Predatory shell drilling by two species of Austroginella (Gastropoda: Marginellidae)

Predatory shell drilling of bivalve mollusc shells is reported for the gastropods Austroginella johnstoni and A. muscaria from south-eastern Australia. This is the first record of this feeding behaviour in the family Marginellidae. The drill holes are circular and paraboloid, with a small inner penetration hole. The corroded nature of the aragonite crystals within the drill holes suggests a chemical dissolution drilling mechanism. No obvious accessory boring organ was located. The gastropods have subepithelial gland cells in the proboscis, a pair of small salivary glands and a large foregut gland. The latter has a duct bypassing the valve of Leiblein and joining the anterior oesophagus.     

The salivary papilla of Octopus as an accessory radula for drilling shells

Removal of much of the functional region of the radula of Octopus vulgaris does not prevent the animal from drilling holes in mollusc shells. These drilling activities are carried out by a salivary papilla that lies just below the radula. The papilla is muscular and its anterior face is covered with very small teeth. It is now possible to say that the salivary papilla can function as an accessory radula.     

Has Octopus vulgaris a second radula?

Octopus vulgaris drills shelled molluscs and measurements showed the radula to be too large to reach into the depths of the holes made. Small teeth were found on the salivary papilla and its seems likely that these are used for excavating the deeper parts of the holes and penetration of the shell.     

Drill Holes and Predation Traces versus Abrasion-Induced Artifacts Revealed by Tumbling Experiments

Drill holes made by predators in prey shells are widely considered to be the most unambiguous bodies of evidence of predator-prey interactions in the fossil record. However, recognition of traces of predatory origin from those formed by abiotic factors still waits for a rigorous evaluation as a prerequisite to ascertain predation intensity through geologic time and to test macroevolutionary patterns. New experimental data from tumbling various extant shells demonstrate that abrasion may leave holes strongly resembling the traces produced by drilling predators. They typically represent singular, circular to oval penetrations perpendicular to the shell surface. These data provide an alternative explanation to the drilling predation hypothesis for the origin of holes recorded in fossil shells. Although various non-morphological criteria (evaluation of holes for non-random distribution) and morphometric studies (quantification of the drill hole shape) have been employed to separate biological from abiotic traces, these are probably insufficient to exclude abrasion artifacts, consequently leading to overestimate predation intensity. As a result, from now on, we must adopt more rigorous criteria to appropriately distinguish abrasion artifacts from drill holes, such as microstructural identification of micro-rasping traces.     

Stereotypic and size-selective predation in Polinices pulchellus (Gastropoda: Naticidae) Risso 1826

Polinices pulchellus were size-selective in their choice of Cerastoderma edule. Large predators (12-15.9 mm shell length) selected both larger and a wider size range of cockles than smaller individuals (4-11.9 mm shell length). Considerable overlap occurred in the sizes of cockles frequently drilled by different size classes of snails, indicating that certain sizes of cockles may be most profitable to a wide range of predator sizes. Consumption rates were highest during July and August and were closely related to seawater temperature. Inner and outer drill hole diameters were both correlated with predator size, and the morphology of the drill hole was geometrically similar across a range of predator sizes. Polinices pulchellus showed no preference for either the left or right valve and drilled most cockles in the centre of the shell valve. The relationship between the distance of the drill hole from the umbo and prey size was unaffected by predator size, such that predators of different sizes were not found to drill cockles in different positions. When disturbed during drilling, incomplete drill holes were abandoned and, when drilling resumed, it occurred in new locations on the surface of the shell valve. The findings of this study highlight the stereotyped nature of drilling behaviour seen in the family Naticidae.     

Survival and repair of surgical and natural shell damage in the articulate brachiopod Terebratulina retusa (Linnaeus)

Living specimens of Terebratulina retusa from the Firth of Lorn, Scotland, were surgically damaged by drilling 2 mm diameter holes or narrow slits one cm long in the anterior portion of one valve, by bevelling the anterior margin of both valves, or by amputation of the anterior third of one valve. These injuries to the shell and mantle simulated the type of repaired shell damage seen in Paleozoic species, i.e., scalloped, divoted, cleft, and embayed valves. Less than ten percent of the 200 damaged specimens survived until the 25th week after surgery. Specimens of T. retusa showed the ability to repair drill holes, slits, and bevelled anterior shell regions, but not the most severe damage, i.e., amputations of the anterior third of one valve. Shell‐repair was initiated in the fourth week after surgery by the development of a membrane across the wound. The development of caeca in the new shell layer secreted to plug the drill holes became apparent by the eighth week. The punctate pattern was complete in the new, translucent shell material of bevelled and drilled specimens by the 25th week following surgery. Failure of any specimens to survive amputation of the anterior portion of a valve for more than seven weeks after surgery, and the absence of initiation of the repair process, suggests that terebratulids do not have the tolerance for, nor the ability to repair, the severe injuries (embayed valves) which were sustained and mended by extinct strophomenids.     

Intense drilling in the Carboniferous brachiopod Cardiarina cordata Cooper, 1956

The brachiopod Cardiarina cordata, collected from a Late Pennsylvanian (Virgilian) limestone unit in Grapevine Canyon (Sacramento Mts., New Mexico), reveals frequent drillings: 32.7% (n = 400) of these small, invariably articulated specimens (<2 mm size) display small (<0.2 mm), round often beveled holes that are typically single and penetrate one valve of an articulated shell. The observed drilling frequency is comparable with frequencies observed in the Late Mesozoic and Cenozoic. The drilling organism displayed high valve and site selectivity, although the exact nature of the biotic interaction recorded by drill holes (parasitism vs. predation) cannot be established. In addition, prey/host size may have been an important factor in the selection of prey/host taxa by the predator/parasite. These results suggest that drilling interactions occasionally occurred at high (Cenozoic-like) frequencies in the Paleozoic. However, such anomalously high frequencies may have been restricted to small prey/host with small drill holes. Small drillings in C. cordata, and other Paleozoic brachiopods, may record a different guild of predators/parasites than the larger, but less common, drill holes previously documented for Paleozoic brachiopods, echinoderms, and mollusks.     

Initial predation and parasitism by muricid whelks demonstrated by the correspondence between drilled holes and their apparent enveloper

The morphologies of drilled holes enveloped by three coexisting muricid whelks, Morula musiva, Cronia margariticola and Ergalatax contractus, were compared. The results were used to demonstrate the replacement of feeders using drilled holes, and to estimate the frequency of this occurrence in the field. In the laboratory, M. musiva made circular internal holes, whereas C. margariticola and E. contractus made oval holes, when they preyed upon the mussel Hormomya mutabilis. The maximum inner diameter of the hole correlated with the driller's shell height in all three muricid species. In the field, mussels enveloped by M. musiva had circular drilled holes, as was found in the laboratory, and the correlation between maximum diameter and enveloper's shell height was not significantly different from that found in the laboratory. In contrast, holes enveloped by C. margariticola in the field were more circular than those observed in the laboratory, and there was no correlation between maximum diameter and enveloper's shell height. Statistical analyses of these results indicated that more than half of the mussels being ingested by C. margariticola had been drilled by M. musiva, i.e. C. margariticola would often kleptoparasitize or scavenge M. musiva's prey by taking over the drilled hole. Few M. musiva would take over the holes drilled by C. margariticola or E. contractus. Furthermore, probably few M. musiva would take over the hole made by a conspecific initial drilling predator. It appears that E. contractus rarely initiates predation by drilling.     

Drilling by Octopus vulgaris(Mollusca: Cephalopoda) in the Mediterranean

Octopus vulgaris drills holes in the shells of a variety of molluscs. The walls of the cavities drilled exhibit dissolution of mineral and organic material. The features which characterize the cavities have been described. The composition and structure of the shell itself is important in determining the size, shape and form of the cavity drilled, and not the size of the octopus. Capture, drilling the shell, and eating the occupant may take less than one hour.     

Comparing predatory drillholes to taphonomic damage from simulated wave action on a modern gastropod

Marine drilling predation, in which the predator bores a hole through shelled invertebrate prey, plays a role in the structure of benthic communities. As drilling often leaves the prey shell otherwise undamaged, the resulting holes are also an excellent proxy for drilling predation pressure in the fossil record. Considering that a large number of predation studies focus on drilling predation in the fossil record, it is crucial that we are able to distinguish true drilling predation from taphonomy. The purpose of this study is to determine damage on Olivella biplicata shells, drilled by naticid gastropods, is distinguishable from taphonomically produced damage to these shells. In addition, the potential for preferential breakage due to either the presence or whether absence of a drillhole was investigated. Drilled and non-drilled O. biplicata shells were tumbled to simulate wave action and were checked at intervals to record accumulated damage. Drilled and non-drilled shells do not show a significant difference in damage accumulated while undergoing simulated wave action. Taphonomic damage is unlikely to be mistaken for drilling damage, due to the jagged, irregular appearance of taphonomically produced holes.     

Reappraising the early evidence of durophagy and drilling predation in the fossil record: implications for escalation and the Cambrian Explosion

The Cambrian Explosion is arguably the most extreme example of a biological radiation preserved in the fossil record, and studies of Cambrian Lagerstätten have facilitated the exploration of many facets of this key evolutionary event. As predation was a major ecological driver behind the Explosion – particularly the radiation of biomineralising metazoans – the evidence for shell crushing (durophagy), drilling and puncturing predation in the Cambrian (and possibly the Ediacaran) is considered. Examples of durophagous predation on biomineralised taxa other than trilobites are apparently rare, reflecting predator preference, taphonomic and sampling biases, or simply lack of documentation. The oldest known example of durophagy is shell damage on the problematic taxon Mobergella holsti from the early Cambrian (possibly Terreneuvian) of Sweden. Using functional morphology to identify (or perhaps misidentify) durophagous predators is discussed, with emphasis on the toolkit used by Cambrian arthropods, specifically the radiodontan oral cone and the frontal and gnathobasic appendages of various taxa. Records of drill holes and possible puncture holes in Cambrian shells are mostly on brachiopods, but the lack of prey diversity may represent either a true biological signal or a result of various biases. The oldest drilled Cambrian shells occur in a variety of Terreneuvian‐aged taxa, but specimens of the ubiquitous Ediacaran shelly fossil Cloudina also show putative drilling traces. Knowledge on Cambrian shell drillers is sorely lacking and there is little evidence or consensus concerning the taxonomic groups that made the holes, which often leads to the suggestion of an unknown ‘soft bodied driller’. Useful methodologies for deciphering the identities and capabilities of shell drillers are outlined. Evidence for puncture holes in Cambrian shelly taxa is rare. Such holes are more jagged than drill holes and possibly made by a Cambrian ‘puncher’. The Cambrian arthropod Yohoia may have used its frontal appendages in a jack‐knifing manner, similar to Recent stomatopod crustaceans, to strike and puncture shells rapidly. Finally, Cambrian durophagous and shell‐drilling predation is considered in the context of escalation – an evolutionary process that, amongst other scenarios, involves predators (and other ‘enemies’) as the predominant agents of natural selection. The rapid increase in diversity and abundance of biomineralised shells during the early Cambrian is often attributed to escalation: enemies placed selective pressure on prey, forcing phenotypic responses in prey and, by extension, in predator groups over time. Unfortunately, few case studies illustrate long‐term patterns in shelly fossil morphologies that may reflect the influence of predation throughout the Cambrian. More studies on phenotypic change in hard‐shelled lineages are needed to convincingly illustrate escalation and the responses of prey during the Cambrian.     

Three-dimensional structure of rhesus rotavirus by cryoelectron microscopy and image reconstruction

The structure of rhesus rotavirus was examined by cryoelectron microscopy and image analysis. Three-dimensional reconstructions of infectious virions were computed at 26- and 37-A resolution from electron micrographs recorded at two different levels of defocus. The major features revealed by the reconstructions are (a) both outer and inner capsids are constructed with T = 13l icosahedral lattice symmetry; (b) 60 spikelike projections, attributed to VP4, extend at least 100 A from the outer capsid surface; (c) the outer capsid, attributed primarily to VP7, has a smoothly rippled surface at a mean radius of 377 A and is perforated by 132 aqueous holes ranging from 40-65 A in diameter; (d) the inner capsid has a "bristled" outer surface composed of 260 trimeric-shaped columns of density, attributed to VP6, which merge with a smooth, spherical shell of density at a lower, mean radius of 299 A, and which is perforated by holes in register with those in the outer capsid; (e) a "core" region contains a third, nonspherical shell of density at a mean radius of 225 A that encapsidates the double-stranded RNA genome; and (f) the space between the outer and inner capsids forms an open aqueous network that may provide pathways for the diffusion of ions and small regulatory molecules as well as the extrusion of RNA. The assignment of different viral structural proteins to specific features of the reconstruction has been tentatively made on the basis of excluded volume estimates and previous biochemical characterizations of rotavirus.     

Characterization of boreholes by Octopus dofleini in the bivalve Saxidomus giganteus

Octopus dofleini (Wulker) drills holes in mollusc shells, enabling it to introduce venom. Boreholes in the bivalve Saxidomus giganteus (Deshayes) were generally irregular. Thick shells were more likely to have incomplete boreholes, and the diameter of completed boreholes was larger than in thin shells. A comparison of boreholes to fractured and artificially drilled surfaces suggests that O. dofleini employs chemical dissolution of the shell during drilling.     

Do predatory drill holes influence the transport and deposition of gastropod shells?

Predatory gastropod drill holes are an abundant and easily identifiable signal of predation in ancient and modern molluscan shell assemblages. Many workers have used drill holes to interpret patterns of predation intensity and success in fossil assemblages. These studies are predicated on the assumption that the relative abundances of drilled and undrilled shells in an assemblage accurately reflect those of the community from which the shells were originally derived. The underlying assumption is that drilled and undrilled shells are transported into shell accumulations in the same manner. If this assumption is false, shell accumulations do not represent taphonomically unbiased samples, but rather preferentially sorted deposits from which conclusions about drilling predation cannot be made. To test the hypothesis that drilled and undrilled gastropod shells transport at different flow velocities, multiple transport trials were conducted on two morphologically distinct taxa, Olivella biplicata and Euspira lewisii. Individual specimens were placed in a recirculating flume tank and observed from rest (in stable orientation) until they were transported downstream. During each trial, flow velocity was slowly and incrementally increased, so as to avoid pulses of acceleration, until shells began to move downstream. Drilled and undrilled specimens of both taxa demonstrate statistically significant correlations between shell mass and average transport velocity. Similarly sized drilled and undrilled specimens of both taxa do not exhibit significant differences in transport velocity. These results indicate that predatory drill holes do not change the hydrodynamic properties of gastropod shells. Therefore, gastropod shell assemblages are not likely to be affected by differential transport and sorting of drilled and undrilled shells.     

The three-dimensional structure of reovirus obtained by cryo-electron microscopy.

The structures of reovirus serotypes T2J (Jones), T3D (Dearing) and the T3D core particle have been determined by cryo-electron microscopy and image processing. At a resolution of 30 A the two serotypes have similar features. The core is visible within the virus structure. The outer surface of the virus particles contains 120 holes at T = 13.1 local 6-fold axes. The holes penetrate into the virus as far as the surface of the internal core shell. Protrusions extending 4 nm from the virus surface surround each hole on the outside of the virus. At the 5-fold axes on the surface of the virus flat 'penton craters' form covers over the underlying core spikes. The detailed structure of the reovirus shell is very different to that of rotavirus although both have holes at T = 13.1 axes. Little evidence was seen of reovirus fibres extending from the virus surface.     

Characteristics of the lymphoid tissue reaction in compensatory reparative growth of the salivary glands in mice]

The capacity of the spleen cells of CBA mice to antibody formation as well as to the "graft-versus-host" (GVH) reaction and the change in the stem cell number determined by the spleen colony method were studied after unilateral removal or burn of the submandibular salivary gland and amputation of lower incisors. It is shown that any of these experimental changes in the salivary gland state causes an increase in the stem cell migration and makes lymphocytes more active in inducing the GVH reaction. The ability of spleen lymphocytes to react on additional antigen stimuli increases after amputation of lower incisors, accompanied by an enlargement of salivary glands, and sharply decreases after the removal or burn of the submandibular salivary gland, not causing hypertrophy of salivary glands.     

Assisted fertilization by zona drilling: a mouse model for correction of oligospermia

A micromanipulation apparatus was used to produce holes in the zonae pellucidae of unfertilized mouse oocytes. A microneedle loaded with acid Tyrode's solution was brought into contact with the zona surface, and positive flow was used in conjunction with mechanical pressure to cause a localized dissolution of the zona. Treated eggs were then fertilized in vitro in comparison with control cells. The zona drilling procedure decreased the sperm count required to achieve fertilization by a factor of approximately 100. The rate of polyspermy in zona-drilled oocytes was not greater than in controls, and oocytes fertilized after drilling, when implanted into pseudopregnant foster females, developed to term at the same rate as controls. The results demonstrate that zona drilling is a safe, effective method of increasing the efficiency of fertilization in vitro and may be useful both in agriculture and medicine for conferring fertility upon males with low sperm counts.     

Simulation of initial frontside and backside wear rates in a modular acetabular component with multiple screw holes.

A sliding distance-based finite element formulation was implemented to predict initial wear rates at the front and back surfaces of a commercially available modular polyethylene component during in vitro loading conditions. We found that contact area, contact stress, and wear at the back surface were more sensitive to the liner/shell conformity than the presence of multiple screw holes. Furthermore, backside linear and volumetric wear rates were at least three orders of magnitude less than respective wear estimates at the articulating surface. This discrepancy was primarily attributed to the difference in maximum sliding distances at the articulating surfaces (measured in mm) versus the back surface (measured in microm). This is the first study in which backside wear has been quantified and explicitly compared with frontside wear using clinically relevant metrics established for the articulating surface. The results of this study suggest that with a polished metal shell, the presence of screw holes does not substantially increase abrasive backside wear when compared with the effects of backside nonconformity.     

Hole-drilling in crustaceans by Eledone cirrhosa (Mollusca: Cephalopoda)

Eledone drills holes in the carapace of crustaceans with the tooth-covered salivary complex in conjunction with salivary secretions.     

Configuration of anchorage holes affects fixation of the acetabular component in cemented total hip replacement—a finite element study

Our survey of current practice among UK orthopaedic surgeons shows wide variations in fixation techniques. The aim of this study, is to investigate the effect of drilling different configurations of anchorage holes in the acetabulum on implant stability. To avoid variables that could incur during in vitro testing, we used commercially available COSMOS finite element analysis package to investigate the stress distributions, deformations, and strains on the cement mantle when drilling three large anchorage holes and six smaller ones, with straight and rounded cement pegs. The results, which are in line with our in vitro studies on simulated reconstructed acetabulae, indicate better stability of the acetabular component when three larger holes than six smaller holes are drilled and when the necks of the anchorage holes are rounded. The longevity of total hip replacements could be improved by drilling three large anchorage holes, rather than many smaller ones, as initially proposed by Charnley.