Calcareous Plates Research Articles

Further observations on the genusPappomonasManton et Oates with special reference toP. virgulosasp. nov. from West Greenland

Electron microscopy of dried preparations of Arctic nanoplankton has permitted a second species of the recently erected genus Pappomonas Manton et Oates to be described and named. P. virgulosa sp. nov. is characterised by coccolith appendages composed of a central shaft ending in a cluster of four finger-like rods. There are also calcified plates of characteristic construction, without appendages. Detailed observations on the coccoliths, especially on the shapes and arrangement of component calcite crystallites and the presence of unmineralised components, have permitted further comparisons to be made with equivalent structures in Papposphaera lepida Tangen, recently investigated in the southern hemisphere, as well as with Pappomonas flabellifera Manton et Oates. As a working hypothesis, an interpretation of coccolith morphology in all three taxa has been formulated in terms of known structural components of uncalcified scales in Chrysochromulina spp. The need for fuller information on certain details, no...

An ultrastructural study of the mantle of the barnacle, Elminius modestus Darwin in relation to shell formation

The fine structure of the mantle and shell of the barnacle, Elminius modestus Darwin has been examined by electron microscopy. The epithelial cells along the outer face of the mantle differ in size, shape, and organelle complexity according to the different components of the shell they secrete. The shell consists of a non-calcareous basis and calcareous mural and opercular plates which are connected by a flexible opercular hinge. Both the basis and opercular hinge are composed of two main units: an outer cuticulin layer and a lamellate component of well ordered arched fibrils. During the deposition of the latter structures morphological changes in the cells occur which may be correlated with the moulting cycle. Preliminary results show that the calcareous plates are covered by an outer epicuticle, which is bordered by a cuticulin layer; the inner calcareous component, consists of an orderly arrangement of organic matrix envelopes within which crystals may be initiated. The cells lining the inner surface of the mantle are uniform in appearance with a thin cuticle at their free surface which lines the body cavity. The latter structure of the cuticle and manner of its deposition are similar to those of the basis and opercular hinge. Separating the outer and inner mantle epithelial cells is connective tissue which comprises several differing cell types. The possibilities are discussed of the rôle these cells may play in shell deposition. The modes by which underlying cells secrete the different shell components and the cuticle lining the inner face of the mantle, are also discussed.

An electron-microscope investigation into the cuticle and associated tissues of the operculum of some marine serpulids

The fine structure of the opercula of Spirobis borealis Daudin and S. pusilloides Bush, and the primary and secondary operculum of S. granulatus (L) have been examined by electron microscopy. In different regions, the epithelium of the operculum exhibits variations in thickness and fine structure which correspond to transitions from peduncular to opercular wall to opercular plate epithelia. Externally, the peduncle and walls of the operculum are covered by a cuticle which is composed of several layers of fibrils/fibres embedded in an amorphous matrix. It is regularly traversed by microvilli from underlying cells. At the operculum rim, the cuticle changes so that its appearance is thick and solid. It continues across the roof of the operculum as a thin layer overlying a calcareous plate. The secondary operculum of S. granulatus differs from those of the other species in that an internal calcareous plate and solid cuticle line the roof of the operculum. It differs further in possessing an opercular pore. The possibilities are discussed of the cuticle fibrils/fibres of the peduncle and the opercular wall being collagenous in nature, and later being transformed to a solid tanned structure overlying a calcareous plate. The modes of secretion of the cuticle and calcareous plate by underlying cells are also discussed.

Some new data on skin-digestion and absorption in urchins and sea stars (Asterias and Henricia)

An adult Psammechinus miliaris, and another specimen 8 mm in diameter were both fed “apically” by deposition of a protein-powder extracted from a heavily 14C-tagged urchin. The organs of the former were counted and the latter was totally sectioned and autoradiographed. The gut was more labelled than expected after an “apical” meal. This could be explained by a pumping of some nutritive powder into the gut, the bright marking of the superficial tissues being obviously due to direct uptake. The localized proteolysis produced by a podial disc of P. miliaris on a black gelatin-film may be due to the secretion of special cell-masses just underlying the calcareous plates of the disc. Extracts from mucus, small spines and dorsal podia from the anterior furrow of Echinocardium cordatum produce a conspicuous digestion of Remazol-brilliant blue hidepowder in vitro. Several in vivo tests with artificial substrates suggest the existence of a trypsin-like enzyme and not chymiotrypsin in the mucus. Fresh frozen sections in podia of Asterias rubens treated with A.S. naphthol-propionate showed that special cells, scattered in the connective tissue, gave a dark-red stain. Strains of red granules issued by them found their way to the surface of the disc between the columnar epithelial cells. These chimiotrypsin-positive cells and their products seem identical to those seen by Chaet and Philpot (1964) in A. forbesi. These authors did not suspect their digestive function. The nutrition of Henricia sanguinolenta through the body wall was tested either with radioactive diatoms or 14C-labelled amino acids in sea water selectively offered to one or two arms. Both countings and autoradiographs demonstrated the importance of skin-digestion and absorption, especially in the ambulacra. The absorbed nutrients reach the muscle layer, not only the epiderm as mentioned in Ferguson's (1967) esperiments.

The cuticle of the Aplacophora and its evolutionary significance in the Mollusca

The cuticle of Proneomenia consists of a mucoid matrix containing calcareous spicules and is secreted by the mantle epithelium at the base of the ventral (pedal) groove and over the general body surface. Histochemical examination shows the matrix to be composed of a glycoprotein complex with high acid mucopolysaccharide and low protein contents in which tanning plays little part in stabilization.The cuticle of the Aplacophora is tentatively equated with an early mucoid stage in the evolution of the molluscan shell and it is suggested that secretion of additional protein, followed by hardening by quinone‐tanning, are necessary further stages before a calcified shell evolves. The aplacophoran cuticle is compared with that of Acanthochitona (Polyplacophora) and, although they are similar in many respects, the latter has in addition a discrete inner cuticular layer whichmay act as a semi‐conducting membrane in the deposition of the calcareous plates. The spicules are similar in both groups, each being secreted within a thin cup‐like membrane which exhibits somewhat similar properties to the inner cuticle.

The organic constitution of several benthonic invertebrates from McMurdo sound, Antarctica

1. 1. The total nitrogen, protein, carbohydrate and lipid levels of 7 benthonic Antarctic marine invertebrate species were studied at different seasons and from different localities for comparison with studies on similar temperature invertebrates. 2. 2. The protein level of most of the species studied is close to 50 per cent of the dry weight of the tissue. The most unusual observation was the high level of protein in the asteroid Perknaster fuscus antarcticus body wall, which is rather devoid of the usually abundant calcareous plates and is made up largely of connective tissue. The carbohydrate levels of the various Antarctic invertebrates studied compare favorably with the carbohydrate levels of comparable temperature marine forms. 3. 3. Only the isopod Glyptonotus antarcticus showed a high tissue lipid level, like other Antarctic crustaceans previously studied. The other Antarctic invertebrates had moderate or low lipid levels in their tissues, except in special cases such as the high levels in the ovaries of Perknaster.

Effect of Carbonic Anhydrase Inhibitors on Shell Development and Growth of Balanus improvisus Darwin

CARBONIC CARBONIC anhydrase, associated with respiration in some invertebrate and vertebrate animals, has been found in the shell-forming tissues of many mollusks (Freeman and Wilbur, 1948). More recently (Wilbur and Jodrey, 1955) it has been demonstrated that the enzyme is directly associated with shell deposition and that inhibition of carbonic anhydrase reduces the rate of calcium carbonate deposition both in whole oysters and in mantle-shell preparations. The calcareous shell plates of the acorn barnacles are similar to mollusk shells, in that much of the crystalline material deposited in the organic matrix is calcium carbonate. The enzyme systems associated with shell development and growth in barnacles are not known, and, although carbonic anhydrase has been reported from a wide variety of invertebrates (Brinkman, 1933, Ferguson, Lewis, and Smith, 1937), acorn barnacles have not been among the animals included in the studies. Darwin (1854) postulated that the calcareous plates of the Balanidae are formed by the apposition of the mantle against the older portions of the shell, but few additional studies have been made on shell development. The present study has had two major objectives: (1) to determine whether or not carbonic anhydrase is present in the shell-forming mantle and internal body tissues of Balanus improvisus Darwin and (2) to study the effects of carbonic anhydrase inhibitors on shell development, shell growth, and molting.

Frizzellus Irregularis, a New Holothurian Sclerite from the Upper Bathonian of the Dorset Coast, England

Calcareous plates from the upper Bathonian (middle Jurassic) of the Dorset coast, England, doubtfully placed in the Holothuroidea and previously referred to Etheridgella sp., are redescribed as Frizzellus irregularis, n.gen., n.sp. A statistical study of Frizzellus n.gen. (qua 9parataxon9) shows it to be a normally distributed coherent unit of a zoological genus within the sections and localities studied.

MOULTING AND GROWTH IN BALANUS IMPROVISUS

The Cirripedia differ from other arthropods in that the body is enclosed by calcareous plates which are not shed with the chitinous layers of the animal body and the inner lining of the mantle. As early as 1854 Darwin reported that members of the families Balanidae and Chthamalidae underwent periods of exuviation. He reports that Mr. W. Thompson of Belfast kept twenty specimens of Balanus balanoides alive, presumabLy in the laboratory, and on the twelfth day all had moulted once and one individual twice. The frequency of moulting over an extended period of time has not been determined accurately for any sessile barnacle, presumably because of the difficulties involved in maintaining them in the laboratory. Thomas (1944) reports that moults of a selected group of Balanus perforatus of uniform size but unknown age occurred about every fifth day but makes no reference to the period over which these observations were made. Other than these observations there has been no statement, to our knowledge, concerning the relationship between growth of shell plates and ecdyses nor is the frequency of moulting and the intermoult period, from the time of settling, known for any length of time in any barnacle. The purpose of this investigation was to determine, therefore, a medium which would support growth of barnacles in the laboratory, to ascertain the time of moulting, period of intermoult, and the relationship of shell growth to the moulting cycle. Balanus improvisus Darwin, a barnacle which settles at Beaufort, N. C. during the winter and spring months, was selected for this study.

Rôle des flagellés calcaires dans la fertilité et la sédimentation en mer profonde

Some quantitative data are given here on calcareous flagellates, showing their importance in deep seas, as shown by recent work in the Atlantic Ocean and in the Western Mediterranean. 1.1. The systematic are as yet very provisional. One may distinguish, however, five “species” common to depths below 1,000 metres. Cocolithus fragilis Lohm., is prevalent in warm and temperate seas, between depths of 0 to 3,000 metres. C. wallichii Lohm., Corisphaera fagei Bernard and Syracosphaera profunda Bernard are abundant in warm seas, chiefly below 200 metres. The aberrant Thoracosphaera heimi (Lohm.) is oceanic and inhabits colder layers (< + 3°C, the first three forms < +8°C).2.2. The number of cells per litre is estimated by means of a reversed microscope, after sedimentation of stained water in small glasses. Between the depths of 1,000 and 3,000 m, Coccolithus fragilis generally has 7,000 to 240,000 cells, the other species giving counts of only 4,000 to 100,000 cells. The isolated spores of C. fragilis are even more common, which explains the great resistance of these flagellates to unfavourable waters.3.3. The rate of cell-division seems to be rather low. The number of Coccolithus near the surface grows at the rate of about 1/6 per day, and, after 8 days of such multiplication, a rest is almost always observed in the Mediterranean. In the coastal waters of Algeria, the annual production of C. fragilis per cubic metre is calculated at 36 g. containing about 9 g of calcareous material.4.4. Since the coccoliths are very thin, at most 5 per cent by weight survive to be deposited in deep-sea muds. However, the calcareous plates, more or less dissociated in granules, make up from 15 to 30 per cent of the dry weight of sediments, at 2,000 m depth off Algiers. The same deposits are rich in thick plates of extinct coccolithophorids, derived from Tertiary rocks of the African coast.5.5. The total volume of calcareous flagellates per litre generally amounts to more than 50 per cent, and often 95 per cent, of the phytoplancton in the bathypelagic zone, other algae present being chiefly Myxophyceae (Nostoc, Microcystis, etc....). Thus, the coccolithophorids are the chief subscriber to deep-sea fertility and sedimentation, down to a depth of 4,000 m and probably even deeper.

EXTENSIVE CALCIFICATION OF THE LUNGS AS A DISTINCT DISEASE

Calcareous deposits, especially local, are of frequent occurrence in degenerated and necrotic tissue, old inflammatory exudates, and other dead material such as thrombi. Calcification in the media and intima of the arteries in old persons, in pleural and pericardial exudates where large calcareous plates may form, the concretions in the apices of the lungs and in the bronchial lymph nodes as the result of tuberculosis, are all familiar examples. Wherever tissue degenerates, deposits of calcium salts may take place, usually in the stroma, but also, although rarely, in the cells themselves, as, for instance, in the renal epithelium in toxic necrosis, in ganglion cells, in muscle fibers. Deposition of calcium salts also occurs on a larger scale, when it may give rise to peculiar conditions and even distinct diseases. The cause of such deposits is in general assumed to be a supersaturation, so to speak, of the blood and tissue

Notes on Echinoderm Morphology, No. XI. On the Development of the Apical Plates in Amphiura squamata

ABSTRACT Some very important observations “On the Development of the Calcareous Plates of Amphiura” have been recently published by Dr. J. W. Fewkes,1 who has also entered into a discussion respecting the morphological relations of these plates. Amphiura squamata is viviparous, and the young undergo a direct or abbreviated development without passing through a definite Pluteus form, so that it is easy to follow the various larval stages and to study the mode of appearance of the skeletal plates.

On the Pharynx of an Unknown Holothurian of the Family Dendrochirotae, in which the Calcareous Skeleton is remarkably developed

ABSTRACT The specimen of which an account is here given was found amongst a quantity of other material dredged in the Sulu Sea, in from ten to twenty fathoms, by Captain W. Chimmo, R.N., of H.M.S. “Nassau,’ 1871, and presented by him to the Anatomical Department of the Oxford Museum. The specimen is unfortunately isolated, and no traces can be found of the body of the Holothurian to which it belonged. Its actual length is about th inches, and because of its large size and the regularity of the arrangement of the calcareous plates with which it is protected, it forms a striking object, which attracts the eye of a naturalist at once. The anterior part of the pharynx itself is complete, with its contained tentacles and calcareous ring, but the retractor muscles are completely torn away, and posteriorly no trace remains of the water vascular ring or its appendages. The membrane which closed the intervals between the rows of radial pharyngealia has also disappeared. The calcareous plates composing the actual ring (annulus) around the anterior region of the pharynx will here be termed annularia; those disposed in rows posteriorly the pharyngealia.

On the Oral and Apical Systems of the Echinoderms

ABSTRACT The following essay is an attempt to compare and criticise the various views that have been put forward from time to time, respecting the homologies among the different Echinoderms of the two groups of calcareous plates, which appear at a very early period around the two peritoneal diverticula of the primitive digestive sac of the larva.

On the Occurrence of the Genus Astrocrinites (Austin) in the Scotch Carboniferous Limestone Series; with the Description of a new Species ( A. Benniei ), and Remarks on the Genus

I ntroduction .–In a paper entitled “Proposed Arrangement of the Echinodermata” &amp;c., Messrs. Austin referred to a genus which they proposed to establish under the name of Astracrinites , in the following words:—“Another genus ( Astracrinites of our MS.) offers so many affinities to the recent and fossil Echinodermata, that we consider it the most remarkable of all the known genera. By its being lobed it approaches to the Lobistella ; its ambulacra, spines, and arms mark it as allied to the Echinites , while the arrangement of its calcareous plates connects it with the Lilies of the ocean. In short, it possesses the lobes of a Starfish, the ambulacra and spines of a Sea-urchin, and the plates of a Crinoid. It is further remarkable by deviating from the quinary type so prevalent in the Echinodermata: the lobes and ambulacra of this new genus are each four in number.” In the following year Messrs. Austin described this curious and aberrant form under the name of Astracrinites tetragonus. Their description is as follows :” “Family Astracrinidæ, “Consisting of the genera Astracrinites and Aporocrinites ; “Genus Astrocrinites, Austin. “Def.—Dorso-central plate quadrangular, to which four pairs of elongated plates are attached, imparting a lobed shape to the fossil. In the retiring angles at the base of the four lobes are a like number of ambulacra. Mouth central. Anus lateral. “A. tetragonus, Austin. “Def.—The plates of this species agree with the generic definition. Each of the elongated plates has two or three rows of minute tubercles around its outer margin

On the Discovery of the Scales of Pteraspis , with some Remarks on the Cephalic Shield of that Fish

Prof. Agassiz was the first to described certain remains found in the Cornstones of Herefordshire, associated with the well-known Cephalaspis Lyellii . He considered these remains as portions of the cephalic shield of three distinct species of Cephalaspis , which he named C. rostratus, C. Lewisii , and C. Lloydii , respectively. At the same time he expressed his doubts as to whether, on account of the peculiar structure of the test, it might not be advisable to place these three Fish in a distinct genus. In 1847, Dr. R. Kner, writing in Haidinger's ‘Abhandlungen,’ considered the fossils in question as the remains of Cephalopoda, and he proposed, therefore, to place them in a new genus, Pteraspis , remarking that the structure of the test preserved in these fossils corresponded closely with that of the calcareous plate or “cuttle-bone” of Sepia , Prof. Huxley has since investigated the structure of both Cephalaspis and Pteraspis , and published his results in this Journal. It will therefore only be necessary to remark that he came to the conclusion that Pteraspis Lewisii, P. Lloydii , and P. rostratus were the remains of Fish, and presented no real analogy to Sepia in the microscopic structure of the test. This, he showed, was similar to that of Cephalaspis , but differed in the absence of bone-cells or lacunæ; and he adopted Kner's name of Pteraspis for these Fish, considering that the differences in form and structure between the two groups warranted a generic separation.

On Trematis, a new genus belonging to the family of Brachiopodous Mollusca

In looking over the valuable collection of Palaeozoic fossils brought from the United States by Mr. Lyell, I was struck by a small Brachiopod possessing a combination of structure hitherto unobserved, which entitles it to be placed in a separate genus. The general appearance of the shell is similar to Orbicula , in which genus it has hitherto been placed. It is nearly circular, but slightly broader than long and with an irregular outline. The shell is attached by a ligament which passes through an oblong slit in the lower valve, as in the Orbiculae; this slit reaches from about the centre of the shell to near the posterior margin. Both the valves are slightly and irregularly convex, giving a depressed form to the shell. The valves are united by a hinge, of which the details cannot be seen in the specimens; but it is probably formed of two diverging lamellar processes in the dorsal valve, for where the shell of that valve has been worn away, we can trace three calcareous plates diverging from the hinge of the dorsal valve, as in the Leptaenoid species of Orthis this and in many of the Spirifers. Wherever these plates are found in ,the Brachiopoda, the outer pair appear to be continuations of the teeth or lamellar processes of the hinge; so that the presence of such plates is sufficient to show that the valves played upon a hinge.

XXX. Some observations on the economy of molluscous animals, and the structure of their shells

The shells of Mollusca appear to be coeval with the first formation of the animal: they may be observed covering the embryo on its first development in the egg, even before it has acquired its proper shape or any of its internal organs. The accurate Swammerdam observed them in the eggs of several of the garden and pond snails. His observations have been recently verified and extended by Pfeiffer, on many species of land and fresh-water Mollusca; and I have myself observed the same fact in the eggs of several animals belonging to the different orders of marine shells: there is reason, therefore, to believe that this circumstance is general throughout the class. These observations are most easily made on the embryo of the fresh-water shells, such as the Lymnœœ, Physœ, Ancyli , and Bithyniœ, the eggs of these animals being covered with a transparent coat; while the viviparous Mollusca, and especially the Littorinœ, Paludinœ , and Cyclades , offer the additional advantage of exhibiting the embryos of their animals in all the different states of development at the same time. The cephalopodous Mollusca form no exception; their bone, composed of two or three calcareous plates, being found fully developed in the egg of the Cuttle-fish some time before the young animal is hatched.