Group size structure affects patterns of aggression in larval salamanders

The potential importance of intrapopulation phenotypic variabilityto population-level ecology has been demonstrated in both theoreticaland field studies. One way to connect individuals to the dynamicsof populations they compose is to study behavioral response(an individual-level characteristic) to variability in conspecificphenotypes (a population-level characteristic). We examinedeffects of variation in size of individuals on patterns of aggressionin larval tiger salamanders (Ambystoma tigrinum nebulosum) byobserving aggressive behavior in groups of three larvae in alaboratory experment. We assessed effects of variability insize of conspecifics independently of mean larval size and larvaldensity Overall levels of aggression were generally higher ingroups in which all individuals were similprly sized than ingroups of variably sized individuals. Medium-sized individualsexhibited significantly higher levels of aggression and wereattacked significantly more often when in groups consistingonly of similarly sized larvae as compared to groups composedof larvae representing a wider range of body sizes. Activitylevels of larvae were also generally lower when all individualswere the same size, resulting in a negative correlation betweenactivity and levels of iggressititi. These results suggest thatgioups of similarly sized individuals experience a more aggressivesocial environment than groups of variably sized individuals,and they suggest a promising avenue of research for connectingindividual behavioral and physiological responses to size structure(phenotypic variability) with population dynamics.     

Review of the population structure and ecology of S. mentella in the Irminger sea and adjacent waters

Significant controversies exist over the three types of Sebastes mentella found in the Irminger Sea and adjacent waters. Preliminary genetic studies have given evidence for the existence of three distinct groups, characterized using several molecular genetic markers. The biological or ecological significance of these between-group differences has, however, not been evaluated. In the present paper, we review the life cycle of S. mentella in this area, based on published data. Spawning of S. mentella in the Irminger Sea takes place in a single area above Reykjanes Ridge. The larvae drift towards East Greenland from where they are carried to West Greenland (NAFO Subareas 0+1). Later they return to East Greenland where the main nursery area has been identified. There is evidence for a migration of juvenile fish from the nursery area into the open Irminger Sea, where many different cohorts spawn. We also compare these ecological data with the genetic results and we conclude that the observed genetic differences can be derived from possible genetic drift, selection or mostly from temporal variation (age dependency). which has also been reported for other species with as high longevity as S. mentella. We conclude that S. mentella in the Irminger Sea and adjacent waters comprises one single population.     

The senses of sea anemones: responses of the SS1 nerve net to chemical and mechanical stimuli

The ectodermal slow system (SS1) is one of 3 separate nerve nets in sea anemones. SS1 sensory responses coordinate swimming in Stomphia coccinea (escape response) and expansion to dissolved food substances in Urticina felina (pre-feeding response). Here we have studied Actinia equina, Anemonia viridis, and Anthopleura ballii. Although these anemones can escape from nudibranch predators, the SS1 response to attack by Aeolidia papillosa is probably evoked mechanically rather than chemically (cf. Stomphia). Multiple SS1 pulses to mechanical stimulation are described for the first time. Previous work has shown that in the pre-feeding response of Urticina the SS1 is excited by betaine; in Actinia however, the excitant is proline. The anemones studied can utilize the SS1 in 2 different behavioural responses (escape and pre-feeding/feeding) because the different receptors involved respond at different frequencies (at around 0.6 Hz in escape and 0.2 Hz in pre-feeding).     

Primary Structures of Actinoporins from Sea Anemone <Emphasis Type="Italic">Oulactis orientalis</Emphasis>

Partial amino acid sequences of the actinoporins Or-A (136 aa) and Or-G (144 aa) isolated from the Sea of Japan sea anemone Oulactis orientalis were determined by sequencing the clones obtained by the amplification of genomic DNA and cDNA with primers specific to the N-terminal regions of the O. orientalis actinoporin sequences and to the C-terminal region, which is highly conservative in all the known actinoporin sequences. The complete structures of Or-A (165 aa) and Or-G (173 aa) were elucidated by sequencing the cDNA clones obtained by the rapid amplification of 3′-ends of cDNA. A comparative analysis of the amino acid sequences of the Oulactis actinoporins with those of actinoporins from tropical species revealed considerable differences in the structures of their N-terminal fragments and their membrane-binding sites. We believe that these differences could explain the lower hemolytic activities of Or-A and Or-G compared to those of actinoporins from the tropical species.__________Translated from Bioorganicheskaya Khimiya, Vol. 31, No. 4, 2005, pp. 357–362.Original Russian Text Copyright © 2005 by Il’ina, Monastyrnaya, Isaeva, Guzev, Rasskazov, Kozlovskaya     

Host Imprinting in Anemonefishes (Pisces: Pomacentridae): Does it Dictate Spawning site Preferences?

The olfactory cues, to which some species of anemonefish embryos imprint, are secreted in the mucus on the tentacles and the oral disc of the host anemone. Close contact of the eggs of anemonefishes with the host's tentacles seems therefore important to imprinting. A corollary of this observation is that if local environmental conditions sweep tentacles in one specific direction, then the eggs will be placed leeward of the tentacles, rather than to foremost way from the tentacles. Other known factors such as egg predation can also cause a spawning site preference. No study has examined the possibility of the existence of such a preference. In this study, we addressed two questions: (1) Does spawning site preference exist in anemonefishes? (2) If yes, is it possible to relate this to the imprinting hypothesis, i.e. does local ocean currents over the host anemone have any influence on this preference? Two different coral reef areas were surveyed for anemonefish groups with eggs present: Eilat and Na'ama in the Aquaba-bight, the Red Sea (RS), and areas at Lizard Island, the northern Great Barrier Reef (GBR). We found the anemonefishes Amphiprion akindynos (GBR), A. bicinctus (RS), A. melanopus (GBR), and A. perideraion (GBR), to have a distinctive spawning site preference. We discuss the relevance of these findings to anemonefish host imprinting.     

Adaptive bleaching: a general phenomenon

Laboratory and field data bearing on the adaptive bleaching hypothesis (ABH) are largely consistent with it; no data of which we are aware refute it. We generalize the ABH in light of these data and observations. The population of zooxanthellae within an organism is dynamic, the diversity of zooxanthellae is both surprising and difficult to ascertain, and field experiments demonstrate both turn-over in zooxanthella types and habitat-holobiont correlations. Dynamic change in symbiont communities, and the idea of an equilibrium or optimal community that matches the environment at a particular place and time, are concepts that underlie or emerge from much of the recent literature. The mechanism we proposed to explain responses to acute bleaching appears to operate continuously, thereby enabling the host-symbiont holobiont to track even subtle environmental changes and respond promptly to them. These findings enhance the potential importance of the ABH in the outcomes of acute bleaching, which can (1) accelerate this process of holobiont change, and (2) change the set of possible trajectories for how symbiont communities might recover.     

Nematocysts of sea anemones (Actiniaria,Ceriantharia and Corallimorpharia: Cnidaria): nomenclature

A brief historical review of nematocyst terminology is given and three nomenclatural problems are discussed. It is proposed to combine the terms initiated by Weill (1934) with those of Schmidt (1969). A new mesobasic grade, intermediate between microbasic and macrobasic is proposed for amastigophores and p-mastigophores possessing a short Faltstück. A more liberal interpretation of Weill's (1934) terminology for nematocysts than that proposed by Cutress (1955) is suggested in respect of microbasic amastigophores and p-mastigophores. Basitrichs and b-mastigophores continue to be recognized as separate categories.deceased     

Life histories ofNeomysis integer,and its copepod prey,Eurytemora affinis,in a eutrophic and brackish shallow lake

Data was collected on the population structure and fecundity of the mysidNeomysis integer and the calanoid copepodEurytemora affinis in Hickling Broad, a shallow and eutrophic brackish lake, over a two-year period 1988/89. Standing biomass and production rate estimates were made using estimates of size-specific dry weights and development times obtained from laboratory measurements, field observations and information found in the literature. Both mysid and copepod are capable of a rapid response to favourable conditions and have high rates of birth, growth and production.E. affinis reproduces throughout the year with an estimated annual (May 1988–May 1989) production of 20 g dry wt m⁻². Copepod standing biomass was less in 1989 compared with 1988 owing to an overall reduction in copepod body-size and a reduction of size at maturity. There was a suggestion from the data that this was caused by predation from a greater number of large (>9 mm body-length) mysids in 1989 compared with 1988.N. integer is highly seasonal in its growth with distinct peaks of recruitment in May and July. Annual (May 1988–May 1989) production of the mysid was estimated as 5.8 g dry wt m⁻². AlthoughE. affinis is the only available prey ofN. integer in the lake, the mysid population appears independent of changes in that of the copepod and probably avoids negative predator-prey feedback mechanisms owing to an ability to feed on epiphytic algae.     

Aggressive Interactions and Risk of Fish Predation for Larval Damselflies

Larval damselflies frequently engage in aggressive interactions that may increase their risk of fish predation. To test this we analyzed the behavior of larval Ischnura verticalis exposed to both conspecifics and fish predators. Larvae in the presence of conspecifics oriented, struck, and swam more but crawled less compared to solitary larvae; the presence of fish reduced, or tended to reduce, all behaviors. Fish struck more at interacting larvae compared to noninteracting larvae. Increased attack rate by fish likely reflects the increase in the very active swimming behavior by larvae and suggests a conflict between antipredator behaviors. Swimming is an appropriate response to avoid predation by odonate larvae which normally ambush prey but is clearly dangerous when fast-swimming fish that cue in on movement are nearby.     

Feeding Characteristics of Three Species of Intertidal Sea Anemones of the South Kuril Islands

We examined the content of the coelenteron of Oulactis orientalis, Cnidopus japonicus, and Aulactinia sp. (family Actiniidae) inhabiting the intertidal area of Shikotan and Kunashir Islands (South Kuril Islands). The feeding characteristics (food spectrum, the index of filling of the coelenteron, the index of food similarity of the species, occurrence frequency, the index of trophic importance, and the proportions of certain components in the food pellet) allowed us to determine that the examined species are euryphagous.     

盐度对红树植物海莲幼苗的生长和某些生理生态特性的影响

本文主要探讨了不同盐度海水砂培的海莲幼苗生长量和某些生理生态特性与盐度的相关效应。结果表明,生长基盐度20‰以上,海莲繁殖体的萌苗时间推迟,成活率降低;随着盐度的提高,幼苗高生长量降低,叶片变小;叶片叶绿素含量随盐度提高而提高,相反的叶片可溶性糖含量则降低,而叶片可溶性蛋白质含量变化不明显;叶片组织内氯含量随盐度提高而提高;随着盐度的提高,叶片蒸腾作用减弱,气孔导度降低。由此表明,海莲幼苗适宜生长的盐度范围在15‰以下,更高的盐度表现为生态抗盐适应性生长。     

河西走廊荒漠地区的人口和生态问题

甘肃省自然条件差,粮食自给程度低。在这一背景下,有着灌溉之利,粮食产量较高且稳定的河西走廊荒漠绿洲,便首当其冲地承受着生产更多商品粮的压力。由此必须扩大垦殖,增加用水以及由于人口增长而扩大樵采等对植被的破坏,加剧了沙漠化的发展和绿洲的衰退。本文拟对河西走廊荒漠地区的人口与生态环境问题及解决途径,做一概略讨论。     

La régulation osmotique et ionique chez Homarusgammarus (L.) (Crustacea: Decapoda)

In juveniles of Homarus gammarus (L.) reared at 15°C, mortality occurs only in salinities below 17%. and above 46%.. Regulation is isosmotic in high salinities, and slightly hyperosmotic in low salinities. Regulation of Cl^?, Na⁺, K⁺, Ca²⁺, and Mg²⁺ ions is described. Important similarities exist between these results and those obtained in H. americanus H. Milne Edwards.