The functional meaning of “prey size” in water snakes (Nerodia fasciata, Colubridae)

The evolutionary success of macrostomatan (enlarged-gape) snakes has been attributed to their ability to consume large prey, in turn made possible by their highly kinetic skulls. However, prey can be “large” in several ways, and we have little insight into which aspects of prey size and shape affect skull function during feeding. We used X-ray videos of broad-banded water snakes (Nerodia fasciata) feeding on both frogs and fish to quantify movements of the jaw elements during prey transport, and of the anterior vertebral column during post-cranial swallowing. In a sample of additional individuals feeding on both frogs and fish, we measured the time and the number of jaw protractions needed to transport prey through the buccal cavity. Prey type (fish vs. frog) did not influence transport kinematics, but did influence transport performance. Furthermore, wider and taller prey induced greater movements of most cranial elements, but wider prey were transported with significantly less anterior vertebral bending. In the performance trials, heavier, shorter, and wider prey took significantly more time and a greater number of jaw protractions to ingest. Thus, the functional challenges involved in prey transport depend not only upon prey mass, but also prey type (fish vs. frog) and prey shape (relative height, width and length), suggesting that from the perspective of a gape-limited predator, the difficulty of prey ingestion depends upon multiple aspects of prey size.     

Aptychen als Kieferelemente der Ammoniten

The jaws of the ammonite generaEleganticeras, Hildoceras, Normannites, Scaphites, Physodoceras, andQuenstedtoceras (ofQuenst. lower jaws only) are described. Lower jaws and aptychi of these genera are shown to be identical. They consist of an inner layer of organic material, which corresponds to the complete anaptychi of liassic ammonites, and an outer layer of calcitic material deposited on both flancs of the lower jaw, giving rise, after decay of the organic layer, to the aptychi. Previously published interpretations of aptychi as opercula or hoods are discussed and rejected. It is concluded that they certainly functioned as jaws or possibly shovel-like devices.     

Aptychi: the myth of the ammonite operculum

Re-examination of ammonite specimens with the aptychus apparently in place closing the aperture has shown that these are accidents of preservation and have been misinterpreted as indicating that aptychi functioned as opercula. There remain no convincing grounds for doubting that aptychi functioned only as lower jaws of ammonites, not as opercula. Chance preservation of exceptional specimens can sometimes be misleading. Ammonoidea, aptychi, anoptychi, functional morphology .     

Double function of aptychi (Ammonoidea) as jaw elements and opercula

Lehmann, U. & Kulicki, C. 1990 10 15: Double function of aptychi (Ammonoidea) as jaw elements and opercula. Lethaia , Vol. 23, pp. 325–331. Oslo. ISSN 0024–1164.
Aptychi are calcitic coverings on the outer surface of organic ammonite lower jaws. They are similar in shape to that of the corresponding ammonite apertures. This observation and additional features of many aptychi are in harmony with their former interpretation as protective opercula. We suggest that they served as opercula in addition to functioning as jaws. The primary function of the lower jaws was thus secondarily extended to that of protective shields when they acquired their calcitic covering, while as lower jaws their importance dwindled to that of a more passive abutment. Phylogenetically, this seems to have started slowly in some anaptychi and became obvious with the first aptychi. ▭ Ammonites, aptychus, operculum, jaw apparatus, evolution, function .     

First direct evidence of ammonoid ovoviviparity

Ammonoids had high evolutionary rates and diversity throughout their entire history and played an important role in the high‐resolution sub‐division of the Mesozoic, but much of their palaeobiology remains unclear, including the brooding habitat. We present our study of the first recorded ammonite embryonic shell clusters preserved with calcified embryonic aptychi in situ within the body chambers of mature macroconch shells of the Early Aptian (Early Cretaceous) ammonite Sinzovia sazonovae. The following support the idea that the clusters are egg masses, which developed inside ammonite body chambers: the absence of post‐embryonic shells and any other fossils in these clusters, the presence of the aptychi in all embryonic shell apertures and peculiarities of adult shells preservation. These facts confirm earlier speculations that at least some ammonoids could have been ovoviviparous and that, like many modern cephalopods, they could have reproduced in mass spawning events. The aptychi of ammonite embryonic shells are observed here for the first time, indicating that they were already formed and calcified before hatching. Our results are fully congruent with the peculiar modes of ammonoid evolution: quick recovery after extinctions, distinct evolutionary rates, pronounced sexual dimorphism and the nearly constant size of embryonic shells through ammonoid history. We assume that adaptation to ovoviviparity may be the reason for the presence of these features in all post‐Middle Devonian ammonoids.     

Size-related changes in cranial morphology affect diet in the catfish Clariallabes longicauda

Within the catfish family Clariidae, species exist with different degrees of jaw adductor hypertrophy. This jaw adductor hypertrophy has been related to bite performance, in turn suggesting a link to dietary specialization. Thus, an increase in the degree of hypertrophy will likely be reflected in an increase in the amount of hard prey in the diet. In the present study, we examine the ontogenetic scaling of cranial structure and diet in a species of catfish with a moderate degree of jaw adductor hypertrophy, Clariallabes longicauda . Additionally, we investigate whether the observed changes in the morphology of the feeding system during growth are linked to changes in diet. The fish examined demonstrate a strong positively allometric growth of the jaw adductors, of head height and of maximal head width, suggesting that larger fish can feed on larger and harder prey. Dietary data confirm these hypotheses and reveal an increase in maximal prey size consumed, the proportion of large prey in the diet, and average prey hardness during ontogeny. Moreover, the observed changes in the proportion of large prey consumed and prey hardness are correlated with an increase in lower jaw width and maximal head width, respectively. An increase in the amount of evasive prey in the diet with fish size is correlated with an increase in hyoid length. In summary, not only size dependent, but also size-independent variation of the feeding system was associated with ontogenetic changes in diet in C. longicauda .  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 323–334.     

Sheltered preservation: a peculiar mode of ammonite occurrence in the Cretaceous Yezo Group, Hokkaido, north Japan

Maeda, H. 1991 01 15: Sheltered preservation: a peculiar mode of ammonitc occurrence in the Cretaceous Yeto Group, Hokkaido. north Japan. Lethaia , Vol. 24, pp. 69–82. Oslo. ISSN 0024–1164.
'Sheltered preservation', in which many small ammonites ('refugees') arc preserved in the inside and/or the lower umbilical void of a large ammonite shell ('shelter'), is a common preseivational style in the Cretaceous Yezo Group in Hokkaido, north Japan. The best example is large Calycoceras of Middle Cenomanian age, attaining 300 to 500 mm diameter, whose shell usually hours more than 100 individuals of Desmoceras comprising mainly juveniles less than 12 mm in diameter. In contrdst with other preservational styles of Desmoceras from the same horizon. the shells of refugee ammonites have not suffered phragmoeone collapse, and the inner whorls and a protoconch are intact. Many refugee ammonites are allochthonous, as indicated by the incomplete preservation of their living chamber and the absence of a jaw apparatus. The sheltered preservation is, therefore, a kind of 'Konzcntrat Lagerstatten' completed by both pre- and post-burial processes. Acting as a 'concentration trap' on the sea floor, a large empty ammonite shell probably triggered off such accumulation of the small ammonite shells in post-mortem transport across the sea floor. This biostratinomical process biased the original thanatococnosis of ammonites, so that its immature specimens were selectively accumulated and preserved in the shelter. Ammonoidea, taphonomy, Konzentrat Lagerstätten'. differenrial preservation, Cretuceous. Hokkaido .     

Morphological integration and adaptation in the snake feeding system: a comparative phylogenetic study

A long-standing hypothesis for the adaptive radiation of macrostomatan snakes is that their enlarged gape--compared to both lizards and basal snakes--enables them to consume "large" prey. At first glance, this hypothesis seems plausible, or even likely, given the wealth of studies showing a tight match between maximum consumed prey mass and head size in snakes. However, this hypothesis has never been tested within a comparative framework. We address this issue here by testing this hypothesis in 12 monophyletic clades of macrostomatan snakes using recently published phylogenies, published maximum consumed prey mass data and morphological measurements taken from a large sample of museum specimens. Our nonphylogenetically corrected analysis shows that head width--independent of body size--is significantly related to mean maximum consumed prey mass among these clades, and this relationship becomes even more significant when phylogeny is taken into account. Therefore, these data do support the hypothesis that head shape is adapted to prey size in snakes. Additionally, we calculated a phylogenetically corrected morphological variance-covariance matrix to examine the role of morphological integration during head shape evolution in snakes. This matrix shows that head width strongly covaries with both jaw length and out-lever length of the lower jaw. As a result, selection on head width will likely be associated with concomitant changes in jaw length and lower jaw out-lever length in snakes.     

Über Nahrung und Ernährungsweise von Ammoniten

Until only a few years ago, the majority of ammonites were considered to have been rather swift nectonic swimmers of little ecologic bondage. About their food, nothing was known with certainty. Comparison with recent Coleoids and withNautilus suggests, however, that most ammonoids were poor swimmers. It is not even certain that the hyponome was used for locomotion as much as inNautilus. Slow locomotion made it impossible for ammonites to hunt for fish or other highly agile prey. Their lower jaws, which are identical to the structures known as aptychi and anaptychi (formerly considered to be opercula), are like shovels and make it impossible for their bearers actually to bite and cut with them. Consequently the structure of their jaws also prevented their hunting large and active prey. Their jaws were probably actually used like shovels along the bottom of the sea. They may have gathered small or slow benthonic organisms like foraminifers, ostracodes, small crustaceans, young brachiopods, corals, bryozoa, but also drifting or slowly swimming and dead organisms. Several unusually well preserved stomachs of ammonites contained foraminifers, ostracodes, crinoids, smaller ammonites, and possibly inarticulate brachiopods. It is concluded that, ecologically, ammonites inhabited the place of modern bottom-feeding gastropods.     

Key innovations in Mesozoic ammonoids: the multicuspidate radula and the calcified aptychus

A nearly complete radula with seven elements per row preserved inside of an isolated, bivalved, calcitic lower jaw (= aptychus) of the Late Jurassic ammonite Aspidoceras is described from the Fossillagerstätte Painten (Bavaria, southern Germany). It is the largest known ammonite radula and the first record for the Perisphinctoidea. The multicuspidate tooth elements (ctenodont type of radula) present short cusps. Owing to significant morphological differences between known aptychophoran ammonoid radulae, their possible function is discussed, partly in comparison with modern cephalopod and gastropod radulae. Analogies between the evolution of the pharyngeal jaws of cichlid fishes and the ammonoid buccal apparatus raise the possibility that the evolution of a multicuspidate radula allowed for a functional decoupling of the aptychophoran ammonoid jaw. The radula, therefore, represents a key innovation which allowed for the evolution of the calcified lower jaws in Jurassic and Cretaceous aptychophoran ammonites. Possible triggers for this morphological change during the early Toarcian are discussed. Finally, we hypothesize potential adaptations of ammonoids to different feeding niches based on radular tooth morphologies.     

Sensory modulation and behavioral choice during feeding in the Australian frog, Cyclorana novaehollandiae

This study investigates how visual and tactile sensory information, as well as biomechanical effects due to differences in physical characteristics of the prey, influence feeding behavior in the frog Cyclorana novaehollandiae. Video motion analysis was used to quantify movement patterns produced when feeding on five prey types (termites, waxworms, crickets, mice and earthworms). Twelve kinematic variables differed significantly among prey types, and twelve variables were correlated with prey characteristics (including mass, length, height and velocity of movement). Results indicate that C.␣novaehollandiae uses a different strategy to capture each prey type. Visual assessment of prey characteristics appeared to be more important in modulating feeding behavior than tactile cues or biomechanical effects. We propose a hierarchical hypothesis of behavioral choice, in which decisions are based primarily on visual analysis of prey characteristics. In this model, the frogs first choose between jaw prehension and tongue prehension based on prey size. If they have chosen jaw prehension, they next choose between upward or downward head rotation based on length and height of the prey. If they have chosen tongue prehension, they next choose between behavior for fast and slow prey. Final decisions may be the result of behavioral fine tuning based on tactile feedback. Accepted: 5 August 1996     

Feeding habits of the blue shark, Prionace glauca, and salmon shark, Lamna ditropis, in the transition region of the Western North Pacific

We describe the feeding habits of 70 blue sharks (Prionace glauca) and 39 salmon sharks (Lamna ditropis) caught at 0–7 m depth at night by research drift gillnets in the transition region of the western North Pacific during April–May of 1999 and 2000. Blue sharks of 50–175 cm total length fed on a large variety of prey species, consisting of 24 species of cephalopods and 16 species of fishes. Salmon sharks of 69–157 cm total length fed on a few prey species, consisting of 10 species of cephalopods and one species of fish. Important prey for the blue sharks were large, non-active, gelatinous, meso- to bathypelagic cephalopods (e.g., Chiroteuthis calyx, Haliphron atlanticus, Histioteuthis dofleini and Belonella borealis) and small myctophid fishes. Important prey for the salmon sharks were mid-sized, active, muscular, epi- to mesopelagic squids (e.g. Gonatopsis borealis, Onychoteuthis borealijaponica and Berryteuthis anonychus). Our results suggest that blue sharks feed on cephalopods mainly during the daytime when they descend to deep water. Salmon sharks may feed opportunistically with no apparent diurnal feeding period. Blue sharks and salmon sharks have sympatric distribution in the transition region in spring; they have different feeding habits and strategies that reduce competition for food resources.     

Changing handling times during feeding and consequences for prey size selection of 0+ zooplanktivorous fish

The interrelationship of fish size, prey size and handling time within a 15-min feeding period was studied in three size groups of 0 + roach, Rutilus rutilus, and bleak, Alburnus alburnus. Four size classes of cladoceran prey were used to measure changes in feeding rate and handling time from initial rapid feeding to sustained feeding. Observed differences in increase of handling time between prey size classes led to a change in the prey profitability ranking of those size classes within the first 2 min of the experiments. A 1-min feeding period is interpreted as reflecting an intermediate motivational status between extreme hunger and satiation. The use of average handling times for this period revealed a substantial change in prey profitability estimates compared to previous studies which used handling times based on short-term (a few seconds up to 1 min) feeding. It is not the largest prey items a fish can handle and swallow that are most profitable, but prey of intermediate size. By this approach a closer fit between expectations derived from optimal foraging theory and empirical data on prey size selection of 0 + zooplanktivorous fish is qualitatively achieved. Optimal prey size was found to be close the mouth gape width in small fish of 15 mm standard length, decreasing to 50% of mouth gape width in fish of 40 mm standard length.     

Prey selection by age-0 walleye pollock, Theragra chalcogramma, in nearshore waters of the Gulf of Alaska

Juvenile walleye pollock, Theragra chalcogramma, is the dominant forage fish on the continental shelf of the Gulf of Alaska, yet little is known about the feeding habits of this important interval of pollock life history. The taxonomic composition and size of prey found in the stomachs of age-0 juveniles collected at three nearshore locations in the Gulf of Alaska in September 1990 were compared to the composition and size of zooplankton collected in concurrent plankton tows. The maximum length of prey consumed increased dramatically over the length range of pollock examined (58–110 mm) from approximately 7 mm to 30 mm, due mainly to the consumption of large euphausiids and chaetognaths by the bigger individuals. The maximum width of prey changed little over this size range although there was a general increase in prey width with increasing predator size. The minimum prey length and width did not change with increasing fish size. Juvenile pollock generally selected the larger prey sizes relative to what was available. Juvenile pollock showed a marked preference for adult euphausiids and decapod larvae and an avoidance of copepods and chaetognaths relative to the numbers collected in net tows. These results are discussed relative to the feeding ecology of these juvenile fishes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Foraging behaviour in the jumping spider Phidippus audax: bases for selectivity

The hunting and feeding behaviour of the jumping spider Phidippus audax was examined in the laboratory under single and multi-prey conditions. When given the choice, spiders consistently selected insects with high activity levels and crawling velocities. Selection was not correlated with insect length, mass, or length/width ratio. However, cine analysis of single predator-prey encounters indicated that, at the time of detection, prey size (length and mass) was evaluated by the predator; spiders pursued large insects at significantly slower rates (i.e. more cautiously) than small insects. Prey size also significantly affected handling times. Time invested in handling preferred items was similar whether these were encountered alone or with alternate prey available. However, as predicted by the optimal foraging theory, spiders spent significantly less time feeding on lower ranked items in the presence of alternative prey.     

Ammonite aptychi: Functions and role in propulsion

Seven previous proposals of aptychus (sensu stricto) function are reviewed: lower mandible, protection of gonads of females, protective operculum, ballasting, flushing benthic prey, filtering microfauna and pump for jet propulsion. An eighth is introduced: aptychi functioned to actively stabilize the rocking produced by the pulsating jet during forward foraging and backward swimming. Experiments with in-air models suggest that planispiral ammonites could lower their aperture by the forward shift of a mobile cephalic complex. In the experiments, the ventral part of the peristome is lowered from the lateral resting (neutral) position by the added “ballast” of a relatively thin Laevaptychus to an angle < 25° from horizontal with adequate stability to withstand the counter-force produced by the jet of the recurved hyponome. However, of the shell forms tested, only brevidomes with thick aptychi, e.g., the Upper Jurassic Aspidoceratidae with Laevaptychus and average whorl expansion rates, were stable enough to swim forward by jet propulsion at about Nautilus speed (∼ 25 cm/s). We propose that aptychus function most commonly combined feeding (jaw, flushing, filtering) with protection (operculum), and, more rarely, with locomotion (ballast, pump, diving and stabilizing plane). Aptychi may thus have been multi-functional.     

Terrestrial feeding in the Mudskipper Periophthalmus (Pisces: Teleostei): A cineradiographic analysis

Mudskipping gobies (Periophthalminae) are among the most terrestrial of amphibious fishes. Specializations associated with terrestrial prey capture and deglutition have been studied in Periophthalmus koelreuteri by light and X-ray cinematography which permits direct visualization of pharyngeal jaw movement during deglutition. Anatomical specializations of the pharyngeal jaws are described and include depressible teeth, a large ventral process on ceratobranchial five, and muscular modifications.
Multiple terrestrial feedings occur by Periophthalmus without a return to the water, and cineradiography reveals that the buccal cavity is often filled with air during terrestrial excursions in contrast to some previous hypotheses. Transport of the prey into the oesophagus occurs primarily by anteroposterior movement of the upper pharyngeal jaw. The lower pharyngeal jaw plays a limited role in food transport and may serve primarily to hold and position prey. The bite between upper and lower pharyngeal jaws occurs between the anterior teeth, and both jaws are protracted together during raking of food into the oesophagus. Functional specializations correlated with terrestrial feeding include obligatory use of pharyngeal jaws for swallowing even small prey items and positioning of the prey in the pharynx by pharyngeal jaw and hyoid movements alone.
This analysis of terrestrial feeding allows hypotheses of design constraints imposed by the aquatic medium on fishes to be raised and tested.     

Zur Anatomie und Ökologie von Ammoniten: Funde von Kropf und Kiemen

Soft parts within the living chambers of specimens of the generaArnioceras, Hildoceras, «Oppelia», andPhysodoceras are described. Special attention is given to the contents of the crops and, in consequence, to the feeding habits of ammonites. Our analysis shows that foraminifera, ostracods, small ammonites, and crinoids have been eaten by ammonites. A find of ammonite gills is demonstrated.     

Taphonomic differentiation of Oxfordian ammonites from the Cracow Upland, Poland

Taphonomic analysis of Lower and Middle Oxfordian ammonites from the Cracow Upland, southern Poland (localities at Pod???e, Zalas, M?ynka) revealed differences in ammonite preservation. The studied ammonites, usually termed as external and internal moulds, show a more complex state of preservation. In the Middle Oxfordian glauconitic marls, ammonites are preserved as internal moulds with neomorphic calcite shells showing relics of the original internal structure. In the Middle Oxfordian platy peloidal limestones, ammonites are preserved mostly as external moulds, without septal suture, however under microscope might show relics of internal whorls and septa and/or subtle differences in sediment filling phragmocone chambers. In sponge–microbial bioherms and biostromes, ammonite internal moulds have shells, which in contrast to ammonites from glauconitic marls are not strictly neomorphic ones, but originated by shell dissolution and subsequent filling of moldic porosity by calcite cement. In sponge–microbial nodular limestones, the ammonites are strongly deformed and the outer wall is usually removed by dissolution under pressure. Other important taphonomic differences include the rate of compaction (highest in platy limestones), sedimentary infillings, microborings, encrustations and preservation of siphuncular tubes. The majority of the ammonites appear to be phragmocones; aptychi in all facies are rare. Siphuncular tubes are fossilized exclusively in oppeliids, only in specimens from glauconitic marls and platy limestones, although their other taphonomic attributes are different. Tubes seem to have fossilized due to microbially mediated phosphatization that could be favoured by a set of parameters which operated rather at the scale of ammonoid carcasses: closed, poorly oxygenated conditions, and reduced pH. Taphonomic processes were controlled by the sedimentary environment (fragmentation, sedimentary filling, phosphatization of siphuncular tubes), as well as by early and late diagenesis (neomorphic transformation, dissolution, cementation, compaction) influenced by lithology.     

Cranial morphological scaling and relative prey size limitations for a native predator in an invaded system

Over evolutionary time, predator-prey interactions have shaped and constrained functional and behavioral traits of piscivorous fishes. The endangered Colorado Pikeminnow Ptychocheilus lucius, a large endemic piscivore of the Colorado River Basin, encounters a substantially altered prey base that differs in behaviors and morphologies compared to the historical suite of native prey. To assess physical limitations of Colorado Pikeminnow predation, we conducted a feeding experiment with two species of nonnative prey (spined and despined Channel Catfish Ictalurus punctatus and Red Shiner Cyprinella lutrensis) and quantified scaling of cranial morphology in this predator. In our predation experiments, Colorado Pikeminnow (215–312 mm total length) consumed both spined and despined Channel Catfish as well as Red Shiner but only consumed prey less than 20% of the predator’s total length. Previous feeding trials using smaller Colorado Pikeminnow, with native and nonnative prey species, indicated they consumed prey up to 35% of their total length, suggesting relative prey size limits may decrease as this predator grows. Morphological measurements also suggested relative prey size suitability may decrease as Colorado Pikeminnow become larger, with head depth and width demonstrating isometric scaling at small sizes and shifting to negative allometry as fish get larger. Together, these data suggest an ontogenetic shift in the head morphology of Colorado Pikeminnow may decrease the relative size of prey available to these predators. In severely altered systems, understanding trophic characteristics that limit overall predator resource availability will be critical for conservation of piscivorous fishes.