Allocation of pyloric caecum reserves in FED and starved sea stars, Pisaster giganteus (Stimpson): somatic maintenance comes before reproduction

1980 ◽  
Vol 48 (2) ◽  
pp. 169-183 ◽  
Author(s):  
Christopher Harrold ◽  
John S. Pearse
Keyword(s):  
Pyloric Caecum ◽  
Sea Stars ◽  
Somatic Maintenance

A non-lethal method for estimation of gonad and pyloric caecum indices in sea stars

2009 ◽  
Vol 128 (4) ◽  
pp. 372-380 ◽  
Author(s):  
Eric Sanford ◽  
Megan E. Wood ◽  
Karina J. Nielsen
Keyword(s):  
Pyloric Caecum ◽  
Sea Stars

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

scholarly journals Sea stars generate downforce to stay attached to surfaces

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mark Hermes ◽  
Mitul Luhar
Keyword(s):  
Body Shape ◽  
Control Volume ◽  
Water Channel ◽  
Morphological Plasticity ◽  
The Body ◽  
Sea Star ◽  
Sea Stars ◽  
Hydrodynamic Loads ◽  
Spherical Dome ◽  
Star Models

AbstractIntertidal sea stars often function in environments with extreme hydrodynamic loads that can compromise their ability to remain attached to surfaces. While behavioral responses such as burrowing into sand or sheltering in rock crevices can help minimize hydrodynamic loads, previous work shows that sea stars also alter body shape in response to flow conditions. This morphological plasticity suggests that sea star body shape may play an important hydrodynamic role. In this study, we measured the fluid forces acting on surface-mounted sea star and spherical dome models in water channel tests. All sea star models created downforce, i.e., the fluid pushed the body towards the surface. In contrast, the spherical dome generated lift. We also used Particle Image Velocimetry (PIV) to measure the midplane flow field around the models. Control volume analyses based on the PIV data show that downforce arises because the sea star bodies serve as ramps that divert fluid away from the surface. These observations are further rationalized using force predictions and flow visualizations from numerical simulations. The discovery of downforce generation could explain why sea stars are shaped as they are: the pentaradial geometry aids attachment to surfaces in the presence of high hydrodynamic loads.

Patiriella pseudoexigua (Asteroidea: Asterinidae): a cryptic species complex revealed by molecular and embryological analyses

2003 ◽  
Vol 83 (5) ◽  
pp. 1109-1116 ◽  
Author(s):  
Michael W. Hart ◽  
Maria Byrne ◽  
Sheri L. Johnson
Keyword(s):  
Dna Sequences ◽  
Original Description ◽  
Sensu Stricto ◽  
Genetic Distances ◽  
New Combination ◽  
Sea Stars ◽  
Planktonic Larva ◽  
Closely Related Species ◽  
Planktonic Larvae ◽  
Cryptic Species Complex

Cryptic lineages were identified within a morphologically uniform group of sea stars distributed from Australia to Japan. Among eight populations, all of which have been referred to Patiriella pseudoexigua, we found seven unique mitochondrial DNA sequences clustered into four distinct lineages. These four lineages formed a monophyletic group in which sister clades were separated by small genetic distances but could be differentiated from each other on the basis of reproductive differences. The four lineages thus appear to be separate but very closely related species. Examination of reproduction in several Queensland populations revealed that one population (Statue Bay) consisted of hermaphroditic intragonadal brooders with live-born offspring while other populations (Townsville, Bowen, Airlie Beach) consisted of dioecious free-spawners with a planktonic larva. The brooded larvae from central Queensland populations closely resembled brooded embryos and larvae of a Japanese lineage, while the planktonic larvae from northern Queensland were similar to the original description of planktonic larvae from a Taiwan population. However, each of the viviparous lineages was more closely related to a lineage with planktonic larval development than the viviparous lineages were to each other. Patiriella pseudoexigua thus comprises at least four species with different reproductive phenotypes in which viviparous brooding appears to have evolved in parallel. Based on previous taxonomic work we propose the following names for these four lineages: the dioecious free-spawner from northern Queensland (including the P. pseudoexigua type locality) is P. pseudoexiguasensu stricto; the viviparous brooder from central Queensland is undescribed and here referred to as Patiriella sp. nov; the dioecious free-spawner from Taiwan is temporarily referred to as Patiriella sp. (a senior name for this species may be P. pentagonus); and the hermaphrodite brooder from Japan should be raised to specific status and referred to by the new combination P. pacifica.

Occurrence of Ulcerative Lesions in Sea Stars (Asteroidea) of the Northern Gulf of California, USA

2022 ◽  
Vol 58 (1) ◽  
Author(s):  
Claire Vergneau-Grosset ◽  
Raphaëlle Boudreau ◽  
Fabio Favoretto ◽  
Guy Beauchamp ◽  
Anne-Josée Chicoine ◽  
...  
Keyword(s):  
Gulf Of California ◽  
Sea Stars ◽  
Ulcerative Lesions

Biology and Ecology of Pharmaceutical Sea Stars (Class: Asteroidea)

2019 ◽  
pp. 23-170
Author(s):  
Ramasamy Santhanam ◽  
Santhanam Ramesh ◽  
Sheba Rani Nakka David
Keyword(s):  
Sea Stars

scholarly journals Ultrastructure, dissolution and "pyritization" of Late Quaternary and Recent echinoderms

1987 ◽  
Vol 36 ◽  
pp. 275-287
Author(s):  
Margit Jensen ◽  
Elsebeth Thomsen
Keyword(s):  
Late Pleistocene ◽  
Sea Water ◽  
Late Quaternary ◽  
Pore Space ◽  
Water Interface ◽  
Sea Stars ◽  
Northern Norway ◽  
History Of ◽  
Organic Tissue ◽  
Diagenetic History

The diagenetic history of the skeletal elements of Late Pleistocene-Holocene Ophiura sarsi from the shelf off northern Norway (Andfjorden, Malangsdjupet) is elucidated by comparison with natural and induced degradation of the skeletal elements of Recent ophiuroids (brittle stars) and asteroids (sea stars) from Danish waters. Dissolution features ("core-and-rind") in the trabeculae of fossil and Recent echinoderm stereom are initiated during death and early decay of organic tissue in the animals. The trabeculae have a polycrystal­line lamellar ultrastructure and lose their older central part during later stages of dissolution, which are dependant on undersaturation of the sea-water with regard to CaC03• The presence of undersaturated sea-water is supported by palaeoecological studies (Thomsen & Vorren 1984, 1986) implying oxygen deficient periods in the Late Pleistocene and an increased biogenic production in the Holocene. Pyrite framboids are situated in the secondary voids within the trabeculae and in the pore space of the stereom of the Late Pleistocene elements. No pyrite is observed within the polycrystalline lamellar ultrastructure of the trabeculae. The Late Pleistocene "pyritization" took place during oxygen deficient periods at the sediment-water interface or within the reduced zone of the topmost sediment.

scholarly journals Evidence That Supertriangles Exist in Nature from the Vertical Projections of Koelreuteria paniculata Fruit

Symmetry ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 23
Author(s):  
Yuping Li ◽  
Brady K. Quinn ◽  
Johan Gielis ◽  
Yirong Li ◽  
Peijian Shi
Keyword(s):  
Root Mean Square ◽  
Goodness Of Fit ◽  
Mean Square ◽  
Sea Stars ◽  
Different Types ◽  
Koelreuteria Paniculata ◽  
Two Parameters ◽  
Mean Square Errors

Many natural radial symmetrical shapes (e.g., sea stars) follow the Gielis equation (GE) or its twin equation (TGE). A supertriangle (three triangles arranged around a central polygon) represents such a shape, but no study has tested whether natural shapes can be represented as/are supertriangles or whether the GE or TGE can describe their shape. We collected 100 pieces of Koelreuteria paniculata fruit, which have a supertriangular shape, extracted the boundary coordinates for their vertical projections, and then fitted them with the GE and TGE. The adjusted root mean square errors (RMSEadj) of the two equations were always less than 0.08, and >70% were less than 0.05. For 57/100 fruit projections, the GE had a lower RMSEadj than the TGE, although overall differences in the goodness of fit were non-significant. However, the TGE produces more symmetrical shapes than the GE as the two parameters controlling the extent of symmetry in it are approximately equal. This work demonstrates that natural supertriangles exist, validates the use of the GE and TGE to model their shapes, and suggests that different complex radially symmetrical shapes can be generated by the same equation, implying that different types of biological symmetry may result from the same biophysical mechanisms.

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