The blood system of the flabelligerid polychaete Flabelliderma commensalis (Moore)

The blood system of the flabelligerid polychaete, Flabelliderma commensalis has been explored by dissection, light and electron microscopy and absorption spectrophotometry. The main longitudinal vessels are the dorsal, ventral, perineural, sub-oesophageal, supra-oesophageal and heart. Each segment has a segmental vessel which communicates with the dorsal vessel in thoracic setigers and the gut sinus in abdominal setigers. Branches of the segmental vessels in setigers 2–9 supply the gonads. A blood sinus envelopes most of the gut. Circulation is maintained by the pumping of the heart which immediately supplies blood to the supra-oesophageal ganglion, the branchiae and the palps. These are paralleled by a system of collecting vessels. The sinus of the supra-oesophageal ganglion receives a number of different axonal endings, some of which may be neurosecretory. The retroperitoneal vessels in their most developed form are composed of an intima, longitudinal and circular muscles and a peritoneum. The heart vessel contains a cardiac body whose cells appear to contain vacuoles of blood pigment. The blood pigment exhibits the absorption characteristics of a chlorocruorin with maxima at 438, 558 and 606 nm.     

Paralineopsis taki gen. et sp. nov., a littoral heteronemertean from Japan,provided with special proboscideal,circulatory and sensory organs of significance to nemertean systematics

Some morphological features with major systematic significance are recorded in the heteronemertean Paralineopsis taki gen. et sp. nov. from Onomichi, Japan as follows: horizontal band of specialized epithelium extends from near apex to the opening of the cerebral organ canal on either side of the head; precerebral region filled with gelatinous (hyaline) connective tissue in which longitudinal muscles are absent; body wall muscles do not accompany rhynchodaeal invagination; rhynchodaeum initially only epidermal; inner longitudinal muscles of ventral wall of cephalic blood lacuna become intimately associated with rhynchodaeum forming a dorsal saddle over it; cerebral organs do not penetrate inner longitudinal muscles, and do not contact blood vascular system; proboscideal diaphragm post-cerebral; outer longitudinal muscles absent throughout body; longitudinal muscles of proboscis derived from inner longitudinal musculature. The systematic relationship of P. taki and Paralineus elisabethae (Schütz, 1911) from Villefranche, France is discussed.     

Muscle fibers in the central nervous system of nemerteans: Spatial organization and functional role

The system of muscle fibers associated with the brain and lateral nerve cords is present in all major groups of enoplan nemerteans. Unfortunately, very little is known about the functional role and spatial arrangement of these muscles of the central nervous system. This article examines the architecture of the musculature of the central nervous system in two species of monostiliferous nemerteans (Emplectonema gracile and Tetrastemma cf. candidum) using phalloidin staining and confocal microscopy. The article also briefly discusses the body‐wall musculature and the muscles of the cephalic region. In both species, the lateral nerve cords possess two pairs of cardinal muscles that run the length of the nerve cords and pass through the ventral cerebral ganglia. A system of peripheral muscles forms a meshwork around the lateral nerve cords in E. gracile. The actin‐rich processes that ramify within the nerve cords in E. gracile (transverse fibers) might represent a separate population of glia‐like cells or sarcoplasmic projections of the peripheral muscles of the central nervous system. The lateral nerve cords in T. cf. candidum lack peripheral muscles but have muscles similar in their position and orientation to the transverse fibers. The musculature of the central nervous system is hypothesized to function as a support system for the lateral nerve cords and brain, preventing rupturing and herniation of the nervous tissue during locomotion. The occurrence of muscles of the central nervous system in nemerteans and other groups and their possible relevance in taxonomy are discussed. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

The venous system of the terrestrial crab Ocypode cordimanus (Desmarest 1825) with particular reference to the vasculature of the lungs

The respiratory system of Ocypode cordimanus consists of seven pairs of gills, modified for aerial gas exchange, and a single pair of lungs. Each lung is formed from the inner surface of the branchiostegite and the thoracic wall of the branchial chamber. The branchiostegal surface is increased by a fleshy infolding, the branchiostegal shelf, whilst the surface area of the thoracic lung wall is enhanced by a large flaplike fold. The anatomy of the major sinus systems and the vascular supply to the lungs were investigated. Venous hemolymph is supplied to the lungs potentially from all the major body sinuses. The dorsal, ventral, hepatic, and infrabranchial sinuses are all connected anteriorly to the two eye sinuses which distribute hemolymph to the lungs. Each eye sinus gives off five branches to the branchiostegal lung surface and one to the thoracic lung wall. These afferent vessels are highly branched and interdigitate closely with efferent vessels. The two systems are connected by flat lacunae lying just beneath the respiratory epithelium and these are believed to be the site of gas exchange. The efferent vessels empty into two pulmonary veins on each side, one serving the branchiostegal lung wall and the other the thoracic wall. The two vessels on each side fuse before joining the pericardial cavity as a single trunk on each side.     

The role of the Y-organ and cephalic gland in ecdysteroid production and the control of molting in the crayfish,Orconectes limosus

Summary The production of ecdysteroids (monitored by RIA) by Y-organs and cephalic glands in vitro was measured and hemolymph ecdysteroid levels were determined in the crayfish,Orconectes limosus, both after eyestalk ablation and as a function of time during natural premolt. Y-organ synthesis of ecdysteroid increased in parallel with a rise in hemolymph ecdysteroid concentrations under both conditions, peaking in substage D₂ of premolt. Y-organ ecdysteroid output after eyestalk ablation was 3–4 times higher. Thus, removal of the inhibiting system of the eyestalk effectively removes not only the principal control but also any modulation of ecdysteroid secretion by the Y-organs. Ecdysteroid levels remained low in Y-organ-ectomized crayfish, although premolt was initiated in some animals. The cephalic gland does not appear to contribute to the regulation of molting inOrconectes limosus. The Y-organs, on the other hand, are a principal source of ecdysteroids which regulate the major synthetic activities of premolt.     

Anthobothrium lesteri n. sp. (Cestoda: Tetraphyllidea) in Carcharhinus melanopterus from Heron Island, Australia, with comments on its site, mode of attachment, reproductive strategy and membership of the genus

Anthobothrium lesteri n. sp. in Carcharhinus melanopterus from Heron Island, Australia is described and figured. A combination of characters, namely the number of testes, a weakly laciniate strobila and mature proglottis which is conspicuously longer than wide distinguishes it from other species that appear to be consistent with van Beneden's original concept of Anthobothrium . The scolex and the peduncle are relatively small and frail when compared with the rest of the strobila and with the detached proglottis. A myzorhynchus is absent and the stalked, undivided, simple bothridia have thickened margins. Two circular areas of muscles, which resemble accessory suckers, occur in the centre of each bothridium. There is a distinct cephalic peduncle with spiniform blade-like microtriches followed by craspedote proglottides which have a posterior four-lobed velum. Apolysis is well developed and the oncosphere has a polar filament and a dense covering of spines. Comments are made on the site, the mode of attachment, an aspect of the reproductive strategy of the new species in relation to intestinal eversion in some sharks, and membership of the genus.     

Modifications of motoneuron development following transplantation of thoracic spinal cord to the lumbar region in the chick embryo: evidence for target-derived signals that regulate differentiation.

In order to examine the role of target cells in the development of spinal motoneurons, the neural tube from thoracic segments was transplanted to the lumbar region on embryonic day (E) 2, and allowed to innervate hindlimb muscles in the chick embryo. When examined at later stages of development, the proportion of white and gray matter in the thoracic transplant was altered to resemble normal lumbar cord. Many thoracic motoneurons were able to survive up to posthatching stages following transplantation. The branching and arborization of dendrites of thoracic motoneurons innervating hindlimb muscles, as well as motoneuron (soma) size, were also increased to an extent approximating that seen in normal lumbar motoneurons. In support of previous studies using a similar transplant model, we have also found that the peripheral (intramuscular) branching pattern of thoracic motoneuron axons innervating hindlimb muscles was similar to that of normal lumbar motoneurons. Axon size and the degree of myelination of transplanted thoracic motoneuron axons were also increased so that these parameters more closely resembled axons of normal lumbar than normal thoracic spinal motoneurons. Virtually all of the changes in motoneuron properties noted above were observed irrespective of whether or not the transplanted spinal cord had developed in anatomical continuity with the host rostral cord. Accordingly, it is unlikely that the changes in the development of transplanted thoracic motoneurons reported here are induced either entirely, or in part, by signals derived from the host central nervous system. Rather, these changes appear to be mediated by interactions between the transplanted motoneurons and the hindlimb. We favor the notion that retrograde trophic signals derived from the hindlimb act to modulate the development of innervating motoneurons. Whether this signal involves a diffusible trophic agent released from target cells, or acts by some other mechanism is presently unknown.     

Modifications of motoneuron development following transplantation of thoracic spinal cord to the lumbar region in the chick embryo: Evidence for target-derived signals that regulate differentiation

In order to examine the role of target cells in the development of spinal motoneurons, the neural tube from thoracic segments was transplanted to the lumbar region on embryonic day (E) 2, and allowed to innervate hindlimb muscles in the chick embryo. When examined at later stages of development, the proportion of white and gray matter in the thoracic transplant was altered to resemble normal lumbar cord. Many thoracic motoneurons were able to survive up to posthatching stages following transplantation. The branching and arborization of dendrites of thoracic motoneurons innervating hindlimb muscles, as well as motoneuron (soma) size, were also increased to an extent approximating that seen in normal lumbar motoneurons. In support of previous studies using a similar transplant model, we have also found that the peripheral (intramuscular) branching pattern of thoracic motoneuron axons innervating hindlimb muscles was similar to that of normal lumbar motoneurons. Axon size and the degree of myelination of transplanted thoracic motoneuron axons were also increased so that these parameters more closely resembled axons of normal lumbar than normal thoracic spinal motoneurons. Virtually all of the changes in motoneuron properties noted above were observed irrespective of whether or not the transplanted spinal cord had developed in anatomical continuity with the host rostral cord. Accordingly, it is unlikely that the changes in the development of transplanted thoracic motoneurons reported here are induced either entirely, or in part, by signals derived from the host central nervous system. Rather, these changes appear to be mediated by interactions between the transplanted motoneurons and the hindlimb. We favor the notion that retrograde trophic signals derived from the hindlimb act to modulate the development of innervating motoneurons. Whether this signal involves a diffusible trophic agent released from target cells, or acts by some other mechanism is presently unknown. © 1992 John Wiley & Sons, Inc.     

Deep-sea Tardigrada from South Shetland Islands (Antarctica) with description of Angursa antarctica sp. nov. (Arthrotardigrada, Halechiniscidae)

A new species of marine tardigrade is described coming from the muddy sediment of the Antarctic deep sea. Angursa antarctica sp. nov. is characterized by the presence of balloon-shaped primary clavae, long lateral cirri, long cephalic cirri, spines on legs I, hemispherical capsule-shaped papillae on legs IV, and short external peduncles. Geographical distribution of the genus Angursa extends to Antarctic waters, suggesting a cosmopolitan distribution for this bathyal and abyssal genus. A table comparing the main differentiating characteristics of the species of Angursa is presented. Received: 25 July 1997 / Accepted: 9 November 1997     

Bithorax Complex genes control alary muscle patterning along the cardiac tube of Drosophila

Cardiac specification models are widely utilized to provide insight into the expression and function of homologous genes and structures in humans. In Drosophila, contractions of the alary muscles control hemolymph inflow and support the cardiac tube, however embryonic development of these muscles remain largely understudied. We found that alary muscles in Drosophila embryos appear as segmental pairs, attaching dorsally at the seven-up (svp) expressing pericardial cells along the cardiac dorsal vessel, and laterally to the body wall. Normal patterning of alary muscles along the dorsal vessel was found to be a function of the Bithorax Complex genes abdominal-A (abd-A) and Ultrabithorax (Ubx) but not of the orphan nuclear receptor gene svp. Ectopic expression of either abd-A or Ubx resulted in an increase in the number of alary muscle pairs from seven to 10, and also produced a general elongation of the dorsal vessel. A single knockout of Ubx resulted in a reduced number of alary muscles. Double knockouts of both Ubx and abd-A prevented alary muscles from developing normally and from attaching to the dorsal vessel. These studies demonstrate an additional facet of muscle development that depends upon the Hox genes, and define for the first time mechanisms that impact development of this important subset of muscles.     

Light modulation of postural flexor motoneurones in the tail-fan of the squat lobsterGalathea strigosa (Crustacea,Anomura)

Summary Photosensitivity in the terminal abdominal ganglion (G5) of an anomuran, the squat lobsterGalathea strigosa (Crustacea, Decapoda, Anomura), is described. In contrast to the caudal photoreceptors (CPRs) of long-tailed natantid and macruran decapod crustaceans, the caudal photosensitive elements in G5 inG. strigosa apparently lack the conventional spiking rostral conduction pathways to the thoracic ganglia, and instead make their output connections to a bilateral pair of tonic flexor motoneurones originating within the caudal ganglion itself. These flexor motoneurones modulate the activity of two bilaterally paired uropod coxopodite tonic flexor muscles. This photomodulated motoneurone (PMMN) activity is not abolished by sectioning the abdominal nerve cord anterior to G5. The pattern of photosensitivity, while differing from that shown by other CPRs, resembles instead the pattern attributed to photosensitive interneurones (PSIs) of rostral abdominal ganglia of crayfish and other long-tailed decapod crustaceans.The caudal PSIs inG. strigosa appear to be involved in the postural control of the tail-fan as it is held flexed against the cephalothorax.     

Contraction of the ventral abdomen potentiates extracardiac retrograde hemolymph propulsion in the mosquito hemocoel

Background

Hemolymph circulation in mosquitoes is primarily controlled by the contractile action of a dorsal vessel that runs underneath the dorsal midline and is subdivided into a thoracic aorta and an abdominal heart. Wave-like peristaltic contractions of the heart alternate in propelling hemolymph in anterograde and retrograde directions, where it empties into the hemocoel at the terminal ends of the insect. During our analyses of hemolymph propulsion in Anopheles gambiae, we observed periodic ventral abdominal contractions and hypothesized that they promote extracardiac hemolymph circulation in the abdominal hemocoel.

Methodology/Principal Findings

We devised methods to simultaneously analyze both heart and abdominal contractions, as well as to measure hemolymph flow in the abdominal hemocoel. Qualitative and quantitative analyses revealed that ventral abdominal contractions occur as series of bursts that propagate in the retrograde direction. Periods of ventral abdominal contraction begin only during periods of anterograde heart contraction and end immediately following a heartbeat directional reversal, suggesting that ventral abdominal contractions function to propel extracardiac hemolymph in the retrograde direction. To test this functional role, fluorescent microspheres were intrathoracically injected and their trajectory tracked throughout the hemocoel. Quantitative measurements of microsphere movement in extracardiac regions of the abdominal cavity showed that during periods of abdominal contractions hemolymph flows in dorsal and retrograde directions at a higher velocity and with greater acceleration than during periods of abdominal rest. Histochemical staining of the abdominal musculature then revealed that ventral abdominal contractions result from the contraction of intrasegmental lateral muscle fibers, intersegmental ventral muscle bands, and the ventral transverse muscles that form the ventral diaphragm.

Conclusions/Significance

These data show that abdominal contractions potentiate extracardiac retrograde hemolymph propulsion in the abdominal hemocoel during periods of anterograde heart flow.     

Canine mesenteric artery and vein convey no difference in the content of major contractile proteins

Background  

Mesenteric arteries and veins are composed of tonic smooth muscles and serve distinct functions in the peripheral circulation. However, the basis for the functional disparity of the resistive and capacitative parts of the mesenteric circulation is poorly understood. We studied potential differences in the expression levels of six contractile proteins in secondary and tertiary branches of the inferior mesenteric artery and vein along with differences in the vessel wall morphology.     

A mosquito neuropeptide in a moth larva (Helicoverpa zea): relation to FMRF-amide immunoreactivity.

The cerebral nervous and midgut endocrine systems of the larval corn earworm, Helicoverpa zea, were examined using light microscopy and immunocytochemistry for RF-amide family peptides. Immunoreactivity for a mosquito neuropeptide, Aedes Head Peptide-I (Aea-HP-I,pERPhPSLKTRFa), is widely distributed in this lepidopteran. Immunostaining for Aea-HP-I is localized (1a) in perikarya and axons of the brain, the subesophageal ganglion, and the first thoracic ganglion, (b) in peripheral axons innervating muscles of the midgut, and (2) in numerous midgut endocrine cells. Aea-HP-I-associated activity generally occurs as a subset of FMRF-amide (FMRFa; a molluscan cardioactive peptide) immunoreactivity. Cross-reactivity studies indicate that Aea-HP-I and FMRFa immunoreactivities are heterogeneous in the cerebral nervous system and in axons innervating the muscles of the midgut, but may be homogeneous in midgut endocrine cells. Radioimmunoassay for Aea-HP-I reveals immunoreactivity in hemolymph, as well as in extracts of midguts and heads.     

Circulatory organs of Diplura (Hexapoda): the basic design in Hexapoda?

The circulatory systems of Campodea augens and Catajapyx aquilonaris (Hexapoda: Diplura) have been examined by means of light and electron microscopy. Hemolymph flow has also been investigated in vivo. Both species share features that deviate conspicuously from the common textbook design of the insect circulatory system: (i) antennal vessels connected to the anterior end of the dorsal vessel; (ii) presence of a circumoesophageal vessel ring in the head; (iii) a bidirectional flow within the dorsal vessel, made possible by intracardiac valves; (iv) posterior end of the dorsal vessel tube opens into a caudal chamber connected to cercal vessels (in Campodea) or to cercal channels (in Catajapyx); (v) dorsal diaphragm barely realized, ventral diaphragm absent altogether, and (vi) legs without specific organs serving hemolymph circulation. Comparative analysis has revealed that these characters in Diplura represent the most plesiomorphic condition in the circulatory organs of all extant Hexapoda. In the basic evolutionary lineages of insects, some organ components have been lost and the peripheral vessels decoupled from the dorsal vessel; as a result, autonomous accessory pulsatile organs have evolved to supply hemolymph to long body appendages and a unidirectional hemolymph flow mode prevailed within the dorsal vessel.     

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.     

The insect abdomen--a heartbeat manager in insects?

Different possibilities of coordination between circulation, respiration and abdominal movements were found in pupae of Pieris brassicae, Tenebrio molitor, Galleria mellonella and Leptinotarsa decemlineata. Coordination principles depend on metabolic rate: the need to support circulation with abdominal movements appears only at higher metabolic rates. Integration between different abdominal movements and circulation depends on species, on physiological state and, supposedly, on internal morphology. At low metabolic rates, there is no need for a very intensive hemolymph flow, and the dorsal vessel is capable of initiating and/or maintaining necessary hemolymph flow. Starting from a certain metabolic level, it is possible that the abdomen is used to accelerate hemolymph flow in the case of a large amount of hemolymph. When the necessary flow speed has been reached, relatively weak pulsation of the dorsal vessel with accessory pulsatile organs and diaphragms can easily maintain the necessary flow intensity. Heart activity may sometimes be initiated by abdominal movements via cardiac reflex or mechanical excitation. Sometimes, when heart function is weakened by histolysis, the abdomen may temporarily take over the main circulatory function or occasionally contribute to acceleration of low-speed hemolymph flow. In this case the functions are simultaneous and may be triggered by some mediator(s). In active adult insects the whole body is moving, and hence hemolymph circulates and the tracheal system is effectively ventilated by a whole body ensemble consisting of the dorsal vessel, moving organs, body appendages and accessory pulsatile organs. The mechanism of autocirculation (analogous to autoventilation in gas exchange) is a probable mechanism in circulation in adult insects.     

Arterial system of the gill of the lobster,Homarus americanus

Three-dimensional architecture of the branchial artery and venous vasculature of Homarus americanus was studied by the method of corrosion cast or styrene cracking and by scanning electron microscopy. Four arteries, the epibranchial (EA) and hypobranchial arteries (HA) on the septal wall of the afferent and efferent vessels, respectively, and two lateral canal arteries (LCA), each in one of the paired lateral canals, run parallel to the gill axis. The EA directs dendroid branches to the spongy tissue in the afferent vessel wall far from the efferent, supplying oxygen to the otherwise oxygen-depleted tissue. The HA distributes the filament arteriole (FA) into the central channel of individual middle filaments via the LCA. The FA opens halfway at a position where the channel narrows. Thus, it is likely that venous hemolymph in the central channel flows from base to tip in the direction in which arterial hemolymph from the FA flows. This and the anatomy of venous vasculature suggest three probable patterns of perfusion from afferent to efferent vessels: double serial circulation via the outer and inner filaments and novel routes both through the middle filament, i.e., single circulation via the afferent and efferent channels of this filament and double serial circulation via the outer filament and then the central channel of the middle. On the basis of the physics of flow and known physiological data, we propose that switching of these routes that involves independently functional multiple double serial circulations can play an important role in controlling efficiency of gas exchange, particularly during hypoxia. J Morphol. 233:165–181, 1997. © 1997 Wiley-Liss, Inc.     

The general biology of Verruca stroemia (O. F. Müller). I. Geographical and regional distribution; Cirral activity and feeding

As an introduction to a series of papers on Verruca stroemia (O. F. Müller) the geographical and regional distribution is given: it is characteristically an eastern Atlantic shallow-water species but is not uncommon in parts of the Mediterranean Sea.The cirri and mouth parts are described and also the opercular membrane which in some ways resembles that of Lithotrya.In still water the cirri may be slowly extruded and withdrawn with relatively little forward movement on the down-stroke. The cirri are held close to the ‘velum’ and no internal mantle cavity current could be detected: cirral movements cause small external currents as in a balanid. In the presence of water currents the cirri show a typical extension reaction: when particles strike the cirri they are withdrawn and the food passed to the mouth. The cirri respond only partly to the current direction. Verruca stroemia has no muscles other than the adductor scutorum attached to the shell and cannot change the volume of the mantle cavity by movement of the operculum. Cirral activity closely resembles that of Pollicipes.During pre-copulatory movements the penis makes searching movements but the area searched is relatively restricted.Nauplii are expelled behind the cirri as the latter are extruded, the caudal appendages seeming to play a part in dispersing the nauplii.An examination of the gut contents reveals few whole organisms, rather a mass of fine unrecognizable particulate matter.     

Echinobothrium chisholmae n. sp. (Cestoda,Diphyllidea) from the giant shovel-nose ray Rhinobatos typus from Australia,with observations on the ultrastructure of its scolex musculature and peduncular spines

Echinobothrium chisholmae n. sp. is described from Rhinobatos typus Bennett (Rhinobatidae), collected from Heron Island, Great Barrier Reef, Australia. E. chisholmae differs from all congeners in possessing 11 hooks in each dorsal and ventral group on the rostellum and groups of 3-6 hooklets on either side of the hooks. A single metacestode of E. chisholmae was collected from the decapod crustacean Penaeus longistylus Kubo. Yellow pigmentation of the cephalic peduncle in immature adults is caused by the accumulation of large vesicles in the distal cytoplasm of the tegument. The vesicles probably provide materials for spine formation. Ultrastructural examination of the rostellar musculature revealed that the muscles are stratified (striated-like), consisting of a periodic repetition of sarcomeres separated by perforated Z-like lines that are oblique to the long axes of the myofilaments.