Three species of Carangidae family were caught incidentally during collection of cannonball jellyfish (Stomolophus meleagris) in Bahía de La Paz, Gulf of California, Mexico. All fish were measured, ...preserved and identified as post flexion larvae and early juvenile of Chloroscombrus orqueta, Hemicaranx leucurus and Caranx caballus. C. orqueta stood out in frequency and abundance. H. leucurus were found only in autumn, while the others were present in different seasons. This is the first time recording H. leucurus and C. caballus associating with cannonball jellyfish. Further studies must evaluate this association as all fish caught were at vulnerable stages, and must be considered in jellyfish fishery management.
Численность, биомасса, размерная структура популяций желетелых хищников медуза Aurelia aurita Linnaeus, 1758; гребневики Mnemiopsis leidyi A. Agassiz, 1865 и Pleurobrachia pileus (O. F. Müller, 1776) ...и интенсивность питания двух видов (A. aurita и M. leidyi) исследованы в раннелетний период (июнь) 2016 г. на 45 станциях, охватывавших зону шельфа у берегов Крыма от м. Тарханкут до г. Керчи, а также на 3 станциях глубоководного района с координатами 44°23′N–45°5′N и 32°22′E–36°36′E. Сбор материала проводили вертикальными тралениями от дна (10–100 м) до поверхности на шельфовых станциях и от глубины с σt = 16,2 до поверхности ― на глубоководных, используя модифицированную сеть Богорова ― Расса с диаметром входного отверстия 80 см и ячеëй 500 мкм. Спектр питания определяли под микроскопом в лаборатории сразу после вылова животных, рассчитывая впоследствии суточные рационы и скорость выедания зоопланктона. Установлены пространственные различия в биомассе и численности отдельных видов: максимальная биомасса A. aurita, преобладавшей во всех районах, отмечена в Евпаторийско-Севастопольском районе и обусловлена большими скоплениями среднеразмерных особей новой генерации. Гребневик P. pileus доминировал по численности в районе халистазы. Пищевой спектр медуз был очень разнообразен и включал различные стадии Copepoda, Tunicata, Cladocera, а также меропланктонные организмы ― велигеров Bivalvia и Gastropoda. Халистатическая зона с большими глубинами характеризовалась максимальным количеством видов планктонных Copepoda в пище A. aurita. Среднесуточные рационы медуз, рассчитанные по содержанию пищи в гастральной полости и по времени переваривания, изменялись в широких пределах от района к району. Самыми низкими показатели были в Каркинитском заливе (0,113 ± 0,10) мг C·экз.-1·сут-1, или (1,6 ± 2,18) % C тела, где большую долю пищи составляли водоросли Coscinodiscus granii Gough, 1905. Наиболее интенсивно питались животные в халистатической области (0,687 ± 0,094) мг C·экз.-1·сут-1, или (56,2 ± 23,7) % C тела, в пище преобладали Calanus euxinus Hulsemann, 1991 и Pseudocalanus elongatus Boeck, 1865. Ни в одном из районов A. aurita не могла компенсировать затраты на дыхание за счёт потребления мезозоопланктона. Наибольший пресс на зоопланктон оказывала популяция медуз в Каркинитском заливе и в Евпаторийско-Севастопольском районе, хотя во всех исследованных районах её пресс был очень низок и не приводил к кардинальному сокращению численности зоопланктонного сообщества.
Carnivorous gelatinous zooplankton dominate the zooplankton community in Chesapeake Bay during summer months, exerting considerable top-down control on the planktonic food web. To examine the ...cascading effects of gelatinous zooplankton blooms on the plankton food web and particulate organic carbon (POC) flux, multiple 2-day mesocosm experiments were conducted in the York River tributary of Chesapeake Bay in July–August 2015. Mesocosms contained a natural assemblage of phytoplankton, microzooplankton, and copepods, and each treatment received additions of the ctenophore (Mnemiopsis leidyi), the scyphozoan medusae (Chrysaora chesapeakei), or both gelatinous zooplankton. There was no significant difference between treatments in total POC or PON flux. However, presence of M. leidyi reduced the abundance of copepods, in turn significantly decreasing copepod fecal pellet carbon flux compared to treatments without M. leidyi by 50% (from 36 to 18μgCd−1m−3, or 6% to 3% of total POC flux). Total POC export fluxes were small in all treatments (<1%) compared to previously measured sedimentation rates in the Chesapeake Bay. Top-down changes in copepod fecal pellet carbon flux are equivalent to a modest portion (~10%) of previously calculated C. chesapeakei carcass flux. Future experiments and models of zooplankton contributions to vertical carbon flux should include top-down processes and cascading effects.
•Top-down control of vertical particle flux is often not considered in marine pelagic food webs.•Gelatinous zooplankton exhibit top-down control of plankton in the Chesapeake Bay.•Through their control of the food web, jellyfish affect vertical carbon flux in the Chesapeake Bay.•Presence of gelatinous predators leads to lower flux of copepod fecal pellets.
Large blooms of
Rhopilema nomadica
, a highly venomous rhizostamatid scyphozoan species introduced to the Mediterranean through the Suez Canal, have become ubiquitous in the summer and winter months ...along the Israeli coasts since the mid-1980s. This species has since spread across the eastern Mediterranean and was sighted as far west as Tunisia and Sardinia. For the past 12 years, we have studied changes in the mitochondrial COI haplotypes diversity of
R. nomadica
to investigate small scale fluctuactions of genetic diversity and to reveal possible genetic structuring of the fast spreading invader in the Eastern Mediterranean. The 1091 COI sequences analysed, revealed a highly diverse population displaying 89 haplotypes, 46 of which appeared as singletons, low frequency haplotypes. All the specimens analysed throughout the period belong to a single unstructured population. Though lacking data from the source population in the Red Sea, the high within-population diversity and the high diversity of COI haplotypes support the hypothesis of multiple introductions events, or an open corridor with a continuous influx of propagules. Tajima’s D and Fu’s Fst negative values and the increased numbers of COI singletons from early to late sampling periods, have verified that the Israeli population is characterized by a rapid expanding population. Further research is needed for the evaluation of COI diversity and patterns in
R. nomadica
populations across the eastern Mediterranean Sea and Red Sea, as well as any correlation of the high variability between COI locus and phenotypic diversity.
Due to their boom and bust population dynamics and the enormous biomasses they can attain, jellyfish and ctenophores can have a large influence on the cycling of carbon (C), nitrogen (N) and ...phosphorus (P). This review initially summarises the biochemical composition of jellyfish, and compares and contrasts the mechanisms by which non-zooxanthellate and zooxanthellate jellyfish acquire and recycle C, N and P. The potential influence of elemental cycling by populations of jellyfish on phytoplankton and bacterioplankton production is then assessed. Non-zooxanthellate jellyfish acquire C, N and P predominantly through predation on zooplankton with smaller contributions from the uptake of dissolved organic matter. C, N and P are regenerated via excretion of inorganic (predominantly ammonium (NH₄ ⁺) and phosphate (PO₄ ³⁻)) and dissolved organic forms (e.g. dissolved free amino acids and dissolved primary amines). Inorganic nutrients excreted by jellyfish populations provide a small but significant proportion of the N and P required for primary production by phytoplankton. Excretion of dissolved organic matter may also support bacterioplankton production but few data are available. In contrast, zooxanthellate medusae derive most of their C from the translocation of photosynthetic products, exhibit no or minimal net release of N and P, and may actively compete with phytoplankton for dissolved inorganic nutrients. Decomposition of jellyfish blooms could result in a large release of inorganic and organic nutrients and the oxygen demand required to decompose their tissues could lead to localised hypoxic or anoxic conditions.
Abstract
Despite its wide spatial distribution and its high abundance in the Mediterranean Sea, the biology and the ecology of the scyphozoan species Pelagia noctiluca remain poorly understood. This ...is mainly due to difficulties related to sampling and its maintenance in laboratory conditions. Thus, only a few studies exist on the ecophysiology of this jellyfish species under laboratory conditions. As an example, the maximum sizes of individuals obtained in previous culturing systems were not comparable to the ones found in the environment and the authors could not obtain a second generation. Here we present an improved rearing system for P. noctiluca employing a new enclosed system running with artificial seawater. The monitoring of the jellyfish in this new system highlights the importance of the quality of the food sources provided to the cultures, as well as the volume available for jellyfish growth. We obtain adults similar in size to the ones found in the open ocean (>11 cm), and we were able to obtain a second generation, 140 days after the first one. Our system is both less time-consuming and less stressful for the jellyfish.
Jellyfish can cause high mortality of farmed fish and hence significant economic losses for the aquaculture industry. Despite their socio-economic importance, distribution and diversity data on ...gelatinous plankton are scarce from northern Norwegian fjords and other Nordic systems. Intense blooms of jellyfish have repeatedly been observed in Ryggefjord, Finnmark (Norway), sometimes concurrent with severe health problems of salmon. In the present study, the jellyfish community of this fjord was studied in summer 2015. In July, at least 13 species were identified using a combination of morphological and molecular techniques. High densities of small Beroe spp. and ctenophore larvae in cydippid stage dominated the surface waters. Adult Beroe cucumis were also present. Molecular identification revealed the presence of juvenile Euphysa tentaculata, as well as 2 species each of Clytia and Obelia. Obelia longissima was identified from both its pelagic (medusa) and benthic (polyp) stages, indicating that some local populations can complete their entire life cycle in the fjord. Abundances were significantly different between inner and outer parts of the fjord, and in relation to the prevailing wind direction. A dense bloom of the hydrozoan Dipleurosoma typicum in September coincided with high mortalities of farmed fish, suggesting a causal relationship. We conclude that the jellyfish assemblage in Ryggefjord is dynamic on short time scales and structured by both oceanographic conditions and local reproduction. A better understanding of seasonal population development and the relationships between hydrography, abundance and species composition is required to develop mitigation strategies for aquaculture operations.
Two novel all-in-one electrochromic devices have been fabricated on the basis of low-cost and environmentally benign marine brown algae laminaria japonica, and jellyfish, which were both utilized as ...electronic component (gel electrolytes) in combination with electrochromic viologen bis(3-hydroxypropyl) viologen dibromide, and electron mediators 1,1′-ferrocene dicarboxylic acid and 1,1′-ferrocenedimethanol. The electrochromic performance of the as-fabricated devices was tested. The two biological ECDs exhibited driving voltages as low as 1.1 V, which is superior to many traditional viologen-based ECDs. Moreover, following the principles of green chemistry, no waste and organic solvents were introduced during the room-temperature device assembly. Based on abundant content of biological tissues, the device can be presented as a proof-of-concept to find potential applications in the fields of low-cost, green and large-scale ECDs.
•Biological products, seaweeds and jellyfish were firstly utilized as gel electrolytes in the electrochromic devices.•The cost of film formation and device assembly could be saved due to green and abundant biological products in nature.•No toxic wastes and other organic solvents were introduced during room-temperature device assembly in order to meet the requirements of green chemistry.
Although fossil evidence suggests that various animal groups were able to move actively through their environment in the early stages of their evolution, virtually no direct information is available ...on the nature of their muscle systems. The origin of jellyfish swimming, for example, is of great interest to biologists. Exceptionally preserved muscles are described here in benthic peridermal olivooid medusozoans from the basal Cambrian of China (Kuanchuanpu Formation, ca. 535 Ma) that have direct equivalent in modern medusozoans. They consist of circular fibers distributed over the bell surface (subumbrella) and most probably have a myoepithelial origin. This is the oldest record of a muscle system in cnidarians and more generally in animals. This basic system was probably co-opted by early Cambrian jellyfish to develop capacities for jet-propelled swimming within the water column. Additional lines of fossil evidence obtained from ecdysozoans (worms and panarthropods) show that the muscle systems of early animals underwent a rapid diversification through the early Cambrian and increased their capacity to colonize a wide range of habitats both within the water column and sediment at a critical time of their evolutionary radiation.
Underwater transparently camouflaged organisms can be perfectly "invisible" in the ocean to avoid the capture of predators. Due to the blurry contour boundaries of their bodies, obtaining their ...boundary features and determining their specific positions are challenging for detection tasks. To address this issue, first, we propose a large-scale underwater transparently camouflaged object dataset, termed Aqua-Eye, which is obtained from event data and contains five types of underwater transparent organisms, with a total of 6497 annotated images. Second, to evaluate the effectiveness of this dataset, we propose a simple and effective detection network termed underwater Transparently Camouflaged Object Detection Network (TransCODNet), which can obtain local features and specific locations of targets, providing a better detection method for underwater transparently camouflaged organisms. In this letter, we performed ablation study and nine representative deep learning algorithms were evaluated based on the dataset. Finally, experiments show that the detection accuracy of this algorithm is 84.7%, which is superior to mainstream object detection algorithms, proving the effectiveness of the proposed method.
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