Robert J. Feller

Importance of predation by crustaceans upon bivalve spat in the intertidal zone of the Dutch Wadden Sea as revealed by immunological assays of gut contents

Predation on bivalve spat (Macoma balthica, Cerastoderma edule and Mya arenaria) by crustaceans was studied in an intertidal area in the western Dutch Wadden Sea in 1993. In all species settlement started at the end of April. Peak numbers were reached in the beginning of June of about 4300 ind. m−2 in Macoma, 1300 in Cerastoderma and 500 in Mya. During June and July numbers dropped sharply to low levels at a mean size of 1.0 to 1.5 mm. Instantaneous mortality rates over this period varied from 0.045 d−1 in Macoma to 0.056 d−1 in both Cerastoderma and Mya. Immunoassays of gut contents of brown shrimps Crangon crangon and shore crabs Carcinus maenas positively identified both species as predators on bivalve spat. The high shrimp densities observed (100 ind. m−2) in combination with their simultaneous presence with the post-larval bivalves indicate that juvenile shrimps are likely the most important predator. The estimated predation pressure by crustaceans, and especially the brown shrimp, is sufficient to account for the observed mortality rates among bivalves. Bivalve recruitment, however, did not appear to be regulated by crustacean predation: during the period of predation, bivalve mortality was not density-dependent. Information on bivalve predation in Swedish bays support this view.

Macrophyte detritus in the winter diet of the estuarine mysid,Neomysis americana

Neomysis americana, a common prey item in the diet of estuarine fish, is seasonally abundant in saltmarsh tidal creeks of North Inlet, South Carolina. Visual examination of mysids collected in winter revealed only diatom tests in their guts, with nearly all of the ingesta unidentifiable. Immunological diet analysis provided strong evidence that proteins fromSpartina alterniflora detritus were present in the guts of field-collected mysids. Laboratory determinations of weight-specific ingestion rates for male and female mysids fed particulateS. alterniflora were best described by a curvilinear quadratic function. Ingestion rates ranged from zero to 0.116 mg C ingested per mg C body weight per hr, or greater than 200% of body carbon per day if continuous feeding is assumed. These high ingestion rates may indicate low assimilation efficiency, but ifN. americana’s assimilation efficiency is similar to that of other mysid species, then this mysid may represent an efficient trophic link between saltmarsh macrophyte production and higher trophic levels. The occurrence ofSpartina detritus in the guts of winter mysids suggests that detritivory may be important during periods of scarce food.

Immunological dietary analysis of two penaeid shrimp species from a South Carolina tidal creek

Abstract The natural, visually unrecognizable components of the diets of two species of penaeid shrimp were studied utilizing immunological methods. Seine samples of Penaeus aztecus Ives and P. setiferus (L.) were collected biweekly from May to November, 1983 in a tidal creek of North Inlet, South Carolina. Three size classes were established to examine possible ontogenetic shifts in diet as the shrimp grew. Immunoassays for P. aztecus indicated both macrofaunal and meiofaunal taxa present in all three size classes, with no single dominant prey. P. setiferus proventricular contents, however, revealed consistent presence of three prey items ( Palaemonetes pugio (Holthuis), Uca pugnax (Smith), and Sesarma reticulatum (Say), as well as gammarid amphipods, polychaetes, periwinkles, and foraminiferans.

Deep-sea food web analysis using cross-reacting antisera

The high incidence of unrecognizable prey in the stomachs of deep-sea predators prompted the application of serological methods for identification of trophic connections. Antisera to whole-organism extracts of estuarine taxa cross-reacted with antigenic protein extracts of mid-water and deep-sea taxa along phylogenetically correct lines, indicating their potential as tools for gut contents immunoassay. Stomach, intestine, and rectum contents of grenadiers (Coryphaenoides armatus) trapped at 2500 m in the North Atlantic were analyzed visually and with 32 antisera representing taxa from 10 common deep-sea phyla. While visual analysis only revealed the presence of fluids, parasites, crustacean exoskeletons, and gastropod opercula, the immunoassay indicated the presence of antigenic proteins from holothurian, anemone, gastropod, decapod, and foraminiferan prey in the same samples. This qualitative serological identification of prey at non-specific taxonomic levels provides evidence that benthic predation may be important within deep-sea communities. The immunoassay technique, although not a panacea for elucidating food web dynamics in remote environments, may be useful when other methods fail to identify trophic pathways.

Exploring a Model of Situated Professional Development: Impact on Classroom Practice

A hallmark of current science education reform involves teaching through inquiry. However, the widespread use of inquiry-based instruction in many classrooms has not occurred (Roehrig and Luft in Int J Sci Educ 26:3–24, 2004; Schneider et al. in J Res Sci Teach 42:283–312, 2005). The purpose of this study was to investigate the impact of a professional development program on middle school science teachers’ ability to enact inquiry-based pedagogical practices. Data were generated through evaluation of teacher practice using the Reformed Teaching Observation Protocol (RTOP) (Sawada et al. in School Sci Math 102:245–253, 2002) at three distinct junctures, before, during, and after the professional development treatment. Analysis of teacher-participant post-institute reflections was then utilized to determine the perceived role of the various institute components. Statistical significant changes in RTOP scores indicated that the teachers were able to successfully transfer the enactment of the inquiry-based practices into their classrooms. The subsequent discussion provides connection between these pedagogical changes with use of professional development strategies that provide a situated learning environment.

Predation effect of three fish species and a shrimp on macrobenthos and meiobenthos in microcosms

The responses of macrofaunal and meiofaunal benthic communities to predation by three fish species and a penaeid shrimp were examined to evaluate the potential for epibenthic predators to reduce abundance of benthos. Experiments conducted in 1987 analysed only the macrofaunal community and indicated capitellid polychaete abundance was significantly reduced in the presence of white shrimp [ Penaeus setiferus (Linneaus)], while mummichogs [ Fundulus heteroclitus (Linneaus)] had no significant effect on any macrobenthic taxon. Experiments in 1988 using mullet ( Mugil cephalus Linneaus) as predators resulted in significantly decreased abundances of total meiofauna and the copepod Enhydrosoma propinquum (Brady), while abundances of macrofaunal prey were not significantly reduced. Abundances of the polychaete Streblospio benedicti Webster, total macrofauna and total copepods were significantly reduced by spot ( Leiostomus xanthurus Lacepede) predation. While these experiments were designed with sufficient power to demonstrate that epibenthic predators are possibly capable of causing significant reductions in the populations of macrofaunal and meiofaunal prey, a general paucity of significant impacts indicates that these predators may be but one of many factors influencing benthic abundance in the field. The microcosm experiment approach must incorporate multifactorial designs in the future.

Long-term trends of subtidal macrobenthos in North Inlet, South Carolina

Analyses of seasonal and yearly trends in subtidal macrobenthic samples collected bi-weekly at a sandy site (1981–1984) and a muddy site (1981–1985) in North Inlet, South Carolina, show large fluctations in abundance and high variability between replicate samples. Sampling variability at the sandy site, thought to be influenced more by physical disturbance than by biotic interactions, was especially high and prevented the interpretation of seasonal trends in abundance. Increased replication at the muddy site in 1985 revealed abundance patterns of winter/spring maxima and summer minima. Despite short-term (seasonal) and high year-to-year variability, the fauna at both sites were characterized by long-term stability in abundance. That is, although abundances varied considerably between seasons or years only 9 of 22 taxa analyzed showed a directional change in abundance. These 9 taxa increased in abundance over the four (sandy site) or five (muddy site) years of examination while the other 13 taxa fluctuated about a mean value. The taxonomic composition of benthic fauna at both sites was also very stable through time, with the sandy site always numerically dominated, in order, by polychaetes, amphipods, and bivalves and the muddy site by polychaetes, oligochaetes, and bivalves.

Quantitative cohort analysis of a sand-dwelling meiobenthic harpacticoid copepod

The life history, distribution, and abundance of a numerically dominant harpacticoid copepod, Huntemannia jadensis , was investigated on three intertidal sand beaches in Puget Sound, Washington, from January 1973 to September 1974. Abundance estimates based on five replicate 10 cm 2 core samples at weekly intervals had 95% confidence limits from 50% to 200% of the weekly mean. Most variability in abundance was associated with differences among tidal levels, with additional high variability between stations within a tidal level. Cohorts could be followed at a mean lower low water station on each beach and took about 6 months to mature. Two beachss produced one generation per year in summer, but the third beach had a major cohort in spring and a smaller cohort in winter. Instantaneous rates of population increase ranged from—0.30 to 0.22 per day in field populations. Differences in the sequence of cohort development among the three beaches were of sufficient magnitude that the ecological validity of selecting and single study area as a control site for comparative purpose is questioned.

Development of the sand-dwelling meiobenthic harpacticoid copepod huntemannia jadensis Poppe in the laboratory☆

Abstract Huntemannia jadensis Poppe, a common intertidal copepod in coastal waters of the north-western United States and British Columbia, Canada ranges in length from 0.1 mm at birth to 1.3 mm (adult female) and 1.5 mm for the larger of two male morphs. Body lenght alone is not a reliable indicator of the stage of development for ths species. All six naupliar and the first two copepodite stages are interstitial, but older stages are burrowers. Individual sand grains were grasped with antennae, first maxillae, and caudal rami for browsing attached diatoms. Males of both morphs clasped immature females up to several days before females molted to the adult stage and were inseminated. In cultures with daily addition of benthic diatoms, H. jadensis grew from egg to adult in 50 days at both 15 and 20°C, 66 days at 12°C, and 95 days at 8°C. Development never progressed past the naupliar stages at 4°C. Females lived for more than a year in culture, and a maximum of four broods per female was produced with broods 3 to 5 wk apart. A single observation of generation time (egg to egg) of 167 days was made at 8°C. aboratory egg moratality ranged from 17 to 83% per brood. Naupliar mortality was also very high, but copepodites suffered less than 25% mortality within each stage. Survivorship to maturity in the laboratory was highest at 8°C. Laboratory mortality patterns were similar to those observed in ield populations. Growth was so slow and cultures so difficult to mantain that H. jadensis is not recommended for future laboratory study of burrowing or interstitial harpacticoid copepods.

Serological estimation of prey-protein gut-residence time and quantification of meal size for grass shrimp consuming meiofaunal copepods.

A series of experiments using serological reagents was conducted to examine predation, ingestion and digestion in a model predator-prey system. The harpacticoid copepod Amphiascoides atopus, obtained from mass culture, was used as prey and the grass shrimp, Palaemonetes pugio, as predator. Bulk-gut passage time in P. pugio was measured by visualization of latex beads and ranged from 0.5 to 4 h in starved and continuously-fed grass shrimp. A polyclonal antibody was prepared from crude extracts of A. atopus; cross reactions with P. pugio and three other crustaceans were either negligible or not detected using slide agar-gel-double-immunodiffusion (AGID) and Western blot preparations. The presence of A. atopus antigens was detected with great sensitivity (e.g., seven copepods, 35 µg dry weight, gave positive results) in grass shrimp gut contents even when proteins of other crustacean prey were present. Prey-proteins could be detected for as long as 4 h with AGID and 8 h with Western blot techniques. Individual grass shrimp that were fed A. atopus and consumed from 0 to 98 copepods h(-1) were subjected to Western-blot preparation with chemiluminescence detection and densitometric evaluation. There was a significant curvilinear relationship between protein content and the number of copepod prey ingested. Results suggest that serological techniques can be modified to estimate the mass or abundance of standard-sized prey ingested by field-collected predators.