CYTO-EMBRYOLOGICAL STUDIES OF SEA URCHINS. III. ROLE OF THE SECONDARY MESENCHYME CELLS IN THE FORMATION OF THE PRIMITIVE GUT IN SEA URCHIN LARVAE

It has long been thought that traction exerted by filopodia of secondary mesenchyme cells (SMCs) is a sufficient mechanism to account for elongation of the archenteron during sea urchin gastrulation. The filopodial traction hypothesis has been directly tested here by laser ablation of SMCs in gastrulae of the sea urchin, Lytechinus pictus. When SMCs are ablated at the onset of secondary invagination, the archenteron doubles in length at the normal rate of elongation, but advance of the tip of the archenteron stops at the 2/3 gastrula stage. In contrast, when all SMCs are ablated at or following the 2/3 gastrula stage, further elongation does not occur. However, if a few SMCs are allowed to remain in 2/3-3/4 gastrulae, elongation continues, although more slowly than in controls. The final length of archenterons in embryos ablated at the 1/3-1/2 gastrula stage is virtually identical to the final length of everted archenterons in LiCl-induced exogastrulae; since filopodial traction is not exerted in either case, an alternate, common mechanism of elongation probably operates in both cases. These results suggest that archenteron elongation involves two processes: (1) active, filopodia-independent elongation, which depends on active cell rearrangement and (2) filopodia-dependent elongation, which depends on mechanical tension exerted by the filopodia.

Download Full-text

Role of fibronectin in primary mesenchyme cell migration in the sea urchin.

The Journal of Cell Biology ◽

10.1083/jcb.101.4.1487 ◽

1985 ◽

Vol 101 (4) ◽

pp. 1487-1491 ◽

Cited By ~ 35

Author(s):

H Katow ◽

M Hayashi

Keyword(s):

Cell Migration ◽

Sea Urchin ◽

Culture Media ◽

Horse Serum ◽

Time Lapse ◽

Mesenchyme Cell ◽

Mesenchyme Cells ◽

Primary Mesenchyme Cells

We studied the effect of fibronectin (FN) on the behavior of primary mesenchyme cells isolated from sea urchin mesenchyme blastulae in vitro using a time-lapse technique. The migration of isolated primary mesenchyme cells reconstituted in seawater and horse serum is dependent on the presence or absence of exogenous FN in the culture media. The cells in FN, 4 and 40 micrograms/ml, show a high percentage of migration and migrate long distances, whereas a higher concentration of FN at 400 micrograms/ml tends to inhibit migration.

Download Full-text

Landscape configuration of seagrass meadows regulates sea urchins predation in a Marine Protected Area: what is the role of bottom predators?

10.7287/peerj.preprints.982v1 ◽

2015 ◽

Author(s):

Simone Farina ◽

Silvia Oliva ◽

Ivan Guala ◽

Rodrigo Silva ◽

Luigi Piazzi ◽

...

Keyword(s):

Predation Risk ◽

Sea Urchin ◽

Protected Area ◽

Marine Protected Area ◽

Sea Urchins ◽

Survival Rates ◽

Landscape Configuration ◽

Benthic Assemblages ◽

Seagrass Meadows

In Mediterranean benthic ecosystems of shallow water local-scale predation maintains a main control on both sea urchin population and the ecological structure of macrophyte community. The use of the habitat by local predator guild in dependence on the regional context shapes prey distributions across the environment. On rocky habitat, the sea urchin Paracentrotus lividus is widely known as prey of apex fish predators that indirectly shape the structure of benthic assemblages whereas, in structured Posidonia oceanica, P. lividus can find shelter from predators. In this study, we assessed survival rates of P. lividus in a Marine Protected Area (Sardinia) at the aim to evaluate the role of composition and configuration of landscape on its predation risk. Sites of different landscapes were selected in function of their heterogeneity estimated according to the different proportions and spatial interspersion of four classes of habitats defined on the basis of P. oceanica meadows arrangement: (1) continuous, (2) fragmented and (3) patchy meadows and (4) absence of seagrass (i.e. rocky bottom with macroalgae communities). In order to capture the domain of the ecological process a sampling grain 5x5 meters was used as minimal spatial resolution at which information is assessed. Specifically continuous sampling units in a grid of 7x7 cells yield landscape quadrats of 35 × 35 m and allowed a finer description of the spatial pattern. For each cell we also estimated structural variables of seagrass habitats such as unburied mat, shoot density, canopy height, cover percent, roughness and the natural abundances of prey and predators. After placing the tagged sea urchins, we daily observed the survival rates for twenty days. Predation risk was significantly higher in continuous and fragmented seagrass habitats and predator marks were typically produced by gastropod’s attacks. Landscape indices are used to correlate the amount of available habitat for gastropods movements with sea urchin’s predation risk. Interestingly, estimated predation rate also was negatively correlated with natural sea urchins density across grid cells. Results suggest that, although fishes are considered among the most important pressures on sea urchin population, especially in effective MPAs, bottom predators’ control can be relevant in structurally complex environment such as seagrasses.

Download Full-text

Landscape configuration of seagrass meadows regulates sea urchins predation in a Marine Protected Area: what is the role of bottom predators?

10.7287/peerj.preprints.982 ◽

2015 ◽

Author(s):

Simone Farina ◽

Silvia Oliva ◽

Ivan Guala ◽

Rodrigo Silva ◽

Luigi Piazzi ◽

...

Keyword(s):

Predation Risk ◽

Sea Urchin ◽

Protected Area ◽

Marine Protected Area ◽

Sea Urchins ◽

Survival Rates ◽

Landscape Configuration ◽

Benthic Assemblages ◽

Seagrass Meadows

In Mediterranean benthic ecosystems of shallow water local-scale predation maintains a main control on both sea urchin population and the ecological structure of macrophyte community. The use of the habitat by local predator guild in dependence on the regional context shapes prey distributions across the environment. On rocky habitat, the sea urchin Paracentrotus lividus is widely known as prey of apex fish predators that indirectly shape the structure of benthic assemblages whereas, in structured Posidonia oceanica, P. lividus can find shelter from predators. In this study, we assessed survival rates of P. lividus in a Marine Protected Area (Sardinia) at the aim to evaluate the role of composition and configuration of landscape on its predation risk. Sites of different landscapes were selected in function of their heterogeneity estimated according to the different proportions and spatial interspersion of four classes of habitats defined on the basis of P. oceanica meadows arrangement: (1) continuous, (2) fragmented and (3) patchy meadows and (4) absence of seagrass (i.e. rocky bottom with macroalgae communities). In order to capture the domain of the ecological process a sampling grain 5x5 meters was used as minimal spatial resolution at which information is assessed. Specifically continuous sampling units in a grid of 7x7 cells yield landscape quadrats of 35 × 35 m and allowed a finer description of the spatial pattern. For each cell we also estimated structural variables of seagrass habitats such as unburied mat, shoot density, canopy height, cover percent, roughness and the natural abundances of prey and predators. After placing the tagged sea urchins, we daily observed the survival rates for twenty days. Predation risk was significantly higher in continuous and fragmented seagrass habitats and predator marks were typically produced by gastropod’s attacks. Landscape indices are used to correlate the amount of available habitat for gastropods movements with sea urchin’s predation risk. Interestingly, estimated predation rate also was negatively correlated with natural sea urchins density across grid cells. Results suggest that, although fishes are considered among the most important pressures on sea urchin population, especially in effective MPAs, bottom predators’ control can be relevant in structurally complex environment such as seagrasses.

Download Full-text

Estrogen administration to the edible sea urchin Paracentrotus lividus (Lamarck, 1816)*

Zoosymposia ◽

10.11646/zoosymposia.7.1.23 ◽

2012 ◽

Vol 7 (1) ◽

pp. 247-254 ◽

Cited By ~ 1

Author(s):

SILVIA MERCURIO ◽

MICHELA SUGNI ◽

DENISE FERNANDES ◽

CINTA PORTE ◽

MARIA DANIELA CANDIA CARNEVALI

Keyword(s):

Sea Urchin ◽

Sea Urchins ◽

Gonad Index ◽

Hormonal Treatment ◽

Paracentrotus Lividus ◽

Maturation Stage ◽

Physiological Values ◽

Estrogen Administration

Despite the extensive use of sea urchins in embryology, the hormonal mechanisms regulating echinoid reproductive processes are scarcely known. This research is focused on the role of estradiol (E2), whose presence and seasonal variations in different echinoderm tissues have been previously reported. Three different concentrations of E2 were administered (via peristomial injection, 2/week) to adult specimens of the sea urchin Paracentrotus lividus for 2 and 12 weeks. The lowest concentration was close to physiological values, previously measured in field specimens. Despite the increase of circulating E2 in the coelomic fluids, neither short- nor long-term hormonal treatment induced marked variations in the considered reproductive parameters. The Gonad Index appeared to be more influenced by the feed intake than by E2. Similarly, the maturation stage of the gonads was not markedly affected by E2 injection, although some sex-specific differences could be observed: treated females never reached the maximum maturation stage compared to controls, although this was observed in males injected with the lowest E2 concentration. Although further research is needed to confirm our observations, according to the present study E2 does not markedly influence echinoid reproduction and, particularly, it does not promote female maturation, as reported for vertebrates and suggested for asteroid echinoderms.

Download Full-text

PERAN EKOLOGI BULU BABI DALAM KOMUNITAS RUMPUT LAUT DI PERAIRAN PESISIR KEMA KABUPATEN MINAHASA UTARA

JURNAL PERIKANAN DAN KELAUTAN TROPIS ◽

10.35800/jpkt.7.1.2011.18 ◽

2011 ◽

Vol 7 (1) ◽

pp. 1

Author(s):

Ruddy D Moningkey

Keyword(s):

Sea Urchin ◽

Functional Role ◽

Food Preference ◽

Negative Impact ◽

Sea Urchins ◽

Gut Contents ◽

Seagrass Bed ◽

Transect Line ◽

Feeding Periodicity

A study on the functional role of the sea urchin, Salmacis belli, on seagrass bed near the coast of Kema, North Minahasa Regency, was done by analyzing the gut contents, the food preference, and the feeding periodicity. Sea urchins and plants were collected from the seagrass bed by snorkeling along a 100 M transect line with 30 quadrates randomly placed. The feeding periodicity was determined from the gut index in 24 hours with 3 hour intervals. The results showed that the sea urchin S. belli fed mainly on seagrass Thallasia hemprichii, Enhalus acoroides and Halimeda opuntioa. The feeding periodicity data indicated that the sea urchins actively fed in the day. The grazing capacity of the sea urchin was not affected by their body size. In high density, sea urchins could potentially cause negative impact on the seagrass bed (i.e., destruction of the meadow).

Download Full-text

Determination and morphogenesis in the sea urchin embryo

Development ◽

10.1242/dev.100.4.559 ◽

1987 ◽

Vol 100 (4) ◽

pp. 559-576 ◽

Cited By ~ 10

Author(s):

F.H. Wilt

Keyword(s):

Sea Urchin ◽

Sea Urchins ◽

Secondary Phase ◽

Animal Cells ◽

Sea Urchin Embryo ◽

Defect Isolation ◽

Normal Larva ◽

Mesenchyme Cells ◽

The Stability ◽

Almost All

The study of the sea urchin embryo has contributed importantly to our ideas about embryogenesis. This essay re-examines some issues where the concerns of classical experimental embryology and cell and molecular biology converge. The sea urchin egg has an inherent animal-vegetal polarity. An egg fragment that contains both animal and vegetal material will produce a fairly normal larva. However, it is not clear to what extent the oral-aboral axis is specified in embryos developing from meridional fragments. Newly available markers of the oral-aboral axis allow this issue to be settled. When equatorial halves, in which animal and vegetal hemispheres are separated, are allowed to develop, the animal half forms a ciliated hollow ball. The vegetal half, however, often forms a complete embryo. This result is not in accord with the double gradient model of animal and vegetal characteristics that has been used to interpret almost all defect, isolation and transplantation experiments using sea urchin embryos. The effects of agents used to animalize and vegetalize embryos are also due for re-examination. The classical animalizing agent, Zn2+, causes developmental arrest, not expression of animal characters. On the other hand, Li+, a vegetalizing agent, probably changes the determination of animal cells. The stability of these early determinative steps may be examined in dissociation-reaggregation experiments, but this technique has not been exploited extensively. The morphogenetic movements of primary mesenchyme are complex and involve a number of interactions. It is curious that primary mesenchyme is dispensable in skeleton formation since in embryos devoid of primary mesenchyme, the secondary mesenchyme cells will form skeletal elements. It is likely that during its differentiation the primary mesenchyme provides some of its own extracellular microenvironment in the form of collagen and proteoglycans. The detailed form of spicules made by primary mesenchyme is determined by cooperation between the epithelial body wall, the extracellular material and the inherent properties of primary mesenchyme cells. Gastrulation in sea urchins is a two-step process. The first invagination is a buckling, the mechanism of which is not understood. The secondary phase in which the archenteron elongates across the blastocoel is probably driven primarily by active cell repacking. The extracellular matrix is important for this repacking to occur, but the basis of the cellular-environmental interaction is not understood.(ABSTRACT TRUNCATED AT 400 WORDS)

Download Full-text

The origin of spicule-forming cells in a ‘primitive’ sea urchin (Eucidaris tribuloides) which appears to lack primary mesenchyme cells

Development ◽

10.1242/dev.103.2.305 ◽

1988 ◽

Vol 103 (2) ◽

pp. 305-315 ◽

Cited By ~ 7

Author(s):

G.A. Wray ◽

D.R. McClay

Keyword(s):

Sea Urchin ◽

Sea Urchins ◽

Cell Lineage ◽

Cell Types ◽

Morphological Evidence ◽

Specific Gene ◽

Apparent Paradox ◽

Mesenchyme Cells ◽

Lineage Specific Gene ◽

Primary Mesenchyme Cells

The calcareous larval skeleton of euechinoid sea urchins is synthesized by primary mesenchyme cells which ingress prior to gastrulation. In embryos of the cidaroid sea urchin Eucidaris tribuloides, no mesenchyme cells ingress before gastrulation, yet larvae later contain skeletons. This apparent paradox is resolved by immunochemical, cell lineage and morphological evidence showing that spicule-forming cells of Eucidaris are homologous to primary mesenchyme cells of euechinoids. In particular, these two cell types share expression of two cell lineage-specific gene products, are derived from the same cellular precursors, the micromeres, and undergo a similar migratory phase prior to skeletogenesis. Despite these similarities, there are far fewer spicule-forming cells in Eucidaris than in typical euechinoids and they assume a different pattern during spiculogenesis. The homology between Eucidaris spicule-forming cells and euechinoid primary mesenchyme cells indicates that a heterochrony in the time of spicule-forming cell ingression has occurred since the divergence of their respective lineages.

Download Full-text

Cellular bicarbonate accumulation and vesicular proton transport promote calcification in the sea urchin larva

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.1506 ◽

2020 ◽

Vol 287 (1934) ◽

pp. 20201506

Author(s):

Marian Y. Hu ◽

Inga Petersen ◽

William Weijen Chang ◽

Christine Blurton ◽

Meike Stumpp

Keyword(s):

Sea Urchin ◽

Fluorescent Protein ◽

Marine Species ◽

Ph Homeostasis ◽

Amorphous Calcium Carbonate ◽

Regulatory Strategies ◽

Sea Urchin Embryo ◽

Mesenchyme Cells ◽

Green Fluorescent

The sea urchin embryo develops a calcitic endoskeleton through intracellular formation of amorphous calcium carbonate (ACC). Intracellular precipitation of ACC, requires HCO 3 − / CO 3 2 − concentrating as well as proton export mechanisms to promote calcification. These processes are of fundamental importance in biological mineralization, but remain largely unexplored. Here, we demonstrate that the calcifying primary mesenchyme cells (PMCs) use Na + /H + -exchange (NHE) mechanisms to control cellular pH homeostasis during maintenance of the skeleton. During skeleton re-calcification, pH i of PMCs is increased accompanied by substantial elevation in intracellular [ HCO 3 − ] mediated by the N a + / HCO 3 − cotransporter Sp_Slc4a10. However, PMCs lower their pH i regulatory capacities associated with a reduction in NHE activity. Live-cell imaging using green fluorescent protein reporter constructs in combination with intravesicular pH measurements demonstrated alkaline and acidic populations of vesicles in PMCs and extensive trafficking of large V -type H + -ATPase (VHA)-rich acidic vesicles in blastocoelar filopodial cells. Pharmacological and gene expression analyses underline a central role of the VHA isoforms Sp_ATP6V0a1 , Sp_ATP6V01_1 and Sp_ATPa1-4 for the process of skeleton re-calcification. These results highlight novel pH regulatory strategies in calcifying cells of a marine species with important implications for our understanding of the mineralization process in times of rapid changes in oceanic pH.

Download Full-text

IL17 factors are early regulators in the gut epithelium during inflammatory response to Vibrio in the sea urchin larva

eLife ◽

10.7554/elife.23481 ◽

2017 ◽

Vol 6 ◽

Cited By ~ 24

Author(s):

Katherine M Buckley ◽

Eric Chun Hei Ho ◽

Taku Hibino ◽

Catherine S Schrankel ◽

Nicholas W Schuh ◽

...

Keyword(s):

Immune Response ◽

Inflammatory Response ◽

Sea Urchin ◽

Immune Cells ◽

Sea Urchins ◽

Purple Sea Urchin ◽

Gut Epithelium

IL17 cytokines are central mediators of mammalian immunity. In vertebrates, these factors derive from diverse cellular sources. Sea urchins share a molecular heritage with chordates that includes the IL17 system. Here, we characterize the role of epithelial expression of IL17 in the larval gut-associated immune response. The purple sea urchin genome encodes 10 IL17 subfamilies (35 genes) and 2 IL17 receptors. Most of these subfamilies are conserved throughout echinoderms. Two IL17 subfamilies are sequentially strongly upregulated and attenuated in the gut epithelium in response to bacterial disturbance. IL17R1 signal perturbation results in reduced expression of several response genes including an IL17 subtype, indicating a potential feedback. A third IL17 subfamily is activated in adult immune cells indicating that expression in immune cells and epithelia is divided among families. The larva provides a tractable model to investigate the regulation and consequences of gut epithelial IL17 expression across the organism.

Download Full-text