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.]     

Feeding Characteristics of Deep-Sea Acorn Worm (Hemichordata,Enteropneusta, Torquaratoridae) from the Bering Sea

Doklady Biological Sciences - Deep-sea hemichordates Torquaratoridae gen. sp. reach high abundance up to 12 spec. m–2 at the depths of 1830–2130 m on the slope of the Volcanologists...     

Morphology of a new deep‐sea acorn worm (class Enteropneusta,phylum Hemichordata): A part‐time demersal drifter with externalized ovaries

Ten individuals of an enteropneust in the family Torquaratoridae were videotaped between 2,900 and 3,500 m in the Eastern Pacific—one drifting a few centimeters above the bottom, two exposed on the substrate, and seven partly burrowed, reflecting a bentho‐pelagic life style. Here, we describe a captured specimen (26 cm living length) as the holotype of Allapasus aurantiacus n. gen., n. sp. The small proboscis is dome‐shaped, and the collar is only slightly wider than deep; both of these body regions are more muscular than in other torquaratorids, which presumably facilitates burrowing. The proboscis complex, in contrast to that of shallow‐living enteropneusts, lacks a pericardial sac and is located relatively posteriorly in the proboscis stalk. The stomochord is separated from the main course of the gut by the intervention of a small, plate‐like proboscis skeleton lacking posterior horns. The most anterior region of the trunk houses the pharynx, in which the pharyngeal skeletal bars are not connected by synapticles. The postpharyngeal trunk comprises three intestinal regions: prehepatic, hepatic (with conspicuous sacculations), and posthepatic. On either side of the worm, a flap of body wall (lateral wing) runs the entire length of the trunk. The two lateral wings can wrap the body so their edges meet in the dorsal midline, although they often gape open along the pharyngeal region. The holotype is a female (presumably the species is gonochoric) with numerous ovaries located in the lateral wings along the pharyngeal region. Each larger ovary contains a single primary oocyte (up to 1,500 μm in diameter) and bulges outwards in an epidermal pouch attached to the rest of the body by a slender stalk. Such externalized ovaries are unprecedented in any animal, and nothing is yet known of their role in the reproductive biology of A. aurantiacus. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

Electron microscopic study of the intestinal epithelium of Saccoglossus mereschkowskii (Enteropneusta, Hemichordata)

Epithelium of the hepatic region of the intestine in Saccoglossus mereschkowskii, a representative of enteropneusts (Enteropneusta, Hemichordata) standing at the base of Chordata, has been investigated using electron microscope. The ultrastructure of ciliated and granular epithelial cells, elements of the intraepithelial nerve layer, and intercellular junctions have been characterized. The data concerning details of the organization of the ciliary apparatus and rootlets system are presented. It is justified the presence of complicated supporting construction of cilia which performs a mechanical stabilizing function and possibly also provide synchronization of ciliary movements. The presence of cilia with two centrioles is considered as an adaptation to high functional load on ciliary apparatus. Well developed bundles of myofilaments are found in the cytoplasm of the basal portions of ciliary cells that characterizes these cells as myoepithelial. The features indicating the role of ciliary cells in absorption are described. The capability of these cells to balloon-like secretion is considered. Data on the accumulation of food reserves in the form of lipid droplets and glycogen in the cell cytoplasm are presented. Ciliated cells are characterized by their function as ciliated secretory-absorptive myoepithelial cells. Based on the location of secretory granules both in the apical and basal portions of granular cells, an exocrine-endocrine function of these cells has been suggested. Typical endocrine cells in the intestinal epithelium of S. mereschkowskii are absent. Several types of granules in the nerve fibers cytoplasm are described. Junctions between the nerve fibers and basal portions of ciliary and granular epithelial cells are found. Nerve regulation of contractile and secretory functions of epithelial cells is supposed. The presence of the regulatory nerve-endocrine system that includes receptor cells of open type, secretory endocrine-like cells and nerve elements of nerve layer is supposed in the intestinal epithelium of enteropneusts.     

Diversification of acorn worms (Hemichordata, Enteropneusta) revealed in the deep sea

Enteropneusts (phylum Hemichordata), although studied extensively because of their close relationship to chordates, have long been considered shallow-water, burrowing animals. The present paper more than doubles the number of enteropneust species recorded in the deep sea based on high-resolution imaging and sampling with remotely operated vehicles. We provide direct evidence that some enteropneusts are highly mobile-using changes in posture and currents to drift between feeding sites-and are prominent members of deep, epibenthic communities. In addition, we provide ecological information for each species. We also show that despite their great morphological diversity, most deep-living enteropneusts form a single clade (the rediagnosed family Torquaratoridae) on the basis of rDNA sequences and morphology of the proboscis skeleton and stomochord. The phylogenetic position of the torquaratorids indicates that the group, after evolving from near-shore ancestors, radiated extensively in the deep sea.     

Fine Structure of the Hepatic Sacculations of Glossobalanus minutus (Enteropneusta,Hemichordata)

Abstract The hepatic region of Glossobalanus minutus is characterized by deep foldings of the dorsal side of the gut epithelium which affect the neighbouring tissues and structures: coelomic spaces, musculature and epidermis. The following cell types of the gut epithelium are described: vacuolated cells, undifferentiated cells, two types of mucous cells and two types of granular secretory cells. The nature and function of the different cell types are discussed. Data on the general ciliation and subepithelial nerve plexus of the gut epithelium are also given, with special mention of a possible neuroendocrine secretion towards the subjacent blood spaces. A well-developed blood sinus (gut sinus) lies between the gut and the visceral peritoneum. The ultrastructural features of the gut epithelium and its close association with the blood sinus point to an absorptive function. The coelomic cavity is reduced to a narrow space limited by two peritoneal sheets (visceral and parietal) of myoepithelial nature. Amoebocyte-like cells (coelomocytes) occur free in the coelomic fluid, and muscular, unicellular bridges are attached to both peritoneal walls across the coelomic space. The dorsal epidermis follows the gut foldings and is formed by flat, overlapping cells. The present observations are compared with previous histological, histochemical and ultrastructural data.     

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:     

A new species of Alcyonosyllis Glasby and Watson, 2001 (Polychaeta: Syllidae: Syllinae) from Shimoda,Japan, commensal with the gorgonian Melithaea flabellifera

A new species of Alcyonosyllis Glasby and Watson, 2001 (Polychaeta: Syllidae: Syllinae) is described from shallow water of Shimoda, Izu Peninsula, Japan. The worms were commensal with the gorgonian Melithae flabellifera (Kükenthal, 1909). Alcyonosyllis glasbyi n. sp. differs from all other species of the genus in having a single chaeta per parapodium. The genus is new to Japan.     

An Anatomical Description of a Miniaturized Acorn Worm (Hemichordata,Enteropneusta) with Asexual Reproduction by Paratomy

The interstitial environment of marine sandy bottoms is a nutrient-rich, sheltered habitat whilst at the same time also often a turbulent, space-limited, and ecologically challenging environment dominated by meiofauna. The interstitial fauna is one of the most diverse on earth and accommodates miniaturized representatives from many macrofaunal groups as well as several exclusively meiofaunal phyla. The colonization process of this environment, with the restrictions imposed by limited space and low Reynolds numbers, has selected for great morphological and behavioral changes as well as new life history strategies.Here we describe a new enteropneust species inhabiting the interstices among sand grains in shallow tropical waters of the West Atlantic. With a maximum body length of 0.6 mm, it is the first microscopic adult enteropneust known, a group otherwise ranging from 2 cm to 250 cm in adult size. Asexual reproduction by paratomy has been observed in this new species, a reproductive mode not previously reported among enteropneusts.Morphologically, Meioglossus psammophilus gen. et sp. nov. shows closest resemblance to an early juvenile stage of the acorn worm family Harrimaniidae, a result congruent with its phylogenetic placement based on molecular data. Its position, clearly nested within the larger macrofaunal hemichordates, suggests that this represents an extreme case of miniaturization. The evolutionary pathway to this simple or juvenile appearance, as chiefly demonstrated by its small size, dense ciliation, and single pair of gill pores, may be explained by progenesis. The finding of M. psammophilus gen. et sp. nov. underscores the notion that meiofauna may constitute a rich source of undiscovered metazoan diversity, possibly disguised as juveniles of other species.     

The First Discovery of Trematodes (Digenea) in the Deep-Sea Acorn Worms Torquaratoridae (Hemichordata,Enteropneusta)

Doklady Biological Sciences - Trematodes found in the enteropneust hemichordates are described for the first time. Metacercariae have been found in the trunk coelom, in the collar coelom, in the...     

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.     

Structure of the nervous system in the tornaria larva of<Emphasis Type="Italic"> Balanoglossus proterogonius</Emphasis> (Hemichordata: Enteropneusta) and its phylogenetic implications

The tornaria larva of hemichordates occupies a central position in phylogenetic discussions on the relationships between Echinodermata, Hemichordata, and Chordata. Dipleurula-type larvae (tornaria and echinoderm larvae) are considered to be primary in the life cycle and thus provide a model for the ancestral animal common to all three taxa (the theory of W. Garstang). If the similarities between tornaria and the larvae in Echinodermata result from homology, their nervous systems should be basically similar as well. The present study utilizes anti-serotonin and FMRFamide antisera together with laser scanning microscopy, and transmission electron microscopy, to describe in detail the nervous system of the tornaria of Balanoglossus proterogonius. Serotonin immunoreactive neurons were found in the apical and esophageal ganglia, and in the stomach epithelium. FMRFamide immunoreactive neurons, probably sensory in nature, were detected in the apical ganglion and in the equatorial region of the stomach epithelium. At the ultrastructural level, the apical organ consists of a columnar epithelium of monociliated cells and includes a pair of symmetrical eyespots. The apical ganglion is located at its base and has a well-developed neuropil. Different types of neurons are described in the apical organ, esophagus, and stomach. Comparison with larvae in Echinodermata shows several significant differences in the way the larval nervous system is organized. This calls into question the homology between tornariae and echinoderm larvae. The possibility of convergence between the two larval types is discussed.     

Ostorhinchus yamato,a new species of cardinalfish (Perciformes: Apogonidae) from Japan

Ichthyological Research - The new cardinalfish Ostorhinchus yamato sp. nov. is described on the basis of 135 specimens collected from Japan. The new species resembles Ostorhinchus gularis (Fraser...     

A new species of Megoura (Hemiptera,Aphididae) from Japan

A new species of the genus Megoura, M. lathyricola sp. n., was collected from Lathyrus japonicus subsp. japonicus (Leguminosae) in seashore areas of northern and southern Japan. This species is described and illustrated, and a revised key to the identification of the world species of Megoura is presented.     

Flagelloscypha japonica: a new species of minute basidiomycete (Niaceae) from Japan

A minute basidiomycete belonging to Flagelloscypha (Niaceae, Agaricales) was found on blighted leaves of Rodgersia podophylla in Aomori Prefecture, Japan. The fungus proved to be a new species and was named Flagelloscypha japonica based on its morphological characteristics.     

Fusarium nisikadoi, a new species from Japan

A new species ofFusarium, F. nisikadoi, isolated fromPhyllostachys nigra var.henonis (bamboo) andTriticum aestivum (wheat) in Japan, is described, illustrated and discussed. This species is differentiated from other known species of the genus by the following characteristics: whitish colony color, long zigzag-like chains of 0–3(-5)-septate clavate conidia, intermixed with pyriform conidia, produced mostly from monophialides and rarely from polyphialides in the aerial mycelium, very long and slender sporodochial conidia, and no chlamydospores. The long chains of septate conidia are known only in this species of the genusFusarium. The conidiophores on the aerial mycelium sometimes proliferate sympodially. The species is tentatively placed in the form-sectionLiseola.     

Ericandersonia sagamia, a new genus and species of deep-water eelpouts (Perciformes: Zoarcidae) from Japan

A new genus and species of deep-water zoarcid fish, Ericandersonia sagamia, is described on the basis of four specimens collected from Sagami Bay, Japan, at depths of 880–930 m. This species is placed in the subfamily Gymnelinae and is distinguished from all genera of gymnelines by the following characters: pseudosubmental crest present; frontals partially fused dorsally; parietals meeting in midline; pelvic fins absent; ventral ramus of posttemporal weak; postorbital head pores 5; pectoral-fin rays 14. The phylogenetic analysis (based on 42 morphological characters) indicates that its position is outside the highly modified (= advanced) genera Seleniolycus, Melanostigma, Puzanovia, Nalbantichthys, Opaeophacus, and Andriashevia.