scholarly journals Ultrastructure of the ciliated cells of the free-swimming larva, and sessile stages, of the marine spongeHaliclona indistincta(Demospongiae: haplosclerida)

2013 ◽  
Vol 274 (11) ◽  
pp. 1263-1276 ◽  
Author(s):  
Kelly M. Stephens ◽  
Alexander Ereskovsky ◽  
Pierce Lalor ◽  
Grace P. McCormack
Keyword(s):  
Ciliated Cells ◽  
Free Swimming ◽  
Swimming Larva ◽  
Free Swimming Larva

scholarly journals Intergenerational transmission of symbiotic bacteria in oviparous and viviparous demosponges, with emphasis on intracytoplasmically-compartmented bacterial types

2007 ◽  
Vol 87 (6) ◽  
pp. 1701-1713 ◽  
Author(s):  
Manuel Maldonado
Keyword(s):  
Microbial Communities ◽  
Symbiotic Bacteria ◽  
Free Swimming ◽  
Transmission Electron ◽  
Early Embryos ◽  
Membrane Bound ◽  
Chondrilla Nucula ◽  
New Generation ◽  
Swimming Larva ◽  
Free Swimming Larva

Recent molecular detection of vast microbial communities exclusively associated with sponges has made evident the need for a better understanding of the mechanisms by which these symbiotic microbes are handled and transferred from one sponge generation to another. This transmission electron microscopy (TEM) study investigated the occurrence of symbiotic bacteria in free-swimming larvae of two viviparous species (Haliclona caerulea and Corticium candelabrum) and spawned gametes of two oviparous species (Chondrilla nucula and Petrosia ficiformis). Complex microbial communities were found in these sponges, which in two cases included bacteria characterized by an intra-cytoplasmic membrane (ICM). When ICM-bearing and ICM-lacking bacteria co-existed, they were transferred following identical pathways. Nevertheless, the mechanism for microbial transference varied substantially between species. In C. nucula, a combination of intercellular symbiotic ICM-bearing and ICM-lacking bacteria, along with cyanobacteria and yeasts, were collected from the mesohyl by amoeboid nurse cells, then transported and transferred to the oocytes. In the case of Corticium candelabrum, intercellular bacteria did not enter the gametes, but spread into the division furrows of early embryos and proliferated in the central cavity of the free-swimming larva. Surprisingly, symbiotic bacteria were not vertically transmitted by P. ficiformis gametes or embryos, but apparently acquired from the environment by the juveniles of each new generation. This study failed to unravel the mechanism by which the intercellular endosymbiotic bacterium found in the central mesohyl of the H. caerulea larva got there. Nevertheless, the ultrastructure of this bacterial rod, which was characterized by a star-shaped cross section with nine radial protrusions, an ICM-bound riboplasm, and a putative membrane-bound acidocalcisome, suggested that it may represent a novel organization grade within the prokaryotes. It combines traits occurring in members of Poribacteria, Planctomycetes and Verrucomicrobia, emerging as one of the most complex prokaryotic architectures known to date.

The Vortex Wake of the Free-swimming Larva and Pupa of CULEX PIPIENS (Diptera)

2001 ◽  
Vol 204 (11) ◽  
pp. 1855-1867 ◽  
Author(s):  
John Brackenbury
Keyword(s):  
Reynolds Numbers ◽  
High Amplitude ◽  
The Body ◽  
Ring Vortex ◽  
Free Swimming ◽  
Continuous Surface ◽  
The Mean ◽  
Swimming Larva ◽  
Free Swimming Larva ◽  
Visualisation Technique

SUMMARY The kinematics and hydrodynamics of free-swimming pupal and larval (final-instar) culicids were investigated using videography and a simple wake-visualisation technique (dyes). In both cases, swimming is based on a technique of high-amplitude, side-to-side (larva) or up-and-down (pupa) bending of the body. The pupa possesses a pair of plate-like abdominal paddles; the larval abdominal paddle consists of a fan of closely spaced bristles which, at the Reynolds numbers involved, behaves like a continuous surface. Wake visualisation showed that each half-stroke of the swimming cycle produces a discrete ring vortex that is convected away from the body. Consecutive vortices are produced first to one side then to the other of the mean swimming path, the convection axis being inclined at approximately 25° away from dead aft. Pupal and larval culicids therefore resemble fish in using the momentum injected into the water to generate thrust. Preliminary calculations for the pupa suggest that each vortex contains sufficient momentum to account for that added to the body with each half-stroke. The possibility is discussed that the side-to-side flexural technique may allow an interaction between body and tail flows in the production of vorticity.

Experiments on host-finding and host-specificity in the monogenean skin parasite Entobdella soleae

Parasitology ◽  
1967 ◽  
Vol 57 (3) ◽  
pp. 585-605 ◽  
Author(s):  
G. C. Kearn
Keyword(s):  
Host Specificity ◽  
Host Finding ◽  
Free Swimming ◽  
Solea Solea ◽  
Specific Substance ◽  
The Common ◽  
Mucus Cells ◽  
Common Sole ◽  
Swimming Larva ◽  
Free Swimming Larva

The oncomiracidium of the monogenean skin parasite Entobdella soleae finds its flatfish host, Solea solea, by chemoreception. The free-swimming larva responds to a specific substance secreted by the skin of the common sole, attaches itself to this skin and immediately sheds its ciliated epidermal cells. Larvae respond in the same way to agar jelly which has been in contact with the skin of S. solea.The oncomiracidia attach to S. solea skin in preference to that of other soleid fishes (Buglossidium luteum and Solea variegata), pleuronectid fishes (Limanda limanda, Pleuronectes platessa) and elasmobranch flatfishes (Raia spp.).Larvae respond strongly to isolated epidermis from Solea solea but show no response to the fish's cornea, indicating that the attractive substance is produced by the mucus cells in the fish's epidermis.The larvae attach with equal readiness to skin from the upper and lower surfaces of S. solea. Thus the preponderance of young parasites on the upper surfaces of soles is due not to a preference for the upper skin but to the fact that the lower skin is in contact with the substratum and cannot be reached by the larvae.These results led to speculations on the way in which host specificity evolved in the Monogenea.I am indebted to Mr J. E. Green of the Plymouth Laboratory for setting up a tank containing infected soles and for maintaining the tank and feeding the fishes for many months.I am also grateful to the Directors and Staff of the Plymouth Laboratory and the Fisheries Laboratory, Lowestoft, for hospitality and assistance. I am particularly grateful to Mr J. Riley of the Lowestoft Laboratory for providing various flatfishes.

V. On the structure, physiology, and development of Antedon ( Comatula , Lamk.) rosaceus

1876 ◽  
Vol 24 (164-170) ◽  
pp. 211-231 ◽  
Keyword(s):  
Deep Sea ◽  
Royal Society ◽  
Free Swimming ◽  
Spare Time ◽  
Type Form ◽  
History Of ◽  
The Subject ◽  
Swimming Larva ◽  
Free Swimming Larva

When, in 1865,1 communicated to the Royal Society the First Part of Monograph on the Anatomy, Physiology, and Development (excluding he earliest stages previously described by Prof. Wyville Thomson) of animal which might be regarded—except in certain comparatively unimportant particulars—as a type-form of the whole Crinoidal series, I had nearly concluded my investigation of the subject of it, that I fully ontemplated the presentation of the Second and concluding part in the course of a year (Jr two. Uncertain health, however, interfered with its ompletion in the first instance; and my spare time has since then been;o far taken up by the various inquiries that have arisen out of the Deep-Sea researches which I prosecuted in the vacations of 1868 and three following years, that I have found myself quite unable to resume the tudy of Antedon . Thus it comes to pass that, though I have now had me for a period of ten years the results of my previous labours, as presented in several hundred preparations, with a series of most admirable Ira wings executed by Messrs. George West and A. Hollick, illustrating almost every point of primary importance not only in its structure, but also in the history of its development from nearly the earliest Pentacrinoid stage, all this material has remained unpublished; for I have felt that the completion of my Monograph in a manner worthy of its subject required that certain obscurities should be dissipated and certain gaps filled up; and it now, also, becomes desirable that the Histology of this type should be more fully elucidated by the aid of modern appliances, and that the earliest phases of its Development should be thoroughly reinvestigated. I especially desire to ascertain whether the free-swimming larva (or pseudembryo) has a Gastrcea stage, and to follow out the derivation of the gastric and perivisceral cavities of the Pentacrinoid, and of its original tentacular system, from the structures of the pseudembryo—points on which Prof. Wyville Thomson’s Memoir, admirable as it is, does not enlighten us. This stage of the history has been subsequently studied by a most able observer, Herr Metschnikoff; and the conclusions he has arrived at in regard to the origin of the tentacular system I find to be essentially accordant with those which I had drawn from my own researches on a later stage.

VIII.—Structure and Biology of the Larva and Spat ofVenerupis pullastra(Montagu)

1952 ◽  
Vol 62 (1) ◽  
pp. 255-297 ◽  
Author(s):  
D. B. Quayle
Keyword(s):  
Vertical Distribution ◽  
High Mortality ◽  
Functional Significance ◽  
Marine Invertebrates ◽  
Point Of View ◽  
Seasonal Abundance ◽  
Free Swimming ◽  
Possible Cause ◽  
Swimming Larva ◽  
Free Swimming Larva

Synopsis:This is a study of the structure and biology of the lamellibranchVenerupis pullastra(Montagu) from the early larva to the spat stage. The larva is identified, and the functional significance of the changes that occur during metamorphosis from the larva to the spat is considered. Organ development in the spat up to a length of one millimetre is described. The free swimming larva is studied from the point of view of seasonal abundance, length of pelagic period, vertical distribution and diurnal migration. Spatfalls both on artificial and natural bottom are studied, and the results indicate a possible cause for the high mortality in the early stages of marine invertebrates with this type of reproduction.

Calcium accumulation and secretion in the serpulid polychaete Spirorbis spirorbis L. at settlement

1975 ◽  
Vol 55 (4) ◽  
pp. 911-923 ◽  
Author(s):  
J. A. Nott ◽  
K. R. Parkes
Keyword(s):  
Sea Water ◽  
The Body ◽  
Posterior Half ◽  
Free Swimming ◽  
Calcium Accumulation ◽  
Material Forming ◽  
Suitable Substratum ◽  
Swimming Larva ◽  
Free Swimming Larva

When the free-swimming larva of the polychaete tubeworm Spirorbis spirorbis settles permanently on a suitable substratum, it forms a thin, mucous, anchoring tube, which covers only the posterior half of the body. Within 3 h the worm has built a comparatively thick, calcareous tube onto the anterior end of the initial, mucous tube, which later becomes a compressed and folded remnant (Nott, 1973). The volume of calcareous material forming the tube cannot be stored within the body of the larva before settlement and must, therefore, be taken up rapidly from sea water or ingested material.

scholarly journals An organismal perspective on C. intestinalis development, origins and diversification

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Matthew J Kourakis ◽  
William C Smith
Keyword(s):  
Life History ◽  
Cell Division ◽  
Model Organism ◽  
Tree Of Life ◽  
Laboratory Model ◽  
Free Swimming ◽  
Adult Form ◽  
Sea Squirt ◽  
Swimming Larva ◽  
Free Swimming Larva

The ascidian Ciona intestinalis, commonly known as a ‘sea squirt’, has become an important model for embryological studies, offering a simple blueprint for chordate development. As a model organism, it offers the following: a small, compact genome; a free swimming larva with only about 2600 cells; and an embryogenesis that unfolds according to a predictable program of cell division. Moreover, recent phylogenies reveal that C. intestinalis occupies a privileged branch in the tree of life: it is our nearest invertebrate relative. Here, we provide an organismal perspective of C. intestinalis, highlighting aspects of its life history and habitat—from its brief journey as a larva to its radical metamorphosis into adult form—and relate these features to its utility as a laboratory model.

scholarly journals Ultrastructural observations on the oncomiracidium epidermis and adult tegument of Discocotyle sagittata, a monogenean gill parasite of salmonids

2021 ◽  
Vol 120 (3) ◽  
pp. 899-910
Author(s):  
Mohamed Mohamed El-Naggar ◽  
Richard C Tinsley ◽  
Jo Cable
Keyword(s):  
Surface Layer ◽  
Cell Layer ◽  
Ciliated Cell ◽  
The Body ◽  
Life Stages ◽  
Sensory Receptors ◽  
Ciliated Cells ◽  
Membrane Turnover ◽  
Free Swimming ◽  
Gill Parasite

AbstractDuring their different life stages, parasites undergo remarkable morphological, physiological, and behavioral “metamorphoses” to meet the needs of their changing habitats. This is even true for ectoparasites, such as the monogeneans, which typically have a free-swimming larval stage (oncomiracidium) that seeks out and attaches to the external surfaces of fish where they mature. Before any obvious changes occur, there are ultrastructural differences in the oncomiracidium’s outer surface that prepare it for a parasitic existence. The present findings suggest a distinct variation in timing of the switch from oncomiracidia epidermis to the syncytial structure of the adult tegument and so, to date, there are three such categories within the Monogenea: (1) Nuclei of both ciliated cells and interciliary cytoplasm are shed from the surface layer and the epidermis becomes a syncytial layer during the later stages of embryogenesis; (2) nuclei of both ciliated cells and interciliary syncytium remain distinct and the switch occurs later after the oncomiracidia hatch (as in the present study); and (3) the nuclei remain distinct in the ciliated epidermis but those of the interciliary epidermis are lost during embryonic development. Here we describe how the epidermis of the oncomiracidium of Discocotyle sagittata is differentiated into two regions, a ciliated cell layer and an interciliary, syncytial cytoplasm, both of which are nucleated. The interciliary syncytium extends in-between and underneath the ciliated cells and sometimes covers part of their apical surfaces, possibly the start of their shedding process. The presence of membranous whorls and pyknotic nuclei over the surface are indicative of membrane turnover suggesting that the switch in epidermis morphology is already initiated at this stage. The body tegument and associated putative sensory receptors of subadult and adult D. sagittata are similar to those in other monogeneans.

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