Variety Of Prey Items Research Articles

Haul-out patterns of the Baltic grey seal (Halichoerus grypus) in the suburbs of a metropolis

In this study, we investigated the haul-out patterns of the Baltic grey seal in the coastal area adjacent to the metropolitan city, Saint Petersburg, during the ice-free seasons of 2017-2022. Grey seals occupied stony banks near Kotlin Island, in the easternmost part of the Gulf of Finland. The censuses were carried out from the island shore during evening hours. The number of seals reached 70 during the survey. Contrary to the common trend reported in similar studies, the annual minimum in seal abundance (May and June) coincided with the peak of moulting. Active use of the haul-out site was observed between July and November, implying that eastward movements of the grey seals take place in the Gulf of Finland in the post-moulting period. Wind speed and sea state interfered with the seal hauling out throughout the year, whereas the relationship with air temperature varied seasonally. Cloud cover, atmospheric pressure, wind direction and sea level had no impact on the seal number, though the fluctuations in sea level reduced the haul-out space. The tendency of the seals to haul out towards and after the sunset was determined. The most frequent sources of human disturbance were light planes (0.45 ± 0.12 confidence interval, per count) and powerboats (0.41 ± 0.14 confidence interval, per count), but only the powerboats significantly decreased the seal number. We found that the seals used the banks concurrently with seabirds. The area of Kotlin Island presumably attracts the seals by the diversity of prey items in the estuary of the Neva River. Establishing of a marine protected area and physical marking of the water space around the haul-out site are recommended.

Reproductive biology, length-weight relationship and diet of co-occurring butterfly rays, Gymnura poecilura and Gymnura zonura, in Malaysian waters.

Recent IUCN assessments had resulted in up listing of the status of butterfly rays due to concerns of overfishing, but inadequate biological understanding of these rays prevents meaningful conservation and management measures. Therefore, this study was undertaken to address knowledge gaps in the reproductive biology and diet of longtail butterfly ray (Gymnura poecilura) and zone tail butterfly ray (Gymnura zonura) in Malaysian waters. From surveys of landing sites and fish markets from years 2017 to 2022, size (disc width, DW), weight and maturity were recorded, and stomachs were collected from 94 G. poecilura (N=39 females and 55 males) and 20 G. zonura (N=10 females and 10 males) specimens. The length-weight relationships were significantly different between sexes for G. poecilura. The size at maturity (DW50) was estimated to be 476.0 mm (females), 385.0 mm (males) for G. poecilura and 442.0 mm (combined) for G. zonura. The number of embryos ranged from 1 to 6, and the embryo size was between 73.90 to 130.44 mm DW. Dietary analysis of stomach contents revealed that fish prey was dominant in both G. poecilura [94.4% Index of Relative Importance (IRI)] and G. zonura (100% IRI). Ontogenetic shift was seen in G. poecilura that fed on more variety of prey items, including shrimps, squids and crabs with an increase in body size. Both species co-occur all along coastal Malaysia although G. zonura is rarely encountered from fisheries surveys along the Strait of Malacca. Given similar habitat associations and dietary habits, G. poecilura may be able to outcompete G. zonura across their shared habitat range. The validity of G. japonica and G. micrura records in Malaysia remains questionable and requires future investigation.

A vertebrate, the fence skink, is a common but relatively low-quality prey for an invertebrate predator, the redback spider

Many predators feed on a diversity of prey items and the traits of these prey can affect their quality for predators. While invertebrate predators most often feed on other invertebrates, numerous studies have documented spiders and other predatory arthropods feeding on vertebrates. The goal of this study was to examine the frequency of fence skinks, Cryptoblepharus virgatus, in the diet of redback spiders, Latrodectus hasselti, and to measure the amounts and ratio of nutrients that spiders extracted from fence skinks compared to representative high-quality (i.e., locust) and low-quality (i.e., beetle) arthropod prey. In field surveys, fence skinks represented 8% of individual prey items and 17% of the biomass of prey captured by redback spiders. In feeding trials, spiders consumed a lower total dry mass and mass of lipid when feeding on skinks relative to both arthropod prey and the lowest mass of protein when feeding on beetles. In terms of feeding efficiency, spiders were most efficient at extracting dry mass, lipid and protein from locusts and least efficient at extracting nutrients from skinks (lipid) or skinks and beetles (dry mass and protein). There were also differences in trace element consumption between spiders feeding on skinks versus locusts. These results suggest that skinks are a relatively low-quality prey. The frequency of skinks in the diet of these urban redback spiders is likely a consequence of the abundance of skinks in this habitat, similar microhabitat selection by spiders and skinks, and relatively indiscriminate predation by spiders. Further work is needed to examine the relative quality of other vertebrates for invertebrates and if other traits such as predator feeding mode affects the relative quality of vertebrates as prey.

Prey preference of Stenostomum cf. virginianum Nuttycombe, 1931 (Platyhelminthes); a case study in the littoral zone of a tropical reservoir

In aquatic systems, littoral zones provide heterogeneous environments where turbellarians can reach densities of up to 40,000 ind. m−2 . To reach such high densities turbellarians need to feed on a variety of prey items. Very little information is available on the feeding ecology of Stenostomum spp. in natural conditions. The objective of this work was to determine the food preference of Stenostomum virginianum based on the density and physical characteristics of prey present in the littoral zone of the Benito Juárez reservoir (Mexico) associated with the macrophyte Egeria densa by analyzing the gut content of the turbellarians. We found that 58% of turbellarians contained rotifers in their gut. The thickness of rotifer lorica did not limit the selection, but the size and availability of the species did. The preferred rotifer prey included Trichocerca porcellus, Lecane closterocerca and Colurella obtusa. This work demonstrates that turbellarians feed on rotifers but are often overlooked in freshwater trophic analyses. They need be considered together with other invertebrate predators such as Asplanchna and cyclopoid copepods because of their impact on rotifer communities in tropical and temperate water bodies.

Multiplex PCR targeting lineage‐specific SNPs: A highly efficient and simple approach to block out predator sequences in molecular gut content analysis

Abstract Food webs form the basis of biological communities, though empirical research has been hindered by difficulties in quantifying interactions. Metabarcoding from predator gut content extractions with universal primers promises to provide simple and rapid insights into food web interactions. However, the highly overabundant predator DNA often completely out‐competes that of the digested prey DNA during PCR, impeding the ability to assess the abundance and diversity of prey items. Focusing on the issue of overabundance of predator DNA amplified by a commonly used COI primer pair, we use predator lineage‐specific SNPs at the 3’‐end of PCR primers to selectively block out predators from amplification. While this approach largely prevents predator amplification, it retains high taxonomic versatility for prey lineages. We introduce a novel multilocus assay, targeting four nuclear and mitochondrial rDNA markers, and test our approach in a diverse set of spiders from 12 families. We estimate the recovered prey DNA proportions and compare the taxonomic composition of prey communities between markers. Using a feeding experiment, we also explore recovery of prey DNA over time. While commonly used COI primers yield low and very unpredictable amounts of prey DNA, our assay allows for a considerable and consistent prey enrichment across all tested species. The recovered prey's taxonomic composition is comparable between markers and supports results acquired by COI. The new marker set can be amplified in a simple multiplex PCR, considerably reducing the necessary workload. Our multilocus approach allows the generation of an unprecedented amount of prey data at low cost and effort. Lineage‐specific PCR is taxonomically versatile and could readily be adapted to any prey–predator interaction, opening up the opportunity for community‐wide studies on food web interactions.

Predators buffer the effects of variation in prey nutrient content for nutrient deposition

Predator feeding behavior and digestion regulate the flow of nutrients through ecosystems by determining the fate of prey nutrients. Most predators feed on a diversity of prey items, which differ widely in traits including their nutrient content. Yet, relatively little is known of the mechanisms through which variation in prey nutrient content affects the form by which nutrients are deposited into the environment. The overall goal of this study was to test how variation in the nutrient content of prey affected the fate of nutrients following predation by an arthropod carnivore, the Carolina wolf spider Hogna carolinensis. We manipulated the macronutrient content of prey by varying the diet on which crickets were fed to produce prey treatments that differed in lipid and protein content. Nutrients were measured as both macronutrients and elements in prey and elements in excreta. We found that there was no effect of diet treatment on the amounts of elements or macronutrients in prey carcasses and excreta despite significant variation in the nutrient content of those prey. This is in contrast to studies of some aquatic systems where mass balance by consumers results in variation in excreta content depending on the nutrient content of food. Wolf spiders assimilated the majority of prey nutrients and deposited relatively small and similar amounts of nutrients following feeding. Hence, while prey can vary widely in nutrient content, our findings suggest that this variation has little effect on the amounts of nutrients deposited by predators.

Aspects of the biology and life history of largespot pompano, Trachinotus botla, in South Africa

Trachinotus botla is an important recreational surf zone-dependent fish species distributed in the Indo-west Pacific from South Africa to Australia. In South Africa it is restricted to the northern KwaZulu-Natal coast. Biological investigations revealed that it is a fast growing species that attains a maximum age of ~7 years. Males and females sexually matured in their third year. It has a protracted summer spawning season with evidence of serial spawning behaviour. T. botla is an opportunistic predator with a generalist diet, with fish feeding on a wide variety of prey items particularly those that are temporally ‘superabundant’. Small fish fed predominantly on copepods and terrestrial insects, whereas larger fish consumed bivalves and crabs. Teleosts, primarily engraulids, were important components to the diet of fish of all sizes. An ontogenetic dietary shift was observed just after sexual maturity (~300-mm fork length) that is possibly linked to a change in habitat preference with larger fish foraging on deeper reefs.

Distribution, feeding habits and morphology of killer whales Orcinus orca in the Caribbean Sea

Abstract Killer whales Orcinus orca are found in all oceans of the world, but most of our knowledge on the species comes from studies conducted at higher latitudes. Studies on killer whales in the Caribbean have been scarce. We compiled 176 records of killer whales from the Caribbean, including 95 previously unreported records and 81 records recovered from the literature, consisting of 27 capture or kill records, 4 stranding records and 145 sighting records. Our results indicate that killer whales are widespread in the Caribbean Sea and can be found year‐round in the region. Mean group size was 3.7 animals. A diversity of prey items was recorded, including sea turtles and marine mammals and possibly fish. We cannot exclude ecotype or morphotype‐specific dietary specialization in the Caribbean population. A preliminary morphological analysis of 10 characters in 52 individuals from 21 different groups suggests that Caribbean killer whales do not represent any of the four Antarctic and subantarctic types, type 1 from the northwest Atlantic, or ‘resident’ and ‘transient’ killer whales from the northwest Pacific. Some Caribbean killer whales share a combination of characters typical of type 2 in the North Atlantic, whereas others share those typical of ‘offshore’ killer whales in the northwest Pacific. The significance of this is unclear. Comparison of Caribbean killer whales to previously described morphotypes and ecotypes is hampered by the lack of detailed, quantitative data on variation within other types, as well as by the lack of comparisons of genetic diversity. Our study adds to the growing knowledge of the diversity of killer whales worldwide but underscores that additional research is warranted in the tropics.

Effect of Rhabdias pseudosphaerocephala on prey consumption of free-ranging cane toads (Rhinella marina) during Australian tropical wet seasons

The development of biological control measures to reduce the impact of invasive species is a desired goal. Rhabdias species have recently been advocated as biological control agents for invasive anurans. This study describes a field-based approach to support laboratory results on the potential impact of the lung nematode Rhabdias pseudosphaerocephala on the prey consumption of its host, the invasive cane toad (Rhinella marina, Bufonidae). Toads were sampled from various populations in the Wet Tropics of Australia during the wet seasons of 2010 and 2012. Consumed prey items were counted in 212 cane toads and identified to class and order levels and the number of lung nematodes was counted for each toad. The number of R. pseudosphaerocephala in free-ranging cane toads affected negatively the diversity of prey items consumed, but was not related to the number of prey items or the number of ants consumed. The results suggest that infection of free-ranging cane toads by the lung nematode reduces their range of prey items. Possible reasons could be a reduced locomotor activity resulting in changes of foraging modes of infected toads which was reported from some laboratory trials. Infection of cane toads by R. pseudosphaerocephala may therefore have the potential to alter the impact of cane toads on invertebrate communities and their competition for food resources with native Australian anurans.

Lake Whitefish Feeding habits and condition in Lake Michigan

Lake whitefi sh (Coregonus clupeaformis) have experienced declines in condition in some areas of the Great Lakes. The hypothesis tested was that condition—in terms of relative weight, percent lipid and docosahexaenoic acid (DHA)—was greater in regions where larger proportions of high quality prey (e.g., Diporeia) were included in the diet. Samples of spawning lake whitefi sh from four regions around Lake Michigan (northwest, Naubinway, Elk Rapids and southeast) had distinct mean carbon and nitrogen stable isotope signatures. Lake whitefi sh may be using a variety of prey items, especially the Naubinway population where fi sh occupy the largest stable isotopic niche space. However, trophic niche width inferred from stable isotopes did not vary among regions. Relative weight was highest in the southeast and lowest for all northern regions. The mean measured lipid from lake whitefi sh dorsal, skinless, muscle biopsies were highest for northwest fi sh. DHA was signifi cantly different among regions, with high mean values in Elk Rapids and the northwest. No correlations were found between stable isotope measures and condition metrics. The results suggest that lake whitefi sh are coping with declining Diporeia abundances by feeding on alternate prey. Overall results do not substantiate the hypothesis of a relationship between condition and prey use, although lake whitefi sh from Elk Rapids and the northwest had high quality prey and good condition.

Life history traits of the sand stargazerDactyloscopus tridigitatus(Teleostei: Blennioidei) from south-eastern Brazilian coast

Individuals of the sand stargazerDactyloscopus tridigitatuswere collected monthly over a period of one year in an urban-sandy beach in south-eastern Brazil. We sampled 57 males, 64 females, and 6 juveniles, indicating a sex-ratio of approximately 1:1. Total length and weight did not differ significantly between sexes, showing no sexual dimorphism in size. The growth ofD. tridigitatuswas highly positive allometric and the correlation coefficient was significant for both sexes. Males were observed carrying two egg clumps under each enlarged pectoral fin during most of the year. In contrast, females showed a more restricted reproductive period, concentrated during the austral rainy season. The number of eggs in each clump carried by males did not differ significantly from the number of vitellogenic oocytes of mature females. The number of eggs carried by males was weakly correlated to male total length; however, female fecundity was strongly correlated to female total length.Dactyloscopus tridigitatusconsumed a high variety of prey items, including crustaceans, annelids, molluscs, teleosts, insects and eggs. Isopods were the most important component of the diet followed by polychaetes and amphipods. We concluded that promiscuous breeding, paternal care behaviour and invertivorous feeding habits seem to be important traits for the species' success in the studied habitat.

Parasite communities and feeding ecology of the European sprat (Sprattus sprattus L.) over its range of distribution

The metazoan parasite fauna and feeding ecology of 165 Sprattus sprattus (L., 1758) was studied from different geographic regions (Baltic Sea, North Sea, English Channel, Bay of Biscay, Mediterranean Sea). A total of 13 metazoan parasite species were identified including six Digenea, one Monogenea, two Cestoda, two Nematoda and two Crustacea. Didymozoidae indet., Lecithocladium excisum and Bomolochidae indet. represent new host records. The parasite species richness differed according to regions and ranged between 3 and 10. The most species-rich parasite fauna was recorded for sprats from the Bay of Biscay (North Atlantic), and the fishes from the Baltic Sea contained the lowest number of parasite species. More closely connected geographical regions, the North Sea, English Channel and Bay of Biscay, showed more similar parasite component communities compared with more distant regions. From the examined stomachs of S. sprattus, a total of 11 different prey items were identified, including Mollusca, Annelida, Crustacea and Tunicata. The highest number of prey organisms belonged to the crustaceans. The variety of prey items in the stomach was reflected by the parasite community differences and parasite species richness from the different regions. The feeding ecology of the fish at the sampled localities was responsible for the observed parasite composition and, secondarily, the zoogeographical distribution of the parasites, questioning the use of the recorded sprat parasites as biological indicators for environmental conditions and change.

Contribution of pitcher fragrance and fluid viscosity to high prey diversity in a Nepenthes carnivorous plant from borneo

Mechanisms that improve prey richness in carnivorous plants may involve three crucial phases of trapping:attraction, capture and retention. Nepenthes rafflesiana var. typica is an insectivorous pitcher plant that is widespread in northern Borneo. It exhibits ontogenetic pitcher dimorphism with the upper pitchers trapping more flying prey than the lower pitchers. While this difference in prey composition has been ascribed to differences in attraction,the contribution of capture and retention has been overlooked. This study focused on distinguishing between the prey trapping mechanisms, and assessing their relative contribution to prey diversity. Arthropod richness and diversity of both visitors and prey in the two types of pitchers were analysed to quantify the relative contribution of attraction to prey trapping. Rate of insect visits to the different pitcher parts and the presence or absence of a sweet fragrance was recorded to clarify the origin and mechanism of attraction. The mechanism of retention was studied by insect bioassays and measurements of fluid viscosity. Nepenthes rafflesiana was found to trap a broader prey spectrum than that previously described for any Nepenthes species,with the upper pitchers attracting and trapping a greater quantity and diversity of prey items than the lower pitchers. Capture efficiency was low compared with attraction or retention efficiency. Fragrance of the peristome,or nectar rim,accounted mainly for the observed non-specific, better prey attraction by the upper pitchers, while the retentive properties of the viscous fluid in these upper pitchers arguably explains the species richness of their flying prey. The pitchers of N. rafflesiana are therefore more than simple pitfall traps and the digestive fluid plays an important yet unsuspected role in the ecological success of the species.

Daily age and food habits of Lateolabrax latus larvae and juveniles occurring in the innermost shallow waters of Uwajima Bay, Japan

Daily age and food habits of Lateolabrax latus larvae and juveniles were investigated at two different habitats in Uwajima Bay, western Shikoku, Japan. In the shallow zone at Miura, which contained eelgrass beds, larvae occurred from January and were collected abundantly in March. The size, age, and hatch-date distributions suggested that late-hatched specimens stay longer than earlyhatched specimens at this station. On the contrary, in the intertidal flats of the Kunomura River mouth larvae were rarely collected, but juveniles were collected in relative abundance from April. The distributions in the intertidal flats station suggested that specimens had migrated from another location and then resided in the intertidal flats. Spatial and temporal trophic variations increased remarkably with metamorphosis, and thus, the spatial differences in growth rate were considered in relation to the trophic diversity of prey items. Our results suggest that the nursery environment, nursery utilization pattern, and food habits of early life stages of L. latus show remarkable flexibility. From the similarity of these ecological aspects with L. japonicus, which is a closely related species, we suggest the of these ecological aspects with L. japonicus, which is a closely related species, we suggest the important role of the interspecific competition to the realized niche difference between Lateolabrax congeners.

DIETS OF TWO SYNTOPIC POPULATIONS OF FROGS, RANA VAILLANTI AND RANA BROWNORUM, FROM A TROPICAL RAIN FOREST IN SOUTHERN VERACRUZ, MÉXICO

We present data on diet of 2 syntopic populations of frogs, Rana vaillanti and R. brownorum collected near the Los Tuxtlas biological field station, Veracruz, México. Rana vaillanti strictly inhabits ponds, whereas R. brownorum occurs in several microhabitat types. The stomach contents of 26 specimens of R. vaillanti and 22 of R. brownorum were analyzed. Arthropods consumed by R. vaillanti and R. brownorum included 10 and 12 taxa, respectively. The main prey items for R. vaillanti were Diptera (42.3%), decapod crustaceans (16.3%), Mollusca (Stylomatophora, 8.1%), and Orthoptera (8.2%), whereas R. brownorum consumed Orthoptera (22.0%), Coleoptera (20.8%), and Hymenoptera (15.6%). A regression analysis between prey sizes and snout-vent length was significant in R. brownorum, but not in R. vaillanti. Diversity of prey items was higher in R. brownorum than in R. vaillanti.

Variability in foraging behaviour and prey of the Common Fiscal Shrike, Lanius collaris, along an altitudinal gradient in South Africa

Aspects of the foraging behaviour along an altitudinal gradient of four subpopulations (Durban, Merrivale, Estcourt and Harrismith) of colour-banded Common Fiscals (Lanius collaris) were analysed in summer and winter in South Africa. The shrike subpopulations showed significant differences in their attack, capture and success rates. The shrikes obtained more food during winter by increasing their attack and capture rates, and by taking larger prey items. Foraging success also increased from summer to winter in all except the Harrismith subpopulation, and was dependant upon the size of prey attacked. Perching height, attack distance, encounter time and prey length were significantly different between the sites, but only prey length showed a significant seasonal difference. It is expected that the increased attacks and captures during winter were in response to greater food demands. Common Fiscals displayed significant variability in feeding strategies and foraging parameters along the altitudinal gradient. The foraging efficiency of Common Fiscals is similar to other shrikes that hunt in a similar manner. Invertebrate prey was important (>90%) whilst vertebrate prey (frogs, small reptiles, birds and small mammals) was low (<10%). Durban birds took the greatest number of prey items during summer and winter, followed by the Merrivale, Estcourt and Harrismith birds. Subpopulations also displayed significant differences in the amount and size of prey items cached, but the number and length of cached items were independent of season. The wide variety of prey items consumed showed that Common Fiscals are highly opportunistic. This opportunism and their sit-and-wait predator method are important. Even if shrikes seek to maximise encounters with larger (higher energy) items, the low capture rates and short duration of foraging attempts when taking smaller items indicate that small items can be taken with little opportunity cost while waiting for better items to appear.

Variation in the diet of the red cod with size and season around the Falkland Islands (south-west Atlantic)

Ontogenetic and seasonal variations in the diet were studied for a benthopelagic fish, the red cod Salilota australis (Pisces: Moridae) from the Falkland Islands shelf. The study revealed that small fish (&lt;39 cm total length, TL) fed mainly on benthic gammarid amphipods, with squid Loligo gahi, Illex argentinus and the fish Patagonotothen spp. being of secondary importance. In medium sized fish (40–60 cm TL) the importance of fish in their diet increased, but benthic gammarid amphipods remained important, although their role decreased in the percentage by weight. Large fish (&gt;61 cm TL) fed mainly upon Patagonotothen spp. which consisted of 90% by weight. Seasonal variations were analysed only for medium-sized fish. In February–June, S. australis fed mainly on benthic amphipods and Patagonotothen spp. In July–October, the squid Loligo gahi became the most common prey. In November–January benthic crustaceans reappeared in the diet, and Patagonotothen spp. became the most important prey item followed by benthic gammarid amphipods and the isopod Seriolis sp. The niche breadth was found to be similar in the different size groups (2·03–2·66), indicating that the fish fed on one to two abundant prey items in each group. The niche breadth of medium-sized fish varied seasonally reflecting the diversity of prey items utilized throughout the year.

A New Species of Eimeria (Apicomplexa: Eimeriidae) from the Green Water Snake, Nerodia cyclopion (Reptilia: Serpentes), in Arkansas, U.S.A.

Eimeria cyclopion n. sp. is described from the intestinal contents and feces of 10/15 (67%) green water snakes, Nerodia cyclopion cyclopion, in northeastern Arkansas. Oocysts of the new species are ellipsoidal, 18.7 x 13.1 (14-22 x 12-15) Am, with a smooth, thin, single-layered wall; shape index 1.4 (1.1-1.6). A polar granule and oocyst residuum are present, but a micropyle is absent. Sporocysts are elongate, 13.9 x 4.5 (12-15 x 4-5) Am, each with two filaments that appear to arise from a thin membrane covering the sporocyst; shape index 3.1 (2.8-3.6). A Stieda body and sporocyst residuum are present, but a substieda body is absent. The sporozoites are elongate, 10.6 x 2.9 (10-12 x 2.6-3.2) ,um in situ, each containing spherical anterior and ellipsoidal posterior refractile bodies. A nucleus is located between the refractile bodies. The new form also was found in three sympatric congeners from the study site. In addition, two previously described eimerians were harbored by these hosts. The green water snake, Nerodia cyclopion (Dumeril, Bibron & Dumeril) is a large, heavy-bodied aquatic colubrid that ranges from coastal South Carolina through Florida, west to Louisiana and southeastern Texas, and north through eastern Arkansas to extreme southern Illinois (Behler & King, 1979). The species prefers aqueous areas with sluggish flow and dense aquatic vegetation, including cypress swamps, oxbow lakes, rice fields, river sloughs and bayous, and occasionally estuaries. A variety of prey items are included in the diet of N. cyclopion, although minnows and other small fishes apparently are the most important component (Kofron, 1978). There is a plethora of information available on helminths of N. cyclopion (see Ash & Beaver, 1963; Brooks, 1978, 1979; Little, 1966; Sprent, 1979). However, nothing is known about its coccidian parasites. Recently, we had an opportunity to examine specimens of N. c. cyclopion and other sympatric water snakes from northeastern Arkansas for coccidia. During that period, we found a previously undescribed species of Eimeria and other eimerians in these hosts. A description of the new species is provided 1 We thank B. Beville, B. P. Butterfield, and W. E. Meshaka for assistance in collecting snakes, two anonymous reviewers for critically reviewing the manuscript, and the Arkansas State Game and Fish Commission for Scientific Collecting Permit No. 775. Publication costs, in part, are being met by a grant from the Spencer-Tolles Fund of the American Microscopical Society. 2 Division of Biology, Ackert Hall, Kansas State University, Manhattan, Kansas 66506, U.S.A. 3 Department of Biological Sciences, Arkansas State University, State University, Arkansas 72467, U.S.A. TRANS. AM. MICROSC. SOC., 109(1): 69-73. 1990. ? Copyright, 1990, by the American Microscopical Society, Inc. This content downloaded from 157.55.39.106 on Mon, 10 Jul 2017 17:40:25 UTC All use subject to http://about.jstor.org/terms TRANS. AM. MICROSC. SOC.

Diet, food resource partitioning and feeding periodicity of two riffle-dwelling fish species in a New Zealand river

The diets and feeding periodicities of two small, riffle-dwelling fish, the torrentfish, Cheimarrichthys fosteri, and the bluegilled bully, Gobiomorphus hubbsi, were investigated in an unstable, braided New Zealand river from May 1985 to April 1986. Aquatic insect larvae dominated diets of all fish and dietary overlap between species was high in 10 of 12 months. Nevertheless, the relative importance of prey items, as assessed by the index of relative importance (IRI), differed between species. Gobiomorphus hubbsi fed almost exclusively on larval Deleatidium (Ephemeroptera), whereas C. fosteri consumed a greater variety of prey items, with Deleatidium and trichopteran, elmid and chironomid larvae numerically dominant. A dietary switch from Deleatidium to chironomid larvae occurred in both species during December 1985, when total and relative abundances of mayfly and other benthic macroinvertebrate larvae were severely reduced by two consecutive floods. A diel sampling programme indicated that the feeding periodicity of the two species differed: C. fosteri was a nocturnal feeder, whereas G. hubbsi exhibited a strong crepuscular peak in feeding activity. Overall, the two fish partition their food resource weakly by consuming prey items in different proportions and sizes and more strongly by utilizing the food resource at different times.

Emersion behaviour and foraging ecology of the common Chilean clingfishSicyases sanguineus(Pisces: Gobiesocidae)

The present study is the first to correlate information on emersion behaviour and foraging ecology of Sicyases sanguineus, a common clingfish of the Chilean coast. Individuals smaller than 15 cm in total length were frequently found at the highest points in the inter-tidal zone and consumed inter-tidal animals and seaweeds. Fish larger than 23 cm were infrequently observed emersed in the lower inter-tidal zone, but were collected sub-tidally by divers. These large clingfish ate mainly benthic animals occurring in the low inter-tidal and sub-tidal zones. Size-dependent factors, dessication and wave impact restrict the area of action of S. sanguineus to certain areas of the rocky inter-tidal and shallow sub-tidal zone. However, the fish can be locally very abundant, consuming a great diversity of prey items including both direct primary space users and mobile animals able to affect community structure through grazing. We argue, therefore, that S. sanguineus may be important in structuring communities in som...