Temnopleurus Toreumaticus Research Articles

Revealing the cells fated to form the cell mass in embryos of temnopleurid sea urchins

Larvae of temnopleurid sea urchins form a cell mass (CM) instead of an amniotic cavity on the left side at the early developmental stage for formation of the adult rudiment. However, the cell lineage and the mechanisms that form the CM are still unknown. We analyzed the potential to form a CM in partial embryos resulting from microsurgeries, using two temnopleurid species, Mespilia globulus (L.) and Temnopleurus toreumaticus (Leske). CM formation was completed 28-34 h after fertilization at 24°C, corresponding to the period from the late prism to the two-armed pluteus larval stages in both species. In the case of specimens dissected horizontally during the mesenchyme blastula to prism stages, the CM was formed in partial embryos containing enough of the an2 region, a part of the precursor cells that differentiate the ectoderm. The proportion of specimens with a CM was higher in T. toreumaticus than in M. globulus. Additionally, all larvae derived from half embryos obtained from dissection along the animal-vegetal axis at the mesenchyme blastula stage formed the CM. Transplantation of a stained animal or vegetal hemisphere at the 16-cell stage into a nonstained vegetal or animal embryo indicated that the CM derives from the animal half. Exogastrulae vegetalized by lithium chloride treatment did not form the CM. These results indicate that the CM formation is dependent not only on the an2 region but also on signals from the vegetal region after the mesenchyme blastula stage.

Regeneration of the cell mass in larvae of temnopleurid sea urchins

Mechanisms of cell mass (CM) formation were analyzed by microsurgery in two temnopleurid sea urchins, Mespilia globulus and Temnopleurus toreumaticus. The CM in temnopleurids is formed at the early larval stage from the left ectodermal invagination, and with the hydrocoel derived from the mesoderm, forms an adult rudiment. After serial removal of the CM, it was strongly regenerated until its attachment to the hydrocoel, with the same timing as in control larvae. Embryos that had the tip of the archenteron or the coelomic pouches removed formed a CM in the normal manner. Removal of the CM plus the left somatocoel or the hydrocoel allowed CM regeneration with and without adult rudiment formation. A transplanted CM enlarged autonomously but did not contribute to adult rudiment formation, and larvae formed a new CM. Our observations suggest that the hydrocoel recognizes its distance from the CM to induce the growth of the CM and controls the normal timing of adult rudiment formation.

An annotated species list of regular echinoids from Sri Lanka with notes on some rarely seen temnopleurids.

The first recorded regular echinoid species from Sri Lanka, “Salmacis virgulatus” (now known as S. virgulata L. Agassiz in L. Agassiz & Desor, 1846), was listed by Agassiz & Desor (1846). Knowledge of Sri Lankan regular echinoids continued to advance until the end of the 19th century. However, there is a gap in knowledge between the mid-20th and the beginning of the 21st centuries due to a lack of systematic studies, with the exception of two checklists published by the IUCN Red List in 2006 and 2012. In the present study, we compiled a species list combining published data and new data based on fieldwork between 2013 and 2015. Echinoids were sampled by snorkelling, diving, examination of fisheries bycatch, and collection of tests from beaches. The updated species list presented in this study includes 39 regular echinoids belonging to 28 genera, nine families, and five orders. Phyllacanthus imperialis (Lamarck, 1816) and Temnopleurus toreumaticus (Leske, 1778), which were not recorded during the last 90 years, were confirmed to still occur in Sri Lanka by the present study. We develop an updated species list of regular echinoids to form a basis for future systematic work. The study recommends further investigation to evaluate the status of deep-sea species and additional field work off the northern and eastern coasts of Sri Lanka.

Ehinoid landings at Mandapam, south-east coast of India with a note on gonadal maturity of two species of sea urchins

The sea urchins, belonging to phylum Echinodermata, are a good source of “roe”, (gonads) and are being consumed by humans since pre-historic times. In many countries of the world, it is a delicacy among the food items and in retail markets in Japan, it is sold at prices as high as US$ 600 kg-1. Among the 800 species of echinoids, 105 species are found along the east coast of India and 30 species are recorded along the coast of Tamil Nadu. There is a paucity of information on the biology and ecology of sea urchins and lack of studies on its edibility and palatability. The sea urchin aquaculture called as echiniculture is picking up in subtropics and temperate areas. Importantly, the tropical marine ecosystem of India, which supports diverse flora and fauna is a suitable environment for echiniculture, and the future research needs to be focused to find out the potential species and developing techniques for their aquaculture. The present investigation analysed the landings of echinoderms in the Gulf of Mannar and Palk Bay along the south-east coast of India and also studied the gonadal maturity of two species of sea urchins viz., Salmacis virgulata and Temnopleurus toreumaticus in order to assess their suitability for echiniculture. S. virgulata and T. toreumaticus formed 70 and 30% respectively of the sea urchins landings at Vedalai and Pampan landing centres. The overall sex ratio of both the species did not deviate significantly from 1:1. In S. virgulata the mean monthly gonad index was highest (9.62±0.46) during September 2014 and for T. toreumaticus, the peak GSI was observed during December 2013. Further studies on captive maturation and breeding are needed to explore the potential of these species for echiniculture.

Specification of Larval Axes of Partial Embryos in the Temnopleurid Temnopleurus toreumaticus and the Strongylocentroid Hemicentrotus pulcherrimus.

Many sea urchins, including the strongylocentroid Hemicentrotus pulcherrimus, produce an amniotic cavity on the left for adult rudiment formation at the late larval stage. In contrast, temnopleurids form a cell mass at the early larval stage instead of an amniotic cavity. Although the mechanisms establishing left-right polarity of the amniotic cavity involve cell-cell interactions and signaling pathways, corresponding pathways for the cell mass are unknown. We analyzed the effects of blastomere isolation on the specification of larval axes in the temnopleurid Temnopleurus toreumaticus and compared them to those in H. pulcherrimus. Blastomere isolation at the two- or four-cell stages in T. toreumaticus disturbed the location of the cell mass and adult rudiment in approximately 10-20% of specimens. In contrast, isolation at the two-cell stage in H. pulcherrimus caused the left-right polarity to become random. When blastomeres isolated at the two-cell stage were cultured as pairs, approximately 20% of pairs had atypical polarity in both species. Following isolation at the four-cell stage, 71.4% of quartets produced larvae with atypical polarity in T. toreumaticus. Thus, cell-cell interaction between two daughter blastomeres after the second cleavage may be involved in the mechanism determining left-right polarity. Dye injection into a blastomere and subsequent observations indicated that the location of the boundary of the first cleavage showed similar patterns in both species. These observations suggest that species-specific mechanisms establish the larval axes and blastomeres at the two- and four-cell stages redistribute their cytoplasm, forming gradients that establish left-right polarity.

Contribution to the knowledge of echinoid fauna from Persian Gulf (Echinodermata: Echinoidea)

Species identification is always important. Records of sea urchins and sand dollars species ‎‎(Echinodermata, Echinoidea) is given from Iranian waters. Nine Species of Echinoderms were ‎identified through the study. The species identification was made using morphological ‎characteristics and review of checklist key. Nine species were identified here, including ‎Echinometra mathaei, Prionocidaris baculosa, Temnopleurus toreumaticus, Echinothrix ‎calamaris, Clypeaster humilis, Echinodiscus auritus, Diadema setosum, Diadema savignyi and ‎Parasalenia gratiosa of which three species namely Echinothrix calamaris, Diadema savignyi ‎and Parasalenia gratiosa were new records to Persian Gulf.‎

Morphological diversity of blastula formation and gastrulation in temnopleurid sea urchins.

ABSTRACTEmbryos of temnopleurid sea urchins exhibit species-specific morphologies. While Temnopleurus toreumaticus has a wrinkled blastula and then invaginates continuously at gastrulation, others have a smooth blastula and their invagination is stepwise. We studied blastula and gastrula formation in four temnopleurids using light and scanning electron microscopy to clarify the mechanisms producing these differences. Unlike T. toreumaticus, blastomeres of mid-blastulae in T. reevesii, T. hardwickii and Mespilia globulus formed pseudopods. Before primary mesenchyme cells ingressed, embryos developed an area of orbicular cells in the vegetal plate. The cells surrounding the orbicular cells extended pseudopods toward the orbicular cell area in three Temnopleurus species. In T. toreumaticus, the extracellular matrix was well-developed and developed a hole-like structure that was not formed in others. Gastrulation of T. reevesii, T. hardwickii and M. globulus was stepwise, suggesting that differences of gastrulation are caused by all or some of the following factors: change of cell shape, rearrangement, pushing up and towing of cells. We conclude that (1) many aspects of early morphogenesis differ even among very closely related sea urchins with indirect development and (2) many of these differences may be caused by the cell shape and structure of blastomeres or by differences in extracellular matrix composition.

Influence of Sea Surface Temperature on the Gonadal Development of Sea Urchin Temnopleurus Toreumaticus from the Gulf of Mannar, South East Coast of India

This study was conducted for a 20 months period from October 2013 to May 2015 in Gulf of Mannar, south east coast of India. During the investigation the abiotic factors viz., Sea surface temperature (SST), Daylight photoperiod and atmospheric temperature data were collected from International comprehensive Ocean Atmospheric Database (ICOADS) and the reproductive cycle of the sea urchin was studied from the monthly sampling of sea urchin collected from Vedalai landing centre in Gulf of Mannar. The gonads were studied to calculate Gonad index as well histological to categories them into four different stages of the development and this data was compared with abiotic factors to study the influence of it on the reproductive behavior of sea urchin. The data were analyzed statistically through Pearson correlation and it was found negative between mean monthly gonad index and day length photoperiod, as well as with SST. This clearly indicates that the gonadal development in sea urchin is very much influenced by these two abiotic factors; however other nutritional factors might play greater role in the development gonad.

Development of the sea urchins Temnopleurus toreumaticus Leske, 1778 and Temnopleurus reevesii Gray, 1855 (Camarodonta: Temnopleuridae)

Sea urchin larvae near metamorphosis form an adult rudiment that is a complex of the juvenile structures. However, the details of the mechanisms that form the adult rudiment are unknown. The temnopleurid sea urchins Temnopleurus toreumaticus and Temnopleurus reevesii occur in Japan, but the development of their juvenile morphology has not been described. In this study, we observed their development by light and scanning electron microscopy to follow the adult rudiment formation and to consider the mechanisms of evolution of juvenile morphology in sea urchins. The prism embryos of both species formed two primary pore canals that elongated from the left and right coelomic sacs; the left canal connected the presumptive water vascular system to the hydropore. These organs were formed bilaterally and symmetrically in T. toreumaticus and with left-right asymmetry in T. reevesii. The right canal of both species had degenerated by the four-armed larval stage. At the prism stage, about six cells from the left oral ectoderm located between the left post-oral arm and the oral lobe formed a cell mass. The cell mass grew in diameter stepwise in T. toreumaticus by cell migration and by the formation of an epithelial pouch during the four- to six-armed larval stages and more rapidly in T. reevesii by the formation of a thin epithelium during the six-armed larval stage. In both species, the adult rudiment was formed by attachment of the cell mass to the hydrocoel. The larvae of T. toreumaticus metamorphosed from a tiny hole on the left ectoderm between the post-oral and postero-dorsal arms. These findings suggest that the developmental process involving the formation of two primary pore canals and a cell mass may have been acquired and conserved as common traits in the early development of indirect-developing temnopleurid species during evolutionary divergence from the Cidaroida.

A New Record ofTemnopleurus decipiens(de Meijere, 1904) (Echinoidea, Temnopleuroida, Temnopleuridae) from Indian Waters

The first report of the sea urchin (Echinodermata, Echinoidea) species, Temnopleurus decipiens (de Meijere, 1904) is given from Indian waters (Goa, west coast of India). A complete redescription of the species has been made based on test morphology using 27 phenotypic parameters. This species differs from the original description in that “the ocular plates do not reach the periproct margin.” A detailed comparison with another congener, namely Temnopleurus toreumaticus (Leske, 1778) revealed that apart from the position of the anus and the presence of a suranal plate, notable differences were also observed in the diameter of the apical system, plan of sutural pits, pore-pairs structure, ratio of spine length to maximum test diameter, and colour banding of the spines. Further, the paper provides a modified taxonomic key to all the seven extant species of the genus Temnopleurus L. Agassiz, 1841 with two additional characters.

Novel Morphological Traits in the Early Developmental Stages of Temnopleurus toreumaticus

We have re-observed in detail the development of the sea urchin species Temnopleurus toreumaticus, which is considered to be a typical indirect-developing species with a feeding larval stage. In this re-observation, we discovered two new morphological traits in the early embryonic stages of T. toreumaticus. The first trait is that, immediately after fertilization, the egg enters a stage in which wrinkles form on its surface as a result of actin polymerization. The second new trait is that the blastulae form wrinkles; in sea urchins, this has previously been known only in direct-developing species that have a nonfeeding larval stage and form wrinkles during the blastula stage, before hatching. These phenomena indicate that after fertilization, the egg of T. toreumaticus undergoes a surface transformation that is unprecedented in echinoderms, and that an indirect-developing sea urchin can form a wrinkled blastula.

Macrobenthos of Kakinada Bay in the Godavari delta, East coast of India: comparing decadal changes

A one-year study (1995–1996) on the macrobenthos over a spread of (37) hydrographically differing GPS-fixed sites in Kakinada Bay (mean salinity 27.16±0.4) and adjacent mangrove channels (14.78±0.55) in the Godavari delta, one of India's largest estuarine systems, revealed a great preponderance of benthic life. There were 11 diverse taxa represented by 95 species collected through several (303) grab and dredge hauls. Based on Bray-Curtis similarity through hierarchical clustering implemented in PRIMER, it was possible to distinguish the benthos into four assemblages each of which represented sites in the Central and North bay ( Paphia textrix – Typhlocarcinus sp. Assemblage), South-East bay ( Protankyra similis – Paphia malabarica Assemblage), Mangrove Outlets ( Cerithidea cingulata Assemblage) and Mangrove channels ( Diopatra neapolitana Assemblage). Benthos densities (mean nos. dredge haul −1) were highest (299 individuals) at sites close to mangrove outlets. Species diversity (Margalef, d; Shannon-Wiener, H′) was low in general ( d 1.244 to 2.251 and H′ 0.038 to 1.502). Sediments were mostly clayey-silt in nature except in southeast bay where they are silt-sand. Organic matter (mean) was at or near 1.3%. The observations have revealed marked changes in benthic community structure relative to an earlier investigation held in 1958–1963 in this area. Over the years, species such as Turritella duplicata, Tonna dolium and Placuna placenta found in considerable numbers previously have dwindled. Anomia, Bursa and Atrina and echinoderms, Astropecten indica, Echinodiscus auritus and Temnopleurus toreumaticus and the brachiopod, Lingula sp. of common occurrence in early 60s are absent altogether attributable to long-term natural trends during the intervening years and/or events accompanying human impingement (e.g. industrial and urban growth, port expansion measures, aquaculture, mangrove denudation etc.). Despite such large-scale alterations in benthos community structure, there were no significant changes in “biodiversity” measured through Average Taxonomic Distinctness (AvTD) and Variation in Taxonomic Distinctness (VarTD). The investigation revealed that AvTD (Δ +) and VarTD (Λ +) for previous years and the present study remained well within the 95% confidence funnel implying taxonomic stability. It was found that species, which had replaced the earlier forms, were drawn from comparable (Linnean) hierarchy i.e. same phylum/class.

An approach to the phylogeny of the order Echinoida using interf amily hybrids

Order Echinoida in Japan is now classified into the following five families: Temnopleuridae, Toxo-pneustidae, Strongylocentrotidae, Echinometridae and Parasaleniidae. With the exception of the Parasaleniidae, four of the families are commonly found in shallow waters in Japan. Interrelationships among these four families have been extensively studied by many workers using morphological criteria or at the biochemical and molecular levels, and four different theories have been proposed (Jensen, 1981; Smith, 1984; Mortensen, 1928–1951; Shigei, 1986; Matsuoka, 1988). To examine these theories, I attempted to obtain hybrids using 14 species (4 species of the family Temnopleuridae: Temnopleurus toreumaticus, Temnopleurus hardwickii, Temnopleurus reeversii and Mespilia globulus; 3 species of the family Toxopneustidae: Toxopneustes pileolus, Tripneustes gratilla and Pseudoboletia maculata; 4 species of the family Strongylocentrotidae: Strongylocentrotus intermedius, Strongylocentrotus nudus, Hemicentrotus pulcherrimus and Pseudocentrotus depressus; and 3 species of the family Echinometridae: Anthocidaris crassispina, Echinostrephus aciculatus and Echinometra mathaei).

Temnosides A and B, Two New Glycosphingolipids from the Sea Urchin Temnopleurus toreumaticus of the Indian Coast

Two new glycosphingolipids, temnosides A (1) and B (2), have been isolated from a MeOH extract of the sea urchin Temnopleurus toreumaticus. The proposed structures 1-O-(β-d-glucopyranosyl)-d-(+)-(2S,3R)-2-[(2‘(R)-hydroxytricosanoyl]amido]-1,3-eicosanediol (1) and 1-O-(β-d-glucopyranosyl)-d-(+)-(2S,3R)-2-(docosanoylamido)-1,3-eicosanediol (2) were established by FABMS, 2D NMR, and chemical degradation studies.

Phylogenetic relationships of echinoids of the family Temnopleuridae inferred from allozyme variation.

The family Temnopleuridae of the order Echinoida from Japanese waters is represented by the four echinoid species belonging to the two different genera: Temnopleurus toreumaticus, T. hardwickii, T. reevesii, and Mespilia globulus. Their phylogenetic relationships were investigated by electrophoretic analyses of 16 different enzymes. From the allozyme variation in 30 genetic loci, the Nei's genetic distances between species were caluculated and the molecular phylogenetic tree for the four species was constructed. The phylogenetic tree indicated the following: (1) Among four species of the family, T. toreumaticus and T. reevesii are the most closely related to each other and diverged later. (2) T. hardwickii is more genetically differentiated from the other two congeners. (3) M. globulus is the most distant species of the four members. These allozyme results were discussed through the comparison with other non-molecular evidence, and the divergence process of the four echinoid species was speculated.

Detection and characterization of the cis-element in the first intron of the Ars gene in the sea urchin.

Cis-active elements that are related to temporal regulation of the Ars gene expression in embryos of the sea urchin, Hemicentrotus pulcherrimus, are localized in the region between -252 b and +38b. This promoter region, however, can only determine the onset of gene transcription at a defined period in sea urchin development, and cannot determine the level of the Ars gene transcription. The element that enhances Ars promoter activity is found in the first intron of the Ars gene. The first intron element of H. pulcherrimus shows a similar level of activity when introduced in embryos of another species of sea urchin, Temnopleurus toreumaticus. The size of the first intron element is determined to be 229 b.

SYNCHRONIZED RHYTHMIC CONTRACTIONS AMONG FIVE GONADAL LOBES IN THE SHEDDING SEA URCHINS: COORDINATIVE FUNCTION OF THE ABORAL NERVE RING

The gonadal lobe of the spontaneously shedding sea urchin, Temnopleurus toreumaticus, contracts rhythmically. The gonadal movement following electrical or KCl stimulation is a summed response of the rhythmic and arrhythmic contractions. The lobes pretreated with MgCl2 show only the latter type. Contraction induced by acetylcholine is the latter type. The aboral nerve ring (ANR) connects proximal ends of five gonoducts. In a preparation with intact ANR, the rhythmic contraction occurs synchronously in all five gonadal lobes. When the ANR is separated into two sectors, lobes belonging to the same sector contract synchronously, but those belonging to the different sectors do not.These results demonstrate rhythm generators (pacemakers) in the ANR that are responsible for individual and synchronous contractions among the gonadal lobes.

Asynchronization of Cell Division is Concurrently Related with Ciliogenesis in Sea Urchin Blastulae: (division synchrony/ciliogenesis/intercleavage time/transition probability/ sea urchin blastula).

During the early development of the sea urchins, Temnopleurus toreumaticus, Temnopleurus hardwickii and Hemicentrotus pulcherrimus, the division synchrony in all blastomeres lasted only until the 4th cleavage and a regional synchrony or a graded activity of cell division appeared. In the midblastula stage prior to hatching, the regional synchrony vanished simultaneously with the formation of cilia, then the division proceeded asynchronously. The analysis of cell pedigrees confirmed that a variable extension of intercleavage times occurred after the ciliogenesis. In blastomeres derived from mesomeres of T. toreumaticus embryos, the mean intercleavage time extended from 48 min of the 8th cycle (pre-ciliated) to 115 min of the 9th cycle (ciliated), and the coefficient of variation increased from 15% to 39%. We attempted a kinetic analysis of cell proliferation on the basis of the transition probability model of cell cycle control. We concluded that the minimum time required for the completion of the cell cycle was the decisive factor in the cell cycle succession of pre-ciliated blastomeres, and that a sudden and sharp decrease in the transition probability of the ciliated blastomeres probably interpreted the abrupt slowing and asynchronization of the cleavage cycle at the time of ciliogenesis.

RELATIONSHIPS BETWEEN DISTRIBUTION OF TUBULIN-PARACRYSTALS, GRANULES STAINING WITH NEUTRAL RED AND CLEAVAGE ACTIVITY IN SEA URCHIN EGG-FRAGMENTS1, 2.

Unfertilized eggs of Japanese sea urchins (Temnopleurus toreumaticus and Hemicentrotus pulcherrimus)were separated by centrifugation into two fractions (nucleated light and enucleated heavy fragments) or three fractions (nucleated light, enucleated middle, and enucleated heavy fragments). These fragments were stained with neutral red and then fertilized. Cleavage took place only in fragments containing cytoplasmic granules staining with neutral red: no cleavage occurred in fragment without these granules. When fragments of unfertilized eggs were incubated in a solution in sea water of 10-4 M vinblastine, a mitotic poison that specifically binds to tubulin, tubulin-paracrystals were found in all kinds of fragments, irrespective of whether they had stained granules and cleavage activity. These results suggest that lack of cleavage activity in the fragments is not due to the absence of polymerizable tubulin molecules in the cytoplasm, but rather to other factors, such as the absence of granules staining with neutral red. In other words, there is no relation between the distribution of these granules and polymerizable tubulin, but a close relation between the number of stainable granules and cleavage activity. Quantitative analysis of tubulin molecules in the egg fragments is necessary for confirmation of this idea.

SPECIES SPECIFIC PATTERN OF CILIOGENESIS IN DEVELOPING SEA URCHIN EMBRYOS.

The events of cell division and ciliogenesis in individual blastomeres of developing embryos of the sea urchins Temnopleurus toreumaticus and Hemicentrotus pulcherrimus were followed with a Nomarski differential interference microscope. The number of cell divisions before initiation of ciliogenesis was determined with respect to species. In T. toreumaticus, ciliogenesis began about 4 hr after fertilization at 25°C. The sequence of ciliogenesis was as follows: cilia appeared first on smaller micromeres, followed in order by blastomeres derived from larger micromeres, those from mesomeres and finally those derived from macromeres. Blastomeres originating from mesomeres, macromeres, larger micromeres and smaller micromeres had completed the 8th, 9th, 7th and 5th divisions respectively, before they generated cilia. In H. pulcherrimus, embryos started to form cilia about 9 hr after fertilization at 18°C. Cilia appeared first on blastomeres of mesomere origin and, then on those of macromere origin. Before initiation of ciliogenesis, descendants of mesomeres and macromeres completed 9 and 10 rounds of cell division. Descendants of larger micromeres and the majority of cells derived from smaller micromeres did not acquired cilia even when the embryo began to rotate within the fertilization membrane. At this stage, the former had completed the 6th division and the latter the 8th division. Cell counts of blastomeres per embryo at the blastula stage also supported this observation.