Premoult Females Research Articles

The smell of moulting:N-acetylglucosamino-1,5-lactone is a premoult biomarker and candidate component of the courtship pheromone in the urine of the blue crab,Callinectes sapidus

Female blue crabs (Callinectes sapidus) in their pubertal moult stage release unidentified sex pheromone molecules in their urine, causing males to respond with courtship behaviours including a display called courtship stationary paddling and a form of precopulatory guarding called cradle carry. We hypothesized that pheromones are mixtures of molecules and are more concentrated in urine of pubertal premoult females compared with other moulting stages and thus that these molecules are biomarkers (i.e. metabolites that can be used as an indicator of some biological state or condition) of pubertal premoult females. We tested this hypothesis by combining bioassay-guided fractionation and biomarker targeting. To evaluate the molecular mass of the putative pheromone by bioassay-guided fractionation, we separated urine from pubertal premoult females and intermoult males by ultrafiltration into three molecular mass fractions. The <500 Da fraction and the 500-1000 Da fraction but not the >1000 Da fraction of female urine induced male courtship stationary paddling, but none of the fractions of male urine did. Thus, female urine contains molecules of <1000 Da that stimulate courtship behaviours in males. Biomarker targeting using nuclear magnetic resonance (NMR) spectral analysis of the 500-1000 Da fraction of urine from premoult and postmoult males and females revealed a premoult biomarker. Purification, nuclear magnetic resonance, mass spectrometry and high pressure liquid chromatography analysis of this premoult biomarker identified it as N-acetylglucosamino-1,5-lactone (NAGL) and showed that it is more abundant in urine of premoult females and males than in urine of either postmoult or juvenile females and males. NAGL has not been reported before as a natural product or as a molecule of the chitin metabolic pathway. Physiological and behavioural experiments demonstrated that blue crabs can detect NAGL through their olfactory pathway. Thus, we hypothesize that NAGL is a component of the sex pheromone and that it acts in conjunction with other yet unidentified components.

Epibiosis on eggs and brooding care in the burrowing crab Chasmagnathus granulatus (Brachyura:Varunidae): comparison between mudflats and salt marshes

Chasmagnathus granulatus is a semiterrestrial intertidal burrowing crab that inhabits both the unvegetated mudflats and the cordgrass (Spartina densiflora) salt marshes in Mar Chiquita Lagoon (Argentina), where it is considered the ecologically key species. The mass of C. granulatus eggs incubated by females is colonized by epibiotic micro-organisms and accumulates detritus. The type of epibionts that use eggs as a substrate, the infestation degree, the maternal care behaviour and the protection of the incubation chamber were compared between females living on mudflats and on Spartina-dominated areas. In both places, the epibiosis by bacteria and filamentous fungi and peritrichid colonial ciliate was significantly higher in the periphery than in the centre of the brood mass. The accumulation of detritus was higher in the periphery in mudflat females but not in salt marsh females. Moreover, the level of detritus was significantly higher in mudflat than in salt marsh females only in the periphery of the brood. The infestation level of bacteria and fungi, and peritrichids, increased throughout the embryonic development only in mudflat females. The periphery of the brood mass was significantly more contaminated in mudflat than in marsh females, while the central region of the brood mass did not differ between habitats. The pleopods were significantly more contaminated by bacteria and filamentous fungi and peritrichid colonial ciliates in premoult females than in postmoult females, independently from the collection site. The percentage of females with abnormal embryos was significantly higher in mudflats (26.7%) than in marshes (12.3%). Females with late embryos spent more time flapping the abdomen and probing the embryos with the chela. Non-ovigerous females did not perform specific maternal care activities. The volume of brood mass both in early or late stage of development is greater than that of the incubation chamber and, consequently, peripheral embryos are more exposed.

Copper reduced mating behaviour in male shore crabs ( Carcinus maenas (L.))

Many crustaceans use pheromones to find mates and induce mating behaviours. If pollutants impair the ability to detect chemosensory cues and respond to pheromone signals, they could profoundly affect mating. In a series of laboratory experiments, the effect of copper (0, 0.1 or 0.5 mg Cu(II) per litre for 5 days) on specific components of the mating behaviour of male shore crab Carcinus maenas was investigated, as well as differences in sensitivity between red and green colour morphs. The results show that copper exposure clearly altered the response of C. maenas males to a pheromone stimulus (pre-moult female urine) presented alone, together with a dummy female (a sponge injected with pre-moult female urine) or with a real female. Crabs exposed to the highest copper treatment took more than twice as long to initiate search activity after pheromone introduction and their search behaviour was less directed. When offered a dummy female, male crabs showed decreased pheromone discrimination in both copper treatments. Stroking was the only mating behaviour significantly affected, with a 90% reduction in red crabs in the highest copper treatment. Additionally, crabs of the highest copper treatment more often pinched the dummy female (non-mating behaviour). Finally, male crabs exposed to copper more often pinched pre-moult females and it took about three times longer to establish cradle-carrying. Thus, copper affects the ability of males to detect female pheromones, perform specific mating behaviours and to form pairs.

Mate-guarding strategies and male competitive ability in an orb-weaving spider: results from a field study

Competition between males to reproduce has led to various forms of resource-guarding behaviour. A recent theoretical investigation suggested that guarding strategies should be closely linked to the risk of take-over and the competitive ability of males, but experimental evidence is still scarce. We investigated precopulatory mate guarding of premoult females in a solitary orb-weaving spider Zygiella x-notata (Araneae: Araneidae). We tested the hypotheses that larger males should (1) be more successful at guarding, (2) acquire their mates by usurping them from other males (take-over), and (3) start guarding females as close as possible to their final moult. In a field study, we recorded the mating activity of marked males throughout a breeding season and conducted a male removal experiment to suppress male–male competition near randomly selected guarded females. We found strong male–male competition for guarding premoult females. Male take-over occurred frequently in the population, even though guarding was efficient at locally reducing male turnover near females. Large males were overall more successful in their guarding attempts because of their higher competitive ability, but guarding success did not increase linearly with body size. Large males mainly acquired females by evicting previous guardians. They spontaneously started guarding females closer to their moult than small males; however, this was not significant when no direct competition occurred between them. We discuss possible mechanisms to explain variation in guarding duration and success and the evolution of male body size in this spider.

Circatidal Moulting Rhythm in The Shore Crab Carcinus Maenas

Late premoult females from precopula pairs of male and female Carcimts maenas (Crustacea: Brachyura) moulted at times of expected high tide in constant conditions in the laboratory. The data presents for the first time evidence of endogenous, circatidal (−12·4 h) moulting rhythms in a crustacean.Studies on the temporal patterns of moulting in crustaceans have elucidated rhythms of seasonal (annual or biannual), lunar (29·4 d), semilunar (14·7 d) and diel (24 h) periodicities (see Conan, 1985; Fernandez et al., 1994). Examples in the literature of so-called ‘tidal’ rhythmicity of moulting given by Conan (1985) are more correctly referred to as semilunar or neap/spring patterns. There appear to be no reported examples of true tidal (12·4 h) moulting rhythms. Also there is very little evidence in the literature that moulting rhythms phased to geophysical cycles are controlled endogenously. Most studies have been carried out in the field or under L:D cycles in the laboratory and only a few have been undertaken with animals in constant conditions (see Fowler et al., 1971; Bishop &amp; Herrnkind, 1976; Nicol, 1989; Fernandez et al., 1994). Conan (1985) has reported moulting rhythms of circamonthly, circatidal (=circasemilunar) and circadian periodicities but his use of the prefix ‘circa’ is unusual since it more correctly describes free-running rhythms in constant conditions, not environmentally driven rhythms as in the examples quoted. In the present study we sought to determine whether moulting in the shore crab Carcimts maenas (L.) was tidally patterned and endogenous.Over a period of several days in the summer of 1991 large numbers of premoult female Carcinus maenas were obtained by searching for specimens associated with males in precopular pairs.

Chemical Communication and Behavioural Interaction Between Sexually Mature Male and Female Shore Crabs (Carcinus Maenas)

A new behavioural bioassay system has been used to examine chemical communication in the crab Carcinus maenas (Crustacea: Brachyura) and has demonstrated the sexually and temporally specific nature of a putative sex pheromone. Mature premoult and postmoult females evoked sexual behavioural responses from receptive male crabs. No response was obtained when intermoult female and premoult and postmoult male crabs were tested. Postmoult females continued to be chemically attractive to male crabs with a similar intensity to that of late premoult females for &gt;8 d following moulting, and then with a reduced intensity for &gt;14 d. Male C. maenas successfully entered copula with females &gt;13 d after the female moult.

Changes in female anatomy associated with the reproductive moult in Paracerceis sculpta, a semelparous isopod crustacean

Paracerceis sculpta (Holmes) is a sexually dimorphic sphaeromatid isopod crustacean inhabiting intertidal zones in the northern Gulf of California. Adult females in this species undergo a biphasic moult that initiates their sexual receptivity. Coincident with this moult, females experience anatomical changes associated with oviposition and gestation of young within the female marsupium. These modifications restrict female mobility, prevent females from feeding, and ultimately result in obligate female semelparity. In this paper, I describe the external and internal anatomy of premoult, half‐moulted and postmoult females collected from breeding aggregations in intertidal sponges. Field‐collected premoult females possessed hard, lustrous cuticles, and did not contain sperm. Females in half‐moulted condition contained sperm masses in both oviducts. Postmoult females contained developing embryos in internal brood pouches, and possessed cuticles that were pliable, translucent and setose. Embryos completed their development within postmoult females and dispersed from their mothers as mancae. Gestation duration decreased with increasing ambient temperature, from a maximum of 75 days at 12 dGC to a minimum of 13 days at 35 dGC. Female fecundity correlated positively with female body length. Spent females, depleted of lipid stores and muscle mass, died within two weeks of releasing mancae. ‘Female metamorphosis’ is considered a taxonomic character in certain sphaeromatid species descriptions. Anatomical changes in reproductive females similar to those in P. sculpta may occur in these species as well.

Daily movement patterns of the spiny lobster Jasus edwardsii (Hutton) on a shallow reef in northern New Zealand

Daily movement patterns of spiny lobster Jasus edwardsii were investigated in north-eastern New Zealand during 1984 and 1985. The position of tagged lobsters was recorded by searching a mapped area of shallow (<10 m deep) rocky reef at intervals during day and night. Ha ndling during capture for tagging had short-term effects on behaviour. Spiny lobsters were crepuscular and nocturnal although daytime movements were also common during the mating period. No significant relationship was detected between activity of J. edwardsii and any environmental factor, including sea t emperature, hours of darkness or moonlight or population density. Individual spiny lobsters moved in relation to local topography. The median total distance moved at night was 41 m while the median foraging range was only 24 m. The frequency distribution of distance moved was dispersed and near-exponential in distribution, a reflection of the wide range in lobster size and moult state. Activity of spiny lobsters during April-July appeared related to mating. Most premoult females were active at night and moved shelters between consecutive days enabling choice of shelters or mates. Mature males either stayed within their shelter and mated with cohabiting females or moved among shelters by day and night in search of receptive females. During the mating period the total distance moved at night by males≥ 140mm CL was inversely related to size. Any impact J. edwardsii have on prey populations will be restricted to near-daytime shelter.

Laboratory observations on spawning, brood size and egg hatchability of the Antarctic krill Euphausia superba from Prydz Bay, Antarctica

Forty-three female Euphausia superba were collected from three sites in Prydz Bay, Antarctica in January 1985. Most gravid females took 3 to 14 d to spawn after capture and some less mature females released eggs after 21 d. Most females spawned only once; overall mean brood size was 2 809 eggs and mean hatchability for eggs from the premoult females was 69.7%. For seven females spawning a second time, overall mean brood size was 597 eggs. Mean hatchability for second-spawn eggs from five premoult females was 67.1%. Possible origins of the second-spawned eggs were small numbers of matured eggs left in the ovaries after the first spawning or eggs developed from those of peripheral nucleolus and vitellogenic stages. Throughout the 8 wk of observations, there was no apparent development of eggs in females which had released all their eggs at one spawning.

Studies on the sex pheromone of the shore crab,Carcinus maenas, with special regard to ecdysone excretion

Abstract Shore crabs (Carcinus maenas) were submitted to new bioassay procedures, and ecdysone excretion was measured by RIA technique to answer the question, whether the common moulting hormone of arthropods acts as a sex attractant in this species. The results indicate that juvenile and adult shore crabs excrete ecdysones during the entire moulting cycle. An adult pre-moult female excreted batches of ca. 8 ng ecdysones at a 3.75 h frequency. Artificial ecdysone solutions did not show any pheromonal activity. The unknown pheromone is probably excreted rhythmically by pre-moult females via the antennal glands. Its action range proved to be no longer than 10–20 cm. The pheromone shows interspecific action between Carcinus maenas and Macropipus depurator.

Pair Formation in the Edible Crab (Decapoda, Brachyura)

between 1 and 12 days (mean 4.8 ? 0.8 days) (Edwards, 1966). This study aimed to investigate the hypothesis that the male recognises and is attracted to the pre-moult female by a water-borne chemical stimulus which she releases, a pheromone. In a number of other crabs where females mate only immediately after ecdysis, and where ecdysis is usually preceded by prolonged pairing, the mature pre-moult female releases such a pheromone into the water with her urine. This is absent from the urine of males, intermoult females and immature pre-moult females. It activates the males, eliciting searching behaviour and characteristic postures or displays. Pheromone production has been demon strated in Carcinus maenas (L.) and Macropipus holsatus (Fabr.) (Eales, 1974), Pachygrapsus crassipes Randall (Kittredge et al., 1971 ), Paratelphusa hydrodromus (Herbst) (Rajulu et al., 1973) and Portunus sanguinolentus (Herbst) (Ryan, 1966; Christof ferson, unpublished). In Colline et es sapidus Rathbun, Teytaud (1971) considered that the female was attracted by a male pheromone, but Jachowski (1974) recorded that the water in which pre-moult females had been kept stimulated male crabs to perform courtship displays. Admittedly none of the above species are in the Cancridae, but several observations suggest that a similar mechanism occurs there. Pre-moult females of Cancer productus Randall appear attractive to males (Knudsen, 1964). Kittredge et al. (1971) produce experimental evidence which indicates pheromone mechanisms in several species of Cancer, and Snow & Nielsen (1966) record for Cancer magist er Dana that ...when the new females were introduced the male became quite active. He approached the new

Sex Pheromone in the Lobster, Homarus americanus

SEXUAL recognition and attraction in many insects have been shown to involve chemical communicants called pheromones1, and these results are widely applied in agriculture2. In contrast very little is known about (sex) pheromones in crustaceans, the only experimental verification being that of Ryan3 who observed that males of the Pacific crab, Portunus sanguinolentus, displayed towards water from premoult females. No response was obtained after the excretory pores of the females had been sealed. A few other publications on crustacean behaviour and natural history suggest such a chemical communication system. Berry4 observed in Panulirus homarus that “male lobsters show sudden attraction to particular sexually mature females” and speculated that the tegumentary glands may be involved. Hughes and Matthiessen5 stated that “it appears as if the freshly moulted female (Homarus americanus) exerts a chemical attraction on the male”. Some other indications for the existence of a sex pheromonecan be found6 without experimental evidence, however. This lack of experimental evidence, even in reports on crustacean mating behaviour7, is remarkable considering the economic importance of such Crustacea as lobsters and shrimp and the benefits for culturing these animals, if a sex pheromone were known and available.