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Sea urchins and their relatives are grouped together taxonomically in the class Echinoidea (phylum Echinodermata). Echinoids exhibit remarkable variation in their pentaradially symmetric body shape phenotypes, from spheroid tests (skeletons) in sea urchins to discoid tests in sand dollars. Researchers have speculated on the morphological evolutionary transitions among these phenotypes without reaching consensus. We designed and performed an experiment in which sea urchins grew under a geometric constraint manifested through restricted vertical spatial dimension physically limiting growth in height. Individuals in this treatment group became flatter relative to individuals in a control group after 8 weeks. These findings may be considered as instantiating phenotypic accommodation, an underappreciated phenomenon that may constitute the first step in novel phenotype evolution. We present preliminary speculations relating phenotypically accommodated changes in shape and morphological evolutionary relationships among echinoids. By demonstrating a plausible initiating mechanism in a morphological transition, we hope to contribute to theoretical discussions about phenotypic evolution, emphasizing the role that physical factors play in changing complex biological systems.

Phenotypic plasticity is widely regarded as important for enabling species resilience to environmental change and for species evolution. However, insight into the complex mechanisms by which phenotypic plasticity evolves in nature has been limited by our ability to reconstruct evolutionary histories of plasticity. By using part of the molecular mechanism, we were able to trace the evolution of pre-feeding phenotypic plasticity across the class Echinoidea and identify the origin of plasticity at the base of the regular urchins. The neurosensory foundation for plasticity was ancestral within the echinoids. However, coincident development of the plastic trait and the neurosensory system was not achieved until the regular urchins, likely due to pleiotropic effects and linkages between the two colocalized systems. Plasticity continues to evolve within the urchins with numerous instances of losses associated with loss of sensory capabilities and in one case loss of neurons, consistent with a cost associated with maintaining these capabilities. Thus, evidence was found for the neurosensory system providing opportunities and constraints to the evolution of phenotypic plasticity.

Coelomic fluid aspiration has been utilized in echinoderms in research and clinical settings. Detailed procedural descriptions for coelomic fluid sampling in sea urchins (class Echinoidea) are lacking, and samples are prone to contamination. The objectives of this study were to (1) standardize a technique for coelomic fluid collection in long-spined sea urchin Diadema antillarum that optimizes the diagnostic quality of the sample utilizing diagnostic imaging, (2) identify coelomic fluid bacterial isolates (using Biolog GEN III MicroLog and 16s rDNA sequencing), and (3) compare positive cultures to animal weight, holding time prior to sampling, water temperature, and gross fluid appearance. Seventy Diadema antillarum from the Florida Keys collected in two groups (March and September 2015) were utilized. Positive cultures for bacterial contamination were identified in 5% and 44%, respectively, of animals in the sampling groups. Vibrio spp. was the predominant genus identified. Positive cultures were more frequent in the group with smaller-sized animals, increased holding times, and elevated water temperatures. Deviation from clear-pink gross coelomic fluid appearance did not reliably predict bacterial contamination. A standardized technique for coelomocentesis was defined. The use of the proposed coelomocentesis methodology may facilitate improved health evaluations of sea urchins and may be applicable to research, conservation efforts, and disease investigations.

The class Echinoidea contains among the best-known echinoderms. The group has left the most complete fossil record of this phylum, and contains about 1000 living species, of which 51 are recorded along the Brazilian coast. Although the first record of echinoids in Brazil was made 369 years ago, the knowledge of this fauna remains quite unsatisfactory from a taxonomic and ecological point of view, particularly in the north and northeastern regions of the country. This study provides the first annotated list of echinoids from northeastern Brazil. The studied material largely belongs to collections of the Federal University of Paraíba (CIPY), Federal University of Sergipe (LABIMAR-UFS), Federal University of Bahia (MZUFBA), University of São Paulo (MZUSP), and National Museum of the Federal University of Rio de Janeiro (MNRJ). Thirty-two species from 29 genera, 18 families, and 10 orders were identified. Descriptions of species are provided. Highest diversities of Echinoidea were encountered for the states of Bahia (19 spp.), Alagoas (11 spp.), Paraíba (10 spp.), Ceará (7 spp.), Rio Grande do Norte (7 spp.), and Pernambuco (6 spp.). On the basis of the data analysed, Maranhão (2 spp.), Piauí (2 spp.), and Sergipe (3 spp.) have the lowest diversity. Sandy substrates and depths below 10 m were the least sampled areas over the continental shelf. Although the studied species are common, some taxonomic problems were encountered and discussed. We also provide ecological information and comments on status of the species from the studied region. As a result of this inventory, we were able to provide the first assessment of the echinoid fauna of northeastern Brazil.

The external and internal morphologies of cidaroid and camarodont sea urchin primary spines are investigated giving an overview of the internal microstructure and structural properties. The investigated species comprise the cidaroids Eucidaris metularia, Phyllacanthus imperialis, Plococidaris verticillata and Prionocidaris baculosa as well as the camarodont Heterocentrotus mammillatus (Echinodermata: Class Echinoidea), and morphological descriptions are based on scanning electron microscopy and micro-computed tomography. Stereom types and densities are differentiated using pore and trabecular diameter measurements. Structural analysis was performed using three point bending tests resulting in the calculation of force, deflection and stress, strain relationships. All studied species possess primary spines with a medulla consisting of laminar stereom regardless of the age and position of the spine on the tests. Differences in stereom morphology occur in the radiating layer and the surface of the spines. Material densities and stereom types differ with respect to growth lines when present and the radiating layer. The primary spines also show large differences in their outer morphologies ranging from smooth, striated to tuberculate. H. mammillatus spines are shown to bear more stress resistance than those of the cidaroids. Differences in spine morphologies and reaction to stress are interpreted with respect to functional morphological response, to ambient environmental parameters and their strategies between and within evolutionary stages.

This study presents the first extensive investigation of echinoderm distribution in the area of mobile bottoms in the open part of the northern and middle Adriatic Sea. Five hundred and eighteen bottom trawl hauls were performed at 56 predetermined permanent stations along ten transects over different sediment types, at depths of 10 to 430 m. A total of 34 species of Echinodermata were identified (9 from the class Holothuroidea, 12 from the class Asteroidea, 4 from the class Ophiuroidea and 9 from the class Echinoidea). The list of the species, together with data on depth and sediment distribution, and the stations where individual species were found, are presented.

Bindin plays a central role in sperm-egg attach- ment and fusion in sea urchins (echinoids). Previous studies determined the DNA sequence of bindin in two orders of the class Echinoidea, representing 10% of all echinoid species. We report sequences of mature bindin from five additional genera, representing four new orders, including the distantly related sand dollars, heart urchins, and pencil urchins. The six orders in which bindin is now known include 70% of all echinoids, and indicate that bindin was present in the com- mon ancestor of all extant sea urchins more than 250 million years ago. Over this span of evolutionary time there has been (1) remarkable conservation in the core region of bindin, particularly in a stretch of 29 amino acids that has not changed at all; (2) conservation of a motif of basic amino acids at the cleavage site between preprobindin and mature bindin; (3) more than a twofold change in length of mature bindin; and (4) emergence of high variation in the sequences outside the core, including the insertion of gly- cine-rich repeats in the bindins of some orders, but not others.

This paper presents a checklist of echinoderm species in the Adriatic Sea. The checklist is based on the review of the available literature data, with temporal coverage from the end of the 18th century to the present day, including the most recent investigations of benthic communities. A total of 108 species have been recorded: 2 species from class Crinoidea, 23 species from class Asteroidea, 22 species from class Ophiuroidea, 22 species from class Echinoidea and 39 species from class Holothuroidea. Non-indigenous echinoderm species have not been observed.

The gut of echinoids is lined by an epithelium which includes some mucous cells ; the structure and function of echinoid guts in general has recently been reviewed by Anderson ( 1966) . The term mucous cell is restricted in the present paper to denote only those epithelial cells containing a conspicuous accumulation of mucus intracellularly. In addition, the lining epithelium of echinoid guts may include the following two kinds of cells associated with mucus, yet not considered here to be mucous cells : ( 1) mucus-containing coelomocytes wandering in the gut wall and (2) epithelial cells lacking intracellular mucus, but having a thin glyco calyx of mucus associated with the distal cell membrane. Mucous cells in echinoid guts were first mentioned explicitly by Koehler in 1883; unfortunately, his report is hard to evaluate, because it came long before the advent of histo chemistry. Since the development of histochemical methods for mucopolysac charides, gut mucous cells have been studied in some detail for the following echinoid species: Echinus esculentus (Stott, 1955; Buchanan, 1969), Strongylo centrotus intermedius (Fuji, 1961), Strongylocentrotus purpuratus (Holland and Nimitz, 1964), and Psammechinus miliaris (Buchanan, 1969). Less detailed studies have been made of the gut mucous cells in Diadema antillarism (Lewis, 1964) and Dendraster excentricus (Reisman, 1965). The species mentioned above represent but a few of the extant orders and families of echinoids. The lack of information about mucous cells in the class Echinoidea as a whole prompted the present investigation of the patterns of dis tribution and the histochemical properties of mucous cells in the guts of thirty seven species of echinoids, both regular and irregular. The same set of histo chemical methods was applied to each species in order to facilitate comparisons. The results have been interpreted phylogenetically in the context of a widely accepted scheme of macroevolution in the class Echinoidea (Durham and Melville, 1957). The echinoid taxonomy of Mortensen (1928, 1935, 1940, 1943a, 1943b, 1948, 1950, 1951) has been followed here because it is more suitable at the ordinal level than the newer echinoid taxonomy (summarized by McCormick and Moore, 1966) for condensing and summarizing the results of the present investi gation. During the course of the present study, some new facts about the gross anatomy of the echinoid siphon unexpectedly came to light and have necessarily been reported here. To date, the terminology for echinoid gut regions has not been standardized. Therefore, the terms used in this paper must be defined at the outset. In the

The Bulletin of Zoological Nomenclature, Volume 6, Issue 1, pp. 3-6