Large Males Research Articles

Spatial ecology of invasive Bennett’s wallaby in South Island, New Zealand

Context Bennett’s wallaby (Notamacropus rufogriseus) was introduced into New Zealand in the late-1800s, and has subsequently become a significant pest to agriculture, silviculture, and native vegetation. Effective management of wallabies requires robust spatial and temporal ecological information, which can be used operationally to increase detection and kill rates. Aims To determine home range size and shape, resource (i.e. habitat and topography) selection, and daily movement patterns of three populations of Bennett’s wallaby in the South Island. Methods We attached GPS-collars to 38 adult wallabies (17 females, 21 males) between May 2018 and May 2019, and obtained usable location data from 30 individuals. We used kernel density estimators and resource selection functions to quantify seasonal home ranges and resource selection, respectively. Key results The mean seasonal home range sizes of males and females were similar (26.8 ha and 24.8 ha, respectively; combined range = 1.2–101.9 ha), although the largest home ranges belonged to large males. Resource selection was strongly influenced by distance to concealment cover, ridgelines and streams, i.e. wallabies selected to be closer to these features, though not necessarily at them. Wallabies selected areas close to concealment cover throughout 24-h periods, but most strongly during the day, which is when they bed in dense cover. Wallabies sampled outside of peak breeding moved most during dusk and dawn (median = ~50 m/h), whereas those sampled during peak breeding moved widely during day, dusk, and night (110–280 m/h), but not dawn (median = ~50 m/h). Conclusions The home range sizes of wallabies in New Zealand were highly variable, but on average were similar for males and females. Wallabies selected pasture close to areas with some cover, suggesting a trade-off between access to high-quality forage and concealment cover. Implications Our results provide robust data for modelling management strategies for wallabies, and contribute directly to operational planning by identifying habitats where wallabies are most likely to be found temporally. This information can be used to determine the appropriate survey methods and control tools to maximise detection rates and kill rates of wallabies, based on habitat.

Mate choice for body size leads to size assortative mating in the Ryukyu Scops Owl Otus elegans.

Understanding evolutionary phenomena that involve size assortative mating requires elucidating the generating mechanisms on which assortment is based. Although various mechanisms have been suggested, their relative importance may differ across taxonomic groups. Males selecting for large, fecund females combined with the dominance of large males in the competition for females has been suggested as a major mechanism in specific groups. However, raptors do not appear to conform to this, because the selection for smallness among males (assumed in a theory of reversed sexual size dimorphism) and the selection for largeness among males (assumed in the theory of size assortative mating) are in opposite directions. We studied the assortative mating during a long-term study of the Ryukyu Scops Owls Otus elegans interpositus. Significant assortative mating was found for culmen length (from the base to the tip of the bill) and wing length (from the bend of the wing to the tip of the longest primary). Statistical control of the spatial and temporal accessibility of potential mates did not affect the assortment. Males with short wings had slightly higher fitness components than those with long wings, and females settling early tended to have small wings. Considering that early-settling females can preferentially choose their mates, these results suggest that smaller females have an advantage when choosing smaller males with good reproductive performance. Improved flying and hunting ability of smaller individuals may be the background of choosing smaller individuals. We propose that, not passive process like similarity between individuals and their potential mates, but active mate choice for small individuals is an explanation for the assortative mating in this owl.

Male plumage signal expression is related to feather corticosterone concentration in the Pied Flycatcher Ficedula hypoleuca

Male signals may express the capacity to sustain environmental challenges. In some migratory birds like the Pied Flycatcher Ficedula hypoleuca, plumage ornaments are molted in the winter quarters shortly before spring migration while most feathers are replaced shortly after the breeding season in the breeding areas. The concentration of corticosterone in feathers (CORTf) may relate to baseline CORT levels at the time of molt which could be expressed through plumage signals. Male Pied Flycatchers present white patches on forehead feathers and tertials which are molted before spring migration and on secondaries and primaries replaced after breeding. They also express a variable degree of melanisation of head and back feathers molted in the wintering areas. All these plumage traits have been previously shown to function in social contests and/or mate attraction. Here we have collected tertials on the two wings and two tail feathers, molted in wintering and breeding areas respectively, of males in a Spanish montane population and analysed CORTf in the laboratory with standard enzyme immunoassays. There is no correlation within individuals between CORTf in the two types of feathers, although levels are similar. The size of the forehead patch is negatively associated with CORTf in tail feathers, mainly in small males, while the blackness of head and back is negatively related to CORTf in tertials, mainly in large males. The size of the wing patch composed of patches on feathers molted both in wintering (tertials) and breeding areas (primaries and secondaries) is not related to CORTf in any type of feather. Different male plumage traits thus may reflect circulating CORT levels during molt processes occurring in the wintering respectively breeding range as expressed by CORTf in different types of feathers.

A Life History Study of Atlantic Wolffish Resolves Bias and Imprecision in Length‐ and Age‐at‐Maturity Schedules by Recognizing Abortive Maturation

AbstractStock assessments of U.S. Atlantic Wolffish Anarhichas lupus are hampered by a landings moratorium and low catches in fishery‐independent surveys. Working with the commercial fishing industry, we collected hundreds of fish to overcome a lack of regionally specific life history information. Based on ages from sectioned otoliths, Atlantic Wolffish are long lived (maximum observed age: males = 31 years, females = 29 years). A Gompertz growth model showed that Atlantic Wolffish exhibit dimorphic growth—with larger males across all ages on average. Preliminary estimates of total mortality ranged from 0.15 to 0.21 and were lower than an estimate measured at the beginning of the moratorium. Based on gonad histology, a cohort of vitellogenic oocytes emerged in mature females by April and developed group synchronously to ovulate primarily in October. Skip spawning, which accounts for nonannual spawning, was observed in 5.6% of the mature females. Accounting for abortive maturation, a physiological event that delays functional maturation, improved precision and reduced bias of maturity estimates. The resulting median length at functional maturity was 53 cm total length (95% confidence interval = 49–56 cm), and the median age was 6.7 years old (6.2–7.2 years). These estimates are smaller and younger than elsewhere in the western North Atlantic Ocean, confirming that regionally specific maturity parameters are relevant when assessing reference points of the U.S. Atlantic Wolffish fishery.

A new stag beetle species of the genus Gnaphaloryx Burmeister from Java, western Indonesia (Coleoptera: Lucanidae)

ABSTRACT Tropical Indonesia has a rich biota. The fauna of stag beetles (Lucanidae) is relatively well understood in Indonesia, with numerous endemic species, including on the island of Java. Gnaphaloryx (Lucaninae: Dorcini) is a small genus of stag beetles mainly distributed in the Oriental Region. A new lucanid species, Gnaphaloryx rectus Yamamoto sp. nov., is described from West Java, western Indonesia. This new species can be easily distinguished from the known Gnaphaloryx in the large males as it possesses symmetrical and rather linear mandibles, very weakly developed cephalic horn, weakly produced canthi, and narrower 2nd and 3rd costae on the elytra in comparison with the 1st one. We provide a checklist of all species and subspecies of the genus with their known distributions. http://www.zoobank.org/urn:lsid:zoobank.org:pub:738C1CA7-8D54-46C4-90D6-97087356528F http://www.zoobank.org/urn:lsid:zoobank.org:act:211DA3A1-A08C-4291-BDC7-BAB3F69034C5

Spatiotemporal patterns of male and female white-tailed deer on a hunted landscape.

Resource selection in sexually dimorphic ungulates is at least partially explained by sex‐specific resource requirements and risk aversion strategies. Females generally spend more time in areas with less risk and abundant, high‐quality forage due to their smaller body size. However, demographically variable responses to risk are context dependent, and few have concurrently quantified male and female behavior within areas with the same resource base. We captured 111 (54 males, 57 females) adult white‐tailed deer (Odocoileus virginianus) from 2009 to 2018 on a site in South Carolina, USA, where hunters were the primary source of adult mortality. We fit each deer with a GPS collar programmed to collect locations at 30‐min intervals. Upon collar recovery, we analyzed the data to estimate sex‐ and time‐specific selection for, and distance to, various cover types. While both sexes generally avoided risky areas (i.e., sites hunted more frequently) during the day, females (p = .41) were more likely than males (p = .16) to use risky areas containing abundant food resources during the day, where p = probability of selection. Our findings indicate that female white‐tailed deer may be forced to utilize high risk areas during high risk periods due to their smaller body size and increased nutritional demands, whereas larger males are better able to forgo foraging opportunities during risky periods to mitigate risk; however, our study design left room for the possibility that our observations were driven by innate sex‐specific patterns in white‐tailed deer. Nonetheless, our study contributes information to the literature by describing sex‐specific resource selection by diel period on a site where sexes shared the same resources and were presented with the same landscape of risk.

A-301 Differences in Regional Cerebral Blood Flow for Females and Males with Elevated Self-Reported PTSD Symptoms

Abstract Objective: Females and males may differ in stress responses which suggests different brain reactivity between genders in PTSD. This study compares baseline regional cerebral blood flow (rCBF) between females and males with elevated PTSD symptoms. Method: Females [n = 383; Mage=37.51; white (65%)] and males [n=389; Mage=36.37; white (65%)] with elevated self-reported PTSD symptoms (2SD over the mean) were selected from a deidentified adult clinical outpatient database. No significant differences existed between genders for race or age. ANOVAs were utilized to test the difference between females and males’ baseline rCBF levels. Those with comorbid diagnosis were included. Alpha was set at .001. Results: Females had significantly lower bilateral perfusion in the frontal [left: F(1,770)=17.173; right: F(1,770)=49.496], occipital [left: F(1,770)=88.897; right: F(1,770)=144.190], temporal [left: F(1,770)=11.594; right: F(1,770)=58.005], cerebellum [left: F(1,770)=121.549 right: F(1,770)=138.506] and right parietal lobe [F(1,770)=42.303]. Males had significantly lower bilateral perfusion in limbic system [left: F(1,770)=228.628; right: F(1,770)=211.896], basal ganglia [left: F(1,770)=234.383; right: F(1,770)=138.506], left motor sensory [F(1,770)=31.459], and vermis region of the brain [F(1,770)=51.637]. No differences were found in right motor sensory or left parietal regions. Conclusion: Given the large effects males exhibited in the limbic and basal ganglion regions, males may struggle with emotional regulation, memory, and motor control due to dysfunction in these regions. Females may struggle with dizziness, aspects of executive functioning, processing language and emotions, and difficulty processing visual information due to depravation in the frontal, temporal, occipital and cerebellum regions. Limitations included lack of specificity to trauma and the utilization of a self-report measure to define PTSD symptoms.

Ontogenetic Expressions of Sexually Dimorphic Traits in the Skeleton Shrimp Caprella scaura (Crustacea: Amphipoda).

In sexual dimorphism, males often exhibit exaggerated characters as weapons or ornaments. Among the numerous amphipod species (Amphipoda, Crustacea) showing sexual dimorphism, caprellids (Caprellidae) are characterized by considerably larger males that possess weapons, although the developmental processes underlying these sex-related differences are largely unknown. Therefore, to clarify the process of sexual differentiation during postembryonic development in caprellids, morphometric analyses of Caprella scaura were conducted. Principal component analysis using 31 morphometric traits showed drastic allometric changes occurring at two ontogenetic body length (BL) points (i.e., 3.8 and 8.8 mm). In individuals larger than 3 mm, head spines appeared in both sexes, and penises did only in males, allowing the discrimination of juveniles from larvae. Moreover, in larger males (BL > 8.8 mm), traits used in reproductive behavior, i.e., the first antenna, second gnathopod, and first to fifth pereonites, were extremely exaggerated. Observations of pre-copulatory behavior along with morphological assays revealed that sexually mature males could be identified by the size ratio between the triangular projection and palmar spine on the propodus of the second gnathopod. In contrast, female maturation could be determined by the marginal setae of oostegites forming a brood pouch. The body size distribution of sexually mature females was concentrated within a narrow range of BLs (6-9 mm), whereas that of sexually mature males showed a broader range (BL 9-18 mm), suggesting that, in C. scaura, males continue to molt and grow even after sexual maturation via indeterminate growth, to increase their lifetime reproductive success.

Acoustic and postural displays in a miniature and transparent teleost fish, Danionella dracula.

Acoustic behavior is widespread across vertebrates, including fishes. We report robust acoustic displays during aggressive interactions for a laboratory colony of Danionella dracula, a miniature and transparent species of teleost fish closely related to zebrafish (Danio rerio), which are hypothesized to be sonic based on the presence of a hypertrophied muscle associated with the male swim bladder. Males produce bursts of pulsatile sounds and a distinct postural display - extension of a hypertrophied lower jaw, a morphological trait not present in other Danionella species - during aggressive but not courtship interactions. Females show no evidence of sound production or jaw extension in such contexts. Novel pairs of size-matched or -mismatched males were combined in resident-intruder assays where sound production and jaw extension could be linked to individuals. In both dyad contexts, resident males produced significantly more sound pulses than intruders. During heightened sonic activity, the majority of the highest sound producers also showed increased jaw extension. Residents extended their jaw more than intruders in size-matched but not -mismatched contexts. Larger males in size-mismatched dyads produced more sounds and jaw extensions compared with their smaller counterparts, and sounds and jaw extensions increased with increasing absolute body size. These studies establish D. dracula as a sonic species that modulates putatively acoustic and postural displays during aggressive interactions based on residency and body size, providing a foundation for further investigating the role of multimodal displays in a new model clade for neurogenomic and neuroimaging studies of aggression, courtship and other social interactions.

Female Preference for Males Varies with Resource Availability for Reproduction in the Freshwater Goby Tridentiger brevispinis.

Animals with resource-based breeding systems show varying sexual selection modes driven by resource availability. Males of the freshwater goby Tridentiger brevispinis (Pisces: Gobiidae), which are larger, with a longer dorsal-fin, than females, make nests under stones, and provide exclusive parental care of eggs in the nests. For this goby, the nest sites are crucial resources for reproduction. Laboratory experiments that controlled for nest-site abundance were conducted to investigate the effects of nest-site availability on male-male competition and female mate choice. Nest-holding males were on average larger than the average size of all males combined under conditions of low nest-site availability. This result indicates a greater advantage for large males in intrasexual competition for nest sites under conditions of low nest-site availability. Furthermore, egg-guarding males under conditions of low nest-site availability were larger than nest-holding males without eggs. Under conditions of high nest-site availability, the dorsal-fin length of nest-holding males with eggs were longer than those without eggs. These findings suggest that female preference for mates varies qualitatively with nest-site availability. This variation in female preference might result from mate availability that depends upon nest-site availability. The current study concludes that in nest-spawning fishes, nest-site availability can affect the intensity of male-male competition and cause variations of female preference for mates.

Growth trajectories of wild Assamese macaques (Macaca assamensis) determined from parallel laser photogrammetry

Socioecological factors are associated with life-history patterns and growth trajectories among primates. Under certain conditions, selection may favor a temporal decoupling of growth and major life-history events such as sexual maturation or natal dispersal. Yet, empirical tests of these associations in wild populations remain scarce owing to the lack of non-invasive methods to capture growth trajectories. In this study, we first compared two non-invasive methods of digital photogrammetry. Then, we used parallel laser photogrammetry to investigate forearm growth of wild Assamese macaque males and females in their natural habitat at Phu Khieo Wildlife Sanctuary, Thailand to test life-history and socio-ecological hypotheses. Across 48 males and 44 females, we estimated growth trajectories and pseudo-velocity curves by applying quadratic plateau models and non-parametric LOESS regressions. We assessed the development of sexual dimorphism by comparing the sexes at five different ages. Females had completed 96% of their growth at the age at first birth (5.9 years) and ceased growing at 7.1 years of age. Males, in contrast, grew until well after their average age of natal dispersal: they reached 81% of their size at the age of natal dispersal (4.0 years), and ceased growing only at 9.0 years of age, much later than females. Sexual dimorphism in forearm length was driven by an extended growth period in males, which is expected for males dispersing between multimale and multifemale groups and not facing the risk of being ousted by other larger males. Our results contradict the neonatal investment hypothesis that predicts a desynchronization of investment in growth and reproduction only in female baboons, but not other papionins producing cheaper neonates. Furthermore, male Assamese macaques do not delay natal dispersal until they are fully grown, in accordance with predictions of the male-career-framework for species with low to medium level of direct competition.

Nutrient-dependent allometric plasticity in a male-diphenic mite.

Male secondary sexual traits often scale allometrically with body size. These allometries can be variable within species and may shift depending on environmental conditions, such as food quality. Such allometric plasticity has been hypothesized to initiate local adaptation and evolutionary diversification of scaling relationships, but is under‐recorded, and its eco‐evolutionary effects are not well understood. Here, we tested for allometric plasticity in the bulb mite (Rhizoglyphus robini), in which large males tend to develop as armed adult fighters with thickened third legs, while small males become adult scramblers without thickened legs. We first examined the ontogenetic timing for size‐ and growth‐dependent male morph determination, using experimentally amplified fluctuations in growth rate throughout juvenile development. Having established that somatic growth and body size determine male morph expression immediately before metamorphosis, we examined whether the relationship between adult male morph and size at metamorphosis shifts with food quality. We found that the threshold body size for male morph expression shifts toward lower values with deteriorating food quality, confirming food‐dependent allometric plasticity. Such allometric plasticity may allow populations to track prevailing nutritional conditions, potentially facilitating rapid evolution of allometric scaling relationships.

Reproductive Biology of Yellowfin Tuna (Thunnus albacares) in Tropical Western and Central Pacific Ocean

A total of 756 yellowfin tuna (Thunnus albacares) caught by a Chinese drifting longliner in the tropical western and central Pacific Ocean (WCPO) from May 2018 to March 2019 were investigated to describe the reproductive biology of the species. Generalized linear model and polytomous logistic regression for the ordinal response model were employed to assess the effects of biometric and spatiotemporal factors (such as individual fork length (FL), fishing depth, dissolved oxygen, and month) on the reproductive traits of yellowfin tuna. The results showed that FLs ranged from 87 to 163 cm, averaging 115.8 cm (SD = ±14.2) for females and 121.8 cm (SD = ±16.8) for males. The proportion of males in the sampled fish was 0.61 (SD = ±0.29), and larger males (>130 cm) were proportionally predominant. Analyses based on the monthly variation of the gonadosomatic index and monthly proportion of sexual maturity stages of the gonads showed that the main spawning period of yellowfin tuna lasts from September to December. In addition, the 50% first maturity FLs of males and females were 111.96 cm (SD = ±1.04) and 119.64 cm (SD = ±1.30), respectively. This study provides new information on the reproductive development of T. albacares in the tropical WCPO region. These reproductive parameters reduce uncertainty in current stock assessment models, which will ultimately assist the fishery in becoming sustainable for future generations.

Effects of operational sex ratio and male density on size-dependent mating in Minshan’s toads, Bufo minshanicus, on the Tibetan Plateau of China

Abstract In many animal species, an increase in the operational sex ratio (OSR), density or a combination of both should lead to more intensive competition among individuals of the more abundant sex. To test this, we examined pairing patterns of Minshan’s toad (Bufo minshanicus) from six populations between 2008 and 2015 along the eastern Tibetan Plateau in south-west China. OSRs in breeding aggregations of Minshan’s toad are normally male biased and males actively compete with each other for acquisition and retention of mates. We found evidence that deviations from random mating by size varied between populations and between years according to the magnitude of the OSR and male density. Larger males were generally more successful in pairing than smaller males when the OSR was slightly male biased and male density was high. However, the resulting size-disproportionate mating was more evident when OSR was closer to 1.99, indicating a positive correlation with the intensity of aggressive scramble competition. Thus, the intensity of male-male competition may partly explain variation in size-disproportionate mating among populations.

Population structure and reproduction of the alvinocaridid shrimp Rimicaris exoculata on the Mid-Atlantic Ridge: Variations between habitats and vent fields

The shrimp Rimicaris exoculata is the most conspicuous component of vent communities developing around hydrothermal fluid emissions below 2000 m on the northern Mid-Atlantic Ridge (nMAR). Its high genetic connectivity suggests a remarkable ability to produce dispersing larval stages. However, so far brooding females have been rarely observed and reproduction remained enigmatic. Spatially complex population structures related to the heterogeneity of local habitat conditions are described for many vent species, this information being fundamental to gain a better understanding of their life history. Here our aim was to assess such complexity along with reproductive development in R. exoculata populations within two vent fields, TAG and Snake Pit (3620m and 3470m depth respectively). We compared samples collected in January–February 2014 among visually distinct assemblages with different degrees of exposure to vent fluids. Dense aggregations located near active venting included mostly females and immature individuals, while inactive peripheries harbored low density assemblages of large males. Small juveniles gathering around low temperature diffusions belonged to another species, Rimicaris chacei. One third of the sexually mature females were ovigerous at the two vent fields during our sampling period, with lower fecundities and egg sizes in the TAG population. Overall, the observed shrimp distribution patterns were consistent across both vent fields, although a high degree of heterogeneity in population structure was observed locally within dense aggregations, probably reflecting micro-scale variations in environmental conditions. Our results thus highlight spatially complex population structures where R. exoculata females brood eggs within dense aggregations exposed to vent fluids, while peripheral inactive areas may be important mating grounds for adults. In addition, we suggest temporal variability in reproductive activity, increasing in the winter season, which questions potential seasonality in a deep-sea species.

Large eastern grey kangaroo males are dominant but do not monopolize matings

Large eastern grey kangaroo males are dominant but do not monopolize matings

Large males matter: Low sperm reserves in female snow crab (Chionoecetes opilio) off Newfoundland, Canada

Large, male snow crab (Chionoecetes opilio) off Newfoundland and Labrador were heavily exploited throughout their range from 2015 to 2018 leading to biological concerns about the possibility of sperm limitation within portions of the stock. To address this, primiparous females were sampled from six sites off the island of Newfoundland to gather data on their overall reproductive health (e.g., seminal receptacle load, SL, and clutch weight) at the end of this heavily exploited period. Snow crab females had low SLs in comparison to long-term monitoring at nearby sites in the Northern Gulf of St. Lawrence but were similar to historic observations from the Eastern Bering Sea. Seminal receptacle loads were significantly influenced by the female’s carapace width, time since mating (represented by sampling month), as well as site-specific characteristics of the male population (ratio of most competitive males in the population and male time since terminal molt). Clutch weight was significantly influenced by the female’s carapace width, as well as the average size of sexually mature males and the average time since terminal molt of adult males. Our findings show the potential for sperm limitation to occur in populations depleted of large-male snow crab and by extension for excessive fishing of males to diminish reproductive capacity of the stock. These findings highlight the importance of maintaining conservative exploitation rates for snow crab that protect a substantial proportion of large adult males in order to preserve reproductive capacity.

Global-Scale Environmental Niche and Habitat of Blue Shark (Prionace glauca) by Size and Sex: A Pivotal Step to Improving Stock Management

Blue shark (Prionace glauca) is amongst the most abundant shark species in international trade, however this highly migratory species has little effective management and the need for spatio-temporal strategies increases, possibly involving the most vulnerable stage or sex classes. We combined 265,595 blue shark observations (capture or satellite tag) with environmental data to present the first global-scale analysis of species’ habitat preferences for five size and sex classes (small juveniles, large juvenile males and females, adult males and females). We leveraged the understanding of blue shark biotic environmental associations to develop two indicators of foraging location: productivity fronts in mesotrophic areas and mesopelagic micronekton in oligotrophic environments. Temperature (at surface and mixed layer depth plus 100 m) and sea surface height anomaly were used to exclude unsuitable abiotic environments. To capture the horizontal and vertical extent of thermal habitat for the blue shark, we defined the temperature niche relative to both sea surface temperature (SST) and the temperature 100 m below the mixed layer depth (Tmld+100). We show that the lifetime foraging niche incorporates highly diverse biotic and abiotic conditions: the blue shark tends to shift from mesotrophic and temperate surface waters during juvenile stages to more oligotrophic and warm surface waters for adults. However, low productivity limits all classes of blue shark habitat in the tropical western North Atlantic, and both low productivity and warm temperatures limit habitat in most of the equatorial Indian Ocean (except for the adult males) and tropical eastern Pacific. Large females tend to have greater habitat overlap with small juveniles than large males, more defined by temperature than productivity preferences. In particular, large juvenile females tend to extend their range into higher latitudes than large males, likely due to greater tolerance to relatively cold waters. Large juvenile and adult females also seem to avoid areas with intermediate SST (~21.7-24.0°C), resulting in separation from large males mostly in the tropical and temperate latitudes in the cold and warm seasons, respectively. The habitat requirements of sensitive size- and sex-specific stages to blue shark population dynamics are essential in management to improve conservation of this near-threatened species.

The role of epigynal setae in mate choice in the orb-weaver Leucauge argyra

Male and female genital morphology may have strong effects on fitness in spiders. Females of some species of Leucauge produce mating plugs that partially or totally block the entrances to their insemination ducts on the epigynum, forming barriers that reduce the probabilities of future inseminations. While in some species both females and males participate in plug formation, the mating plugs in L. argyra are produced exclusively by females. The epigynum of L. argyra (Walckenaer 1841) is unusual in having a prominent ventral process covered on its anterior side and around its base with long, thick setae. We tested whether male stimulation of these epigynal setae affected female plug formation by removing them from some females but not others. Females lacking setae produced mating plugs immediately after copulation less often than unmanipulated females. However, 24 hr later the mating plugs had disappeared in many females of the treatment group. Setae removal did not affect the amount of sperm stored in the female spermatheca, or the frequency of female attacks. The rate of male genital inflations correlated positively, but mating duration was negatively correlated with sperm stored in female’s spermathecae. Females attempted to attack small males more often than large males. These findings contribute to our understanding of the function of the setae associated with the female genitalia, and the effect of their tactile stimulation on plug formation, and transference of spermatozoids.

ESTIMASI KOMPONEN RAGAM DAN HERITABILITAS BOBOT BADAN PERIODE STARTER AYAM LOKAL

This study aims to determine the diversity and heritability components of the nature of body weight production of local chickens aged 0-4 weeks. The material used in this study were 95 local chickens from 4 male and 20 female. Heritability calculation (h2) uses the nested design method. The results showed the value of heritability (h2) DOC weights in male body weights were 0.429851 and 0.569476 in the third week, while the largest variance component in the third week was 12.28387 and for female in the fourth week was 59.333934 . Heritability (h2) DOC weights for male body weight gain were 0.6840 and 0.5257 in the third week, the variance component given from the largest male was in the fourth week ie 0.39037 and for female in the second week was 0.68931.