Influence of temperature and food concentration on body size,weight and lipid content of two Calanoid copepod species

Two species of Copepoda Temora longicornis (Müller) and Pseudocalanus elongatus (Boeck) were cultured continuously in the laboratory. Four and three generations, respectively, were raised at 16 different combinations of temperature and food concentration. Prosome length and ash-free dry weight were measured in the adult stage and in Pseudocalanus also in copepodite stage I, and the relation between length and weight was established. In Pseudocalanus also the relative amount of lipid was estimated.Prosome length and length-specific body weight (condition factor) were positively correlated with food concentration. Lipid content in Pseudocalanus was also strongly affected by the concentration of food.Prosome length was negatively correlated with temperature. However, length-specific body weight in Temora was positively correlated with temperature. Therefore, at higher temperature Temora was smaller, but heavier per unit body length. In Pseudocalanus a similar but less significant influence of temperature on length-specific weight was found; lipid content was not significantly influenced by the temperature.Females of Temora had larger length-specific weights than males. In Pseudocalanus the opposite was found, coinciding with a higher lipid content in males than in females.It is discussed that at natural concentrations of phytoplankton body size and weight of copepods are reduced in the North Sea during the major part of the growing-season.     

How big were early hominids?

The recent discovery of new postcranial fossils, particularly associated body parts, of several Plio-Pleistocene hominids provides a new opportunity to assess body size in human evolution.¹ Body size plays a central role in the biology of animals because of its relationship to brain size, feeding behavior, habitat preference, social behavior, and much more. Unfortunately, the prediction of body weight from fossils is inherently inaccurate because skeletal size does not reflect body size exactly and because the fossils are from species having body proportions for which there are no analogues among modern species. The approach here is to find the relationship between body size and skeletal size in ape and human specimens of known body weight at death and to apply this knowledge to the hominid fossils, using a variety of statistical methods, knowledge of the associated partial skeletons of the of early hominids, formulae derived from a modern human sample, and, finally, common sense. The following modal weights for males and females emerge: Australopithecus afarensis, 45 and 29 kg; A. africanus, 41 and 30 kg; A. robustus, 40 and 32 kg; A. boisei, 49 and 34 kg; H. habilis, 52 and 32 kg. The best known African early H. erectus were much larger with weights ranging from 55 kg on up. These estimates imply that (1) in the earliest hominid species and the “robust” australopithecines body sizes remained small relative to modern standards, but between 2.0 and 1.7 m.y.a. there was a rapid increase to essentially modern body size with the appearance of Homo erectus; (2) the earliest species had a degree of body size sexual dimorphism well above that seen in modern humans but below that seen in modern gorillas and orangs which implies (along with other evidence) a social organization characterized by kin-related, multi-male groups with females who were not kin-related; (3) relative brain sizes increased through time; (4) there were two divergent trends in relative cheek-tooth size—a steady increase through time from A. afarensis to A. africanus to the “robust” australopithecines, and a decrease beginning with H. habilis to H. erectus to H. sapiens.     

Beliefs About Weight Gain and Attitudes Toward Relapse in a Sample of Women and Men with Obesity

Objective : The purpose of this study was to examine beliefs regarding reasons for weight gain, likely responses to weight loss relapse, notions of reasonable weight loss, and correlations between beliefs and attitudes in a large nonclinical sample of men and women with obesity. Research Methods and Procedures : Participants were 3,394 white women (n= 1,674) and men (n = 1,720) with obesity who had responded to a survey about body image and eating behaviors conducted by Consumer Reports magazine. Results : Women and men indicated that the most important reasons for their weight gain were lack of exercise and enjoying eating; the least important reason was a need to avoid social or sexual situations. Both groups reported that their most likely response to relapse is to start watching food intake, whereas their least likely response is to ask a friend, spouse, or family member for help. Women rated depression, stress, low self-esteem, and need to avoid situations as more important reasons for their weight gain than did men, and women were more likely to feel terrible and regain as a response to relapse. There was no relationship between an individual's beliefs about weight gain, responses to relapse, or notions of reasonable weight loss. Discussion : Implications of these findings for the treatment of obesity are discussed.     

Low dairy intake in early childhood predicts excess body fat gain

Objective: To estimate the effect of dairy intake in early childhood on the acquisition of body fat throughout childhood. Research Methods and Procedures: Ninety‐nine of the original 106 families enrolled in the Framingham Children's Study with a child age to 6 years at baseline were followed into adolescence through yearly clinic visits and periodic data collection throughout each year. Dairy intake for these analyses was derived from a mean of 15 days of diet records per subject collected before age 6. A trained examiner took two measurements each year of height, weight, and triceps, subscapular, suprailiac, and abdominal skinfolds using a standardized protocol. Yearly change in body fat was estimated as the slope of these anthropometry measures from ages 5 to 13 years. Early adolescent body fat was estimated as the mean of all available measurements from 10 to 13 years of age. Results: Children in the lowest sex‐specific tertile of dairy intake during preschool (i.e., <1.25 servings per day for girls and <1.70 servings per day for boys) had significantly greater gains in body fat during childhood. These children with low dairy intakes gained more than 3 additional mm of subcutaneous fat per year in the sum of four skinfold measures. By the time of early adolescence, those in the lowest tertile of dairy intake had a BMI that was approximately two units higher and an extra 25 mm of subcutaneous fat. Discussion: Suboptimal dairy intakes during preschool in this cohort were associated with greater gains in body fat throughout childhood.     

Cephalisation bei Caniden

Cephalisation in Canidae Studied were the intraspecific and interspecific relationships between brain weight and body weight in Canidae. Inclination values of the allometric lines: intraspecific – 0,25, interspecific 0,571. Most of the studied species have nearly the same degree of cephalisation, deviations from the interspecific allometric line are small; the cephalisation of Nyctereutes and Otocyon is less developed than in the other canid species. There is no difference in cephalisation between most canids and felids. Mustelids show a high variability in cephalisation. Criticized were the data of Bauchot (1985) and Gittleman (1986) on brain weight and body weight.     

Clinic-Based vs. Home-Based Interventions for Preventing Weight Gain in Men

Objective : Weight gain occurs frequently in men aged 25–40. This study compared the effectiveness of a clinic-based and a home-based intervention with a no-treatment control group in preventing this weight gain. Research Methods and Procedures : Men (n = 67)—aged 25 to 40, sedentary, with a body mass index of 22 to 30, recruited from the University of Pittsburgh—were randomly assigned to 4-month treatments focused on increasing aerobic exercise and reducing fat intake through a clinic-based (CB) or a home-based (HB) program, or to a de-layed-treatment control group. Subjects were reassessed at 4 months. Results : Adherence and outcome did not differ significantly between the CB and HB programs, except that CB subjects recorded their food intake more frequently, and a greater number of CB subjects achieved a total of 120 miles of exercise over the 4 months. Subjects in the two intervention conditions combined lost significantly more weight (-1.6 ± 2.5 kg) than control subjects, who gained 0.2 ±1.9 kg (p<0.01); this effect of treatment was seen primarily in men with a body mass index of 27 to 30 (-2.7 kg for CB and HB combined vs. +1.5 kg for control). Treated subjects also had somewhat greater improvements in body composition, aerobic fitness, and weekly energy expenditure than controls, although these differences did not reach significance. Discussions: Both CB and HB intervention show promise in preventing weight gain in young men, especially in those who are slightly overweight. Larger studies, using more representative samples of young men, appear warranted.     

QTL for body weight,morphometric traits and stress response in European sea bass Dicentrarchus labrax

Natural mating and mass spawning in the European sea bass (Dicentrarchus labrax L., Moronidae, Teleostei) complicate genetic studies and the implementation of selective breeding schemes. We utilized a two‐step experimental design for detecting QTL in mass‐spawning species: 2122 offspring from natural mating between 57 parents (22 males, 34 females and one missing) phenotyped for body weight, eight morphometric traits and cortisol levels, had been previously assigned to parents based on genotypes of 31 DNA microsatellite markers. Five large full‐sib families (five sires and two dams) were selected from the offspring (570 animals), which were genotyped with 67 additional markers. A new genetic map was compiled, specific to our population, but based on the previously published map. QTL mapping was performed with two methods: half‐sib regression analysis (paternal and maternal) and variance component analysis accounting for all family relationships. Two significant QTL were found for body weight on linkage group 4 and 6, six significant QTL for morphometric traits on linkage groups 1B, 4, 6, 7, 15 and 23 and three suggestive QTL for stress response on linkage groups 3, 14 and 23. The QTL explained between 8% and 38% of phenotypic variance. The results are the first step towards identifying genes involved in economically important traits like body weight and stress response in European sea bass.     

Behavioral Strategies of Individuals Who Have Maintained Long-Term Weight Losses

MCGUIRE, MAUREEN T., RENA R. WING, MARY L. KLEM, AND JAMES O. HILL. Behavioral strategies of individuals who have maintained long-term weight losses. Obes Res. Objective: The purpose of the present study was to compare the behaviors of individuals who have achieved long-term weight loss maintenance with those of regainers and weight-stable controls. Research Methods and Procedures: Subjects for the present study were participants in a random-digit dial telephone survey that used a representative sample of the U. S. adult population. Eating, exercise, self-weighing, and dietary restraint characteristics were compared among weight-loss maintainers: individuals who had intentionally lost ≥10% of their weight and maintained it for ≥1 year (n = 69), weight-loss regainers: individuals who intentionally lost ≥10% of their weight but had not maintained it (n = 56), and weight-stable controls: individuals who had never lost ≥10% of their maximum weight and had maintained their current weight (±10 pounds) within the past 5 years (n= 113). Results: Weight-loss maintainers had lost an average of 37 pounds and maintained it for over 7 years. These individuals reported that they currently used more behavioral strategies to control dietary fat intake, have higher levels of physical activity (especially strenuous activity), and greater frequency of self-weighing than either the weight-loss regainers or weight-stable controls. Maintainers and regainers did not differ in reported levels of dietary restraint, but both had higher levels of restraint than the weight-stable controls. Discussion: These results suggest that weight-loss maintainers use more behavioral strategies to control their weight than either regainers or weight-stable controls. It would thus appear that long-term weight maintenance requires ongoing adherence to a low-fat diet and an exercise regimen in addition to continued attention to body weight.     

Lean and Weight Stable: Behavioral Predictors and Psychological Correlates

Objective: To examine behavioral characteristics associated with being lean and weight stable during adulthood. Research Methods and Procedures: Participants included 165 white married couples who were part of a larger longitudinal study. Participants’ height and weight were measured on three occasions at 2‐year intervals. Men and women were classified as being lean and weight stable (the target group) if they had a BMI < 25 at baseline and maintained their weight within 5% of baseline at 2nd and 4th year follow‐up. Individuals not fulfilling these criteria were included in the comparison group. Group differences in background characteristics including childhood weight status, BMI at each occasion, dieting history, and mental and physical health history were examined. In addition, multiple measures of dietary intake and physical activity were obtained and used to predict the likelihood of being in the target group. Results: Men (N = 22) and women (N = 36) in the target group had lower mean BMI scores at each occasion, were less overweight during childhood, were less likely to have dieted in the past year, and rated themselves as being more healthy than men and women in the comparison group. No differences were identified in mental health. Relative to the comparison group, women in the target group reported higher levels of physical activity and higher levels of physical activity among their spouses, and men in the target group reported healthier dietary patterns. Discussion: Results from this study suggest that being lean and weight stable in adulthood is linked to childhood weight status in combination with dietary and activity patterns during adulthood.     

Weight Goals in a College‐age Population

Objective: Although a growing body of literature has found unrealistic weight loss goals to be common among older, primarily female, subjects, little is known about weight loss goals of younger adults. Research Methods and Procedures: Three hundred seventy‐nine college students had their height and weight taken and reported their “goal,” “dream,” “happy,” “acceptable,” and “disappointed” weights. A series of 2 (gender) × 2 (nonoverweight vs. overweight) ANOVAs were conducted with both absolute weight goals and percentage of weight loss needed to obtain those goals as dependent variables. Results: When examined in terms of absolute weight goals, women generally had lower body mass index (BMI) goals than men, and nonoverweight participants had lower BMI goals than overweight participants. Surprisingly, most overweight participants would accept a weight loss that would still place them in the overweight BMI range. When examined in terms of percentage loss needed to reach those goals, only overweight women chose goal and dream weights that would require a loss greater than can be expected from nonsurgical weight‐loss treatments, and all overweight participants chose happy and acceptable weights within 15% of current weight. Discussion: Participants in this study had generally reasonable weight‐loss goals, and even the most extreme weight loss goals were much more moderate than those found in previous studies. These results are surprising given the extreme social pressures for thinness facing young adults. Future studies should examine the variables that influence selection of goal weights and how goal weights affect actual dieting behavior.     

Spectral characteristics of intense mew calls in cat species of the genus <Emphasis Type="Italic">Felis</Emphasis> (Mammalia: Carnivora: Felidae)

Spectral characteristics of intense mew calls of six cat (sub)species in the genus Felis were studied in captivity: European wildcat (Felis s. silvestris), African wildcat (F. s. lybica), Asiatic steppe cat (F. s. ornata), black-footed cat (F. nigripes), jungle cat (F. chaus), and sand cat (F. margarita). The body weight of the largest (jungle cat) of the six taxa is about six times that of the smallest (black-footed cat), and they live in different habitat types ranging from open desert virtually devoid of vegetation (sand cat) to various types of rather dense forest and shrubland (European wildcat). These habitats differ considerably in the conditions for sound propagation. In this study we analyzed whether and how spectral characteristics of the intense mew calls of these cat taxa are related to their body weight/size and predominant habitat type (open vs. dense). Neither the mean fundamental frequency nor the mean dominant frequency of the intense calls of these cat (sub)species showed an inverse correlation with their respective body weights (“frequency scaling rule”). Rather, the mean dominant frequency is significantly positively correlated with body weight, being lower in the calls of the smaller taxa living in open habitat compared to those of the larger taxa living in dense habitat types. The hypothesis supported best by our data is that spectral features of intense mew calls in the Felis taxa studied have evolved to reduce attenuation when propagating through their respective habitat types. B. Tonkin-Leyhausen is retired and has no institutional affiliation any longer.     

A family-based approach to preventing excessive weight gain

Objective: Preventing weight gain in adults and excessive weight gain in children is a high priority. We evaluated the ability of a family‐based program aimed at increasing steps and cereal consumption (for breakfast and snacks) to reduce weight gain in children and adults. Research Methods and Procedures: Families (n = 105) with at least one 8‐ to 12‐year‐old child who was at‐risk‐for‐overweight or overweight (designated as the target child) were recruited for the study. Eighty‐two families were randomly assigned to receive the family‐based intervention and 23 families to the control condition. The 13‐week intervention consisted of specific increases in daily steps (an additional 2000 steps/d) and consumption of 2 servings/d of ready‐to‐eat cereal. Results: The intervention was successful in increasing walking (steps) and cereal consumption. The intervention had positive, significant effects on percentage BMI‐for‐age and percentage body fat for target children and weight, BMI, and percentage body fat for parents. On further analysis, the positive effects of the intervention were seen largely in target girls and moms, rather than in target boys and dads. Discussion: This family‐based weight gain prevention program based on small changes holds promise for reducing excessive weight gain in families and especially in growing overweight children.     

Impact of Weight‐Cycling History on Bone Density in Obese Women

Objective: The purpose of this study was to examine the effect of weight cycling (as defined by the frequency and magnitude of intentional weight loss) on bone mineral density and bone mineral content in obese sedentary women. Research Methods and Procedures: Bone mineral content and density measured by DXA, submaximal physical fitness assessment, nutrient intake, oral contraceptive use, and weight‐cycling history were assessed in 195 healthy, overweight sedentary women (age, 21 to 45 years; body mass index, 27 to 40 kg/m²) before beginning a behavioral weight‐loss intervention. Results: After controlling for body weight, multivitamin use, oral contraceptive/estrogen use, and calcium and magnesium intake, women who had a history of weight cycling did not have significantly lower total‐body bone mineral content or density or total femur bone mineral density. In addition, 99% of subjects were above or within one SD of age and gender normative data for total femur bone mineral density. Discussion: It does not seem that a history of weight cycling has an adverse affect on total femur and total‐body bone mineral density in overweight sedentary premenopausal women.     

The relationship between body weight and natural mortality in juvenile and adult fish: a comparison of natural ecosystems and aquaculture

The relationship between body weight and natural mortality in juvenile and adult fish was analysed for different aquatic ecosystems: lakes, rivers, the ocean, and pond, cage and tank aquaculture systems. Mortality was modelled as a power function of weight, and the parameters b (exponent) and M_u (mortality at the unit weight of 1 g) estimated for fish in the six ecosystems, as well as within selected populations, species and families. At the ecosystem level, no significant differences in parameters were found between lakes, rivers and the ocean and a joint mortality-weight relationship for all natural ecosystems was estimated with parameters b=?0.288 (90% CL[?0.315, ?0.261]) and M_u=3.00 (90% CL[2.70, 3.30]) year^?1. Among the culture systems, mortality-weight relationships in ponds and cages were not significantly different and a joint relationship was estimated. The weight exponents of mortality in ponds/cages and tanks were very similar at about b=?0.43, and significantly more negative than in natural ecosystems. Mortalities at unit weight were significantly lower in tanks (0.91 year^?1) than in ponds/cages (2.24 year^?1), and both were significantly lower than in natural ecosystems. No systematic differences were found between the mortality-weight relationships determined for individual populations, species or families, and fish in the respective ecosystems. It is hypothesized that aquaculture mortality-weight relationships indicate the allometric scaling of non-predation mortality, which is therefore more strongly size dependent than predation mortality. If non predation mortality in natural ecosystems shows a similar scaling with body weight, then the allometric exponent of predation mortality must be less negative than that observed for total natural mortality. Implications of the established mortality-weight relationships for aquaculture and culture-based fisheries are discussed.     

Neonatal weight in gibbons (Hylobates spp.)

Neonatal and birth weights of gibbons have mostly been reported for single individuals, and larger samples (n = 2–8) have apparently been published for only two species of gibbons (Hylobates lar and H. syndactylus). In addition, a critical examination of the few published neonatal weights of gibbons shows that several of them should not be used. Neonatal weights are here defined as weights taken on infants up to seven days old, whereas birth weights include only those taken on the day of birth. This paper presents neonatal weights for six representative species of gibbons (H. lar, H. leucogenys, H. moloch, H. muelleri, H. pileatus, H. syndactylus) and some of their hybrids. Most of our data stem from surviving animals that were subsequently hand-reared and include 80 infants, thus making the previously available dataset 5 times larger. Our neonatal weights fall roughly into three different classes: neonates of the lar group (about 390 g, n = 27), the concolor group (about 510 g, n = 7), and the siamang (about 540 g, n = 46). This grouping corresponds not only to taxonomic units within the hylobatids, but also to grouping of gibbons by adult body weight. No weight difference between males and females is evident in our sample, and hybrids of the lar group do not appear to differ in weight from pure species. True birth weights (i.e., weights recorded on the day of birth) are available for only a few individuals. These weights are, on average, 7% higher than neonatal weights, but the difference is not statistically significant. Additional samples of neonatal weights suggest that infants that die on the day of birth weigh, on average, 17% less, twins weigh 29% less, and infants born by Cesarean section weigh 19% more than our reference sample of neonates. © 1995 Wiley-Liss, Inc.     

Intentional Weight Loss Reduces Mortality Rate in a Rodent Model of Dietary Obesity

Objective: We used a rodent model of dietary obesity to evaluate effects of caloric restriction‐induced weight loss on mortality rate. Research Measures and Procedures: In a randomized parallel‐groups design, 312 outbred Sprague‐Dawley rats (one‐half males) were assigned at age 10 weeks to one of three diets: low fat (LF; 18.7% calories as fat) with caloric intake adjusted to maintain body weight 10% below that for ad libitum (AL)‐fed rat food, high fat (HF; 45% calories as fat) fed at the same level, or HF fed AL. At age 46 weeks, the lightest one‐third of the AL group was discarded to ensure a more obese group; the remaining animals were randomly assigned to one of three diets: HF‐AL, HF with energy restricted to produce body weights of animals restricted on the HF diet throughout life, or LF with energy restricted to produce the body weights of animals restricted on the LF diet throughout life. Life span, body weight, and leptin levels were measured. Results: Animals restricted throughout life lived the longest (p < 0.001). Life span was not different among animals that had been obese and then lost weight and animals that had been nonobese throughout life (p = 0.18). Animals that were obese and lost weight lived substantially longer than animals that remained obese throughout life (p = 0.002). Diet composition had no effect on life span (p = 0.52). Discussion: Weight loss after the onset of obesity during adulthood leads to a substantial increase in longevity in rats.     

Early hominid body weight and encephalization

The body weight of the Plio-Pleistocene hominids of Africa is estimated by predicting equations derived from the Terry Collection of human skeletons with known body weights. About 50% of the variance in body weight can be accounted for by vertebral and femoral size. Predicted early hominid weights range from 27.6 kg (61 lb) to 54.3 kg (119 lb). The average weight for Australopithecus is 43.2 kg (95 lb) and for Homo sp. indet. from East Rudolf, Kenya, is 52.8 kg (116 lb). These estimates are consistent even if pongid proportions are assumed. Indices of encephalization show that the brain to body weight ratio in Australopithecus is above the great ape averages but well below Homo sapiens. The Homo sp. indet. represented by the KNM-ER 1470, O.H. 7 and O.H. 13 crania have encephalization indices above Australopithecus despite the greater body weight of the former.     

A primary care weight management intervention for low-income African-American women

Objective: To determine whether a tailored weight management program, addressing the needs of obese, low‐income African‐American women, would produce greater weight loss than standard medical care. Research Methods and Procedures: A randomized, controlled trial was conducted between 1999 and 2003 with 144 overweight or obese women (predominantly African‐American) enrolled at two primary care clinics. Four physicians at each clinic were randomly assigned to provide either tailored weight management interventions or standard care. The tailored condition consisted of six monthly outpatient visits lasting ～15 minutes each, which included personalized materials and messages. The main outcome was body weight change. Results: The intervention group lost more weight than the standard care group (p = 0.03). The tailored group lost a mean (standard deviation) of 2.0 (3.2) kg by Month 6. The standard care group gained 0.2 (2.9) kg. More participants in the tailored group lost weight (79% vs. 47%; p = 0.04). Discussion: Obese, low‐income, African‐American women provided with 90 minutes of physician‐delivered, tailored weight management instruction over 6 months achieved greater weight loss than those receiving standard medical care. The primary care physician can be effective in delivering weight loss interventions, and the primary care clinic may be a useful setting to implement weight management interventions.     

Dominant frequency of loud mew calls of felids (Mammalia: Carnivora) decreases during ontogenetic growth

• 1 A negative correlation between body weight and frequency characteristics of a species' vocalizations exists in mammals, due to the acoustics of vocal sound production (‘source‐filter theory’; source = larynx; filter = supralaryngeal vocal tract) and the strong positive correlation between body weight and vocal tract length.
• 2 A negative correlation is hypothesized to exist between increasing body weight and frequency characteristics of calls during ontogeny as well.
• 3 This hypothesis is tested for mean dominant frequency (maximum spectral energy peak) of intense mew calls in juveniles of five species of the Felidae: lion Panthera leo, jaguar Panthera onca, leopard Panthera pardus, tiger Panthera tigris and puma Puma concolor.
• 4 In the five felid species in which the hyoid is incompletely ossified (genera Panthera and Uncia), the larynx undergoes a considerable ontogenetic descent, resulting in a proportionally longer vocal tract in adult individuals than in all other species of the family, which have a fully ossified hyoid without a descent.
• 5 In all five species studied here, mean dominant frequency decreases as body weight increases during growth. In the four Panthera species (with laryngeal descent) dominant frequency is determined by the vocal tract (the filter), and dominant frequency is largely similar at similar weights, indicating a similar correlation between the ontogenetic increase in body weight (and vocal tract length) and the decrease in mean dominant frequency. In the puma (without laryngeal descent) dominant frequency is determined by the larynx (the source), it is considerably higher than in the Panthera species, and the course of its ontogenetic decrease differs considerably from that in Panthera.
• 6 The data do not support a uniform scaling relationship between body weight and mean dominant frequency of intense mew calls in the Felidae during ontogenetic growth.

     

POLYGYNANDRY IN THE DUSKY PIPEFISH SYNGNATHUS FLORIDAE REVEALED BY MICROSATELLITE DNA MARKERS

In the dusky pipefish Syngnathus floridae, like other species in the family Syngnathidae, ‘pregnant’ males provide all post-zygotic care. Male pregnancy has interesting implications for sexual selection theory and the evolution of mating systems. Here, we employ microsatellite markers to describe the genetic mating system of S. floridae, compare the outcome with a previous report of genetic polyandry for the Gulf pipefish S. scovelli, and consider possible associations between the mating system and degree of sexual dimorphism in these species. Twenty-two pregnant male dusky pipefish from one locale in the northern Gulf of Mexico were analyzed genetically, together with subsamples of 42 embryos from each male's brood pouch. Adult females also were assayed. The genotypes observed in these samples document that cuckoldry by males did not occur; males often receive eggs from multiple females during the course of a pregnancy (six males had one mate each, 13 had two mates, and three had three mates); embryos from different females are segregated spatially within a male's brood pouch; and a female's clutch of eggs often is divided among more than one male. Thus, the genetic mating system of the dusky pipefish is best described as polygynandrous. The genetic results for S. floridae and S. scovelli are consistent with a simple model of sexual selection which predicts that for sex role-reversed organisms, species with greater degrees of sexual dimorphism are more highly polyandrous.