Size at maturity,fecundity and reproductive potential of a protected population of the spiny lobster<Emphasis Type="Italic"> Palinurus elephas</Emphasis> (Fabricius, 1787) from the western Mediterranean

Protected lobster populations are expected to contribute to the replenishment of fished populations through increased egg production. We studied the reproductive biology and egg production potential of a population of the spiny lobster Palinurus elephas protected from fishing since 1990 in the Columbretes Islands Marine Reserve (western Mediterranean). An index of spawning potential was derived to compare egg production potential in the Reserve and in western Mediterranean exploited populations. Females' physiological maturity (ability to reproduce) and functional maturity (ability to mate and bear eggs) occurred at a carapace length (CL) of 76–77 mm. Males' physiological maturity occurred at a slightly larger size, 82.5 mm CL. In the Reserve, P. elephas' individual fecundity increases linearly with body size up to the females' maximum size, although maximum reproductive yield (eggs per body gram) was reached at intermediate sizes. Size-specific fecundity in the protected population was similar to that of lightly fished populations off Ireland and greater than that of western Mediterranean exploited populations. The female size class of 105–110 mm CL contributed most to egg production in the protected population and is well above the minimum landing size (MLS) for western Mediterranean fisheries. Newly mature females (below MLS) generate a very small fraction (1%) of the egg production from the Reserve. Given the pattern of exploitation in western Mediterranean fisheries, egg production potential depends more on the quantity than on the mean size and fecundity of the available females. The role of the greater availability of large males for mating in unfished populations is discussed in terms of the females' individual fecundity and mating success.     

Population structure and growth in captivity of the spiny lobsterPanulirus penicillatus from Dahab,Gulf of Aqaba,Red Sea

Panulirus penicillatus (Olivier, 1791) (Decapoda: Palinuridae) is the most common spiny lobster in the Red Sea and is widely distributed in the Indian and Pacific Oceans. Lobsters (n=377) were collected on four occasions during 1986 on the coral reef at Dahab, Sinai, Egypt. Average size of the collected individuals was 70.5±24.6 mm carapace length (CL) for males and 63.2±15.9 mm CL for females. The sex ratio was 1:1.64 males to females. Length increment per molt was inversely correlated with size and ranged from 2.1 mm per molt in the 40 to 50 mm CL size class to less than 1 mm in the 60 to 70 mm CL size class. Average intermolt period was ca. 136 d for all size classes. The relationship between carapace length and body weight was expressed by the equation:W _b=6.43 × 10^–4 × (CL)^2.89.P. penicillatus from Dahab differ in size, sex ratio and growth rate compared to other palinurid populations throughout their range. This might represent the effect of isolation and location at the edge of the geographical range for this species. It may also indicate an adaptation to their unique habitat in the coral reef in comparison to other palinurid species.     

Reproductive biology of the spiny lobster, <Emphasis Type="Italic">Panulirus Penicillatus</Emphasis>, in the southeastern coastal waters off Taiwan

The reproductive biology of spiny lobster, Panulirus penicillatus, was studied based on 2,068 lobsters, ranging from 34.28 to 131.60 mm carapace length (CL), sampled in Taitung coastal waters from September 2003 to December 2004. The overall sex ratio approximated 1:1 (χ² = 0.02, P > 0.05), but the monthly sex ratios in 2004 showed significant differences and males were predominant in sizes larger than 80 mm CL. Reproductive activity, assessed using histology, a gonadosomatic index and percentage of ovigerous females, indicated that the mature females could be found in every month and that the major spawning occurred from May to September. The presence of re-developing/re-ripe ovaries by month and size-specific spawning time suggest that larger mature females (>60 mm CL) spawn at least three times a year while smaller new mature females spawn at least once a year. For females, the estimated sizes at 50% physiological and functional maturity were (mean ± SE) 56.46 ± 0.56 mm CL and 66.63 ± 1.07 mm CL. The estimated sizes at functional maturity were between 72 and 74 mm CL for males. The number of eggs per spawning event (brood size, BS) was related to CL by the equation Y _BS = 2.4 × 10^-3CL^4.18 (r ² = 0.902, n = 12). Female lobsters with CL ranging from 60 to 80 mm made the greatest contributions to egg production because of their high brood size and active reproductive activity. A minimum legal size should be established for the fishery to protect egg production potential of lobster population in the southeastern coastal waters off Taiwan.     

The effects of gregarine parasites,body size,and time of day on spermatophore production and sexual selection in field crickets

Summary In laboratory experiments measuring the rate of spermatophore production in the field crickets Gryllus veletis and G. pennsylvanicus by confining single males with a conspecific female, 0–10 spermatophores were produced by each male within 24 h. The number of spermatophores produced was unrelated to a male's body size, but was significantly negatively correlated with the natural levels of gregarines, a protozoan gut parasite, in the males. Spermatophore production in the laboratory peaked between 0600 and 1000 h, as did the proportion of courtship songs given by male crickets in the field, suggesting that mating may occur more frequently in the morning. When single males were placed in jars with two conspecific females, 49% transferred spermatophores to both females, whereas 51% of males only gave spermatophores to one of the females. The results support the hypothesis that parasites are important in sexual selection, and are used to propose a new interpretation of post-copulatory guarding in crickets.     

Population characteristics of the deep-sea lobsters Polycheles typhlops and Stereomastis sculpta (Decapoda: Polychelidae) in a bathyal mud community of the Mediterranean Sea

Distribution and abundance as a function of depth, and population parameters such as sex and size structure of the population and aspects of reproductive biology have been studied in the deep-sea polychelid lobsters Polycheles typhlops and Stereomastis sculpta. Samples were taken by otter trawl in the Balearic Sea, a deepsea basin in the northwestern Mediterranean Sea from 1985 to 1989. In both species the largest size classes were dominated by females. In S. sculpta, male and female sizes were very similar. In P. typhlops, ovigerous females and those with external spermatophores were 23 and 25 mm in carapace length (CL), respectively; males with external spermatophores were 17 mm in CL. In S. sculpta, ovigerous females and those with external spermatophores were 24 and 19 mm CL, respectively, and males with external spermatophores 19 mm CL. Highest densities of P. typhlops occurred along the middle slope at depths between 500 and 1000 m. Only small-sized individuals were found at the deepest depths sampled; some recruitment must therefore occur in waters much deeper than those usually inhabited by the adult population. The sex-ratio was 1:1 in most samples, but in some of the shallowest samples females predominated. The depth distribution range of S. sculpta was 981 to 2253 m: densities clearly increased with increasing depth. There were no apparent variations in size distribution as a function of depth. Since very few adult males and females were captured, the population in the survey area would seem to be comprised mainly of juveniles. As a function of depth, females were numerically dominant only in some of the shallowest samples taken in the distribution range of this species. There is strict habitat partitioning between the two species. In both species, the variation in the sex-ratio as a function of depth suggests differential migration between the sexes, probably related to egg incubation and hatching.     

Moulting and reproduction of the spiny lobster Jasus edwardsii (Decapoda: Palinuridae) in northern New Zealand

Aspects of moulting and reproduction of a primarily adult population of the spiny lobster Jasus edwardsii (Hutton) (Palinuridae) were investigated in the field and at an adjacent laboratory in northeast New Zealand from 1982 to 1986. Most males moulted in October/November, ensuring they were in intermoult stage at mating. Females moulted in late April–June, 2 to 3 mo later than females from more southern latitudes. For individual females the specific timing of ecdysis and mating and the length of the interval between them were related to size. Larger females (125 to 135 mm carapace length), tended to moult earlier and wait longer (up to 38 d) before mating, but did so prior to smaller females (95 to 105 mm carapace length, CL) which moulted later, but mated within as few as 9 d. These differences are explained equally well by size-dependent growth processes and by social or chemical inhibition by larger females. Most spiny lobsters (93 to 131 mm CL) moulted at night at depths <10 m. No clear reasons for these behaviours could be found. Eggs were incubated for 101 to 116 d by females in the study population, 70% of the time recorded for more southern areas, these differences probably being related to differences in water temperature. A consequence of earlier female moulting and egg-laying, and longer egg-incubation periods with increasing latitude is that the majority of J. edwardsii larvae hatch in September–November.     

Effect of temperature on growth,sexual maturity and reproduction of<Emphasis Type="Italic"> Acanthomysis robusta</Emphasis> (Crustacea: Mysidacea) reared in the laboratory

The growth, sexual maturity and reproduction of a shallow, temperate-water mysid, Acanthomysis robusta Murano, were investigated by rearing this species through a complete life cycle at 10°C, 15°C, 20°C and 25°C. The average daily growth rate, which ranged from 0.08 to 0.29 mm for immature mysids and from 0.04 to 0.15 mm for mature mysids, increased with increasing temperature. Water temperature had little effect on the molt increment (the increase in body length between successive molts), but clearly shortened the intermolt period (the interval between successive molts) with increasing temperature. Thus, the faster growth rate at higher temperatures is responsible for the shortened intermolt period. External sexual differentiation first became apparent at the 4th or 5th post-marsupial molt, when body length was 4.3–4.9 mm. Thereafter, males reached sexual maturity at the 9th or 10th post-marsupial molt (7.3–9.8 mm in body length), while females reached maturity at the 10th–13th molt (8.2–12.2 mm). In contrast to this small difference in molt number for sexual maturity, the post-marsupial age at first maturity, which ranged from 13 to 57 days for males and from 17 to 78 days for females, decreased markedly with increasing temperature. The incubation time of ovigerous females, which varied from 5 to 24 days, also decreased with increasing temperature. The relationships between water temperature and the three development times, the intermolt period, the age at first sexual maturity and the incubation time conformed to the effective day-degree concept. Although mature females maximally produced four broods in a lifetime, egg-bearing significantly lengthened the intermolt period and consequently functioned as a factor decreasing the growth rate.Communicated by T. Ikeda, Hakodate     

Female rock shrimp<Emphasis Type="Italic"> Rhynchocinetes typus</Emphasis> mate in rapid succession up a male dominance hierarchy

The dynamics of male-male competition for mates and patterns of female choice depend critically on the social environment. We released newly molted sexually receptive females of the rock shrimp Rhynchocinetes typus in the field and recorded their interactions with males. In the dense aggregations in which these shrimp live, most females were encountered and seized by males within 2 min. Usually, females were first seized by subordinate males, and subsequently taken over by the dominant males. Many females (17 out of 23) had multiple mates during the 10-min observation period, and most of them received spermatophores from multiple males. Males used different mating tactics in accordance with their dominance status: subordinate males often used the sneaking tactic, seizing the female and immediately transferring spermatophores. In contrast, all dominant males used the primary mating tactic; they seized and stimulated the female before transferring spermatophores. Results from previous studies had indicated that females may reduce the fertilization chances of subordinate males by delaying spawning and removing spermatophores. We suggest that this capability in combination with the observed rapid mate succession may enable females to exploit male contest behaviors.Communicated by P. Backwell     

Effects of spermatophores on male and female monarch butterfly reproductive success

Summary I present the results of experiments designed to measure the effects of spermatophores produced by male monarch butterflies on male and female reproductive success. There was wide variation in the number of matings by captive males, suggesting the potential for strong sexual selection on males. Male lifespan was not affected by total number of matings, nor did it differ between males that were allowed to mate and those not exposed to females. Two effects of spermatophores on female behavior or fecundity are reported; (1) Females that received large spermatophores delayed remating longer than those receiving small ones. (2) Females allowed to mate several times laid more eggs than singly-mated females. The relative importance of these effects is discussed in relation to monarch mating patterns.     

Reproductive biology of commercially exploited deep-water royal red prawns (Haliporoides sibogae,Solenoceridae) in south-east Australia

Deep-water royal red prawns (Haliporoides sibogae de Man, 1907; Solenoceridae: Penaeidea) were sampled from commercial catches off south-east Australia between November 1988 and May 1990. Four stages of sexual development were distinguished macroscopically for each sex. For the females, histology and analysis of oocyte size were used to validate the macroscopic staging of ovaries into undeveloped, developing, early ripe and ripe. Females were larger than males, reaching a maximum size of 46 mm carapace length (CL) compared to 32 mm CL for males. Average size at sexual maturity was 30.8 mm CL for females and 25.8 mm CL for males. Females apparently breed several times in their life, whereas males probably breed only once. Individual fecundity (ranging from about 58 000 to 140 000 oocytes) was relatively low compared with other penaeids, but oocytes were larger (mean diameter=0.41 mm). Two short breeding seasons occurred per year (February to April and July to August). There was a clear size-related latitudinal distribution of the prawns, with largr prawns (spawners) being more abundant in the northern region of the fishing area, and juveniles (CL20 mm) being more abundant in the south. Most of the spawning stock probably lies outside the main fishing ground, while the fishery targets mainly prawns below the size at maturity.     

Protein content of spermatophores in relation to monandry/polyandry in butterflies

The evolution of a mating system, and specifically mating frequency, is dependent on the costs and benefits to both sexes of mating once or several times. In butterflies, males transfer a spermatophore that contains both sperm and accessory gland products. Accessory gland substances contain nutrients which, in some species, females use to increase their reproductive output and longevity. Nutrients contained in these packaged ejaculates represent investment by males in reproduction. Consequently, the nutritional composition of spermatophores may vary depending on the mating system. There are two lines of arguments concerning the evolution of the nutrient content of ejaculates. One hypothesis argues that male nuptial gifts evolved in the context of certainty of paternity and ease of finding mates; thus spermatophores of polyandrous males (with lower certainty of paternity and greater ease of finding mates) should contain less protein than those of monandrous males, since more spermatophores are produced on average. The other hypothesis argues that polyandry evolved in the context of maximization of male transfer of nutrients to females, and hence spermatophores of polyandrous males should contain more protein than those of monandrous males. In an attempt to distinguish between these two hypotheses, we determined how protein content of ejaculates varied with the degree of polyandry in nine species of pierid and two species of satyrid butterflies. We found that both relative ejaculate mass and protein content increased with the degree of polyandry. Hence our results are consistent with the view that polyandry has evolved in the context of male transfer of nutrients to females, and provides another example of a male adaptation to multiple mating in butterflies.     

Correlates of male mating success in great bustard leks: the effects of age, weight, and display effort

We examined how mating success varied in relation to age, weight, body size, and display behavior among great bustard Otis tarda males. The estimated mating success was strongly skewed, with 45% of adult males being involved in copulation attempts and only 9.7% actually seen copulating successfully. Unlike most birds, body size continued increasing in great bustards several years after reaching sexual maturity. Age, weight, and display effort were all significant and independent predictors of male mating success. The higher display effort involved performing longer full-display bouts. Older males could detach from the male flock earlier in the season as well as on each day and spend longer seasonal and daily periods displaying as solitary birds, which contributed to increase their mating success. In contrast, males weighing more did not invest more in display, which suggests that they could be recognized as dominants by other males and selected by females through assessment of their plumage sexual traits. In contrast to most other bird species, the system described for great bustards resembles that found in some lek-mating ungulates, where social rank is a complex trait determined by both age and mass, and as in these mammals, it suggests that sexual selection continues to favor a high male weight in this extremely sexually dimorphic species.     

Effect of female molt stage and sex ratio on courtship behavior of the blue crab Callinectes sapidus

In many species, males and females actively participate in courtship, and the outcome of pre-mating interactions influences the mating success of both sexes. Female blue crabs, Callinectes sapidus, mate soon after their final molt to maturity; thus female molt stage dictates the timing of mating. In a field experiment, we manipulated female molt stage and sex ratio to test their effects on the courtship behavior of both sexes, if female behavior influences the behavior and pairing success of males, and if male courtship influences male pairing-success. Early-molt-stage females avoided males during courtship, whereas late-molt-stage females sought out males. As a result, males had to pursue and capture early-molt-stage females whereas males displayed to late-molt-stage females and more easily physically controlled them. Males sometimes abandoned late-molt-stage females, but this occurred more often when females were abundant. The rate at which females avoided males was positively correlated with that of males abandoning females, and males that were unsuccessful at pairing met with higher rates of female resistance than successful males, suggesting that female behavior influences male pairing-success. Unlike unsuccessful males, successful males more often made the transition between display and maintaining physical control of the female. At high male sex ratios, males initiated courtship more readily; thus both sexual competition and female behavior influence male courtship in this species. Received: 7 July 1996 / Accepted: 10 January 1998     

Courtship and reproduction in<Emphasis Type="Italic"> Carybdea sivickisi</Emphasis> (Cnidaria: Cubozoa)

Courtship and fertilization events in cubozoans have received little attention from biologists, and much of what we know about these processes is based on conjecture or scant anecdotal evidence. I set out to describe these processes in the cubozoan Carybdea sivickisi by observing mature medusae in vitro. Mature adults engage in courtship during which spermatophores are transferred from the male to the female, who then inserts the gametes into her manubrium. Females accepted multiple spermatophores from multiple males, and only produced one embryo strand. This study also provides evidence that the presence of conspicuous velar spots on the females bell margin is a signal of sexual maturity, and that sexual maturity was not reached in either sex until individuals had a bell diameter of at least 5 mm.Communicated by R.J. Thompson, St. Johns     

Food or sex—males and females in a sex role reversed pipefish have different interests

In a sex role reversed pipefish, Syngnathus typhle, we found that basic life history allocations were directly influenced by sexual selection. We investigated time allocation to foraging and mating, respectively, in a choice experiment, giving males and females, of small or large body size, a choice between food and a potential partner. We found that males were more interested in foraging than mating, i.e., were more frequently observed in front of the food than in front of the partner, whereas females were more interested in the potential partner. This reflects sexual selection operating differently on the two sexes, as males and females are relatively similar in other life history traits, such as growth, mortality, age of maturity, dispersal, and parental expenditure. Moreover, large individuals allocated more time to mating activities, small to feeding. Individuals more interested in mating compared to food were subsequently more critical when given a choice between a large (high-quality) and a small (low-quality) partner, whereas individuals more interested in food were not selective. These findings are consistent with our predictions: sex-role reversed males can be relatively sure of achieving one or more matings, and should allocate more time to feeding and, hence, to parental investment, growth and/or future reproduction. Females, on the other hand, have more uncertain mating prospects and should allocate time to imminent reproductive activities, thereby foregoing other life history traits such as growth and future egg production. By this, they also sacrifice future fecundity and attractiveness.     

Sex ratios,mating behavior and sexual size dimorphism of the northern water snake,Nerodia sipedon

Competition among males to mate is generally associated with male-biased size dimorphism. In this study we examine mating behavior in the northern water snake (Nerodia sipedon), a species in which males are much smaller than females despite substantial competition among males to mate. Competition among males was a consequence of a male-biased operational sex ratio due to slightly higher female mortality from a birth sex ratio of 1 : 1, and, in 1 year, more synchronous and longer mating activity by males. Approximately one-third of both males and females appeared not to mate in a given year. Larger males were generally more likely to attempt mating, but size did not explain the variance in the number of aggregations in which individual males participated. Within aggregations, males that were successful at achieving intromission were larger than unsuccessful males in 1 of 2 years. Variation in condition (mass relative to length) and relative tail length were not generally useful predictors of either mating effort or success in males. Because large size was often advantageous to males, sexual size dimorphism appeared not to be a consequence of sexual selection favoring smaller males. Because sexual dimorphism was evident at birth, and both males and females matured sexually at about 4 years, sexual dimorphism was not simply a consequence of one sex growing at the maximum rate for longer. Female fecundity increased with size, and sex differences in size-fecundity relations may underly the pattern of sexual size dimorphism. However, because multiple mating by females is common, sperm competition is likely to be important in determining male reproductive success. Therefore, allocation of energy to sperm rather than growth may also prove to be an important influence on male growth rates and sexual size dimorphism.     

Life-history traits of Plesionika martia (Decapoda: Caridea) from the eastern-central Mediterranean Sea

Life-history traits of Plesionika martia (Milne Edwards, 1883) were studied through data collected during six seasonal trawl surveys carried out in the Ionian Sea (eastern-central Mediterranean) between July 1997 and September 1998. P. martia was found at between 304 and 676 m depth, with the highest density in the 400-600 m range. Intraspecific, size-related depth segregation was shown. Recruitment occurred in summer at the shallowest depths. Juveniles moved to the deepest grounds as they grew. The largest female and male were 26 and 25 mm carapace length, respectively. The sex ratio was slightly in favour of females at depths >400 m. Although a seasonal spawning peak was shown, the reproduction appears to be rather prolonged throughout the year. Females with ripe gonads were found from spring to autumn. Ovigerous females with eggs in late maturity stage were found year round. Large females could spawn more than one time within their annual reproductive cycle. The size at first maturity (50% of the ovigerous females) was 15.5 mm CL. Average brood size of eggs with a well-developed embryo was 2,966ǃ,521. Iteroparity, low fecundity and large egg size patterns were observed. Brood size increased according to the carapace length. Two main annual groups were found in the field population of the Ionian Sea. Estimates of the Von Bertalanffy growth parameters are: L_X=30.5 mm, k=0.44 year^-1 in females; L_X=28.0 mm, k=0.50 year^-1 in males. A negative allometry was detected mostly in the ovigerous females. The life cycle of P. martia is discussed in the light of life-history adaptations shown in other deep-water shrimp species.     

Parental investment, potential reproductive rates, and mating system in the strawberry dart-poison frog, Dendrobates pumilio

We studied the effect of relative parental investment on potential reproductive rates (PRRs) to explain sex differences in selectivity and competition in the dart-poison frog Dendrobates pumilio. We recorded the reproductive behavior of this species in a Costa Rican lowland rainforest for almost 6 months. Females spent more time on parental care than males, and `time out' estimates suggest that PRRs of males are much higher than than those of females, rendering females the limiting sex in the mating process. Males defended territories that provide suitable calling sites, space for courtship and oviposition, and prevent interference by competitors. Male mating success was highly variable, from 0 to 12 matings, and was significantly correlated with calling activity and average perch height, but was independent of body size and weight. Estimates of opportunity for sexual selection and variation in male mating success are given. The mating system is polygamous: males and females mated several times with different mates. Females were more selective than males and may sample males between matings. The discrepancy in PRRs between the sexes due to differences in parental investment and the prolonged breeding season is sufficient to explain the observed mating pattern i.e., selective females, high variance in male mating success, and the considerable opportunity for sexual selection. Received: 9 June 1998 / Received in revised form: 27 March 1999 / Accepted: 3 April 1999     

A Contemporary,Sex‐Limited Change in Body Size of an Estuarine Turtle in Response to Commercial Fishing

Abstract: Juvenile growth rate and adult body size are important components of life‐history strategies because of their direct impact on fitness. The diamondback terrapin (Malaclemys terrapin) is a sexually dimorphic, long‐lived turtle inhabiting brackish waters throughout the Atlantic and Gulf coasts of the United States. In parts of its range, terrapins face anthropogenically imposed mortality: juveniles of both sexes inadvertently enter commercial crab traps and drown. For adult females, the carapace eventually grows large enough that they cannot enter traps, whereas males almost never reach that critical size. We compared age structure, carapace dimensions, growth curves, and indices of sexual dimorphism for a Chesapeake Bay population of terrapins (where mortality of turtles is high due to crab traps) with contemporary terrapins from Long Island Sound and museum specimens from Chesapeake Bay (neither group subject to commercial crab traps). We also calculated the allochronic and synchronic rates of evolutionary change (haldanes) for males and females to measure the rate of trait change in a population or between populations, respectively. We found a dramatic shift to a younger male age structure, a decrease in the length of time to terminal female carapace size, a 15% increase in female carapace width, and an increase in sexual dimorphism in Chesapeake Bay. In a new twist, our results implicate a fishery in the selective increase in size of a reptilian bycatch species. These sex‐specific changes in life history and demography have implications for population viability that need to be considered when addressing conservation of this threatened turtle.