Relative importance of growth and behaviour to elasmobranch suction-feeding performance over early ontogeny.
ABSTRACT: Development of the ability to capture prey is crucial to predator survival. Trends in food-capture performance over early ontogeny were quantified for leopard sharks Triakis semifasciata and whitespotted bamboosharks Chiloscyllium plagiosum by measuring suction pressure and flow in front of the mouth during feeding. At any size, C. plagiosum produce greater subambient pressure and ingest more rounded water parcels. Maximum subambient pressure scaled with negative allometry in T. semifasciata and was accompanied by an increase in the time to reach maximum gape. Despite a similar trend in buccal expansion timing, maximum pressure in C. plagiosum scaled with isometry and was accompanied by an earlier onset of hyoid depression and a positive allometric increase in buccal reserve volume. Growth was the primary factor responsible for developmental trends in both species, with size-independent behavioural changes contributing little to overall performance variability. Ontogenetic dietary shifts are predicted for both species as a consequence of size-dependent changes in performance. Chiloscyllium plagiosum becomes anatomically and behaviourally canalized towards suction feeding, limiting the effective range of prey capture and possibly necessitating stalking. Triakis semifasciata, by contrast, retains the flexibility to employ both ram and suction and therefore captures more elusive prey with age.
Project description:Chiloscyllium, commonly called bamboo shark, can be found inhabiting the waters of the Indo-West Pacific around East Asian countries such as Malaysia, Myanmar, Thailand, Singapore, and Indonesia. The International Union for Conservation of Nature (IUCN) Red List has categorized them as nearly threatened sharks out of their declining population status due to overexploitation. A molecular study was carried out to portray the systematic relationships within Chiloscyllium species using 12S rRNA and cytochrome b gene sequences. Maximum parsimony and Bayesian were used to reconstruct their phylogeny trees. A total of 381?bp sequences' lengths were successfully aligned in the 12S rRNA region, with 41?bp sites being parsimony-informative. In the cytochrome b region, a total of 1120?bp sites were aligned, with 352 parsimony-informative characters. All analyses yield phylogeny trees on which C. indicum has close relationships with C. plagiosum. C. punctatum is sister taxon to both C. indicum and C. plagiosum while C. griseum and C. hasseltii formed their own clade as sister taxa. These Chiloscyllium classifications can be supported by some morphological characters (lateral dermal ridges on the body, coloring patterns, and appearance of hypobranchials and basibranchial plate) that can clearly be used to differentiate each species.
Project description:To understand the mechanisms of liver regeneration better to promote research examining liver diseases and marine biology, normal and regenerative liver tissues of Chiloscyllium plagiosum were harvested 0?h and 24?h after partial hepatectomy (PH) and used to isolate small RNAs for miRNA sequencing. In total, 91 known miRNAs and 166 putative candidate (PC) miRNAs were identified for the first time in Chiloscyllium plagiosum. Through target prediction and GO analysis, 46 of 91 known miRNAs were screened specially for cellular proliferation and growth. Differential expression levels of three miRNAs (xtr-miR-125b, fru-miR-204, and hsa-miR-142-3p_R-1) related to cellular proliferation and apoptosis were measured in normal and regenerating liver tissues at 0?h, 6?h, 12?h, and 24?h using real-time PCR. The expression of these miRNAs showed a rising trend in regenerative liver tissues at 6?h and 12?h but exhibited a downward trend compared to normal levels at 24?h. Differentially expressed genes were screened in normal and regenerating liver tissues at 24?h by DDRT-PCR, and ten sequences were identified. This study provided information regarding the function of genes related to liver regeneration, deepened the understanding of mechanisms of liver regeneration, and resulted in the addition of a significant number of novel miRNAs sequences to GenBank.
Project description:Suction feeding is the most common form of prey capture across aquatic feeding vertebrates and many adaptations that enhance efficiency and performance are expected. Many suction feeders have mechanisms that allow the mouth to form a planar and near-circular opening that is believed to have beneficial hydrodynamic effects. We explore the effects of the flattened and circular mouth opening through computational fluid dynamics simulations that allow comparisons with other mouth profiles. Compared to mouths with lateral notches, we find that the planar mouth opening results in higher flow rates into the mouth and a region of highest flow that is positioned at the centre of the mouth aperture. Planar mouths provide not only for better total fluid flow rates through the mouth but also through the centre of the mouth near where suction feeders position their prey. Circular mouths are shown to provide the quickest capture times for spherical and elliptical prey because they expose the prey item to a large region of high flow. Planar and circular mouths result in higher flow velocities with peak flow located at the centre of the mouth opening and they maximize the capacity of the suction feeders to exert hydrodynamic forces on the prey.
Project description:Prey capture is critical for survival, and differences in correctly positioning and timing a strike (accuracy) are likely related to variation in capture success. However, an ability to quantify accuracy under natural conditions, particularly for fishes, is lacking. We developed a predictive model of suction hydrodynamics and applied it to natural behaviours using three-dimensional kinematics of three centrarchid fishes capturing evasive and non-evasive prey. A spheroid ingested volume of water (IVW) with dimensions predicted by peak gape and ram speed was verified with known hydrodynamics for two species. Differences in capture success occurred primarily with evasive prey (64-96% success). Micropterus salmoides had the greatest ram and gape when capturing evasive prey, resulting in the largest and most elongate IVW. Accuracy predicted capture success, although other factors may also be important. The lower accuracy previously observed in M. salmoides was not replicated, but this is likely due to more natural conditions in our study. Additionally, we discuss the role of modulation and integrated behaviours in shaping the IVW and determining accuracy. With our model, accuracy is a more accessible performance measure for suction-feeding fishes, which can be used to explore macroevolutionary patterns of prey capture evolution.
Project description:Extensive gene duplication is thought to have occurred in the vertebrate lineage after it diverged from cephalochordates and before the divergence of lobe- and ray-finned fishes, but the exact timing remains obscure. This timing was investigated by analysis of the Dlx gene family of a representative cartilaginous fish, the leopard shark, Triakis semifasciata. Dlx genes encode homeodomain transcription factors and are arranged in mammals as three convergently transcribed bigene clusters. Six Dlx genes were cloned from Triakis and shown to be orthologous to single mammalian Dlx genes. At least four of these are arranged in bigene clusters. Phylogenetic analyses of Dlx genes were used to propose an evolutionary scenario in which two genome duplications led to four Dlx bigene clusters in a common ancestor of jawed vertebrates, one of which was lost prior to the diversification of the group. Dlx genes are known to be involved in jaw development, and changes in Dlx gene number are mapped to the same branch of the vertebrate tree as the origin of jaws.
Project description:We discovered that knifefish (Apteronotus albifrons) during suction feeding can produce millimeter-sized cavitation bubbles and flow accelerations up to?~?450 times the acceleration of gravity. Knifefish may use this powerful suction-induced cavitation to cause physical damage on prey hiding in narrow refuges, therefore facilitating capture.
Project description:Suction feeding is the most commonly used mechanism of prey capture among aquatic vertebrates. Most previous models of the fluid flow caused by suction feeders involve making several untested assumptions. In this paper, a Chimera overset grids approach is used to solve the governing equations of fluid dynamics in order to investigate the assumptions that prey do not interact with the flow and that the flow can be modelled as a one-dimensional flow. Results show that, for small prey, both neglecting the prey and considering prey interaction give similar calculated forces exerted on the prey. However, as the prey item increases in size toward the size of the gape, its effect on the flow becomes more pronounced. This in turn affects both the magnitude of the hydrodynamic forces imparted to the prey and the time when maximum force is delivered. Maximum force is delivered most quickly to intermediate sized prey, about one-third of mouth diameter, and most slowly to prey less than 7 per cent or greater than 67 per cent of mouth diameter. This suggests that the effect of prey size on the timing of suction forces may have substantial consequences for the feeding ecology of suction feeders that are known to prefer prey between 25 and 50 per cent of mouth diameter. Moreover, for a 15 cm fish with a 15 mm gape, assuming a radial one-dimensional flow field can result in underestimating the maximum force exerted on a 5 mm diameter spherical prey 1 gape distance from the mouth by up to 28.7 per cent.
Project description:We recorded capture events (CEs) of the daphniid Ceriodaphnia dubia by the carnivorous Southern bladderwort with suction traps (Utricularia australis). Independent to orientation and behavior during trap triggering, the animals were successfully captured within 9?ms on average and sucked in with velocities of up to 4?m/s and accelerations of up to 2800?g. Phases of very high acceleration during onsets of suction were immediately followed by phases of similarly high deceleration (max.: -1900?g) inside the bladders, leading to immobilization of the prey which then dies. We found that traps perform a 'forward strike' during suction and that almost completely air-filled traps are still able to perform suction. The trigger hairs on the trapdoors can undergo strong bending deformation, which we interpret to be a safety feature to prevent fracture. Our results highlight the elaborate nature of the Utricularia suction traps which are functionally resilient and leave prey animals virtually no chance to escape.
Project description:A unique example of phenotypic flexibility of the oral apparatus is present in newts (Salamandridae) that seasonally change between an aquatic and a terrestrial habitat. Newts grow flaps of skin between their upper and lower jaws, the labial lobes, to partly close the corners of the mouth when they adopt an aquatic lifestyle during their breeding season. Using hydrodynamic simulations based on ?CT-scans and cranial kinematics during prey-capture in the smooth newt (Lissotriton vulgaris), we showed that this phenotypic flexibility is an adaptive solution to improve aquatic feeding performance: both suction distance and suction force increase by approximately 15% due to the labial lobes. As the subsequent freeing of the corners of the mouth by resorption of the labial lobes is assumed beneficial for the terrestrial capture of prey by the tongue, this flexibility of the mouth fine-tunes the process of capturing prey throughout the seasonal switching between water and land.