Effects of body size and shape on locomotion in the bat star (Patiria miniata)

Among taxa ranging from cnidarians to vertebrates, absolute speed of locomotion generally increases with increasing body size. Despite the unique mode of locomotion in echinoderms, crawling speed also appears to increase with increasing body size, at least in some species of asteroids and echinoids. We used an escape-response assay to assess how maximum crawling speed varied with body size in the bat star Patiria miniata. We also tested the effect of arm number on maximum crawling speed by comparing speeds of five- and six-armed individuals. Contrary to prior reports for a single sea urchin and sea star species, both absolute crawling speed and crawling speed relative to body size actually declined with increasing body mass, increasing arm length, and increasing oral surface area, in both five- and six-armed individuals. Arm number did not appear to have a significant effect on crawling speed. The reasons for this negative relationship between crawling speed and body size in P. miniata remain unclear, but we suspect that the disproportionate increase in body mass relative to total tube-foot cross-sectional area may make locomotion proportionally more difficult in larger-bodied sea stars.     

Electron microscopy of extracellular materials during the development of a sea star,Patiria miniata (Echinodermata: Asteroidea)

The fine structure of conspicuous extracellular materials during the life history of a sea star (Patiria miniata) is described. The outer surface of the developing sea star is covered by two morphologically different cuticles that appear sequentially during ontogeny. The primary cuticle, which is about 120 nm thick and two-layered, is present from mid-blastula through the end of the larval stage. The secondary cuticle, which is about 1 micron thick and three-layered, first appears on the epidermis of the rudiment region of the larva and, after metamorphosis, covers the entire epidermis of the juvenile and adult stages. During ontogeny, there are only two conspicuous gut cuticles: the first lines the newly invaginated archenteron at the start of the gastrula stage, and the second lines the esophagus during the larval stage. A blastocoelic basal lamina first appears at mid-blastula and persists as subectodermal and subendodermal basal laminae. Ruthenium red-positive granules are detectable between the lateral surfaces of adjacent ectodermal cells during part of the gastrula stage; this transient intercellular material may possibly aid in lateral adhesion between cells.     

Predation by Patiria miniata (Asteroidea) on bryozoans: Prey diversity may depend on the mechanism of succession

Summary In environments where frequent disturbances interrupt the successional process there will usually be many patches of habitat at intermediate stages of succession. It is then relevant to consider the factors which control local diversity during succession. In offshore kelp forests across the whole Southern Californian Bight settlement panels were rapidly colonised by two species of cyclostome bryozoans (Tubulipora tuba and T. pacifica); but cheilostome bryozoans eventually became dominant during succession because they were able to grow over Tubulipora spp. When abundant, Tubulipora spp. were apparently able to reduce the number of colonies, and hence the number of species, of cheilostome bryozoans settling on the panels. Thus the rapid colonisers may delay the process of succession and reduce the diversity of bryozoans during succession. In field and laboratory experiments we found that the asteroid Patiria miniata preys on Tubulipora spp. but not on cheilostome bryozoans. The predator speeds up the successional process and increases bryozoan diversity by reducing the cover of Tubulipora spp. Other ways in which predators may influence diversity during succession are discussed. The effect of predation may depend on the abundance of the prey and the mechanism of succession.     

Isolation and sequence analysis of sea urchin (Lytechinus pictus) histone H4 messenger RNA

Histone messenger RNAs isolated from early blastula stage Lytechinus pictus sea urchin embryos have been separated into discrete RNA bands on polyacrylamide gels. The most rapidly migrating of these molecules, the putative histone H4 mRNA, has been digested with T₁ ribonuclease to generate oligonucleotides for nucleotide sequence analysis. Many of these sequences are colinear with the highly conserved amino acid sequence of histone H4 protein as determined for both cows and peas.Histone H4 messenger RNA hybridizes in conditions of DNA excess to sea urchin DNA which is repeated approximately 470-fold. Despite this level of repetition the nucleotide sequence of the H4 messenger RNA reflects little evolutionary divergence within the H4 genes of L. pictus as judged by the stoichiometric yield of T₁ oligonucleotides and the hybridization and thermal stability of histone H4 mRNA-DNA hybrids.     

Changes in the Distribution of Calcium-Sequestering Membranes during the First Cell Cycle of the Sea Urchin, Lytechinus variegatus

Chlortetracycline (CTC) has been used to study sequential changes in the distribution of calcium-sequestering membranes during the first cell cycle of fertilized sea urchin eggs CTC staining patterns first appear as a diffuse ring around the centered zygote nucleus at the time of syngamy. As development proceeds, the ring becomes brighter and then elongates concurrently with the formation of the streak apparatus. Fluorescence subsequently accumulates in the centrospheres of the developing mitotic apparatus and is present in mitotic asters throughout mitosis. When the mitotic apparatus disappears, the fluorescence associated with each aster condenses into a bright ring surrounding each daughter nucleus. Ultrastructural studies show that CTC-fluorescent areas are rich in membranes while experiments with rhodamine 123, a mitochondrion-specific laser dye, indicate that mitochondria are excluded from areas in which membranes accumulate. Microtubule inhibitors prevent the initial accumulation of fluorescence around the zygote nucleus and arrest the development of existing fluorescence patterns when applied at later stages. In contrast, changes in fluorescence patterns are unaffected by the microfilament inhibitor cytochalasin D. These observations show that calcium-sequestering membranes are associated consecutively with the sperm aster, streak, and mitotic apparatus and that the continual reorganization of these membranes during the first cell cycle depends on the assembly and disassembly of microtubules.     

The Vertical Distribution of Larvae of the Sea Urchin Strongylocentrotus intermedius in Superficial Desalination Conditions

The vertical distribution of larvae of the sea urchin Strongylocentrotus intermedius in conditions of superficial desalination was studied under laboratory conditions. In the earlier stages of development, the larvae accumulated in the water column zone with a salinity below the optimal level. The long-term observations of the larval accumulations revealed the deceleration of, and abnormalities in, the development and death of the larvae. The larvae at the pre-settling stages changed their behavior: when they reached layers of a salinity unfavorable for their survival or development, the larvae did not enter them and instead moved down instead. Obviously, S. intermedius larvae are only capable of actively choosing their position within the water column with the salinity gradient at the later stages of development.     

Sensitivity of Embryos and Larvae of the Sea Urchin Strongylocentrotus intermedius to Effects of Copper Ions

The effect of copper ions in seawater (0.02 mg/l) on the early stages of development of the sea urchin Strongylocentrotus intermedius was studied. Copper exposure from fertilization or the prism stage retarded development and growth and led to abnormalities in the morphology of the embryos and larvae. However, if development to the pluteus stage proceeded in clean seawater, an increased copper concentration did not inhibit the growth of larvae. If sea urchin embryos at fertilization and the prism stage were maintained for 1–2 days in seawater containing 0.02 mg Cu/l and then transferred to clean seawater, the adverse consequences of this exposure remained present after 48 h.     

The Reaction of the Starfish Asterias amurensisand Patiria pectinifera (Asteroidea) from Vostok Bay (Sea of Japan) to a Salinity Decrease

The reactions of the starfish Asterias amurensis and Patiria pectinifera that live in Vostok Bay at the salinity of 32–33 to a salinity decrease were studied under laboratory conditions. The lower limits of the desalination tolerance range of A. amurensis and P. pectinifera were, respectively, 24 and 20. A. amurensis proved to be less resistant to desalination. Under experimental conditions, all specimens of this species survived the salinity of 22, while those of P. pectinifera tolerated 18. At the same time, A. amurensis responded more actively than P. pectinifera to unfavorable changes in the environment. Turned to their dorsal side and exposed to a salinity of 16 to 32, the former reverted to the normal position within a shorter time than the latter. Being a more euryhaline species, P. pectinifera endured a salinity decrease to 6 or 8 over, respectively, 21 or 28 h. However, only 30–40% of all specimens could recover locomotory activity 12 or 8.5 h after being placed into water of normal salinity.     

Sequence analysis and evolution of sea urchin (Lytechinus pictus and Strongylocentrotus purpuratus) histone H4 messenger RNAs

The putative histone H4 (F2a₁) mRNA has been isolated from early blastula Strongylocentrotus purpuratus sea urchin embryos. Nucleotide sequences of oligonucleotides obtained by digestion of this RNA with T₁ ribonuclease have been obtained and many are found to be colinear with the amino acid sequence of histone H4 protein. The sequences obtained from the H4 mRNAs of S. pnrpuratus have been compared with those obtained from Lytechinus pictus (Grunstein & Schedl, 1976). The two mRNAs for this highly conserved protein have undergone considerable divergence of the sort that would be predicted from the degeneracy of the genetic code. 11.5% of the bases have undergone substitution at a rate calculated to be 3 × 10^?9 base changes · codon^?1 · year^?1.     

Purification of Acetylcholinesterase from Sea Urchin (Hemicentrotus pulcherrimus) Embryos by Affinity Chromatography

Only one form of acetylcholinesterase (AchE) was detected in Hemicentrotus pulcherrimus embryos. In H. pulcherrimus embryos as well as in the other sea urchin embryos, AchE activity begins to increase rapidly after gastrula stage.
Purification of AchE from plutei has been carried out by the procedure including affinity chromatography. Purified AchE had the activity 14,600 times higher than that of homogenate, and the final yield of AchE was 8%. The enzyme seems to be electrophoretically homogeneous, and has a molecular weight of 3 × 10⁵ as determined by Sepharose CL–6B column chromatography.     

Anisakis pegreffii Larvae in Sea Eels (Astroconger myriaster) from the South Sea,Republic of Korea

Anisakis simplex sensu stricto (s.s.), Anisakis pegreffii, Anisakis berlandi (=A. simplex sp. C), and Anisakis typica are the 4 major species of Anisakis type I larvae. In the Republic of Korea (Korea), A. pegreffii, A. berlandi, and A. typica larvae in fish hosts has seldom been documented. In this study, molecular analysis was performed on Anisakis larvae from the sea eels (Astroconger myriaster), the major source of human anisakiasis in Korea, collected from Tongyeong City, a southern coastal area of Korea. All 20 sea eels examined were infected with Anisakis type I larvae (160 larvae; 8 per fish). Their species were analyzed using PCR-RFLP patterns and nucleotide sequences of internal transcribed spacers (ITS1, 5.8 subunit gene, and ITS2) and mitochondrial cytochrome c oxidase 2 (cox2). Most (86.8%; 112/129) of the Anisakis type I larvae were A. pegreffii, and 7.8% (10/129) were A. typica. The remaining 5.4% (7/129) was not identified. Thus, A. pegreffii is the major species of anisakid larvae in sea eels of the southern coast of Korea.     

Larvae and postlarvae production of the green-white sea urchin Lytechinus variegatus (Echinodermata: Echinoidea) in culture conditions

We evaluated the biological feasibility of massive larvae and postlarvae production of the Caribbean green-white urchin Lytechinus variegatus. Experiments were designed to choose the initial larval density and microalgae diets under culture, to study metamorphosis, postlarval and juvenile growth. Massive production of competent larvae 650 microm long at 12-13 days is possible using larval densities of 0.25 to 1 larva/ml. The microalgae Rhodomonas sp. was suitable for the optimization of larval growth and survival. Metamorphosis of 100% of the larvae can be induced with films of bentic diatoms (Navicula sp. and Amphora sp.), after 96 h; however, diatoms are not adequate for postlarval development and a food supply of Ulva lactuta is necessary for proper growth. For juveniles, a diet of macroalgae (U. lactuta) and/or commercial marine shrimp culture pellet food is enough for growth, but the best results were obtained with shrimp or U. lactuta used alone (85-86%, against 46% with the mixed diet). We recommend future experiments on nutritional requirements to optimize growth of these and subsequent stages.     

The Structure and Development of the Apical Ganglion in the Sea Urchin Pluteus Larvae of Strongylocentrotus droebachiensis and Mespilia globulus

The structure of the apical ganglion is described using transmission electron microscopy and ultrastructural immunohistochemical localization with anti-serotonin, and the development of these nerve cells in animalized and vegetalized embryos, and embryos treated with Ca²⁺-deficient sea water are demonstrated with immunofluorescence microscopy. The axons within the neuropile contain clear and dense-core vesicles, but all the vesicles appear anti-serotonin immunoreactive. The principal type of neuron within the apical ganglions is anti-serotonin immunoreactive. In the animalized embryos, serotonergic neuroblasts and neurons appear in the second quarter of animal-vegetal axis. Serotonergic cells were not detected in vegetalized exogestrulae. Mespilia globulus embryos treated with Ca²⁺-deficient sea water ruptured to form a cellular sheet on the substratum. In ruptured embryos serotonergic neurons formed a ring around the area corresponding to the apical plate of normal embryos. These findings indicated that the serotonergic preoral nerve cells of echinopluteus derive from cells on the periphery of the apical plate.     

A Stereometric Analysis of Karyokinesis, Cytokinesis and Cell Arrangements during and following Fourth Cleavage Period in the Sea Urchin, Lytechinus variegatus

Fourth cleavage of the sea urchin embryo produces 16 blastomeres that are the starting point for analyses of cell lineages and bilateral symmetry. We used optical sectioning, scanning electron microscopy and analytical 3-D reconstructions to obtain stereo images of patterns of karyokinesis and cell arrangements between 4th and 6th cleavage. At 4th cleavage, 8 mesomeres result from a variant, oblique cleavage of the animal quartet with the mesomeres arranged in a staggered, offset pattern and not a planar ring. This oblique, non-radial cleavage pattern and polygonal packing of cells persists in the animal hemisphere throughout the cleavage period. Contrarily, at 4th cleavage, the 4 vegetal quartet nuclei migrate toward the vegetal pole during interphase; mitosis and cytokinesis are latitudinal and subequatorial. The 4 macromeres and 4 micromeres form before the animal quartet divides to produce a 12-cell stage. Subsequently, macromeres and their derivatives divide synchronously and radially through 8th cleavage according to the Sachs-Hertwig rule. At 5th cleavage, mesomeres and macromeres divide first; then the micromeres divide latitudinally and unequally to form the small and large micromeres. This temporal sequence produces 28-and 32-cell stages. At 6th cleavage, macromere and mesomere descendants divide synchronously before the 4 large micromeres divide parasynchronously to produce 56- and 60-cell stages.     

Nonallelic histone gene clusters of individual sea urchins (Lytechinus pictus): mapping of homologies in coding and spacer DNA

The linear arrangement and lengths of the spacers and coding regions in the two nonallelic histone gene variant clusters of L. pictus are remarkably homologous by R loop analysis and are similar in general topography to the histone gene repeat units of other sea urchins examined to date. No interventing sequences were detected. The coding regions of these two histone gene variants share considerable sequence homology; however, there are areas of nonhomology in every spacer region and the lengths of the nonhomologous spacers between the H2A and H1 genes are not the same for the two repeat unit classes (inter-gene heterogeneity). Combining length measurements obtained with both R loops and heteroduplexes suggests that the DNA sequences of the analogous leader regions for the two H1 mRNAs are nonhomologous. Similar observations were made for the H4 leader sequences, as well as the trailer region on H2B. S. purpuratus spacer DNA segments share little sequence homology with L. pictus; however, the analgous coding (and possibly flanking) regions have conserved their sequences. The various coding and spacer regions within a repeat unit do not share DNA sequences. Thus certain areas in the sea urchin histone gene repeat units have been highly conserved during evolution, while other areas have been allowed to undergo considerable sequence change not only between species but within a species.     

Ribosomal RNA Synthesis in Sea Urchin Embryos: Differential Rates of Accumulation in Chemically-induced Animalized and Vegetalized Larvae

Animalization was induced with evans blue and with Zn⁺⁺ in embryos of Arbacia punctulata and of Lytechinus variegatus , respectively. Li⁺ induced vegetalization in A. punctulata embryos. While animalization did not affect the rate of cleavage, vegetalized embryos exhibited a reduction in cell number at post-morula stages. Mid-gastrulae and corresponding experimental embryos each were labeled for 4 hr with uridine-[5-³H] and with L-[³H-methyl]-methionine. The rate of uptake of each exogenous RNA precursor was similar in control and in experimental embryos. Purified RNA preparations were fractionated by electrophoresis on 2.4% acrylamide+0.5 % agarose gels. Comparison of rates of incorporation of each RNA precursor into 26s and 18s RNAs indicated that on a per cell basis evans blue- and Zn⁺⁺-animalized embryos showed a reduction (0.53–0.56) and Li⁺-vegetalized embryos an enhancement (1.41—1.53) in the rate of accumulation of newly made 26s and 18s RNAs compared to controls (1.00). These results suggest that chemically-induced animalized and vegetalized embryos provide useful tools for studying possible differential gene expression in different embryonic germ layers of the developing sea urchin embryo.     

海胆Runx基因保守序列的克隆与初步分析

Runx(Runt box)是Runt结构域转录因子家族的成员之一。马粪海胆Runx基因第663位和728位碱基发生突变,分别为A→T和C→T。第一个突变为错义突变,使密码子编码的氨基酸由天冬氨酸变为酪氨酸,而第二个突变为同义突变,密码子编码的氨基酸未发生变化。海胆Runx基因保守序列的突变可能会导致其表达产物的变化,进而会影响海胆的生理机能。     

Localization and Substrate Selectivity of Sea Urchin Multidrug (MDR) Efflux Transporters

In this study, we cloned, expressed and functionally characterized Stronglycentrotus purpuratus (Sp) ATP-binding cassette (ABC) transporters. This screen identified three multidrug resistance (MDR) transporters with functional homology to the major types of MDR transporters found in humans. When overexpressed in embryos, the apical transporters Sp-ABCB1a, ABCB4a, and ABCG2a can account for as much as 87% of the observed efflux activity, providing a robust assay for their substrate selectivity. Using this assay, we found that sea urchin MDR transporters export canonical MDR susbtrates such as calcein-AM, bodipy-verapamil, bodipy-vinblastine, and mitoxantrone. In addition, we characterized the impact of nonconservative substitutions in the primary sequences of drug binding domains of sea urchin versus murine ABCB1 by mutation of Sp-ABCB1a and treatment of embryos with stereoisomeric cyclic peptide inhibitors (QZ59 compounds). The results indicated that two substitutions in transmembrane helix 6 reverse stereoselectivity of Sp-ABCB1a for QZ59 enantiomers compared with mouse ABCB1a. This suggests that subtle changes in the primary sequence of transporter drug binding domains could fine-tune substrate specificity through evolution.