Effects of climate warming on strobilation and ephyra production of North Sea scyphozoan jellyfish

Recent studies have correlated fluctuations in jellyfish abundances with climatic changes, leading to speculation that the warming trend in the North Sea will affect the strobilation activity of Scyphozoa. The present study provides long-term data (10–22 months) on temperature effects on the species Aurelia aurita, Cyanea capillata, Cyanea lamarckii and Chrysaora hysoscella. Strobilation at current winter temperature (5°C) in the German Bight was compared to strobilation at warmer winter temperatures. Simulated winter temperature of 10°C had several positive effects on strobilation, as compared to 5°C: 1. A longer strobilation period or higher ephyra production per polyp in A. aurita, C. lamarckii and Ch. hysoscella; 2. Higher percentages of polyps strobilating in A. aurita and Ch. hysoscella; 3. More ephyrae per strobila in C. capillata and C. lamarckii; 4. A shorter strobilation duration in C. capillata and C. lamarckii. Cold winter temperatures of 5°C promoted strobilation in C. capillata, but inhibited strobilation in A. aurita and reduced ephyra production in C. lamarckii and Ch. hysoscella. These results suggest that climate warming will benefit A. aurita, but not cold-water C. capillata. The distributions of C. lamarckii and Ch. hysoscella probably could expand to the north.     

Release and growth of Cyanea capillata (L.) ephyrae in the Gullmar Fjord,western Sweden

In an investigation carried out in the Gullmar Fjord, western Sweden, the autecology of the scyphozoans Aurelia aurita (L.) and Cyanea capillata (L.), has been studied. This paper focuses on results concerning C. capillata, but comparisons with Aurelia aurita are made and discussed. The main period of strobilation was in winter and early spring. The extent of ephyrae release was only one tenth of that of A. aurita. The period of rapid growth of ephyrae and medusae during the spring was delayed one month compared to the pattern for Aurelia. The Cyanea scyphistomae are exposed to predation by the nudibranch Coryphella verrucosa and only very limited settling of Cyanea planulae occurred in the area. Immigration from the North Sea is probably a major factor regulating the appearance of Cyanea capillata along the western coast of Sweden.     

Autecological investigations on marine diatoms. 4:Biddulphia aurita (Lyngb.) Brebisson et Godey—A succession of spring diatoms

Comparison of generation times ofBiddulphia aurita (Lyngb.) Brebisson and Godey with other diatoms indicated that the species can reach its best competitive position by growth from –1.5°C to about 6°C. The diatom demonstrates its optimum temperature at about 12°C. Yet, flowerings will occur at the lower temperatures only. Its presence in the early spring plankton is facilitated by its non-adhrence behaviour, that proved to be temperature dependent. At 0°C almost no adherence occurred, whereas at high temperaturesB. aurita adhered completely to the bottom of the glas vessels or pipettes. The importance ofB. aurita in the benthic community is discussed. The mutual differences in growth ofB. aurita, Chaetoceros debilis andThalassiosira nordenskioeldii resulted in a succession comparable with that found in nature.     

Capture and digestion of the scyphozoan jellyfish Aurelia aurita by Cyanea capillata and prey response to predator contact

Laboratory experiments, field observations and manipulativefield experiments were carried out in 1993 in Gullmarsfjorden(Sweden) to study the interactions between two common speciesof scyphozoan jellyfish. Cyanea capillata was a predator onAurelia aurita. Gut analyses on 70 specimens of C.capillatashowed no size dependency in the ability to catch     

Muscle and nerve net organization in stalked jellyfish (Medusozoa: Staurozoa)

Staurozoan cnidarians display an unusual combination of polyp and medusa characteristics and their morphology may be informative about the evolutionary origin of medusae. We studied neuromuscular morphology of two staurozoans, Haliclystus ‘sanjuanensis ’ and Manania handi , using whole mount immunohistochemistry with antibodies against FMRFamide and α‐tubulin to label neurons and phalloidin to label muscles. All muscles appeared to lack striations. Longitudinal interradial muscles are probable homologues of stalk muscles in scyphopolyps, but in adult staurozoans they are elaborated to inwardly flex marginal lobes of the calyx during prey capture; these muscles are pennate in M. handi . Manubrial perradial muscles, like the manubrium itself, are an innovation shared with pelagic medusae and manubrial interradial muscles are shared with scyphozoan ephyra. Marginal muscles of M. handi displayed occasional synchronous contraction reminiscent of a medusa swim pulse, but contractions were not repetitive. The nerve net in both species showed regional variation in density and orientation of neurons. Some areas labeled predominantly by α‐tubulin antibodies (exumbrellar epidermis), other areas labeled exclusively by FMRFamide antibodies (dense plexus of neurites surrounding the base of secondary tentacles, neuronal concentration at the base of transformed primary tentacles; gastrodermal nerve net), but most areas showed a mix of neurons labeled by these two antibodies and frequent co‐labeling of neurons. Transformed primary tentacles had a concentration of FMRFamide‐immunoreactive neurons at their base that was associated with a pigment spot in M. handi; this is consistent with their homology with rhopalia of medusae, which are also derived from primary tentacles. The muscular system of these staurozoans embodies characteristics of both scyphopolyps and pelagic medusae. However, their nerve net is more polyp‐like, although marginal concentrations of the net associated with primary and secondary tentacles may facilitate the richer behavioral repertoire of staurozoans relative to polyps of other medusozoans. J. Morphol. 278:29–49, 2017. ©© 2016 Wiley Periodicals,Inc.     

Cryptic diets of forage fish: jellyfish consumption observed in the Celtic Sea and western English Channel

To establish if fishes’ consumption of jellyfish changes through the year, we conducted a molecular gut-content assessment on opportunistically sampled species from the Celtic Sea in October and compared these with samples previously collected in February and March from the Irish Sea. Mackerel Scomber scombrus were found to feed on hydrozoan jellyfish relatively frequently in autumn, with rare consumption also detected in sardine Sardina pilchardus and sprat Sprattus sprattus. By October, moon jellyfish Aurelia aurita appeared to have escaped predation, potentially through somatic growth and the development of stinging tentacles. This is in contrast with sampling in February and March where A. aurita ephyrae were heavily preyed upon. No significant change in predation rate was observed in S. sprattus, but jellyfish predation by S. scombrus feeding in autumn was significantly higher than that seen during winter. This increase in consumption appears to be driven by the consumption of different, smaller jellyfish species than were targeted during the winter.     

Gill cell toxicity of northern boreal scyphomedusae <Emphasis Type="Italic">Cyanea</Emphasis> <Emphasis Type="Italic">capillata</Emphasis> and <Emphasis Type="Italic">Aurelia</Emphasis> <Emphasis Type="Italic">aurita</Emphasis> measured by an in vitro cell assay

Scyphozoan medusae are very successful foragers which occasionally occur in high abundances in boreal waters and may impact many different groups in the marine ecosystem by means of a variety of toxins. A rainbow trout gill cell line, RTgill-W1, was tested for its suitability as quantitative indicator of the cytotoxicity of Cyanea capillata and Aurelia aurita; the major scyphozoan species in the North and Baltic seas. Cultures of rainbow trout gill cells were exposed to whole venoms extracted from fishing tentacles and oral arms at increasing protein concentrations. The venom caused detachment, clumping and lysis of cells, as well as a drop in vitality, in a dose-dependent manner. Morphological changes in the cells were evident within 1 h after venom addition. The damage to gill cells was quantified by measuring the metabolic activity of the cells by means of the fluorescence of resorufin derived from the nonfluorescent substrate, resazurin. In general, a decrease in the metabolic activity of the cells was detected at a venom (protein) concentration above 2.0 μg ml⁻¹ (corresponding to 0.2 μg 10⁴ cells⁻¹), and a total loss of activity was observed above 40.0 μg ml⁻¹ (corresponding to 4.0 μg 10⁴ cells⁻¹). C. capillata venoms had increased cytotoxic activity as compared to A. aurita venoms at the same concentration. Cnidocyst extracts from oral arms of A. aurita induced an 85% loss of gill cell viability at concentrations of 0.2 μg 10⁴ cells⁻¹, whereas crude venoms from fishing tentacles reduced cell viability by 18% at the same concentration. Gel electrophoresis of the venoms indicated that these consist of a large number of proteins in a fairly wide size range, from 6 to 200 kDa, including some that are the same size as those found in cubomedusae. It also appears that larger (i.e., older) medusae have more complex venoms and, in some cases, more potent venoms than smaller animals.     

Temperature effects on asexual reproduction rates of scyphozoan species from the northwest Mediterranean Sea

In recent decades, many areas worldwide have experienced mass occurrences of jellyfish. To determine how temperature may affect jellyfish populations in the northwest (NW) Mediterranean Sea, we maintained polyps of three scyphozoan species, Aurelia aurita, Rhizostoma pulmo, and Cotylorhiza tuberculata in the laboratory at three temperatures (14, 21, 28°C) to test effects on survival and production of new polyps and ephyrae. Temperature significantly affected survival of all species, with longest survival of A. aurita and R. pulmo at 14°C and of C. tuberculata at 21°C. More polyps were budded by all species at temperatures above 14°C. A. aurita produced the most buds polyp⁻¹ (43.5) and R. pulmo the fewest (8.8). Strobilation occurred only at 14°C for A. aurita and at 21°C for C. tuberculata. For R. pulmo, fewer polyps strobilated and strobilated later at 14°C. These patterns of survival and asexual reproduction were seasonally appropriate for each species in the NW Mediterranean, where A. aurita medusae occur earliest (~April–May) in cool waters, followed by R. pulmo during May–June, and then by C. tuberculata in mid-summer. Comparisons among scyphozoan species suggested that many may be restricted by low temperatures, and that global warming may benefit temperate species, but not tropical or boreal species.     

Reproduction and life history strategies of the common jellyfish, Aurelia aurita, in relation to its ambient environment

The scyphozoan Aurelia aurita (Linnaeus) is a cosmopolitan species, having been reported from a variety of coastal and shelf sea environments around the world. It has been extensively studied over the last 100 years or so, and examination of the literature reveals three striking features: (1) the presence of populations in a wide range of environmental conditions; (2) large inter-population differences in abundance and life history patterns over large and small spatial scales; and (3) inter-annual variability in various aspects of its population dynamics. A. aurita is clearly a highly flexible species that can adapt to a wide range of environmental conditions. While various physiological and behavioural characteristics explain how A. aurita populations can take advantage of their surrounding environment, they do not explain what governs the observed temporal and spatial patterns of abundance, and the longevity or lifespan of populations. Understanding these features is necessary to predict how bloom populations might form. In a given habitat, the distribution and abundance of benthic marine invertebrates have been found to be maintained by four factors: larval recruitment (sexual reproduction), migration, mortality and asexual reproduction. The aims of this review are to determine the role of reproduction and life history strategies of the benthic and pelagic phases of A. aurita in governing populations of medusae, with special attention given to the dynamic interaction between A. aurita and its surrounding physical and biological environment.     

Effects of low salinity on settlement and strobilation of scyphozoa (Cnidaria): Is the lion’s mane <Emphasis Type="Italic">Cyanea capillata</Emphasis> (L.) able to reproduce in the brackish Baltic Sea?

Several species of scyphozoan medusae occur in river estuaries and other brackish waters but it is often unknown if the planulae settle and the scyphopolyps reproduce in those low-salinity waters. In the present study, scyphozoan species from the German Bight (North Sea) were tested in laboratory experiments to investigate their tolerance of low salinity. Planula larvae released from medusae in salinity 32 were still active after the salinity was reduced to 10 (Cyanea capillata, Cyanea lamarckii) and to 7 (Chrysaora hysoscella) in laboratory treatments. Planulae did not settle on the undersides of floating substrates when salinity was reduced to <20. By contrast, planulae released from C. capillata medusae in Kiel Bight (western Baltic Sea) in salinity 15 developed into polyps in laboratory cultures. Polyps reared from planulae in salinity 36 survived a reduction to 12 (C. capillata, C. lamarckii) and to 8 (Aurelia aurita). Polyps of all tested species strobilated and released young medusae (ephyrae) in salinity 12. These results show a high tolerance of planulae and polyps to low salinity, indicating their possible occurrence in estuaries and brackish waters. In addition to laboratory observations, young C. capillata ephyrae were collected in the western Baltic Sea (Kiel Bight) in salinity 15, which indicates that they were probably released by a local polyp population. We suggest that the polyps of the painfully stinging lion’s mane, C. capillata, may be more widespread in the Baltic Sea than previously assumed and that the occurrence of the medusae may not only depend on inflow of water masses from the North Sea.     

Feeding behaviour of the grass grub Costelytra zealandica (White) (Coleoptera: Melolonthinae)

The feeding response of 3rd‐instar Costelytra zealandica larvae to 20 amino acids tested individually at 2 concentrations was assessed. Six of these compounds had a phagostimulatory effect; in particular, the ubiquitous amino acids L‐aspartic acid, L‐glutamic acid, and L‐serine induced considerable feeding by the grubs. Ascorbic acid was also a strong feeding stimulant and, in combination with sucrose, evoked an intense behavioural response. A synergistic effect of ‘Salt Mix W on the larval response to sucrose was demonstrated.     

Malate dehydrogenase and tetrazolium oxidase of scyphistomae ofAurelia aurita,Chrysaora quinquecirrha,andCyanea capillata (Scyphozoa: Semaeostomeae)

Summary 1. The malate dehydrogenase (MDH) isozyme patterns of the three most common polyps of Chesapeake Bay (USA) differ in number and in electrophoretic mobilities:Aurelia aurita: 4 bands (Rm=0.29, 0.33, 0.39, 0.43);Chrysaora quinquecirrha: 5 bands (Rm=0.21, 0.22, 0.40, 0.53, 0.54);Cyanea capillata: 1 band (Rm=0.50) or sometimes a second (Rm=0.25).2. The tetrazolium oxidase (TO) isozyme patterns differ as follows:Aurelia aurita: 2 bands (Rm=0.39, 0.51);Chrysaora quinquecirrha: 1 band (Rm=0.58);Cyanea capillata: 1 band (Rm=0.39).3. Isozyme components of MDH and TO, either singly or in combination, may be used to distinguish the common Chesapeake Bay polyps of unknown origin.

---

Malatdehydrogenase und Tetrazoliumoxydase der Scyphistomae vonAurelia aurita, Chrysaora quinquecirrha andCyanea capillata (Scyphozoa: Semaeostomeae)

Kurzfassung Im Gewebe der Scyphistomae vonAurelia aurita, Chrysaora quinquecirrha undCyanea capillata wurde das Isoenzymmuster der Malatdehydrogenase (MDH) und der Tetrazoliumoxydase (TO) durch Anwendung der Polyacrylamidgel-Elektrophorese bestimmt. Entsprechend der Reihenfolge der genannten Arten betrug die Anzahl der gefundenen MDH-Isoenzymbanden 4,5 bzw. 1, während sich die der TO-Isoenzymbanden auf 2,1 bzw. 1 belief. Es wird darauf hingewiesen, daß das Isoenzymmuster für die taxonomische Zuordnung der schwer zu unterscheidenden Scyphopolypen neben anderen Merkmalen mit herangezogen werden kann.

---

---

Contribution No. 547 from the Virginia Institute of Marine Science.     

Insecticidal potential of cashew (Anacardium occidentale L.) for control of the beetle,Callosobruchus subinnotatus (Pic.) (Bruchidae) on bambarra-groundnut (Voandzeia subterranea L.) Verde

Abstract

The nut and shell of cashew (Anacardium occidentale L.) were evaluated for insecticidal efficacy at concentrations of 2.5, 5.0 and 7.5% per 150 g bambarra groundnut (Voandzeia subterranea L.) Verde seeds against Callosobruchus subinnotatus (Pic.) (Bruchidae). Cashew nut shell was highly toxic to C. subinnotatus and achieved 100% insect mortality within 48 hours at 7.5% and 100% mortality within 72% hours at 2.5 and 5.0% concentrations. Oviposition and progeny development of the insect were severely suppressed while seeds were protected from damage by the bruchid. Seed germination was, however, impaired at all concentrations, suggesting that seed treated with cashew products may be suitable for consumption but not be suitable as planting stock.     

Hearing and evasive behaviour in the greater wax moth, Galleria mellonella (Pyralidae)

Greater wax moths (Galleria mellonella L., Pyraloidea) use ultrasound sensitive ears to detect clicking conspecifics and echolocating bats. Pyralid ears have four sensory cells, A_1?4. The audiogram of G. mellonella has best frequency at 60 kHz with a threshold around 47 dB sound pressure level. A₁ and A₂ have almost equal thresholds in contrast to noctuids and geometrids. A₃ responds at + 12 to + 16 dB relative to the A₁ threshold. The threshold data from the A‐cells give no indication of frequency discrimination in greater wax moths. Tethered greater wax moths respond to ultrasound with short‐latency cessation of flight at + 20 to + 25 dB relative to the A₁ threshold. The behavioural threshold curve parallels the audiogram, thus further corroborating the lack of frequency discrimination. Hence, the distinction between bats and conspecifics is probably based on temporal cues. At a constant duty cycle (percentage of time where sound is on) the pulse repetition rate has no effect on the threshold for flight cessation, but stimulus duration affects both sensory and behavioural thresholds. The maximum integration time is essentially the same: 45 ms for the A₁‐cell and 50–60 ms for the flight cessation response. However, the slopes of the time‐intensity trade‐off functions are very different: ? 2.1 dB per doubling of sound duration for the A₁‐cell threshold, and ? 7.2 dB per doubling of sound duration for the behavioural threshold. The significance of the results for sexual acoustic communication as well as for bat defence is discussed.     

A quantitative description of the behaviour of wild juvenile plaice (Pleuronectes platessa L.)

The behaviour of young plaice (Pleuronectes platessa L.) as they migrate up and down sandy beaches with the tide is described. Their behaviour during this migration consists mainly of swimming and feeding interspersed with rarer behavioural acts. Over short periods swimming behaviour can be described by a random model in which the probability of a swim occurring remains constant. This probability varies markedly, however, from hour to hour. Two types of swimming movement are recognized: one of very short duration represents searching for food and the other, longer, category serves to transport the fish up and down the shore. Variations in the feeding rate and in the frequency, duration, and direction of swimming movements over the tidal cycle are described and related to the changing physical and biological conditions that the fish experience during their intertidal movements.     

Sex roles in the ghost moth Hepialus humuli (L.) and a review of mating in the Hepialidae (Lepidoptera)

Recently it has been found that female Lepidoptera belonging to diverse families actively court their males, rather than play a merely passive role. Male and female Hepialus humuli have been reported to come together in three different ways: (1) females are attracted to groups or ‘leks’ of white, hovering males by visual stimuli; (2) females are attracted to the males by olfactory-substances produced on the hind-tibial brushes of the males; (3) males are attracted to sedentary females by olfactory stimuli. During my study I observed H. humili males flying on a total of 21 nights in two different parts of England. The males hovered in groups for about 20 min each evening, starting and stopping their flights in synchrony. Timing depended on light intensity, northern moths flying later in the summer evenings than southern moths. I observed a total of 18 matings. Normally, a female from outside a male lek flew into the group and up to one of the males. This male then usually followed her to a settling position, where mating took place. In a few cases females touched males; in one case a female struck a male in the air so that both fell to the ground and were copulating when examined. Photographs of hovering males show that their hind tibial brushes are fully everted in flight. The organs are folded against the body when the moth is mating, at rest or dead. Whilst hovering, the males are apparently emitting pheromones which function as primary attractants, rather than as the aphrodisiacs of many other lepidopteran males. The mating behaviour of hepialids is reviewed. It is concluded that all studied hepialids which have male brush organs (some Hepialus and Oncopera, Sthenopis, Zenophassus) exhibit similar flight and mating behaviour: males hover, sit or loop back and forth on the spot in leks; females fly into male aggregations and mate there (although some published observations suggest otherwise). In contrast, hepialids such as Fraus, Oxycanus and other Hepialus that lack male brush organs have mating behaviour in which the males are the active partner, a more standard lepidopteran method. In view of the controversies surrounding mating in hepialids, future systematic and behavioural work on Hepialidae throughout the world will be worthwhile.     

Extension of methods for jellyfish and ctenophore trophic ecology to large-scale research

Science has rapidly expanded its frontiers with new technologies in the 20th Century. Oceanography now is studied routinely by satellite. Predictive models are on global scales. At the same time, blooms of jellyfish and ctenophores have become problematic, especially after 1980. Although we have learned a great deal about gelatinous zooplankton ecology in the 20th Century on local scales, we generally have not scaled-up to estimate the extent, the causes, or effects of large blooms. In this age of global science, research on gelatinous zooplankton needs to utilize large-scale approaches and predictive equations. Some current techniques enable jellyfish populations (aerial, towed cameras), feeding (metabolic rates, stable isotopes), and dynamics (predictive modeling) to be studied over large spatial and temporal scales. I use examples of scyphomedusae (Aurelia spp., Cyanea capillata, Chrysaora quinquecirrha) and Mnemiopsis leidyi ctenophores, for which considerable data exist, to explore expanding from local to global scales of jellyfish trophic ecology. Regression analyses showed that feeding rates of Aurelia spp. (FR in copepods eaten medusa⁻¹ d⁻¹) generally could be estimated ±50% from in situ data on medusa wet weight (WW) and copepod density; temperature was not a significant factor. FR of C. capillata and C. quinquecirrha were similar to those of Aurelia spp.; the combined scyphomedusa regression underestimated measured FR of C. quinquecirrha and Aurelia spp. by 50% and 180%, respectively, and overestimated measured FR of C. capillata by 25%. Clearance rates (CR in liters cleared of copepods ctenophore⁻¹ d⁻¹) of M. leidyi were reduced in small containers (≤20 l), and a ratio of container-volume to ctenophore-volume of at least 2,500:1 is recommended for feeding experiments. Clearance rates were significantly related to ctenophore WW, but not to prey density or temperature, and estimated rates within 10–159%. Respiration rates of medusae and ctenophores were similar across habitats with greatly ambient different temperatures (10–30°C), and can be predicted from regressions using only mass. These regressions may permit estimation of feeding effects of gelatinous predators without exhaustive collection of feeding data in situ. I recommend that data on feeding and metabolism of jellyfish and ctenophores be entered in a database to allow generalized predictive relationships to be developed to promote inclusion of these important predators in ecosystem studies and models. Guest editors: K. A. Pitt & J. E. Purcell Jellyfish Blooms: Causes, Consequences, and Recent Advances     

Ultrastructure of the neuromuscular system of the polyp of Aurelia aurita L., 1758 (Cnidaria,scyphozoa)

Fine structural study indicates that the neuromuscular system of stage I polyps of Aurelia aurita is exclusively ectodermal. The three major muscle fields are the radial muscles of the oral disc, the longitudinal muscles of the tentacles, and the muscle cords of the septae and the column; the muscle fields are in physical continuity at the peristomial pits and share a common innervation and type of myofibril. The myofibril is striated in the tentacle base, in the outer oral disc, and in the upper part of the muscle cord; it grades into a smooth muscle toward the tentacle tip, the mouth, and the lower part of the cord. There is a fourth field of longitudinal smooth muscle in the pharynx. The nervous system consists of an epithelial sensory cell in the tentacle and a single type of neuron found in the subepithelial layer of the tentacle, oral disc, and muscle cord. The lack of gap junctions suggests that there is no nonnervous conduction system. The subepithelial layer also contains three types of fibers and a type of soma which cannot be characterized as neuronal. The soma is identified as the “neurosecretory cell” described in Chrysaora. The absence of neuromuscular elements in the column and stolon distinguishes the Aurelia aurita collected from Washington, USA, from English polyps previously described.     

Attraction of Aurelia and Aequorea to prey

Previously it has been assumed that medusae make random contact with their prey. Medusae were tested in a flow-through aquarium with inflow at each end and a central outflow. Aurelia aurita and Aequorea victoria were attracted to either end of the chamber if Artemia prey were present in a screened compartment. A. aurita was also shown to be attracted to water conditioned by Artemia, and to ammonium chloride added to one or other of the inflow currents.