Metamorphosis of the Hawaiian Stream Goby Sicyopterus Stimpsoni: A Structural, Functional, and Behavioral Analysis.

The endemic goby Sicyopterus stimpsoni is unique among five species of Hawaiian freshwater fishes because it undergoes rapid metamorphosis of cranial structures during postlarval development. These fishes are amphidromous and return after a prolonged stay in the ocean to streams where they are confined to estuaries until completion of cranial restructuring. Within 48 hours after entering fresh water, head width increases significantly, while total length and head length remains unchanged. Weight decreases by approximately 15% during this period. The upper lip enlarges greatly, and the mouth position shifts from terminal to nearly ventral. Shape analysis of radiographs taken from a sequence of fish preserved at two-hour intervals after entering fresh water revealed drastic reallocation of the premaxilla-maxilla complex and dentary. The cranium and most dorsal and caudal structures of the skull remained unchanged. Microscopic observations showed development of a buccal velum, a ridge on the lower lip, and a greatly enlarged upper lip during metamorphosis. In the second half of metamorphosis, tooth buds develop, and a gland in the upper lip becomes prominent. After completion of metamorphosis, Sicyopterus stimproni is able to climb waterfalls by alternating use of the pelvic sucking-disk and mouth, with which it also is able to scrape diatoms from rock surfaces by rapid rostrocaudal movement of the upper-jaw complex. Anatomical analysis of adult fish suggested a four-bar-linkage model for feeding and climbing; it consists of the (1) cranium, (2a) hyomandibular-quadrate-triangle, (b) lower jaw complex, (3) upper jaw complex, and (4) palatine-ectopterygoid axis. The premaxilla-ethmoidal ligament and interopercular-articular ligament provide elasticity to the model. Non-linear, highly dynamic cranial development with extensive reallocation of cranial function has not been described previously for fishes, and the analysis provides a unique example for the theory of terminal addition during ontogeny of an organism. A relatively small change in structure at the end of larval development has enormous implications for the entire ontogeny of the species. The metamorphosis of Sicyopterus stimpsoni constitutes a departure from typical linear development in the transition from larva to adult, and can be used to hypothesize evolutionary mechanisms guiding the phylogeny of a taxon

The Effects of Homogenized Cream and Commercial Buttermilk Powder on Low-Fat Cheddar Cheese.

Seventy percent reduced fat Cheddar cheese was manufactured with homogenized cream and sweet cream buttermilk powder in an effort to improve flavor and texture characteristics. Manufacturing procedures, as well as the chemical, physical and sensory attributes. Pasteurized cream was homogenized (15.8 MPa) with and without the addition of buttermilk powder. The cream was added to pasteurized skim milk to produce two vats of cheese, one with and one without buttermilk powder. After milling, each vat was split to produce a washed curd and normal curd cheese. The four cheeses were sampled at week one, and months one, two and four. Both buttermilk cheeses had a stronger cheddar flavor, described as sulfide, by the fourth month. There was no significant difference in the percent of citric acid pH 4.6 soluble nitrogen between control and treatment cheeses. The percent of soluble nitrogen increased over time for all groups. Gel electrophoresis failed to identify fat globule membrane proteins from the buttermilk powder in the 4 month old cheeses. Membrane proteins were found in the wheys of both treatment and control cheeses. Analysis of the free fatty acids was conducted on the extracts of the cheese by solid phase extraction and gas chromatography. No significant differences were noted. Reversed phase HPLC of the citric acid and pH 4.6 soluble peptide fractions identified one peak as having a consistently greater area in the buttermilk cheese. Sensory analysis was conducted on lowfat cheese made with homogenized cream and lowfat cheese made with homogenized cream and buttermilk powder. An experienced panel of 8 conducted attribute analysis. Control cheeses were firmer, more crumbly and more curdy than the buttermilk cheeses. Buttermilk cheeses were more bitter, acid, sulfide, unclean and had a stronger flavor than the control. Consumer evaluations were conducted at 2, 3 and 4 months of aging. Buttermilk cheese had a significantly softer texture in the first panel at two months of aging. The control cheese was preferred for flavor and overall liking after three and four months of aging

Stairway to Heaven: Evaluating Levels of Biological Organization Correlated with the Successful Ascent of Natural Waterfalls in the Hawaiian Stream Goby Sicyopterus stimpsoni

Selective pressures generated by locomotor challenges act at the level of the individual. However, phenotypic variation among individuals that might convey a selective advantage may occur across any of multiple levels ofbiological organization. In this study, we test for differences in external morphology, muscle mechanical advantage, muscle fiber type and protein expression among individuals of the waterfall climbing Hawaiian fish Sicyopterus stimpsoni collected from sequential pools increasing in elevation within a single freshwater stream. Despite predictions from previous laboratory studies of morphological selection, few directional morphometric changes inbody shape were observed at successively higher elevations. Similarly, lever arm ratios associated with the main pelvic sucker, central to climbing ability in this species, did not differ between elevations. However, among climbingmuscles, the adductor pelvicus complex (largely responsible for generating pelvic suction during climbing) contained a significantly greater red muscle fiber content at upstream sites. A proteomic analysis of the adductor pelvicusrevealed two-fold increases in expression levels for two respiratory chain proteins (NADH:ubiquinone reductase and cytochrome b) that are essential for aerobic respiration among individuals from successively higher elevations.Assessed collectively, these evaluations reveal phenotypic differences at some, but not all levels of biological organization that are likely the result of selective pressures experienced during climbing

Characteristics of Perennial Wheatgrass (Thinopyrum intermedium) and Refined Wheat Flour Blends: Impact on Rheological Properties

Intermediate wheatgrass (IWG) (Thinopyrum intermedium) is a perennial grass with desirable agronomic traits and positive effects on the environment. It has high fiber and protein contents, which increase the interest in using IWG for human consumption. In this study, IWG flour was blended with refined wheat at four IWG-to-wheat ratios (0:100, 50:50, 75:25, and 100:0). Samples were analyzed for proximate composition, microstructure features, pasting properties (Micro Visco-Amylo-Graph device), protein solubility, and total and accessible thiols. Gluten aggregation properties (GlutoPeak tester) and mixing profile (Farinograph-AT device) were also evaluated. IWG flour enrichment increased the pasting temperature and decreased the peak viscosity of blended flours. IWG proteins exhibited higher solubility than wheat, with a high amount of accessible and total thiols. The GlutoPeak tester highlighted the ability of IWG proteins to aggregate and generate torque. Higher IWG flour enrichment resulted in faster gluten aggregation with lower peak torque, suggesting weakening of wheat gluten strength. Finally, the addition of IWG to refined wheat flour resulted in a decrease in dough development time and an increase in consistency, likely because of the higher levels of fiber in IWG. The 50% IWG flour enrichment represents a good compromise between nutritional improvement and maintenance of the pasting properties, protein characteristics, and gluten aggregation kinetics

An ecotoxicologically relevant approach to water quality monitoring for contaminants of emerging concern

Contaminants of Emerging Concern (CECs) have been documented across the seven continents, including Antarctica, and are likely an impediment to the sustainable management of natural resources. Most studies to date have relied on sweeping chemistry surveys, reliant upon sophisticated instrumentation. This approach is expensive, relies on limited laboratory capacity, and generates results that are spatially and temporally constrained. Here we review existing approaches that can overcome these limitations by focusing on effects-based monitoring. Passive samplers can generate long-term records regarding the occurrence of CECs. As samples are concentrated, their analysis can be achieved using equipment that will be more common and less expensive. A second approach involves rapid test methods for single compounds, including test strips, ELISA assays, and mobile phone-based analytic tools. These can provide inexpensive CEC presence data for many field sites and can be used to stratify sampling and thereby reduce cost. Identifying the presence of a single compound can often shed light on the likely presence of entire groups of chemicals. Pairing these chemistry-derived approaches with geospatial modeling to predict CEC presence and concentrations across watersheds has already been applied in several large watersheds. Utilizing available ecotoxicological knowledge bases provides an opportunity to link modeled CEC occurrence and concentrations with likely adverse biological responses. Finally, confirmatory on-site exposure experiments can corroborate the presence or absence of biological effects hypothesized from the above chain of evidence to provide natural resource managers with information to make conservation decisions

Performance and scaling of a novel locomotor structure: adhesive capacity of climbing gobiid fishes

Many species of gobiid fishes adhere to surfaces using a sucker formed from fusion of the pelvic fins. Juveniles of many amphidromous species use this pelvic sucker to scale waterfalls during migrations to upstream habitats after an oceanic larval phase. However, adults may still use suckers to re-scale waterfalls if displaced. If attachment force is proportional to sucker area and if growth of the sucker is isometric, then increases in the forces that climbing fish must resist might outpace adhesive capacity, causing climbing performance to decline through ontogeny. To test for such trends, we measured pressure differentials and adhesive suction forces generated by the pelvic sucker across wide size ranges in six goby species, including climbing and non-climbing taxa. Suction was achieved via two distinct growth strategies: (1) small suckers with isometric (or negatively allometric) scaling among climbing gobies and (2) large suckers with positively allometric growth in non-climbing gobies. Species using the first strategy show a high baseline of adhesive capacity that may aid climbing performance throughout ontogeny, with pressure differentials and suction forces much greater than expected if adhesion were a passive function of sucker area. In contrast, large suckers possessed by non-climbing species may help compensate for reduced pressure differentials, thereby producing suction sufficient to support body weight. Climbing Sicyopterus species also use oral suckers during climbing waterfalls, and these exhibited scaling patterns similar to those for pelvic suckers. However, oral suction force was considerably lower than that for pelvic suckers, reducing the ability for these fish to attach to substrates by the oral sucker alone

Assessing the effects of exposure timing on biomarker expression using β-estradiol

Temporal and spatial variability in estrogenicity has been documented formanytreated wastewater effluents with the consequences of this variability on the expression of biomarkers of endocrine disruption being largely unknown. Laboratory exposure studies usually utilize constant exposure concentrations which may produce biological effects that differ from those observed in organisms exposed in natural environments. In this study, we investigated the effects of differential timing of exposures with 17β - estradiol (E2) on a range of fathead minnow biomarkers to simulate diverse environmentally relevant exposure profiles. Two 21-day, replicate experiments were performed exposing mature male fathead minnows to E2 at time-weighted mean concentrations (similar average exposure to the contaminant during the 21-day exposure period; 17 ng E2/L experiment 1; 12 ng E2/L experiment 2) comparable to E2 equivalency values (EEQ) reported for several anthropogenically altered environments. A comparable time-weighted mean concentration of E2 was applied to five treatments which varied in the daily application schema: E2 was either applied at a steady rate (ST), in a gradual decreasing concentration (HI), a gradual increasing concentration (LO), applied intermittently (IN), or at a randomly varying concentration (VA). We assessed a range of widely used physiological (vitellogenin mRNA induction and plasma concentrations), anatomical (body and organ indices, secondary sex characteristics, and histopathology), and behavioral (nest holding) biomarkers reported to change following exposure to endocrine active compounds (EACs). All treatments responded with a rise in plasma vitellogenin concentration when compared with the ethanol carrier control. Predicatively, vitellogenin mRNA induction, which tracked closely with plasma vitellogenin concentrations in most treatments was not elevated in the HI treatment, presumably due to the lack of E2 exposure immediately prior to analysis. The ability of treatment male fish to hold nest sites in direct competition with control males was sensitive to E2 exposure and did yield statistically significant differences between treatments and carrier control. Other biological endpoints assessed in this study (organosomatic indices, secondary sex characteristics) varied little between treatments and controls. This study indicates that a broad suite of endpoints is necessary to fully assess the biological consequences of fish exposure to estrogens and that for at least field studies, a combination of vitellogenin mRNA and plasma vitellogenin analysis are most promising in deciphering exposure histories of wild-caught and caged fishes

Terra (aqua) incognita : knowledge gaps in global ecotoxicology

The peer-reviewed toxicological literature contains twice as many studies pertaining to the River Thames (United Kingdom) than to the Congo River (Central Africa), despite the latter's watershed being roughly 250 times larger and sustaining a 5-fold greater human population (Web of Science database). Protecting such underresearched natural resources from chemical contamination requires local research to fill knowledge gaps, attention to regional expertise, and incorporation of local communities into the decision-making process. The support of regional, collaborative networks may be the most important of these because they will be most responsive to emerging ecotoxicological concerns as they develop.This article also appears in: Contaminants of Emerging Concern: Addressing Data Gaps with a Focus on Developing Countrieshttps://setac.onlinelibrary.wiley.com/journal/15528618hj2022Chemistr

Contaminants of Emerging Concern in The North American Great Lakes: Evidence of Reproductive Disruption from Field and Laboratory Studies

Analysis of water samples collected at 54 sites in the Great Lakes Watershed confirmed the ubiquitous presence of Contaminants of Emerging Concern (CECs). Cluster analyses of CECs suggest that the co-occurrence of CECs is linked to dichotomous urban or agricultural land use. Urban mixtures contained steroidal estrogens, BPA, alkyphenols, pharmaceuticals and personal care products. Agricultural samples contained herbicides, pesticides, BPA, and alkylphenols. Resident and caged sunfish were collected from 27 sampling sites and analyzed for indicators of stress associated with CEC exposure. At high aqueous CEC concentrations, glucose concentrations spiked in sunfish plasma and liver cells exhibited toxic stress response. Canonical correspondence analyses revealed that concurrent with indicators of toxic stress, biomarkers of reproductive potential declined. To further examine the population level consequences, fathead minnows were exposed in the laboratory for three generations to the empirically derived CEC mixtures at environmentally relevant concentrations and found to alter fecundity. This integrated series of studies indicates that CECs in Great Lakes tributaries may impact fish population health and sustainability.Ope