing the proboscis in its distal region, it can still be uncoiled, however, it cannot be fully recoiled. These morphometric and experimental results indicate that the oblique proboscis muscles are responsible for recoiling the proboscis to the resting position.     

Onychophoran‐like myoanatomy of the Cambrian gilled lobopodian Pambdelurion whittingtoni

Arthropods are characterized by a rigid, articulating, exoskeleton operated by a lever‐like system of segmentally arranged, antagonistic muscles. This skeletomuscular system evolved from an unsegmented body wall musculature acting on a hydrostatic skeleton, similar to that of the arthropods’ close relatives, the soft‐bodied onychophorans. Unfortunately, fossil evidence documenting this transition is scarce. Exceptionally‐preserved panarthropods from the Cambrian Lagerstätte of Sirius Passet, Greenland, including the soft‐bodied stem‐arthropod Pambdelurion whittingtoni and the hard‐bodied arthropods Kiisortoqia soperi and Campanamuta mantonae, are unique in preserving extensive musculature. Here we show that Pambdelurion's myoanatomy conforms closely to that of extant onychophorans, with unsegmented dorsal, ventral and longitudinal muscle groups in the trunk, and extrinsic and intrinsic muscles controlling the legs. Pambdelurion also possesses oblique musculature, which has previously been interpreted as an arthropodan characteristic. However, this oblique musculature appears to be confined to the cephalic region and first few body segments, and does not represent a shift towards arthropodan myoanatomy. The Sirius Passet arthropods, Kiisortoqia and Campanamuta, also possess large longitudinal muscles in the trunk, although, unlike Pambdelurion, they are segmentally divided at the tergal boundaries. Thus, the transition towards an arthropodan myoanatomy from a lobopodian ancestor probably involved the division of the peripheral longitudinal muscle into segmented units.