Developmental regulation and morphological saltation in the heteromorph ammonite Nipponites

Paleobiology ◽  
1988 ◽  
Vol 14 (3) ◽  
pp. 272-286 ◽  
Author(s):  
Takashi Okamoto
Keyword(s):  
Developmental Regulation ◽  
Shell Growth ◽  
Growth Direction ◽  
Intermediate Form ◽  
Free Living ◽  
Neutral Buoyancy ◽  
Life Orientation ◽  
Sea Bottom ◽  
Mode Of Life ◽  
Lower Limits

Nipponites, a Late Cretaceous nostoceratid ammonite, shows a peculiar meandering shell growth in the middle-late stage. Assuming neutral buoyancy, and a constant aperture angle relative to the sea bottom, meandering growth of this ammonite was modeled by computer simulation. In this model, the meandering shell growth is controlled by regulation of life orientation. The remarkable similarity in the coiling modes and rib obliquity patterns between the computer-simulated and actual specimens strongly suggests a free living mode of life in Nipponites with an approximately neutral buoyancy. The simulation also suggests that morphological saltation from a simple helicoid form like Eubostrychoceras japonicum to a meandering shell form like Nipponites occurred abruptly without any intermediate form by minor change of the upper and lower limits of growth direction.

Ecophenotypic plasticity in shell growth direction of asari clam Ruditapes philippinarum

2021 ◽  
pp. 1-6
Author(s):  
Takeshi Tomiyama
Keyword(s):  
Growth Rate ◽  
Shell Growth ◽  
Shell Height ◽  
Growth Direction ◽  
Ruditapes Philippinarum ◽  
Shell Morphology ◽  
Individual Growth ◽  
Shell Size ◽  
Internal Factors ◽  
Suitable Habitats

Abstract Asari clam (or Manila clam) Ruditapes philippinarum is an important bivalve for local fisheries. This species exhibits a large variation in shell morphology, and the shell roundness tends to be greater in more unsuitable habitats. To test whether the increments in shell size parameters (length, height and width) were affected solely by environmental conditions or by internal factors such as initial shell shapes or growth rate, a field caging experiment was conducted at two different sites of unsuitable and suitable habitats in Matsukawaura Lagoon, Japan, where shell shapes of wild clams were significantly different between the habitats. In the experiment, clams were released from the two sites to the same site or to the other site and were re-collected after 3, 6 and 12 months of caging. Caged clams originating from unsuitable habitats and released to suitable habitats showed a reduction in shell height relative to shell length, while clams from suitable habitats introduced to unsuitable habitats showed marked increases in both shell height and width. Generalized linear mixed models suggested that the increase in shell height was affected largely by the release habitat (environment) whereas the increase in shell width was affected largely by the individual growth rate. These results suggest that marginal growths in shell height and width respond differently to external and internal factors of clams, resulting in plasticity in their shell shapes according to the environments to which they are translocated.

scholarly journals The life histories and population dynamics of monogenean gill parasites of Trachurus trachurus (L.)

1962 ◽  
Vol 42 (3) ◽  
pp. 587-600 ◽  
Author(s):  
J. Llewellyn
Keyword(s):  
Coastal Waters ◽  
Life Histories ◽  
Feeding Habits ◽  
Limiting Factor ◽  
Trachurus Trachurus ◽  
Free Living ◽  
Sea Bottom ◽  
Second Year ◽  
Post Spawning ◽  
Gill Parasites

Gastrocotyle trachuri and Pseudaxine trachuri infect young Trachurus trachurus at Plymouth as soon as the 3- or 4-month-old adolescent fishes descend to the sea bottom in October. The parasites normally mature in 3 or 4 months, but, exceptionally, in about 1 month, and the life-span is normally no longer than 1 year. Trachurus specimens at the beginning of their second year pick up a largely new infection of parasites.G. trachuri and P. trachuri are much less frequent on 2- and 3-year-old specimens of Trachurus and probably occur only very rarely on still older fishes, the limiting factor being not an age-immunity but a post-spawning migration of the host from the concentration of free-living infective stages of the parasites in coastal waters.The parasites have adapted themselves to a seasonal change in the feeding habits of Trachurus by ceasing to produce larvae in anticipation of the summer disappearance of scad from the sea bottom in pursuit of pelagic food-organisms.

scholarly journals Evolution of parasitism along convergent lines: from ecology to genomics

Parasitology ◽  
2013 ◽  
Vol 142 (S1) ◽  
pp. S6-S15 ◽  
Author(s):  
ROBERT POULIN ◽  
HASEEB S. RANDHAWA
Keyword(s):  
Parallel Evolution ◽  
Genome Reduction ◽  
Phenotypic Traits ◽  
Parasitic Mode ◽  
Evolutionary Time ◽  
Free Living ◽  
Mode Of Life ◽  
Parasitic Castrator ◽  
Host Exploitation

SUMMARYFrom hundreds of independent transitions from a free-living existence to a parasitic mode of life, separate parasite lineages have converged over evolutionary time to share traits and exploit their hosts in similar ways. Here, we first summarize the evidence that, at a phenotypic level, eukaryotic parasite lineages have all converged toward only six general parasitic strategies: parasitoid, parasitic castrator, directly transmitted parasite, trophically transmitted parasite, vector-transmitted parasite or micropredator. We argue that these strategies represent adaptive peaks, with the similarities among unrelated taxa within any strategy extending to all basic aspects of host exploitation and transmission among hosts and transcending phylogenetic boundaries. Then, we extend our examination of convergent patterns by looking at the evolution of parasite genomes. Despite the limited taxonomic coverage of sequenced parasite genomes currently available, we find some evidence of parallel evolution among unrelated parasite taxa with respect to genome reduction or compaction, and gene losses or gains. Matching such changes in parasite genomes with the broad phenotypic traits that define the convergence of parasites toward only six strategies of host exploitation is not possible at present. Nevertheless, as more parasite genomes become available, we may be able to detect clear trends in the evolution of parasitic genome architectures representing true convergent adaptive peaks, the genomic equivalents of the phenotypic strategies used by all parasites.

Geometric shell growth and mode of life of a Devonian chonetoidean brachiopod

Lethaia ◽  
2007 ◽  
Vol 31 (2) ◽  
pp. 125-135 ◽  
Author(s):  
PATRICK R. RACHEBOEUF ◽  
ZARELA A. HERRERA
Keyword(s):  
Shell Growth ◽  
Mode Of Life

scholarly journals Texture of the Freshwater Shells from the Unionidae Family Collected in the Czech Republic Investigated by X-ray and Neutron Diffraction

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1483
Author(s):  
Monika Kučeráková ◽  
Jan Rohlíček ◽  
Stanislav Vratislav ◽  
Markéta Jarošová ◽  
Ladislav Kalvoda ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Shell Growth ◽  
Growth Direction ◽  
Mechanical Resistance ◽  
Minimal Amount ◽  
The Czech Republic ◽  
Crystallographic Preferred Orientation ◽  
X Ray ◽  
Engineering Sciences ◽  
Source Of Information

Bivalve shells exhibit extreme mechanical resistance despite using a minimal amount of material. The shells thus represent an inspiration and a source of information for environmental, geological, and engineering sciences. In this study, two species of freshwater shells from the Unionidae family, collected in the Czech Luznice River, were investigated with respect to their crystallographic preferred orientation by means of X-ray and neutron diffraction. The observed texture was found to be of a strongly uniaxial type, with the strength increasing along the shell growth direction. The c-axis of aragonite does not change during growth and its alignment remains perpendicular to the outer surface of the shell

The chamber formation cycle in Nautilus macromphalus

Paleobiology ◽  
1981 ◽  
Vol 7 (4) ◽  
pp. 481-493 ◽  
Author(s):  
Peter Ward ◽  
Lewis Greenwald ◽  
Yves Magnier
Keyword(s):  
Direct Contact ◽  
Prime Factor ◽  
Shell Growth ◽  
The Body ◽  
Liquid Volume ◽  
Final Thickness ◽  
Neutral Buoyancy ◽  
The Face ◽  
Liquid Removal ◽  
Direct Measures

The chamber formation cycle in externally shelled, chambered cephalopods consists of mural ridge formation, secretion of the siphuncular connecting ring, septal calcification, and cameral liquid removal. Radiographic observation of the chamber formation cycle in specimens of Nautilus macromphalus allows direct observation of the various processes of the chamber formation cycle in a chambered cephalopod, and gives direct measures of rates. New chamber formation in N. macromphalus initiates when slightly more than half of the cameral liquid has been removed from the last formed chamber. At this volume, the liquid within the chamber drops from direct contact with the permeable connecting ring to a level where it is no longer in direct contact and must move onto the connecting ring due to wettable properties of the septal face and septal neck. This change from “coupled” to “decoupled” emptying coincides with the formation of a mural ridge at the rear of the body chamber, in front of the last formed septum. With completion of the mural ridge, the septal mantle moves forward from its position against the face of the last formed septum and attaches to the new mural ridge, where it begins calcifying a new septum in front of the newly created, liquid-filled space. Emptying of the new cameral liquid from this space commences when the calcifying septum has reached from one-third to two-thirds of its final thickness. The cessation of calcification of the septum coincides with a liquid volume in the new chamber of approximately 50%, at which point the cycle begins anew. During the chamber formation cycle apertural shell growth appears to be continuous. Since apertural shell growth is the prime factor leading to increased density in seawater, and hence decreased buoyancy, the period in the chamber formation cycle between the onset of septal calcification and the onset of emptying would be a time of greatly decreasing buoyancy. This is avoided by the removal of decoupled liquid from previously produced chambers. In this way constant neutral buoyancy is maintained. The time between chamber formation events in aquarium maintained N. macromphalus appears to be between 70 and 120 d.

Form and function in Thylacocephala, Conchyliocarida and Concavicarida (?Crustacea): a problem of interpretation

1985 ◽  
Vol 76 (2-3) ◽  
pp. 391-399 ◽  
Author(s):  
W. D. Ian Rolfe
Keyword(s):  
Compound Eye ◽  
Neutral Buoyancy ◽  
Low Contrast ◽  
Linear Pattern ◽  
Form And Function ◽  
Mode Of Life ◽  
And Function ◽  
Food Substrate

ABSTRACTDifferences in the preservation of Jurassic thylacocephalans and conchyliocarids have given rise to different interpretations of the form of these fossils, and thus their mode of life. When evidence from these two groups is combined with that derived from Palaeozoic concavicarids, it becomes possible to unify the several interpretations of this one group of organisms, the Thylacocephala. The group ranges from at least the Silurian to the Cretaceous.A review is given of how these differences of interpretation have arisen, and some resolution is attempted. If the thylacocephalan “anterior structure” is reinterpreted by analogy with hyperiid amphipods as a paired compound eye occupying most of the surface of the head, it explains its bilobed nature and the position of the stomach within the structure, but it raises the difficulty of a post-cephalic origin for the carapace. The simpler solution is preferred of regarding this structure as discrete paired eyes with a smooth cornea and subjacent crystal cones.The raptorial appendages are post-oral and post-adductor in insertion. They are therefore tentatively identified as the maxillae and maxilliped, but verification of the mandible's position is needed to test this. The postero-ventral battery of “body somites” is reinterpreted as paired protopods of abdominal limbs. A respiratory current is deduced to have entered a branchiostegal chamber ventrally, and left it posterodorsally. It is speculated that the looped linear pattern of intra-cuticular spheres in Paraostenia are photophores. The large eyes with small interommatidial angles were probably used to discern low contrast prey or carrion against a dim background. By analogy with hyperiid amphipods, it is suggested that at least some thylacocephalans were mesopelagic predators. They may have attained neutral buoyancy from their food substrate of shark and coleoids.

scholarly journals Determination of the shell growth direction during the formation of silica microcapsules by confocal fluorescence microscopy

2015 ◽  
Vol 3 (39) ◽  
pp. 7745-7751 ◽  
Author(s):  
Judith van Wijk ◽  
Joris W. O. Salari ◽  
Jan Meuldijk ◽  
Bert Klumperman
Keyword(s):  
Fluorescence Microscopy ◽  
Shell Growth ◽  
Growth Direction ◽  
Silica Shell ◽  
Confocal Fluorescence Microscopy ◽  
Pickering Emulsions ◽  
Confocal Fluorescence

A novel procedure was developed to determine the direction of silica growth during the formation of a silica shell around aqueous microdroplets in water-in-oil Pickering emulsions, and it was found that the shell grows from the inside to the outside.

scholarly journals Understanding form and function of the stem in early flattened echinoderms (pleurocystitids) using a microstructural approach

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e1820 ◽  
Author(s):  
Przemysław Gorzelak ◽  
Samuel Zamora
Keyword(s):  
Active Mode ◽  
Form And Function ◽  
Sea Bottom ◽  
Locomotory Organ ◽  
Mode Of Life ◽  
Life Habits ◽  
And Function ◽  
Collagenous Tissues ◽  
Flexible Stem

Pleurocystitid rhombiferans are among the most unusual echinoderms whose mode of life has been long debated. These echinoderms are usually interpreted as vagile epibenthic echinoderms, moving over the sea bottom by means of a flexible stem. Although their life habits and posture are reasonably well understood, the mechanisms that control the movement of stem are highly controversial. Specifically, it is unknown whether the stem flexibility was under the control of muscles or ligamentary mutable collagenous tissues (MCTs). Here, we reconstruct palaeoanatomy of the two Ordovician pleurocystitid rhombiferans (PleurocystitesandAmecystis) based on stereom microstructure. We show that the articular facets of columnals in pleurocystitid rhombiferans are composed of fine labyrinthic stereom. Comparison with modern echinoderms suggests that this type of stereom was associated with muscles implying that their stem was a muscular locomotory organ supporting an active mode of life.

scholarly journals Low-Temperature-Induced Controllable Transversal Shell Growth of NaLnF4 Nanocrystals

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 654
Author(s):  
Deming Liu ◽  
Yan Jin ◽  
Xiaotong Dong ◽  
Lei Liu ◽  
Dayong Jin ◽  
...  
Keyword(s):  
Reaction Temperature ◽  
Lattice Mismatch ◽  
Shell Growth ◽  
Three Dimensional ◽  
Anisotropic Shell ◽  
Growth Direction ◽  
Minor Role ◽  
Growth Method ◽  
Surface Ligand ◽  
A Minor

Highly controllable anisotropic shell growth is essential for further engineering the function and properties of lanthanide-doped luminescence nanocrystals, especially in some of the advanced applications such as multi-mode bioimaging, security coding and three-dimensional (3D) display. However, the understanding of the transversal shell growth mechanism is still limited today, because the shell growth direction is impacted by multiple complex factors, such as the anisotropy of surface ligand-binding energy, anisotropic core–shell lattice mismatch, the size of cores and varied shell crystalline stability. Herein, we report a highly controlled transversal shell growth method for hexagonal sodium rare-earth tetrafluoride (β-NaLnF4) nanocrystals. Exploiting the relationship between reaction temperature and shell growth direction, we found that the shell growth direction could be tuned from longitudinal to transversal by decreasing the reaction temperature from 310 °C to 280 °C. In addition to the reaction temperature, we also discussed the roles of other factors in the transversal shell growth of nanocrystals. A suitable core size and a relative lower shell precursor concentration could promote transversal shell growth, although different shell hosts played a minor role in changing the shell growth direction.

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