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Heart urchins (Echinoidea: Spatangoida) collectively represent a highly diverse group of echinoids with abundant global fossil and extant records. Despite their wide distribution, the preservation challenges associated with their delicate and thin tests have led to limited comprehensive studies of this fossil group in Taiwan. Here, we report a new spatangoid echinoid assemblage from the Early Pleistocene part of the Gutingkeng Formation. Despite the inherent fragility and pronounced deformations in the studied specimens, the preserved key diagnostic characteristics (pore pairs in ambulacrum III and oral plating) indicate most of the fossil echinoids belong to genera Schizaster and Brissopsis. Moreover, based on detailed taphonomic and functional morphological examination, the paleoenvironment of the assemblage is interpreted as a low-energy, fine-grained soft substrate in a deeper shallow-water setting. Furthermore, this assemblage shares a high similarity with Assemblage 3 at the S'Archittu-Cajaragas section in the Miocene of Sardinia, supporting the notion that echinoids are excellent paleoenvironmental indicators, as similar echinoid faunas can be found across continents when environmental conditions are similar. On the other hand, the temporal and geographical distribution of Schizaster -rich echinoid assemblages in Taiwan may be correlated with the Cenozoic orogeny history of Taiwan. [ABSTRACT FROM AUTHOR]

The sea urchin Pseudechinus magellancus exhibits a covering behaviour through which it captures different items from the environment and arranges them on its aboral surface with the assistance of podia. The items mainly used include detached algae and inorganic items available in the substrate. Spatial (between sites) and vertical (along a coastal depth gradient from intertidal tidepools to upper circalittoral zones) variability was found in the composition of covering items, indicating that coverage is strongly influenced by the availability of the utilised items. Inorganic biogenic items (eg shell remnants) were prevalent in the lower intertidal, while detached algae predominate in subtidal environments. A positive selection of larger items from those available in the environment was found at least in the intertidal tidepools. The species exhibited an equal degree of coverage between juveniles and adults, and also a higher proportion of individuals with high coverage in the intertidal zone compared to the subtidal zone. The degree of coverage between sites with dissimilar sediment input was similar. The covering behaviour in P. magellanicus may not be a response to a single factor but rather an advantageous trait with multiple functions that could have been selected simultaneously. [ABSTRACT FROM AUTHOR]

ABSTRACT Drilling predation on echinoids (sea urchins) has been known to occur in marine ecosystems since the Jurassic Period; however, it has rarely been studied in existing species. Tests of the irregular sea urchin Brissus unicolor (Leske, 1778), which frequently occurs in shallow substrates of the Canary Islands, mostly show very evident perforations through their skeletons. The aim of this study was to describe the characteristics of these perforations in order to determine their possible origins as well as document their size, site selectivity, and frequency of occurrence among different sample sites. Of the 104 tests of B. unicolor that were collected from 15 locations off the island of Tenerife (Canary Islands, Spain), 94% showed a least one perforation. These boreholes exhibit a circular morphology, penetrating the sea urchin tests perpendicularly and entirely. Notably, they display a unique acid signature, diverging from those documented in the fossil record and other relevant studies. Our analysis showed size and site selectivity by the predator as the perforations were mainly located on the oral side of the test. The perforations are attributed to drilling predation. The characteristics of these boreholes on B. unicolor match published records of predation marks suggesting that they are produced by the predatory gastropod family Cassidae, with Semicassis undulata (Gmelin, 1791) considered to be the most probable predator. [ABSTRACT FROM AUTHOR]

Hitherto unreported whale fall fauna has been found from the Lower Miocene of Khari Nadi Formation of Kutch, India.This vertebrate-invertebrate assemblage comprises jumbled up bone fragments of different parts of the whale along with molluscs and echinoids. Some representatives in this assemblage are characteristic whale fall fauna and some are characteristic shallow marine fauna. The molluscs belong to the families Buccinidae, Provannidae, Naticidae, Turritellidae, Borsoniidae, Volutidae, Haminoeidae, Cypraeidae, Strombidae, Rostelleriidae, Cassidae, Osteridae, Veneridae, Astartidae and the echinoids to family Spatangidae and Schizasteridae. The present study reveals that the deposition of this entire assemblage was in a shallow marine environment and also sheds some light on the molluscan association related to a whale fall from the western Indian sea waters in the Lower Miocene. [ABSTRACT FROM AUTHOR]

Gregory's diverticulum, a digestive tract structure unique to a derived group of sand dollars (Echinoidea: Scutelliformes), is filled with sand grains obtained from the substrate the animals inhabit. The simple methods of shining a bright light through a specimen or testing response to a magnet can reveal the presence of a mineral-filled diverticulum. Heavy minerals with a specific gravity of >2.9 g/cm3 are selectively concentrated inside the organ, usually at concentrations one order of magnitude, or more, greater than found in the substrate. Analyses of diverticulum content for thirteen species from nine genera, using optical mineralogy, powder X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy, as well as micro-computed tomography shows the preference for selection of five major heavy minerals: magnetite (Fe3O4), hematite (Fe2O3), ilmenite (FeTiO3), rutile (TiO2), and zircon (ZrSiO4). Minor amounts of heavy or marginally heavy amphibole, pyroxene and garnet mineral grains may also be incorporated. In general, the animals exhibit a preference for mineral grains with a specific gravity of >4.0 g/ cm3, although the choice is opportunistic and the actual mix of mineral species depends on the mineral composition of the substrate. The animals also select for grain size, with mineral grains generally in the range of 50 to 150 mm, and do not appear to alter this preference during ontogeny. A comparison of analytical methods demonstrates that X-ray attenuation measured using micro-computed tomography is a reliable non-destructive method for heavy mineral quantification when supported by associated analyses of mineral grains extracted destructively from specimens or from substrate collected together with the specimens. Commonalities in the electro-chemical surface properties of the ingested minerals suggest that such characteristics play an important role in the selection process. [ABSTRACT FROM AUTHOR]

Gregory’s diverticulum, a digestive tract structure unique to a derived group of sand dollars (Echinoidea: Scutelliformes), is filled with sand grains obtained from the substrate the animals inhabit. The simple methods of shining a bright light through a specimen or testing response to a magnet can reveal the presence of a mineral-filled diverticulum. Heavy minerals with a specific gravity of >2.9 g/cm3 are selectively concentrated inside the organ, usually at concentrations one order of magnitude, or more, greater than found in the substrate. Analyses of diverticulum content for thirteen species from nine genera, using optical mineralogy, powder X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy, as well as micro-computed tomography shows the preference for selection of five major heavy minerals: magnetite (Fe3O4), hematite (Fe2O3), ilmenite (FeTiO3), rutile (TiO2), and zircon (ZrSiO4). Minor amounts of heavy or marginally heavy amphibole, pyroxene and garnet mineral grains may also be incorporated. In general, the animals exhibit a preference for mineral grains with a specific gravity of >4.0 g/cm3, although the choice is opportunistic and the actual mix of mineral species depends on the mineral composition of the substrate. The animals also select for grain size, with mineral grains generally in the range of 50 to 150 μm, and do not appear to alter this preference during ontogeny. A comparison of analytical methods demonstrates that X-ray attenuation measured using micro-computed tomography is a reliable non-destructive method for heavy mineral quantification when supported by associated analyses of mineral grains extracted destructively from specimens or from substrate collected together with the specimens. Commonalities in the electro-chemical surface properties of the ingested minerals suggest that such characteristics play an important role in the selection process.

Ocean warming and acidification driven by anthropogenic CO 2 emissions may impact the mineral composition of marine calcifiers. Species with high skeletal Mg content could be more susceptible in polar regions due to the increased solubility of CO 2 at lower temperatures. We aimed to assess the environmental influence on skeletal Mg content of Antarctic echinoderms belonging to Asteroidea, Ophiuroidea, Echinoidea and Holothuroidea classes, along a latitudinal gradient from the South Shetland Islands to Rothera (Adelaide Island). We found that all skeletal structures, except for echinoid spines, exhibited high Mg content, with asteroids showing the highest levels. Our results suggest that asteroids and holothuroids exert a higher biological capacity to regulate Mg incorporation into their skeletons. In contrast, the variability observed in the skeletal Mg content of ophiuroids and echinoids appears to be more influenced by local environmental conditions. Species-specific differences in how environmental factors affect the skeletal Mg content can thus be expected as a response to global climate change. • Skeletal structures presented high Mg content, except in echinoid spines. • Asteroids had the highest Mg content, followed by ophiuroids, holothuroids, and echinoids. • No local variability in skeletal Mg content was observed in asteroids and holothuroids. • Environmental parameters may have influenced the skeletal Mg in ophiuroids and echinoids. [ABSTRACT FROM AUTHOR]

Sea urchins have a wide variety of symbionts on their body surfaces and inside their bodies. Copepods of the genus Clavisodalis (Taeniacanthidae) collected from the esophagus of sea urchins of the genera Diadema and Echinothrix in southern Japan were identified based on their morphological characteristics, and molecular analysis was conducted to determine whether genetic variation occurs in copepods from different localities and hosts. Morphological observations identified individuals from southern Japan as Clavisodalis sentifer Dojiri and Humes, 1982, making this the first record of this species in the northern hemisphere and the first record of its genus in Japan. Morphological and molecular analysis suggested that the copepod specimens collected from multiple hosts across two genera would be the same species. Considering the typically observed high level of host specificity among taeniacanthid copepods, the utilization of hosts from two genera by C. sentifer is noteworthy.