Latitudinal and depth gradients in marine predation pressure

Aim There is a general paradigm that marine predation pressure increases towards the tropics and decreases with depth. However, data demonstrating global trends are generally lacking. Rhynchonelliform brachiopods inhabit all the oceans and often survive shell‐crushing predator attacks. We investigate shell repair in brachiopods across a range of Southern Hemisphere and tropical Northern Hemisphere latitudes and depths. Location The Southern Hemisphere and tropical Northern Hemisphere. Methods We analysed the frequency of shell repair in 112 bulk samples, over 70% of which showed traces of shell damage and repair. Results The pattern of shell repair frequency (RF) was more complicated than the anticipated increase with decreasing latitude, with low levels at both polar and tropical sites but high levels at temperate latitudes. This pattern is only evident, however, in shallow water assemblages; and there is no latitudinal trend in water depths greater than 200 m, where shell RF is systematically low. There was a significant logarithmic relationship between RF and depth. Low polar repair rates reflect reduced predation pressure, directly supporting the global paradigm. Low rates in the tropics appears counter to the paradigm. However, tropical brachiopods are generally very small (micromorphic) in shallow water and below the minimum size at which damage is recorded anywhere. Main conclusions Predation pressure decreased logarithmically with depth. At shallow depths (< 200 m) RF showed its highest levels in the mid temperate latitudes with decreasing frequency towards both the tropics and the poles. Low levels of shell repair at high latitudes are likely to be due to a lack of crushing predators, but in the tropics it is suggested that the low frequency is a result of the small size of tropical brachiopods. We hypothesize that micromorphy in this region may be an outcome of high predation pressure.     

Brachiopod shell thickness links environment and evolution

While it is well established that the shapes and sizes of shells are strongly phylogenetically controlled, little is known about the phylogenetic constraints on shell thickness. Yet, shell thickness is likely to be sensitive to environmental fluctuations and has the potential to illuminate environmental perturbations through deep time. Here we systematically quantify the thickness of the anterior brachiopod shell which protects the filtration chamber and is thus considered functionally homologous across higher taxa of brachiopods. Our data come from 66 genera and 10 different orders and shows well-defined upper and lower boundaries of anterior shell thickness. For Ordovician and Silurian brachiopods we find significant order-level differences and a trend of increasing shell thickness with water depth. Modern (Cenozoic) brachiopods, by comparison, fall into the lower half of observed shell thicknesses. Among Ordovician–Silurian brachiopods, older stocks commonly have thicker shells, and thick-shelled taxa contributed more prominently to the Great Ordovician Biodiversification but suffered more severely during the Late Ordovician Mass Extinction. Our data highlight a significant reduction in maximum and minimum shell thickness following the Late Ordovician mass extinction. This points towards stronger selection pressure for energy-efficient shell secretion during times of crisis.     

Mechanical strength of shells of selected extant articulate brachiopods: Implications for paleozoic morphologic trends

Dried shells of Terebratalia transversa, Laqueus californianus, Hemithyris psittacea, and T. unguicula and alcohol‐soaked, tissue‐lined shells of Terebratulina retusa, Dallina septigera, Cryphus vitreus, and Liothyrella uva were crushed in an apparatus that facilitated measurement of the force (newtons) against the valves at the instant of fracture. The results revealed that the costate shells of T. transversa and T. retusa were the strongest. Force is correlated with valve thickness, but not with size (length). When normalized for valve thickness, the force required to fracture shells is correlated with shell biconvexity (height/length) among pooled species of dried specimens. Geniculate specimens of T. retusa were not stronger than the intraspecific variants with a constant radius of curvature to their valves.

The percent‐frequency of plicate, spinose, lamellose and rugate genera increase significantly in the successive stages, Caradocian (Late Ordovician) through Famennian (Late Devonian) at the expense of smooth to costellate genera. The percent‐frequency of rectimarginate (central fold lacking) genera also decreases appreciably in this time frame. These morphologic trends, in combination with the experimental crushing data, support the hypothesis that selection favored species with such anti‐predatory adaptations during a time of escalation of shell‐crushing predators.     

STROPHOMENIDE BRACHIOPODS FROM THE CHANGWU FORMATION (LATE KATIAN, LATE ORDOVICIAN) OF CHUN'AN, WESTERN ZHEJIANG, SOUTH-EAST CHINA

Abstract:  Late Ordovician strophomenide brachiopods (superfamilies Strophomenoidea and Plectambonitoidea) from the upper Changwu Formation (mid Ashgill, late Katian) of Jianglütang, Chun'an County, western Zhejiang Province, consist of ten genera and 12 species. Five new species of three new genera are recognized: Chunanomena triporcata , Chunanomena sembellina , Cheramomena subsolana , Lateriseptomena modesta , and Lateriseptomena rugosa . The strophomenide brachiopods from the upper Katian strata described in this study and those from the border region of Zhejiang and Jiangxi provinces reported in previous work contain 16 strophomenoid and 12 plectambonitoid genera, and most of the strophomenoids are endemic to South China. Numerical analysis of well-documented late Katian strophomenide brachiopod faunas indicates a strong provincialism, characterized by the highly distinct North American province (Laurentia), the South China-Kazakhstan province, and the Avalonia-Baltica province (Wales, Belgium and Sweden). Surprisingly, the Girvan district of Scotland, which was a peri-Laurentian terrane during the Ordovician, contains a late Katian brachiopod fauna that is more closely related to the contemporaneous brachiopods of Avalonia-Baltica than to those of North America.     

MORPHOLOGY AND BEHAVIOR OF CRABS AND GASTROPODS FROM LAKE TANGANYIKA,AFRICA: IMPLICATIONS FOR LACUSTRINE PREDATOR-PREY COEVOLUTION

The shells of most lacustrine gastropods are typically small, weakly calcified, and modestly ornamented to unornamented. Similarly, most lacustrine crabs are usually small detritivores with weak chelae. A number of invertebrate taxa in Lake Tanganyika, however, deviate from these generalities. This study explores a predator-prey coevolution model as an explanation for the large, heavily calcified, and ornate gastropods and the robust, durophagous crabs of Lake Tanganyika. The endemic thiarid and viviparid gastropods from Lake Tanganyika have significantly thicker shells and higher frequencies of terminal apertural lip thickening than closely related cosmopolitan taxa from outside the lake. Tanganyikan gastropods also display considerably higher incidence of shell repair, following nonlethal shell damage, than cosmopolitan taxa of the same families. There is a strong positive correlation between gastropod apertural lip thickness and shell repair frequency among all the gastropod species analyzed. The endemic Tanganyikan potamonautid crab Platytelphusa armata (a molluscivore) possesses larger, more robust crushing chelae than other African potamonautid or potamonid crabs. In contrast with the cosmopolitan African crabs, the Tanganyikan crabs display molariform, rather than serrate dentition on their crushing chelipeds. In shell-crushing experiments, the Tanganyikan gastropod shells were an order of magnitude stronger than typical lacustrine gastropod shells, many well within the range of tropical marine gastropod shell strengths. Predation experiments with the endemic gastropods Spekia, Neothauma, Lavigeria spp., Paramelania spp. and the crab Platytelphusa armata showed that increased size, apertural lip thickness or shell sculpture reduced the successful predation rate of P. armata. Crabs with large chelae have a greater ratio of successful: unsuccessful attacks than crabs with small chelae. Among cases of successful predation, crabs with large chelae employed predation methods that required less time and energy (such as crushing the shell in the cheliped) than the methods employed by crabs with small chelae (such as peeling the shell from the aperture or the spire). The morphological, shell-crushing, and aquarium experiment data, considered in concert, provide strong support for the idea that the endemic gastropods and crabs of Lake Tanganyika have coevolved over the past 7 million years.     

Did the Late Ordovician mass extinction event trigger the earliest evolution of ‘strophodontoid’ brachiopods?

‘Strophodontoid’ brachiopods represented the majority of strophomenide brachiopods in the Silurian and Devonian periods. They are characterized by denticles developed along the hinge line. The evolution of denticles correlated with the disappearance of dental plates and teeth and were already present when the clade originated in the Late Ordovician. Specimens of Eostropheodonta parvicostellata from the Kuanyinchiao Bed (early–middle Hirnantian, uppermost Ordovician) in the Hetaoba Section, Meitan, Guizhou Province, South China, display clear fossil population variation, during a process of loss of dental plates and the development of denticles. Three phenotypes of E. parvicostellata are recognized in a single fossil bed, likely heralding a speciation process. Non-metric multidimensional scaling (NMDS) based on five key characters of genera of the Family Leptostrophiidae shows a much wider morphospace for Silurian genera than for those in the Devonian. Phylogenetic analysis of the Family Leptostrophiidae supports the NMDS analysis and mostly tracks their geological history. The fossil population differentiation in E. parvicostellata discovered between the two phases of the Late Ordovician mass extinction event (LOME) linked to a major glaciation, suggests a Hirnantian origination of the ‘strophodontoid’ morphology, and links microevolutionary change to a macroevolutionary event.     

The origin and geometry of radial ribbing patterns in articulate brachiopods

Ackerly, S. C. 1992 07 15: The origin and geometry of radial ribbing patterns in articulate brachiopods.
Geometric models for simple. radial ribbing in articulate brachiopods include (1) ribs radiating isometrically from the shell umbo. (2) divergence of thc ribs from some 'point' within the shell, and (3) reorientation of the ribs at right angles to the shell margin. Analyses of the Orthida, the ancestral taxon of articulate brachiopods, indicate that rib geometries are isometric in Early Cambrian taxa (model 1). but that by the Early Ordovician rib orientations are generally perpendicular to the shell margin (model 3). A combination of functional and morphogenetic Factors explains the ribbing geometries observed in orthide brachiopods.     

Structure of the first-formed shell of the Middle Ordovician orthid-like brachiopods from the Leningrad Region

Shell structure of the first-formed shell of the Middle Ordovician orthid-like brachiopods from the Leningrad Region is described. The 190-μm-wide first-formed shell is composed of finely granular layer while 700-μm-wide first-formed shell is fibrous. Thus the order Orthida in the Early Paleozoic included brachiopods with both planktotrophic and lecithotrophic larvae in the ontogeny.     

Epithelial moulds from some Upper Ordovician acrotretide brachiopods of Ireland

Three new genera of acrotretid brachiopods are of general morphological interest in that they display polygonal mosaics on the internal shell surfaces, features which are believed to be moulds of the outer epithelial cells. The mosaic is further noted in a specimen of Eoconulus , a form which may also belong to the Acrotretacea. Such mosaics have not previously been recorded from the Acrotretacea. Polygonal mosaics, epithelial moulds, outer epithelium , Eoconulus, Acrotretacea, Ordovician.     

Constraining functional hypotheses: controls on the morphology of the concavo-convex brachiopod Rafinesquina

The concavo-convex shape of strophomenoid brachiopods has been inferred to be adaptive to a free-lying state. Such functional hypotheses should be constrained by identifying the factors controlling morphology. A typical strophomenoid, Rafinesquina alternata, is used here to study morphological influences. Specimens of R. alternata were collected from ten localities in Indiana, USA. Beds are Upper Ordovician (Richmondian) mudstones and limestones of the Dillsboro and Whitewater Formations. Length and hingeline width of the pedicle valve were measured, and elongation (length divided by width) calculated for each specimen. Specimens were qualitatively identified as geniculate or arcuate. Regression analyses using stratigraphy (time), mudstone percentage (substrate), grainstone percentage (disturbance), ratio of Strophomena planumbona to R. alternata (competition), and length (ontogeny) as independent variables, were performed to determine the factors influencing morphology. Elongation was most strongly influenced by grainstone percentage and the S. planumbona ratio. Populations of R. alternata from grainstonerich intervals are less elongate than other samples. The lateral margins of transverse R. alternata may have functioned as sediment traps during periods of high turbidity. Alternatively, variation in elongation may be a character displacement due to interspecific competition with the related S. planumbona, which is inferred to have had a similar life mode. R. alternata specimens found in beds dominated by S. planumbona are more elongate than R. alternata from beds in which S. planumbona is rare or absent. Geniculation was influenced by stratigraphic position, suggesting an evolutionary trend, and by limestone percentage. Geniculate individuals are most common in muddier intervals, supporting the hypothesis that geniculation enabled R. alternata to employ an ‘iceberg’ strategy, ‘floating’ convex down on the soft muds. The habitat distribution of R. alternata is inconsistent with the hypothesis that concavo-convex brachiopods lived convex-valve-up, as suggested by Lescinsky (1995). Both elongation and geniculation may be examples of phenotypic plasticity.     

Influence of valve geometry, ornamentation, and microstructure on fractures in Late Ordovician brachiopods

Among Late Ordovician brachiopods from southeastern Indiana. strophomenids display a ratio of 4:1 parabolic to linear repaired fractures in contrast to the 1:2 ratio found for orthids and rhynchonellids. Additionally, only strophomenids display repaired elliptical fractures. The weakest parts of strophomenid and orthid-rhynchonellid shells are the regions of the adductor muscle scars and the sulcus, respectively. Fractured biplanate shells of strophomenids are commonly cleaved anteriorly to posteriorly, whereas fractures are localized on the anterior of strongly curved to geniculate conspecific specimens. Rugae on leptaenids, thickened anterior margins of the brachial valve of rafinesquinids, and the dense distribution of pseudopunctate in all strophomenids, functioned to localize anteriorly the (un)repaired linear and parabolic fractures. No sublethal fracture occurs on any biconvex shell where the height is greater than 14 mm, despite the fact that numerous specimens of certain species attained shell heights of 20 mm or more, an observation suggesting the upper limit in the gape of the crushing elements of the predator. Crushing experiments on valve 'models' reveal that the inflated equibiconvex, plicate shape of the shells of Plarysfrophia is the strongest. However, the architecture of the concave strophomenid valves is relatively stronger than the corresponding valves of many orthids and rhynchonellids when normalized for valve thickness.     

The earliest known strophomenoids (Brachiopoda) from early Middle Ordovician rocks Of South China

The upper Daguanshan Formation (middle Expansograptus hirundo graptolite biozone, Dapingian, early Middle Ordovician) of the Shuanghe area, Changning County, southern Sichuan Province, contains three new genera and species of strophomenoids: Ochyromena plana, Shuangheella elongata, and Primotimena globula, which are attributed to the Strophomenidae, Rafinesquinidae and Glyptomenidae respectively. These are the earliest known strophomenoids from the South China palaeoplate, and also the oldest rafinesquinid and glyptomenid brachiopods worldwide. Global review of the superfamily Strophomenoidea of Middle Ordovician age suggests that the first diversity peak at the species level occurred in late Darriwilian (Llanvirn) time, mainly as a result of the rapid diversification of the family Strophomenidae. The first appearance datum (FAD) of strophomenoids and their possible westward dispersal were from North China (latest Floian) and/or South China (early Dapingian), through the Chu‐Ili terrane of Kazakhstan, Iran, and Baltica (early Darriwilian), to Avalonia and Laurentia (late Darriwilian). This points to the existence of early diversification hotspots of the strophomenoid superfamily in the North and South China palaeoplates during the early Middle Ordovician in generally shallow water (corresponding to BA2) environments. The high degree of similarity in the external morphology and ventral interior of the three new genera indicates that the early diversification of strophomenoids began with differentiation of the cardinalia, especially in the configuration of the bilobed cardinal process, a key evolutionary novelty for the strophomenoids.     

Tuning in to multiple predators: conflicting demands for shell morphology in a freshwater snail

1. We examined the response to chemical cues from fish and crayfish, two predators with contrasting feeding modes, and their single and combined effect on shell morphology in the freshwater snail Radix balthica. 2. Snails were subjected to four treatments: tench (Tinca tinca), signal crayfish (Pacifastacus leniusculus), a combination of tench and signal crayfish and no predators (control). Shell shape, crushing resistance and shell thickness were quantified. We also analysed whether shape or shell thickness contributes most to crushing resistance. 3. Chemical cues from the fish induced a rounder shell shape in R. balthica, a thicker shell and a higher crushing resistance, whereas crayfish chemical cues had no effect on shell morphology, shell thickness or crushing resistance. Shell shape contributed more to crushing resistance than shell thickness. 4. The combined predator treatment showed an intermediate response between the fish and crayfish treatments. Shell roundness was reduced compared with the fish treatment, but the reduced crushing resistance that comes with a less rounded shell was compensated by an increased investment in extra shell material, exceeding that of the fish treatment. 5. Our study extends previous studies of multipredator effects on phenotypically plastic freshwater snails by showing that the snails are able to fine‐tune different elements of morphology to counter predator‐specific foraging modes.     

Traces of predation/parasitism recorded in Eocene brachiopods from the Castle Hayne Limestone,North Carolina,USA

Schimmel, M., Kowalewski, M. & Coffey, BP. 2011: Traces of predation/parasitism recorded in Eocene brachiopods from the Castle Hayne Limestone, North Carolina, USA. Lethaia, Vol. 45, pp. 274–289. The Castle Hayne Limestone (Middle Eocene, North Carolina), noted for its diverse macro‐invertebrate fossils, was sampled to assess if Early Cenozoic brachiopods from eastern North America record any traces of biotic interactions. Systematic surveys of two North Carolina quarries yielded 494 brachiopods dominated by one species: Plicatoria wilmingtonensis (Lyell and Sowerby, 1845). Despite subtle variations in taphonomy, taxonomy and drilling patterns, the two sampled quarries are remarkably similar in terms of quantitative and qualitative palaeoecological and taphonomic patterns. In both quarries, brachiopods contain frequent drillholes (24.5% specimens drilled). The majority of drillholes were singular, perpendicular to shell surface and drilled from the outside. Ventral valves were drilled slightly more frequently than dorsal ones, but site‐selectivity in drilhole location was not evident. Larger brachiopods were drilled significantly more frequently than smaller ones. However, drillhole diameter did not correlate with brachiopod size. The drillholes are interpreted as records of ‘live‐live’ biotic interactions, representing either predatory attacks or parasitic infestations or a combination of those two types of interactions. A notable fraction of specimens bear multiple drillholes, which is consistent with either parasitic nature of interactions or frequent failed predatory events. The high drilling frequency reported here reinforces other reports (from other continents and other epochs of the Cenozoic), which suggest that brachiopods may be an important prey or host of drilling organisms in some settings. The number of case studies reporting high frequencies of drilling in brachiopods is still limited and thus insufficient to draw reliable generalizations regarding the causes and consequences of these occasionally intense ecological interactions. □Brachiopods, drilling parasitism, drilling predation, Eocene, North Carolina, taphonomy.     

Predation in the Ordovician and Silurian of Baltica

Signs of predation appear in the Middle Ordovician of Baltica. Shell repair dominates over the predatory borings in the Ordovician and Silurian. Predators attacked molluscs, brachiopods and tentaculitoids in the Ordovician and molluscs, tentaculitoids, brachiopods and ostracods in the Silurian. There is an increase in the number of prey species in the Late Ordovician, which could be related to the Great Ordovician Biodiversification Event. Molluscs are the favourite prey taxon in the Ordovician, but in the Silurian, molluscs became less dominant as the prey. This is probably not an artefact of preservation as Ordovician and Silurian molluscs are equally well preserved.     

Shell structure and affinities of the enigmatic Lower Ordovician articulate brachiopod Lycophoria Lahusen, 1886

Wright, A. D. 1992 04 15: Shell structure and affinities of the enigmatic Lower Ordovician articulate brachiopod Lycophoria Lahusen. 1886. Lethaia . Vol. 25, pp. 125–129. Oslo. ISSN 0024–1164.
The enigmatic Baltoscandian Lower Ordovician brachiopod Lycophoriu has a combination of morphological characters that makes it difficult to place taxonomically. The more recent assignments of the genus have been with the Porambonitacea, the Triplesiacea and the Orthacea. A basic character in articulate brachiopods is the differentiation of the secondary shell into either stacked fibres or laminar sheets. The hitherto unknown shell structure in Lycophoria has been examined under the electron microscope and is shown to be fibrous, which is taken as ruling out any close affinity with the lamellar shelled Triplesiacea. Despite superficial similarities, features of the shell interior are not compatible with the pentameride Porambonitacea and although there are differences from the typical orthacean, these are no greater than those of the accepted orthid Producrorrhis. Lycophoria , in the monotypic family Lycophoriidae, is accordingly best regarded as a specialized offshoot of the basic orthacean stock. * Shell microstructure, Lycophoridae, Orrhacea, Porambonitacea, Triplesiacea, Lower Ordovician, Baltoscandia .     

Epizoans on late Ordovician brachiopods from Southeastern Indiana

The frequency of epizoans (cornulitids, inarticulate brachiopods, bryozoans, solitary and colonial rugosan corals) on over 8000 specimens of articulate brachiopods (four strophomenids, five orthids, one rhynchonellid) was calculated for four stratigraphic horizons in the Dillsboro Formation of southeastern Indiana. Frequency of shells encrusted correlates significantly with the surface area of the valves. Punctae in brachiopod shells (Onniella meeki) may have deterred larval settlement of epizoans. Coarse ribbing on articulates deterred encrustation by the inarticulate brachiopod. The horn coral shows a preference for attachment to the anterior of Hiscobeccus capax. Bryozoans show a preference for the incurrent lateral margins of inferred living hosts, suggesting rheotropic behavior by settling larvae. Inarticulate brachiopods are concentrated around the sloping commissure of the brachial valve of strophomenids, suggesting geotropic behavior and/or selective survival of settling larvae. Inarticulates deterred overgrowth by bryozoans. High frequencies of encrustations of the medial region of pedicle valves of orthids and strophomenids probably reflect post‐mortem encrustations. Alternating intervals of slow sediment accumulation punctuated by tropical storms and rapid shell burial may account for the high frequency of shells with either their entire surface veneered or only a very small area encrusted by bryozoans.     

An early Ordovician patelliform gastropod, Palaelophacmaea, reinterpreted as a coelenterate

Yochelson, Ellis L. & Stanley, George D., Jr. 1981 12 15: An early Ordovician patelliform gastropod, Palaelophacmaea , reinterpreted as a coelenterate. Lethaia , Vol. 15, pp. 323–330. Oslo. ISSN W24–1164.
The fossil Palaelophacmaea criola Donaldson, from the early Ordovician Stonehenge Formation of central Pennsylvania, was described as a patelliform gastropod. A reinterpretation of the type lot and study of a few additional specimens provide the basis for an alternative placement. Palaelophacmaea is here assigned to the Hydrozoa, as a possible chondrophore. It has an exceptionally thin shell or test and concentric but irregular corrugations. Cambrian univalve genera having a more or less circular outline that are currently assigned to the Gastropoda or Monoplacophora should be reexamined to see whether they have the features of fossil chondrophore coelenterates rather than those of molluscs. The late Cambrian Palaeoacmaea Hall & Whitfield is removed from the monoplacophoran Mollusca and left unassigned as to phylum. We judge that at least some early Cambrian species of Scenella are probably coelenterate remains. * Early Ordovician , Palaelophacmaea, Gastropoda, Monoplacophora, Hydrozoa .     

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.