The ontogeny of feeding behavior and cranial morphology in the leopard shark Triakis semifasciata (Girard 1854): A longitudinal perspective

While much is known about the ecological and functional morphology of feeding in lower vertebrates, studies of elasmobranch feeding over ontogeny are broadly lacking. In this study, the ontogeny of feeding behavior and morphology were investigated in neonatal and young-of-the-year leopard sharks Triakis semifasciata using morphometric measurements of growth and high-speed videography in a longitudinal study. Five food types were used during filming sessions to facilitate differentiation of modulation and variation over ontogeny. Functional aspects of muscle and buccal volume scaling were investigated through dissection. Growth over ontogeny was shown to influence numerous kinematic variables, while intra- and inter-individual variability was the dominant factor affecting feeding behavior. Modulation of feeding behavior based on food size and elusiveness was present for timing variables and predator motion during the strike, but not for food motion or the relative extent of buccal expansion. Allometric growth occurred in all aspects of external cranial morphology measured, resulting in a shallower head profile, anterior displacement of the mouth, and relatively larger jaw musculature over ontogeny. While the degree to which morphology constrains or enhances behavior cannot be directly quantified, variability in behavior greatly exceeds variability in morphology over early ontogeny. Maintenance of a behaviorally and morphologically versatile feeding apparatus throughout ontogeny is proposed to enhance the exploitation of resources and facilitate a diverse diet in T. semifasciata under variable environmental conditions.     

Fine structure and functional morphology of the mouthparts of Bittacus planus and Terrobittacus implicatus (Insecta: Mecoptera: Bittacidae)

The Bittacidae are unique in Mecoptera for their adults being predaceous. However, their mouthparts have not been well documented for functional morphology to date. Here, we investigated the mouthpart morphology of the hangingflies Bittacus planus Cheng and Terrobittacus implicatus (Huang & Hua) using scanning electron microscopy. The mouthparts are of the mandibulate type and situated at the tip of an elongated rostrum. The labrum is greatly elongated, roughly twice as long as the subquadrate clypeus. The epipharynx is furnished with a row of basiconic sensilla arranged evenly as a median band extending from the apex to the base. The mandibles are slender and elongated, bearing a sharp lateral and a small mesal tooth. The maxillae are well developed, each consisting of a partially sclerotized cardo and a stipes, a hirsute galea and a lacinia, and a five-segmented maxillary palp. The sensillar pattern on the distal segment of the maxillary palp differs slightly between the two bittacid species. The labium is composed of a postmentum, a prementum, and a pair of two-segmented labial palps. The feeding mechanism of bittacids is briefly discussed in combination with the mouthpart morphology and their feeding habits.     

Comparative morphology of the somatic musculature in species of Hexarthra and Polyarthra (Rotifera, Monogononta): Its function in appendage movement and escape behavior

Species of Hexarthra and Polyarthra are freshwater rotifers with well-known escape behaviors that result from interactions with planktonic predators. Both rotifers bear a suite of mobile appendages that function in evasive maneuvers and saltatory jumps through the water column, but the anatomical and functional bases of these actions are poorly understood. Here, we use a combination of phalloidin staining, confocal laser scanning microscopy, and video analysis to describe the morphology of the somatic muscles that supply the mobile appendages in order to understand how they function in escape behavior. Results show that species of Hexarthra, which bear six radially distributed limbs, possess a highly complex trunk musculature that supplies the inside of each limb with its own abductor and adductor muscles, i.e., a direct muscle supply. The singular dorsal and ventral limbs each receive a pair of large abductor and adductor muscles (four muscles total per limb), while the paired dorsolateral and ventrolateral limbs each receives three muscles (two abductors, one adductor per limb). Contraction of the abductor muscles creates a power stroke in the form of an anterior sweep of the limbs, which leads to a three-dimensional tumbling of the rotifer through the water column. Alternatively, species of Polyarthra possess 12 blade-like appendages that are arranged into four equal bundles; each bundle receives an indirect muscle supply that attaches to the shoulder of the paddles. A single longitudinal paddle muscle supplies each dorsolateral bundle, while a pair of longitudinal paddle muscles supplies each ventrolateral bundle. Contraction of these muscles, whether singly or in concert, functions to abduct the paddles in a power stroke, leading to rotation of the body and movement of the rotifer. The recovery stroke is hypothesized to be a multi-step process that begins with reorientation of the appendages prior to adduction, followed by contraction of various muscles to antagonize the paddle muscles. In total, these observations reveal novel complexities in the rotifer muscular system that aids our understanding of the biophysics of predator avoidance in appendage-bearing rotifers.     

Computational fluid dynamics of flow regime and hydrodynamic forces generated by a gliding North Atlantic right whale (Eubalaena glacialis)

Accurate estimates of drag on marine animals are required to investigate the locomotive cost, propulsive efficiency, and the impacts of entanglement if the animal is carrying fishing gear. In this study, we performed computational fluid dynamics analysis of a 10 m (length over all) right whale to obtain baseline measurements of drag on the animal. Swimming speeds covering known right whale speed range (0.125 m/s to 8 m/s) were tested. We found a weak dependence between drag coefficient and Reynolds number. At a swimming speed of 2 m/s, we analyzed the boundary layer thicknesses, the flow regimes, and drag components. We found the thickest boundary layer at the lateral sides of the peduncle, whereas the boundary layer thickness over the outer part of the flukes was less than 1.7 cm. Laminar flow occurred over the anterior ~0.6 LoA and turbulent flow from ~0.8 LoA to the fluke notch. On the surfaces of the flukes outside of the body wake region, flow was laminar. Our most significant finding is that the drag coefficient (0.0071–0.0059) of a right whale for swimming speeds ranging from 0.25 m/s to 2 m/s is approximately twice that of many previous estimates for cetaceans.     

Effects of turbulence on the feeding rate of a pelagic predator: The planktonic hydroid Clytia gracilis

Relatively little is known about the role of turbulence in a predator-prey system where the predator is a passive, pelagic forager. The Campanulariid hydroid Clytia gracilis (Cnidaria, Hydrozoa) is unusual because it occurs as planktonic colonies and is reported to forage passively in the water column on Georges Bank, Massachusetts, USA. In this study, we investigated the role of various turbulence conditions on the feeding rate of C. gracilis colonies in laboratory experiments. We found a positive relationship between turbulence velocities and feeding rates up to a turbulent energy dissipation rate of ca. 1 cm² s^− 3. Beyond this threshold feeding rate decreased slightly, indicating a dome-shaped relationship. Additionally, a negative relationship was found between feeding efficiency and hydroid colony size under lower turbulent velocities, but this trend was not significant under higher turbulence regimes.     

Elucidating the mechanism of poricidal anther dehiscence in Miconia species (Melastomataceae)

Melastomataceae have porate anthers. However, unlike Solanaceae and many monocots, in which the poricidal dehiscence depends on the presence of a mechanical layer (often the endothecium), most members of Melastomataceae have no evident specialized layer related to the poricidal opening. The goal of this study was to characterize the tissues that form the apical pore of the anther in 10 Miconia species, which may help to understand the nearly unknown mechanism of anther dehiscence in this genus, considered to be one of the largest and most diverse New World genera. Before anthesis, the apical pores of all of the species are closed by a uniseriate epidermis, the cells of which lack a cuticle. In contrast, the epidermis of the remainder of the anther is covered by a thick, ornamented cuticle. Among Myrtales, the Melastomataceae form a clade with Alzateaceae, Crypteroniaceae and Penaeaceae, almost all of which have anthers with endothecium lacking wall thickenings. In these families, the endothecium may or may not be present in the mature anther, with degenerating cells in the latter case. Anther dehiscence does not depend on the endothecium as the mechanical layer, and this process is still not well understood. However, in the Miconia species studied here, the cuticle may prevent tissue dehydration, and the pore opening seems to be due to the passive process of dehydration taking place only in the pore region due to the absence of the cuticle.     

Nudibranch-sponge feeding dynamics: Benefits of symbiont-containing sponge to Archidoris montereyensis (Cooper, 1862) and recovery of nudibranch feeding scars by Halichondria panicea (Pallas, 1766)

Selected interactions between the encrusting sponge Halichondria panicea and its primary predator, the dorid nudibranch Archidoris montereyensis, were investigated in a high-latitude rocky intertidal community spatially dominated by H. panicea. Feeding experiments were conducted in which A. montereyensis pairs were provided with sponge containing symbiotic zoochlorellae or sponge in which the zoochlorellae population had been reduced or removed by shading. Nudibranchs consuming H. panicea with symbiotic zoochlorellae had higher feeding, growth, and egg production rates than individuals eating aposymbiotic sponge. We simulated A. montereyensis predation on H. panicea by creating typically sized feeding grooves in the sponge. H. panicea's response was high linear growth rates into the experimental feeding grooves, generally recovering most of the groove area within 4 weeks. Overall, the sponge's rapid response to tissue damage minimizes grazing impacts and substrate loss and reduces susceptibility to wave removal.     

Determining effects of suspended sediment on condition of a suspension feeding bivalve (Atrina zelandica): results of a survey, a laboratory experiment and a field transplant experiment

The horse mussel Atrina zelandica (Gray) is a large, suspension feeding pinnid bivalve, common in coastal and estuarine areas of northern New Zealand. As a suspension feeder, Atrina is likely to be influenced by suspended sediment loads. We conducted a laboratory experiment to determine the effect of short-term elevations in turbidity levels, such as those commonly recorded during storms, on the physiological condition and clearance rates of Atrina. We also conducted a field survey and a 3-month transplant experiment at multiple sites along a gradient of increasing suspended sediment load in a New Zealand estuary. Laboratory clearance rates of Atrina declined above a threshold suspended sediment concentration, and Atrina physiological condition at the end of this experiment was lower in high cf. low turbidity treatments. Decreases in Atrina condition were detected after exposure to elevated levels for only 3 days. The field survey and transplant experiment provided empirical evidence of a strong, negative effect of increasing suspended sediment flux on the physiological condition of Atrina. We suggest that relationships between the physiological condition of suspension feeders and sediment settling flux could provide a link between sediment inputs, which commonly occur as a result of catchment runoff during rainfall events, and the ecological health of estuarine and shallow coastal areas. Our study also demonstrated that Atrina have a natural distribution limit controlled by suspended sediment load. Thus, there is potential for larger-scale functional and structural effects on benthic communities in estuarine and coastal areas with high rates of sedimentation.     

Effects of jaw adductor hypertrophy on buccal expansions during feeding of air breathing catfishes (Teleostei,Clariidae)

Some species of Clariidae (air breathing catfishes) have extremely well developed (hypertrophied) jaw closing muscles that increase the maximal biting force of these species. As these enlarged jaw muscles tightly cover the suspensoria, which are firmly connected to the neurocranium, we expect diminished lateral expansions during suction for species with hypertrophied jaw muscles. In turn, this could imply a reduced suction performance for these species. Compared to Clarias gariepinus, which has relatively small jaw closers, Clariallabes longicauda shows a clear hypertrophy of the jaw adductors. A kinematic analysis of prey capture in these two species is presented here. As predicted, Clariallabes longicauda shows less lateral expansion (average abduction of the hyoids of 19.0°) than Clarias gariepinus (abduction of 31.1°). However, our data indicate that the decrease in lateral expansion capacity in the species with excessive adductor development is compensated for by a larger and faster ventral expansion of the buccal cavity by depression of the hyoid.     

New insights into the larval development of Macandrevia cranium (Müller, 1776) (Brachiopoda: Rhynchonelliformea)

The terebratulid Macandrevia cranium (Müller, 1776) is a representative of articulate brachiopods. However, little is known about its embryology and larval development. In order to obtain reproducible results we used a strict protocol of artificial fertilization under controlled temperature conditions as a basis for our morphological study. Sampling of embryos or developing larvae at frequent intervals led to the most comprehensive collection of preserved developmental stages, ranging from early zygotes to late three-lobed stage larvae. SEM studies of all these stages showed that the development of M. cranium is similar to that of other terebratulid brachiopods. This includes the presence of four bundles of larval setae in three-lobed stage larvae. Our results contradict earlier observations on the development of M. cranium and show that this species exhibits more typical features of articulate brachiopod development than previously thought.     

Habitat selection by two Mediterranean species of Aplysia: A. fasciata poiret and a. depilans Gmelin (Mollusca : Opisthobranchia)

Factors influencing habitat selection were examined in two species of Mediterranean Aplysia. Animals and egg masses were found in four types of habitats that varied in degree of exposure to wave action. Both species were frequently found in groups. Neither species was common in areas cut off from the surge of the sea. No difference in food preference was observed. A. depilans Gmelin were primarily found in areas subject to greater wave action, while A.fasciata Poiret dominated the calmer habitats. Both species were common in intermediate environments. In late summer, when A. depilans are absent, A. fasciata penetrated some environments previously dominated by the former. Morphological and behavioural features of A. depilans and A.fasciata are consistent with adaptation to rough and calm habitats, respectively.     

低温对蝶蛹金小蜂卵成熟及其数量动态的影响

寄生蜂卵成熟动态影响其产卵决策行为,因而对于认识寄生蜂搜寻行为生态学机理具有重要意义。以蝶蛹金小蜂(Pteromalus puparum)-菜粉蝶(Pieris rapae)为模式生物,首先连续3周每隔24 h详细观察子代蜂幼期不同发育阶段的体型、卵巢管以及寄主蛹的外部形态,以此为基础观察了低温处理(模拟越冬温度)被寄生蛹对子代蜂成熟卵数量动态的影响。蝶蛹金小蜂胚后发育历时约2周,其中卵期1 d;幼虫历期约7 d。初孵幼虫体透明;胚后第3—6天体积快速增大,然后减缓,体色由绿变黄;胚后第8天进入预蛹,第9—12天蛹淡色,复眼由淡黄变为深红,第13—14天蛹暗黑色,并逐渐带有金属光泽。卵巢管在羽化当天即开始沉积卵黄,并在羽化后1—4 d连续增加直到出现卵吸收;羽化后5—6 d成熟卵数量增速不明显甚至略有减小。寄主蛹随子代蜂从卵发育至幼虫再到蛹体色从绿色变为灰褐色再到土黄色。低温处理被寄生的寄主蛹(寄生蜂处于老熟幼虫或蛹期)后,羽化成虫的卵巢管略细,成熟卵数量较少。成熟卵数量的变化不仅受低温处理的影响,而且受雌蜂体型大小和日龄的影响;低温处理明显减缓卵成熟速率,各日龄期成熟卵数量均明显减少;适温下成熟卵数量于羽化后第4天达到峰值,而低温处理下成熟卵数量达到峰值的时间延迟至第7天。研究表明,越冬低温对来年羽化的蝶蛹金小蜂卵成熟动态具有不良影响。     

Pollen morphology of Chinese Curcuma L. and Boesenbergia Kuntz (Zingiberaceae): Taxonomic implications

In order to find new non-molecular evidence to support the phylogenetic and taxonomic position, pollen grains of 20 populations of 16 species of Chinese Curcuma L. and Boesenbergia Kuntz (Zingiberaceae) were investigated under SEM and TEM. The pollen grains are spherical and ovoid, nonaperturate. The pollen wall is composed of a very thin exine and a thick intine. The exine is psilate or echinate. The intine consists of two layers, i.e., a thick, channeled layer (exintine) and an inner homogenous layer (endintine). The results reveal morphological congruence between the pollen grains of species of Curcuma, which according to DNA sequence data appears to be a polyphyletic genus. However the uniform pollen morphology in Curcuma provides no evidence to divide this genus into separate taxonomic entities. Our results on pollen morphology also do not provide any additional evidence to either unite or segregate Boesenbergia albomaculata and Curcumorpha longiflora in the same genus and demonstrate that more taxonomic data on the genus Boesenbergia and its relatives are needed before a final decision can be made.     

Fissiphalliidae, a new family of South American laniatorean harvestmen (Arachnida: Opiliones)

Fissiphalliidae, a new family of the Opiliones suborder Laniatores, is described in the superfamily Gonyleptoidea, based on a new genus (Fissiphallius n. gen.) und 3 new species (F. sturmi n. sp., F. spinulatus n. sp., F. sympatricus n. sp.) from Colombia. Most emphasized are the male genitalic characters, unique in Opiliones: A honzontally split truncus which results in a long movable (glans) and an immovable finger (distal part of the truncus). Both hide the extremely long stylus with the seminal opening at its end. In an expanded state, the movable finger is bent dorsally by an erectile vesicle. It is shown that male genitalic characters in Opiliones display clear functional and constructional traits on the family level. Those characters, if used appropriately, will demonstrate that several families in gonyleptoid Laniatores are polyphyletic and should be divided into several taxa of the family level.     

Temperature as a cue for the periodicity in feeding of Brachycentrus occidentalis (Insecta: Trichoptera)

Filtering behaviour of two groups of Brachycentrus occidentalis larvae exposed to a diel temperature cycle and a LD12:12 photoperiod, was observed for 5 days at 4-hr intervals. Both groups were then subjected to 5 days of continuous light; however, a diel temperature pattern was maintained for only one group. Behaviour of larvae showed a diel periodicity under the initial conditions that was quickly lost in continuous light and constant temperature. Under continuous light and daily fluctuating temperatures, larvae could maintain a diel periodicity. However, the amplitude of the periodicity was moderated.     

Effect of the snail Ilyanassa obsoleta (Say) on dynamics of the amphipod Corophium volutator (Pallas) on an intertidal mudflat

We investigated interactions between two dominant invertebrate species of intertidal soft-sediment environments of the northwest Atlantic, the mud snail Ilyanassa obsoleta and the burrowing amphipod Corophium volutator, on a mudflat of the upper Bay of Fundy, Canada. Distribution of I. obsoleta on the mudflat was highly patchy and negatively correlated with density of C. volutator. Manipulation of snail density in cages showed that I. obsoleta influences C. volutator; specifically, increasing density of snails reduced density, increased patchiness in distribution, decreased recapture rates and decreased immigration of C. volutator. Ilyanassa obsoleta seems to be affecting C. volutator through an influence on survival rate and emigration rate, although temporal variation in these effects was observed. Given that both I. obsoleta and C. volutator show a preference for tide pools, an important microhabitat on mudflats, snails might have a profound impact on C. volutator population dynamics.     

Effect of intestinal erythrocyte agglutination on the feeding performance of Triatoma brasiliensis (Hemiptera: Reduviidae)

Triatoma brasiliensis is an important vector of Trypanosoma cruzi in Brazil. The feeding efficiency on its hosts depends on several parameters including the maintenance of the ingested blood at low viscosity, which could be modulated by the anterior midgut (crop) anticoagulant and haemagglutinant activities. In the present study, we characterized T. brasiliensis crop haemagglutination activity and evaluated its importance in the feeding process. Soluble crop contents (SCC) of T. brasiliensis were able to agglutinate rat, mouse and rabbit eryhtrocytes, but had no activity on cattle and Thrichomys apereoides, a rodent species commonly associated with T. brasiliensis in the wild. The haemagglutination was characterized by the immediate formation of several clusters of erythrocytes connected by flexible elastic-like fibers. The feeding efficiency of T. brasiliensis on rat (agglutinated by SCC) was almost double that from T. apereoides (not agglutinated by SCC). The influence of haemagglutination on feeding was confirmed by artificially feeding bugs on a diet composed of cattle or rat erythrocytes. The bugs fed on cattle erythrocytes had lower ingestion rates in comparison to those fed on rats. The results indicate that, in addition to other parameters, haemagglutination brought about by SCC has an important role in the feeding efficiency of T. brasiliensis.     

The feeding behaviour of a sit-and wait-predator,Ranatra dispar (Heteroptera: Nepidae): optimal foraging and feeding dynamics

Summary Nitrogen and phosphorus flow in litterfall and throughfall were studied in two California Quercus species (the evergreen Q. agrifolia and deciduous Q. lobata) before, during, and after an outbreak of the California oak moth, Phryganidia californica. All of the foliage of both oak species was removed by the herbivore during the course of this outbreak. During the outbreak, total N and P flow to the ground more than doubled from Q. agrifolia and increased to a lesser extent from Q. lobata over the previous year. The composition of the litter during the outbreak year shifted so that in Q. agrifolia, almost 70% of the total N and P flow to the ground moved through frass and insect remains, while in Q. lobata, approximately 60% of the N and 40% of the P moved through frass and insect remains. Short-term leaching experiments showed that nitrogen was far more rapidly lost from Phryganidia frass than from leaf litter of either species. These results and the relative frequency of Phryganidia outbreaks suggest that this herbivore has significant effects on the nutrient cycling beneath these trees.     

Palaeobiogeographical provenance, taphonomy, and mode of life of Aturia cubaensis (Cephalopoda, Nautiloidea) from Cainozoic deposits of Chile

The presence of Aturia cubaensis (Lea) is reported from several Cainozoic localities along the central and southern Chilean coast. The shells are very well preserved and the ultrastructure of the shell, especially of the siphuncular tube, of A. cubaensis is described and the function of the siphuncular tube discussed. A. cubaensis shows an interesting distributional pattern in Chile, becoming more frequent towards higher latitudes. It occurs in the Navidad, Ranquil, and Lacui formations of central and southern Chile and the Cameronian Stage of Tierra del Fuego, spanning a time of Eocene-Oligocene to latest Miocene, possibly even earliest Pliocene. Tierra del Fuego is the southernmost record of this species. The preservation of Aturia in all these localities is exceptionally good, no incrustation and microboring is observed in the shells. Post-mortem shell breakage is present, but usually the phramocone is not destroyed. These records contradict either the subtropical to tropical nature of the genus Aturia or existing climatic reconstructions for the southeastern Pacific during the middle to late Cainozoic. A number of southern South American names for nautiloids are synonymized with A. cubaensis: Nautilus maldonadi Philippi, Nautilus caroliameghinoi Ihering, Aturia (Sphenaturia) brueggeni Ihering, Aturia (Sphenaturia) felschi Ihering. Nautilus araucanus Philippi and Nautilus magellanicus Philippi are nomina nuda but presumably also synonyms of A. cubaensis.