Feeding Biology Research Articles

Diel feeding patterns and daily ration estimates of three subantarctic euphausiids in the vicinity of the Prince Edward Islands (Southern Ocean)

The feeding biology of three euphausiid species, Euphausia vallentini (adults and juveniles), Euphausia longirostris, and Nematoscelis megalops, was investigated in the vicinity of the Prince Edward Archipelago during austral autumn (April/May) of 1998 and 1999, using the gut fluorescence and gut fullness techniques, to assess diel feeding patterns and estimate daily rations. The results showed clear diel feeding patterns for both E. vallentini adults and juveniles. High feeding activity occurred during dark hours in E. longirostris, while N. megalops did not show distinct diel feeding pattern. E. longirostris had the highest gut pigment levels, averaging 15.2 and 57.1 ng pigm ind−1 in 1998 and 1999, respectively. A similar pattern was observed for E. vallentini: 3.2 versus 6.5 ng pigm ind−1 in juveniles and 4.4 versus 21.9 ng pigm ind−1 in adults. Low average gut pigment levels were found for N. megalops during both years (range 2.0–4.5 ng pigm ind−1). Gut evacuation rates varied between 0.45 and 0.99 h−1 for E. vallentini adults, 0.47 and 1.36 h−1 for E. vallentini juveniles, 0.41 and 1.08 h−1 for N. megalops. A single measurement of 0.94 h−1 was made for E. longirostris. Ingestion rates for E. vallentini ranged from 0.24 to 1.82 μg pigm ind−1 d−1 for adults and from 0.98 to 1.92 μg pigm ind−1 d−1 for juveniles. The highest individual ingestion rates were found for E. longirostris (between 1.24 and 3.65 μg pigm ind−1 d−1), and the lowest for N. megalops (0.23 μg pigm ind−1 d−1). These ingestion rates were combined with data from the gut fullness technique to estimate the contribution of herbivory to the total daily carbon uptake.

Food and Feeding Biology of the Black Skimmer in Argentina: Evidence Supporting Offshore Feeding in Nonbreeding Areas

-We investigated the diet of the Black Skimmer (Rynchops niger) in three consecutive years (autumn 1998, autumn 1999 and summer 2000) by analyzing 642 pellets collected at Punta Rasa, Samborombon Bay, Buenos Aires, Argentina. Fish was the main prey in the diet (occurrence = 100%), while insects were present in only 2.7% of samples. Among the 14 fish species identified, Argentine Anchovies (Engraulis anchoita) (occurrence = 38.7%, N = 31.5%), Silversides (Odontesthes spp.) (occurrence = 38.3%, N = 26.2%) and White Croakers (Micropogoniasfurnieri) (occurrence = 11.6%, N = 20.5%) were the most important prey. Fish prey averaged 77 mm in length (?34 mm, range 15-169 mm, N = 123), and had an average mass of 6.9 g (?7.3 g, range 0.1-31.6 g, N = 123). Marked differences were observed in the frequency of occurrence and numeric importance of the fish prey species found in the three sampling seasons; while typical marine fishes, such as the Argentine Anchovy, constituted the bulk of the diet during 1998, estuarine juvenile fish prevailed in 1999 and 2000. The comparison of size and mass of prey between seasons also revealed large differences. Fishes caught in 1998 were significantly larger and heavier than those caught in other seasons. The diet of skimmers overlapped with that of South American Terns (Sterna hirundinacea), Royal Terns (S. maximus) and Sandwich Terns (S. sandvicensis) in the area during 1998, when prey was mostly marine fish. Received 17 April 2001, accepted 25June 2001.

Feeding: form, function, and evolution in tetrapod vertebrates

As the first four-legged vertebrates, called tetrapods, crept up along the shores of ancient primordial seas, feeding was among the most paramount of their concerns. Looking back into the mists of evolutionary time, fish-like ancestors can be seen transformed by natural selection and other evolutionary pressures into animals with feeding habitats as varied as an anteater and a whale. From frog to pheasant and salamander to snake, every lineage of tetrapods has evolved unique feeding anatomy and behavior. Similarities in widely divergent tetrapods vividly illustrate their shared common ancestry. At the same time, numerous differences between and among tetrapods document the power and majesty that comprises organismal evolutionary history. Feeding is a detailed survey of the varied ways that land vertebrates acquire food. The functional anatomy and the control of complex and dynamic structural components are recurrent themes of this volume. Luminaries in the discipline of feeding biology have joined forces to create a book certain to stimulate future studies of animal anatomy and behavior.

Spatial aspects of the reproductive and feeding biology of the striped robber, Brycinus lateralis (Pisces: Characidae), in the Okavango Delta, Botswana

The Okavango Delta is a vast inland wetland system situated in northern Botswana. High rainfall is received in early summer in the southern Angolan highlands and throughout the Delta with the flood waters reaching the upper riverine floodplain between March and May where it percolates through to the lower drainage rivers between July and September. Aspects of the reproductive and feeding biology of two allopatric populations of the striped robber, Brycinus lateralis, a small characin species inhabiting the northern riverine floodplain and southern drainage rivers, were investigated. Both populations were similar in the biological aspects studied, with the flood cycle having little influence on the timing of reproduction, sexual maturity and dietary composition. Female fish from both populations matured sexually at 57 mm SL, breeding over a protracted period during the warm, summer months. In both populations, the sex ratio was female-dominated at 4.8:1 (riverine floodplain) and 2.2:1 (drainage rivers). The striped robber is an opportunistic micro-carnivore with immature fish feeding predominantly on Daphnia spp. and adults being largely insectivorous.

Food and Feeding Biology of the Common Tern during the Nonbreeding Season in Samborombon Bay, Buenos Aires, Argentina

-Common Terns (Sterna hirundo), which breed in North America and migrate into the southern hemisphere in winter, show a wide nonbreeding distribution that includes the Atlantic coasts of Argentina and Brazil. At Punta Rasa (Samborombon Bay, Argentina), there were about 30,000 Common Terns. Their diet in winter was assessed by the analysis of regurgitated pellets collected at Punta Rasa. Adult Coleoptera, Odonata, Orthoptera and Hemiptera were the main insects found in the diet. A total of 14 species of fishes were identified. Argentine Anchovy (Engraulis anchoita) and Anchovy (Anchoa marinii) (Family Engraulidae), represented 79% by number and the 78% of the consumed biomass of fish prey. The average length of fish prey was 90.0 ? 17.6 mm. Half the prey lived in seawater, while the other half was taken in estuarine or seawater. There was no evidence of fish prey taken by terns foraging in freshwater habitats. Total consumption of food was estimated as 106 tons of fish (most of themjuvenile) during a five month period at Punta Rasa. Received 6 August 2000, accepted 9 December 2000.

Advances in the Study of Feeding Behaviors, Mechanisms, and Mechanics of Sharks

Sharks as a group have a long history as highly successful predatory fishes. Although, the number of recent studies on their diet, feeding behavior, feeding mechanism, and mechanics have increased, many areas still require additional investigation. Dietary studies of sharks are generally more abundant than those on feeding activity patterns, and most of the studies are confined to relatively few species, many being carcharhiniform sharks. These studies reveal that sharks are generally asynchronous opportunistic feeders on the most abundant prey item, which are primarily other fishes. Studies of natural feeding behavior are few and many observations of feeding behavior are based on anecdotal reports. To capture their prey sharks either ram, suction, bite, filter, or use a combination of these behaviors. Foraging may be solitary or aggregate, and while cooperative foraging has been hypothesized it has not been conclusively demonstrated. Studies on the anatomy of the feeding mechanism are abundant and thorough, and far exceed the number of functional studies. Many of these studies have investigated the functional role of morphological features such as the protrusible upper jaw, but only recently have we begun to interpret the mechanics of the feeding apparatus and how it affects feeding behavior. Teeth are represented in the fossil record and are readily available in extant sharks. Therefore much is known about their morphology but again functional studies are primarily theoretical and await experimental analysis. Recent mechanistic approaches to the study of prey capture have revealed that kinematic and motor patterns are conserved in many species and that the ability to modulate feeding behavior varies greatly among taxa. In addition, the relationship of jaw suspension to feeding behavior is not as clear as was once believed, and contrary to previous interpretations upper jaw protrusibility appears to be related to the morphology of the upper jaw-chondrocranial articulation rather than the type of jaw suspension. Finally, we propose a set of specific hypotheses including: (1) The functional specialization for suction feeding hypothesis that morphological and functional specialization for suction feeding has repeatedly arisen in numerous elasmobranch lineages, (2) The aquatic suction feeding functional convergence hypothesis that similar hydrodynamic constraints in bony fishes and sharks result in convergent morphological and functional specializations for suction feeding in both groups, (3) The feeding modulation hypothesis that suction capture events in sharks are more stereotyped and therefore less modulated compared to ram and bite capture events, and (4) The independence of jaw suspension and feeding behavior hypothesis whereby the traditional categorization of jaw suspension types in sharks is not a good predictor of jaw mobility and prey capture behavior. Together with a set of questions these hypotheses help to guide future research on the feeding biology of sharks.

Reproduction and food habits of the lined seahorse, Hippocampus erectus (Teleostei: Syngnathidae) of Chesapeake Bay, Virginia.

The reproductive and feeding biology of the lined seahorse, Hippocampus erectus, was studied in Chesapeake Bay. Seahorses are monogamous, and males incubate the eggs received from females in a closed brood pouch (= marsupium). Females do not play any parental care after mating. Total sex ratio and the operational sex ratio was strongly skewed toward females. Males and females had similar number of eggs/embryos and hydrated oocytes, respectively. The number of eggs/embryos found in the male brood pouch varied from 97 to 1,552 (fish from 80 to 126 mm TL), whereas the number of hydrated oocytes in female varied from 90 to 1,313 (fish from 60 to 123 mm TL). Both, the number of eggs/embryos and hydrated oocytes were better linearly correlated to total weight than to total length. The small snout and mouth size limits the feeding of the lined seahorse to small prey size. Amphypods were the predominant food items found in the guts, especially Ampithoe longimana, Gammarus mucronatus, and Caprella penantis. The lined seahorse is not abundant in Chesapeake Bay, but keeps a breeding population which is probably brought inside the bay by currents on drifting vegetation. Chances to find a partner may be difficult because of its low abundance, due to turbid waters, and its sedentary behavior.

Species-specific impacts of grazing amphipods in an eelgrass-bed community

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 223:201-211 (2001) - doi:10.3354/meps223201 Species-specific impacts of grazing amphipods in an eelgrass-bed community J. Emmett Duffy*, Annie M. Harvilicz School of Marine Science and Virginia Institute of Marine Science, The College of William and Mary, Gloucester Point, Virginia 23062-1346, USA *E-mail: jeduffy@vims.edu ABSTRACT: Small, grazing invertebrates often benefit seagrasses by cropping their epiphytic algal competitors. Yet predictive relations between grazer abundance and seagrass performance are elusive, in significant part because of poorly understood diversity in mesograzer feeding biology. We conducted experiments in eelgrass Zostera marina microcosms to explore how differences in feeding between 2 common grazing amphipod taxa affected accumulation and species composition of epiphytes on eelgrass, as well as amphipod population growth, competition and production, over a 4-week period in summer. Gammarus mucronatus and ampithoids (a mixture of Cymadusa compta and Ampithoe longimana) were stocked, singly and in combination, along with a grazer-free control treatment. Amphipod population growth rates indicated that the 2 taxa competed for a common limiting resource, presumably periphyton, which was essentially eliminated in all grazer treatments. Final abundances of both amphipod taxa were 53 to 68% lower in treatments where the other grazer was present than in single-species grazer treatments. A common carrying capacity was also indicated by the nearly identical final biomass of amphipods across treatments, despite 2-fold variation in initial amphipod densities. These results support the hypothesis that the 2 amphipod taxa are roughly equivalent in terms of resource requirements and production rates. Despite this equivalence, subtle differences in diet breadth between amphipod taxa translated into substantial differences in biomass and composition of the fouling assemblage among treatments. Whereas grazer-free eelgrass became heavily fouled with periphyton and tunicates, eelgrass exposed to G. mucronatus alone was overgrown by the red alga Polysiphonia harveyi, which reached a biomass equal to the total fouling mass of grazer-free controls. P. harveyi was nearly absent from all other treatments. In contrast, eelgrass with ampithoids was virtually devoid of all fouling material. Thus, similar mesograzer species can have markedly different impacts on fouling assemblages, and these occur despite strong similarity in grazer energetics and primary food sources. Our results may help to reconcile evidence of diet overlap and diffuse competition among mesograzer species with the different feeding preferences and community impacts shown for several mesograzers in experimental studies. KEY WORDS: Amphipods · Ampithoe longimana · Community structure · Competition · Cymadusa compta · Gammarus mucronatus · Grazing · Mesograzers · Resource limitation · Zostera marina Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 223. Online publication date: November 28, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.

Polydora and Related Genera Associated with Hermit Crabs from the Indo-West Pacific (Polychaeta: Spionidae), with Descriptions of Two New Species and a Second Polydorid Egg Predator of Hermit Crabs

Polydora and Related Genera Associated with Hermit Crabs from the Indo-West Pacific (Polychaeta: Spionidae), with Descriptions of Two New Species and a Second Polydorid Egg Predator of Hermit Crabs1 Jason D. Williams Abstract Polydora and related genera associated with hermit crabs from shallow subtidal coral reef areas of the Indo-West Pacific are described. Over 2000 hermit crabs were collected from localities in the Philippines and Indonesia between July 1997 and April 1999. In total, 10 species of polychaetes among five genera (Boccardia, Carazziella, Dipolydora, Polydora, and Tripolydora) were identified and described. Adult morphology of these species was investigated with light microscopy and scanning electron microscopy. The study includes the description of two new Polydora species, including the second known polydorid egg predator of hermit crabs. Six of the species burrow into calcareous substrata, living in burrows within live or dead gastropod shells or coralline algae attached to shells. Two species were found in mud tubes within crevices of gastropod shells inhabited by hermit crabs. The zoogeography and biodiversity of polydorids from the West Pacific are discussed. The diversity of polydorids from the Philippines is comparable with that of other central Pacific and Indo-West Pacific islands, but it is lower than that in areas of the North and Southwest Pacific; lower diversity probably reflects disparity in sampling efforts between these regions. A key to the Philippine polydorids is provided. Polychaetes are common associates of hermit crabs, either living on, within, or burrowing into occupied gastropod shells (e.g., Jensen and Bender 1973, Stachowitsch 1980, Hoberg et al. 1982, Karlson and Shenk 1983, Walker 1995). In particular, Polydora and related genera (termed polydorids, nine genera of the family Spionidae that contain a modified fifth segment) are known to burrow into calcareous substrata including gastropod shells occupied by hermit crabs (Blake and Evans 1973, Read 1975, Radashevsky 1993, Blake 1996, Martin and Britayev 1998, Williams 2000). The burrowing behavior of these species has been investigated in substantial detail because of their effects on commercially important mollusk species (see Radashevsky and Williams 1998). Polydorids have been considered to be facultative or obligate commensals of hermit crabs, but recent research indicates that the worms can have negative effects on their hosts (Buckley and Ebersole 1994, Williams 2000). The purpose of this investigation was to examine the systematics and ecology of polydorids associated with hermit crabs from coral reef areas of the Indo-West Pacific. The Spionidae is one of the most conspicuous polychaete families of Indo-West Pacific islands, in many areas second only to the family Syllidae in number of recorded genera (Knox 1957, Bailey-Brock 1995, Paxton and Chou 2000). Polydorids are common inhabitants of coral reef areas, and some species are bioeroders found to burrow in live and dead corals and mollusk shells (Hartman 1954, Bailey-Brock 1995). In spite of the amount of work completed in the North and [End Page 429] Southwest Pacific (see Blake and Kudenov 1978, Radashevsky 1993, Sato-Okoshi 1999, Radashevsky and Hsieh 2000a,b), polydorids from central Indo-West Pacific areas such as the Philippines remain largely unknown. Before this investigation only two polydorid species had been identified from the Philippines, although a number of faunistic surveys of the polychaetes from the Philippines and surrounding areas have been completed (Pillai 1965, Williams 2000). Part of the success of polydorids is due to the possession of long prehensile palps allowing the worms to suspension and deposit feed or a combination of both (Williams and McDermott 1997). Other taxonomically important features of these worms include major spines of the fifth segment, branchial distribution, neuropodial hooded hook morphology, and pygidium morphology. This paper represents part of a series of studies on the systematics, ecology, and feeding biology of polydorids associated with hermit crabs from the Indo-West Pacific. The first paper provided the description of Polydora robi, an obligate commensal of hermit crabs from the Philippines and Indonesia (Williams 2000). Polydora robi was documented to ingest the embryos of host hermit crabs, and the reproduction and larval development of the species have been investigated (Williams 2001). The study reported here provides records of 10 species of polydorids from the Philippines and Indonesia, nine of...

Feeding biology of a guild of benthivorous fishes in a sandy shore on south-eastern Brazilian coast.

The feeding biology of eight species of benthivorous fishes was studied in a sandy shore at Anchieta Island, south-eastern Brazilian coast. The fishes fed mainly on Amphipoda and Mysidacea crustaceans. The diet of the most abundant species, the drum Umbrina coroides, was analyzed in three standard length classes (20-55, 56-90 and 91-135 mm). This sciaenid showed an ontogenetic diet shift from Mysidacea to Amphipoda. The feeding behaviour of the sciaenid U. coroides and the gerreid Eucinostomus gula was recorded while snorkeling. During their foraging both species uncovered small organisms buried in the sand. Notwithstanding general similarities in diet, U. coroides and E. gula presented differences in feeding behaviour and morphology. Two carangid species of the genus Trachinotus differed in diet composition and consumed a larger array of food items than the remaining fish species. Differences in diet and feeding activity between the remaining benthivorous species were noted. These differences possibly reduce overlap in resource use and favour the coexistence of guilds of benthivorous fishes on sandy shores.

Mouthpart evolution in adults of the basal, «symphytan», hymenopteran lineages

We review feeding biology and mouthpart structure generally among adults of the basal hymenopteran, or «symphytan», lineages (sawflies, woodwasps, horntails and their relatives). These insects feed on a wide range of materials: floral and extrafloral nectar, pollen, plant (floral and leaf) tissues, plant (angiosperm) sap, the juice of ripe fruit, the spermatial fluid of rust fungi, sternorrhynchan bug honeydew, and insect tissues. Adults show feeding-related mouthpart specialization either for consuming pollen (the Xyelidae only) or for consuming «concealed» floral nectar (several families). Seven functional types of elongated proboscis or «concealed-nectar extraction apparatus (CNEA)» have previously been recognized among Hymenoptera. We identify an additional type, which appears to be unique among Hymenoptera and has probably evolved directly from unspecialized mouthparts (labiomaxillary complex). In total, three types of CNEA are known to occur in «Symphyta». Type 1 occurs in Pamphiliidae, Megalodontesidae, Argidae, Pergidae, Tenthredinidae, Cimbicidae and Cephidae. Type 5 occurs in Pergidae (in two unidentified species of Euryinae). Type 8 occurs in Tenthredinidae (in the genusNipponorhynchus Takeuchi). CNEA of some type or other has arisen at least twice within the family Tenthredinidae and at least twice within the pergid subfamily Euryinae. Evolutionary parallelism in CNEA structure has occurred between the basal, «symphytan», hymenopteran lineages and the Apocrita, a phenomenon hitherto not mentioned in the literature. Within the «Symphyta», possession of Type 1 CNEA appears to be a ground plan feature of each of the following taxa: the pergid genus Eurys Newman, the megalodontesid genus Megalodontes Latreille (the only extant representative of the Megalodontesidae) and the tenthredinid genus Cuneala Zirngiebl, while possession of Type 8 appears to be a ground plan feature of the tenthredinid genus Nipponorhynchus Takeuchi. However, in general among «Symphyta», possession of CNEA is characteristic of only small and taxonomically subordinate groups, suggesting that CNEA has evolved independently many times within the basal hymenopteran lineages rather than being inherited from a common ancestor early in the evolutionary history of the Hymenoptera. In other words, ecological expediency rather than phylogenetic history mainly accounts for its distribution pattern within the basal lineages. The results of a morphological survey of «Symphyta» indicate that the habit of exploiting «concealed» nectar, by means of CNEA, is fairly widespread (CNEA is present in at least half of the extant families), contradicting the view held in the literature on flower visiting that it is altogether absent. We discuss our findings in relation to the occurrence and evolution of «suctorial» mouthparts in other Hymenoptera and in non-hymenopteran insects: Mecopterida, Coleoptera and Hemiptera.

Mouthpart evolution in adults of the basal, ‘symphytan’, hymenopteran lineages

We review feeding biology and mouthpart structure generally among adults of the basal hymenopteran, or «symphytan», lineages (sawflies, woodwasps, horntails and their relatives). These insects feed on a wide range of materials: floral and extrafloral nectar, pollen, plant (floral and leaf) tissues, plant (angiosperm) sap, the juice of ripe fruit, the spermatial fluid of rust fungi, sternorrhynchan bug honeydew, and insect tissues. Adults show feeding-related mouthpart specialization either for consuming pollen (the Xyelidae only) or for consuming «concealed» floral nectar (several families). Seven functional types of elongated proboscis or «concealed-nectar extraction apparatus (CNEA)» have previously been recognized among Hymenoptera. We identify an additional type, which appears to be unique among Hymenoptera and has probably evolved directly from unspecialized mouthparts (labiomaxillary complex). In total, three types of CNEA are known to occur in «Symphyta». Type 1 occurs in Pamphiliidae, Megalodontesidae, Argidae, Pergidae, Tenthredinidae, Cimbicidae and Cephidae. Type 5 occurs in Pergidae (in two unidentified species of Euryinae). Type 8 occurs in Tenthredinidae (in the genusNipponorhynchus Takeuchi). CNEA of some type or other has arisen at least twice within the family Tenthredinidae and at least twice within the pergid subfamily Euryinae. Evolutionary parallelism in CNEA structure has occurred between the basal, «symphytan», hymenopteran lineages and the Apocrita, a phenomenon hitherto not mentioned in the literature. Within the «Symphyta», possession of Type 1 CNEA appears to be a ground plan feature of each of the following taxa: the pergid genus Eurys Newman, the megalodontesid genus Megalodontes Latreille (the only extant representative of the Megalodontesidae) and the tenthredinid genus Cuneala Zirngiebl, while possession of Type 8 appears to be a ground plan feature of the tenthredinid genus Nipponorhynchus Takeuchi. However, in general among «Symphyta», possession of CNEA is characteristic of only small and taxonomically subordinate groups, suggesting that CNEA has evolved independently many times within the basal hymenopteran lineages rather than being inherited from a common ancestor early in the evolutionary history of the Hymenoptera. In other words, ecological expediency rather than phylogenetic history mainly accounts for its distribution pattern within the basal lineages. The results of a morphological survey of «Symphyta» indicate that the habit of exploiting «concealed» nectar, by means of CNEA, is fairly widespread (CNEA is present in at least half of the extant families), contradicting the view held in the literature on flower visiting that it is altogether absent. We discuss our findings in relation to the occurrence and evolution of «suctorial» mouthparts in other Hymenoptera and in non-hymenopteran insects: Mecopterida, Coleoptera and Hemiptera.

Digestive function in Australian magpie geese (Anseranas semipalmata)

The Australian magpie goose (Anseranas semipalmata) is not really a ‘goose’ but an aberrant species representing the monotypic family Anseranatidae. It is herbivorous but its ability to utilise dietary fibre is uncertain. We examined digestive processes in tame birds fed natural forages in metabolism cages and in wild birds. An examination of the gross anatomy of the gut showed features similar to those in waterfowl of the family Anatidae, the true ducks and geese. In a total-collection feeding trial geese were fed either unhusked rice grain or fresh aquatic grass. The aquatic grass was high in fibre (neutral detergent fibre (NDF) was 74% of dry matter) and magpie geese could not maintain energy or nitrogen balance on this feed. The maintenance energy requirement of the caged magpie geese, as estimated on the rice diet, was 573 kJ kg–1 day–1, which was similar to that found for other species of geese. The maintenance nitrogen requirement was 0.44 g N kg–1 day–1 or 0.52 g N kg–0.75 day–1, which also was similar to the average value for birds. Fibre digestion on both diets was small, 19% and 27% of NDF for rice and grass respectively. Rates of passage of fibrous digesta through the gut of magpie geese varied with diet. The mean retention time for fibre was longer when feeding on the aquatic grass than on unhusked grain, 7.7 3.0 h v. 3.7 0.6 h Data from wild magpie geese clarified the process of digestion. The patterns of pH and short-chain fatty acids along the gut pointed to acid and enzymic digestion occurring in most of the tract, down to the ileocaecal junction. Fermentation appeared restricted to the caeca, rectum and cloaca, though, of note, the caeca contained little fibre, 5% NDF. Higher levels of fibre digestion were indicated in wild geese but fibre still was not a major contributor to the energy intake of these birds. The digestive capabilities of the magpie geese were considered in relation to their impact on the feeding and reproductive biology of these ‘geese’ in monsoonal, northern Australia

Feeding habits of Pterodoras granulosus (Valenciennes) (Pisces, Doradidae) in the lower Plata Basin

Feeding habits of Pterodoras granulosus (Valenciennes) (Pisces, Doradidae) in the lower Plata Basin. The feeding biology of Pterodoras granulosus (armored catfish) was studied in an extensive area comprising two environments of different characteristics, a typical lotic system, the Lower Paraná River, and an environment transitional towards an estuarian system on the right margin of the Río de la Plata. The relative importance of the different feeding items observed in the stomach content of Pterodoras granulosus represented the relative abundance of them in the environment. Therefore, P. granulosus appeared as a benthic, strongly euriphagic and hardly selective organism consuming vegetation and molluscs, whith little selectivity, its diet being dominated by vegetation in the Lower Paraná River and molluscs on the right margin of the Rio de la Plata. The mussel Limnoperna fortunei showed a high percentage of occurrence in all sampling sites. The eventual importance of the feeding habits of P. granulosus on the population density of C. limnoperna is discussed.

SNAIL SPEARS AND SCIMITARS: A CHARACTER ANALYSIS OF CONUS RADULAR TEETH

Knowledge of the attributes of the venom-injecting radular teeth of Conus can enhance understanding of the functional biology of feeding and the systematics of this large and taxonomically difficult genus of gastropods. We define and provide a scheme for coding the states of Conus radular tooth characters, in order to facilitate their use in taxonomic and phylogenetic studies. To exemplify these characters, we describe and illustrate teeth of putatively primitive species and of species representing generalized, vermivorous, molluscivorous and piscivorous feeding groups within the genus. We define and address the intraspecific and interspecific variation of ten presence-absence characters and 15 continuous characters, of which at least five and ten, respectively, are present in most species. Some continuous characters are bimodally distributed among the species sampled. If this distribution still obtains when additional species are examined, these characters could also be coded unambiguously as having two states. We also review the several previously proposed classification schemes of Conus radular teeth and of species according to tooth characters. As Troschel suggested in 1866, a tooth length:width ratio greater than or less than 20 separates the genus into two distinct species groups, now known to comprise the molluscivorous and piscivorous species in the former, and vermivorous and generalized species in the latter. Important subsidiary characters are the number of barbs, presence/absence of blade, cusp, and spur, length of serrations, relative width of base, and tooth length:shell length ratio.

Feeding biology of a predatory and a facultatively predatory nematode ( Enoploides longispiculosus and Adoncholaimus fuscus )

This paper reports on the feeding biology of a predatory and of a facultatively predatory nematode, Enoploides longispiculosus and Adoncholaimus fuscus, respectively. Both species represent genera which are common and abundant in the littoral of the North Sea and in adjacent estuaries. Observations on the foraging behaviour of both species are given, and for the former species, a range of prey from its natural habitat is identified. Respiration was determined using a polarographic oxygen electrode technique and compared to consumption determined as predation rates on the monhysterid nematode Diplolaimelloides meyli. The daily C-loss due to respiration accounted for 15% of the measured C-consumption in E. longispiculosus and for 111% in A. fuscus, proving the observed feeding rates in the latter species to have been inadequate for the maintenance of its aerobic metabolism. Daily respiration rates at an average environmental temperature were 219 ng C ind−1 d−1 for adults of A. fuscus and 21.9 ng C ind−1 d−1 for adults of E. longispiculosus. Using radiotracer techniques, no uptake of bacterial cells or of organic matter in the dissolved phase was demonstrated for E. longispiculosus. In A. fuscus, however, a significant drinking of label in the dissolved or volatile fraction occurred; bacterial cells were taken up at a level insignificant to the nematode's daily C-ration. It is concluded that E. longispiculosus has a fairly strict predatory feeding strategy, while A. fuscus gains a majority of C from additional foraging strategies, among which the uptake of dissolved material and scavenging on macrofauna carcasses (as reported in the literature) may be of particular importance.

Aspects of the Feeding and Reproductive Biology of the Lake Tanganyikan Cichlid, Lamprologus ornatipinnis (Pisces, Cichlidae)

This project investigated the reproductive and feeding biology of Lamprologus ornatipinnis. Specimens were collected monthly from North Bay, Mbita Island, Zambia for a year. Dentition was examined under a scanning electron microscope, stomach contents were analysed using the Index of Relative Importance (IRI) and mean Gonado-somatic Indices (GSI) were calculated for each month to reveal spawning peaks. Both males and females possess an outer row of six (premaxilla) and eight (dentary) enlarged canines. The remaining inner rows consist of small, recurved canine-like teeth. The lower pharyngeal bone possesses enlarged centrally placed molars with an increasing number of smaller bevelled teeth laterally. This dentition is very similar to a typical benthic arthropod and mollusc eater. Stomach content analysis revealed that L. ornatipinnis feeds predominantly on Chironomidae, Copepoda and Ostracoda. The importance of these prey items in the diet differed significantly between the months sampled. Percentage volume of Copepoda and Cyclopoida was greater in female stomachs than males and the % number of Chironomidae greater in males than females. Gonadosomatic Index (GSI) values indicated males and females breed throughout the year. Females, however have a significant peak (p<0.05) in breeding activity from July to October that coincides with the increased abundance of plankton at this time.

Feeding habits of John Dory, Zeus faber, off the Portuguese continental coast

The feeding habits of John Dory (Zeus faber) were studied, based on the analysis of stomach contents from fish sampled in five groundfish surveys. These surveys were carried out off the Portuguese coast during different seasons between 1990 and 1992. The main aspects of feeding biology analysed in this paper are: ontogenetic diet changes, temporal variations in food composition and feeding intensity. Multivariate methods were used to investigate ontogenetic diet shifts. Two main length groups were identified: 8.0–24.9 cm fish, feeding mainly on dragonets and silvery pout, and 25.0–55.9 cm fish whose diet was mainly composed of blue whiting and snipefish. A transitional phase (24.0–30.9 cm fish) with a mixed food composition was observed. This ontogenetic diet shift does not seem to correspond to any important change in body morphology but it does coincide with the onset of sexual maturity in the species.John Dory switched from a diet of small prey species with more pronounced benthic behaviour to a diet of larger schooling pelagic species. This suggests parallel evolution to more pelagic foraging behaviour. However, John Dory feeding habits appear to be largely controlled by the availability and accessibility of prey species: (i) the diet of adult John Dory is dominated by very abundant species; (ii) shifts in the main prey items between different times of the year and between different areas seem to be related both with their absolute and relative abundance in the environment and with the overlap between the depth distribution of predator and prey.

Identification of mustelid species: otter (Lutra lutra), American mink (Mustela vison) and polecat (Mustela putorius), by analysis of DNA from faecal samples

AbstractThe abundance of mink, otter, and polecat may be inferred from records of their scats, and the feeding biology of the species is often studied by analysis of skeletal remains and other hard parts in faeces. However, in some situations it is difficult to distinguish between faeces from these three mustelid species. A method is described for assigning faeces to these three mustelid species, based on analysis of DNA extracted from their scats. Mustelid‐specific primers were developed for PCR amplification of a part of the mitochondrial cytochrome b gene, and two restriction enzymes were found to detect species‐specific sequence variation. Analysis of DNA from different faecal samples showed that the results were reproducible and that the approach provided an efficient method of species identification.

The Effect of Patch Size and Persistence of Host Plants on the Development of Acaricide Resistance in the Two-spotted Spider Mite Tetranychus Urticae (Acari: Tetranychidae)

Spatial and temporal characteristics of host plants can influence the population biology of the herbivores feeding on them. In this study, I examined the effect of variation in host plant characteristics on the development of acaricide resistance in the two-spotted spider mite Tetranychus urticae, a widely distributed agricultural pest. This investigation examined the geographic variation in the degree of resistance to two new types of acaricide, pyridaben and fenpyroximate. From mortality tests at field-level concentrations of the acaricides, many populations collected from fruit trees and roses had a high frequency of resistant individuals for acaricides while almost all populations collected from herbaceous crops had low frequencies of resistant individuals. These results, combined with those from a previous allozyme study, indicate that patch size and persistence of host plants regulate the population structure of the mites including gene flow between populations and, by extension, the development of acaricide resistance.