Two modified Breder traps for quantitative studies of tropical amphidromous migration

Amphidromy is a life cycle of fauna found throughout the tropics and subtropics, including representatives from three phyla. Amphidromy involves a life cycle of oceanic larval development, with postlarval migration into streams where growth and reproduction take place. With increasing industrial and urban development in tropical regions, demands for freshwater are continuously growing, resulting in the construction of dams and diversions that break the freshwater continuum necessary for the amphidromous life cycle; thus, jeopardizing many populations of native and endemic tropical stream fauna. Because of this, more quantitative studies are needed to better understand this unique life cycle, which heretofore, has been relatively little studied compared to tropical terrestrial communities. As such, new and quantitative methods are needed to study the immature stages (e.g., postlarvae) associated with amphidromy. In this paper, we introduce two modifications of the original Breder trap that have been designed specifically for standardized, quantitative monitoring of amphidromous postlarval migration. In addition, the two modified traps can be used in a variety of stream settings from natural bed substrates to modified channels with little heterogeneity. The first modification is made of acrylic, with a flat bottom useful in channelized streams or streams with relatively flat, unnatural benthic substrate (e.g., concrete). The second modification is an affordable trap made from polyvinylchloride (PVC) compression couplings, to be used in streams with natural benthic substrates, particularly those with large, embedded and immovable boulders and bedrock outcrops. Both traps were designed for continuous water flow through the traps, providing the necessary rheotactic cue for migrating amphidromous postlarvae, and ameliorating deficiencies of earlier traps not intended for tropical amphidromous fauna. We also make recommendations for standardized use of these traps to facilitate data comparisons among studies.     

Hitchhiking behaviour in the obligatory upstream migration of amphidromous snails

Migratory animals endure high stress during long-distance travel in order to benefit from spatio-temporally fluctuating resources, including food and shelter or from colonization of unoccupied habitats. Along with some fishes and shrimps, nerite snails in tropical to temperate freshwater systems are examples of amphidromous animals that migrate upstream for growth and reproduction after a marine larval phase. Here I report, to my knowledge, the first example of ‘hitchhiking’ behaviour in the obligatory migration of animals: the nerite snail Neritina asperulata appears to travel several kilometres as minute juveniles by firmly attaching to the shells of congeneric, subadult snails in streams of Melanesian Islands, presumably to increase the success rate of migration.     

Skip of the routine habitat in an amphidromous migration of ayu

Ayu Plecoglossus altivelis is a typical amphidromous fish with ontogenic requirements for habitats among lower reaches of a river, the marine coastal area, and middle reaches of a river at the immature adult stage. Mature fish that had a small body size like ordinary young were found around the spawning ground. In comparison with standard adults, the migratory histories of the dwarf adults were examined using otolith microchemistry analysis. Sr:Ca ratio estimated that the dwarf fish were exposed to saline or brackish water after once moving into the river, whereas the standard-size fish migrated upstream.     

The Use of Two Modified Breder Traps to Quantitatively Study Amphidromous Upstream Migration

Amphidromous stream fauna represent three phyla that have a tropical distribution among oceanic islands, with a few continental representatives. This lifecycle involves marine larval development, with postlarval migration, growth and reproduction as adults occurring in freshwater streams. Many tropical archipelagoes are on the brink of heavy commercial development, threatening freshwater resources in tropical regions. Because of this threat and the isolated nature of tropical islands, quantitative studies are needed to better understand this unique lifecycle. In this paper, we present the use of two modifications of the original Breder trap to study the migration dynamics of tropical amphidromous fish and shrimp postlarvae. The first modification was used in a cemented and channelized stream. The second modification was used in two streams with natural substrates of large, embedded and immovable boulders and basalt outcrops. Quantitative trapping was standardized by time and numbers of traps used, to give results presented as postlarvae trap^–1 h^–1. The number of traps used in the natural streams was based on channel width at the trapping location (i.e., equal number of traps per meter), thus providing equivalent trapping effort between streams of different sizes and flow magnitude. Both trap designs were useful for quantitative monitoring of postlarvae over several months and years, among different streams, and were equally practical for assessing diel and species-specific migration dynamics. Postlarval recruitment of Hawaiian amphidromous species showed temporal variation between months and years within the same stream, significant differences between two streams of different flow magnitude, and distinct diel patterns in diurnal and nocturnal fish and shrimp migration, respectively. A direct correlation between stream flow and total fish postlarval migration was documented.     

Evolution of the organization for tropical studies

The Organization for Tropical Studies (OTS)/Organización para Estudios Tropicales (OET) has evolved in many ways since its founding in 1963 as a non-profit consortium offering graduate courses and facilitating research in tropical ecology in Costa Rica. By 2002, its international membership included about 65 institutions, including four from Costa Rica. It had developed three Costa Rican field stations (La Selva, Las Cruces, and Palo Verde) with excellent facilities for teaching and research, and it was constructing a new Costa Rican office at the University of Costa Rica. Combinations of internal and external pressures influenced OTS to develop in new directions in the 1980s and 1990s. It became more diversified and more concerned with applied science in its traditional areas of graduate education and research facilitation. The Organization also evolved into new niches: more applied biology, professional education, environmental education and policy, conservation efforts, and an expanded geographic distribution to other Latin American countries. OTS was composed of changing combinations of people (Boards, members, staff) with evolving and competing priorities for limited financial resources. External environmental changes also shaped OTS's evolution. New problems of increased tropical deforestation, the emergence of the biodiversity "crisis" and conservation biology, global climate change, and calls for sustainable development affected OTS constituents and funding priorities of governments and foundations. Both internal and external pressures have in some cases demanded for OTS to improve its relationship with: Costa Rican biologists and their institutions, the Costa Rican government, and Costa Ricans living around the three OTS field stations.     

Lekking birds in a tropical forest forego sex for migration

Facultative, partially migratory animals provide a contemporary window into the evolution of migration, offering rare opportunities to examine the life-history trade-offs associated with migration. For the first time, to our knowledge, we describe the nature of these trade-offs, using a lek-breeding tropical bird, the white-ruffed manakin (Corapipo altera). Previous evidence indicated that weather drives post-breeding migration to lower elevations bringing condition-related benefits. Using elevation-sensitive stable isotope measurements and more than 1200 h of behavioural observations, we show that male manakins which migrate incur costs of diminished social status and matings with females the following breeding season. Because migratory tendency depends on inter-annual variation in weather, physical costs of displays and breeding prospects the following year, migratory decisions are subject to both natural and sexual selection, with the outcome of such decisions linked to changing climatic regimes.     

A comparison of two common flight interception traps to survey tropical arthropods

Tropical forests are predicted to harbor most of the insect diversity on earth, but few studies have been conducted to characterize insect communities in tropical forests. One major limitation is the lack of consensus on methods for insect collection. Deciding which insect trap to use is an important consideration for ecologists and entomologists, yet to date few study has presented a quantitative comparison of the results generated by standardized methods in tropical insect communities. Here, we investigate the relative performance of two flight interception traps, the windowpane trap, and the more widely used malaise trap, across a broad gradient of lowland forest types in French Guiana. The windowpane trap consistently collected significantly more Coleoptera and Blattaria than the malaise trap, which proved most effective for Diptera, Hymenoptera, and Hemiptera. Orthoptera and Lepidoptera were not well represented using either trap, suggesting the need for additional methods such as bait traps and light traps. Our results of contrasting trap performance among insect orders underscore the need for complementary trapping strategies using multiple methods for community surveys in tropical forests.     

A comparativist manifesto for international migration studies

Abstract

Drawing on thirteen years of fieldwork among Mexican migrants in the United States and Mexico and comparisons of immigration policy throughout the Americas, this paper systematically elaborates the advantages and disadvantages of different kinds of multi-sited studies. A reformed logic of the Millian methods of agreement and difference takes into account the causal connections among the cases. I call for a ‘homeland dissimilation’ perspective and comparisons of internal and international migration as a way to take off the self-imposed national blinders that pre-determine many of the conclusions of the assimilation and even transnationalism literatures.     

A modified wire-loop method for quantitative electron microscopic radioautography

Summary The distribution of reaction for acid and alkaline phosphatases in the proximal cartilage of the os penis and the mandibular condylar cartilage has been compared. The distribution of acid phosphatase in the two structures seems to be identical, whereas the distribution of alkaline phosphatase in the os penis cartilage seems to differ from that in the mandibular condylar cartilage and, by this, from all other studied growth cartilages.     

A fast and robust quantitative time-lapse assay for cell migration

We describe a simple and widely applicable method to measure cell migration in time-lapse sequences of fluorescently labeled cells in culture. Briefly, binarized cell images obtained after thresholding were cumulatively projected, and the covered areas were measured. This procedure determines the time course of the track area successively covered by the cell population. Under conditions where cell growth is negligible, a robust index of cell motility is derived from normalized plots for the displacement of cells over time. We applied this method to quantitatively examine the migration of B35 neuroblastoma cells transiently expressing GFP and to C6 glioma cells after staining with Hoechst 33258. This sensitive assay detected the influence of agents which inhibit actin polymerization (cytochalasin B) or interfere with the maintenance of cell polarity (methyl-beta-cyclodextrin) on cell migration. Thus, this assay is a versatile tool to measure quickly the migration of different cell types using different labeling strategies.     

Evidence of seasonal migration in a tropical subterranean vertebrate

Many animals undergo migrations that depend on a range of biotic or abiotic factors provoking daily, seasonal or annual movement of individuals and/or populations. Temperate amphibians frequently have their life cycles dominated by annual temperature fluctuations, but in the tropics it is often presumed that distinct rainy seasons will influence amphibians more than small changes in temperature. Here, we direct the seasonal changes in abundance hypothesis to a caecilian amphibian Boulengerula boulengeri found in monthly randomized quantitative surveys in the top 30 cm of soil. Meteorological data are used to interpret the significant changes found in relation to rainfall and temperature variables. Instead of the expected correlation of migration with rainfall, we find that frequency varies significantly and positively with temperature. In addition, data on the depth at which individual caecilians are collected suggest that animals undergo a vertical (rather than horizontal) migration within the soil. This is the first example of vertical migrations with temperature (as opposed to rainfall) of any tropical subterranean fauna. We discuss the possible influences that stimulate migration in this species (abiotic factors, feeding, reproduction and predation). The ecology of caecilians has lagged behind that of all other tetrapods, and this study has importance for future ecological studies, as well as biodiversity assessments and monitoring methodologies.     

A review of quantitative methods for proteomic studies

An overview is provided of six strategies for relative or absolute quantitation of protein abundances that are widely used in proteomic studies. Strengths and limitations are discussed. Four of these involve stable isotope labeling and isotope ratio measurements by mass spectrometry. In another, mass spectra are used to deconvolute overlapping peptide HPLC peaks to provide relative quantitation based on peak areas. The sixth provides relative abundances of proteins based on 2-D gel arrays. It should be noted that these strategies measure peptide and protein abundances, and cannot directly assess changes in regulation or expression.     

Microfluidic tools for quantitative studies of eukaryotic chemotaxis

Over the past decade, microfluidic techniques have been established as a versatile platform to perform live cell experiments under well-controlled conditions. To investigate the directional responses of cells, stable concentration profiles of chemotactic factors can be generated in microfluidic gradient mixers that provide a high degree of spatial control. However, the times for built-up and switching of gradient profiles are in general too slow to resolve the intracellular protein translocation events of directional sensing of eukaryotes. Here, we review an example of a conventional microfluidic gradient mixer as well as the novel flow photolysis technique that achieves an increased temporal resolution by combining the photo-activation of caged compounds with the advantages of microfluidic chambers.     

Two modified techniques for flexor tendon repair.

The aim of this article is to present two new techniques for digital flexor tendon repair: a modification to the conventional Kessler technique (wrap core suture) and tendon splints (H-shaped splint). These techniques were aimed at enhancing the biomechanical properties of such repairs as related to resistance to both gap formation and repair failure. Comparing (in an ex vivo study) the tensiometric properties (gap formation and failure strengths) of 24 flexor digitorum profundus tendons repaired with the described techniques (12 repairs per each technique) and the conventional Kessler repair (24 repairs), we found that the former provided significantly stronger repairs than the latter in vitro. A statistically significant difference (p < 0.001) was found between each of the two presented techniques and the Kessler repair. The wrap core suture increased the load at which a visible (1 mm) gap formed by 22.6 percent when compared with the conventional Kessler suture. The mean gap strength of the wrap core repair was 6.5 N, whereas that of the conventional Kessler was 5.3 N. The failure loads (ultimate strength) of the wrap core suture were 33.8 percent higher than those of the conventional Kessler. The mean breaking load of the wrap core repair was 19.4 N, whereas that of the conventional Kessler was 14.5 N. The H-splint repair increased the load at which a visible gap formed and the failure loads (ultimate strength) by 158.5 and 333.1 percent, respectively, when compared with the conventional Kessler suture. The mean gap strength of the H-splint repair was 13.7 N, and its mean breaking load was 62.8 N.     

Fluorescent dyes for lymphocyte migration and proliferation studies

Fluorescent dyes are increasingly being exploited to track lymphocyte migration and proliferation. The present paper reviews the properties and performance of some 14 different fluorescent dyes that have been used during the last 20 years to monitor lymphocyte migration. Of the 14 dyes discussed, two stand out as being the most versatile in terms of long-term tracking of lymphocytes and their ability to quantify lymphocyte proliferation. They are the intracellular covalent coupling dye carboxyfluorescein diacetate succinimidyl ester (CFSE) and the membrane inserting dye PKH26. Both dyes have the advantage that they can be used to track cell division, both in vitro and in vivo, due to the progressive halving of the fluorescence intensity of the dyes in cells after each division. However, CFSE appears to have the edge over PKH26 based on homogeneity of lymphocyte staining and cost. Two other fluorescent dyes, although not suitable for lymphocyte proliferation studies, are valuable tracking dyes for short-term (up to 3 day) lymphocyte migration experiments, namely the DNA-binding dye Hoechst 33342 and the cytoplasmic dye calcein. In the future it is highly likely that additional fluorescent dyes, with different spectral properties to CFSE, will become available, as well as membrane inserting fluorescent dyes that more homogeneously label lymphocytes than PKH26.