Reproductive morphology, mating behavior, and spawning ecology of cephalaspid sea slugs (Aglajidae and Gastropteridae)

Abstract. Several recent experimental studies have assessed the behavioral reproductive ecology of four opisthobranch species belonging to the families Aglajidae and Gastropteridae (Cephalaspidea). In order to extend the scope of this earlier work, here we document the reproductive morphology and behavior of 36 taxa belonging to the same two sea slug families. Measurements focus on insemination patterns, spawning characteristics, as well as the size and shape of male and female reproductive organs (i.e., prostate, penis, bursa copulatrix, seminal receptacle). We found that behavioral and morphological traits vary considerably between species, even between closely related taxa. Mating behavior covers the full spectrum from unilateral to simultaneously reciprocal insemination and includes putatively antagonistic mechanisms such as hypodermic injection in some cases. With respect to morphology, particularly great variation was present in traits related to the male sexual function, such as prostate size and penis type. In traits associated with the female function, noticeable variation in those traits accessible for measurement was limited to the relative size of the sperm‐digesting bursa copulatrix. These data provide the basis for future comparative analyses on the evolution of reproductive characters in a phylogenetic context. We further explore the relationship between characteristics and body size. Our data corroborate previous findings that in species with exclusively planktotrophic development, investment per embryo (using mean egg diameter per species as a proxy) is independent of mean species body size. In contrast to egg size, spawn weight and the number of eggs per spawn tightly increased with body size, both within and among species. Hence, larger individuals among planktotrophs increased reproductive investment by increasing offspring quantity rather than investing more into each single offspring. Comparably large eggs with few eggs per spawn in our only two species with facultatively intracapsular metamorphosis are also consistent with findings in other opisthobranchs.     

Diurnal periodicity of spawning activity of permanently territorial damselfishes (Teleostei: Pomacentridae)

Synopsis Like other congeneric damselfishes, the herbivorous Stegastes altus defends individual feeding territories from heterospecific food competitors, regardless of sex. Females spawned demersal eggs for 31.4 min (n = 25) at the nest in territories of males 0–75 m away from theirs. Throughout the spawning season (June to September), spawning occurred only at dawn, mainly just after sunrise. Daily activity of the fish community showed that potential diurnal food competitors were few or inactive only at dawn and dusk. The frequency of intrusions into the female's territory by heterospecific competitors were as low when she left her territory to spawn at dawn, as they were in the daytime when she defended it. Removal of the female in the daytime resulted in a significant increase in intrusion frequency. An ‘anti-competitor hypothesis’, whereby dawn spawning ensures the food resource in the female's territory seems to explain not only the spawning periodicity in S. altus but also the timing of spawning of other permanently territorial damselfishes. Contribution from the Laboratory of Animal Ecology, Kyoto University, No. 492.     

Reproductive variance in planar spawning Chromodoris species (Mollusca: Nudibranchia)

Although variance in life history parameters is well known from comparisons among broad phylogenetic groups of marine invertebrates, there is still an outstanding need to increase empirical studies that compare closely related species. If the species under study share a recent common ancestor and developmental strategy, there is an opportunity to contrast maternal investment against interspecific variation while controlling for evolutionary distance. Furthermore, when these species co-occur, it allows for exploration of potential character displacement. We examined egg size and other factors related to reproduction in four closely related species, co-occurring nudibranchs belonging to the monophyletic Chromodoris planar spawning clade. The duration of oviposition appeared to be conserved and may be phylogenetically constrained in these four co-occurring species. In contrast, egg size differed significantly among species, but was not influenced by parental body length or position within the egg mass for any of the species. The number of egg mass whorls also varied, but did not correspond to the interspecific differences in parental body length. These results suggest that some significant differences exist among these sympatric Chromodoris species that may be candidate traits for character displacement. These characters would need to be re-measured in geographic areas where the studied Chromodoris species do not co-occur.     

Colonial Nesting and the Importance of the Brood Size in Male Parasitic Reproduction of the Mediterranean Damselfish Chromis chromis (Pisces: Pomacentridae)

We investigated male parasitic spawning in a protected natural population of Mediterranean damselfish. Chromis chromis nested in colonies, inside which males showed a high variability in mating success. Our field observations indicate that the egg batches obtained by the most successful fish were five times bigger than the ones obtained by the less successful fish and many males never received ovipositions. On the other hand, reproductive parasitism was a common tactic within the colony. Successful nesting males sneaked into their neighbours' nests depending on the amount of eggs in their nest, with small clutch size inducing the males to parasitic reproduction. Males failing to receive egg depositions on their nests showed a significantly higher parasitism rate than successful males. Non-territorial males occupied stations in the water column above the breeding grounds and whenever the opportunity arose, they disrupted spawning in progress, stealing copulation with females. We observed that the likelihood of males being parasitized by sneakers was not correlated with the size of their own clutch; on the contrary, it depended both on the number of neighbouring nests and on the number of neighbouring males with barren nests (i.e. unsuccessful males). No correlation was found between parasitic behaviour and male size, suggesting males may switch between spawning in their own and in their neighbour's nests depending on mating opportunity. The hypothesis that colonial nesting facilitates parasitic reproduction is here discussed.     

Prostaglandin induction of spawning behavior in Cichlasoma bimaculatum (Pisces cichlidae)

Prostaglandin (PG) stimulates female spawning behavior in goldfish and in some other teleosts in which female reproductive behaviors consist of postovulatory oviposition acts. This study examined the effects of PG on female sexual behavior in a teleost fish, Cichlasoma bimaculatum, in which female reproductive behaviors involve both preovulatory courtship and substrate cleaning behaviors, and post-ovulatory oviposition behavior. In females of established pairs, PGF2 alpha injection (5 micrograms, im) at any stage of the spawning cycle, or in the parental phase, rapidly induced substrate cleaning which soon merged into oviposition behavior (without egg release). These results support a role for PG in oviposition behavior of Cichlasoma. However, indomethacin (1 mg, ip), a PG synthesis inhibitor, did not block oviposition in ovulated females which had begun to spawn. Indomethacin may not have lowered PG levels sufficiently. Alternatively, as shown by J.J. Polder (1971, Neth. J. Zool. 21, 265), oviposition behavior may be induced or maintained by other factors associated with the spawning situation.     

Reproductive migrations of the sex role reversed pipefish Nerophis lumbriciformis(Pisces; Syngnathidae)

Using an individual identification technique, a population of worm pipefish Nerophis lumbriciformis was followed during 19 months, in order to determine the exact use of the intertidal and, considering the specific movement patterns of males and females, the mating system exhibited by this population. Field observations showed that the number of adults increased during the breeding season, with males arriving 1 month earlier than females. Furthermore, males and females presented distinct permanence periods, showing that the intertidal is used as a mating arena. It was also observed that both male and female worm pipefish mated repeatedly over the span of a reproductive season, but females exhibited shorter remating intervals. Also, females stayed for longer periods on the mating grounds, the intertidal zone, whereas males typically left for the subtidal after mating, usually returning within 2 months. These inter‐sexual differences in the occupation of the intertidal suggest that females breed with different males but also that males accept eggs from various females since, on their return, a new group of mating partners was now available. Thus, N. lumbriciformis might be considered polygynandric. It is a clearly dimorphic species in spite of the observed polygynandry, suggesting that differences in remating intervals may be influential in determining the strength of sexual selection along with what may be expected from the polygynandrous mating system alone.     

Sexual selection and reproductive success in males of the bicolor damselfish, Eupomacentrus partitus (Pisces: Pomacentridae)

Relative reproductive success of male bicolor damselfish, Eupomacentrus partitus, was measured as the number of egg batches obtained per week per male during a 14-month field study. Large and consistent differences in spawning success, observed in seven colonies containing 23 males, demonstrated that mating was non-random. Various physical and behavioural characteristics of males were also monitored. Significant correlations (P<0.05) were found between reproductive success and four variables: frequency of courtship, inter- and intraspecific aggression, and total length. The importance of other factors such as size and location of male territories and time allotment to various activities was also considered. The interactions between these variables, as well as preliminary observations of spawning, suggest that intersexual selection, that is female choice of mates, is the dominant process in sexual selection in this species.     

Reproductive success in Zygogramma bicolorata: A role of post-insemination association of male and female

Reproductive success is attained by various mechanisms in insects. Prolonged post insemination association is one such mechanism to increase the reproductive success. The present study was conducted to assess the role of post insemination association of mating partners on reproductive performance in Chrysomelidae beetle, Zygogramma bicolorata Pallister. The matings were disrupted at different time intervals and fecundity and percent egg viability of the females were recorded. In addition, the mounting attempts, mating attempts, time to commencement of mating and latent period were also recorded. It was hypothesized that: (1) the mounting and mating attempts would not exist, (2) copulation duration, would not affect the reproductive performance, and (3) the beetle would not exhibit the mate guarding behaviour. Interestingly, results revealed that 6.00 ± 1.3 and 6.59 ± 0.93 mounting and mating attempts are needed to establish successful mating. The results revealed that males improved their percent egg viability with a mating duration ranging from nearly 30–50 min. While fecundity increased with a mating duration of above 30 min and up to a duration of 60 min. This result concluded that males of this beetle display post copulatory mate guarding behaviour after 60 min in which male rides on female’s back with his aedeagus inserted in the female genital tract.     

迁地驯养孟加拉巨蜥一些繁殖特性的初步研究

2005～2006年对8条孟加拉巨蜥的体重、体长、繁殖行为、卵径等繁殖特性进行了初步研究.雄性巨蜥体重为3390 g±139 g,体长(SVL)为52.9 cm±2.5 cm,雌性巨蜥体重为3320 g,体长(SVL)约49.5 cm.巨蜥发情时间出现在4～8月, 其中50%的发情行为发生在7月份.每次发情持续时间约为8.8±2.1天,两次发情间隔时间约为18.8±3.2天.巨蜥的求偶交配模式包括嗅闻、攀爬、诱导和跨爬4个环节.卵的长径为56.9 mm±2.6 mm(n=21),宽径为33.3 mm±1.5 mm (n=21).繁殖期巨蜥的活动节律表明孟加拉巨蜥是典型的昼行动物.     

Reproductive behavior of the antLeptothorax (Dichothorax) pergandei

Summary Leptothorax pergandei, the only member of the subgenusDichothorax, is a common ant in Chihuahuan desert habitats in southwestern Arizona. According to colony censuses and relatedness estimates, colonies are mostly monogynous and queens typically mate only once. Mating takes place in local swarming flights; virgin queens attract males with secretions from the poison gland. Some dealate queens running on the soil surface directly after the mating flight had well-developed ovaries containing mature eggs and yellow bodies.     

Spatio-temporal patterns of recruitment of labroid fishes (Pisces: Labridae and Scaridae) to damselfish territories

Recent studies have shown that recruitment variability is an important process structuring reef fish assemblages. The aim of this study is to describe the spatio-temporal patterns of recruitment of three abundant labroid taxa (Coris schroederi, Halichoeres melanurus and Scarus spp.), using damselfish territories as replicate units of habitat. Temporal recruitment patterns of each taxa were consistent among three sites along 2 km of reef tract, with small differences among sites probably the result of hydrological or random factors operating at that scale. Recruitment of only one species (C. schroederi) showed consistent differences in the magnitude of recruitment among sites, which was probably due to an overriding effect of habitat selection for the location of the territories on the reef profile at one site. Two taxa, C. schroederi and Scarus spp., recruited in low to moderate rates over many weeks with moderate recruitment peaks detected in one year only. This pattern may be characteristic of many labroid species that have protracted periods of production of larvae. In contrast, H. melanurus recruited in a single short pulse of high magnitude each summer, which suggests that production of larvae by this species may occur over a more restricted period of time. No strong pattern of lunar entrainment of recruitment was detected for any taxa, which may be due to a lack of lunar periodicity in production of larvae. Further studies are now required to identify the processes that are important in determining patterns of labroid recruitment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of mobbing toward predators by the damselfishPomacentrus coelestis (Pisces: Pomacentridae)

Field observations on prey-predator interactions, focusing on mobbing behavior byPomacentrus coelestis, were made in the shallow water of Shirahama, Japan. Within the breeding colony of the damselfish, indirect group mobbing toward 6 ambushers and direct mobbing with physical contact only by nesting males toward a stalker were observed. The direct mobbing toward the stalker (moray eel) is suggested to have involved an element of egg-guarding. Group mobbing was usually released by large and quick attacking motion of the predator. Attack intervals of a predator were much longer after it was mobbed than when it was not mobbed, but there was no significant difference in success ratio of the next attack whether mobbing was elicited or not. Consequently, it is concluded that mobbing effectively reduced future predation risk of each mobber.     

Maternal influences on the sexual behavior and reproductive success of the female rat

In many species, including humans, there is evidence for parental effects on within-sex variations in reproductive behavior. In the present studies we found that variations in postnatal maternal care were associated with individual differences in female sexual behavior in the rat. Females born to and reared by dams that showed enhanced pup licking/grooming (i.e., High LG mothers) over the first week postpartum showed significantly reduced sexual receptivity and alterations in the pacing of male mounting (i.e., longer inter-intromission intervals) observed in a paced mating test. There were minimal effects on the sexual behavior of the male offspring. The female offspring of High LG mothers showed a reduced lordosis rating, a decreased mount:intromission ratio, received fewer ejaculations and were less likely to achieve pregnancy following mating in the paced mating context. The data suggest maternal influences on the sexual development of the female rat that are functionally relevant for reproductive success. Together with previous studies these findings imply that maternal care can ‘program’ reproductive strategies in the female rat.     

Effect of male and female age on the mating success of the obliquebanded leafrollerChoristoneura rosaceana (Lepidoptera: Tortricidae) under different ecological conditions

The present study was undertaken to test the hypothesis that male and female age, as well as temperature, can affect the mating success ofChoristoneura rosaceana, given the role that these two factors play in the pheromone biology of this species. In the laboratory, the mating success of females generally declined linearly with age, whereas in males, it increased during the first 3 days and then decreased. The decline in female mating success was more pronounced under warm than cool thermocycles, while the changes observed in males were greater under fluctuating than constant temperature regimes. The onset time of mating was unaffected by male age, however, older females always mated earlier than younger ones, with the advance being more pronounced at cool than warm temperatures. Similar results were also obtained under field conditions. When a single 3-day-old male was provided with 0-, 3-, and 5-day-old females simultaneously, older females obtained mates significantly more often than younger individuals at all temperatures, indicating that calling earlier may afford a reproductive advantage to older females. At both constant temperatures, the time spent mating was longer in older than in younger females, but not under fluctuating thermocycles. Very young and very old males generally spent more time in copula than middle-aged individuals both at constant temperatures and under the warm thermocycle. Under the cool thermocycle, the duration of mating was considerably prolonged at all ages, which could increase the risk of predation.     

Multiple mating and its effect on the reproductive success of female Epiphyas postvittana (Lepidoptera: Tortricidae)

Abstract.

• 1 Multiple mating and its effect on reproductive performance of female Epiphyas postvittana (Walker) moths were studied under controlled conditions.
• 2 The age at which the moths mated for the first time ranged from the first to the tenth day after emergence, but 71% of first matings were during the first 3 days.
• 3 The majority (63%) of females had one or two spermatophores in the bursa copulatrix. Some (24%) were found with three to five spermatophores, whereas no successful mating occurred among 13% of individuals. The number of matings was partly dependent on the number of mates available to the female. Between the range of sex ratios of one male to one female and four males to one female maximal mating success occurred at the ratio of three males to one female.
• 4 Virgin females were capable of egg-laying, but mating stimulated and accelerated oviposition. Mated individuals laid twice as many eggs as unmated ones.
• 5 The level of copulatory activity did not influence the longevity of females irrespective of the number of males available to them.
• 6 Sex ratios with greater than one male to a female improved the reproductive success by marginally increasing fecundity and fertility.
• 7 It is concluded that multiple mating would enhance population growth, and is of particular benefit to populations with a preponderance of females, as is known to occur naturally in this species.

     

Sociosexual behavior of a free-ranging Cebuella pygmaea (Callitrichidae,platyrrhini) troop during postpartum estrus of its reproductive female

The sociosexual behavior of a free-ranging Cebuella pygmaea troop containing two adult males was studied throughout a postpartum periestrous period of its reproductive female. A clear-cut male-initiated six-day behavioral estrous period occurred from the 13th through 18th day postpartum, with a two-day peak of mating activity on the 15th and 16th days. Both adult males attempted to mate with the female, but the dominant male maintained exclusive mating access to her by guarding behavior and aggression toward the subordinate male. Estrus-related changes in the daily activity pattern included constant following of the female by the male, increased huddling and grooming between the consorts, a decrease in infant carrying, and suppression of insect foraging in the consorting male. Behaviors seen only during the periestrous period included genital presenting by the female, intensive licking and sniffing of her genitalia by the males, female-guarding by the dominant male, anogenital scent-marking on the male's body by the female, tongue protrusion and “tongue vibrating” by the male, and copulations, play chasing, and “consort walking” by the couple. Within the Callitrichidae, genital presenting and tongue vibrating in sexual context have been observed only in Cebuella.     

Behaviour of the female beaugregory damselfish (Stegastes leucostictus)

Much less is known about the behaviour of female beaugregory damselfish than about males of the species. This study was initiated to determine behavioural patterns and interactions of female beaugregories on the back reef of Discovery Bay Marine Laboratory, North shore of Jamaica. Females fed, patrolled, and chased intruders in a significantly larger area and ate significantly more per 15-min observation period than did males. Males spent significantly more time patrolling their territories and chased significantly more total intruders than did females. However, this difference in total chases comes from the fact that males chased the bluehead wrasse, an egg predator, significantly more often than did females while all other species of intruder were chased the same by both sexes. The distance that females travelled from their homesite to court was significantly positively correlated to female body length. This increased distance travelled may relate to mate assessment. Female beaugregory damselfish may be able to be more selective in their choice of mate with increased size and distance travelled.     

Reproductive success in female Neolamprologus mondabu (Cichlidae): influence of substrate types

Individual variation in body size, home range size, and reproductive success among Neolamprologus mondabu (Cichlidae) females were investigated with reference to substrate types in the littoral zone of northern Lake Tanganyika. Larger females occupied sandy substrates and smaller ones stony substrates. Female reproductive success, estimated as the number of offspring successfully released per month, was higher on sandy substrates than on stony substrates. This may be attributable to higher spawning intensity and better protection of broods against predators in open, sandy habitats.     

Reproductive biology and female parental care in the cockscomb prickleback,Anoplarchus purpurescens (Pisces: Stichaeidae)

Synopsis Reproduction and parental care in the cockscomb prickleback, a Pacific coast intertidal fish, were examined using a combination of field and laboratory observations. The sexes were dimorphic, particularly during the breeding season, and males competed with other males for access to females. Males performed lateral and spasm displays. In the wild, the breeding season extended from January to March on cobblestone beaches. Assortative mating was positive with respect to body size. Females exhibited solitary parental care of the eggs. Each female coiled around, guarded and fanned a single egg mass that likely represented her total reproductive effort for the year. The number of eggs in the mass increased linearly with female size (weight or length). Males did not remain after spawning. Aquarium observations revealed that males spawn with more than one female given the opportunity. It is not known whether this occurs in the wild. Incubation to hatching took 29 days. Upon hatching, the young swam towards the surface. Parental care did not extend beyond hatching.