Site selection and behavior of sponge and bivalve borers in shells of the cretaceous oysters exogyra cancellata and pycnodonte mutabilis from delaware,U.S.A

In shells of the oysters Exogyra cancellata and Pycnodonte mutabilis from the Mount Laurel and Marshalltown Formations (Campanian‐Maestrichtian), three‐quarters of all valves bear sponge borings (Entobia isp.) borings and 30% have borings of a lithophagid bivalve (Gastrochaenolites isp.). Non‐random distributions of these euendoliths, documented in this paper, may in part be accounted for by differential survival of sponge and lithophagid larvae and spat in varying circumstances. In addition, exterior shell architectures and post‐mortem orientations of shells are inferred to have prompted active geophobic (antigravity), rugophilic (groove‐seeking), and rheophilic (current‐seeking) behavior that enhanced survivorship of the settling larvae.     

Taphonomy of modern and fossil intertidal gastropod associations from Isla Santa Cruz and Isla Santa Fe, Galápagos Islands

Examination of modern gastropod associations from the low intertidal zone of Isla Santa Cruz suggests that fossil rocky intertidal deposits from this tropical locality will be taphonomically compromised in three ways: (1) Marine hermit crabs, by their use of empty gastropod shells, will mix the shells from varying tidal heights and habitats, thus facilitating mixed associations of such shells in the fossil record, (2) encrusting organisms on crab-inhabited shells are abundant, while boring organisms are almost non-existent, indicating possible differences in postmortem shell retention, and (3) intertidal shells are further taphonomically altered by terrestrial hermit crabs, which transport the shells onto land as well as physically modify the shells. Gastropod fossils from beach and terrace deposits on Isla Santa Fe are interpreted to be a mixed assemblage of rocky intertidal assemblage with few shells indicating influence from marine hermit crabs. Modification of the shell by marine and terrestrial hermit crabs was also evident. A unique polish to the shells at one locality is attributed to the marine iguanas and is only found in the terrace site biologically bulldozed by egg-laying iguanas. Few studies exist on modern rocky intertidal associations in the Galápagos, and the fossil record of rocky shores may provide a baseline for future studies in how community structure has changed over since the advent of humans. Galapagos, C oenobita C ompressus , gastropods, humans, Gulf of California, bionts, nutrients.
Sally E. Walker, Department of Geology, The University of Georgia, Athens, Georgia, USA; 8th September, 1994; revised 28th June, 1995.     

Host‐specific acrothoracid barnacles on Middle Devonian platyceratid gastropods

Borings, attributed to acrothoracic barnacles, occur on the platyceratid gastropod Naticonema lineatum (Conrad) from the Middle Devonian Hamilton Group of western New York and rarely in specimens as old as the Early Devonian. These latter are the oldest known acrothoracid borings are in the fossil record. The borings are consistently developed as laterally compressed, inequilateral pouches exclusively on these gastropods, commonly as dense infestations.

Naticonema shells yielding borings typically occur associated with partially articulated qrinoid remains, and they are sometimes found attached to crinoids in a manner similar to coprophagous Platyceras. In addition to barnacle borings, Naticonema shells often bear thin encrustations of bryozoans which are usually perforated by these borings but sometimes also overgrow them. Barnacles bored live hosts; gastropods prevented shell penetration by producing cyst‐like secondary secretions of calcite beneath acrothoracid boreholes.

The relative antiquity of these borings and their association with coprophagous platyceratids makes their discovery particularly significant in revealing aspects of the early ecology of barnacles. Attachment to the host commensal gastropods was one of the first successful life modes of these crustaceans prior to their later diversification to other habitats. Mississippian and Pennsylvanian occurrences of similarly bored gastropods demonstrate continuity of the barnacle‐gastropod‐crinoid ecological association from the Middle to Late Paleozoic.     

Traces of Naticid Predation on the Gryphaeid Oyster Pycnodonte dissimilaris: Epifaunal Drilling of Prey in the Paleocene

Traces of drilling predation by naticid gastropods were observed on 51 valves of the free-lying, semi-infaunal oyster Pycnodonte dissimilaris (Gryphaeidae) from the Paleocene Hornerstown Formation, in New Jersey. Stereotypic behavior of the predator is indicated by the highly constrained placement of drill holes, 94% of which are centrally located on the oyster shells. Predator—prey mismatches in size, involving small predators that drilled through the upper valves of relatively large oysters, are documented by comparison of outer borehole diameter, as an index of predator size, with the sizes of the oyster shells. Results of this analysis suggest that at least some prey were drilled epifaunally, as they were too large to be manipulated and buried by the predator. This indicates, together with reports of epifaunal drilling by living naticids, that such behavior is geographically and stratigraphically more widespread in the Naticidae than has previously been acknowledged. This in turn suggests that epifaunal drilling of prey is a plesiomorphic, opportunistic mode of behavior, conserved in the evolution of the Naticidae, that has permitted subsequent escalation or expansion in range of naticid foraging from a more narrowly defined infaunal paradigm into exposed intertidal refugia.     

Bivalve borings in Lower Jurassic Lithiotis fauna from northeastern Italy and its palaeoecological interpretation

Random shell sections of the Pliensbachian (Early Jurassic) larger bivalve Opisoma from columns within the Main Post Office building of Ferrara, northern Italy, have been discovered to bear neat clavate-shape boreholes. These boreholes belong to the ichnogenus Gastrochaenolites Leymerie and represent bivalve borings. Opisoma is a subordinate component of the Lithiotis fauna characterised by aberrant shells thriving in tropical lagoonal settings which were widespread throughout the Tethyan and Panthalassa coasts. Although the Lithiotis fauna is well known in the palaeontological literature, no bivalve boring have been so far been formally described. The uniqueness of the morphology, size and substrate of these borings merits the designation of the new species Gastrochaenolites messisbugi ichnosp. nov. which thereby represents the first ichnospecies described from this fauna. The morphology of the boreholes and the included bivalves allows the boring activity to be ascribed to a mytilid bivalve. Palaeoecological and taphonomic analyses allowed the presence of the boreholes to be correlated to the Opisoma mode of life (epifaunal, free-living form) as well as to generally low sedimentation rates and seasonal mesotrophic conditions during an overall oligotrophic regime.

http://zoobank.org/urn:lsid:zoobank.org:act:CCF77B32-D459-4305-BC86-93F228852E50     

Reproductive and recruitment dynamics of clionaid sponges on oyster reefs in North Carolina

Boring sponges belonging to the family Clionaidae have become a destructive nuisance to eastern oyster (Crassostrea virginica) aquaculture and restoration efforts in the southeastern USA. Clionaid sponges colonize the inner layers of oyster shells and remove carbonate material, compromising the quality and marketability of the oyster; however, relatively little is known about reproduction and recruitment of these sponges. Using histological techniques, reproductive activity of clionaid sponges was monitored at two sites (Cedar Island and Masonboro Sound) in coastal North Carolina. Sponge recruitment to limestone tiles (5×5 cm), oyster shells, and clam shells was monitored in 2013 and 2014; recruitment to the limestone tiles was statistically higher than recruitment to clam or oyster shells. Overall, seasonal patterns in reproduction and recruitment of clionaid sponges were generally similar at the two sites. Three species of clionaid sponge were found during field sampling (Cliona celata, C. lobata, and C. truitti), and reproductive activity (eggs and spermatocysts) of these species was observed from April to November, with peak reproduction occurring from June to September for C. lobata and from August to September for C. celata. Recruitment peaked in late summer/early fall. Additionally, the relationship between environmental conditions (temperature, salinity, dissolved oxygen, pH, and chlorophyll a) and clionaid recruitment was explored using a regression model. At Cedar Island, the best‐fit model included salinity and dissolved oxygen, while the best‐fit model at Masonboro Sound included temperature, pH, and salinity. The data from this study show that the primary reproduction and recruitment pulses occur in the fall for local clionaids, and thus mitigation strategies should be applied in the late fall or winter to minimize infestations.     

Bioerosion experiments at Lizard Island,Great Barrier Reef

The rates at which dead coral substrates are modified by bioerosional processes were determined by exposing recently killed corals for up to four years in a variety of reef environments at Lizard Island (northern Great Barrier Reef). Grazers were the major croding agents of these coral substrates and exhibited differences between sites that varied between sampling periods. Subtidal reef slopes and lagoon environments of water depths < 20 m were subjected to higher average rates of grazing erosion (0.30–1.96 kg/m²/y) than shallow depths less than 1 m (0.07–0.26 kg/m²/y). A deep site at 20 m experienced low average rates of grazing (0.08–0.29 kg/m²/y). Boring rates by worms (polychaetes and sipunculans), sponges and molluscs were relatively low and varied between sites, but increased with length of sampling period as larger borers succeeded the initial colonizing small polychaete worms. We hypothesize from these experiments that the extent of boring in reef substrates will be influenced by the interaction between the succession of the boring community and the rate at which the substrate is destroyed by grazing. We suggest that the level of grazing modifies the successional pattern of borers by removing the surface substrate and continually exposing bare substrate that can be colonized by early boring colonists. Thus, constant high levels of grazing may maintain the boring community at an early successional stage and prevent the development of a mature boring community. In order to establish large borer populations, reef substrates must be protected from extensive grazing bioerosion. This interaction of grazing and boring has important implications for the way dead coral is preserved in different reef environments.     

Entobia exogyrarum (Frič, 1883) from the Upper Cretaceous of the Bohemian Cretaceous Basin

The validity of the little-known ichnospecies Entobia exogyrarum (Fri?) is verified. Shells of an oyster, Rhynchostreon suborbiculatum (Lam.), represent the substrate for the sponge borings. The borings occur in many Upper Cenomanian to Middle Turonian localities of the Bohemian Cretaceous Basin. This study revealed that the sponges attacked shells of living oysters. Entobia exogyrarum (Fri?) also represents one of the shallowest occurrences of Entobia borings in the Upper Cretaceous rocks.     

Bioerosional structures and pseudoborings from Late Jurassic and Late Cretaceous-Paleocene shallow-water carbonates (Northern Calcareous Alps, Austria and SE France) with special reference to cryptobiotic foraminifera

Examples of bioerosional processes (boring patterns) are described from shallow-water limestones of the Late Jurassic Plassen Carbonate Platform (PCP) and the Late Cretaceous to Paleocene Gosau Group of the Northern Calcareous Alps, Austria. Some micro-/macro-borings can be related to distinct ichnotaxa, others are classified in open nomenclature. In the Alpine Late Jurassic, bioerosional structures recorded from clasts in mass-flows allow palaeogeographical conclusions concerning the source areas. In particular, these are borings of the Trypanites-ichnofacies detected from clasts (Barmstein limestones) of the PCP or special type of bored ooids of unknown source areas or restricted autochthonous occurrences. In the Lower Gosau Subgroup, Gastrochaenolites macroborings occur in mobile carbonate clast substrates of shore zone deposits (“Untersberg Marmor”). Different types of borings are recorded from rudist shells and coral skeleton, some of which are referable to the ichnotaxon Entobia produced by endolithic sponges. In the present study, special attention is paid to the occurrences of the cryptobiotic foraminifera Troglotella incrustans Wernli and Fookes in the Late Jurassic and Tauchella endolithica Cherchi and Schroeder in the Late Cretaceous. The latter is so far only known to be from the Early Cenomanian of France and is reported here for the first time from the Late Turonian-Early Coniacian stratigraphic interval where it was found in turbulent carbonate deposits within borings penetrating bivalve shells or coralline algae. The records of cryptobiotic foraminifera from the Northern Calcareous Alps are supplemented by a single finding from the Middle Cenomanian of SE France. A palaeoenvironmental interpretation of the occurrences of the cryptobiotic foraminifera is provided.     

A New Ichnospecies of Gastrochaenolites Leymerie from the Pleistocene Port Morant Formation of Southeast Jamaica and the Taphonomy of Calcareous Linings in Clavate Borings

The ichnospecies Gastrochaenolites pickerilli isp. nov. is based on ten borings found in a shell of the gastropod Strombus gigas Linné from the Pleistocene (Sangamonian) Port Morant Formation of southeast Jamaica. These borings bear morphological similarities to Gastrochaenolites torpedo Kelly and Bromley but differ from all other Gastrochaenolites ispp. in having prominent and numerous calcareous meniscate structures arrayed adjacent to one side of the boring. These menisci are concave towards the center of the boring and are the remnants of calcareous tubes that lined earlier boreholes, that the boring bivalve treated as part of the lithified substrate when relocating. They are thus evidence of the former positions of borings that, unusually, were breached as the bivalve migrated sideways. Although this was a common behavior for Gastrochaenolites-producing bivalves within this substrate, the reason for it occurring is uncertain.     

Developmental instability of vascular plants in contrasting microclimates at ‘Evolution Canyon’

Rocellaria dubia bores into subtidal rocks of karsted limestone in the Adriatic Sea and elsewhere. It also bores into the shells of various bivalve species. The mechanism of boring has hitherto been debated, but examination of occupied shells suggest that this is achieved by mechanical (the shell) abrasion and chemical etching using secretions produced from glands in the anterior mantle. Fast‐growing bivalves such as Ostrea edulis and Pinna nobilis carry heavy R. dubia burdens, and encapsulate the borer in secreted calluses. Slow‐growing bivalves such as the burrowing Venus verrucosa and Glycymeris violacescens carry low R. dubia burdens, are less able to encapsulate the borers, and probably incur enhanced mortalities as a result. Individuals of R. dubia removed from their limestone boreholes re‐secreted adventitious tubes around their siphons, probably from glands in the posterior mantle. The lifestyle of R. dubia is now better understood, and its ability to bore bivalve shells in particular suggests how the more advanced tropical gastrochaenids Cucurbitula and Eufistulana have evolved from initial (as juveniles) bivalve shell borers into occupants of adventitious crypts and tubes, respectively. It is further argued that the Gastrochaenidae show convergent similarities with the similar crypt‐ and tube‐building representatives of the Clavagelloidea. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 786–804.     

Precipitation of iron in windowpane oyster shells by marine shell‐boring Cyanobacteria

Shells of windowpane oyster [Placuna placenta (L)] in the intertidal zone of the Zuari estuary, Goa, were often found to be black in color. Microscopical observation of partially decalcified shells showed the presence of cyanobacterial filaments encrusted with black precipitate. Microchemical test (Prussian blue reaction) and wavelength dispersive x‐ray analysis confirmed this precipitate to be of iron. Mineralogical studies of this black precipitate, using x‐ray diffraction and scanning electron microscopy, suggested the presence of iron as iron oxides. The cyanobacteria from such black shells were cultured in enriched seawater medium. In this medium also they precipitated iron as confirmed by Prussian blue reaction. They were identified as Plectonema terebrans Born et Flah and Phormidium sp.     

Quantification of radular marks as a method for estimating grazing of intertidal gastropods on rocky shores

Wax discs have been used previously on intertidal rocky shores to record the grazing activity of gastropods. This study has evaluated this methodology for recording grazing of four common intertidal microalgal grazers on intertidal shores in New South Wales, Australia. In the laboratory, the four species examined-the patellid limpet, Cellana tramoserica (Sowerby), the trochid, Austrocochlea porcata (A. Adams), the neritid, Nerita atramentosa Reeve and the littorinid, Bembicium nanum (Lamarck)-made distinctive marks in the wax. These allowed identification of each species or combinations of species grazing over the different discs. Field experiments showed that the intensity of grazing, as indicated by the mean number of scratches per disc, was positively related to the number of gastropods in the surrounding area during low tide for C. tramoserica. The number of scratches per disc in any area was correlated with the percentage of discs scratched. The relationship for C. tramoserica was found at two scales-in sites (approximately 3x3 m) and also in plots (50x50 cm) within sites. Therefore, densities that were measured when these limpets were inactive during low tide provided good estimates of grazing activity during high tide. This is largely because these limpets do not move far between where they rest and where they feed. The amount of microalgal food in the vicinity was not correlated with density, nor with grazing intensity. No relationship between density and grazing intensity was found for N. atramentosa, although experiments were only done in the field at one spatial scale (in sites, 3x3 m). Results obtained in the laboratory and in the field show that wax discs are useful to distinguish grazing by different species of gastropods on Australian rocky shores and allow tests of hypotheses about grazing activity at different spatial scales.     

An insect boring in an Early Cretaceous wood from Bornholm,Denmark

Abstract

An insect boring of unique shape is described from a lignitic layer within the Early Cretaceous (Berriasian) Skyttegård Member of the Rabekke Formation on Bornholm. Morphologically it cannot be compared to any modern or fossil wood borings, although some structures are reminiscent of Scolytidae, Platypodidae and Lymexylonidae. Most probably, however, the tracemaker was a female fungus-farming beetle, thus producing an agrichnion.     

Environment-specific shell shape variation in the boring mytilid Leiosolenus patagonicus

Environmental conditions induce phenotypic responses (behavioural, morphological and physiological) in many marine species. The boring mytilid Leiosolenus patagonicus inhabits different types of substrata, such as sandstone intertidal and hard subtidal substrata (here called ‘lifeless-substratum’) and shells of bivalve species (here called ‘live-substratum’), where they are exposed to different restrictions in their growth. We used geometric morphometric methods to compare the contour shell shapes from each type of substratum (live and lifeless) since we expected the body shape to differ between individuals from these different substrata. The results showed that the shell shape depends on the type of substratum where the larvae recruit. The mean shell shapes of individuals from the live-substratum are more slender than those of the individuals growing inside the lifeless-substratum. Individuals from live-substratum can adapt their phenotype depending on the oyster’s anti-parasitism responses, while in lifeless-substratum they are able to build their own refuges.     

A new mode of ammonite preservation – implications for dating of condensed phosphorite deposits

Unusual phosphatic casts of the ammonites Mortoniceras (Subschloenbachia) sp. and Stoliczkaia sp. from the upper Albian condensed phosphorite bed at Annopol, Poland, are discussed in terms of their taphonomic history. These specimens are interpreted as ‘secondary’ external casts of ammonite replicas preserved originally as attachment scars on oyster shells. The following genetic history is suggested for this previously undocumented mode of ammonite preservation: (1) settling of shells of dead ammonites on the seafloor; (2) colonization of these shells by oysters and formation of ammonite replicas on left valves of oysters; (3) dissolution of ammonite shells; (4) reworking and fragmentation of oyster shells; (5) casting of ammonite replicas by phosphatic material; and (6) separation of ammonite casts from oyster shells, either through mechanical disintegration or dissolution of the latter. The specimens studied were formed after dissolution of the ammonite conchs, not prior to this event as in the case of typical ammonite steinkerns (internal moulds). Therefore, they are here referred to as ‘pseudo‐steinkerns’. The time interval between loss of the original ammonite shells and the formation of oyster‐mediated pseudo‐steinkerns may be very extensive. Therefore, the pseudo‐steinkerns may potentially mislead in biostratigraphic dating of condensed phosphorite deposits.     

Book reviews

A total of 59 taxa of epibionts and endobionts occurred on experimentally deployed gastropod shells within one year of emplacement at depths ranging from 15 m to 260 m in the Bahamas. Most of the diversity occurred within 73 m of water depth. The experimental shells at the deepest sites (210 m, 260 m) were essentially pristine. Differences in experimental treatment affected the results: shells in bags contained more bionts than tethered shells, suggesting the bags had more protective areas for biont settlement. Soft‐bodied encrusters were restricted to the upper 73 m while foraminiferans and bryozoans exhibited bathymetric trends to the deepest sites. While boring algae and cyanobacteria were ubiquitous on the shells to 73 m, other bioeroders (e.g., clionid sponges) were rare. Bioaccumulation, rather than bioerosion, is the predominant process affecting mollusc shells during the first year of taphonomic exposure in carbonate systems to depths of 260 m.     

Can tropical freshwater zooplankton graze efficiently on cyanobacteria?

Zooplankton may at times graze cyanobacteria. However, their top-down effects are considered to be low, particularly in tropical regions dominated by small-size grazers that may be unable to consume efficiently filamentous or colonial species. Recently, cyanobacteria blooms were reported in the Senegal River hydrosystem. We conducted feeding experiments to assess the ability of copepods (Pseudodiaptomus hessei and Mesocyclops ogunnus), cladocerans (Moina micrura and Ceriodaphnia cornuta), and rotifers (Brachionus angularis, B. falcatus, and Keratella sp.) to control different cyanobacteria (Cylindrospermopsis raciborskii, Anabaena solitaria, A. flos-aquae, and Microcystis aeruginosa). None of the zooplankton species ingested M. aeruginosa. Mesocyclops ogunnus did not consume any of the cyanobacteria. Both cladocerans consumed the smallest filaments of cyanobacteria, whereas all the rotifers and P. hessei consumed a broader food-size spectrum. The functional feeding responses suggest that the concentration and size of the filaments are not the sole criteria for food consumption. The high zooplankton community grazing rates, estimated by applying the clearance rates measured in the laboratory to the in situ zooplankton abundance, indicate that grazing by zooplankton potentially constitutes an important controlling factor for the filamentous cyanobacteria in the tropics.     

Bioerosion along a bathymetric gradient in a cold-temperate setting (Kosterfjord, SW Sweden): an experimental study

In the cold-temperate setting of the Swedish Kosterfjord, a 2-year experiment was launched in order to assess bioerosion rates and to investigate the endolithic borer communities in relation to light availability (relative bathymetry), hydrography and exposure time. The inventory of microendolithic traces, studied by SEM analysis of epoxy resin casts of planted bivalve shells, yields diverse ichnocoenoses comprising a total of 21 traces produced by boring cyanobacteria (7), chlorophytes (4), fungi (6) and traces of uncertain affinity (4). The link between the endoliths (biotaxa) and the traces they leave (ichnotaxa) is evaluated by the study of the boring organisms in situ by transmission light microscopy of planted Iceland spar and bivalve shells. Additionally, the activity of various macroborers (foraminiferans, polychaetes, echinoids, gastropods and sponges) is documented, adding to a distinct diversity maximum at 7 m water depth. A highly condensed photic zonation, due to the high latitude (59°) and eutrophic conditions, is recorded by the measurement of the Photosynthetically Active Radiation (PAR) and is confirmed by the bathymetric range of the photic related ichnocoenoses. At 1 m water depth, a mature shallow euphotic ichnocoenosis dominated by cyanobacteria and at 7 m, a deep euphotic ichnocoenosis dominated by chlorophytes, respectively, is developed after as little as 12 months exposure. With the vanishing light availability from 15 m downwards, the ichnocoenoses development is significantly slowed and only immature dysphotic and aphotic borer communities (dominated by fungi) are encountered. Strong fluctuations of salinity (down to 8%) and temperature (0–20°C) in the euphotic zone indicate most phototrophs present to be considerably euryhaline and eurytherm, while most endolithic fungi appear preferentially in the deeper, more stable marine waters.     

Hettangian (Early Jurassic) Dinosaur Tracksites from the Mecsek Mountains,Hungary

A rare example of a North American Jurassic hardground is found in the Carmel Formation of southwestern Utah. The Carmel hard‐ground was formed across a carbonate lagoon from an oolitic shoal seaward to a subtidal shelly facies landward. It has an abundant bivalve fauna consisting of thick layers of encrusters (the oyster Liostrea and the plicatulid Plicatula), borers (the ichnofossil Gastro‐chaenolites with the mytilid Lithophaga often preserved inside), and nestlers (the mytilid Modiolus). A rare soft‐bodied bryozoan (Arach‐nidium) is preserved by bioimmuration in the attachment scars of Liostrea; this is the first bioimmuration recorded from the Jurassic of North America, and the first bioimmuration recorded from a hard‐ground. The phoronid boring Talpina is present in some Liostrea shells; it was apparently excavated after the death of these oysters. The Carmel hardground community does not contain other fossils, such as serpulids, brachiopods, foraminiferans, and skeletal bryo‐zoans, typical of Jurassic hardgrounds elsewhere. It represents a low diversity molluscan community developed in a restricted marine environment.