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Studies on the muscular system of gastrotrichs revealed the presence of muscles in a new orientation, that of left- and right-handed helices around the digestive tract. These helicoidal muscles are found on the pharynx and intestine of numerous species in both orders, Chaetonotida and Macrodasyida. In many cases, the helices surround both circular and longitudinal muscle bands. The number of helices is a function of ontogeny, and their position along the alimentary canal may be family-specific. To date, helicoidal muscles have been found in the following families: Chaetonotidae, Dactylopodolidae, Macrodasyidae, Thaumastodermatidae, Turbanellidae, and Xenotrichulidae. The precise function of these muscles remains to be determined, but we hypothesize that they play two roles: antagonize dilations of the pharynx and intestine during feeding and contribute to shape change in the body during ciliary locomotion. Based on their wide systematic distribution, these muscles are likely to be part of the ground pattern of the Gastrotricha.

Attempts to infer gastrotrich phylogeny from morphological characters has revealed the family Dactylopodolidae to be the sister taxon to the rest of the Macrodasyida. Dactylopodola retains several plesiomorphic characteristics making the genus worthy of attention for further phylogenetic investigation. Here we report the results of research on two organ systems of D. baltica, the muscular and nervous system. Immunofluorescent localization of acetylated tubulin and serotonin revealed the orientation of both main nerve cords and small sensory fibers in the species. In several cases, the nerves of D. baltica correspond in position to those of other macrodasyid taxa. Unique to D. baltica is the innervation of immunoreactive 5-HT neurons in the cerebral eyespots. In the muscular system, the arrangement of specific muscle sets is similar between D. baltica and other macrodasyidans: inner circular muscles, left- and right-handed helicoidal muscles, longitudinal muscles, and outer circular rings. The ventrolateral longitudinal muscles are uniquely arranged at the anterior and posterior portion of the body, as are their sites of insertion. It is proposed that the structure and orientation of the muscles and nerves reflect both local adaptation and phylogeny, and should provide a useful source for information on gastrotrich evolution.

The basic organization of the rotifer nervous system has been known for over a century, while recent ultrastructural and behavioral observations have provided valuable insights into its fine structure and function. The freshwater carnivorous rotifer, Asplanchna brightwelli, is a well-known model for the study of cyclomorphosis and cyclical parthenogenesis, but as of yet, few details exist on its neurobiology. To gain insight into the structure of its nervous system, and provide a foundation for future research, the cerebral ganglion was studied with immunohistochemistry, CLSM, and computer modeling. Immunoreactivity to serotonin, FMRFamide, SCPb, and alpha-and beta-tubulin revealed numerous connections within the brain and between the brain and other organ systems. Anti-5HT was especially useful in delineating intracerebral connections and connections to presumed sensory structures in the apical field and trunk region. Approximately 20 pairs of serotoninergic petikarya and their axonal extensions were all symmetrically arranged within the cerebral ganglion a distinct fibrous neuropil was absent. Decussations, or the crossing of axons at the body midline, were prevalent within the cerebral ganglion and formed pathways to regions in the corona and trunk. Early stage juveniles, still retained within the adult pseudocoelom, also showed significant immunoreactivity in the cerebral ganglion and displayed a similar pattern of connections within the brain as the adults. The utility of neuroanatomical characters derived by CLSM and immunohistochemistry is discussed in reference to the future of rotifer research.

Filinia longiseta is a planktonic rotifer common in lentic systems. The species possesses paired, elongate lateral spines that function in saltatory sweeping motions in response to sheer disturbances by predators. The purpose of this investigation was to gain insight into the neuromuscular control of spine movement through the use of electron microscopy, confocal laser scanning microscopy, and immunohistochemistry. Bodywall musculature and neural innervation were visualized using CLSM in combination with phalloidin and antibodies to structural proteins (tubulins) and various neurotransmitters (serotonin, FMRFamide, etc). Computer generated three-dimensional models of the neuroanatomy were subsequently constructed. Results show that muscular supply to the lateral spines is indirect: paired, striated body-wall muscles insert on the syncytial integument around the spines and do not insert within the hollow spine interior. Dorosoventral movement of the spines appears to be produced by local distortions of the integument caused by antagonistic muscular contractions. A single neuron (non-immunoreactive to 5HT or FMRFamide) innervates the hollow spines and may have a propioreceptive function, relaying positional information to the cererbral ganglion about spinal movement. Additional neuroanatomical details are presented.

Neomeniomorpha (Solenogastres) is a small and monophyletic taxon of marine, shell-less molluscs that share a potentially primitive phylogenetic position with species of Chaetodermomorpha (Caudofoveata). Species of both clades are poorly cephalized, wormlike, and possess a suite of plesiomorphic morphologies that characterize them as primitive molluscs. In this study, three species of interstitial solenogastres (Tegulaherpia(2), Meiomenia (1)) were studied using a combination of confocal microscopy, phalloidin labeling, and immunohistochemistry to gain insight into the structure of the neuromuscular system. Antibodies to serotonin, FMRFamide, and SCPb allowed for visualization of the nervous system including cerebral and pedal ganglia, pedal and visceral nerve cords, intercordal commissures, and innervation of the bodywall, velum, and pedal pit. 5HTimmunoreactivity provided the most revealing details, allowing for unambiguous demonstration of neuronal perikarya and processes throughout the body. Phalloidin was used to visualize the bodywall and gut musculature, exposing a 3-D gridwork of circular, diagonal, longitudinal, and dorsoventral muscles. Results reveal that solenogastres possess a neuromuscular system analogous to the new molluscan archetype (HAM) presented by Haszprunar, and application of the aforementioned methodologies (cLSM, immunohistochemistry) will provide valuable insights into the structure and evolution of aplacophoran molluscs.

We developed a computational method for the identification of putative cis-regulatory elements, which incorporates a direct measure of the effects of selection as a determinant in non-protein coding sequence evolution. As such, the method provides a biologically relevant framework for comparisons of non-protein coding sequence evolution. Comparisons of orthologous HoxA, Aa and Ab cluster paralogous group 2 intergenic and intron-related sequences from Mus muscu/us(mouse), Homo sapiens (humans), Heterodontus francisci (horn shark), Polypterus senegalus (bichir), Danio rerio (zebrafish), Oreochromis niloticus (Nile tilapia), Morone saxatilis (striped bass), and Takifugu rubripes (Japanese pufferfish) revealed three sequence domains that are under purifying selection in all the species and on both clusters, indicative that these three regions likely represent fundamental regulatory control elements of HoxA cluster paralogous group 2 genes in their common gnathostome ancestor. Detailed analysis of one of these three domains using both Mus musculus and Morone saxatilis HoxA paralogous group 2 regions as the index for comparisons demonstrated the presence of four general gnathostome elements, one general actinopterygian element, two general teleost elements and a host of mammalian and perciform-specific elements. The results also showed the partitioning of cis-regulatory elements between the actinopterygian HoxAa and Ab clusters relative to the inferred ancestral gnathostome HoxA cluster. Overall, our results indicate that the evolution of Hox paralogous group 2 cis-regulatory regions is dominated by the evolution of novel lineage-specific elements superimposed on a framework of shared common ancestral elements.

Gastrotrichs are characterized by a suite of unique morphologies (apomorphies) that set them apart from other animals. Among the more recent findings include muscles that form distinct spirals around the digestive tract. These cellular spirals in the form of crossed-helices form alternating right- and left-handed geodesic springs that make alpha angles of ca. 54 degrees, the ideal solution for the fiber angle in a thin pressurized cylinder of circular cross-section. Based on new observations with confocal scanning electron microscopy (CSLM) and TEM, the helices are constructed of obliquely-striated muscle cells and are positioned external of nearly all other muscles that contact the gut tube. The crossed-helices are hypothesized to mechanically constrain the shape of underlying muscles, muscle function, gut shape, and the rigidity of the hydrostatic digestive tract. Attachment forces maintain a constant position of the helical center with respect to the longitudinal body axis, permitting radial expansion of the gut tube without linear expansion. A preliminary biomechanical model based on this system shows that the helices function as both reinforcer and mechanical spring; they do not deflect or distort under longitudinal body constriction and they restore original body shape without the necessity of antagonistic contractive forces by circular muscles.

Gastrotrichs live in an environment characterized by extremely low Reynolds numbers. The morphology of the gastrotrich feeding apparatus is therefore adapted to overcome viscosity and enhance prey capture. An investigation of mouth geometry, pharynx structure, and cephalic muscle topology was undertaken using electron microscopy, epifluorescence and confocal scanning laser microscopy to gain insight into the evolutionary morphology of the head and feeding system of thaumastodermatid gastrotrichs. Results suggest that species of Thaumastodermatidae evolved a novel head morphology to exploit the interplay of hydrodynamics, evolutionary constraints, and prey specialization. The thaumastodermatid head is characterized by a distinctly broadened morphology that bears a wide, dorsoventrally-compressed mouth and a weakly developed myoepithelial pharynx, characterized by a low myofilament density and few sarcomeres. The mouth is covered by a dorsolateral expansion of the head called the oral hood that contains extensions of pharynx and body wall. It is hypothesized that an evolutionary loss of radial myofilaments in the pharynx and fluid mechanic principles governing the functional morphology of feeding have driven the evolution of head morphology. A weak pump hypothesis is proposed that predicts a low density of pharyngeal muscle translates into an ineffective muscular pump in a viscous medium. Selection to maximize the surface area of the head to either enclose a small volume of water or create a funnel opening would theoretically increase pumping capacity for food uptake and transport. Based on these observations, it is proposed that moderate evolutionary constraints in pharyngeal organization may channel evolutionary changes in the morphology of the head leading to specializations of the feeding apparatus.

I have really enjoyed working with the members of the Technical Committees these past few years, but sad to say my tenure in this position is coming to an end. A new Vice President for Technical Activities will be elected for 2009 and this is my last submission in this fi ne magazine. Dr Steve Adam assisted in getting a new PARs going in the Standards arena, with their potential to become IEEE Standards in many important areas. Steve?s contributions were greatly appreciated by all of us who had contact with him. [ABSTRACT FROM PUBLISHER]

Gastrotrichs are acoelomate micrometazoans common to marine interstitial environments of sublittoral sediments and exposed sandy beaches. The genusNeodasys(Chaetonotida) contains three marine species known from oceans and seas worldwide, and figures prominently in discussions of gastrotrich origins. To gain insight into the phylogenetic position ofNeodasysand to understand the adaptive significance of muscle anatomy in marine interstitial gastrotrichs, a fluorescent phalloidin-linked marker was used to view the organization of muscles in two species from North America and Australia. Muscular topography ofNeodasys cirritusfrom Florida, USA, andNeodasyscf.uchidaifrom Queensland, Australia, was found to be similar between species and to basal species of Macrodasyida; muscles were present in circular, longitudinal and helicoidal patterns. Musculature of the midgut region was partially reduced relative to basal macrodasyidan gastrotrichs, but well developed relative to most other chaetonotidan gastrotrichs. In general, muscle patterns in species ofNeodasysclosely correspond with those of other gastrotrichs of similar size and body type, and may therefore reflect a common adaptive solution to the physical demands of the interstitial environment. Results also suggest that reductions in midgut musculature may be functionally related to oviposition and, as such, are probably not homologous with similar reductions of circular muscles in other species of Chaetonotida. [ABSTRACT FROM AUTHOR]