New archaeogastropod limpets from hydrothermal vents; Superfamily Lepetodrilacea. II. Anatomy

1988 ◽  
Vol 319 (1192) ◽  
pp. 33-82 ◽  
Keyword(s):  
Hydrothermal Vents ◽  
Mantle Cavity ◽  
Visceral Mass ◽  
Origin And Evolution ◽  
Mode Of Life ◽  
Receptaculum Seminis ◽  
The Right ◽  
High Degree ◽  
Narrow Section ◽  
System Approaches

The anatomy of nine species (two genera) of lepetodrilacean limpets is described and the mode of life deduced therefrom. The unique action of the odontophore sets them apart from all prosobranchs yet known: its initial ventral movement is all but suppressed and the dorsal movement, before withdrawal, exaggerated. This action is facilitated by the freedom of the odontophore from the restraining action of the snout which is controlled by special cephalic levator and retractor muscles. Evidence indicates that the jaws are used as scrubbers, loosening particles from the substratum over the animal’s head which are then collected by the specialized rhipidoglossate radula. This is the only method of feeding in the more primitive of the two genera, Gorgoleptis , in which the possession of a metapodium with an operculum indicates that the transformation to the limpet form is incomplete. All members of the superfamily have a single left gill typically bilamellate and with a pectiniform skeleton. The dorsal (left) lamellae are reduced in number and size, particularly in Lepetodrilus (lost in Lepetodrilus ovalis ), and the ventral (right) ones exaggerated and their numbers increased with the enlargement of the mantle cavity. Although the ciliary bands on the lamellae of Lepetodrilus are as in other prosobranchs, at the tips of the lamellae the frontals and abfrontals expand to form pads and the laterals encircle the tips between them. This unusual modification relates to suspension feeding: the two methods of feeding may proceed concurrently. The nervous system has a high degree of fusion of the postcephalic ganglia. The pedal ganglia are large, their short commissure continuous with a pleural commissure, and the supra- and suboesophageal ganglia are contiguous with the right and left pleurals respectively. Nerves to the mantle and foot are compound. The epipodium is well developed, confined to the region of the foot in Gorgoleptis and with elongated tentacles, but spreading on to the head and forming a fold surrounding the base of each cephalic tentacle in Lepetodrilus , which has shorter tentacles round the foot; cilia on the right cephalic fold pass particulate matter from the mantle cavity to the mouth. The penis of Lepetodrilus is also of epipodial origin as opposed to its development from the left side of the snout in Gorgoleptis. In both genera a right pallial tentacle is associated with the exhalant passage from the mantle cavity, though this is greatly reduced in Lepetodrilus . The shell of Gorgoleptis species indicates that these limpets have followed a different evolutionary course from that of Lepetodrilus in that the columellar lip remains as an integral part of the peristome. In species of both genera the mantle edge has two folds, the inner probably represents the fusion of the inner and middle folds of zeugobranch limpets: the remoteness of the periostracal and shell secreting areas results in an inturned band of periostracum particularly broad in Lepetodrilus species. In each, the shell muscle is approximately bilaterally symmetrical, but details of its constituent parts, pedal and pallial, differ. In addition to the bilamellate gill and epipodium, the alimentary, circulatory, nervous and excretory systems indicate that relationships are at the archaeogastropod level. Although similar to the trochaceans, these limpets differ from them in a number of respects. The reproductive system approaches that of monotocardians in the length of the gonadial duct, which in the male is a vesicula seminalis; in the separation of that part of the right kidney through which gametes pass to the urinogenital opening; in the presence of a prostate and penis in the male, and in the female Lepetodrilus of a receptaculum seminis. The female has no hypertrophied pallial oviduct, and eggs with no secondary investments are apparently fertilized in the mantle cavity, and then shed. Although the anatomy of Neomphalus indicates that it had a different origin and evolution from the more conservative lepetodrilaceans, all these prosobranchs share a common characteristic in the attainment of the limpet form by having a narrow section between the enlarged head and the visceral mass marked by the end of the oesophageal pouches and tight chiastoneury.

scholarly journals Observations on the opisthobranch mollusc Acteon tornatilis (L.).

1954 ◽  
Vol 33 (3) ◽  
pp. 565-585 ◽  
Author(s):  
Vera Fretter ◽  
Alastair Graham
Keyword(s):  
Salivary Glands ◽  
Reproductive System ◽  
Vas Deferens ◽  
Buccal Cavity ◽  
Mantle Cavity ◽  
Water Current ◽  
Male And Female ◽  
Receptaculum Seminis ◽  
The Right ◽  
Labial Glands

SummaryActeon tornatilis is an opisthobranch mollusc which burrows in sand, using foot, labial and cephalic tentacles in the process. The last also help to exclude sand from the mantle cavity, which is extended into a caecum coiling alongside the visceral hump, presumably used for respiration but also for excretion. The main pallial water current is an exhalant one on the right.The mantle skirt carries, on the left, numerous repugnatorial glands with toxic secretions.Labial glands lie at the mouth and the buccal cavity contains jaws and a reduced buccal mass and radula. Into it open salivary glands the structure of which is like that of the pyramidellids. The oesophagus shows traces neither of glands nor of torsion whereas the stomach, though simplified, has resemblances to that of a prosobranch.The reproductive system is shown to be different from previous descriptions. Male and female ducts are separate from the lower end of the little hermaphrodite duct. The former passes to a prostate from which a vas deferens leads to a large uninvaginable penis; the latter has associated albumen and mucous glands and there is a receptaculum seminis to the duct of which a ventral channel leads from the female aperture in the mantle cavity.Discussion of these aspects of the animal's structure confirms its position as the most primitive of the opisthobranchs.

The functional anatomy of the mantle complex and columellar muscle of tectibranch molluscs (Gastropoda: Opisthobranchia), and its bearing on the evolution of opisthobranch organization

1977 ◽  
Vol 277 (951) ◽  
pp. 1-56 ◽  
Keyword(s):  
Water Flow ◽  
Body Wall ◽  
General Pattern ◽  
Large Body ◽  
Mantle Cavity ◽  
The Body ◽  
Differential Growth ◽  
Visceral Mass ◽  
Mantle Edge ◽  
The Right

An account is given of the anatomy of a series of opisthobranch molluscs principally to assess the change in importance and functioning of the mantle cavity and columellar muscle throughout the transition from prosobranch to opisthobranch organization. Intermediate steps are represented by living tectibranchs, of which Philine and Scaphander are investigated in detail, Acteon, Bulla, Haminoea, Akera, Aglaja and Gastropteron more briefly. Though an opisthobranch, Acteon has an organization typical of a monotocardian prosobranch; the remainder show trends affecting the shell and visceral mass, mantle cavity and head-foot, which resulted finally in the production of nudibranch types. It is confirmed that the adaptations exhibited by primitive tectibranchs relate to the assumption of a burrowing mode of life. Initial changes were the reduction of the nuchal area and sealing of the mantle cavity anteriorly so that it opened on the right, where it became restricted, the first perhaps prompting the sealing. A broadening and an anterior elongation of the head-foot produced a wedge to facilitate burrowing. Change in disposition of the mantle edge, incurred by differential growth, produced an involute shell with a large body whorl, alignment changing from erect to horizontal. The resultant streamlining eased infaunal progression; no vertical insinking of the viscera was involved. Subsequently the shell became reduced and finally lost. A section of the mantle edge enlarged to produce a posterior mantle lobe upon which sit both the shell and viscera, and which later became redundant as posterior elongation of the head-foot produced a slug-like form, the viscera being incorporated within the head-foot. As the nuchal area became reduced, mechanical needs prompted alteration to both the form and attachment of the columellar muscle. In Acteon the muscle is like that of a prosobranch, but the proximal region has broadened, a change of proportion required by primitive tectibranchs in order to support the floor of the mantle cavity formed from the section of mantle skirt which in prosobranchs lies on the right. This was followed by reduction and re-alignment of the entire muscle along an anteroposterior axis as emphasis changed from the muscle effecting retraction into a shell to producing contorsions of the head-foot. The shell, similarly reduced, instead of providing anchorage, became itself anchored by additional anterior and posterior attachment zones with, in more advanced forms, dorsoventral muscles of the body wall rather than longitudinal muscles fastening to the former. Importance was placed on the mutual stabilization of constituent parts of the posterior body region. Re-alignment of the muscle induced breaking up of the longitudinal muscle sheet of the head-foot to produce muscle tracts, best exhibited in those tectibranchs which swim; they are derived from both the columellar muscle and intrinsic body wall muscles. In advanced opisthobranchs, the importance of the columellar muscle progressively diminishes and it is finally lost in the adult. The mantle cavity shallowed, partially due to lack of space on the right where the mantle abuts against the viscera, but principally to avoid instability of its walls. Without support the walls will, especially in larger animals, tend to collapse owing to the restricted inhalant flow of water caused by the absence of an effective siphon and the adverse infaunal conditions. The floor may tend perhaps to be pushed laterally by increases in pressure within underlying haemocoelic spaces. Tensor muscles arose to stabilize the floor, for this became distinct from the thickened mantle edge represented by the posterior mantle lobe, and viscera were interpolated between the inner surfaces of the two regions of this section of the mantle skirt. The separation of surfaces was a consequence of the creation of space posteriorly by reduction of the nuchal area, shell and proximal columellar muscle, all adaptations to produce a slug-like form; the first was the most important at an early stage in evolution, the latter two at a later stage. There is no evidence that any tensor muscle is derived from the columellar muscle It is suggested that the first opisthobranchs were small, a feature which almost certainly favoured colonization of the infaunal niche, and lacked a gill, water flow being produced by ciliated bands as in various small gastropods. Upon a subsequent increase in size, a gill of different pattern to the prosobranch ctenidium evolved which is not important in producing water flow. The pallial caecum is a further respiratory innovation to offset functional inefficiencies which might otherwise have been incurred upon the increase in size which was undertaken under conditions of poor ventilation. Respiratory exchange was also facilitated by fusion of the pallial caecum to the visceral mass ( Philine, Aglaja, Akera ), which also enabled tensor muscles to attach to and stabilize its floor. In Philine , the roof also is stabilized by areas which adhere to the shell thereby ensuring that this caecum is always fully open. Discussion of both the mantle complex and columellar muscle indicates a high incidence of parallelism. It is suggested that the term detorsion be discarded. No rotation of the mantle skirt took place, but differential growth followed by folding to which the term posterior migration has been applied. Discussion of developmental studies indicates that torsion in opisthobranchs is halted at a stage which approximately corresponds to the position of the mantle complex in the adult, and in more advanced forms torsion is essentially abolished. The final changes leading to the assumption of the nudibranch condition, and the phylogenetic interrelations of the animals investigated are briefly discussed. It is concluded that the general pattern of opisthobranch evolution was one of initial assumption of infaunal life, followed, after varying intervals of time, by return to the surface; only a few groups, of which the Philinidae are a good example, have fully exploited the infaunal niche.

THE DEVELOPMENT OF RETUSA OBTUSA (MONTAGU) (GASTROPODA, OPISTHOBRANCHIA)

1967 ◽  
Vol 45 (5) ◽  
pp. 737-764 ◽  
Author(s):  
S. Tyrell Smith
Keyword(s):  
Mantle Cavity ◽  
Direct Development ◽  
Visceral Mass ◽  
Adult Kidney ◽  
Organ Systems ◽  
Embryonic Shell ◽  
Planktonic Phase ◽  
Egg Membrane ◽  
The Right ◽  
Digestive Glands

The development of Retusa obtusa (Montagu 1803) from uncleaved egg to hatching is described. Cleavage is spiral and holoblastic, and results in the formation of a stereoblastula. Gastrulation occurs partly by epiboly and partly by invagination. The veliger form is assumed within the egg membrane: the velar lobes and cilia are comparatively less well developed than those of planktonic veligers.The foregut is ectodermal in origin, whereas the hindgut is almost entirely endodermal. The larval midgut diverticula give rise directly to the adult digestive glands. The left diverticulum is larger than the right from the first. A coelom, of the type described by Saunders and Poole (1910) for Aplysia, is not present at any stage in the development of Retusa. Hatching occurs approximately 28 days (at 12 °C) after oviposition. Development is direct.The alimentary canal and nervous system show some evidence of torsion; but this asymmetry is present from the first appearance of these organ systems, and no torsional process per se is detectable in. development. No jaws or radula are present in Retusa. At hatching, the heart and adult kidney are well developed. The embryonic kidney degenerates. The larval musculature degenerates and plays no part in the formation of the adult musculature. The mantle cavity spreads posteriorly, so that the heart and kidney come to tie within the suprapallium.The conclusion reached is that the trend toward loss of genetic torsion in the opisthobranchia has advanced further in Retusa than in Aplysia (Saunders and Poole 1910). Hyperstrophy of the embryonic shell is attributed to deformation of the visceral mass by the enlarged left midgut diverticulum, before evagination of the shell gland has taken place. There has been no previous record of direct development for a shelled opisthobranch. Comparisons are made with R. truncatula, which has an obligatory planktonic phase in its life history. It is concluded that the acquisition of direct development by R. obtusa is connected with the small size of the adult animal and with its northerly range.

scholarly journals The Genital Ducts of Theodoxus, Lamellaria and Trivia, and a Discussion on their Evolution in the Prosobranchs

1946 ◽  
Vol 26 (3) ◽  
pp. 312-351 ◽  
Author(s):  
Vera Fretter
Keyword(s):  
Vas Deferens ◽  
Mantle Cavity ◽  
Genital Duct ◽  
The Right ◽  
Narrow Section ◽  
Sex Cells

The prosobranchiate gastropods are divided into three orders, the Archaeogastropoda, the Mesogastropoda and the Stenoglossa. In the first of these groups the gonad is connected with the right kidney by a duct which is developed from the ovary, and the sex cells escape to the posterior end of the mantle cavity through the right ureter. The eggs are usually shed singly into the sea where fertilization occurs. In the Mesogastropoda and Stenoglossa the right kidney is not developed and the ovarian duct leads to a short and narrow section of the genital duct which is typically ciliated, and may communicate with the pericardium by a gonopericardial duct and passes anteriorly to a long glandular tract running forwards to the mouth of the mantle cavity. This glandular section is incipient in the archaeogastropod Calliostoma zizyphinum. It is probably formed, as Thiele (1935) suggests, by an ectodermal intucking and will be referred to as the pallial oviduct, for it lies anterior to the opening of the original right kidney, and must be derived from the ectoderm of the mantle (Bourne, 1908; Giese, 1915). The short duct which links it with the ovarian duct will be termed the renal oviduct: in Paludina (=Viviparus), in which its development has been investigated (Drummond, 1903), it is formed from the vestige of the right kidney, and even in the highly specialized Stenoglossa it retains the connexion with the pericardium which is characteristic of the right and left kidneys of the archaeogastropods. Similarly, in the male system of the Mesogastropoda and Stenoglossa there can be distinguished a testis duct, which is connected to the posterior end of the mantle cavity by a renal vas deferens, and this in turn is followed by a pallial vas deferens.

scholarly journals Challenges and Controversies in the Genetic Diagnosis of Hereditary Spastic Paraplegia

2021 ◽  
Vol 21 (4) ◽  
Author(s):  
Lydia Saputra ◽  
Kishore Raj Kumar
Keyword(s):  
Genetic Diagnosis ◽  
Spastic Paraplegia ◽  
Limb Weakness ◽  
Hereditary Spastic Paraplegias ◽  
Gene Testing ◽  
Testing Strategies ◽  
Whole Exome ◽  
The Right ◽  
Gene Panels ◽  
High Degree

Abstract Purpose of Review The hereditary spastic paraplegias (HSPs) are a group of disorders characterised by progressive lower limb weakness and spasticity. We address the challenges and controversies involved in the genetic diagnosis of HSP. Recent Findings There is a large and rapidly expanding list of genes implicated in HSP, making it difficult to keep gene testing panels updated. There is also a high degree of phenotypic overlap between HSP and other disorders, leading to problems in choosing the right panel to analyse. We discuss genetic testing strategies for overcoming these diagnostic hurdles, including the use of targeted sequencing gene panels, whole-exome sequencing and whole-genome sequencing. Personalised treatments for HSP are on the horizon, and a genetic diagnosis may hold the key to access these treatments. Summary Developing strategies to overcome the challenges and controversies in HSP may hold the key to a rapid and accurate genetic diagnosis.

The Right to Repair Goods in the Era of Digitalization and Globalization

2021 ◽  
Vol 16 (12) ◽  
pp. 45-52
Author(s):  
P. L. Likhter
Keyword(s):  
Circular Economy ◽  
Medical Equipment ◽  
Environmental Safety ◽  
Spare Parts ◽  
Service Organizations ◽  
Warranty Period ◽  
Market Participants ◽  
The Right ◽  
High Degree

Today, large companies are increasingly using controversial strategies related to the violation of the buyer’s rights to repair the goods both during and after the expiration of the warranty period. This is primarily manifested in the restriction of access to the necessary information on the product repairing, hindering the work of independent service organizations, intentional complication of parts during their design, unreasonably high degree of integration of units, lack of a sufficient number of spare parts on the market, etc. As a rule, such actions distort the principles of integrity and transparency, which, in turn, entails risks to consumer and environmental safety. This issue is of particular relevance in the context of the COVID-19 pandemic, when sellers of medical equipment restrict the possibility of its restoration by independent specialists, and also prevent the distribution of the necessary software. Based on the results of the work, it is concluded that it is advisable to establish boundaries for the conduct of market participants to stimulate the production of durable and maintainable goods in order to transit to a circular economy.

scholarly journals Origin, Traject and Distribution of Renal Arteries (Arteriae renalis) in Chinchilla lanigera

2018 ◽  
Vol 75 (1) ◽  
pp. 129
Author(s):  
Cristian MARTONOS ◽  
Cristian DEZDROBITU ◽  
Florin STAN ◽  
Aurel DAMIAN ◽  
Alexandru GUDEA
Keyword(s):  
Renal Artery ◽  
Renal Arteries ◽  
Left Renal Artery ◽  
Lateral Part ◽  
Formaldehyde Solution ◽  
Anatomical Dissection ◽  
The Right ◽  
High Degree ◽  
Aorta Abdominalis ◽  
Degree Of Similarity

For the present study a number of 5 female chinchilla carcasses were used. The animals were slaughtered for commercial purpuses (fur). The anatomical dissection started with the identification of the aorta (Aorta abdominalis). The next step was the intra-arterial injection of a colouring substance. The carcasses was fixed in the formaldehyde solution and subsequently the renal arteries were dissected. The first renal artery was the right renal artery (Arteria renalis dextra) and, at 0,5 cm caudally, the left renal artery (Arteria renalis sinister) arose . The origin of those arteries were disposed on the lateral part of the abdominal aorta.The origin, traject and distribution of renal arteries on the studied species have a high degree of similarity with the literature dates described for leporids.

scholarly journals Coupling of Bacterial Endosymbiont and Host Mitochondrial Genomes in the Hydrothermal Vent Clam Calyptogena magnifica

2003 ◽  
Vol 69 (4) ◽  
pp. 2058-2064 ◽  
Author(s):  
Luis A. Hurtado ◽  
Mariana Mateos ◽  
Richard A. Lutz ◽  
Robert C. Vrijenhoek
Keyword(s):  
Dna Sequences ◽  
Hydrothermal Vent ◽  
Hydrothermal Vents ◽  
Nuclear Gene ◽  
Sexual Population ◽  
Origin And Evolution ◽  
Bacterial Endosymbionts ◽  
Sulfur Oxidizing ◽  
Tight Association ◽  
Clam Population

ABSTRACT The hydrothermal vent clam Calyptogena magnifica (Bivalvia: Vesicomyidae) depends for its nutrition on sulfur-oxidizing symbiotic bacteria housed in its gill tissues. This symbiont is transmitted vertically between generations via the clam's eggs; however, it remains uncertain whether occasionally symbionts are horizontally transmitted or acquired from the environment. If symbionts are transmitted strictly vertically through the egg cytoplasm, inheritance of symbiont lineages should behave as if coupled to the host's maternally inherited mitochondrial DNA. This coupling would be obscured, however, with low rates of horizontal or environmental transfers, the equivalent of recombination between host lineages. Population genetic analyses of C. magnifica clams and associated symbionts from eastern Pacific hydrothermal vents clearly supported the hypothesis of strictly maternal cotransmission. Host mitochondrial and symbiont DNA sequences were coupled in a clam population that was polymorphic for both genetic markers. These markers were not similarly coupled with sequence variation at a nuclear gene locus, as expected for a randomly mating sexual population. Phylogenetic analysis of the two cytoplasmic genes also revealed no evidence for recombination. The tight association between vesicomyid clams and their vertically transmitted bacterial endosymbionts is phylogenetically very young (<50 million years) and may serve as a model for the origin and evolution of eukaryotic organelles.

scholarly journals The structure of the sedimentary complex of the Middle and South Caspian depressions (Azerbaijan sector)

2021 ◽  
Vol 43 (4) ◽  
pp. 199-216
Author(s):  
N.P. Yusubov ◽  
I.S. Guliyev
Keyword(s):  
Seismic Data ◽  
Oil And Gas ◽  
Sedimentary Cover ◽  
Clay Content ◽  
Geological Structure ◽  
Point Of View ◽  
South Caspian Basin ◽  
Origin And Evolution ◽  
Geological Interpretation ◽  
High Degree

The high degree of knowledge of the upper horizons of the sedimentary cover of the Middle and South Caspian depressions, given an insufficient increase in hydrocarbon reserves, leads to the need for a detailed approach to the search for oil and gas deposits in deep-seated sediments (over 6 km). During the geological interpretation of new highly informative seismic data, as well as data of deep drilling and petrological core studies, there were revealed obvious shortcomings in the concepts of the origin and evolution of the Middle and South Caspian depressions. These ideas misinterpret evolution, especially the South Caspian Basin, which is characterized by a number of unique features: very thick sedimentary cover (up to 22 km), extremely high sedimentation rate, low heat flow and reservoir temperatures, abnormally high pore and reservoir pressures, high clay content of the section, etc. The main purpose of the study was to elucidate the regional structure and features of the dissection of the sedimentary cover of the Middle and South Caspian depressions, the conditions of occurrence and distribution of facies and thicknesses of individual complexes of deposits. The paper analyzes the results of some previous studies of the geological structure of the Middle and South Caspian depressions based on the data of deep seismic sounding, seismological and gravimetric observations. We consider the main conclusions of these studies, about the geological structure of the sedimentary complex of the region’s, very outdated and subject to revision. The results of seismic stratigraphic analysis of seismic data allowed the authors to identify new data about the tectonic structure and express a completely different point of view regarding the structure of the sedimentary cover in the region. The work also touches on the issue associated with the tectonics of the region and the alleged subduction zone here.

scholarly journals Subjective Experience of Speech Depending on the Acoustic Treatment in an Ordinary Room

2021 ◽  
Vol 18 (23) ◽  
pp. 12274
Author(s):  
Emma Arvidsson ◽  
Erling Nilsson ◽  
Delphine Bard-Hagberg ◽  
Ola J. I. Karlsson
Keyword(s):  
Speech Perception ◽  
Subjective Experience ◽  
Sound Quality ◽  
Reverberation Time ◽  
Acoustic Environment ◽  
Acoustic Environments ◽  
The Right ◽  
Acoustic Treatment ◽  
High Degree ◽  
Speech Clarity

In environments such as classrooms and offices, complex tasks are performed. A satisfactory acoustic environment is critical for the performance of such tasks. To ensure a good acoustic environment, the right acoustic treatment must be used. The relation between different room acoustic treatments and how they affect speech perception in these types of rooms is not yet fully understood. In this study, speech perception was evaluated for three different configurations using absorbers and diffusers. Twenty-nine participants reported on their subjective experience of speech in respect of different configurations in different positions in a room. They judged sound quality and attributes related to speech perception. In addition, the jury members ranked the different acoustic environments. The subjective experience was related to the different room acoustic treatments and the room acoustic parameters of speech clarity, reverberation time and sound strength. It was found that people, on average, rated treatments with a high degree of absorption as best. This configuration had the highest speech clarity value and lowest values for reverberation time and sound strength. The perceived sound quality could be correlated to speech clarity, while attributes related to speech perception had the strongest association with reverberation time.

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