Localisation of the amathamide alkaloids in surface bacteria of Amathia wilsoni Kirkpatrick, 1888 (Bryozoa: Ctenostomata)

The marine bryozoan Amathia wilsoni contains several brominated secondary metabolites, the alkaloid amathamides A–F. Energy dispersive X-ray analysis coupled with scanning electron microscopy was used to localise bromine in sections of Amathia wilsoni. Bromine concentrations higher than background levels were only found on the surface of the bryozoan and not within any of the different internal cell types. The correlation between bromine levels and a rod-shaped bacterium, ubiquitous to the tip region, points to the bacterium being closely associated with the range of amathamides found in Amathia wilsoni.     

The ontogenetical and supposed phylogenetical fate of the parietal muscles in the Ctenostomata (Bryozoa)

A new term, “trophon”, has been introduced for the feeding and sexually propagating unit in the stolonate ctenostomes; the “stolon” and the “trophon” represent “sukzooids”, because they are homologous only to parts of the autozooids in the uniserially arranged ctenostomes. – The ontogeny of the muscles, especially the parietal muscles, has been studied in 17 species of ctenostomatous bryozoans belonging to different sub-groups of this order; the main effort was directed toward the details of the differentiations in living animals (14 of the investigated species). In various species of the Ctenostomata two separate sets of parietal muscles develop – probably as a consequence of the elongation of the cystid; the functional parietal muscles in the trophons of the stolonial forms are homologous to the secondary parietal muscles found in several uniserial ctenostomes. Contrary to the supposition by Soule (1954) in the different families of the serially arranged forms the muscles appear in different sequences during the development of the zooid and partly have different ontogenetical fates. Neither the “Carnosa” nor the “Paludicellea” (s. 1.) nor the “Stolonifera” can be maintained as taxa with the argument of a similar ontogeny of the muscles. A detailed comparison regarding the fate of the parietal muscles (and the polypide anlage) showed similarities between certain of the uniserial to either some of the stolonial, the sheet like, or the cystid-fusing forms suggesting a separate evolutionary origin of the advanced forms in those groups of the serially growing forms. – A new family, Pottsiellidae fam. nov., has been introduced and defined.     

The Occurrence of Bulbella abscondita (Bryozoa,Ctenostomata) in Brackish Waters of Northern Italy

The victorellid bryozoans, Tanganella muelleri and Bulbella abscondita, have been found in the delta of the River Po, Northern Italy. Our finds seem to be the first recorded of B. abscondita in waters in Italy.     

Organogenesis during budding and lophophoral morphology of Hislopia malayensis Annandale, 1916 (Bryozoa, Ctenostomata)

Background  

Bryozoans represent a large lophotrochozoan phylum with controversially discussed phylogenetic position and in group relationships. Developmental processes during the budding of bryozoans are in need for revision. Just recently a study on a phylactolaemate bryozoan gave a comprehensive basis for further comparisons among bryozoans. The aim of this study is to gain more insight into developmental patterns during polypide formation in the budding process of bryozoans. Particular focus is laid upon the lophophore, also its condition in adults. For this purpose we studied organogenesis during budding and lophophoral morphology of the ctenostome bryozoan Hislopia malayensis.     

Fine structure of the pharyngeal apparatus of the pelagosphera larva in Phascolosoma agassizii (Sipuncula) and its phylogenetic significance

Sipuncula is a small taxon of worm-like marine organisms of still uncertain phylogenetic position. Sipunculans are characterized by an unsegmented body composed of a trunk into which the anterior part, the introvert, can be withdrawn. The group has been placed at various positions within Metazoa; currently, it is either seen as sister group of a clade comprising Mollusca and Annelida or as sister to each of these. An in-group position in either Mollusca or Annelida has usually been precluded till now due to the lack of so-called annelid or molluscan “key-characters” such as segmentation and chaetae or the radula. In the development of certain taxa the trochophore stage is followed by a planktonic larva, the pelagosphera, which might exhibit phylogenetically important structures. Among these is the buccal organ, which has been considered homologous either to the ventral pharyngeal organ present in many sedentary polychaetes or to the radular apparatus of molluscs. In the present paper, the ventral pharynx of the pelagosphera larva of Phascolosoma agassizii is investigated by transmission electron microscopy. The pharynx comprises dorsolateral ciliary folds, a muscle bulb formed by transverse muscle fibres with large intercellular spaces, and an investing muscle. A tongue-like organ is lacking. These results show great structural correspondences to the ventral pharynx of polychaetes, especially to that of the flabelligerid Diplocirrus longisetosus. In contrast, there are no signs of structural similarities to the corresponding structures of molluscs. Thus evidence increases that Sipuncula are closely related to annelids; moreover, an in-group position of Sipuncula within Annelida, as suggested by recent molecular studies, is not precluded by the present data. Instead these studies find additional support. Hence the lack of segmentation and chitinous chaetae in Sipuncula would be a secondary rather than a primary situation, as has recently been shown for Echiura and Pogonophora.     

The egg, repagulum, and larva of Byas albistigma (Neuroptera: Ascalaphidae): morphology, behaviour and phylogenetic significance

Abstract The external morphology and habits of the larval instars of the Central American ascalaphid Byas albistigma (Walker) are described for the first time, and its eggs and repagula (abortive eggs) are compared to those of a Brazilian Byas sp. described by New (1971). In most respects, all immature stages of Byas are shown to be much like those of another neuroptyngine (entire-eyed) owlfly, Ascaloptynx furciger (McLachlan). However, larvae of Byas are arboreal rather than terrestrial and possess a number of important morphological characters that are more primitive than those seen in Ascaloptynx Shared features of the two genera that may constitute the ground plan of the Neuroptynginae are discussed in some detail and are weighted according to their primitive or derived status.     

Frontal organs in the Acoelomorpha (Turbellaria): Ultrastructure and phylogenetic significance

Using characters discernible through electron microscopy, we redefine the organ traditionally identified as the frontal organ in acoelomorph turbellarians as being a collection of two to several large mucus-secreting glands whose necks emerge together through a frontal pore at the exact apical pole of the body, i.e. at the point where the pattern of epidermal ciliary rootlets converges. Representatives that we have studied of each of the acoel families Paratomellidae, Diopisthoporidae, Solenofilomorphidae, Convolutidae, Otocelidae, and Mecynostomidae, as well as a representative of the Nemertodermatida, have such glands. Up to five additional types of glands that open anteriorly outside of the frontal pore, some of which are indistinguishable from glands of the general body wall, could be seen in the nemertodermatid, in Hesiolicium inops (Paratomellidae), and in representatives of the latter four acoel families. In Paratomella, three different types of glands open in diffuse fashion in a frontal glandular complex reminiscent of that in the Macrostomida.Sensory elements near the frontal pore appear to be independent of the gland necks, and so the organ cannot be considered a sensory organ.The frontal organ, as described above, appears very likely to be homologous within the Acoelomorpha, and represents another strong (although unrooted) autapomorphy for this line of turbellarian evolution.     

Anatomy and phylogenetic significance of Eoconularia loculata, a conulariid from the Silurian of Gotland

The type material of Eoconularia loculata (Wiman, 1895), a conulariid with high, bifurcated septa, was originally found in an erratic boulder, hence the source-rock is as yet unidentified. Recently, a rich material of the species has been discovered at eleven localities in the Silurian Hemse Beds of Gotland Another two localities in the Slite Beds (Wenlockan, Sheinwoodian) revealed what is assumed to be the ancestor of E loculata. This ancestral form probably constitutes a separate taxon distinguished from E. loculata in having simple, unbranched septa. E. loculata is re-described, and four ontogenetic stages in septal development are recognized. During stage 1, the most juvenile stage, the septa are simple. The septa in stages 3 and 4, the adult stages, are coarse and bifurcated. The affinities of conulariids are discussed, with the conclusion that the group shares a number of similarities with modem scyphomans. The microstructures of the exoskeleton show several similarities with coronatids, and the septa are interpreted to be homologous with the internal structures of stauromedusids. The stratigraphical distribution of all currently known septate conulariids suggests that septa were a primitive morphologic feature ranging from early? Ordovician to late Silurian. The simplest type, however, persisted at least into the early Permian. Five of the eleven described septa types have been found only among the conulariids from Gotland. □Conulariida, EOCONULARIA LOCULATA, bifurcated septa, taxonomy, ecology, morphology, Scyphozoa, Sweden, Gotland, Silurian.     

The settlement and metamorphosis of the marine bryozoan Bowerbankia gracilis (Ctenostomata: Vesicularioidea)

Summary The settlement and metamorphosis of the marine bryozoan Bowerbankia gracilis has been examined by light and electron microscopy. The period of rapid morphogenesis consists of the following sequence of morphogenetic movements: 1) eversion of the internal sac, 2) retraction of the apical disc, 3) coronal involution and exposure of the pallial epithelium, and 4) closure of the internal coronal cavity. The eversion of the internal sac at the onset of metamorphosis coincides with a sudden reversal of the direction of beat of the coronal cilia. The reversed beating of the coronal cilia wafts the adhesive secreted by the internal sac over the metamorphosing larva, forming the pellicle. The internal sac is subsequently internalized and histolyzed with the corona and the other transitory larval tissues, and the extensive pallial epithelium forms the epidermis of the ancestrular body wall (cystid). Type I mesenchyme cells form an incomplete somatic mesothelium beneath the differentiating cystid epidermis, and Type II mesenchyme cells become mobile phagocytes. The main body cavity develops by the histolytic enlargement of the internal cavity formed during coronal involution. The apical disc degenerates and the polypide develops from rudiments in the oral hemisphere of the larva. The distinctive larval morphology and metamorphosis of vesicularioid ctenostomes are compared with other bryozoans, and possible evolutionary trends are considered.     

Some British Phidoloporidae (Bryozoa: Gheilostomatida)

Five British species of Reteporella Busk, 1884 are described and figured. A neotype specimen is selected for R. beaniana (King), and R. incognita sp. nov. is described, and distinguished from R. couchii (Hincks).     

Electric organs in skates: Variation and phylogenetic significance (Chondrichthyes: Rajoidei)

A total of 63 species of skates (Chondrichthyes: Rajoidei) were surveyed, along with three species of the outgroup (Chondrichtyes: Rhinobatoidei) for electric organs along the sides of the tail. All skate specimens examined possessed what appeared to be functional electric organs, and the three species of the outgroup lacked evidence of electric organs. The electric organs were tail-positive and arranged into horizontal columns divided by transverse septa. The electrocytes varied considerably within and among supraspecific taxa (subgenera and genera), but they could be broadly classified into cup-shape, modified cup-shape, intermediate-shape, and disc-shape cells, provided that the distinction was partially based on position of the electrocytes within their connective tissue chambers. The survey, in part, corroborates a phylogenetic hypothesis of skates and in some respects further resolves the hypothesis. The supraspecific taxa Atlantoraja and Rioraja have similar derived-type electrocytes, as do the five supraspecific taxa of Rajini, and Cruriraja and Anacanthobatis, and to a lesser extent the supraspecific taxa Arhynchobatis, Psammobatis, and Sympterygia, and the supraspecific taxa Notoraja, Pavoraja, and Pseudoraja, corroborating the hypothesis. The supraspecific taxa Amblyraja, Rajella, Leucoraja, Breviraja, and Dactylobatus were unresolved in the phylogenetic hypothesis, but the electrocyte survey suggested that Leucoraja, Breviraja, and Dactylobatus were derived with respect to Amblyraja and Rajella. © 1994 Wiley-Liss, Inc.     

A new coptoclavid larva (Coleoptera: Adephaga: Dytiscoidea) from the Middle Jurassic of China,and its phylogenetic implication

Daohugounectes primitivus, a new genus and species of coptoclavid beetles, is described from 67 fossil larvae from the Jurassic locality of Daohugou, northeastern China. It differs from other coptoclavids in the combination of the following characters: lateral lobes of nasale present; legs relatively short, with tarsi flat and slightly dilated; abdominal tergite VIII almost circular; derivative of abdominal segment IX present; urogomphi short; and helical thickening of tracheae weak. Most of these features are plesiomorphic for the family Coptoclavidae and the superfamily Dytiscoidea. Among dytiscoids, a derivative of abdominal segment IX is present only in the larvae of the recently discovered relic family Aspidytidae.     

The female postabdomen of the enigmatic Nannochoristidae (Insecta: Mecopterida) and its phylogenetic significance

Hünefeld, F. and Beutel, R.G. 2011. The female postabdomen of the enigmatic Nannochoristidae (Insecta: Mecopterida) and its phylogenetic significance. —Acta Zoologica (Stockholm) 00: 1–8. External and internal features of the female postabdomen of Nannochorista neotropica are described in detail. The conditions found in females of Nannochoristidae come closest to the ground plan of Mecopterida. This lineage is characterised by telescoping postabdominal segments, a presumptive autapomorphic feature that is modified in some antliophoran groups, but displayed by the nannochoristid species in a typical manner. More potential autapomorphies of Mecopterida, all present in Nannochoristidae, are the neo‐formation of an intersegmental muscle, a transverse muscle spanning between the genital appendages of segment VIII, a muscle connecting these appendages and the genital chamber and the loss of an intersegmental muscle. Plesiomorphic features of Nannochoristidae are the presence of paired genital appendages on segments VIII and IX. Information on the egg‐depositing substrates of the females is not available. The telescoping postabdomen is suitable for oviposition in soft substrates such as moist soil, or rotten plant materials in the riparian zone, and this is possibly a ground‐plan feature of Mecopterida. The results of recent phylogenetic analyses based on morphological data support a placement of Nannochoristidae in Antliophora, whereas the exact position of the group remains ambiguous. No characters of the female postabdomen were found supporting the monophyly of Mecoptera as conventionally circumscribed, that is Nannochoristidae + Boreidae + Pistillifera.     

The larval morphology of the marine bryozoan Bowerbankia gracilis (Ctenostomata: Vesicularioidea)

Summary The larval morphology of the marine bryozoan Bowerbankia gracilis has been investigated by light and electron microscopy. The barrel-shaped larva (200 m long and 150 m in diameter) is light yellow without any apparent eyespots, although it is positively phototactic during its brief free-swimming existence. The primary morphological characteristics of the larva are: (1) a large corona that forms most of the larval surface, (2) a small apical disc without blastemas, (3) a deep pallial sinus lined by an extensive pallial epithelium, (4) an internal sac without regional specializations, and (5) a polypide rudiment in the oral hemisphere. This organization is characteristic of larvae of the ctenostome superfamily Vesicularioidea, and differs radically from the organization of all other bryozoan larvae examined. The major morphological differences occur in the size and organization of the apical disc, the pallial epithelium, and the internal sac. In most bryozoans, these regions of the larval epithelium represent rudiments of the polypide and the body wall epidermis of the ancestrula. The oral polypide rudiment, the extensive pallial epithelium, and the reduced internal sac in vesicularioid larvae indicate that their pattern of metamorphosis also differs radically from the metamorphoses of other bryozoans.Figure Abbreviations AB aboral - acr axial ciliary rootlet - ad apical disc - anc aboral nerve cord - ANT anterior - arm apical retractor muscle - b basal body - bf basal foot process - c corona - cc ciliated cleft - ce centriole - ci cilium - cl cupiform layer of the polypide rudiment - cp ciliary pit - cr ciliary rootlet - enr equatorial neural ring - g glandular cells of the pyriform organ - gl glycocalyx - go Golgi complex - gr granule - hcr horizontal ciliary rootlet - ic intercoronal cell - igf inferior glandular field - ip infrapallial cells - is internal sac - jp juxtapapillary cells - l lipid droplets - L lateral - m mesenchyme - m Type I mesenchyme cell - m Type II mesenchyme cell - m Type III mesenchyme cell - mb median band of the polypide rudiment - mc marginal cells of the apical disc - mi mitochondria - mr microridge - mv microvilli - nn nerve nodule - np neural plate - nu nucleus - O oral - oce oral ciliated epithelium - op opening to the internal sac - ovc oral vesicular collarette - p papilla of the pyriform organ - pa pallial cell - pe pallial epithelium - po pyriform organ - POS posterior - pp parasagittal patches of undifferentiated cells - pr polypide rudiment - rer rough endoplasmic reticulum - sc supracoronal cells - sg secretory granules - sgf superior glandular field - sp suprapallial cells - tc terminal cone - tf transitional filaments - u undifferentiated cells - va vacuole - vc vesicular cell - wc wedge-shaped cells of the apical disc - y yolk granule - za zonula adhaerens Caption Abbreviations Gp Glutaraldehyde-phosphate - Os Osmium     

The preoral cavity of lower Hymenoptera (Insecta): comparative morphology and phylogenetic significance

The skeletal and muscular morphology of the preoral cavity, including the labrum, hypopharynx and labium, was examined in the imago in representatives of all the ‘symphytan’ families as well as the apocritan families Stephanidae, Megalyridae and Trigonalyidae. Xyelidae have complex modifications for masticating pollen, remarkably similiar to those of primitive Lepidoptera. These modifications, collectively termed the triturating basket complex, include an asymmetrical distal epipharyngeal wall with a microtrichial brush and an enlarged infrabuccal pouch with heavy cuticular armature that interacts with the mandibles during feeding. There were striking structural differences between the two subfamilies of Xyelidae in the ligular region; the reduced glossa and clubshaped paraglossae of Macroxyelinae resembles those of primitive Lepidoptera, while the well developed, flattened glossa and paraglossae in Xyelidae are similiar to those of most other ‘Symphyta’. A putative transformation series, leading from a relatively large labrum with unsclerotised distal epipharyngeal wall lying anterior to the mandibles, as seen in Xyelidae and enthredinoidea, to a small and heavily sclerotised labrum and distal epipharyngeal wall lying posterior to the mandibles, as seen in ‘Siricoidea’, Orussidae and the Apocrita, was revealed. These modifications may be adaptations to enable the adult of the families pupating in wood to emerge from the pupal chamber. The Anaxyelidae, Orussidae and Apocrita have similiar configurations of the glossa and nsertions of the ventral premental adductors. This indicates a close affinity of the Anaxyelidae to Orussidae + Apocrita, a hypothesis that is in conflict with other character systems. The Orussidae and Stephanidae share a unique condition in the development of a pair of large apodemes attached to the labrum; this renders the groundplan state of the labrum in the Apocrita uncertain. Twentyfive characters were defined in an attempt to eludicate the ‘Symphyta’–Apocrita transition. A numerical cladistic analysis of the characters was undertaken, resulting in 522 minimum length trees. The characters are also discussed with reference to a cladogram which resulted from an analysis of the characters derived from the present study and a survey of characters from literature.     

Anatomy and ultrastructure of ventral pharyngeal organs and their phylogenetic importance in Polychaeta (Annelida)

Summary A comparative anatomical and ultrastructural study of ventral pharyngeal organs (pharyngeal bulbs) was carried out in two species of the Dinophilidae: Dinophilus gyrociliatus and Trilobodrilus axi. Special attention was paid to the fine structure of the stomodeal epithelium, cuticle, glands, muscles, and myoepithelial junctions. The differences between the species are very slight. The pharyngeal organ of the Dinophilidae is characterized by the following features: solid muscle bulbus made up of muscle cells only, bulbus muscle cells with two myofilament systems crossing at an angle of about 90°, gap junctions between these muscle cells, bulbus projects into a pharyngeal sac and bears rostrally a specific epithelium and cuticle, no bulbus glands, no investing (= sagittal) muscles, specific cuticle ultrastructure, cilia of ascending oesophagus with asymmetric tips, specific structure and position of salivary gland openings. The phylogenetic importance of these structures is discussed. Some of these characters are clearly autapomorphic features of the Dinophilidae and no common derived structures to other families with a ventral pharyngeal organ are present. Therefore, it is most likely that the dinophilid pharyngeal organ evolved independently. These findings do not agree with the hypothesis of the unity of the archiannelid families (Polygordiidae, Protodrilidae, Saccocirridae, Nerillidae, Dinophilidae, and Diurodrilidae) established on the basis of an assumed structural similarity of their ventral pharyngeal organs.Abbreviations bb basal body - bep bulbus epithelium - bl basal lamina - bm bulbus muscle - c cilium - cc coelenchyme cell - cm circular muscle - cr caudal rootlet - cu cuticle - dblm dorsal bulbus longitudinal muscle - dlm dorsal longitudinal muscle - dsn dorsal stomatogastric nerve - dy dyad - el electron-dense layer - fl fibrous layer - fi filaments - g Golgi apparatus - gl gland cell - hv homogeneous vesicle - l lipid droplet - la external lamina - lal lamellar layer - ll lower lip - lm longitudinal muscle - ly lysosome - m mitochondrion - mo mouth opening - mt microtubule - mv microvillus - mvp microvillar process - n nucleus - nu nucleolus - oes oesophagus - pcom preoral commissure - phf pharyngeal fold - phl pharyngeal lumen - phs pharyngeal sac - pms peripheral myofilament system - r rootletlike structure - rer rough endoplasmic reticulum - rr rostral rootlet - s sarcoplasmic reticulum - sc salivary canal - scom suboesophageal commissure - sd septate desmosome - ser smooth endoplasmic reticulum - sg secretory granule - sgl salivary gland - sn stomatogastric nerve - st stomach - step stomodeal epithelium - tep transitional epithelium - tf tonofilaments - va vacuole - vlm ventral longitudinal muscle - vsn ventral stomatogastric nerve - z z-element - za zonula adherens     

The spermatozoon of the Echiniscidae (Tardigrada,Heterotardigrada) and its phylogenetic significance

The spermatozoon ultrastructure of four species of moss-dwelling Heterotardigrada belonging to four genera of Echiniscidae, namely Pseudechiniscus juanitae, Echiniscus duboisi, Novechiniscus armadilloides and Antechiniscus parvisentus, was investigated. In all species, the testicular male gamete is similar in morphology and in length. The spermatozoon is made up of a long head, consisting of a cylindrical acrosome and an oval or rod-shaped nuclear region which contains a nucleus with osmiophilic and electron-dense chromatin, and a tapering tail, with a "9+2" axoneme. An elongated sack-like structure originates from the posterior part of the head, extending beyond the main axis of the cell and running parallel to the tail. It consists of two parallel tubular regions which sometimes form a strict double helix and contain two voluminous, "free" mitochondria with unmodified cristae. In addition, a voluminous vesicle is present laterally to the centriole or between the end of the nucleus and the beginning of the mitochondria, limited by two cytomembranes and filled with electron-lucent and granular material. The male gametes representative of these moss-dwelling Echiniscidae are very similar to the spermatozoa of the marine Echiniscoididae Echiniscoides sigismundi. This close similarity emphasises that habitat changes have had little influence on the organisation of the sperm cell representative of Echiniscoidea. Spermatozoon characters which could be useful for phylogenetic studies on Tardigrada are discussed.