Advances in marine biology最新文献

While jellyfish are often considered to be a nuisance, their value to ecosystems and for human exploitation is shifting this perception. People have been eating jellyfish for millennia. In recent decades, the scale of jellyfish fisheries has expanded dramatically, with annual catches in the hundreds of thousands of tonnes. The overwhelming majority of jellyfish species targeted for human consumption are from the order Rhizostomeae, which can also be fed to livestock and certain species in mariculture operations. The use of rhizostome jellyfish is expanding beyond food applications, such as pharmaceuticals and cosmetics, especially for collagen and other bioactive compounds. Jellyfish collagen is high in antioxidants, can act as an immunostimulator, and has applications for tissue engineering and medical implements. Jellyfish venom extracts exhibit high biological activities, including those that are antihypertensive, antimicrobial, and anticancer. Jellyfish can also be used as fertilizers and insecticides, and jellyfish mucus appears to have potential as a filter for nanoparticles and microplastics, suggesting possible applications in wastewater treatment. Most of these applications are still in developmental stages, and beyond their use as food, jellyfish are not targeted at commercial scale, apart from collagen extraction. As research advances, exploitation of jellyfish is expected to continue expanding. Given the lack of knowledge and understanding regarding jellyfish fisheries and their management, caution should be exhibited to avoid overfishing.

The genus Kogia includes two species that are some of the least known cetacean species around the globe. Here, we investigated the occurrence, behavior, and habitat suitability of dwarf sperm whales (K. sima) off St. Vincent and the Grenadines (Eastern Caribbean). Small boat dedicated surveys were conducted during May and June of both 2022 and 2023 along the south and west coast of the island of St. Vincent. A total of 2260 km was surveyed and 33 sightings of dwarf sperm whale were recorded, which was also the most frequently sighted cetacean species (37.5% of all cetacean sightings). Group size varied from 1 to 20 individuals (mean = 2.08, SD = 3.23). Traveling and breaching were the most commonly recorded behavioral categories and occurred at an equal proportion (28.6%). The distribution of dwarf sperm whales was restricted to the south and southwest portion of St. Vincent in depths ranging from 95 to 1104 m (mean = 650 m). Habitat suitability (in relation to depth and slope) was investigated using an ensemble model using three algorithms (GLM, GAM, and MaxEnt). The model revealed that slope, and to a lesser extent depth, were important in explaining the habitat suitability of dwarf sperm whales. This preliminary research highlights the existence of a globally important area for dwarf sperm whales off St. Vincent, where encounter rates are significantly higher than in any other known island-associated habitat.

Cetaceans are a critical component of marine ecosystems, acting as top predators in mesopelagic trophic webs. In the Macaronesian biogeographical region, cetacean populations face threats from various anthropogenic activities. Evaluating cryptic oceanic species like kogiids whales is challenging due to insufficient biological and ecological data, making conservation assessments and management efforts harder to achieve. Kogia breviceps and K. sima comprising the family Kogiidae, are morphologically similar, widely distributed, and elusive, with most information originating from stranded specimens and few at sea observations. This study examines data from Kogia species stranded in the Canary Islands between 1977 and 2024 and analyzes sighting data obtained between 1999 and 2024. Between 1977 and May 2024, there were 111 stranding events involving 114 kogiid individuals along the Canary Islands' coasts: 86 events (88 individuals) were pygmy sperm whales, 14 events (15 individuals) were dwarf sperm whales, and 11 events with 11 individuals, were unidentified Kogia species. Additionally, 36 kogiid sightings were recorded, of which 34 originated from dedicated surveys and 2 from opportunistic sightings. Of these sightings, 14 (39%) were K. breviceps, 9 (25%) were K. sima, and 13 (36%) were unidentified Kogia. Twenty-nine sightings (80.5%) of kogiids were recorded in the waters off the eastern coast of the islands of Lanzarote and Fuerteventura. The data indicate that the waters around the Canary Islands are an important habitat for Kogia whales. The findings establish a baseline for future research and underscore the necessity of accurately assessing conservation pressures on pygmy and dwarf sperm whales in the region.

The Cells of Ecosystem Functioning are natural units of management and conservation, allowing for an ecosystem-based maritime spatial planning based on an accurate knowledge of marine biodiversity and ecosystem functioning which, however, is presently insufficient and fragmentary. A five-step roadmap to fill current knowledge gaps and make ecosystem-based marine sustainability possible is proposed: Step 1: make the inventory of biodiversity. Step 2: unveil the roles of species. Step 3: understand the ecological relationships that link species with each other and with the physical environment. Step 4: frame marine biodiversity and ecosystem functioning in a five dimensional spatial and temporal context (the Cells of Ecosystem Functioning). Step 5: plan our activities so as to preserve a healthy state of ecosystems. EU legislation has drawn a careful map to guide us along this road, with a series of directives that, if successfully enforced, will be conducive to knowledge-based marine sustainability.

The morphology of members of the order Rhizostomeae is revisited considering all life cycle stages, but with emphasis on the medusa. The current classification of the group is presented, and some aspects of species diversity are discussed. The main issues investigated since the 1970s are briefly presented by decade.

In the present study we reviewed the life cycles and reproduction strategies of the order Rhizostomeae. We found 28 species with described life cycles representing ∼30% of the valid species. The metagenetic life cycle of most scyphozoans, which includes the benthic asexually-reproducing polyp and the pelagic sexually-reproducing medusa, is exhibited by all rhizostome species. Rhizostomeae are dioecious with only two exceptions described as hermaphroditic. Sexual dimorphism can be found in species with special external structures utilised for brooding but others show no sexual dimorphism despite the colour of mature gonads. Six asexual reproduction modes have been described for the production of new polyps but rhizostome polyps propagate through a main mode that differs among taxa. Species belonging to Dactyliophorae produce new polyps by podocysts whereas the Kolpophorae new polyps develop from free-swimming buds. The number of ephyrae formed per strobila differs between taxa with monodisc and polydisc strobilation in the Kolpophorae and Dactyliophorae, respectively. Given the low number of studied species it is expectable that new reproductive strategies will be discovered when additional species are investigated. We recommend increasing (1) descriptions on life cycles and reproductive strategies for a greater number of species, (2) attempts to locate the polyps in the field, (3) the study of species in their natural environment, to understand the population dynamics of Rhizostomeae and to clarify the potential of artificial structures to increase medusa populations. In addition, experimental studies are needed to improve our understanding of the factors affecting transitions between life cycle stages and medusa production rates.

Max Egon Thiel's chapter on the ecology of rhizostomes in his review up to 1970 covered a bewildering variety of topics, many of which are the focus of other chapters in this volume: their interactions with humans; their associations with other organisms; their venoms. Although he also discussed their habitats and habits, the effects of environmental conditions on distribution, and patterns in seasonality, he paid scant attention to blooms, he did not write about their role in the wider ecosystem, and he ignored alien introductions. It is clearly impossible to comprehensively update Thiel's review in a similar vein - we don't have the space - and so we have decided to focus our efforts here on either those topics that particularly fascinated him (seasonality), or those that he did not write about (alien introductions, their role in the ecosystem). Our narrative is based on case studies of well known taxa, from which we attempt to draw patterns of commonality, where appropriate. We conclude our account with a discussion of rhizostomes as Discomedusae, and whether we should be considering them separately from semaeostomes in terms of ecology.

Written to serve as a guideline for future research in this field, this roadmap provides some perspectives on the main developments and remaining challenges in the field of marine animal acclimatisation, adaptive potential and resilience to climate change. There has been extensive research conducted on the impact of climate change stress on marine animals, with studies recognising the potential for cross- and multi- generational impacts. Parents can potentially pass on resilience to offspring. The response of marine animals to climate change stressors is complex where utilising marginal and extreme systems as natural laboratories can help to address key research gaps and provide an understanding of the plastic and adaptive changes necessary for survival under stress.

Rhizostomeae species attract our attention because of their distinctive body shape, their large size and because of blooms of some species in coastal areas around the world. The impacts of these blooms on human activities, and the interest in consumable species and those of biotechnological value have led to a significant expansion of research into the physiology and functional biology of Rhizostomeae jellyfish over the last years. This review brings together information generated over these last decades on rhizostome body composition, locomotion, toxins, nutrition, respiration, growth, among other functional parameters. Rhizostomes have more than double the carbon content per unit of biomass than jellyfish of Semaeostomeae. They swim about twice as fast, and consume more oxygen than other scyphozoans of the same size. Rhizostomes also have faster initial growth in laboratory and the highest body growth rates measured in nature, when compared to other medusae groups. Parameters such as body composition, nutrition and excretion are highly influenced by the presence of symbiotic zooxanthellae in species of the Kolpophorae suborder. These physiological and functional characteristics may reveal a wide range of adaptive responses, but our conclusions are still based on studies of a limited number of species. Available data indicates that Rhizosotomeae jellyfish have a higher energy demand and higher body productivity when compared to other jellyfish groups. The information gathered here can help ecologists better understand and make more assertive predictions on the role of these jellyfish in their ecosystems.

Why females would mate with multiple partners and have multiple fathers for clutches or litters is a long-standing enigma. There is a broad dichotomy in hypotheses ranging from polyandry having benefits to simply being an unavoidable consequence of a high incidence of male-female encounters. If females simply give in to mating when it is too costly to avoid being harassed by males (convenience polyandry), then there should be a higher rate of mating as density increases. However, if females actively seek males because they benefit from multiple mating, then mating frequency, and consequently the incidence of multiple paternity of clutches, should be high throughout. To explore these competing explanations, here we review the incidence of multiple paternity for sea turtles nesting around the World. Across 30 rookeries, including all 7 species of sea turtle, the incidence of multiple paternity was only weakly linked to rookery size (r²=0.14). However, using high resolution at-sea GPS tracking we show that the specifics of movement patterns play a key role in driving packing density and hence the likely rate of male-female encounters. When individuals use the same focal areas, packing density could be 100× greater than when assuming individuals move independently. Once the extent of adult movements in the breeding season was considered so that movements and abundance could be combined to produce a measure of density, then across rookeries we found a very tight relationship (r²=0.96) between packing density and the incidence of multiple paternity. These findings suggest that multiple paternity in sea turtles may have no benefit, but is simply a consequence of the incidence of male-female encounters.