Reproductive behaviour ofNereis diversicolor (Annelida: Polychaeta)

Nereis diversicolor O. F. Müller, collected on the tidal flats of the Jadebusen (North Sea, FRG) in autumn 1987 and 1988, was exposed to different temperatures in the laboratory. Results indicated that maturation was induced by temperatures above 6°C; spawning in early spring was synchronized by raising temperatures after a period of low temperatures in winter, and occurred mainly at new and full moon. During reproduction the female stays inside the burrow; the male releases sperm in front of it; the resultant larvae remain in the tube for 10 to 14 d protected by the female.     

The significance of microbial carbon in the nutrition of the deposit feeding polychaete Nereis succinea

A partial carbon budget was calculated for a population of the deposit feeding polychaete Nereis succinea (Frey and Leuckart) for a North Carolina, USA salt marsh in order to determine if the ingestion and assimilation of microbial carbon was sufficient to meet the carbon requirement. Carbon required by the population was estimated by calculating annual production, 2.1 g C m^-2, and respiration, 9.4 g. There was no net release of dissolved organic carbon. Annual consumption of microbial carbon (as determined by ATP) was estimated to be 5.2 g m^-2. Assimilation efficiency of heterotrophic, detrital microbes was estimated to be 57%. If this value is used for all the microbial carbon, then total assimilation was 3.0 g C m^-2, or about one-fourth the carbon requirement. N. succinea was able to assimilate carbon from sterile plant detritus which suggests that some of the carbon needed to balance the budget may come from direct uptake of the plant substrate. Other possible additional sources of carbon include consumption of meiofauna and uptake of dissolved organic matter.     

Energetic costs of swarming behavior for the copepod Dioithona oculata

The cyclopoid copepod Dioithona oculata forms dense swarms within shafts of sunlight that penetrate the mangrove prop-root habitat of islands off the coast of Belize. Previous studies, based on in situ video recordings and laboratory studies, have shown that D. oculata is capable of maintaining fixed-position swarms in spite of currents of up to 2 cm s⁻¹. The purpose of this study was to examine the energetic costs of maintaining these swarms, in terms of increased metabolic costs of maintaining position in currents and in terms of reduced feeding rates in densely packed swarms during the day. Using a sealed, variable-speed flow-through chamber, the respiration rates of D. oculata were measured while swarms maintained position in different current speeds. The results indicate that active metabolism (swimming at maximum speed to maintain the swarm in a current) is approximately three times greater than routine metabolism (normal swimming speeds in the absence of currents), indicating a significant metabolic cost of maintaining swarms in the presence of currents. In addition, gut-pigment analysis indicated that feeding rates of these copepods were often reduced in swarms during the day compared to when the copepods were dispersed at night. Given the high “cost” of swarming, the adaptive value of swarming in terms of reduced predation, increased opportunities for mating, and reduced dispersal, must be substantial. Received: 4 June 1997 / Accepted: 18 September 1997     

Spatial aggregations of the swarming jellyfish Pelagia noctiluca (Scyphozoa)

In the Adriatic Sea, the spatial distribution and aggregation aspects of swarning Pelagia noctiluca (Forskål, 1775) were studied by SCUBA divers from August 1984 to November 1985. Medusae were asually distributed in the upper 20- to 30-m layer. Dense aggregations caused by wind, currents and tidal phenomena occurred only in shallow coastal waters. Maximum population densities of swarms drifting freely near the shore were estimated at about 20 individuals per cubic meter, but when they had drifted ashore jellyfish could reach concentrations of 150 to 600 individuals in the same volume of sea water. Some peculiar forms of aggregations could be distinguished: couples, clusters, and surface and bottom aggregations. The effects of wind, currents and geomorphological features of the shore on passive aggregations of jellyfish are presented.     

Lack of kin recognition in swarming honeybees ( Apis mellifera )

Honeybee colonies reproduce by colony fission and swarming. The primary swarm leaves the nest with the mated mother queen. Further “after-swarms” can leave the nest. These are composed of virgin queens and sister workers. Since all workers in the primary swarm have the same relationship to the mother queen, kin recognition cannot have any effect on the worker distribution in the swarm. Because of polyandry of the mother queen, the after-swarm is composed of super- and halfsister workers of the virgin queen. In this case kin recognition might affect swarm composition if workers increase their inclusive fitness by preferentially investing in a supersister queen. The distribution of workers in the mother colony, the primary and the after-swarm was analyzed using single-locus DNA fingerprinting in two colonies of the honeybee (Apis mellifera). The colonies were composed of 21 and 24 worker subfamilies because of multiple mating of the queen. The subfamily distribution in the mother colonies before swarming was significantly different from the subfamily frequencies in the primary swarm. This indicates different propensities for swarming in the various subfamilies. The subfamily distribution was also significantly different between the mother colony and the after-swarm. There was however no significant difference between the subfamily composition of the primary and the after-swarm. The average effects of kin recognition on the distribution of the subfamilies in the two after-swarms were less than 2%. We conclude that colony-level selection sets the evolutionary framework for swarming behaviour. Received: 22 May 1996 / Accepted after revision: 2 November 1996     

Cysteine-glutathione disulfide, the sperm-release pheromone of the marine polychaete Nereis succinea (Annelida: Polychaeta)

Summary. In the marine polychaete Nereis succinea (Frey & Leuckart 1847) a sex pheromone was isolated from the coelomic fluid of sexually mature females and identified by NMR studies and independent synthesis. This pheromone is released by the females during reproduction together with eggs and coelomic fluid into the free water column and induces sperm release of surrounding males. Its structure was ascertained as L-cysteine-glutathione disulfide. It exhibited a response threshold of 0.6 · 10⁻⁷ M. Received 15 July 1997; accepted 25 November 1997.     

Estimate of removal rate ofNereis virens (Polychaeta: Nereidae) from an intertidal mudflat by gulls (Larus spp.)

The feeding behavior of herring gulls (Larus argentatus), ringed-billed gulls (L. delawarensis) and great blackbacked gulls (L. marinus) on an intertidal mudflat in Maine, USA, was investigated. Remains of fish, mussels, crabs, insects, and the polychaeteNereis virens were recovered from gull feces. Forty-three percent of the fecal samples containedN. virens jaws, setae, or both. A comparison of jaws from fecal material and from worms collected from the natural community demonstrates that gulls preferentially preyed upon larger worms. Feeding was largely confined to 3 h around low tide, and birds fed mostly in the low intertidal and below mean low water where the largest worms were located. Individual birds remained on the flat for a mean of 28.0 min and consumed a mean of 19.2 worms per visit. It was calculated that gulls remove a mean of 808 largeN. virens from the flat per tide from June to October, representing an estimated 0.04% of the standing crop of largeN. virens.     

Kin structure and the swarming behavior of the honey bee Apis mellifera

Summary Experimental hives obtained from cordovan queens that were instrumentally inseminated with semen from one cordovan and one Italian drone were set up and allowed to swarm. Cordovan provides a resessive genetic marker system (cuticle color) so that the workers from the cordovan and Italian male lines are distinguishable. Our results show that these patrilineal worker groups segregate non-randomly during colony fission and this segregation cannot be explained by observed age structure. Evidence of innate kin recognition in bees has been previously established. We argue that kin recognition could be responsible for the observed non-random grouping of kin during swarming.     

A first record of daytime surface swarming by Euphausia lucens in the Southern Benguela region

On 9 October, 1985 a daytime surface swarm of the euphausiid Euphausia lucens was observed and sampled in St. Helena Bay in the Southern Benguela region. The swarm was monospecific, consisted of adults in prebreeding condition and appeared to be feeding on detrital material. The swarm covered an estimated 46 ha, densities within it ranged between 4 000 and 1 500 000 individuals per cubic metre and the swarm was estimated to contain 5 000 tonnes of euphausiids. No simple explanation for the presence of the swarm was apparent.     

Why insects swarm: testing the models for lek mating systems on swarming Empis borealis females

Summary Female dance-flies, Empis borealis L., gather to swarm, and males carrying nuptial gifts visit swarms for mating. Field observations and experiments were performed on this behaviorally sex-role reversed species to test models of lekking behavior. The key predictions were: (1) female preference model: male visiting rate and mating rate should increase with the number of females in swarm (swarm size), (2) hotspot model: male visiting rate should be independent of swarm size, and (3) hotshot model: swarm size should be positively correlated with the body size of the largest female in swarm. We found that male visiting rate and mating rate increased with swarm size, and that mating rate per female increased with swarm size. Males also mated more often in larger swarms than in smaller ones. Both males and females visited swarm sites even in the absence of other individuals. When females were successively removed from swarm sites more males than females on average arrived at these sites: 2.25 males per female. When no individuals were present at the swarm site, arriving males moved on to another site, whereas arriving females generally stayed. Larger experimental swarm-markers attracted both more males and more females and even more males when swarming females were present. There was no correlation between mean or median female size in swarms and the number of females in swarms. Thus, the female preference model and the hotspot model were corroborated, while other models were judged unlikely to explain swarming behavior in E. borealis. Correspondence to: B.G. Svensson     

Laboratory method of analysis of swarming behaviour in macroplankton: combination of a modified flume tank and stereophotographic techniques

This paper describes a flume tank in which the various physical and behavioural conditions encountered by swarming macroplankton can be manipulated, and a mathematical stereophotographic technique, for use in the calculation of the three-dimensional co-ordinates of individual organisms within the swarms. The mathematical model incorporates the Direct-Linear Transformation equation which describes the position of the object and its image in relation to the camera-perspective centre of the photographic system. Combining this equation with a modified light-ray tracement technique to solve for the passage of light through a three-media environment, the actual three-dimensional co-ordinates of the individual organisms and subsequently their inter-individual distances, bearings and angles of elevation may be derived. The distances between adjacent animals can be measured to an accuracy of 0.24 mm (SD=0.21) using this photogrammetric technique. The design of the flume tank allows for the manipulation of water current speed and flow patterns, substrate, and light intensity. Six species of mysid and one species of euphausiid have been induced to swarm in the flume tank. The conditions required to induce swarming and schooling in the laboratory are described. The inter-individual distances, bearings and angles of elevation have been calculated for Paramesopodopsis rufa, Anisomysis mixta australis, Australerythrops paradicei (Crustacea: Mysidacea) and Nyctiphanes australis (Crustacea: Euphausiacea) using the stereophotographic technique.     

Daytime surface swarming of Euphausia pacifica (Crustacea: Euphausiacea) in the Sanriku coastal waters of northeastern Japan

Biological characteristics of daytime surface swarming of Euphausia pacifica were investigated. Swarms in the Sanriku coastal waters consisted almost exclusively of mature individuals and seemed to be related to breeding behavior. Although maturation of ovarian eggs occurred both at the beginning and the end of the swarming period, females with attached spermatophore were most frequent at the end of the period. Since stomachs of swarming individuals were nearly empty throughout this period, swarming behavior was probably not related to feeding. Swarming individuals did not seem to be transported to the surface by vertical water movement caused by tidal streams, because the daily catch per boat did not differ between spring and neap tides.     

唐鱼卵黄蛋白原的诱导、纯化与鉴定

为探讨利用雄性唐鱼(Tanichthys albonubes)卵黄蛋白原(Vitellogenin,Vtg)作为生物标志物检测环境雌激素的可行性,采用浸浴法用50μg·L-117β-雌二醇(E2)对雄性唐鱼进行染毒,30d后将鱼体整体匀浆进行常规聚丙烯酰胺凝胶电泳(Native-PAGE)以分析Vtg的产生;并采用Mg2+-EDTA选择性沉淀和Q Sepharose阴离子交换层析对Vtg进行分离纯化.结果表明,E2诱导下,雄性唐鱼产生了雌性特异蛋白Vtg,并且可在体内积累;利用Mg2+-EDTA选择性沉淀和Q Sepharose阴离子交换层析的两步纯化方法可分离纯化唐鱼整体匀浆Vtg;经Native-PAGE鉴定,确定唐鱼Vtg的分子量为440kDa.以上结果提示,雄性唐鱼Vtg可以作为环境雌激素监测的有效生物学标记物。     

杂草对不同水稻品种化感作用的诱导效应

以高脚子粳稻、DV86、HG1和扬稻6号4个水稻品种和稗草、异型莎草、鸭舌草为材料，研究了不同水稻品种单栽或与杂草共栽时，水稻叶片水浸提液对稻田主要杂草稗草的化感作用。结果表明：在正常单栽条件下，高脚子粳稻抗稗草的化感潜力显著大于：HG1和DV86，三者的化感潜力均显著大于非化感品种扬稻6号。不同水稻品种与杂草共栽时，其化感作用均由不同程度的变化，HG1在与稗草共栽时，对稗草幼苗的生长抑制作用显著大于高脚子粳稻；DV86在与鸭舌草共栽时，对稗草幼苗的生长抑制最强。研究表明不同杂草对不同水稻品种的杂草化感作用的诱导效应存在显著差异。     

光周期对油桃芽休眠诱导及呼吸代谢的影响

以‘曙光’(Prunus persica var.nectariana cv.Shuguang)油桃为试材,研究光周期对油桃芽休眠诱导进程以及对芽内底物水平的呼吸代谢运行的影响.结果表明:短日照使油桃芽提前进入休眠诱导,并促进休眠迅速加深,而长日照使休眠延迟.整个休眠诱导期内,叶芽和花芽的总呼吸速率先升高后降低.在底物水平上,随着休眠诱导的进行,三羧酸循环(TCA)略有下降,但仍维持高位运行,磷酸戊糖途径(PPP)在总呼吸中比例持续上升.短日照诱导相关的呼吸代谢变化提前出现,而长日照对相关呼吸代谢的变化具有推迟作用.     

Induction of trypsinogen secretion in herring larvae (Clupea harengus)

Mechanisms initiating trypsinogen secretion were studied in laboratory reared herring larvae (Clupea harengus L.) exposed to physical and chemical stimuli. Pancreatic secretion of trypsinogen was quantified for each stimulus type as the increase above pre-stimulus level of intestinal trypsin content. Larval prey types were: nauplii, copepodites or adult Acartia tonsa, small polystyrene spheres (diameter 94 m), small (diameter 79 m) or large (diameter 170 m) polystyrene-latex spheres. Intestinal trypsin content can be expressed as a function of two variables: meal size and content of pancreatic trypsinogen. Trypsinogen secretion increases with different prey items in the order: small spheres, nauplii and copepodites. Larvae which eat large spheres secrete more enzyme than if fed small spheres but trypsinogen secretion is similar in fish larvae fed copepodites and large spheres. The fact that the size of non-biodegradable particles exerts a major control over trypsinogen secretion suggests neural — as opposed to chemically mediated — initiation of secretion. A cephalic phase of secretory stimulation could not be demonstrated during swallowing of copepods or exposure for 2 to 3 h to compounds which leak from live copepodites. As cephalic and gastric phases of secretory stimulation are absent, initiation of trypsinogen secretion must take place in the intestine. Larval herring retain trypsin in the intestine. Ca. 4.5 h after a meal, 3/4 of the enzyme is located in the intestinal fluid, presumably available for hydrolysis of subsequent meals, and the high proportion (ca. 25%) of the pancreatic trypsinogen content which is secreted for copepodite prey may thus not be energetically wasteful for the larvae.     

Induction of metamorphosis of two species of sea urchin from Sea of Japan

The induction of metamorphosis in mature larvae by selected chemical compounds and natural substrata was investigated in two species of sea urchins from the Sea of Japan, Strongylocentrotus intermedius and Scaphechinus mirabilis. Glutamine in crystalline form was added directly to water containing mature larvae, and this compound, at a final concentration of 10 g ml^-1, was an inducer of metamorphosis in S. intermedius (100% activity) and S. mirabilis (50% activity). Gutamine, or its natural mimetic molecules, may be an active component of the exogenous cue that induces metamorphosis of S. intermedius larvae. This exogenous cue was produced by the epiphytic calcareous algae, Melobesia spp. that colonized the older sea grass Zostera marina. Glutamic acid was also used as an inducer of metamorphosis for S. intermedius and S. mirabilis larvae (50 to 60% activity), but it was toxic to the larvae.     

Induction and reversion of multixenobiotic resistance in the marine snail Monodonta turbinata

Many marine organisms inherently express the presence and function of a new defence mechanism, termed multixenobiotic resistance mechanism (MXRM) because of its similarity to multidrug resistance (MDR) found in tumor cell lines resistant to chemotherapeutic drugs. However, previously no information was available on a possible induction of the activity of MXRM in organisms living at polluted sites. The purpose of the present study was to demonstrate the inducibility of this defence mechanism in the marine snail Monodonta turbinata, an organism known to inhabit a wide range of environmental conditions existing along a pollution gradient. Specimens of M. turbinata used in the present study were collected from March 1993 through March 1994 near Rovinj, Croatia. The accumulation of generally labelled ³H-vincristine (³H-VCR) in the gills of snails living at an unpolluted site was 67% higher and very sensitive to verapamil, an inhibitor of P-glycoprotein activity in comparison to snails living at a polluted site. The accumulation of vincristine (VCR) in snails from a polluted site was reduced and insensitive to verapamil due to the induced state of P-glycoprotein, as was demonstrated immunochemically by the enhanced concentration of a 140 kDa protein cross-reacting with the polyclonal antibodies raised against mammalian P-glycoprotein. MXRM could be induced in snails from the unpolluted site to the level found in snails living at a polluted site either by transplantation for 3 d to a polluted site, or by exposure for 3 d to sea water polluted with Diesel-2 oil (hydrocarbon concentration equivalent to 50 ppb of Kuwait oil). Discovery of the inducibility of this new defence mechanism in aquatic organisms may have important implications in ecotoxicology, as was demonstrated by a 104% enhanced accumulation of VCR in the presence of the MXRM-inhibitor, the so-called chemosensitizer. Besides, a striking difference in the levels of MXRM-elements (the sensitivity of the accumulation rate of xenobiotics to verapamil, immunochemical expression of P-glycoprotein, and the sensitivity of the binding of xenobiotics on membrane vesicles to verapamil) found between specimens living at the polluted and unpolluted sites offers a new molecular biomarker for exposure to pollutants.