The morphology and behavior of dimorphic males in Perdita portalis (Hymenoptera : Andrenidae)

Summary In Perdita portalis, a ground nesting, communal bee, males are clearly dimorphic. The two male morphs are easily distinguished based on head size and shape into (1) a flight-capable, small-headed (SH) morph that resembles the males of other closely related species and (2) a flightless, large-headed (LH) morph that possesses numerous derived traits, such as reduced compound eyes, enlarged facial foveae and fully atrophied indirect flight muscles. The SH morph occurs exclusively on flowers while the LH morph is found only in nests with females. While on flowers, SH males are aggressive, fighting with conspecific males and heterospecific male and female bees, and they mate frequently with foraging females. Using artificial observation nests placed in the field, I observed the behavior of females and LH males within their subterranean nests. LH males are aggressive fighters; males attacked each other with mandibles agape, and male-male fights always ended in the death of one male. LH males are highly attentive to the reproductive behavior of females; they spend increasing amounts of time near open cells during cell provisioning, and mating only takes place immediately prior to oviposition when females are forming the accumulated pollen and nectar into a ball. Based on larvae reared to adulthood in the laboratory, the two male morphs occur in equal proportions. The behavior of males in closely related species, especially P. texana, and the origin and maintenance of male dimorphism are discussed.     

Associative behavior of the fish Cryptocentrus cryptocentrus (Gobiidae) and the pistol shrimp Alpheus djiboutensis (Alpheidae) in artificial burrows

Observations and experiments on the associative behavior of the fish Cryptocentrus cryptocentrus (Valenoiennes) and the shrimp Alpheus djiboutensis De Man from the Red Sea were carried out in artificial burrows. A signal system, bringing about correlated behavior in fish and shrimp, consisted of antennal contact of the shrimp with the fish, tail undulations by the fish and, finally, emergence of the shrimp. The shrimp emerged from the burrow only in the presence of the fish. A constant antennal contact was maintained by the partners while the shrimp was outside the burrow. Emerging from the burrow, the shrimp pushed the fish towards the entrance. Following visual stimulation, the shrimp always retreated back into the burrow with the fish. However, the further back the shrimp was located inside the burrow, the less intense was its retreat with the fish. In the absence of the fish, visual stimulation of the shrimp had no effect. Cleaning of fish by shrimp was observed within the burrow.     

Mineral concentration in tissues during ovarian development of the white shrimp Penaeus vannamei (Decapoda: Penaeidae)

Levels of calcium, magnesium, zinc, copper, iron, and manganese were examined in the muscle, hepatopancreas, and gonad of white shrimp, Penaeus vannamei, females at different stages of ovary maturation. Eyestalk-ablated shrimp were sampled during the intermolt stage and classified using the following maturation stages evaluated histologically: cortical stage, vitellogenesis, previtellogenesis, and without gonadic development. In muscle, the copper concentration was significantly lower in the vitellogenic stage than in other stages of ovary development. In the hepatopancreas, manganese levels were higher in the cortical and vitellogenic stages than in animals in previtellogenesis and without gonadic development. No other influence of ovary maturation on muscle and hepatopancreas mineral content was found. In contrast, in the ovary, significant differences of some mineral concentrations were detected. Zinc, iron, and magnesium concentrations were significantly increased in the cortical stage compared to the vitellogenic and previtellogenic stages. Our results indicate that these elements are selectively accumulated during ovary development, especially when the ovaries reach the cortical stage. Received: 14 March 2000 / Accepted: 30 November 2000     

How do dietary diatoms cause the sex reversal of the shrimp <Emphasis Type="Italic">Hippolyte inermis</Emphasis> Leach (Crustacea,Decapoda)

Hippolyte inermis Leach 1915 is a protandric shrimp largely distributed in Posidonia oceanica meadows and other Mediterranean seagrasses. Previous studies demonstrated several physiological peculiarities, such as absence of female gonadic buds in adult males (the new female gonad is produced starting from few undifferentiated cells), the consequent absence of an ovotestis, 2 yearly periods of reproduction with different population structures (a spring outburst producing both males and primary females, and a fall reproduction producing mainly males), and a process of sex reversal influenced by the diatom food ingested. We performed several laboratory analyses to compare the effects of various species of benthic diatoms, in order to test the effect of different diatoms and provide information on the mechanism of action of the ingested compounds. In addition, we performed molecular tests (TUNEL) and TEM observations, to check the hypothesis that the effect of benthic diatoms may be mediated by a process of apoptosis acting on the male gonad. The results obtained allowed for a ranking of a series of benthic diatoms according to their effects on sex reversal, and a confirmation of the striking effect of Cocconeis sp. diatoms, which are able to trigger the appearance of primary females. We also demonstrated the presence of apoptosis both in the male gonad and in the androgenic glands of postlarvae. The effect is species specific, strictly localized to the male gonad and androgenic gland, and limited to a very short period of time, from the 5th to the 12th day of postlarval development.     

Comparative mating success of smaller male-phase and larger male-role euhermaphrodite-phase shrimp, <Emphasis Type="Italic">Lysmata wurdemanni</Emphasis> (Caridea: Hippolytidae)

The protandric simultaneous hermaphrodite shrimp Lysmata wurdemanni (Gibbes 1850) has a pure searching mating system, i.e., males are continually searching for receptive females and copulation is brief. To examine whether size-based advantage in male–male competition occurs and whether the mating ability of male-phase (M) shrimp equals that of euhermaphrodite-phase shrimp serving as males (Em), mating performance, including mating frequency and precopulatory behavior, of M and Em shrimp was compared using two M:Em ratios. Two experiments were carried out from March 2004 to August 2004 at Florida Institute of Technology’s Vero Beach Marine Laboratory using laboratory-cultured shrimp that originated from Port Aransas, TX, USA. In the two experiments, one parturial euhermaphrodite-phase shrimp acting as a female (Ef) was maintained with one M and two Em shrimp (one with and one without an egg mass), and two M and two Em shrimp, respectively. The M shrimp used were always smaller than the Em shrimp. Experiment 1 showed that there was no significant difference in mating ability between Em with and without egg mass. In both experiments, the M shrimp gained mating partners more frequently than the Em shrimp did. In the experiment with two M and two Em shrimp, mating frequencies of the small M and large M shrimp were similar. Precopulatory behaviors of the M shrimp were more active than those of the Em shrimp. Mating between the small M and larger Ef shrimp was sometimes successful even when the size difference was 20.0 mm total length (TL). Mating between a larger M shrimp and smaller Ef shrimp sometimes failed when the size difference was only 13.0 mm TL. Mating frequency of M shrimp over that of Em shrimp with Ef shrimp increased significantly with increasing density and operational sex ratio. The advantage of M over Em shrimp in obtaining mating partners is probably a result of sexual selection and adaptation, and may partially explain the observed delayed sex change in some L. wurdemanni, i.e., some male-phase shrimp grow very large and never become hermaphrodites.     

Surface glycoproteins are not the contact pheromones in the Lysmata shrimp

Behavioral evidence suggests that some male caridean shrimp, such as those of Lysmata species, identify conspecific females via contact pheromones that coat the cuticle surface of the females. In this study, we attempted to determine whether the contact pheromones in three Lysmata species, Lysmata ankeri, Lysmata boggessi, and Lysmata wurdemanni, are glycoproteins as hypothesized previously in a diverse group of aquatic invertebrates. Twenty lectins were screened and lectin-binding experiments indicated that lectin treatment did not affect mate recognition in the shrimps. The behavior of the male-phase (MP) shrimp in the three treatments (non-lectin-treated MP and lectin-treated euhermaphrodite-phase (EP) shrimp, lectin-treated MP and lectin-treated EP shrimp, and lectin-treated MP and non-lectin-treated EP shrimp) and in the control was not different in responding to lectin-treated and control EP shrimp. All the MP shrimp copulated with lectin-treated and control EP shrimp successfully. All the MP shrimp copulated with ethylenediamine tetraacetate-treated EP shrimp (with glycoproteins removed from their cuticle surface) immediately after they detected the EP shrimp. The results suggest that glycoproteins are not likely to be the contact sex pheromones in the three Lysmata shrimp species.     

Reproductive biology of the common shrimp Crangon crangon (Decapoda: Crangonidae) in the central Irish Sea

Aspects of the reproductive biology of the common shrimp Crangon crangon (L.) were studied in Port Erin Bay, Isle of Man, Irish Sea. Size at sexual maturity was determined from the proportions of ovigerous females and of females with maturing ovaries. The size at which 50% of females are mature is estimated (±95% confidence intervals) as 12.5±0.48 mm carapace length. Based on the proportions of ovigerous females and of mature females, the main breeding season was from January to June. Mean ovarian dry weights indicated two broods (winter and summer), with females bearing winter broods (WB) having higher gonad indices than those with summer broods (SB). WB females with non-eyed eggs and with eyed eggs differed in the regression of ovarian dry weight on carapace length, indicating preparation for laying a second brood. In both broods the moult stages of berried females were related to egg stage. Moulting will occur following the release of the brood. During embryonic development, mean egg length and egg volume were larger in all stages, and the mean dry weight of individual eggs of all stages heavier, in WB than in SB; there was no difference in egg number, however. Consequently, reproductive investment, the proportion of female weight devoted to egg production, was 67% higher in WB (0.20±0.04) than in SB (0.12±0.03). There is a significant effect of egg volume on brood weight, but not on egg number. In both broods, egg number was a negatively allometric function of female body size in non-eyed eggs and an isometric function of female body size in eyed eggs. Brood mortality during incubation was higher in SB (17%) than WB (10%). Differences in the reproductive variables and investment between the two broods of C. crangon are discussed in the light of reproductive strategies and life history.Communicated by J.P. Thorpe, Port Erin     

Effect of FSH and LH on testis during nonbreeding season in Calotes versicolor (Daud.)

Histological and biochemical studies carried out on the male reproductive organs of the Indian garden lizard, Calotes versicolor after the treatment with pituitary gonadotrophins (FSH and LH), showed a significant increase in the weight, protein content and diameter of testis, but decrease in its cholesterol. The spermatogonia, spermatocytes and spermatids increased significantly in the germinal epithelium of seminiferous tubule, and spermatozoa appeared in its lumen. The Leydig and Sertoli cells were hypertrophied with increase in their nuclear diameter. The epidymal weight, diameter and protein content also increased after gonadotrophins treatment. There was a significant decrease in the testicular cholesterol indicating the utilization of cholesterol for steroid hormone synthesis. The combined gonadotrophin (FSH + LH) treatment was more effective than the individual gonadotrophin treatment.     

Offshore spawning by the portunid crabScylla serrata (Crustacea: Decapoda)

The portunid crabScylla serrata (Forskål) is shown to migrate offshore to spawn. Records of 447S. serrata caught as bycatch by trawlers in the tropical waters of northern Australia were analysed with respect to area, depth, distance offshore and month of capture as well as the sex and size of the crabs and whether the females were ovigerous. The crabs were caught mainly in three areas that correspond to the tiger prawn trawl fishery, at between 10 and 60 m depth (mean 28.5 m), 3 to 95 km offshore (mean 17.9 km). Most (87%) of the crabs were captured in October and November, which suggests they move offshore in September and October. No crabs were reported from offshore by February. Over 97% of the crabs caught offshore were female, of these 61.5% were ovigerous. The size range of females (100–109 to 200–209 mm carapace-width size classes) and males (120–129 to 200–209 mm carapace-width size classes) caught was similar. The frequent occurrence in coastal waters of females that are larger than the modal size at spawning, as well as mature females with spent ovaries, suggests that many females return to the coast after spawning. Although some species of portunid crab are euryhaline, mature females of estuarine species migrate to the sea to spawn. The migration byS. serrata described here is far more extensive than would be required to reach sea water salinities; it probably provides a dispersal mechanism for larvae to enable the megalopa stage to recruit to habitats distant from those of the parents.     

Functional cytology of the hepatopancreas of Penaeus semisulcatus (Crustacea: Decapoda) during the moult cycle

In the shrimp Penaeus semisulcatus, the digestive gland functions as the main site for the digestion, absorption and storage of nutrients and metals during the feeding stages of intermoult and for the mobilization of reserves during the non-feeding stages of pre-and post-moult. These different activities are reflected directly in the cytology of the gland. All the epithelial cells show marked fluctuations in frequency and changes in structure, form and function which occur in phase with the moult cycle. The shrimp were collected offshore from Kuwait in 1980.     

Das kommensalische verhältnis zwischen Periclimenes imperator (Decapoda: Palaemonidae) und Hexabranchus sanguineus (Nudibranchia: Doridacea)

The Red Sea nudibranch Hexabranchus sanguineus, rare in this region, was found in the Gulf of Aqaba together with a pair of commensal shrimp, Periclimenes imperator. The behaviour of the shrimp, especially as regards their adaptation to the host, was studied in the field and in an aquarium. The shrimp live on the sea slug, feeding on particles adhering to its mucous surface; they move on it even when it is swimming. The shrimp's colour is well adapted to that of the host. The observed specimens never left a healthy host willingly; when, in aquarium experiments, various red substrates or mucous sea cucumbers were offered beside H. sanguineus, the shrimp always chose the nudibranch. However, dead or injured and motionless slugs were abandoned. Two days after the death of a nudibranch, its commensal shrimp accepted the brown synaptid Euapta godeffroyi as host; on a previous occasion, a shrimp was found living on this latier species in the reef. The adaptation of P. imperator to living on the temporarily free-swimming H. sanguineus apparently represents a special evolutionary stage compared with that of other members of this family, which are mostly commensal with sessile hosts. Only palaemonid cleaner-shrimps feed briefly from free-swimming substrates.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft     

Possible mutualism between females of the subsocial membracid Polyglypta dispar (Homoptera)

Summary Female Polyglypta dispar membracids facultatively guard egg masses or oviposit into masses guarded by other females. Defending females repel at least some enemies of both eggs and nymphs. Eggs of guarding females may be partially protected from parasitism by the presence of additional eggs laid by other females. Females sometimes desert egg masses or groups of nymphs, and undefended masses are sometimes adopted by other females. Some individuals remain on or near the plant where they grew up, and littermates sometimes oviposit into the same egg mass. Some copulating pairs are littermates, while others are not. Females with larger numbers of mature and nearly mature eggs in their ovaries are less likely to defend egg masses, and females desert smaller groups of nymphs more often.     

Delayed breeding in the cooperatively breeding Florida scrub-jay (Aphelocoma coerulescens): inhibition or the absence of stimulation?

To determine whether fundamental differences exist in the reproductive physiology of breeder and nonbreeder Florida scrub-jays (Aphelocoma coerulescens), we compared plasma levels of testosterone (T) and luteinizing hormone (LH) in males, and estradiol (E₂) and LH in females. Although male breeders had higher overall T and larger testes, nonbreeders’ T paralleled that of breeders, and their testes were more than an order of magnitude larger than regressed testes. Breeder and nonbreeder males had equivalent baseline LH, and equivalent changes in LH following a gonadotropin-releasing hormone (cGnRH-I) challenge. The T, LH and GnRH challenge data indicate that nonbreeder males have functional hypothalamo-pituitary-gonadal (HPG) axes. We found no hormonal evidence of inbreeding suppression in males: nonbreeders that did not live with their mothers and those that did had similar T. Male nonbreeders that were exposed to E₂-implanted females had higher T than did controls, suggesting that the lack of within-pair stimulation is a key factor in whether an individual delays breeding. Female nonbreeders had E₂ titres equal to or higher than breeders and neither basal LH nor LH following GnRH challenge differed by breeding status. Nonbreeders’ ovarian follicles were smaller than breeders’, but were larger than they would be during the non-breeding season. These data suggest that nonbreeders were primed for breeding and were simply waiting for an opportunity or a required stimulus. Female nonbreeders that lived in a territory with an unrelated male breeder had significantly higher E₂ than those that remained with their fathers. Similarly, nonbreeders that were captured away from their home territories had elevated E₂. However, nonbreeders that lived with their fathers had E₂ that was equivalent to breeding females, suggesting that inbreeding avoidance may not be the primary factor leading to delayed breeding in females. Received: 13 June 1995 /Accepted after revision: 27 April 1996     

Timing of copulation in the molting and reproductive cycles in a grapsid crab,Gaetice depressus (Crustacea: Brachyura)

From the seasonal changes in the amount of semen in the sperm ducts of males and in the fullness of spermatheca of females, the copulation season of Gaetice depressus in central Japan is considered to approximately coincide with the oviposition season, from March to October. The sperm ducts of all the large males examined contained semen, the amount of which did not vary obviously with stages of the molt cycle or with seasons. The genital apertures of females were normally covered with calcified immobile opercula in this species. The opercula decalcified after molting and again shortly before oviposition, and retained mobility for 1 to 3 d. Shortly after molting, soft-shelled females with mobile opercula did not have well-developed ovaries nor did they copulate with males even if they had a chance. In contrast, all of the hard-shelled females with mobile opercula had well-developed ovaries, and laid eggs within 2 d after the decalcification of opercula regardless of the occurrence of copulation. Laboratory experiments showed that the females normally copulated with males before oviposition. Crabs examined in this study were collected from Shirahama, Wakayama Prefecture, Japan between March 1988 and March 1989.     

Life history strategy of a southern European population of brown shrimp (Crangon crangon L.): evidence for latitudinal changes in growth phenology and population dynamics

This study provides a comprehensive examination of the life cycle dynamics of the brown shrimp (Crangon crangon L.) in the Mondego estuary, Portugal, a habitat located near the southern edge of the range of this species in European waters. The phenology of all life stages was documented (from the occurrence of ovigerous females, developing embryos, planktonic larvae and benthic post-larvae), and migration patterns of larvae into and out of the estuary were examined. Temperature-dependent functions of egg and larval development were combined with data on field abundance to predict the timing and magnitude of occurrence of larvae and recruits. Compared to brown shrimp at higher latitudes, southern conspecifics grow slower, mature earlier and have smaller brood sizes, and larvae have a more protracted settlement period. The Mondego estuary, besides acting as nursery area, is a dynamic platform for C. crangon to use in different stages, sizes and seasons.     

Biochemical composition of the deep-sea red crab Chaceon quinquedens (Geryonidae): organic reserves of developing embryos and adults

Deep-sea red crabs Chaceon quinquedens (Smith) were collected in traps at depths of 860 and 1043 m in the northern Gulf of Mexico. Ovigerous crabs were maintained in the laboratory and the developing embryos were sampled every 2 wk until hatching. Proximate analysis (lipid, protein, carbohydrate, and ash) of embryos was performed to determine patterns and rates of organic reserve utilization during embryogenesis. Midgut gland, gonads, and clutch (as appropriate) of adult crabs (males, non-ovigerous females and ovigerous females) were analyzed for the same components as the embryos. Red crab embryos exhibited different patterns of yolk deposition and subsequent depletion of yolk components during embryogenesis. There was a range of lipid to protein (L:P) ratios among the different clutches examined, indicating plasticity in the relative proportions of lipid and protein yolk. The energy used for embryogenesis was estimated by converting the amounts of lipid, protein and carbohydrate in the embryos to their caloric equivalents; final values, taken from 9 mo-old embryos whose siblings were hatching as zoeae, were subtracted from the initial values of sibling embryos sampled at the time of collection (2 to 3 mo old). The amount of energy consumed during embryogenesis in the laboratory was relatively constant (0.12 to 0.13 cal egg^-1). There was considerable variability among the concentrations of organic reserves in the midgut gland of adult crabs and in the ovaries of females. Variations in midgut gland L:P ratios and ovaries were related to the reproductive status of the females, but there were no trends related to depth of capture.     

Effects of predation and habitat structure on the abundance and population structure of the rock shrimp Rhynchocinetes typus (Caridea) on temperate rocky reefs

Human disturbances, such as overfishing, may disrupt predator–prey interactions and modify food webs. Underwater surveys were carried out at six shallow-water reef barrens in temperate waters of northern-central Chile from October to December 2010 to describe the effects of predation, habitat complexity (low, medium and high) and refuge availability on the abundance and population structure of the rock shrimp Rhynchocinetes typus (Rhynchocinetidae), an important mesoconsumer on subtidal hard substrata. Three sites were within managed (restricted access) areas for fishermen, and three were unmanaged (open-access). Field observations and tethering experiments were conducted to examine the relationship between fish and shrimp abundances, and the relative predation rates on shrimps. Direct effects of predation on R. typus body-size distribution were examined from shrimps collected in the field and fish stomachs. The presence and the abundance of R. typus increased with habitat reef complexity and refuge availability. Shrimp abundance was negatively related to fish abundance in managed areas, but not in open-access areas, where shrimp densities were the highest. Also, predation rates and body-size distribution of shrimps were unrelated, although fish consumed more large shrimps than should be expected from their distribution in the field. R. typus occurred most often in shelters with wide openings, offering limited protection against predators, but providing potential aggregation sites for shrimps. Overall, direct effects of predation on shrimp densities and population structure were weak, but indirect effects on shrimp distribution within reefs appear to have been mediated through behavioural responses. Our study highlights the need to assess both numerical and behavioural responses of prey to determine the effects of predator loss on mesoconsumer populations.     

Variation in the lipid content of wild-caught females of the marine shrimpPenaeus kerathurus during sexual maturation

Changes in total lipids, lipid classes and their fatty acid contents were studied in the ovaries and midgut glands ofPenaeus kerathurus Forskäl females during sexual maturation. The shrimp were captured in the Gulf of Cádiz (southwest Spain) in 1990. The lipid content and fatty acids, in relative terms, increased during ovarian development. The greatest changes occurred between Maturation Stages III and IV. Ovarian lipids were dominated by polar classes, whereas in the midgut gland the major classes were triacylglycerols and sterol esters. The amounts of major fatty acids in ovaries (16:0, 16:1n-7, 18:1n-9, 18:1n-7, 20:5n-3 and 22:6n-3) increased with increasing maturity, but declined slightly between Stages III and IV. The total polar lipid content of the midgut was 5.7% (by dry weight) and its fatty acid composition remained constant during the whole study period. Total lipid content of the midgut gland showed an upward trend during sexual maturation, except between Stages II and III, when a slight decrease was observed. Predominant fatty acids in the midgut gland (16:1n-7, 20:5n-3 and 22:6n-3) displayed a noteworthy decline between Stages II and III, corresponding with the marked increase in total lipid fatty acid content in the ovaries during the same period.     

Divide or broadcast: Interrelation of asexual and sexual reproduction in a population of the fissiparous hermaphroditic seastar Nepanthia belcheri (Asteroidea: Asterinidae)

Asexual and sexual reproduction were studied in an intertidal population of Nepanthia belcheri (Perrier) at Townsville, Queensland, Australia, by regular sampling over a year (March 1976-March 1977) and by histological analysis of gonads. Fission reached a peak in early winter (April–June), when about 45% of the population showed evidence of recent fission. Propensity for fission was unrelated to longest arm length. Seven-armed seastars predominated in the population and these underwent fission in two stages to produce one 3-armed fragment and two 2-armed fragments. Fission planes were not related to numbers or positions of madreporites. Hermaphroditism was a normal sexual condition in the population. Almost all gonads contained oocytes, but some gonads functioned as ovaries (without spermatogenic tissue) while others functioned as testes. Seastars with mature ovaries were significantly larger than those with mature testes, indicating protandry, as in other hermaphroditic asteroids. However, fission complicates the pattern of gonad development by causing regression or retardation of gonads and by apparently having a masculinizing effect, so that ovaries may change to testes in fission products. There was a period of sexual reproduction in early summer (October–November). This followed the period of intense fission and regeneration, and a population change from predominately functional females to males. Consequently there was an extreme imbalance against mature females at sexual reproduction, further reducing potential fecundity. Thus, sexual reproduction was very subordinate to fission as the means of recruitment. The 450 m diam eggs probably give rise to pelagic lecithotrophic development and, if this is the case, N. belcheri retains the advantage of complementing reliable recruitment from fission with a dispersive phase. The combination of fission and hermaphroditism is particularly advantageous for a very sparse dispersal of larvae, as a functionally dioecious population may develop from one larva settling in a new locality.     

Observations on rock boring by Alpheus saxidomus (Crustacea: Alpheidae)

This study describes some aspects of the distribution, ecology, and rock boring behaviour of the shrimp Alpheus saxidomus Holthuis from the Pacific coast of Costa Rica. This species has a typical hammer-shaped dactylus on the first right pereiopod of females and males that shows tracks of abrasion at the hammer-head. Structural analysis of this hammer-dactylus proved that it is suited for the mechanical treatment of rocks. The very thick and calcified cuticle of the hammer is mostly formed by the sclerotinized, hard exocuticle, which has abundant pore canals.