Scott P. McRobert

The influence of body coloration on shoaling preferences in fish

Shoaling behaviour provides antipredator benefits that rely, to some extent, on a high degree of phenotypic homogeneity between individuals within the shoal. Therefore, fish should have the ability to discriminate between potential shoalmates, choosing to associate with individuals of similar appearance to themselves. We studied the effects of a single phenotypic character, body coloration, on association choices made by black and white mollies (Poecilia latipinna). When given a choice between a group of mollies of similar coloration and an empty compartment, individual test fish (black or white) spent significantly more time near the fish group. When given a choice between a group of black mollies and a group of white mollies, individual fish (black or white) spent significantly more time near the group of mollies of similar coloration to their own. When given a choice between a group of mollies of dissimilar coloration and an empty compartment, black and white mollies reacted differently. Black mollies spent significantly more time on the side of the central compartment closest to the white mollies, while there was no significant difference between the time spent by white mollies on either side of the test tank. Our results indicate that fish can use visual cues to discriminate actively between potential shoalmates on the basis of body coloration. Copyright 1998 The Association for the Study of Animal Behaviour.

Courtship of young males is ubiquitous in Drosophila melanogaster

In eightDrosophila melanogaster stocks, males which are only a few hours old stimulate courtship which is qualitatively and, in many of the stocks, quantitatively indistinguishable from the courtship elicited by virgin females. Although the sex appeal of young males and the extent to which it declines as the males become sexually mature vary somewhat from stock to stock, homosexual courtship appears to be characteristic of the species.

Road occurrence and mortality of the northern diamondback terrapin

We examined road occurrence and mortality of the northern diamondback terrapin, Malaclemys terrapin terrapin, in the Jacques Cousteau National Estuarine Research Reserve during the 2004 nesting season (May-July). Traffic volume estimates were obtained using measuring devices stationed on sections of Great Bay Boulevard, an access road through a salt marsh habitat in Tuckerton, New Jersey. Six hundred adult female terrapin occurrences were recorded, 53 of those being road mortalities (8.83%). A significantly greater proportion of road kills was found in the section of the road with the highest traffic volume. There was also a positive correlation between road kills and increasing traffic volume throughout the day. Approximately half of the road mortalities were discovered in the first survey hour, suggesting that some nesting terrapins were being killed during the night or in the early morning hours. The information gathered suggests that terrapins are attracted to the roadside as it meets the requirements for a suitable nesting habitat.

Social partner preferences of male and female fighting fish (Betta splendens)

While the social interactions of Betta splendens have been studied in the contexts of dominance hierarchies, mate choice and communication networks, the social partner preferences of Betta have been largely overlooked. In this study, we presented male and female Betta with a single male, a single female, and a group of three females in dichotomous choice tests in order to better understand basic social interactions in this largely nonsocial species. The highly territorial Betta preferred associating with conspecifics in nearly every configuration we tested, with exceptions noted when single females were given the choice between a lone male and an empty chamber, and when males were presented with a single female and an empty chamber. Also, in most tests, the fish chose to spend more time with the larger group of females. The motivation for this preference certainly varied from reproductive to anti-predator. While such behavior might not suggest true shoaling behavior, it does demonstrate a subtle degree of sociality.

Shoaling in Juvenile Guppies: The Effects of Body Size and Shoal Size

While factors affecting shoal mate choice have been examined extensively in adult guppies (Poecilia reticulata), few studies have focused on the shoaling behavior of juveniles. In this study, juvenile guppies were tested for their ability to shoal as well as their response to shoal mates of different body size and to shoals with different numbers of individuals. In dichotomous choice tests, 10-day-old guppies (mean body length=8.83 mm), 30-day-old guppies (13.17 mm) and 50-day-old guppies (18.6mm) were given the opportunity to swim near shoals of five fish or an empty chamber. In most cases, the juvenile fish demonstrated shoaling behavior, swimming near a group of fish rather than an empty chamber, regardless of the age of the stimulus shoal. When presented with two shoals, one of similar age and body size and one of dissimilar age and body size, only the 50-day-old guppies showed a significant preference for the age-matched shoal. Similarly, when choosing between a large shoal and a small shoal, only the 50-day-old guppies spent significantly more time near the larger shoal. Thus, while juveniles at each age shoaled, only 50-day-old fish demonstrated the shoal mate discrimination seen in adult fish.

Identification of acoustic stimuli that mediate sexual behavior inDrosophila busckii (Diptera: Drosophilidae)

We have shown that D. busckiimales and females, unlike other drosophilids that have been analyzed in this regard, court and copulate as well in relatively dim red light as they do in bright white light. We have also shown that males and females of this species flutter their wings during courtship and that wing fluttering in both sexes is associated with acoustic stimuli. Wingless males perform vigorous courtship but are incapable of mating, suggesting that females must perceive male song to be receptive to copulation. When they are tested with normal males, wingless females stimulate vigorous courtship, but their copulation frequencies are significantly lower than winged females. This observation suggests that perception of the females song by either or both sexes facilitates mating.

The effect of body coloration and group size on social partner preferences in female fighting fish (Betta splendens).

Females of the fighting fish Betta splendens have been shown to associate with other B. splendens females in a manner reminiscent of shoaling behavior. Since body coloration varies dramatically in this species, and since body coloration has been shown to affect shoalmate choice in other species of fish, we examined the influence of body coloration on association preferences in female B. splendens. In dichotomous choice tests, B. splendens females spent more time swimming near groups of females (regardless of coloration) than swimming near an empty chamber, and chose to swim near fish of similar coloration to their own when choosing between two distinctly colored groups of females. When examining the interplay between body coloration and group size, focal fish spent more time swimming near larger groups (N=5) of similarly colored fish than swimming near an individual female of similar coloration. However, focal fish showed no preference when presented with an individual female of similar coloration and a larger group of females of dissimilar coloration. These results suggest that association choices in B. splendens females are strongly affected by both body coloration and by group size.

Shoaling preferences and the effects of sex ratio on spawning and aggression in small laboratory populations of zebrafish (Danio rerio).

Owing to a lack of basic information on the biology of zebrafish (Danio rerio), lab managers must often base decisions regarding the care and use of this species on anecdotal information. In an effort to provide researchers with context-specific behavioral information, the authors evaluated shoaling and spawning behaviors in small groups of zebrafish. In each shoaling assay, a fish was given a choice to shoal with either a single fish or a group of three fish. Females preferred to shoal with a group of three individuals rather than with a single individual, regardless of the sex of the other fish. Males preferred groups of three males over single males but preferred single females to groups of three females. In spawning assays, zebrafish were placed in breeding tanks in one of three sex ratios (1 male:1 female; 3 males:1 female; 1 male:3 females). Reproductive efficiency did not differ among groups, but aggression (evaluated according to presence of shed scales) was more frequently observed in the male-dominated treatment group.

Northern Diamondback Terrapin Occurrence, Movement, and Nesting Activity Along a Salt Marsh Access Road

ABSTRACT Northern diamondback terrapins, Malaclemys terrapin terrapin, were tagged with passive integrated transponder tags to mark them and monitor their activity along a road through salt marsh habitat in Tuckerton, New Jersey. A mark-recapture study was conducted to evaluate terrapin movements, nesting frequency, and nest site fidelity. During sampling periods throughout 2 nesting seasons (2004–2005), 300 adult females were tagged. Ninety-two recaptures were made of 54 individual terrapins, with most recaptures (81.5%) occurring within a season (range = 1–45 days, mean = 7.5 days). Some recaptures (18.5%) occurred the following year. Some females crossed the road multiple times during nesting, and nearly half searched for a site within 50 m of the area where they were initially tagged. Nest site selections of all multiple nesters (within and among seasons) varied greatly from approximately 4–1307 m (mean internesting distance = 202.75 m), yet 39% were recaptured within 50 m of their initial tagging location. One-third of yearly nesters showed an internesting distance within 25 m of their initial-year tagging location. These results indicate that some females travel variable distances between nest sites and may demonstrate evidence of nest site fidelity.

Behavioral and pheromonal phenotypes associated with expression of loss-of-function mutations in the sex-lethal gene of Drosophila melanogaster.

We have shown that female-specific functions of the sex determination gene Sex-lethal (Sxl) regulate sexual behavior and synthesis of the three major sex pheromones that have been identified in normal, sexually mature Drosophilia melanogaster males and virgin females. Diplo-X flies, heterozygous in trans for two partial loss-of-function Sxl mutations, elicit less courtship than normal females and produce large quantities of the inhibitory pheromones that normal males synthesize. In addition, the mutant flies fail to synthesize the female-predominant aphrodisiac pheromone or make very small quantities of this compound.