Academic literature on the topic 'Siphonophore'

Three new species belonging to the family Resomiidae (Siphonophora: Physonectae) are described from material mainly collected by ROVs in the vicinity of Monterey Bay, California, USA, with some additional submersible-collected specimens from The Bahamas. Although these species,Resomia ornicephala,R. persica, andR. dunni, show some differences from those previously described, particularly in the shape of the nectophores, they have all been placed in the genusResomia. They retain the basic characteristic of having two forms of tentilla on the same tentacle, the more proximal form, with a spirally coiled cnidoband, becoming reconfigured into the more distal form, usually with a zigzagged cnidoband, although in one of the new species the zigzagging of the cnidoband is less well-defined.

Siphonophores are colonial hydrozoans that feed on zooplankton including fish larvae, and occur throughout the world's oceans from surface waters to ocean depths. Here we describe the composition of hyponeustonic siphonophores (0–3 m depth) from the tropical Colombian Pacific Ocean based on 131 plankton samples collected between June–October from 2001–2004. Samples were dominated by species of Calycophorae, with only three species of Physonectae identified, consistent with their deeper depth distribution. Muggiaea atlantica, Chelophyes contorta, Diphyes dispar, and Eudoxoides mitra were the most common of the 21 species identified. We found moderate structuring of the siphonophore community by the salinity gradient from inshore to offshore, and greater richness during the night because of diel vertical migration. Temperature did not play a significant role in structuring siphonophore communities, perhaps because of the narrow temperature range observed (3.5 °C). We extend the known temperature and salinity range of several species, including M. atlantica up to temperatures of 28.6 °C and salinities down to 24.7. Interestingly, only polygastric stages of M. atlantica were found, suggesting the reproductive stage of M. atlantica in tropical waters might be found in deeper waters. Chelophyes appendiculata was rare in our study and C. contorta was common, providing evidence they have a potential allopatric relationship, with C. contorta replacing C. appendiculata in warm water. Finally, we found siphonophore abundance was positively related to the abundance of copepods and fish eggs, with the top 13 most abundant species all having positive correlations, suggesting siphonophore abundances are tightly controlled by their food.

In his Challenger Monograph Haeckel (1888b) listed a total of 204 species of siphonophores and 36 species of Porpitidae (Disconectae, according to Haeckel), which are now known not to belong to the Siphonophorae. In this paper the siphonophore species have been divided into four categories: a). species that had been described previously by an acknowledged authority other than Haeckel; b). species where Haeckel changed the generic or specific name of a previously described species by another authority, and then ascribed the authority to himself; c). species that Haeckel actually described and illustrated as what he believed to be new; and d). species that Haeckel mentioned in the text as a new species, but with the description deferred to a later publication or simply not given. The validity of the forty-three species that Haeckel actually described is then discussed. A full list of all these species is given in an Appendix.

Siphonophores are one of the least known gelatinous zooplankters in the tropical waters of the Northwestern Atlantic. Most of the regional knowledge about their diversity and distribution is based on surface samples (0–200 m). Siphonophores were collected from oceanic waters off the Mexican Caribbean across an expanded sampling range (0–940 m) during two cruises and were taxonomically examined. A total of 47 siphonophore species were recorded, of these, 14 had not been found in this sector of the Caribbean Sea and 10 represent new records for the Caribbean Basin. The number of species currently known from the western Caribbean is increased from 42 to 56. Some of these species also represent new records for the Northwestern Tropical Atlantic region. The greatest relative increase was observed among species of Lensia, five of which are exclusively deep-living forms dwelling below 300 m. A revised, expanded checklist of the siphonophores of the Western Caribbean is also provided. These results confirm the need of further deep sampling to increase our understanding of Caribbean siphonophore diversity.

The spatial patterns of siphonophores were analysed in relation to local hydrographic features during two different monsoon seasons (the north-easterly monsoon in winter v. the south-westerly monsoon in summer) in the Taiwan Strait. Forty-eight species were identified, with five types of calycophoran siphonophores (Lensia subtiloides, Chelophyes appendiculata, Chelophyes contorta, Bassia bassensis, and Diphyes chamissonis) being most common in both seasons. Significantly higher abundances of four of the five common species were recorded in summer than in winter. Differences in the siphonophore species compositions were also observed between the northern and southern part of Taiwan Strait, with significantly higher diversity occurring in the southern waters. The distribution patterns of siphonophore assemblages were closely linked to the hydrographic features, influenced by the dynamic nature of the currents in the study area, with temperature, salinity and zooplankton biomass being the three most important factors.

Predator specialization has often been considered an evolutionary “dead end” due to the constraints associated with the evolution of morphological and functional optimizations throughout the organism. However, in some predators, these changes are localized in separate structures dedicated to prey capture. One of the most extreme cases of this modularity can be observed in siphonophores, a clade of pelagic colonial cnidarians that use tentilla (tentacle side branches armed with nematocysts) exclusively for prey capture. Here we study how siphonophore specialists and generalists evolve, and what morphological changes are associated with these transitions. To answer these questions, we: a) Measured 29 morphological characters of tentacles from 45 siphonophore species, b) mapped these data to a phylogenetic tree, and c) analyzed the evolutionary associations between morphological characters and prey-type data from the literature. Instead of a dead end, we found that siphonophore specialists can evolve into generalists, and that specialists on one prey type have directly evolved into specialists on other prey types. Our results show that siphonophore tentillum morphology has strong evolutionary associations with prey type, and suggest that shifts between prey types are linked to shifts in the morphology, mode of evolution, and evolutionary correlations of tentilla and their nematocysts. The evolutionary history of siphonophore specialization helps build a broader perspective on predatory niche diversification via morphological innovation and evolution. These findings contribute to understanding how specialization and morphological evolution have shaped present-day food webs.

This updated re-description of the prayine siphonophore Rosacea cymbiformis includes figures of all zooids (except larval nectophores) and is based on material held in the collections of the Natural History Museum (NHM), London. Rosacea cymbiformis was originally described in 1830 under the name Physalia cymbiformis, and subsequently reported many times during the 19th Century. However, during the 20th Century it was confused with the closely related species R. plicata, and the two species are still not clearly differentiated. Previous descriptions are reviewed herein, including conflicting interpretations of nectophore designation in R. plicata, and bract orientation in R. cymbiformis and R. plicata. To identify these siphonophores to species level and separate them from other closely related prayines, it is essential to distinguish the first definitive nectophore from the second, and the right paired bracteal canals from the left canals. This becomes critical when only detached siphonophore zooids are available, as for example, in plankton samples collected with nets. A summary of the differences between R. cymbiformi and the five other currently recognized Rosacea species, R. plicata, R. repanda, R. limbata, R. flaccida and R. arabiana, is presented. The full synonymy of R. cymbiformis is too long for inclusion here and is deferred to a later paper.

Amphipods of the genus Phronima are known to make a barrel-shaped house from the gelatinous matrix of pelagic tunicates or siphonophores. Among the seven barrels examined here, one barrel of Phronima curvipes was supposed to be made from a swimming bell of a siphonophore based on its morphology, while the other six barrels made by P. sedentaria were immunochemically and/or morphologically identified as tunicates (i.e. Thetys vagina, other salps and pyrosomas). Histological observation showed that the phronimids had completely eaten the animal tissues other than the gelatinous matrix (i.e. tunic or mesoglea). Tunic cells were found in the tunicate barrel and some were probably tunic phagocytes that appeared to be alive and functional. In the tunicate barrels, cuticular layers of the tunic were found on both the outer and inner side of the barrel wall. Tunic cuticle would be regenerated on the inner side after the epidermis was grazed by the phronimids. The cuticular layers would protect the tunic matrix from the invasion of microorganisms. In the barrel supposed to originate from Thetys vagina, there are minute protrusions on the tunic cuticle as found in the intact tunic of this species. In the barrel from a siphonophore, neither cells nor cuticle regeneration were found. No bacteria were observed in the barrel, suggesting that the barrel has some antibiotic system.

Effective locomotion and maneuvering in aquatic environments is important for survival for marine fauna. The ability to move quickly, change direction, and tune energy consumption for long migrations is critical for escape from predators and pursuit of prey. This controlled propulsion in terms of varying speed, turning rates, and actuation effort is of interest for the next generation of underwater vehicle design. Integration of biological functional simplicity, robustness, and superior performance enables robotic vehicles to successfully complete difficult and dynamic operational goals. Gelatinous animals known as Cnidarians employ a wide variety of propulsive methods, ranging from the simple but efficient propulsion of large jellyfish to the rapid and highly maneuverable multi-jet propulsion of colonial animals known as siphonophores. This dissertation studies how these two extremes of underwater soft body propulsion are able to achieve simple yet effective control and locomotion, and thus inform the design of effective vehicle propulsion control and actuation. Two large single bell jellyfish robots, Cyro 2 and Cyro 3, were designed and constructed to implement the simple body form and propulsive methods of large jellyfish to study the unique locomotive characteristics and fluid interactions that generate straight swimming and turning maneuvers. The other extreme of small soft-body colonies moving by multi-jet propulsion was subsequently investigated in-depth, starting with a characterization of the biological fluid jetting actions and gaits. The results of these performance capabilities were then applied to an experimental robotic model with bio-inspired construction and controls to verify an elegant but highly functional neurological control scheme and the kinematic capabilities from varying jetting gait patterns.
PHD

In many regions of the world the abundance and distribution of jellyfish is increasing. These changes have important consequences for marine ecosystems and the services that they provide to humans. It is a fundamental goal of marine ecologists to develop understanding of how jellyfish populations respond to environmental change. Two key processes are involved in the regulation of jellyfish populations: local demographics (i.e. production and mortality) and dispersal (i.e. immigration and emigration). A failure to discriminate between the contributions of these two fundamental processes can obscure the specific environmental factors that drive changes in jellyfish populations, impeding understanding. This thesis aims (1) to assess recent changes in the abundance and distribution of Muggiaea atlantica in the coastal waters of the United Kingdom; and to (2) investigate the influence of environmental variability on both the biological (i.e. demography) and physical (i.e. dispersal) processes that drive these changes. This study utilised data collected from a network of coastal monitoring stations, together with data on a range of local and regional hydroclimatic environmental factors. I show that since the late 1960s, there has been a progressive northward extension of this species’ distribution from its centre of population in the Bay of Biscay and Iberian Coast region. These changes involved the establishment of a resident population in the Western English Channel (WEC) and the subsequent development of transient seasonal populations on the east and west coasts of Scotland. In the WEC the M. atlantica population was capable of overwintering, sustaining a resident population irrespective of immigration. This population was modulated primarily by the availability of suitable local environmental conditions that influenced demography (temperature and food availability) and secondarily by changes to water circulation patterns that influenced its dispersal. In contrast, in Scotland M. atlantica was incapable of overwintering and its population was primarily modulated by immigration and secondarily by the availability of suitable local environmental conditions. On the west coast of Scotland, the European Slope Current (ESC) was identified as the source of immigration, whereas on the east coast the mechanism of immigration was not identified. Despite the importance of the ESC as a transport mechanism from the WEC region, a direct source-sink relationship between the WEC and Scottish coastal waters was not clearly demonstrated, suggesting the importance of a network of sources. Key environmental requirements for local M. atlantica production were consistent between the localities, these were: a critical limit of 10 °C for reproduction, with an optimum of 13–15°C, together with the availability of small copepod prey. Changes in the timing of this critical temperate modulated trophic phasing with copepod prey, influencing the phenology of the blooms of M. atlantica. This thesis provides the basis for developing a mechanistic understanding of the factors that modulate distribution in a species of jellyfish. The principles and methods used could be applied to better understand changes in the abundance and distribution of M. atlantica in other areas, and also for different species of jellyfish.

Orientador: Prof. Dr. Otto Müller Patrão de Oliveira
Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Evolução e Diversidade, 2016.
Os sifonóforos são um grupo de hidrozoários (Cnidaria: Medusozoa) de grande importancia no ambiente pelagial marinho. Apesar disso, estudos sobre a sistemática desses organismos são escassos na literatura. Pouco se sabe sobre as relações filogenéticas entre os táxons superiores do grupo, e pouco progresso foi feito até o momento para o gênero Lensia. O presente estudo teve como objetivos realizar uma minuciosa análise morfológica do nectóforo anterior dos diferentes morfotipos do gênero Lensia, provenientes de duas campanhas oceanográficas, e realizar a análise filogenética desses morfotipos, com base nos dados morfológicos obtidos. O material analisado foi proveniente de duas campanhas oceanográficas (FINEP III e Projeto Habitats), realizadas ao longo da costa sudeste do Brasil. Ao todo foram analisados 61 espécimes e foram identificadas 15espécies de Lensia. Os espécimes foram fotografados com um estereomicroscópio com camera digital acoplada. Em seguida, foram identificados, descritos, esquematizados e medidos. Foi elaborada uma chave de identificação das espécies analisadas. Foram listados 22 caracteres do nectóforo anterior de Lensia, que foram codificados em uma matriz de dados. Foram utilizadas duas espécies do gênero Diphyes e uma espécies do gênero Muggiaea, como grupos externos. A análise filogenética foi feita com o software TNT, e as árvores mais parcimoniosas foram buscadas usando pesagem implícita (k variando de 2 a 6). A análise resultou em quatro árvores mais parcimoniosas. A espécie L. leloupi é o grupo-irmão das espécies estudadas. As espécies de Lensia formaram um clado sustentado pelo hidroécio mediando até um quarto do comprimento do nectosaco.
Siphonophores are a group of hydrozoans (Cnidaria: Medusozoa) of great importance in the marine pelagic environment. Despite that, studies about the systematics of these organisms are scarce in the literature. Little is known about the phylogenetic relationships between the group's superior taxa, and little progress has been made until the moment for the genus Lensia. The objectives of the present study were to conduct a detailed morphological study of different morphotypes of the genus Lensia, obtained from two oceanographic campaigns, and perform a phylogenetic analysis of these morphotypes, based on the morphological data obtained. The analyzed material was collected by two oceanographic campaigns (FINEP III and Habitats Project), made throughout the southeastern Brazilian coast. A total of 61 specimens were analyzed and 15 species of Lensia were identified. Specimens were photographed using a stereomicroscope with digital camera attached. Posteriorly, the identification, morphological descriptions, elaboration of schemes, and measurements of specimens were performed. An identification key of the analyzed species was elaborated. Twenty two characters of the anterior nectophore of Lensia were listed, and codified in a data matrix. Two species of the genus Diphyes and one species of the genus Muggiaea were used as outgroups. A phylogenetic hypothesis, based on the morphological data, was inferred using the TNT software, and the shortest trees were searched using implied weighting (k varying from 2 to 6). The analysis resulted in four most parsimonious trees. The species L. leloupi is the sister group to all studied species. The species of Lensia formed a clade sustained by the hydroecium measuring up to onequarter the height of the nectosac.

Underwater surveillance missions both for defense and civilian applications are continually demanding the need for unmanned underwater vehicles or UUVs. Unmanned vehicles are needed to meet the logistical requirements for operation over long distances, greater depths, long duration, and harsh conditions. In order to design UUVs that not only satisfy these needs but are also adaptive and efficient, there has been increasing interest in taking inspiration from nature. These biomimetic/bio-inspired UUVs are expected to provide significant improvement over the conventional propeller based vehicles by taking advantage of flexible bodies and smart actuation. In this thesis, jetting jellyfish were utilized as the inspiration to understand the fundamentals of this new form of propulsion and subsequently translate the understanding onto the engineered platform to validate the hypothesis and construct robust models. Jetting jellyfish species are generally smaller in dimensions than rowing jellyfish, consume lower energy for transport, and exhibit higher proficiency. In the second chapter, a bio-inspired stationary jet propulsion mechanism that utilizes an iris diaphragm actuation system was developed. Detailed discussion is provided on the design methodology and factors playing the leading role in controlling the vortex formation. The propulsion mechanism was intended to mimic the morphological and deformation features of Sarsia sp. jellyfish that measures approximately 1 cm in diameter. The performance of experimental model was analyzed and modeled to elucidate the role of structure and fluid displacement. Utilizing the results from Chapter 2, a free-swimming jellyfish-inspired robot (named JetPRo) was developed (also utilizing an iris diaphragm) in Chapter 3 and characterized for relevant propulsive metrics. A combination of theoretical modeling and experimental analysis was used to optimize the JetPRo's gait for maximum steady-state swimming velocity. Next, an attempt was made towards creating a free-swimming jetting robot (named JP2) using a guided cable mechanism to achieve the desired actuation and improve the propulsion while simplifying the drive mechanism. Using JP2 robotic model, a systematic set of experiments were conducted and the results were used to refine the theory. Based upon the comprehensive computational analysis, an optimized swimming gait was predicted and then validated. A modular robot inspired by siphonophores was developed and initial efforts were made in laying down the foundation for understanding of this complex locomotion mechanism. Siphonophores are colonial organisms consisting of several jetting bodies attached to a central stem. An experimental model was developed mimicking the multimodal swimming propulsion utilized by Siphonophores. Several swimming gaits inspired by the natural animal were replicated and the preliminary performance of the experimental model was quantified. Using these results, an analysis is presented towards further improving the design and assembly of a siphonophore-inspired robot.
Master of Science

Les compartiments intermédiaires de l’écosystème pélagique (du mésozooplancton au micronecton) transfèrent l’énergie et la matière organique entre les producteurs primaires et un certain nombre d’espèces commerciales (anchois, sardines…). Certains de ces organismes produiraient des « couches diffusantes » (Sound Scattering Layers, SSLs) observés sur une large gamme d’échelles spatio-temporelles et de zones géographiques. Néanmoins, la composition taxonomique des SSLs reste encore en grande partie inconnue. L’objectif de cette thèse était de décrire la composition et la répartition de SSLs denses observées dans le golfe de Gascogne (GdG) au printemps à plusieurs échelles spatiales, en utilisant l’acoustique large bande, des filets et des outils vidéo. Dans le premier chapitre, nous avons montré que la largeur du faisceau d’un échosondeur avait peu d’impact sur les densités acoustiques de SSLs observées au printemps 2014, ce qui suggère que certaines SSLs du golfe de Gascogne pourraienten comparant la réponse acoustique large bande mesurée in situ aux prédictions de modèles de réflecteurs acoustiques paramétrées à l’aide des données d’échantillonnages biologiques. Nous avons déterminé que les réflecteurs dominant la réponse acoustique aux basses fréquences (18-150 kHz) étaient composés de siphonophores et de poissons mésopélagiques, tous porteurs d’inclusions gazeuses. La réponse acoustique aux plus hautes fréquences était dominée des organismes mésozooplanctoniques, dont de fortes densités de ptéropodes. Dans le troisième chapitre, nous avons appliqué des méthodes de clas
Intermediate trophic components of pelagic ecosystem (from mesozooplakton to micronekton) funnel energy and organic matters from primary producers to many commercial species (anchovy, sardines…). Some of these organisms are supposed to be important contributors to the ubiquitous Sound Scattering Layers (SSLs) observed over a broad range of spatio-temporal scales and geographical areas. Yet, the SSLs taxonomic composition remains largely unknown. The aim of this PhD was to describe the composition and repartition of dense SSLs observed in the Bay of Biscay (France) in spring at several spatial scales, using broadband acoustics, nets and videos. In the first chapter, we showed that the echo sounder beam widths had few effect on the SSLs backscatter, suggesting those SSLs could be composed of unidentified small gaseous scatterers. In the second chapter we applied a forward approach to characterize the composition of SSLs sampled in spring 2016 at small scale,by comparing in situ frequency responses to predictions of scatterer models parameterized with biological sampling data. We determined that these SSLs were probably composed of gas-bearing siphonophores, who, together with mesopelagic fish, dominated the frequency spectra at low frequencies (18-150 kHz). The acoustic backscatter at higher frequencies was dominated by a mix of mesozooplankton organisms, including high densities of pteropods. In the third chapter we applied unsupervised classification methods and a supervised discriminant analysis to delineate the spatial distribution of a peculiar surface SSL composed of

Les variations saisonnieres des populations d'hydromeduses et de scyphomeduses, de deux populations de siphonophores (chelophyes appendiculata et abylopsis tetragona) ainsi que d'une population de ctenaire (pleurobrachia rhodopis) ont ete etudiees durant 3 ans dans la rade de villefranche-sur-mer (mediterranee nord-occidentale). L'inventaire faunistique du peuplement des carnivores gelatineux de la rade est constitue d'especes regulierement pechees, d'especes rares ou d'especes presentant de fortes fluctuations interannuelles d'abondance. Le second suivi planctonique entre la surface et 60 m (les peches etant efectuees tous les 10m) a montre que la thermocline intervient, en fonction du caractere thermique des especes, pour orienter la distribution verticale des clenteres. Les distributions temporelle et bathymetrique varient pour les especes meroplanctoniques et holoplanctoniques et sont liees aussi bien aux saisons hydrologiques qu'aux saisons trophiques. Le suivi, au cours de 27 ans, des principales populations de carnivores gelatineux holoplanctoniques de la rade a montre que les annees d'observation peuvent etre classees en fonction des abondances des especes comme annees riches, moyennes ou annees pauvres, identifiant egalement des associations et des oppositions entre herbivores et carnivores pelagiques. Les parametres biologiques ont ete obtenus a partir d'elevages du ctenaire pleurobrachia rhodopis au laboratoire. Dans la gamme des concentrations en copepodes utilisees (jusqu'a 225 cop/1), le taux de predation augmente avec la disponibilite alimentaire. Aucune satiation n'est atteinte. Le volume nettoye apparent reste independant de la concentration en nourriture. Mots-clef : cnidaires et ctenaires, carnivores gelatineux, variations saionnieres, distribution bathymetrique, evolution a long terme, predation.

Au cours de ce travail, on a etudie la biometrie et la distribution saisonniere de 4 especes de siphonophores, et de 3 especes d'hydromeduses, parmi les especes les plus communes de la rade de villefranche-sur-mer. Du point de vue de la distribution saisonniere, le printemps et l'ete sont les saisons pendant lesquelles on a un maximum de siphonophores. D'autre part, le maximum d'hydromeduses se produit au cours de l'automne et de l'hiver. Au laboratoire, nous avons eleve deux especes d'hydromeduses clytia spp. Et obelia spp. , pour etudier l'influence de la temperature sur leur taux de croissance. Nous avons calcule le rendement de croissance de clytia spp. De deux facons: 1) a partir de l'excretion ammoniacale journaliere moyenne des meduses; 2) a partir de la consommation journaliere des meduses exprimes en poids sec de proies. En general, nous avons observe pour clytia spp. Un rendement de croissance plus eleve chez les individus les plus petits, et moins eleve chez les individus ayant atteint un diametre egal a 5-6 mm

Tese de doutoramento em Biociências, no ramo de Ecologia, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Gelatinous carnivores’ zooplankton, commonly known as “jellyfish”, are ubiquitous organisms in neritic systems worldwide, with an important ecological role in the pelagic food chains. During the past several decades, their ever-increasing, mostly due to environmental perturbations and climate alterations, becoming a big concern for marine ecologists, due to the implications off their blooms on the zooplankton communities. In the Mondego estuary, the gelatinous zooplankton community is composed by higher Hydromedusae diversity and, also, by two colonial species, belonging to the order of Siphonophorae, the Calicophorans Muggiaea atlantica and its congener Muggiaea kochii, the former has constituted the most abundant gelatinous organisms in the Mondego estuary since 1994. The first chapter aimed to describe how changes in the species richness, the phenology, and the abundance of the gelatinous carnivores of the Mondego estuary during the period 2003-2013, were influenced by the North Atlantic Oscillations and its effect on regional atmospheric variability, such as on upwelling activity. During the 11-year time series, the most abundant gelatinous species were M. atlantica, Lizzia blondina, Obelia sp., Liriope tetraphylla, Solmaris corona and Clytia hemisphaerica. During the period investigated, the gelatinous community displayed phenological shifts, changed their mean annual pattern from unimodal to bimodal peak, before and after 2007, respectively. Also, the species richness increased since 2007-2008, with the increase presence of rare species. Shifts on the gelatinous community were connected to the atmospheric forces promoted by the NAO and its influence on upwelling activity and regional climate, as statistical analysis confirmed. The second chapter describes, more specifically, the spatial distribution on seasonal scale, of the two siphonophores species present in the Mondego estuary, M. atlantica and M. kochii and explained which environmental factors most influenced their life cycle in the estuary. The study was conducted during two years, 2014 and 2015, characterized by a different scenario in terms of precipitation. In fact, 2014 was considered a normal year and 2015 was dryer than the previous. Generally, in all the sampling zones, M. atlantica was more abundant than its congener, and both species presented higher abundance, in terms of colonies and gonophores, in the downstream area of the estuary. Moreover, during the dryer year (2015), it was observed an increase of the M. atlantica colonies, while the abundance of M. kochii was not affected by the increase in salinity values, maintaining similar abundance values during both years. Generally, salinity and prey availability have been pointed out as the determinant drivers for the reproduction and distribution of these two species in the Mondego estuary, and the positive regression coefficients denoted positive influence of salinity, calanoid nauplii, cirripedia cypris and cyclopioda copepodites on both species nectophores and gonophores. Finally, in the third chapter, being M. atlantica a voracious predator in neritic waters, it was assessed the feeding activity and the selectivity of this species in the Mondego estuary on daily scale, during a half tide cycle (11 hours). For this purpose, it was analysed the gastrozooids (stomachs) content of the eudoxids (sexual stage) of M. atlantica estimating, also, the consumption of the different prey found in the stomachs. Generally, M. atlantica and eudoxids reached the higher abundance value during the flood tide and, again, the salinity was the environmental driver that most influence the presence of M. atlantica at daily scale, as confirmed by the multiple regression analysis and the Principal Component Analysis. Moreover, greater variability of prey was found before the high tide, corresponding, also, to the time when the largest number of full stomachs have been found. Thus, prey identified in the eudoxids stomachs (the copepod Euterpina acutifrons and copepod nauplii), confirmed the prey selectivity of M. atlantica, mostly to the small dimensions of its stomachs. It was estimated that, in the Mondego estuary, M. atlantica eudoxia consumed between 1.48 to 3.84 prey dayˉ¹mˉ³. These values were lower compared with others studies, probably because the night-time predation was not considered and, also, because the study analysed only the gastrozooids content of M. atlantica eudoxida (the sexual stage) and not of adult colonies. These findings provide baseline information to our understanding of the ecology of the gelatinous carnivorous communities in the Iberian Peninsula.
O zooplâncton carnívoro gelatinoso, geralmente conhecido como "água-viva" ou "jellyfish", encontra-se presente em sistemas neríticos em todo o mundo e desempenha um papel ecológico importante nas cadeias alimentares pelágicas. Durante as últimas décadas o contínuo aumento destes organismos, principalmente devido a perturbações ambientais e alterações climáticas antropogénicas, tem-se tornando uma grande preocupação para os biólogos marinhos, devido aos impactos e alterações que o seu aumento exponencial na estrutura e ecologia alimentar das comunidades marinhas. No estuário do Mondego a comunidade zooplanctónica gelatinosa é composta em grande parte por Hydromedusae e, também, por duas espécies coloniais, pertencentes à ordem de Siphonophorae, os Calicophorans Muggiaea atlantica e o seu congênere Muggiaea kochii, sendo a primeira a espécie gelatinosa mais abundante no estuário do Mondego desde 1994. Nesta dissertação o primeiro capítulo tem por objetivo descrever como a mudança na riqueza de espécies, a fenologia e a abundância dos carnívoros gelatinosos do estuário do Mondego, durante o período 2003-2013, foram influenciadas pela Oscilação do Atlântico Norte (NAO) e os seus efeitos na variabilidade atmosférica regional como, por exemplo, nos padrões de upwelling. Durante o estudo as espécies gelatinosas mais abundantes foram M. atlantica, Lizzia blondina, Obelia sp., Liriope tetraphylla, Solmaris corona e Clytia hemisphaerica, e a comunidade gelatinosa apresentou mudanças fenológicas, alterando o seu padrão anual médio, passando de um pico de abundância para dois picos, antes e depois de 2007, respetivamente. Além disso, a riqueza específica aumentou e, desde 2007-2008, as espécies raras aumentaram em abundância. Todas essas mudanças na comunidade gelatinosa estiveram ligadas as forças atmosféricas promovidas pelo NAO e a sua influência sobre os padrões de upwelling e o clima regional, como confirmou a análise estatística. Se o primeiro capítulo teve uma abordagem em grande escala sobre toda a comunidade gelatinosa, o segundo capítulo descreve, mais especificamente, a distribuição espacial à escala sazonal das duas espécies de sifonóforos presentes no estuário do Mondego, M. atlantica e M. kochii, explicando quais foram os fatores ambientais que mais influenciaram o seu ciclo de vida no estuário. O estudo foi realizado durante dois anos, 2014 e 2015, caracterizados por um cenário diferente em termos de precipitação. Na verdade, 2014 foi considerado um ano normal e 2015 foi mais seco do que o anterior. Geralmente, em todas as zonas de amostragem, M. atlantica foi mais abundante do que a sua congênere, e ambas as espécies apresentaram maior abundância, em termos de colônias e gonóforos, na área a jusante do estuário. Além disso, durante o ano de seca (2015), observou-se um aumento das colónias de M. atlantica, ao passo que a distribuição e a abundância de M. kochii não foram afetadas pelo aumento dos valores de salinidade, mantendo valores de abundância similares em ambos os anos. Geralmente, a salinidade e as presas foram apontadas como os fatores determinantes na reprodução e distribuição dessas duas espécies no estuário do Mondego e os coeficientes de regressão indicaram a influência positiva da salinidade, nauplius de calanoide, cypris de cirripedia e copepodites de ciclopoida nos nectóforos e gonóforos de ambas as espécies. Finalmente, no terceiro capítulo, sendo M. atlantica um predador voraz em águas neríticas, foi avaliada a sua atividade de alimentação e a seletividade em termos de presas no estuário do Mondego numa escala diária, durante um ciclo de semi-maré. Para este propósito, foi analisado o conteúdo de gastrozóoides (estômagos) das eudoxias (fase sexual) de M. atlantica estimando, também, o consumo das diferentes presas encontradas nos estômagos. Geralmente, M. atlantica e as eudoxias atingiram o maior valor de abundância durante a enchente e, novamente, a salinidade foi a variável ambiental que mais influenciou a presença e a variabilidade diária de M. atlantica, resultado confirmado pela análise de regressão múltipla e da Análise de Componentes Principais. Além disso, maior variabilidade de presas foi encontrada antes da maré alta, que também correspondeu ao momento em que o maior número de estômagos cheios foram encontrados. Assim, as presas identificadas nos estômagos das eudoxias (o copepode Euterpina acutifrons e náuplios de copepoda), confirmaram a seletividade em termos de presas devido, principalmente, às pequenas dimensões dos seus estômagos. Estima-se que, no estuário do Mondego, as eudoxias de M. atlantica consumiram entre 1,48 a 3,84 presasˉ¹mˉ³ dˉ¹, resultados baixos em comparação com outros estudos, provavelmente porque a predação noturna não foi considerada e, também, porque o estudo analisou apenas o conteúdo de gastrozóoides das eudoxias de M. atlantica (o estágio sexual) e não o de colónias adultas.

碩士
國立中山大學
海洋生物科技暨資源學系研究所
94
Temporal and spatial distribution in species composition and abundance of siphonophores in relation to hydrographic variables in the waters off southern and northern Taiwan were investigated from December 2003 to August 2004. In total, 48 siphonophoran species belonging to 18 genera and 7 families were recognized, with the mean abundance of 2226 ± 1228 ind./1000 m3. The abundance of siphonophores showed an obvious seasonal change, lower in December and February and higher in May and August. The six most dominant species, together they contributed to 66.5 % of the numerical total of siphonophores, were Chelophyes contorta, Bassia bassensis, Chelophyes appendiculata, Abylopsis eschscholtzi, Abylopsis tetragona and Eudoxoides mitra. The dominant siphonophoran species exhibited apparent seasonal succession. Different dominant species showed different seasonal distribution patterns and most species were dominated by sexual generation. Result of the cluster analysis of siphonophoran data revealed 2 station groups. GroupⅠwas mostly composed by the stations in February and May, and group Ⅱ contained the stations in May and August. Forty-two siphonophoran species belonging to seven families and nineteen genera were recognized in the waters off northern Taiwan, with the mean abundance of 7129 ± 10240 ind./1000 m3. The abundance of siphonophores displaced an apparent seasonal change, significantly higher in February and August and lower in December and May. The six most dominant species, together they contributed to 79.4 % of the numerical total of siphonophores, were Diphyes chamissonis, C. appendiculata, Muggiaea atlantica, Lensia subtiloides, B. bassensis and E. mitra. The dominant siphonophoran species showed obvious seasonal succession and different dominant species exhibited different seasonal distribution patterns. Muggiaea atlantica and L. subtiloides were dominated by polygastric stage, while other species were mostly the eudoxid generation. Result of CA of siphonophores revealed 3 station proups. GroupⅠ was primarily the stations in the northwestern waters off Taiwan waters in December, Group Ⅱ contained the stations in the northeastern waters off Taiwan in all seasons. Group Ⅲ was mainly the sations in the northwestern waters off Taiwan in February and May. The mean species number and species diversity were always higher in southern waters than in northern waters of Taiwan, but the overall mean abundance was three times higher in the northern waters than in the southern waters. The overall mean abundance in this study showed higher in December 2003 and lower in February and May 2004. Result of the ANOVA test revealed the significant difference in siphonophoran abundance between May and August 2004 in both southern and northern stations. The abundance of total siphonophores was not significantly correlated with water temperature, salinity and chlorophyll a. The abundance of the six most dominant species in the southern Taiwanese waters was not significantly correlated to water salinity and chlorophyll a, but the abundance of C. contorta, B. bassensis, A. eschscholtzi and C. appendiculata were apparently influenced by water temperature. The abundance of the six most dominant species in the northern Taiwanese waters exhibited different correlationships with hydrographic variables, C. appendiculata showed significantly positive correlation with chlorophyll a, B. bassensis exhibited significantly positive correlation with water temperature, salinity and chlorophyll a, while E. mitra was significantly positively correlated with salinity.

This chapter describes the taxonomy of colonial Hydrozoa. Siphonophores are pelagic organisms that can be found the whole year round, sometimes in a characteristic season, inshore and offshore at all latitudes and depths. As in all hydrozoans, they carry tentacles equipped with stinging cells (nematocysts), which are used by the colony to immobilize and kill their prey. The chapter covers their life cycle, ecology, and general morphology. It includes a section that indicates the systematic placement of the taxon described within the tree of life, and lists the key marine representative illustrated in the chapter (usually to genus or family level). This section also provides information on the taxonomic authorities responsible for the classification adopted, recent changes which might have occurred, and lists relevant taxonomic sources.