Callianassid Shrimp Research Articles

Resurrection of the parasitic isopod genus Cryptione Hansen, 1897 (Epicaridea: Bopyridae) and description of a new species of parasitic isopod (Epicaridea: Bopyridae) from the deep-sea shrimp Notostomus gibbosus (Caridea: Acanthephyridae) with an analysis of its phylogenetic position based on molecular data

A new species of pseudionine parasite is described from the deep-sea shrimp Notostomus gibbosus A. Milne-Edwards, 1881, collected in the Gulf of Mexico, the first record of a bopyrid parasitizing any member of the family Acanthephyridae Spence Bate, 1888. Morphological and molecular data are provided to support the inclusion of the new species and 12 other branchial ectoparasites of caridean shrimps in the genus Cryptione Hansen, 1897 that is resurrected herein. Cryptione is sister to the genus Pseudione sensu stricto, ectoparasites of axiid and callianassid shrimps as well as nephropid lobsters. The new species Cryptione grandis can be distinguished from its closest congeners including C. parviramus (Adkison, 1988) from the Gulf of Mexico by several female and male characters. The epicaridium larvae of C. grandis were examined with scanning electron microscopy (SEM), only the second description of this stage for any species in the genus. A table listing all species in Cryptione and taxonomic notes on some species are provided.

The trace fossil Thalassinoides paradoxicus Kennedy, 1967 revisited from its type locality (Albian-Cenomanian chalk, SE England)

The trace fossil Thalassinoides includes ichnospecies that have been recognised for a long time and widely used in the interpretation of depositional systems. Despite its broad occurrence, the ichnotaxonomic status of this important ichnogenus is far from being unmistakable, which in turn hampers its application in palaeoenvironmental reconstructions. One of the most common ichnospecies is Thalassinoides paradoxicus, originally described from the Paradoxica Bed of the Lower Chalk in the Hunstanton Cliff in SE England. To demarcate this characteristic form from similar ichnospecies, T. paradoxicus is reexamined and described from its type locality. It is characterised by an ‘irregular, very extensive horizontal burrow network, occurring at several levels, connected by vertical shafts’ (Kennedy), but its morphological variability also includes a range of significant architectural elements as well as burrow portions with a laminated wall, scratches and pellets. A series of colonisation events along omission surfaces can be reconstructed based on the occurrence of several burrow generations. T. paradoxicus is an important constituent of shallow-marine environments and subtle variations in morphology may help to constrain facies interpretations. Based on modern analogues and finds of body fossils within their burrows, decapod crustaceans (foremost callianassid shrimp) are known producers of T. paradoxicus from the Mesozoic onwards, whereas older records can be attributed to other malacostracans but also trilobites.

Long-term variability in larval recruitment rates of a callianassid shrimp population on an intertidal sandflat in an estuary-to-coastal ocean interface area in relation to river discharge and shelf water movement, western Kyushu, Japan

Long-term variability in larval recruitment rates of a callianassid shrimp population on an intertidal sandflat in an estuary-to-coastal ocean interface area in relation to river discharge and shelf water movement, western Kyushu, Japan

A new symbiotic scale worm (Polychaeta: Polynoidae) living in association with burrowing callianassid shrimps in the Black Sea

A new scale worm tentatively assigned to the genus Malmgrenia McIntosh, 1874 (Annelida: Polynoidae) is described from the burrows of callianassid shrimps belonging to the genus Gilvossius Manning et Felder, 1992 (Decapoda: Axiidea: Callianassidae). This is the first association involving callianassid shrimps with a polynoid scale worm, known from the Black Sea (northeastern basin) and even for the Atlantic Ocean basin. The taxonomy of the new species, as well as the previously known associations of scale worms with callianassid shrimps are also discussed.

Applicability of the source–sink population concept to marine intertidal macro‐invertebrates with planktonic larval stages

AbstractLocal populations of marine benthic macro‐invertebrates with planktonic larvae are believed to be in source–sink relationships via larval dispersal in a regional population complex. Practically, such a region is definable only after connectivity of constituent local populations is explored. Numerical simulations abound for hydrodynamic connectivity by larvae between local/regional populations. Empirical studies have scarcely integrated inter‐local connectivity and intra‐local population dynamics into demographic connectivity analysis. I review the current research and indicate fundamental and technical problems to demonstrate that some source–sink systems in intertidal shores, which are most accessible among benthic habitats, are a good model. The challenge in benthic source–sink research comes from that existent local populations may not be self‐sustaining because of low larval self‐seeding rates and/or low benthos' survival rates and yet can persist as latent sinks. They may receive larvae leaking from sources at good‐quality habitat patches with stationary larval retention areas for self‐recruitment. On an intertidal sandflat in an estuary–coastal ocean region, Kyushu, Japan during 1979–2019, the population of a trochid gastropod with 3‐ to 9‐day larval duration became extinct and recovered. The extinction was caused by sediment destabilization by a callianassid shrimp population which increased in the early 1980s. The gastropod recovery was owing to the shrimp decline by stingray predation and the transport of larvae from some self‐sustainable populations with lower shrimp densities 30 km away. It was estimated that the gastropod population before the shrimp proliferation on that sandflat might be a latent sink requiring allochthonous larval subsidy due to epi‐benthic predation on juveniles.

Ichnologic note first occurrence of the microcoprolite Palaxius salataensis in the Aptian (Lower Cretaceous) of northeast Mexico and its paleoecological implications

Microcoprolites of Palaxius salataensis are non-skeletal carbonate grains produced by callianassid shrimps. This ichnospecies is recognized by four longitudinal canals arranged around a bilateral plane of symmetry, with crescent outline in cross-section. Palaxius salataensis has been previously reported from other countries and in strata from the late Paleozoic to the Mesozoic. In this study, we describe the first Aptian record of the ichnospecies, the first Cretaceous occurrence in North America, and the fifth occurrence worldwide. Palaxius salataensis was found in a packstone-grainstone with abundant pellets and common gastropod shell fragments and subangular, poorly sorted intraclasts. The paleoenvironment was characterized by shallow-waters with high energy conditions, occurring between fair-weather wave base and storm wave base, close to the platform margin, where well-oxygenated and nutrient-rich conditions predominated. The microcoprolite-rich bed of the La Huasteca Canyon occurs on top of an oolitic grainstone interval in the upper levels of the Cupido Formation, interpreted as the termination of the early Aptian Oceanic Anoxic Event 1a (OAE 1a). The presence of P. salataensis in the upper levels of the Cupido Formation is directly related to the availability of organic matter rather than to oxygen recovery.

Semilunar postlarval settlement periodicity ensuing from semilunar larval release cycle in the Nihonotrypaea harmandi (Crustacea, Decapoda, Axiidea, Callianassidae) population on an intertidal sandflat in an open marine coastal embayment

AbstractMany decapod crustaceans in marine intertidal habitats release larvae toward coastal oceans, from which postlarvae (decapodids: settling‐stage larvae) return home. Decapodid settlement processes are poorly understood. Previous studies showed that in Kyushu, Japan, the callianassid shrimp population on an intertidal sandflat of an open bay joining the coastal ocean near a large estuary released eight batches of larvae basically in a semilunar cycle from June through October and that decapodids performed diel vertical migration, occurring in the water column nocturnally. We conducted (a) frequent sampling for population density and size‐composition on the sandflat through one reproductive season, (b) planktonic and benthic sampling for decapodids around the bay mouth, and (c) current meter deployment at three points across the bay mouth for tidal harmonic analysis. On the sandflat, six batches of newly‐settled decapodids (settlers) occurred in a semilunar periodicity until October, with peaks occurring 0–3 days before syzygy dates except for the first one. For larval Batches 1–4, buoyancy‐driven shoreward subsurface currents during July to mid‐October would transport some pre‐decapodid‐stage larvae (zoeae) toward the bay. The absence of expected settler Batches 7–8 would be due to the converse subsurface currents caused by water‐column mixing and seasonal winds after mid‐October, carrying zoeae offshore. Once in the bay, phasing of night and nighttime‐averaged shoreward tidal current explained the settlement pattern for Batches 1–4. For Batches 5–6 occurring in mid‐September to mid‐October, water currents generated by seasonal wind and tidal forcings may have caused peak settlement after the time expected from tidally‐driven decapodid transport.

Effect of stingray (Hemitrygon akajei) foraging on a ghost shrimp population (Nihonotrypaea harmandi) on an intertidal sandflat, western Kyushu, Japan

Callianassid shrimp residing in deep burrows have large bioturbating effects on marine soft-bottom communities. A few predators that excavate deep pits could have substantial effects on shrimp populations, as well as knock-on effects. Processes and consequences of such effects on shrimp populations are poorly understood. On a 300-m-wide intertidal sandflat area between tide marks in western Kyushu between 1989 and 1994, shrimp population densities were stable, reaching >1300individualsm–2. Dasyatid stingray feeding pits reaching depths up to 20cm occurred abruptly in large numbers in 1994, after which shrimp densities decreased yearly to hundreds of individuals per square metre in 2001. The densities of ray feeding pits formed per day were monitored every or every other spring tide between 2000 and 2001. Schools of rays were enclosed during submerged times and their body sizes recorded alive to determine size-frequency distribution. The body-size frequency distributions of shrimp were compared among the gut contents of several rays, ray feeding pits and intact sandflat. Reductions in the shrimp density per ray feeding bout compared with the density on the intact sandflat were recorded. A model of daily predation at different seasonal rates was used to simulate the yearly change in shrimp density. The result was consistent with the actual change.

Millennial‐Scale Age Offsets Within Fossil Assemblages: Result of Bioturbation Below the Taphonomic Active Zone and Out‐of‐Phase Production

AbstractOceanographic and evolutionary inferences based on fossil assemblages can be obscured by age offsets among co‐occurring shells (i.e., time averaging). To identify the contributions of sedimentation, mixing, durability, and production to within‐ and between‐species age offsets, we analyze downcore changes in the age‐frequency distributions of two bivalves on the California shelf. Within‐species age offsets are ~50–2,000 years for Parvilucina and ~2,000–4,000 years for Nuculana and between‐species offsets are 1,000–4,000 years within the 10‐ to 25‐cm‐thick stratigraphic units. Shells within the top 20–24 cm of the seabed are age‐homogeneous, defining the thickness of the surface completely‐mixed layer (SML), and have strongly right‐skewed age‐frequency distributions, indicating fast shell disintegration. The SML thus coincides with the taphonomic active zone and extends below the redoxcline at ~10 cm. Shells >2,000–3,000 years old occurring within the SML have been exhumed from subsurface shell‐rich units rich where disintegration is negligible (sequestration zone, SZ). Burrowers (callianassid shrimps) penetrate 40–50 cm below the seafloor into this SZ. The millennial offsets within each increment result from the advection of old shells from the SZ, combined with an out‐of‐phase change in species production. Age unmixing reveals that Parvilucina was abundant during the transgressive phase, rare during the highstand phase, and increased steeply in the twentieth century in response to wastewater. Nuculana was abundant during the highstand phase and has declined over the past two centuries. This sequestration‐exhumation dynamic accentuates age offsets by allowing both the persistence of shells below the SML and their later admixing with younger shells within the SML.

Spatial distribution and population dynamics of Callichirus major (Crustacea, Callianassidae) in a tropical sandy beach, northeastern Brazil

AbstractCallichirus major is a callianassid shrimp widely used as live bait by Brazilian recreational fishers. Here, we present information about spatial distribution and population dynamics of C. major based upon both the number of burrow openings and the number of specimens collected monthly between July 2011 and September 2012 at Aruanda Beach, northeastern Brazil. Burrows occupied a spatial area between 68 m (November 2011) and 107 m wide (April 2012), starting at the intermediate intertidal area (~48 ± 5 m below the high tide mark) and extending their distribution to the sublittoral zone. Mean density ranged from 5.6 ± 3.6 (December 2011) to 35.6 ± 18.7 burrows per m2 (July 2012). The population had a female‐biased sex ratio (1:1.5 males:females). Dorsal oval length was 3.97–14.65 mm for males and 4.31–16.30 mm for females. Weight–length relationships for males and females were both allometrically positive. Ovigerous females occurred from November 2011 to March 2012, with a mean fecundity of 2327 ± 1290 eggs, and recruitment was observed in June 2012. The von Bertalanffy growth parameters estimated for males were: L∞ = 15.00 mm, K = 0.78/year, C = 0.2, and WP = 0.6. For females, the model parameters were: L∞ = 16.50 mm, K = 0.78/year, C = 0.2, and WP = 0.6. The total instantaneous mortality rate for males and females was 1.72 and 1.11/year, respectively. The pattern of distribution, density, and reproductive cycle was similar to that reported for the species in southern‐southeastern Brazil. However, the asymptotic lengths estimated here for both males and females were higher, suggesting an underexploited status for this population, inhabiting an area where penaeid shrimps are the most preferred live bait used by local recreational fishers.

Normal Delayed Establishment of a Semilunar Brooding and Larval Release Cycle in the Course of the Reproductive Season of the Ghost Shrimp Population on a Warm Temperate Intertidal Sandflat

Many decapod crustaceans inhabiting estuarine and coastal shores with larvae that develop in the coastal ocean release them at nocturnal ebb tides in a semilunar or lunar spring tide cycle under semidiurnal tidal regimes. In common brachyurans on warm temperate shores, this release cycle becomes first established in their mid-reproductive season. How this occurs is poorly understood, under the dichotomous views that peak larval release in each spring tide during the mid- to late season is timed to the syzygy date or the date with the largest tidal range (TR) and fastest tidal currents a few days later. The callianassid shrimp, Nihonotrypaea harmandi, inhabiting an intertidal sandflat in midwestern Kyushu, Japan, under a mixed, mainly semidiurnal, tidal regime has a reproductive season from June through October at water temperatures ranging from 20°C to 29°C. Frequent population sampling was conducted in 1993 (to mid-August) and 1994 (to early November), with cold and hot summers, respectively. Observations and experiments on embryo deposition and larval release, and measurement on water level and velocity were performed in other years. Harmonic analysis of tides was made on the water level and velocity and applied to those in 1994. Female shrimp released larvae at nocturnal ebb tides. The population comprised three age cohorts (one 2-y-old and two 1-y-old), and eight distinct larval releases occurred during June to October, each forming a batch preceded by embryo deposition by 3 wk to 2 wk linked to 20°C to ≥ 25°C in water temperature, respectively. Syzygy-centered peak embryo deposition first occurred in late July (for the third batch in 1994) and early August (for the fourth batch in 1993), with each batch dominated by the youngest cohort. Afterward, peak larval release immediately followed by peak embryo re-deposition every spring tide occurred in 1994. In the earlier reproductive season, the older two cohorts were dominant in the mature individuals, with a longer longevity of the oldest and more dominance of the second oldest in 1993 than in 1994, and embryo deposition was only weakly synchronized with syzygies, followed by longer embryo developmental durations. The peak larval release dates for the first two (in 1994) or three (in 1993) batches were between neap and spring tides. Thereafter, the peak date for each batch approached the largest-TR date but never coincided precisely. Seaward larval transport efficiency evaluated by the product of mean water velocity per ebb and ebb duration suggests suboptimal values throughout the reproductive season.

Facultative commensalism of a free-burrowing urothoid amphipod with a deep burrow-dwelling callianassid shrimp in intertidal sand

Species of the free-burrowing amphipod genus, Urothoe, are common on open sandy beaches. On intertidal sandflats, some species are associated with burrows or tubes of large infauna. How this link is formed and persisting under sheltered conditions was examined. On an intertidal sandflat in mid-western Kyushu, Japan, U. carda co-occurred with the deep burrow-dwelling callianassid shrimp, Nihonotrypaea harmandi, along a 300-m transect between tide marks. Amphipods resided in the surface 5-cm sediment outside shrimp burrows, as confirmed by sediment coring and burrow casting. In summers 1980 and 1981, the shrimp and amphipod populations were confined to the upper shore at mean densities of 182 and 701 inds m−2, respectively. In winter to spring, when the sediment surface mixing was caused by seasonal wind-induced waves, the amphipod but not the shrimp expanded down to the lowest shore. Later, by 1983, the shrimp increased mean density by 2.5 times and now also ranged to the lowest shore. In the summers of 1984, 2010, and 2015, the amphipod expanded to the lowest shore as well, with small variations in population size. Three marked changes in substrate properties were associated with shrimp inhabitation: thicker oxidized layer (proxy for oxygenated layer) in the sediment column; looser surface sediment, as evaluated with vane shear strength; and coarser and better-sorted surface sediment with less mud content. At least the former two changes were attributable to shrimp bioturbation, which could provide the amphipod with more permeable and softer substrates, leading to the formation of facultative commensalism.

Phytoplankton as a principal diet for callianassid shrimp larvae in coastal waters, estimated from laboratory rearing and stable isotope analysis

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 592:141-158 (2018) - DOI: https://doi.org/10.3354/meps12507 Phytoplankton as a principal diet for callianassid shrimp larvae in coastal waters, estimated from laboratory rearing and stable isotope analysis Yu Umezawa1,2,*, Akio Tamaki1, Toshikazu Suzuki1, Seiji Takeuchi1, Chikage Yoshimizu3, Ichiro Tayasu3 1Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Bunkyo-machi, Nagasaki 852-8521, Japan 2Department of Environmental Science on Biosphere, Tokyo University of Agriculture and Technology, Saiwai-cho, Fuchu, Tokyo 183-8509, Japan 3Research Institute for Humanity and Nature, Motoyama, Kamigamo, Kyoto 603-8047, Japan *Corresponding author: umezawa@me.tuat.ac.jp ABSTRACT: The field diet of meroplanktonic decapod crustacean larvae is poorly known, despite standard use of microzooplankton as food in laboratory culture. Using callianassid shrimp Nihonotrypaea harmandi larvae collected from a 65 m deep inner-shelf location off mid-western Kyushu, Japan, between June and August 2012 and 2013 and mass-reared in the laboratory, a phytoplankton-based diet through larval development (zoeae I–VI to decapodid) was demonstrated. When the pure-cultured diatom Chaetoceros gracilis was fed to zoeae, survival rate to decapodids was 3.4 to 3.9% in 26 to 40 d at 22°C, which was comparable to previous rearing results for zoeae fed microzooplankton. Trophic enrichment factors (TEFs) from stable isotope (SI) analysis of zoeal whole-body tissue in the laboratory were 2.0‰ for δ13C and 1.9‰ for δ15N. In the field water column, diatoms dominated the nano- to micro-sized plankton, accounting for 38 to 81% of the biovolume, followed by heterotrophic protists. The trophic position (TP) estimated from amino acid-specific δ15N values for the field-collected zoeae VI was 2.1 (TPGlu/Phe) or 2.7 (TPAla/Phe), suggesting that those zoeae fed on mixtures of phytoplankton and heterotrophs including protists. Bulk SI analyses were performed for particulate organic matter (POM; proxy for phytoplankton), microzooplankton (mainly calanoid copepods), and shrimp zoeae to elucidate the diet of larvae in the water column. A shift in SI from fresh to degraded POM was determined through the incubation of field-collected POM. Based on this shift during degradation and larval TEFs, phytoplankton and their sinking detritus with heterotrophic protists were estimated to be the principal diet for those larvae residing mostly below the chlorophyll maximum layer. KEY WORDS: Nihonotrypaea harmandi · Zoea · Rearing · Diatom · Isotopic trophic enrichment factor · Amino-acid-δ15N-based trophic position · Phytodetritus · Protists Full text in pdf format Supplementary material PreviousNextCite this article as: Umezawa Y, Tamaki A, Suzuki T, Takeuchi S, Yoshimizu C, Tayasu I (2018) Phytoplankton as a principal diet for callianassid shrimp larvae in coastal waters, estimated from laboratory rearing and stable isotope analysis. Mar Ecol Prog Ser 592:141-158. https://doi.org/10.3354/meps12507 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 592. Online publication date: March 29, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Field survey and resin casting of Gymnogobius macrognathos spawning nests in the Tatara River, Fukuoka Prefecture, Japan

We investigated the spawning nests of Gymnogobius macrognathos on a tidal flat in the Tatara River, Fukuoka Prefecture, Japan. Digging uncovered 19 spawning nests. The number of eggs and the standard length of the guarding male were positively correlated. Nine spawning nests were examined using in situ resin casting. All casts had structures characteristic of callianassid shrimp burrows and were most likely those of Nihonotrypaea japonica. Spawning nests had significantly greater average diameters than shrimp burrow openings and may have been widened by G. macrognathos.

Solving a cold case: New occurrences reinforce juvenile callianassids as the Ophiomorpha puerilis tracemakers

The ichnotaxon Ophiomorpha puerilis was erected based on material from late Pleistocene shallow-marine, siliciclastic deposits of southeastern Brazil. These tiny burrows with a distinctive lining of cylindrical pellets having rounded ends were originally interpreted as burrows of juvenile callianassid shrimp, with polychaetes also considered as a possible tracemaker. Recent discoveries of O. puerilis in late Pleistocene shallow-marine carbonates from two localities in the Bahamas and from the Miami Limestone of south Florida, described herein, have expanded significantly the geographic range of the ichnotaxon and provided numerous, well preserved specimens for detailed structural analysis of its burrow form and pellets. The new information strengthens the interpretation of juvenile callianassids as the tracemakers, resolving the “cold case” of the burrow's tracemaker. Microscopic analyses revealed that the pellets of O. puerilis are constructional, not fecal. Furthermore, larger forms of Ophiomorpha are common and occur in close association with O. puerilis at each locality. These new data allowed close comparison of O. puerilis pellets with those of Sergio mirim, a modern callianassid from southeastern Brazilian beaches, Ophiomorpha nodosa from Brazilian Pleistocene deposits, and fossil polychaete burrows filled with fecal pellets as described in the literature. The combined evidence allows us to exclude polychaetes as potential O. puerilis tracemakers. Rather, O. puerilis records the settling and initial burrowing behavior of callianassid decapodids. The characteristics of an Ophiomorpha ichnofabric with the addition of O. puerilis also is described and explored. An emended diagnosis for the O. puerilis ichnotaxon is provided, based on the new structural data for this burrow.

Associations between the pink wormfish, Microdesmus longipinnis (Weymouth), and the ghost shrimp, Lepidophthalmus louisianensis (Schmitt), in artificial burrows

Microdesmus longipinnis (Weymouth) is a small estuarine teleost fish that is known to feed on the eggs of the callianassid shrimp, Lepidophthalmus louisianensis (Schmitt). In the course of collecting M. longipinnis for physiological studies we noticed that there seemed to be a higher preference towards burrows of non-gravid and male shrimp than one would expect if the driving force behind this relationship was exclusively egg predation. In an attempt to expand upon the understanding of the relationship between these two animals we tested the hypothesis that the fish are not seeking out burrows based solely on the presence of eggs but rather the presence of the shrimp. Laboratory experiments demonstrated that M. longipinnis positively associated with male L. louisianensis when compared to empty burrows supporting the idea of a more complex relationship that has previously been reported in the literature. Further study is needed to fully determine the nature of the relationship between M. longipinnis and L. louisianensis.

Dynamics of bacterial community structure on intertidal sandflat inhabited by the ghost shrimp Nihonotrypaea harmandi (Decapoda: Axiidea: Callianassidae) in Tomioka Bay, Amakusa, Japan

Callianassid (ghost) shrimp has been claimed as an ecosystem engineer, as it is one of the most powerful bioturbating macrobenthos in intertidal sandflats. However, our knowledge about the relationship between areal distribution of bottom-dwelling ghost shrimps and dynamics of sediment microbial community structure remains obscured. We used automated ribosomal intergenic spacer analysis (ARISA) to reveal the bacterial community dynamics in the sediment of intertidal sandflat of Tomioka Bay, Kyushu, Japan, which is predominantly inhabited by a burrow-dwelling callianassid shrimp Nihonotrypaea harmandi. We found that the bacterial community structures of high and middle shrimp population areas were significantly differentiated from those of low population area (ANOSIM, R=0.10–0.18, p<0.01), while the former two areas were statistically indistinguishable (ANOSIM, R=−0.015, p>0.1). These results illustrated the potential importance of shrimp population density as a key factor in shaping the bacterial community structure and interpreting their dynamics in the sandflat. Furthermore, greater similarity between burrow and non-burrow communities was found in samples taken in autumn through winter than in those in summer (one-way ANOVA, p<0.05), whereas the phylotype richness was not simply differentiated by seasons. These results suggest not only that environmental variables including water temperature and salinity of the water column overlying the sandflat could exert notable impacts on the sediment bacterial community dynamics, but that the bio-irrigation and mixing by the ghost shrimp in permeable sandflat would strongly homogenize sediment particles, enhance solute transport surrounding the burrow and ambient subsurface substrate, and therefore reduce spatial differentiation of the bacterial community structure between the two sites. A comparison between present and previous studies of axiidean (former taxonomic group name, thalassinidean) ghost shrimps provides us with a comprehensive understanding of the shrimps' impacts on bacterial community dynamics, highlighting the importance of sediment permeability, a characteristic determined by the type of sediment, as a key controlling factor to shape spatial heterogeneity of bacterial community structure around burrow.

A new genus for Entophilus mirabiledictu Markham & Dworschak, 2005 (Crustacea: Isopoda: Cryptoniscoidea: Entophilidae) with remarks on morphological support for epicaridean superfamilies based on larval characters.

A detailed reexamination of male and female Entophilus mirabiledictu Markham & Dworschak, 2005 (an endoparasite of callianassid shrimp), resulted in recognition of seven female and five male characters that separate the species from its sole congener, E. omnitectus Richardson, 1903 (an endoparasite of munidid squat lobsters). These characters show that the two species are so different as to warrant E. mirabiledictu being placed in its own genus within the Entophilidae. Additionally, a review of the morphological features of entophilid cryptoniscus larvae led to the finding that the number of flagellar segments on the second antenna offers morphological support for a recent molecular phylogeny of epicaridean taxa that rearranged the component families within the two recognised superfamilies. This work highlights the power of using larval characters in testing hypotheses on the evolutionary relationships of epicaridean taxa.

Biodetrital carbonates on the Adriatic continental shelf imprinted by oxidation of seeping hydrocarbons

The gas-productive Bonaccia area located at ca. 80–90 m below sea level offshore Ancona (Central Adriatic Sea) is site of hydrocarbon-derived carbonate production. The carbonates include large dm-sized slabs (bryozoan limestone), smaller concretionary aggregates, mudstones and pipes. The mudstones and botryoidal aragonite cements within limestones show δ13C values as low as −47.8‰ VPDB, consistent with seepage of isotopically light hydrocarbons (e.g. methane). These hydrocarbon-derived carbonates commonly incorporate abundant shell remains, deriving from the prevalently coarse bioclastic-rich muddy deposits from post-glacial transgressive units. It is, therefore, hypothesized that hydrocarbon-rich fluids permeated the post-glacial sediments, resulting in seafloor seeps that were inhabited by chemosymbiotic lucinid bivalves and burrowing callianassid shrimps; fossils and traces of which have been found in the Bonaccia carbonates. Microbial oxidation of the reduced compounds contained in the seep fluids led to a locally patchy carbonate cementation of the sediments at the seep sites. The pipes are interpreted as decapod burrows that subsequently served as conduits for hydrocarbon leakage. Seepage is probably still active at present as testified by gas production at the study site. Interestingly, seep carbonates exhumed by erosion served as hard substrate for fouling benthos (i.e., bryozoans, oysters and red algae) in the Holocene. The main products of the processes at the Bonaccia study site are composite bryozoan-dominated limestones, whose multi-step and complex history was unfold thank to radiocarbon dating of key components and precise stratigraphic control. The Bonaccia case-study can serve as a model for the interpretation of ancient analogs, such as bryozoan dominated limestones and mudstones of Paleozoic to Mesozoic age, which are not uncommon in the geological record. It further calls for caution in assuming that the presence of dominant macrobenthic fossil in old hydrocarbon-derived limestones implies its ecological connection to active seepage.

Assessment of benthic disturbance associated with stingray foraging for ghost shrimp by aerial survey over an intertidal sandflat

One notable type of bioturbation in marine soft sediments involves the excavation of large pits and displacement of sediment associated with predator foraging for infaunal benthos. Batoids are among the most powerful excavators, yet their impact on sediment has been poorly studied. For expansive tidal flats, only relatively small proportions of the habitat can be sampled due to physical and logistical constraints. The knowledge of the dynamics of these habitats, including the spatial and temporal distribution of ray bioturbation, thus remains limited. We combined the use of aerial photogrammetry and in situ benthic sampling to quantify stingray feeding pits in Tomioka Bay, Amakusa, Japan. Specifically, we mapped newly-formed pits over an 11-ha section of an intertidal sandflat over two consecutive daytime low tides. Pit size and distribution patterns were assumed to scale with fish size and reflect size-specific feeding behaviors, respectively. In situ benthic surveys were conducted for sandflat-surface elevation and prey density (callianassid shrimp). The volume versus area relationship was established as a logistic function for pits of varying sizes by photographing and refilling them with sediment. This relationship was applied to the area of every pit detected by air to estimate volume, in which special attention was paid to ray ontogenetic change in space utilization patterns. In total, 18,103 new pits were formed per day, with a mean individual area of 1060cm2. The pits were divided into six groups (G1 to G6 in increasing areas), with abundances of G1, G2+G3, and G4−G6 being medium, high, and low, respectively. Statistical analyses using generalized linear models revealed a marked preference for the higher prey-density areas in G1 and the restriction of feeding grounds of G4−G6 to the lower shore, with G2+G3 being generalists for prey density and sandflat elevation. The lower degrees of overall bioturbation by G1 and G4−G6 were spatially structured for the eight sub-areas demarcated by prey density and sandflat elevation, while G2+G3 homogenized the state over the sandflat. The newly-formed pits׳ sub-areal mean numerical, excavated-areal, and displaced-sediment-volume densities per day were confined to small ranges: 0.14–0.17m−2, 132–223cm2m−2, and 551–879cm3m−2 (latter two including 119 shallow non-pit excavations). These bioturbation rates are positioned at relatively high levels compared with those by rays from other geographic regions. The present procedure is applicable to the assessment of disturbance by any surface-sediment excavators on tidal flats if their pit dimensions are discernible from the air.