Gene regulation of adult skeletogenesis in starfish and modifications during gene network co-option

The larval skeleton of the echinoderm is believed to have been acquired through co-option of a pre-existing gene regulatory network (GRN); that is, the mechanism for adult skeleton formation in the echinoderm was deployed in early embryogenesis during echinoderm diversification. To explore the evolutionary changes that occurred during co-option, we examined the mechanism for adult skeletogenesis using the starfish Patiria pectinifera. Expression patterns of skeletogenesis-related genes (vegf, vegfr, ets1/2, erg, alx1, ca1, and clect) suggest that adult skeletogenic cells develop from the posterior coelom after the start of feeding. Treatment with inhibitors and gene knockout using transcription activator-like effector nucleases (TALENs) suggest that the feeding-nutrient sensing pathway activates Vegf signaling via target of rapamycin (TOR) activity, leading to the activation of skeletogenic regulatory genes in starfish. In the larval skeletogenesis of sea urchins, the homeobox gene pmar1 activates skeletogenic regulatory genes, but in starfish, localized expression of the pmar1-related genes phbA and phbB was not detected during the adult skeleton formation stage. Based on these data, we provide a model for the adult skeletogenic GRN in the echinoderm and propose that the upstream regulatory system changed from the feeding-TOR-Vegf pathway to a homeobox gene-system during co-option of the skeletogenic GRN.

Patiriisocius marinistellae gen. nov., sp. nov., isolated from the starfish Patiria pectinifera, and reclassification of Ulvibacter marinus as a member of the genus Patiriisocius comb. nov.

A marine strain, designated KK4T, was isolated from the surface of a starfish, Patiria pectinifera, which was collected from seawater off the coast of Hokkaido, Japan. Strain KK4T is a Gram-stain-negative, non-spore-forming, rod-shaped, aerobic bacterium that forms yellow-pigmented colonies. A phylogenetic relationship analysis, based on 16S rRNA gene sequences, revealed that strain KK4T was closely related to Ulvibacter marinus IMCC12008T, Ulvibacter antarcticus IMCC3101T and Ulvibacter litoralis KMM 3912T, with similarities of 96.9, 95.8 and 95.6 %, respectively, but low sequence similarities (<94 %) among other genera in the family Flavobacteriaceae . Genomic similarities between strain KK4T and the three Ulvibacter type strains based on average nucleotide identity and digital DNA–DNA hybridization values were lower than the species delineation thresholds. Moreover, phylogenetic tree based on genome sequences showed that strain KK4T was clustered with U. marinus IMCC12008T and formed a branch independent from the cluster including type species of the genera Ulvibacter , Marixanthomonas , Marinirhabdus , Aureitalea and Aequorivita . Amino acid identity values between strain KK4T/ U. marinus IMCC12008T and the neighbour type species/strains were 61.9–68.2% and 61.5–67.4 %, which were lower than the genus delineation threshold, implying the novel genus status of strain KK4T. Strain KK4T growth occurred at pH 6.0–9.0, 4–30 °C and in NaCl concentrations of 0.5–5.0 %, and optimally at pH 7.0, 25 °C and 3.0 %, respectively. Unlike Ulvibacter strains, strain KK4T could assimilate glucose, mannose, galactose and acetate. The major quinone and fatty acids were menaquinone-6 and iso-C15 : 0 (27.5 %), iso-C15 : 1 G (22.5 %) and iso-C17 : 0 3-OH (12.8 %), respectively. Based on genetic, phylogenetic and phenotypic properties, strain KK4T represents a novel species of the genus Patiriisocius, for which the name Patiriisocius marinistellae gen. nov., sp. nov. is proposed. The type strain is KK4T (=JCM 33344T=KCTC 72225T). In addition, based on the current data, Ulvibacter marinus should be reclassified as Patiriisocius marinus comb. nov.

Arm swapping autograft shows functional equivalency of five arms in sea stars

Extant echinoderms show five-part radial symmetry in typical shape. However, we can find some asymmetry in their details, represented by the madreporite position not at the center, different skeletal arrangement in two of the five rays of sea urchins, and a circular cavity formed by two-end closure. We suspect the existence of any difference in hidden information between the five. In our hypothesis, deep equivalency makes no issue in function even after exchanging the position of rays; otherwise, this autograft causes some trouble in behavior or tissue formation. For this attempt, we firstly developed a method to transplant an arm tip to the counterpart of another arm in the sea star Patiria pectinifera. As a result, seven arms were completely implanted—four into the original positions for a control and three into different positions—with underwater surgery where we sutured with nylon thread and physically prevented nearby tube feet extending. Based on our external and internal observation, each grafted arm (i) gradually recovered movement coordination with the proximal body, (ii) regenerated its lost half as in usual distal regeneration, and (iii) formed no irregular intercalation filling any positional gap at the suture, no matter whether two cut arms were swapped. We here suggest a deep symmetry among the five rays of sea stars not only in morphology but also in physiology, representing an evolutionary strategy that has given equal priority to all the radial directions. Moreover, our methodological notes for grafting a mass of body in sea stars would help echinoderm research involving positional information as well as immunology.

Approach for numerically describing and classifying benthic animals’ polymorphic cells morphology

Describing cell morphology is a tricky task, prone to misinterpretation due to subjective nature of the human observer and his vocabulary limitations. Consequently, these limitations actuate prevalence of non-formalized, statistically unverifiable language use. This determines the reason for overlooking cell shape as a viable parameter for describing cell's functional state intricacies. In this study we demonstrate the use of mathematical parameters set for describing two-dimensional fractals, such as: convex hull, density, roundness and asymmetry, for comparative in vitro morphological analysis of sprawled starfishes' Aphelasterias japonica and Patiria pectinifera (Echinodermata: Asteroidea) coelomocytes, and bivalve's Callista brevisiphonata (Mollusca: Bivalvia) hemocytes. We found that these parameters allow us to describe visually distinguishable but verbally indescribable "chaotic" sprawled cell shapes. Furthermore, resulting numerical cell descriptions differs significantly, enabling for their species-specific grouping and classification. We argue that presented morphometric methodology can be used for describing and classifying cells of any arbitrary morphology, as well as compiling "cell shape - cell functional state" match library for later use in in vitro analysis, potentially for cells of any animal.

Approach for numerically describing and classifying benthic animals’ polymorphic cells morphology

Describing cell morphology is a tricky task, prone to misinterpretation due to subjective nature of the human observer and his vocabulary limitations. Consequently, these limitations actuate prevalence of non-formalized, statistically unverifiable language use. This determines the reason for overlooking cell shape as a viable parameter for describing cell's functional state intricacies. In this study we demonstrate the use of mathematical parameters set for describing two-dimensional fractals, such as: convex hull, density, roundness and asymmetry, for comparative in vitro morphological analysis of sprawled starfishes' Aphelasterias japonica and Patiria pectinifera (Echinodermata: Asteroidea) coelomocytes, and bivalve's Callista brevisiphonata (Mollusca: Bivalvia) hemocytes. We found that these parameters allow us to describe visually distinguishable but verbally indescribable "chaotic" sprawled cell shapes. Furthermore, resulting numerical cell descriptions differs significantly, enabling for their species-specific grouping and classification. We argue that presented morphometric methodology can be used for describing and classifying cells of any arbitrary morphology, as well as compiling "cell shape - cell functional state" match library for later use in in vitro analysis, potentially for cells of any animal.

Approach for numerically describing and classifying benthic animals’ polymorphic cells morphology

Describing cell morphology is a tricky task, prone to misinterpretation due to subjective nature of the human observer and his vocabulary limitations. Consequently, these limitations actuate prevalence of non-formalized, statistically unverifiable language use. This determines the reason for overlooking cell shape as a viable parameter for describing cell's functional state intricacies. In this study we demonstrate the use of mathematical parameters set for describing two-dimensional fractals, such as: convex hull, density, roundness and asymmetry, for comparative in vitro morphological analysis of sprawled starfishes' Aphelasterias japonica and Patiria pectinifera (Echinodermata: Asteroidea) coelomocytes, and bivalve's Callista brevisiphonata (Mollusca: Bivalvia) hemocytes. We found that these parameters allow us to describe visually distinguishable but verbally indescribable "chaotic" sprawled cell shapes. Furthermore, resulting numerical cell descriptions differs significantly, enabling for their species-specific grouping and classification. We argue that presented morphometric methodology can be used for describing and classifying cells of any arbitrary morphology, as well as compiling "cell shape - cell functional state" match library for later use in in vitro analysis, potentially for cells of any animal.