Otolith morphology varies between populations,sexes and male alternative reproductive tactics in a vocal toadfish Porichthys notatus

In this study, the morphology of sagittal otoliths of the plainfin midshipman fish Porichthys notatus was compared between populations, sexes and male alternative reproductive phenotypes (known as ‘type I males or guarders’ and ‘type II males or sneakers’). Sagitta size increased with P. notatus size and changes in shape were also detected with increasing body size. Porichthys notatus sagittae begin as simple rounded structures, but then elongate as they grow and take on a more triangular and complex shape with several prominent notches and indentations along the dorsal and caudal edges. Moreover, the sagittae of the two geographically and genetically distinct populations of P. notatus (northern and southern) differed in shape. Porichthys notatus from the north possessed taller sagittae with deeper caudal indentations compared to P. notatus from the south. Sagitta shape also differed between females and males of the conventional guarder tactic. Furthermore, guarder males had smaller sagittae for their body size than did sneaker males or females. These differences in sagittal otolith morphology are discussed in relation to ecological and life history differences between the sexes and male tactics of this species. This is the first study to investigate teleost otolith morphology from the perspective of alternative reproductive tactics.     

Sperm maturation and male tactic-specific differences in ejaculates in the plainfin midshipman fish Porichthys notatus

Using the plainfin midshipman fish Porichthys notatus, a species with alternative reproductive tactics (ARTs), we investigated how sperm maturation shapes sperm competitive abilities. We compared sperm performance and morphology before and after final sperm maturation by sampling sperm from the testes and stripped ejaculates of guarders and sneakers. In accordance with sperm competition risk theory, ejaculates from sneaker males had three times as much sperm as ejaculates from guarder males and sneaker males produced faster swimming sperm than guarder males, but this was only the case after final sperm maturation had occurred. Additionally, fully mature sperm found in ejaculates had larger heads and midpieces than sperm found in the testes. These results emphasize the important role played by non-sperm components of an ejaculate in mediating sperm performance and potentially also morphology.     

Predation on eggs by conspecific males in two Japanese damselfishes,Pomacentrus nagasakiensis andChromis notatus notatus,after removal of egg-guarding males

Egg predation by conspecific males of damselfishes,Pomacentrus nagasakiensis andChromis notatus notatus, was studied at Bohnotsu (31°15′ N, 131°15′ E) and Tsuyazaki (33°47′ N, 130°29′ E), respectively. InP. nagasakiensis, 7 egg-guarding males were removed from nests, and intrusion and egg predation by conspecific males took place in all of the nests within an average time of 12.2 min. Frequency of attacks on eggs by other reef fishes during the period between the removal of egg-guarding males and intrusion of conspecific males was lower than expected, considering the frequency of aggressive displays of the egg-guarding males. The results of male removal experiments forChromis notatus notatus were almost the same, with intrusion and egg predation by conspecific males occurring in all 12 of the nests from which egg-guarding males had been removed. SixP. nagasakiensis and 15C. notatus notatus which intruded into the nests and preyed on eggs were collected. All were males except for 1C. notatus notatus female. Results suggest that these males which intruded into vacant nests to eat eggs did not have clutches of their own during the spawning bouts when the experiments were done. Results also showed that the intruding males were not inferior to egg-guarding males in standard length, gonadosomatic index, and condition factor. It is clear that males which do not have their own clutches during at least 1 spawning bout and prey on others' eggs when egg-guarding males disappear are common in these 2 gregariously nesting damselfishes. It is discussed that conspecific eggs are potentially a good food source not only for other species of reef fishes but also for conspecific males which do not have their own eggs during the spawning bouts. The origin of males wich prey on eggs of other conspecifics is also considered. Some aspects of egg-guarding and aggressive behavior of males in damselfishes are discussed.     

Tactic changes in dusky frillgoby Bathygobius fuscus sneaker males: effects of body size and nest availability

Field and laboratory studies were conducted to examine the effects of nest availability and body size on changes in male mating tactics from sneaking to nest‐holding in the dusky frillgoby Bathygobius fuscus. In the field, the body size of nest‐holding males decreased from early to mid‐breeding season, suggesting the possibility of a change in the tactics of sneaker males to nest‐holding. Many sneaker males did not use vacant spawning nests even when size‐matched nests were available, but they continued to reproduce as sneakers. Similarly, in aquarium experiments with available vacant nests, some sneaker males became nest‐holders irrespective of their body size, but some did not. These results showed that nest availability is not a limiting factor for changes in tactics by sneaker males in this species. Because tactic‐unchanged sneaker males were co‐housed with larger nest‐holding males in the tanks, the body size of nearby nest‐holding males may have affected the decision to change tactics for sneaker males. Moreover, smaller individuals among tactic‐changed males tended to spend more time until spawning, probably because they had relatively larger costs and smaller benefits of reproduction as nest‐holding males compared to larger males.     

Cognitive ability is heritable and predicts the success of an alternative mating tactic

The ability to attract mates, acquire resources for reproduction, and successfully outcompete rivals for fertilizations may make demands on cognitive traits—the mechanisms by which an animal acquires, processes, stores and acts upon information from its environment. Consequently, cognitive traits potentially undergo sexual selection in some mating systems. We investigated the role of cognitive traits on the reproductive performance of male rose bitterling (Rhodeus ocellatus), a freshwater fish with a complex mating system and alternative mating tactics. We quantified the learning accuracy of males and females in a spatial learning task and scored them for learning accuracy. Males were subsequently allowed to play the roles of a guarder and a sneaker in competitive mating trials, with reproductive success measured using paternity analysis. We detected a significant interaction between male mating role and learning accuracy on reproductive success, with the best-performing males in maze trials showing greater reproductive success in a sneaker role than as a guarder. Using a cross-classified breeding design, learning accuracy was demonstrated to be heritable, with significant additive maternal and paternal effects. Our results imply that male cognitive traits may undergo intra-sexual selection.     

Interspecific differences in male cannibalistic behavior between two sympatric cardinalfishes (Pisces: Apogonidae)

Cannibalistic behavior of a paternal mouthbrooding cardinalfish, Apogon notatus, was examined and compared with that of a sympatric congener, Apogon doederleini. In both species, males sometimes cannibalized their own entire broods, but their postcannibalistic behavior was markedly different. Males of A. doederleini respawned within a few days of cannibalism, usually changing mates, whereas males of A. notatus took several weeks to respawn, less frequently changing mates. This difference was attributed to mate availability for males. The operational sex ratio was female biased in A. doederleini but male biased in A. notatus, suggesting that the former males have higher mate availability and thus opportunities for remating soon after cannibalism. For male apogonids that accept only one clutch at a time, an effective way to compensate for reproductive loss entailed by filial cannibalism is to remate as soon as possible after cannibalism. The higher rate of filial cannibalism by A. doederleini than by A. notatus suggests that this cannibalism is facilitated by high mate availability. In contrast to filial cannibalism, heterocannibalism was more frequent in A. notatus. High population density and gregariousness may be important factors contributing to the frequent occurrence of heterocannibalism. Received: January 6, 1999 / Accepted: May 14, 1999     

Parasitic spawning in sand gobies: an experimental assessment of nest-opening size, sneaker male cues, paternity, and filial cannibalism

Sneaking is common in nest-building fish with paternal care,but the role of nest-opening size in protecting against entryby sneaker males has never been tested before. Using the sandgoby (Pomatoschistus minutus), a fish with exclusive paternalcare, experimental manipulations of nest openings provided nosupport for the hypothesis that nest openings serve as physicalor visual defense or that sneaker males prefer to parasitizenests with wide openings. Female mating preference was alsonot influenced by nest-opening size. However, female courtshipbehavior and visibility were important cues for sneaker males.Most sneak entries occurred when the nest holder was occupiedwith courtship, chasing another sneaker male or nest building.In half the cases of observed sneak entry, the sneaker malefertilized eggs, also when sneaking only occurred before spawning.Sneak entry and its duration were good estimates of stolen paternity,but neither sneak entries nor degree of fertilizations werecorrelated with filial cannibalistic behavior. Testes size didnot explain parasitic spawning success in replicates with geneticallydetermined sneaking. However, all sneaker males without breedingcoloration had huge testes and small sperm duct glands, whereasnest-holding males had small testes and large sperm duct glands,and sneaker males with breeding coloration were intermediate.     

Unravelling the evolution of complex reproductive traits with phenotypic engineering

The social dynamics surrounding courtship, mating and parental care are complex enough when just a single male and female are involved, but for species that employ multiple strategies for achieving fertilization success, the network of interactions among rivals, allies and suitors can be utterly complicated. Such is the case in the ocellated wrasse, Symphodus ocellatus, in which males adopt one of three mating strategies. The large, colourful “nesting males” court females, defend territories and care for fertilized eggs until they hatch. The smaller “satellite males” help the nesting males court females and guard against the third morph, the “sneaker males”, which sneak in when a nesting male is spawning with a female and surreptitiously release sperm. Sneaker males perform no courtship displays nor defend territories, so their reproductive investment is devoted entirely to sperm production. And these alternative male strategies work: 100% of nests contain some eggs fertilized by sneaker and satellite males, despite the fact that parental care is solely the responsibility of nesting males In this issue of Molecular Ecology, work to untangle the proximate mechanisms regulating the reproductive physiology of nesting males and their behaviour towards other males, which impacts the entire social network. Moreover, they describe how variation in neuroendocrine regulation can give rise to variation in reproductive traits, upon which sexual selection can act.     

Diet composition of chub,Squalius cephalus (Teleostei: Cyprinidae), in Lake Tödürge,Sivas, Turkey

Digestive tract contents of 241 specimens captured between March 1998 and November 1999 were analysed using both qualitative and quantitative methods to determine diet composition and feeding habits of Squalius cephalus (L., 1758) inhabiting Lake Tödürge, Turkey. Ages ranged from I to VI years; 60.6% of the fish were females, 39.4% males. The chub population appeared to consume a wide range of food items such as phytoplankton, zooplankton, nematodes, insects, fish, macrophytes, plant and animal detritus, whereby zooplankton (69.2%) predominated. Although individuals in the age I group preferred plankton (phytoplankton frequently; zooplankton infrequently), the older specimens (age groups IV, V and VI) behaved mostly as carnivores but also consumed some macrophytes. While there were no significant differences between diet compositions of males and females, seasonal changes were observed in frequency of occurrence, quality and quantity of consumption, and feeding activity. The chub specimens fed most heavily during spring (the pre‐spawning period: March, April and May). Highest food volume (13.0 cm³) consumed was in May and the lowest in September (2.0 cm³) while also being correlated with temperature. All of the food items were found in the digestive tract (82.1% of the specimens examined over all seasons). Highest fullness (84.9%) was reached in autumn and the lowest during summer (79.8%).     

Description of alternative male reproductive tactics in a shell-brooding cichlid, Telmatochromis vittatus, in Lake Tanganyika

Telmatochromis vittatus (Cichlidae) is a Tanganyikan substrate brooder which spawns in the gastropod-shell nests of a cichlid, Lamprologus callipterus. We describe male reproductive tactics of T. vittatus in and around the shell nests, where males of various sizes were found. Based on utilization patterns of the shell nests, interactions among males, and spawning behaviors, males could be categorized into four types based on reproductive tactics and in order of body size: sneaker males, satellite males, territorial males and piracy males. Size range of males in tactic groups rarely overlapped. Territorial males defended shell nests harboring multiple females, but during pair-spawning they were occasionally taken over by large piracy males that visited several nests repeatedly. Small sneaker males darted to pair-spawning territorial males and might ejaculate sperm. Satellite males did not perform parasitic spawning but pair-spawned in a single shell outside the nests. Spawning of satellite males was infrequently parasitized. The largest gonado-somatic index (GSI) was found in sneaker males followed by piracy males, territorial males and satellite males, suggesting that gonadal investment of males using the four tactics may be consistent with intensity or risk of sperm competition.     

Evolution of sperm quality but not quantity in the internally fertilized fish Xiphophorus nigrensis

Abstract Species with alternative reproductive strategies are characterized by discrete differences among males in suites of traits related to competition for fertilizations. Models predict sneaker males should allocate more resources to their ejaculates because they experience sperm competition more frequently and often occupy a disfavoured ‘role’ owing to subordinance in intramale competition and female preferences for larger males. We examined whether sperm number and quality differed between male strategies in the internally fertilized fish Xiphophorus nigrensis and explored the relationship between sperm morphology and performance. We found sneaker males had similar testes sizes compared to courting males but ejaculates with both more viable and longer lived sperm. Sneaker sperm also had longer midpieces, which was positively correlated with both velocity and longevity. Our study suggests that the evolution of sperm quantity and quality can be decoupled and that the sperm morphology is likely to play an important role in mediating sperm competition through its effects on sperm performance.     

Food consumption in Gerris (Hemiptera)

Summary The parameters influencing food consumption in larvae and adults of five species of Gerris were studied. An experimental components analysis was utilized with emphasis placed on measurements of the length of time the insects spent handling food items, and the amount of food in the gut at any one time. The following characteristics were noted: (1) The maximum feeding time required to achieve satiation was 2–2.5 h for all gerrids above 10 mg wet weight. For gerrids below this weight, feeding time declined at a logarithmic rate. (2) Body size had little influence on the duration of the feeding period after food deprivation; only with the first and second instar larvae was a significant difference noted. (3) The average duration of the feeding and non-feeding periods was 10.4 and 24.6 min respectively for satiated adult G. remigis in the presence of excess food. (4) Signifcant differences in relative digestive rate existed between adult and larvae irrespective of species. (5) The smaller the gerrid, the greater the volume relative to its body weight that could be consumed at a single feeding, and for all gerrids, the amount consumed per day was greater than the maximum amount that can be ingested at a single feeding, this difference being larger in the larvae than in the adults. (6) The relationship between daily amount consumed and temperature was linear for four species, increasing with increasing temperature; food consumption in G. remigis, however, peaked at about 19°C, and declined linearily at temperatures both above and below this value. (7) Irrespective of instar and stadium duration, food consumption for G. notabilis peaked within a stadium about 40% of the way through the stadium.     

The effects of sex,age, season and habitat on diet of the red fox <Emphasis Type="Italic">Vulpes vulpes</Emphasis> in northeastern Poland

The diet of the red fox Vulpes vulpes was investigated in five regions of northeastern Poland by stomach content analysis of 224 foxes collected from hunters. The red fox is expected to show the opportunistic feeding habits. Our study showed that foxes preyed mainly on wild prey, with strong domination of Microtus rodents, regardless of sex, age, month and habitat. Voles Microtus spp. were found in 73% of stomachs and constituted 47% of food volume consumed. Other food items were ungulate carrion (27% of volume), other mammals (11%), birds (9%), and plant material (4%). Sex- and age-specific differences in dietary diversity were found. Adult males and juvenile foxes had larger food niche breadths than adult females and their diets highly overlapped. Proportion of Microtus voles increased from autumn to late winter. Significant habitat differences between studied regions were found. There was a tendency among foxes to decrease consumption of voles with increasing percentage of forest cover. Based on our findings, red foxes in northeastern Poland can be recognized as a generalist predators, consuming easily accessible and abundant prey. However, high percentage of voles consumed regardless of age, sex, month, or habitats may indicate red fox specialization in preying on Microtus rodents.     

Microsatellite markers and multiple paternity in a paternal care fish, Hexagrammos otakii

The fertilization success of sneaking behavior in a paternal care fish, Hexagrammos otakii, was estimated using microsatellites as genetic markers. Sneaking behavior was observed using a video camera placed near the nest of a breeding territorial male. Two egg masses fertilized by different patterns of sperm emission by the territorial male and sneaker males were examined for paternity discrimination. When a sneaker emitted a large amount of sperm after sperm emission by the territorial male, the sneaker fertilized more eggs than the territorial male. When the territorial male and a sneaker alternately emitted semen, the territorial male fertilized the most eggs. These results suggest that both the amount of emitted sperm and the timing of sperm emission are important factors in sperm competition. Received: November 18, 1999 / Accepted: January 17, 2000     

Spawning behavior of Arctic charr (Salvelinus alpinus): Spawning synchrony,vibrational communication,and mate guarding

A mismatch in synchrony between male and female gamete release in external fertilizers can result in reduced or failed fertilization, sperm competition, and reduced paternity. In Arctic charr (Salvelinus alpinus), males can adopt either a guard or sneak tactic resulting in both pre‐ and postcopulatory competition between males with alternative reproduction tactics. Here, spawning behavior of free‐living Arctic charr was video‐recorded, and their reproductive behavior was analyzed. From evaluating 157 spawning events, we observed that females mainly spawned with a guarding male and that the female and the guarding male synchronized timing of gamete release under sperm competition. Although sneakers spawned with higher synchrony than the guarding male in single‐male spawning events, the average sneaker released his milt less synchronized with the female than the guarding male under sperm competition. Approximately 50% of the recorded spawning events occurred under sperm competition, where each event included an average of 2.7 males. Additionally, sneakers were more exposed to sperm competition than guarding males. An influx of males, in close proximity to the female, occurred during the behavioral sequences leading up to egg release, but this influx seemed not dependent on egg release, suggesting that something else than gonadal product attracts sneaker males to the spawning female. Just before and during the actual release of gametes, the spawning couple vibrates their bodies in close contact and it seems likely that this vibrational communication between the spawning couple, which results in a larger amplitude sound wave than seen under regular courting, reveals time of gamete release to sneaker males. Thus, vibrational communication may enable synchrony between the guarding male and the female, and this might be traded against the cost of higher detectability from surrounding sneaker males, eavesdropping in close proximity.     

Diet and activity budget of <Emphasis Type="Italic">Rhinopithecus roxellana</Emphasis> in the Qinling Mountains,China

We collected data on diet and daytime activity budget, and investigated the phenology of food trees and food abundance for a group of Rhinopithecus roxellana on the East Ridge of Yuhuangmiao in the Qinling Mountains from November 2001 to December 2003. We calculated the seasonal activity budget using data collected by scan sampling from 84 full-day observations (winter 16, spring 18, summer 28, autumn 22 days). During scan sampling we recorded behavioral states, and the food items and species consumed. The subjects consumed 84 plant species, including trees and shrubs of 29 families, and lichens. Food species varied seasonally. The overall diet of R. roxellana consisted of 29.4% fruit/seeds, 29.0% lichens, 24.0% leaves, 11.1% bark, 4.2% buds, 1.3% twigs and 1.0% unidentified items. Because the abundance of different food items varied seasonally, the monkeys had to shift their major food items seasonally. The annual activity budget of R. roxellana was 36.2% time spent resting, 35.8% feeding, 22.9% moving, and 5.1% other behavior. Seasonal changes in activity budget were observed. R. roxellana spent more time moving in autumn, when the quality of the food might be highest, and least time moving in winter when the food quality might be lowest. Thus, this type of monkey has a passive foraging strategy.     

Behavioral activities and diet of Azaras’s capuchin monkey,Sapajus cay (Illiger, 1815), in a forest remnant of the Brazilian Cerrado

ABSTRACT

Azaras’s capuchin monkey (Sapajus cay) is a poorly studied species in ecological aspects. We investigated behavioral activities and diet of a group of S. cay in a remnant of the Brazilian Cerrado. We sought to identify the most frequent behavior that the group engaged in, as well as to verify possible differences in behavioral patterns and diet between adult males and females. From January to July 2012 we collected behavioral and foraging data for a group of 21 individuals using scan sampling. Behaviors and food items consumed were analyzed using percentages and two proportions Z-tests to assess differences between males and females. We obtained 878 scans in approximately 202 hours of sampling effort, resulting in 4,159 individual activity records of capuchin monkeys. The group allocated time to traveling (41.3%), resting (25.5%), feeding (14.3%), foraging (13.7%), and social activities (5.1%). Females spent more time foraging and feeding, while males spent more time resting. Fruits (61.4%), invertebrates (15.3%), and seeds (14.3%) were the most common food items consumed. We did not find differences in food consumption between sexes. Behavioral activities may be influenced by habitat quality of the studied area, opportunistic habits, and plasticity in the diet.     

Coping with low-quality diets: a first account of the feeding ecology of the southern gentle lemur, <Emphasis Type="Italic">Hapalemur meridionalis</Emphasis>, in the Mandena littoral forest,southeast Madagascar

Malagasy primates of the genus Hapalemur are exceptional in their exhibition of specialisations allowing for a folivorous diet despite their small body size. Members of this group are well known for their preference for specific parts of woody bamboo, the primary food resource throughout much of their range. The southern gentle lemur (H. meridionalis), however, inhabits littoral forests that contain little or no woody bamboo. Similar to its closely related congener, the Alaotran gentle lemur (H. alaotrensis), the question is raised as to how these lemurs subsist in this ecological context. The aim of this study was to gain an initial understanding of the ecological niche of the southern gentle lemur in the threatened ecosystem of the littoral forest of southeastern Madagascar. Lemurs were habituated and observed over a 3-month period during the austral winter, allowing for collection of both continuous and instantaneous focal data on their feeding ecology. Preferred food species were identified and collected, and biochemical analyses determined macronutrient and secondary compound values for consumed food items. The diet of the southern gentle lemur was found to be of low nutritional quality, as evaluated through the low protein-to-fibre ratio, especially when compared with other folivores. This lemur is also unique in spending a majority of its time grazing on terrestrial grasses (family Poaceae) during the resource-poor winter months. Our data indicate that Hapalemur spp. possess a behavioural flexibility, and possibly, digestive abilities, higher than previously thought for an animal of its small body size.     

Digestibility of chitin in cod,Gadus morhua,in vivo

Sixteen cod,Gadus morhua (L.), were individually fed a single ration of shrimps,Crangon allmanni. Four fish were killed and examined 6, 12, 24 and 48 h after the fish had been fed. Chitinase activities were measured in the extracts of stomach contents, stomach tissue, pyloric caecae, intestinal contents and intestinal tissue. The level of enzyme activity in different parts of the digestive tract was shown to be dependent on the phase of the digestive process. High concentrations of the chitin degradation product N-acetyl-D-glucosamine were determined in the stomach and in the intestinal contents. Based on the chitin concentration in the food organisms and the individual food uptake, the amount of chitin consumed by each fish could be calculated. Only up to 9% of the ingested chitin was recovered from the intestinal contents of the fish at any given time after feeding (6, 12, 24 and 48 h). In addition, only 2.4% of the chitin consumed with the food could be recovered in the collected faeces of the fish. The 4 cod killed 48 h after feeding had completely emptied their stomach. Chitin digestion in these fish was calculated to have been 90%.     

Prey availability and diet of maned wolf in Serra da Canastra National Park,southeastern Brazil

Analysis of 400 scats of the maned wolfChrysocyon brachyurus (Illiger, 1815), collected in Serra da Canastra National Park from November 1998 to January 2000 yielded 1688 occurrences of 69 identified food items, 49.5% of which were represented by plant items and 50.5% by animal items. According to the frequency of occurrence analysis, the most important food item categories were wolf’s fruit,Parinari obtusifolia (Chrysobalanaceae), small mammals and birds. When the estimated biomass consumption is considered, the animal items became more important (56.8%) than plant items (43.2%). Small mammals were consumed more in the dry season, while miscellaneous fruits and arthropods were consumed mostly in the wet season. Functional response was found only for the category miscellaneous fruits; however, seasonality analysis revealed that wolf’s fruit and small mammals were consumed according to their availability in the area. Prey selection was observed for most of the small mammal species, emphasizing a high level of consumption ofNecromys lasiurus, Monodelphis sp. andGracilinanus sp. The finding that most of the diet was composed of fruits and animal items from open areas of the savannah-like Cerrado led us to suggest that the maned wolf spends most of its time preying in this habitat, indicating a need to establish conservation policies for the Cerrado.