Sea surface microlayer and elemental composition in phaeo‐, chloro‐, and rhodophytes in winter and spring

Trace metal or rare earth element (REE) content of marine macroalgae are underexamined and there is a great need for further understanding since macroalgae are used for food and may also be bioindicators of environmental changes. This study, by using high resolution inductive coupled plasma spectrometer in a clean laboratory (class 1000), investigates the trace metal and REE concentrations and composition in the youngest tissue of various species within three algal classes in the Trondheimsfjord, Norway, comprising phaeo‐, chloro‐, and rhodophytes in winter (February) and Spring (May) 2013, with the main focus on phaeophytes. The macroalgae were found in a clear zonation pattern as a function of depth. A significant difference in element concentration and composition was found between the six phaeophyte species along with a significant difference between winter and spring tissue. A zonation depth trend in algal tissue element concentration was also found for the phaeophytes, where the algal species located in both extreme ends (upper vs. lower littoral zone) obtained a lower element concentration than the algae located in the middle part of the littoral zone. This trend seems to result from different algal contact with the metal‐rich sea surface microlayer. The chlorophytes had 5–27 times higher concentration of REE and lead (Pb) than the two other algal classes. Results indicate that the rhodo‐ and chlorophytes are better accumulators than the phaeophytes for several trace metals and REE.     

Responses of cyclic phosphorylation of MAPK-like proteins in intertidal macroalgae after environmental stress

The presence and activation of MAPK-like proteins in intertidal macroalgae is described in the current study. Two MAPK-like proteins of 40 and 42 kDa in size similar to p38 and JNK, of mammalian cells have been identified in six representative species of intertidal macroalgae from the Strait of Gibraltar (Southern Spain), namely in the chlorophytes Ulva rigida and Chaetomorpha aerea, the rhodophytes Corallina elongata and Jania rubens, and the phaeophytes Dictyota dichotoma and Dilophus spiralis. Phosphorylation of MAPK-like proteins was studied during semi-tidal cycles. Analysis of p38-like and JNK-like MAPKs in macroalgae protein extracts was carried out by using specific antibodies against the phosphorylated forms of both MAPKs. Protein blot analysis of samples collected from 2009 to 2011 in natural growing sites on days when either low or high tide occurred at midday, indicated that MAPK-like proteins in all species were highly phosphorylated in response to desiccation imposed by low tide or high irradiance. Phosphorylation of p38-like MAPK always preceded that of JNK-like MAPK. In addition, phosphorylation of MAPKs was fastest in rhodophytes, followed by chlorophytes and then finally phaeophytes. In the first group, phosphorylation was mostly dependent on desiccation, whereas both high irradiance and desiccation were responsible for p38-like and JNK-like phosphorylation in chlorophytes. In phaeophytes, high irradiance was mostly responsible for MAPK-like activation.     

Ontogenetic plasticity of food habits in the Mexican spiny-tailed iguana, Ctenosaura pectinata

Ontogenetic shifts from insect consumption by juveniles to plant consumption by adults are rare in the herbivorous lizard family Iguanidae. My investigations on diet and digestive tract anatomy of the iguanid lizard Ctenosaura pectinata show that this species has an ontogenetic diet shift. Insects were rare in adult diets but constituted 86.5% (by volume) of the food eaten by the smallest juveniles. All age classes ate some plant parts from a range of plant types, but flowers and leaves of legumes were a primarily food source. Non-adult lizards had the widest food niche breadths. Arthropods in the diet of juveniles and immatures covaried seasonally with the decline of arthropod abundance. Several hypotheses could explain this ontogenetic plasticity in diet. I rejected hypotheses that gut structure constrained juveniles to an arthropod diet and that insect consumption was purely an artifact of plant consumption because (1) size-adjusted gut morphology and capacity was similar among age classes, and (2) no food plants sampled had an excessive density of arthropods. I supported an alternative hypothesis that juveniles can eat plants but do not because insects provide a more nutritious diet. This conclusion was based on the observation that the juvenile hindgut is similar to that of herbivorous adults, and the propensity for juveniles to consume primarily, but not exclusively, insects when they were most abundant. The hindgut represents the site of fermentative plant fiber breakdown in many herbivorous lizards. Insect foods can compensate for size-related nutritional needs (energy and protein) and digestive limitations in juveniles. Opportunistic feeding to maintain a broad diet might help juvenile and immature lizards through high-predation-risk growth periods by reducing searching costs, increasing nutritional and energetic gains due to associative effects, and increasing new food exposure. Received: 20 January 1999 / Accepted: 25 January 2000     

The intertidal algal flora of Isipingo Beach,Natal, South Africa,and its phycogeographical affinities

The intertidal seaweed flora of Isipingo Beach, Natal, is described. Isipingo Beach lies on the sub-tropical east coast of southern Africa and is the only east coast locality studied in detail by pioneering biogeographers. A total of 172 species (37 chlorophytes, 26 phaeophytes and 109 rhodophytes) are recorded. A phycogeographical analysis of 124 species with sufficiently documented distributions, shows that 69% are warm water species also known from the tropical coasts of Mozambique, Tanzania and Kenya. The phycogeographical affinity of the Isipingo flora is certainly with sub-tropical and tropical floras.     

Seasonal Variation in the Chemical Composition of Tropical Australian Marine Macroalgae

The proximate chemical composition (ash, soluble carbohydrate, lipid and protein) was determined in 30 common species of tropical Australian marine macroalgae from Darwin Harbour (12^∘26′S, 130^∘51′E), in summer (hot and wet) and winter (cool and dry). There was a wide diversity of species in both seasons (19 species in summer and 20 species in winter). In most species, the major component was soluble carbohydrate (chlorophytes range 2.5–25.8% dry weight (dw), phaeophytes range 8.4–22.2% dw, rhodophytes range 18.7–39.2% dw) with significantly higher (p < 0.05) percentages only in winter season rhodophytes. Highest percentages of protein were found in rhodophytes collected in the summer (range 4.8–12.8% dw), with significantly lower percentages (p < 0.05) during winter. All species had lipid contents within the range 1.3–7.8% dw, with highest percentages in summer phaeophytes, but no significant differences between species or season. Most species had moderate to high ash contents (24.2–89.7% dw), with the highest percentages during summer. Compared with summer samples, macroalgae collected in winter had higher energy value and slightly lower percentages of inorganic matter. The variation of algal groups and chemical composition may influence the availability of the food source for the majority of herbivores, which in turn is likely to effect their ecology and community structure.     

Cultural Estimation of Yeasts on Seaweeds

Five per cent suspensions of freshly harvested seaweeds were used as an inoculum to develop a selective medium for epiphytic yeasts. Conditions for satisfactory yeast growth and visualization as red colonies on membrane filters were obtained by supplementing a basal glucose-Trypticase-yeast extract-agar at pH 7.0 with 100 mg each of chloramphenicol and 2,3,5-triphenyl tetrazolium chloride per liter. Maximal counts were obtained by triturating the algae in prechilled (4 C) seawater with a blender for 2 to 5 min. Inhibitory phenolic materials released from phaeophytes during this process were removed with a modified Cholodny filtration. A preliminary survey indicated that yeasts were epiphytic on all nine species of seaweeds and that maximal populations occurred on the chlorophytes and rhodophytes especially during the periods of warmer water.     

The marine algae of Hluleka (Transkei) and the warm temperate/sub-tropical transition on the east coast of southern Africa

The marine flora of the transition region between the warm temperate south coast and sub-tropical east coast of southern Africa is very poorly documented. The seaweeds of Hluleka Nature Reserve, centrally placed along this transition, are described. 178 species (120 rhodophytes, 33 chlorophytes and 25 phaeophytes) are recorded, including 28 new records for the region, and a new combination,Tiffaniella schmitziana (Barton) nov. comb. A biogeographical analysis of those species whose distribution is sufficiently known reveals that 65% are warm water species, also occurring in tropical seas. Hluleka is thus towards the warmer end of the transition, and the major discontinuity is sharply defined, occurring in the ca 130 km of coastline between Hluleka and the mouth of the Kei River. It is probable that a rapid temperature gradient along this stretch of coast (change of 2°C in annual mean) is responsible for the discontinuity.     

Riparian contributions to the diet of terapontid grunters (Pisces: Terapontidae) in wet–dry tropical rivers

The diets of terapontid assemblages in 22 catchments across Australia's wet–dry tropics were investigated in relation to the direct use of terrestrial‐riparian inputs, as well as the role of ontogeny and morphology in mediating consumption of allocthonous material. The diet of several species was restricted almost entirely to instream trophic resources throughout their life history. In contrast, ontogenetic diet shifts towards increasing consumption of terrestrial prey types were a prominent feature of the dietary ecology of some terapontids, with collective allocthonous dietary items making a significant contribution (up to 42%) to diet in larger size classes of several species. For those species consuming terrestrial‐riparian material in their diet, terrestrial invertebrates were the most common prey item; however, terrestrial vegetation, principally riparian fruits, and terrestrial vertebrates were also important dietary inclusions in the larger size classes of particular species. A large mouth gape was the morphological feature most strongly associated with consumption of terrestrial food resources within the Terapontidae. Results indicate that the direct consumption of terrestrially derived food sources in northern Australian aquatic systems may be more important than previously asserted, and that additional research is required to better clarify the role of terrestrial subsidies to these ecosystems.     

Feeding ecology of the Iberian cyprinid Barbus bocagei Steindachner, 1865 in a lowland river

Patterns of food resource utilization by Barbus bocagei in a lowland river in the central part of the Iberian Peninsula are presented and discussed. Focal points include feeding activity, diet composition and seasonal and ontogenetic diet shifts. Striking features of overall feeding pattern of barbel are its continuous feeding activity, bottom habits, high consumption of detritus and dipteran larvae and narrow diet breadth. Seasonal changes in food resource availability elicited changes in food utilization patterns, revealing a trend to more generalist feeding during spring. Barbel increase consumption of plant material and large prey during ontogeny, but overlap in prey resource utilization between size classes is high. The versatility of barbel foraging behaviour may be an important feature in its exploitation of Iberian lotic systems.     

Age-Sex Analysis of Activity Budget,Diet, and Positional Behavior in <Emphasis Type="Italic">Alouatta caraya</Emphasis> in an Orchard Forest

Howlers (Alouatta spp.) spend more than half of the daytime resting and their diet consists predominantly of leaves. Associated with a general strategy of energy conservation, their positional behavior is characterized by quadrupedalism as the major locomotor mode, and sitting as the most common resting and feeding posture. However, researchers have sparse information on the degree to which age-sex classes fit the generic trends and the influence of habitat structure on them. We compare the activity budget, dietary composition, and positional behavior by age-sex or age classes in a group of black-and-gold howlers (Alouatta caraya) in a small orchard forest. We collected 26,474 behavioral records via instantaneous scan sampling over 1 yr. The main activity was resting (56%) and the diet comprised mainly leaves (82%); sitting was the most adopted feeding (61%) and resting (52%) posture, and walking was the most prevalent locomotor mode (38%). There are age-sex differences for all major behaviors. Whereas resting tended to increase with body size, moving decreased. We observed no difference in the consumption of major plant parts. There were ontogenetic differences in most positional behaviors. Sitting increased from infants to adults during feeding, whereas the opposite occurred for bridging and hanging. During resting, infants curled more and lay less than the other classes did, whereas adults engaged in more sitting. Adults and subadults walked more than individuals of other ages did; infants climbed and bridged more than others did; and, there were opposing trends in leaping and descending. Habitat structure is a partial explanation of the locomotor behavior of black-and-gold howlers.     

Seaweed survival after consumption by the greenbeak parrotfish,Scarus trispinosus

We assessed the survival of seaweed (macroalgae and cyanobacteria) after consumption by the greenbeak parrotfish, Scarus trispinosus, in northeastern Brazil. Samples of S. trispinosus feces were collected, inoculated on filter paper, and kept in the laboratory and field for 60 and 30 d, respectively. Comparisons of samples inoculated with feces to those without (controls) revealed a marked increase in the abundance and diversity of seaweed in samples inoculated with feces in both laboratory and field experiments. These results were consistent between summer and winter, although the seaweed species differed. A total of one cyanobacterium and 16 macroalgal taxa (nine rhodophytes, five heterokontophytes, and two chlorophytes) were recorded in the inoculated samples. Rhodophyta also presented the highest abundance across treatments, possibly because of their higher resistance to parrotfish digestion, greater ingestion, or both. The survival of cyanobacteria and macroalgae after consumption by S. trispinosus suggests that parrotfishes may contribute to seaweed dispersion on tropical reefs.

     

黄海中部高眼鲽的摄食及随体长的变化

对2004年1月-2005年10月在黄海中部采集的622尾高眼鲽样品的胃含物进行分析.结果表明：高眼鲽摄食的食物种类包括11类38种,其中甲壳类和瓣鳃类为优势饵料类群,共占食物相对重要性指数百分比的99%;食物中的优势饵料种类为太平洋磷虾、脊腹褐虾和樱蛤.与20世纪80年代相比,黄海高眼鲽的摄食强度下降,食物组成发生了较大的变化;鱼类不再是优势饵料类群,鳀鱼在食物中所占的比例明显下降.通过聚类分析和列联表检验等方法对高眼鲽摄食随体长的变化进行研究,结果表明：体长在51～370 mm范围内的高眼鲽的摄食强度没有显著的体长变化,但不同体长组摄食的食物种类有一定差异.＜119 mm的主要以磷虾类和底层虾类为食;体长在120～199 mm的除以磷虾类和底层虾类为主要食物外,还摄食相当比例的瓣鳃类和鱼类;＞200 mm的则主要摄食底层虾类和鱼类,磷虾类所占比例减小.     

A juvenile skull of Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia), and implications for cranial ontogeny,phylogeny, and taxonomy in ornithopod dinosaurs

A juvenile skull of Dysalotosaurus lettowvorbecki, a basal iguanodontian from the Middle Dinosaur Member (Kimmeridgian) of the Tendaguru Beds (Tanzania), is described and reconstructed in detail. Further preparation and computed tomography scans have uncovered additional and formerly unknown skull elements, especially of the lower jaw. The reconstruction of the skull reveals ontogenetic differences to earlier reconstructions, which were based on specimens of relatively older individuals. The most notable ontogenetic changes in Dysalotosaurus are a relative lengthening of the muzzle, a decrease in the relative size of the orbit, and a straightening of the posterior skull roof. Additionally, ontogenetic variations were found in many single elements of the skull, all of which reflect the three main tendencies described above. Furthermore, there might have been an ontogenetic change in the diet, from omnivorous juveniles to fully herbivorous adults. The results of this study will help to evaluate ontogenetic stages in other ornithopods, and will shed light on a crucial stage of ornithopod evolution that culminated in the highly specialized and diverse hadrosaurs of the Cretaceous. Many of the evolutionary changes seen in this lineage can be attributed to peramorphism, and probably reflect a perfection of the adaptation towards an obligatory herbivorous diet. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 366–396.     

Why can't young fish eat plants? Neither digestive enzymes nor gut development preclude herbivory in the young of a stomachless marine herbivorous fish

Most young fishes lack the ability to function as herbivores, which has been attributed to two aspects of the digestive system: elevated nitrogen demand and a critical gut capacity. We compared the digestive morphology and biochemistry of two size classes of the marine herbivore Hyporhamphus regularis ardelio, pre-ontogenetic trophic shift (pre-OTS, <100mm) and post-ontogenetic trophic shift (post-OTS, >100mm), to determine what limits the onset of herbivory and how their digestive processes fit with current models of digestion. Two gut-somatic indices comparing gut length to body length (relative gut length) and body mass (Zihler's Index) demonstrated a significant decrease (RGL 0.59→0.49, P<0.01; ZI 3.24→2.44, P<0.01) in gut length relative to body size. There was little difference in enzyme activity between the two classes, with juveniles showing similar levels of carbohydrase and lipase and less protease compared with adults, indicating that juveniles did not preferentially target nitrogen and were as capable of digesting an herbivorous diet. These findings suggest that herbivory in this fish is not limited by the function of the post-oesophageal digestive tract, but rather the ability of the pharyngeal mill to mechanically process plants. Our findings offer partial support for the current model of stomachless digestion, indicating that further refinement may be necessary.     

Digestive enzyme activities in herbivorous and carnivorous prickleback fishes (Teleostei: Stichaeidae): ontogenetic, dietary, and phylogenetic effects

We measured the activities of eight digestive enzymes in four species of herbivorous and carnivorous prickleback fishes and determined the effects of ontogeny, diet, and phylogeny on these enzyme activities. Of the four species, Cebidichthys violaceus and Xiphister mucosus shift to a more herbivorous diet as they grow (> or =45 mm SL [standard length]), whereas Xiphister atropurpureus and Anoplarchus purpurescens remain carnivores throughout life. Digestive enzyme activities of small (30-40 mm SL) carnivorous juveniles were compared with those of larger (60-75 mm SL) wild-caught juveniles that had consumed a natural diet and larger (60-75 mm SL) juveniles raised on a high-protein animal diet. Cebidichthys violaceus and both species of Xiphister showed ontogenetic changes in digestive enzyme activities, whereas A. purpurescens did not. Despite dietary differences between X. atropurpureus and X. mucosus, these sister taxa displayed the most similar digestive enzyme activities from ontogenetic and dietary perspectives (high alpha-amylase and lipase and low trypsin and aminopeptidase activities), and both were more similar to C. violaceus, a member of the same largely herbivorous clade, than either was to A. purpurescens, a member of an adjacent, carnivorous clade. The results support the hypothesis that phylogeny influences digestive enzyme activities in these fishes. Anoplarchus purpurescens, a carnivore with a diverse diet, showed great plasticity in enzyme activity, especially trypsin and aminopeptidase, which were elevated in this species to the highest level among the four species after consuming the high-protein diet. These results support the hypothesis that fishes with relatively broad diets can modulate digestive enzyme activities in response to changes in dietary composition.     

Transitional ecological requirements for early juveniles of two sympatric stichaeid fishes,Cebidichthys violaceus andXiphister mucosus

Synopsis The distribution patterns, diets, and substratum (refuge) requirements of early juveniles of two sympatric stichaeid fishesCebidichthys violaceus andXiphister mucosus, were investigated in a rocky intertidal habitat at Diablo Canyon, California. Monthly investigations were conducted at low tide for four consecutive months, to assess ontogenetic differences in distribution, diet, and refuge requirements within and between the two species. Distinct differences in vertical zonation were exhibited by both stichaeids throughout the study. Interspecific zonation patterns were similar to those recorded for adults of both species. Diet analyses showed that early juveniles of both stichaeids were zooplanktivorous, differing markedly from the primarily herbivorous diets of adults. Changes in diet were largely due to the selection of larger prey taxa as both fishes, and their mouth size, grew over the study period. Predation by both fishes on water-column planktors (calanoid copepods, zoea and polychaete larvae) was greatest following initial intertidal settlement and habitat establishment by early juvenile fishes. Greater dependence on substrate-oriented and/or benthic prey (harpacticoid copepods, gammarid amphipods and mysid shrimp) was exhibited by both fishes as they grew in size. Affinities for sand, gravel, and pebbles during monthly field surveys were similar for both species throughout the study. As the fishes grew, their substratum preferences changed in relation to the substrata which provided the best refuge. Results from laboratory experiments indicated that young stichaeids select very specific substrata based on fish age (size) and substratum suitability (i.e. adequate refuge). Similarities in diet and substratum preferences, and changes in those preferences over time, appear to be the result of morphological similarities (body size and shape and mouth gape) for both species at a given age.     

Hindgut fermentation in three species of marine herbivorous fish

Symbioses with gut microorganisms provides a means by which terrestrial herbivores are able to obtain energy. These microorganisms ferment cell wall materials of plants to short-chain fatty acids (SCFA), which are then absorbed and used by the host animal. Many marine herbivorous fishes contain SCFA (predominantly acetate) in their hindgut, indicative of gut microbial activity, but rates of SCFA production have not been measured. Such information is an important prerequisite to understanding the contribution that gut microorganisms make in satisfying the energy needs of the fish. We have estimated the rates of acetate production in the gut of three species of temperate marine herbivorous fish from northeastern New Zealand: Kyphosus sydneyanus (family Kyphosidae), Odax pullus (family Odacidae), and Aplodactylus arctidens (family Aplodactylidae). Ex vivo preparations of freshly caught fish were maintained with their respiratory and circulatory systems intact, radiolabeled acetate was injected into ligated hindgut sections, and gut fluid was sampled at 20-min intervals for 2 h. Ranges for acetate turnover in the hindguts of the studied species were determined from the slope of plots as the log of the specific radioactivity of acetate versus time and pool size, expressed on a nanomole per milliliter per minute basis. Values were 450 to 570 (K. sydneyanus), 373 to 551 (O. pullus), and 130 to 312 (A. arctidens). These rates are comparable to those found in the guts of herbivorous reptiles and mammals. To determine the contribution of metabolic pathways to the fate of acetate, rates of sulfate reduction and methanogenesis were measured in the fore-, mid-, and hindgut sections of the three fish species. Both rates increased from the distal to proximal end of the hindgut, where sulfate reduction accounted for only a small proportion (<5%) of acetate methyl group transformed to CO(2), and exceeded methanogenesis from acetate by >50-fold. When gut size was taken into account, acetate uptake from the hindgut of the fish species, determined on a millimole per day per kilogram of body weight basis, was 70 (K. sydneyanus), 18 (O. pullus), and 10 (A. arctidens).     

A pilot study on the ontogeny of digestive physiology in Japanese macaques (Macaca fuscata)

An assumption based on the Jarman–Bell principle suggests a positive relationship between body size and the digestive efficiency in animals, where smaller animals are less effective at digesting fibrous food due to shorter digesta passage. To examine the effect of body size within a species and explore a potential physiological background of ontogenetic diet shifts, we measured food intake, digestibility, digesta passage and gut fill in nine Japanese macaques, including three juveniles/subadult animals. Although these three showed a comparable digestive efficiency as the older animals on a low-fiber diet, they did not achieve the long retention times of adults in spite of similar levels of indigestible food intake and gut capacity. While the limited sample size would not allow generalized conclusions on ontogenetic digestive development in primates, this study suggests additional, yet unexplored effects other than food intake, digestion and gut capacity on digesta retention during ontogeny.     

Ontogenetic Development of the Gastrointestinal Microbiota in the Marine Herbivorous Fish Kyphosus sydneyanus

Molecular techniques were used to investigate the composition and ontogenetic development of the intestinal bacterial community in the marine herbivorous fish Kyphosus sydneyanus from the north eastern coast of New Zealand. Previous work showed that K. sydneyanus maintains an exclusively algivorous diet throughout post-settlement life and passes through an ontogenetic diet shift from a juvenile diet which is readily digestible to an adult diet high in refractory algal metabolites. Terminal restriction fragment length polymorphism (T-RFLP) analysis was used to investigate the relationship between bacterial community structure and fish size. Bacterial diversity was higher in posterior gut sections than anterior gut sections, and in larger fish than in smaller fish. Partial sequencing of bacterial 16S rDNA genes PCR amplified and cloned from intestine content samples was used to identify the phylogenetic affiliation of dominant gastrointestinal bacteria. Phylogenetic analysis of clones showed that most formed a clade within the genus Clostridium, with one clone associated with the parasitic mycoplasmas. No bacteria were specific to a particular intestinal section or size class of host, though some appeared more dominant than others and were established in smaller fishes. Clones closely related to C. lituseburense were particularly dominant in most intestine content samples. All bacteria identified in the intestinal samples were phylogenetically related to those possessing fermentative type metabolism. Short-chain fatty acids in intestinal fluid samples increased from 15.6 ± 2.1 mM in fish <100 mm to 51.6 ± 5.5 mM in fish >300 mm. The findings of this study support the hypothesis that the ontogenetic diet shift of K. sydneyanus is accompanied by an increase in the diversity of intestinal microbial symbionts capable of degrading refractory algal metabolites into short-chain fatty acids, which can then be assimilated by the host.     

Natural born killers: an invasive amphipod is predatory throughout its life-history

Introduced predators can have profound impacts on prey populations, with subsequent ramifications throughout entire ecosystems. However, studies of predator–prey interaction strengths in community and food-web analyses focus on adults or use average body sizes. This ignores ontogenetic changes, or lack thereof, in predatory capabilities over the life-histories of predators. Additionally, large individual predators might not be physically capable of consuming very small prey individuals. Both situations are important to resolve, as native prey may or may not therefore experience ontogenetic or size refuges from invasive predators. Here, we find that the freshwater amphipod invader, Gammarus pulex, is predatory throughout its development from juvenile through to adult. All size classes collected in the field had a common prey, nymphs of the mayfly Baetis rhodani, in their guts. In an experiment with predator, prey and experimental arenas scaled for body size, G. pulex juveniles and adults consumed B. rhodani in all size-matched categories. In a second experiment, the largest G. pulex individuals were able to prey on the smallest B. rhodani. Thus, the prey do not benefit from any ontogenetic or size refuge from the predator. This corroborates with the known negative population abundance relationships between this invasive predator and its native prey species. Understanding and predicting invasive predator impacts will be best served when interactions among all life-history stages of predator and prey are considered.