Oligogalacturonate hydrolase with unique substrate preference from the pulp of parsley roots

The main form of pectate hydrolases in the cell wall of parsley roots showed a unique substrate preference of a plant exopolygalacturonase because it clearly preferred the substrates with degree of polymerization about 10. This form was separated from the others, purified and characterized. Enzyme exhibited sharp pH optimum corresponding to pH 4.7, molecular mass 53.5 kDa, and isoelectric point 5.3. It was stable at 50°C in 2-h assay and had optimum of temperature at 60°C (activation energy being 37.0 kJ/mol). The interaction with concanavalin A indicated the glycosylation of enzyme. Substrates were cleaved from the non-reducing end.     

Substrate selection by juvenile Atlantic cod (Gadus morhua): effects of predation risk

Although predator avoidance has been proposed as one possible factor influencing the distribution of fish among substrate types, no study has addressed this question directly. Groups of juvenile Atlantic cod were offered a choice between pairs of the following three substrates: sand, gravel-pebble and cobble. Their distribution on these substrates was compared prior to, during and following exposure to a predator (i.e. a larger conspecific). With no apparent risk of predation, juvenile cod preferred sand or gravel-pebble. When cobble was present, juveniles hid in the interstitial spaces of this substrate in the presence of a predator. With no cobble present, juveniles showed no preference between sand and gravel-pebble, and did not seek refuge from predation in association with these substrates. Following exposure to a predator (i.e. 2.5 h later) larger juvenile cod again showed a preference for the finer-grained substrates, but smaller individuals continued to associated with the cobble. The presence of cobble resulted in fewer juveniles being captured and a significant increase in the latency until the first juvenile was captured by the predator. Results are discussed with respect to the effects of predation on the distribution and survival of fishes among substrate types.     

Effect of acclimation temperature and substrate type on selected temperature,movement and activity of juvenile spiny softshell turtles (Apalone spinifera) in an aquatic thermal gradient

In some turtle species, temperature selection may be influenced by environmental conditions, including acclimation temperature and substrate quality. These factors may be particularly important for softshell turtles that are highly aquatic and often thermoregulate by burying in the substrate in shallow water microhabitats. We tested for effects of acclimation temperature (22 °C or 27 °C) and substrate type (sand or gravel) on the selected temperature and movement patterns of 20 juvenile spiny softhshell turtles (Apalone spinifera; Reptilia: Trionychidae) in an aquatic thermal gradient of 14–34 °C. Among 7–11 month old juvenile softshell turtles, acclimation temperature and substrate type did not influence temperature selection, nor alter activity and movement patterns. During thermal gradient tests, both 22- and 27 °C-acclimated turtles selected the warmest temperature (34 °C) available most frequently, regardless of substrate type (sand or gravel). Similarly, acclimation temperature and substrate type did not influence movement patterns of turtles, nor the number of chambers used in the gradient tests. These results suggest that juvenile Apalone spinifera are capable of detecting small temperature increments and prefer warm temperatures that may positively influence growth and metabolism, and that thermal factors more significantly influence aquatic thermoregulation in this species than does substrate type.     

Influence of peat substrate on the distribution and behaviour patterns of sand shrimp, Crangon septemspinosa, under experimental conditions

Peat harvesting is a lucrative industry in New Brunswick, Canada, and is for the most part located along the coast. Current methods of mining peatlands are such that high levels of peat fibers are transported by runoff into fresh and marine waters. To understand better the influence of peat substrate on aquatic organisms living in peat‐impacted habitats, the sand shrimp (Crangon septemspinosa) was used as a bioindicator. A series of laboratory experiments was conducted in which shrimp were provided with a choice between sand and peat. Long‐term studies on starved shrimp confirmed that whereas foraging activities took place on both substrates, shrimp display an overall preference for sand (73% of all shrimp observed were on sand, n=60). When food was deposited on each of the substrates, shrimp generally opted to feed on sand (75% of all shrimp observed were on sand, n=60). After all food on sand was consumed, shrimp tended to move to peat. This was followed by a short period of foraging on both sand and peat with an eventual return to sand in most instances. The presence of food on both substrates did not influence their preference for sand. However, shrimp will move onto a peat substrate to forage if food is present only there. This observation suggests that, although there is a marked preference for sand, peat is not completely repellent to them. Finally, histological investigations of the shrimp digestive system revealed that peat was ingested with food particles and processed in the gastric mill. There was, however, no discernible discrimination between the two substances during ingestion. Finally, starved shrimp on peat substrate did not ingest peat fibers, suggesting that peat is not perceived as an alternative food source.     

A heterogeneous thermal environment enables remarkable behavioral thermoregulation in Uta stansburiana

Ectotherms can attain preferred body temperatures by selecting specific temperature microhabitats within a varied thermal environment. The side‐blotched lizard, Uta stansburiana may employ microhabitat selection to thermoregulate behaviorally. It is unknown to what degree habitat structural complexity provides thermal microhabitats for thermoregulation. Thermal microhabitat structure, lizard temperature, and substrate preference were simultaneously evaluated using thermal imaging. A broad range of microhabitat temperatures was available (mean range of 11°C within 1–2 m²) while mean lizard temperature was between 36°C and 38°C. Lizards selected sites that differed significantly from the mean environmental temperature, indicating behavioral thermoregulation, and maintained a temperature significantly above that of their perch (mean difference of 2.6°C). Uta's thermoregulatory potential within a complex thermal microhabitat structure suggests that a warming trend may prove advantageous, rather than detrimental for this population.     

Microhabitat selection in intertidal gobiid fishes: Species- and size-associated variation

Patterns of space use and the individual-based behaviour of microhabitat selection were investigated in three intertidal gobiid fishes, Bathygobius fuscus, Chaenogobius annularis and C. gulosus, from Kyushu, southern Japan. While the three species tended to occupy slightly different types of tidepool, their patterns of distribution largely overlapped in the field. Laboratory experiments involving choice of shelter (i.e. underneath a stone plate) and four different substrate types were conducted to examine size- and time-related variation in habitat selection. The shelter area was preferred by small- and large-sized C. gulosus (day and night), large C. annularis (day and night) and small C. annularis (daytime only), while no preference was evident in small B. fuscus (day and night) and small C. annularis (night). Patterns of substrate choice also differed among species, size groups and between day and night. Size differences in substrate use were evident in B. fuscus and C. gulosus but not in C. annularis, while diel differences were shown by all species groups except large B. fuscus. The gravel and sand substrates tended to be used more frequently than the bare rock substrate, but the strength of preference of a particular substrate type varied among individuals/species. Our results demonstrate that habitat selection by the three gobiid species is variable depending on species, body size and time of day, which must ultimately bear upon mitigating intra-/interspecific interactions in tidepool environments.     

Lake sturgeon spawning on artificial habitat in the St Lawrence River

In 1996, lake sturgeon (Acipenser fulvescens) spawning was documented for the third consecutive year on an artificially placed gravel bed in the St Lawrence River. Two distinct spawning periods were observed in 1996. Spawning initially commenced on 17 June, when water temperature reached 15°C. A second spawning event was documented from 28 June to 1 July (16°C). Sturgeon egg densities were monitored in three transects on egg trays, on the gravel surface, and within interstitial spaces in the gravel. Counts of developing eggs in the gravel bed during both spawning periods were used to estimate a total of 275 000 eggs on the study area (0.075 ha). Average egg density was highest in the transect with the highest water velocities. Lake sturgeon fry were first observed in the gravel on 24 June (15.5°C), and first emergence from the gravel was documented on 28 June. Hatching following the second spawning event commenced on 3 July. Based on assessment of average embryo viability (61.6%) and egg‐to‐emergent fry survival (17.6%) an estimate of about 171 000 sturgeon eggs hatched, producing over 49 000 emergent fry. Current velocity, substrate particle size, depth of substrate, and maintenance of sediment‐free interstitial spaces are important considerations in planning future spawning habitat enhancement projects.     

Initial preference for plant species and state during oviposition site selection by an odonate

Endophytic egg‐laying odonates use an ovipositor to insert their eggs inside plant tissues. Before egg deposition, oviposition site selection consists of two crucial steps: (i) the initial choice, typically decided in species that oviposit in tandem within vertical substrates by the male when landing and then by the female by staying on the substrate or flying to another; and (ii) the insertion site choice, made by the female who uses her ovipositor to palpate the substrate. Some odonates prefer to deposit their eggs within specific plant species. Some are able to discriminate between living and dead substrates during the initial choice. However, the extent to which odonates discriminate among distinct plant species during the initial choice is unknown. We studied the initial site preference in Lestes macrostigma (Odonata: Lestidae) to determine whether the males and/or females show a distinct preference among five types of shoots when landing on or when palpating the substrate, respectively. Male L. macrostigma preferred to land on Bolboschoenus maritimus and dead Juncus spp. When focusing on J. maritimus, females preferentially palpated the substrate when the male landed on dead shoots. We suggest that the male preference for these substrates is consistent with that of the female during insertion site choice but also during egg deposition. Such behavior should reduce the duration of oviposition, with benefits of reducing the predation risk and increasing available time for foraging. The advantage in preferring these substrates should be linked to a selection pressure acting on egg development and/or survival.     

Determination of substrate preferences of tench, Tinca tinca (L.), under controlled experimental conditions

The substrate preference of tench Tinca tinca (L.), 33 2‐year‐old individuals, mean size 10 ± 0.36 cm total length, was determined using four different substrates (concrete, artificial vegetation, sand and mud) in a 26 m long maquette. The species showed a high preference (100%) for the mud. Six more trials were performed combining the substrates by pairs (concrete–vegetation, concrete–mud, concrete–sand, mud–vegetation, mud–sand, sand–vegetation). Selection order was: mud (100% of the individuals when compared with concrete and sand and 98.26 ± 2.68% when compared with artificial vegetation), artificial vegetation (100% of the individuals when compared with concrete and 99.81 ± 0.76% when compared with sand), sand (98.29 ± 3.66% when compared with concrete) and concrete.     

Oviposition preference for novel versus normal food resources in laboratory populations ofDrosophila melanogaster

Female fecundity, oviposition preference and specificity on one normal and two novel food media were assayed on four laboratory populations ofDrosophila melanogaster, revealing considerable among- and within-population variation in oviposition preference. Overall, there was a significant tendency of females to prefer novel media to their normal banana food as an oviposition substrate. Specificity in the populations was fairly high, implying that a large proportion of females tended to lay the majority of their eggs on the preferred medium. The results showed that oviposition preference for a given food medium could be affected by the alternative provided, and that, consequently, oviposition preference for a given food medium versus another cannot be predicted based upon a knowledge of what the preference for each of the two media was versus a common third medium. Specificity, on the other hand, was not significantly affected by the type of alternative food media provided in a given trial. Moreover, comparison of results from fecundity and oviposition preference assays also showed that the egg laying behaviour ofDrosophila females in response to different food media may be different in choice versus no-choice situations. Thus, a substrate on which fecundity is higher than on another, when assayed in a no-choice situation, may not be preferred over the other substrate when a choice between the two is provided to the ovipositing females. The latter two results point to possible complexity in the responses of females to various oviposition substrates based upon the overall setting of the assay, including the alternative substrates present for egg laying.     

Habitat utilization, movement and use of groundwater seepages by larval and juvenile Black Redhorse, Moxostoma duquesnei

Black Redhorse (Moxostoma duquesnei) larval and juvenile habitat was characterized in the Grand River, Ontario from June to September 2007–2012. Similar to adult Black Redhorse and their congeners, larval Black Redhorse were most likely to be located in clean, clear, stable runs with low to moderate flow, over pebble, gravel and cobble substrate, mixed with sand. Areas (n?=?22) where 0+ Black Redhorse were observed and collected were 1.4?±?0.2 m from shore, with a mean water temperature of 22.0?±?0.5 °C, mean depth of 0.20?±?0.02 m and mean water velocity of 0.12?±?0.05 m/s. Larval and juvenile Black Redhorse occupied riffles, runs, pools and backwater areas; however, there was a strong preference for runs. Juvenile Black Redhorse moved upstream in the early evening and at night to overwintering areas in the Grand River in November when water temperature approached 5 °C. The persistence of Black Redhorse populations in the Grand River may be related to the presence of groundwater, which provides refuge from extreme temperature and poor water quality during the summer.     

Does ambient substrate composition influence consumer diversity effects on algal removal?

Benthic substrates constitute an important habitat template for aquatic communities and may affect the contributions of benthic organisms to ecological processes. To test the effects of ambient substrate composition on the process of algae accrual and removal, we conducted an experiment to examine how substrate type influenced consumer richness effects. We hypothesized that algal removal from focal substrates (ceramic tiles) would be influenced by the surrounding ambient substrate through its effect on nutrient cycling and subsequent algal growth. We manipulated consumer richness in mesocosms at one or three species while holding consumer biomass constant. Aquatic consumers were an amphipod, a snail, and a water boatman, and ambient substrates were either sand or gravel. After 21 days, ambient substrate influenced epilithic algal accrual on tiles, affected physio-chemical parameters within mesocosms, and modified consumer behavior. Chlorophyll a was approximately 2× greater on control tiles surrounded by sand, and FPOM and turbidity were greater on sand than gravel when consumers were present. Substrate modified consumer behavior such that consumers congregated around focal substrates in sand, but dispersed around them in gravel. Consumers also had substrate-specific influences on epilithic chlorophyll, causing a decrease in sand and an increase in gravel. Algal assemblages on focal tiles were dominated by diatoms, and their composition responded to consumer richness and identity, but not substrate. Our data suggest that direct effects (e.g., consumptive removal of epilithon from focal tiles) were more pronounced in sand, whereas indirect effects (e.g., bioturbation and enhanced mixing) promoted algal accrual in gravel. These results show that algae production on exposed surfaces may change as underlying substrate composition changes, and that substrate type can alter consumer diversity effects on algal removal.     

Population differences in host plant preference and the importance of yeast and plant substrate to volatile composition

Divergent selection between environments can result in changes to the behavior of an organism. In many insects, volatile compounds are a primary means by which host plants are recognized and shifts in plant availability can result in changes to host preference. Both the plant substrate and microorganisms can influence this behavior, and host plant choice can have an impact on the performance of the organism. In Drosophila mojavensis, four geographically isolated populations each use different cacti as feeding and oviposition substrates and identify those cacti by the composition of the volatile odorants emitted. Behavioral tests revealed D. mojavensis populations vary in their degree of preference for their natural host plant. Females from the Mojave population show a marked preference for their host plant, barrel cactus, relative to other cactus choices. When flies were given a choice between cacti that were not their host plant, the preference for barrel and organ pipe cactus relative to agria and prickly pear cactus was overall lower for all populations. Volatile headspace composition is influenced by the cactus substrate, microbial community, and substrate‐by‐microorganism interactions. Differences in viability, developmental time, thorax length, and dry body weight exist among populations and depend on cactus substrate and population‐by‐cactus interactions. However, no clear association between behavioral preference and performance was observed. This study highlights a complex interplay between the insect, host plant, and microbial community and the factors mediating insect host plant preference behavior.     

Temperature coupling of mate attraction signals and female mate preferences in four populations of Enchenopa treehopper (Hemiptera: Membracidae)

Variation in temperature can affect the expression of a variety of important fitness‐related behaviours, including those involved with mate attraction and selection, with consequences for the coordination of mating across variable environments. We examined how temperature influences the expression of male mating signals and female mate preferences—as well as the relationship between how male signals and female mate preferences change across temperatures (signal–preference temperature coupling)—in Enchenopa binotata treehoppers. These small plant‐feeding insects communicate using plantborne vibrations, and our field surveys indicate they experience significant natural variation in temperature during the mating season. We tested for signal–preference temperature coupling in four populations of E. binotata by manipulating temperature in a controlled laboratory environment. We measured the frequency of male signals—the trait for which females show strongest preference—and female peak preference—the signal frequency most preferred by females—across a range of biologically relevant temperatures (18°C–36°C). We found a strong effect of temperature on both male signals and female preferences, which generated signal–preference temperature coupling within each population. Even in a population in which male signals mismatched female preferences, the temperature coupling reinforces predicted directional selection across all temperatures. Additionally, we found similar thermal sensitivity in signals and preferences across populations even though populations varied in the mean frequency of male signals and female peak preference. Together, these results suggest that temperature variation should not affect the action of sexual selection via female choice, but rather should reinforce stabilizing selection in populations with signal–preference matches, and directional selection in those with signal–preference mismatches. Finally, we do not predict that thermal variation will disrupt the coordination of mating in this species by generating signal–preference mismatches at thermal extremes.     

The relative importance of food and shelter for seagrass-associated invertebrates: a latitudinal comparison of habitat choice by isopod grazers

The generality of mechanisms affecting habitat choice and grazing in seagrass meadows was evaluated in a latitudinal comparison of seagrass grazers from the temperate (60°N) Baltic Sea and the subtropical (30°N) Gulf of Mexico. Using similar habitat choice experiment set-ups in Finland and the USA, the role of food type, habitat complexity and predation hazard on habitat choice of the isopods Idotea baltica (Pallas) and Erichsonella attenuata Harger were tested. When shelter was provided by both living and artificial seagrass, epiphytic food resources on artificial vegetation were clearly preferred by both species, although Idotea was attracted to epiphyte-free seagrass when no alternative food was present. When choosing between food and shelter, both species preferred epiphytic food over shelter. However, under predation hazard of fish, Erichsonella clearly switched to the habitat offering shelter, while the presence of a predatory fish produced no preference for shelter by Idotea. Food type may be considered as an universal mechanism that partly determines the presence of grazers in seagrass habitats and is, in the absence of a predator, more important than shelter. Predation risk affected the behaviour of the grazers, but the response varied between species possibly due to varying importance of fish predation in the areas studied. Received: 16 November 1998 / Accepted: 13 February 1999     

Effects of Menstrual Cycle and Room Temperature on Color Preference

This study investigated the effects of menstrual cycle on color preference in nine normally menstruating female subjects. They were instructed to choose their preferred color out of 45 Munsell hues every 5 min at ambient temperatures (T _a) of 28°C (630-800 h), from 28°C to 23°C (800-900 h) and at 23°C (900-930 h). Warmer color hues were preferred during the luteal phase than the follicular phase at 28°C, while there did not exist any significant differences at other T _as. The findings that a preference for warmer colors occurred in the luteal phase at 28°C is discussed in terms of the load error between actual core temperature and its setpoint.     

Effects of attachment substrate,larval diet,and temperature on development and survival of immature Coquillettidia linealis (Skuse) and Coquillettidia xanthogaster (Edwards)

A sustainable colony allowed investigations into attachment substrates, diet and temperature in the development of the immature stages of Cq. linealis and its local congener Cq. xanthogaster. As immatures, these mosquitoes attach to submerged plants for respiration, and various field‐collected and laboratory‐raised plants were compared with non‐living substrates. Hydroponically‐grown wheat plant seedlings provided the most suitable attachment substrate. Development and survival of immatures to eclosion were investigated with three types and three quantities of a standardized diet. Development and survival at rearing temperatures between 10° and 30° C were also investigated. Diet type appeared to have little influence on development. However, at the lowest diet quantity, development to pupation was significantly reduced while the highest diet quantity impacted on the eclosion of pupae. Mean duration of immature development for Cq. linealis increased as temperature decreased. Time from 1^st instar to median eclosion did not differ significantly between 23° C (6.0 weeks) and 25° C (5.3 weeks), although it was 10 weeks at 20° C, and 30° C was lethal. For Cq. xanthogaster, similarly, mean duration of immature development increased as temperature decreased, with development time from 1^st instar to median eclosion significantly longer at 20° C (7.5 weeks) compared to 23° C (5.0 weeks) and 30° C (4.0 weeks).     

Male and female preferences for nest characteristics under paternal care

Nests play a critical role for offspring development across the animal kingdom. Nest quality may contribute to the builder's extended phenotype and serve as an ornament during mate choice. We examined male and female nest choice in the common goby (Pomatoschistus microps), a benthic fish with male‐only parental care where females deposit eggs in male‐built nests. Using prebuilt nest models, we independently manipulated two candidate nest quality traits: (a) nest entrance width with a role in oxygen ventilation, and (b) extent of sand cover with a role in camouflage. In simultaneous choice trials, male gobies exhibited no preference for any nest model type. This suggests that initial characteristics of a nesting substrate have minor importance for males, which usually remodel the nest. Females were given a choice between two males occupying either entrance‐ or cover‐manipulated nests. The same pair of males was then exposed to a second female but now with alternated nest types assigned. Most females were consistent in choosing the same, typically the heavier male of the two regardless of nest properties. However, the females that chose the same nest regardless of the male preferred low over high sand coverage and narrow over wide nest entrance. Our results indicate that females base their mating decision on a combination of male phenotype and nest traits. While we found no indication that females are attracted to highly decorated nests, our study is the first in fishes to disentangle a preference for narrow (and thus more protective) nest entrances independent of nest coverage.     

Post‐hatch dispersal of lake sturgeon (Acipenser fulvescens,Rafinesque, 1817) yolk‐sac larvae in relation to substrate in an artificial stream

Knowledge of the effects of environment and genotype on behavior during early ontogenetic stages of many fish species including lake sturgeon (Acipenser fulvescens) is generally lacking. Understanding these effects is particularly important at a time when human activities are fundamentally altering habitats and seasonal and diel physical and biotic stream features. Artificial stream channels were used in a controlled experiment to quantify lake sturgeon yolk‐sac larvae dispersal distance and stream substrate preference from different females (N = 2) whose eggs were incubated at different temperatures (10 and 18°C) that simulated stream conditions during early and late spawning and incubation periods in the Black River, Michigan. Data revealed that yolk‐sac larvae exhibited considerable variability in dispersal distance as a function of family (genotype), temperature experienced during previous (embryonic) ontogenetic stages, and environmental ‘grain’. Yolk‐sac larvae dispersal distance varied as a function of the juxtaposition of substrate to location of egg hatch. Lake sturgeon yolk‐sac larvae dispersed from mesh screens attached to bricks and settled exclusively in gravel substrate. Dispersal distance also varied as a function of family and egg incubation temperatures, reflecting differences in offspring body size and levels of endogenous yolk reserves (yolk sac area) at hatch. Expression of plasticity in dispersal behavior may be particularly important to individual survival and population levels of recruitment contingent upon the location, size, and degree of fragmentation of suitable (gravel) habitats between adult spawning and yolk‐sac larvae rearing areas.     

Oviposition behavior of the littoral rotifer Euchlanis dilatata

Several components of egg-laying behavior in 3 clones of E. dilatata were investigated. Using nearest-neighbor analyses it was shown that individual animals lay their eggs randomly within culture dishes in the absence of an artificial substrate while eggs laid in the presence of a substrate are clumped in 2 of the 3 clones studied. Animals preferentially oviposited on artificial substrates containing eggs when given a choice between artificial substrates with and without eggs of conspecifics. When given a choice of natural substrates, animals consistently laid more eggs on the plant species from which they were collected. This preference persisted for 2 generations after animals had been removed from plants. In addition, observations of neonate hatching behavior demonstrated that neonates often spend relatively long times in the immediate vicinity of hatching.