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The cannonball jellyfish Stomolophus meleagris display colour variations from blue to purple, and different pigmentation patterns on the umbrella surface. Although these colour phenotypes are commo...

Worldwide catches of cannonball jellyfish Stomolophus meleagris (Cnidaria: Scyphozoa) have increased during the last years; nevertheless, this species still lacks updated biological knowledge for its management. This research proposes that the individual growth pattern for jellyfish can be estimated in the absence of age readings through cohort follow-up over time and by multi-model inference approach (MMI). Length data were obtained during 2010–2011 in Gulf of California to obtain cohort information using a multinomial analysis and then assign age; growth model selection was based on MMI. Three cohorts were identified and the von Bertalanffy model suitably described their growth. The species has an accelerated growth with a short life cycle; cohorts one and two reached their asymptotic length, and the third one barely reached the length-at-first sexual maturity. Growth variations among cohorts could be explained by their different biological strategies where the first two prioritized asymptotic length and the third one reproduction length. The three cohorts shared a common goal for medusoid phase, which was sexual reproduction. This information could be used for estimating harvest rates or assessing their capacity for redoubling as an invasive population in coastal ecosystems. The proposed methodology may be applied in other jellyfish species around the world.

Exploitation of the cannonball jellyfish (Stomolophus sp. 2) is increasing in Mexico and USA due to successful fisheries associated with seasonal blooms in coastal areas. Previously, it was proposed that such blooms could be identified by recognizing the presence of young stages in the water. In our work, we aim to describe the young stages (ephyra and metaephyra) found in the Las Guásimas lagoon, Sonora, Mexico. The description of specimens is based on photographs, drawings, and morphological measurements aimed at helping in the early detection of blooming events.

The digestive capacity of jellyfish has barely been studied because of the complexity of their life stage body-forms and sizes. To assess the digestive capacity in the changes from the benthic polyp-form to the pelagic stage in the cannonball jellyfish Stomolophus meleagris, we used fluorometric and spectrophotometric techniques for measuring the activity of trypsin, chymotrypsin, aminopeptidase, amylase, lipase, phosphatase acid, and alkaline. The findings showed that at all stages were able to digest proteins, carbohydrates, and lipids, but the digestive capacity differs between the benthic–pelagic stage and final development of the ephyrae, suggesting a shift in nutrient requirements. The digestive capacity indicated that polyps better assimilate carbohydrates and proteins. During the pelagic stage, a shift in the digestive capacity occurred, where 5-day ephyrae better assimilate proteins, while 15-day-old ephyrae were better with lipids and proteins and juvenile medusae with lipids. This is the first study to describe changes in the digestive capacity of cannonball jellyfish and can help identify ecological features of an important fishing resource with potential aquaculture interest. Different diets for polyps, ephyrae, and juvenile medusae must be considered if the species is cultivated.

espanolEl objetivo de esta investigacion fue conocer el rol de los actores involucrados en la pesqueria de medusa bola de canon, en Guaymas, Sonora. Con el metodo bola de nieve se realizaron entrevistas semiestructuradas, luego se jerarquizaron mediante la red de poder/ interes de cuatro cuadrantes, y se relacionaron con una matriz de vinculacion. El resultado arrojo que el Instituto Nacional de Pesca, los compradores, procesadores, comercializadores y las cooperativas pesqueras son los actores clave, con mayor interes e influencia en el manejo de la pesqueria. El presente analisis es util para establecer y mejorar el manejo de la captura de medusa. Se concluye que existe una relacion conflictiva y de poca cooperacion entre los actores mencionados, lo cual impide que se respeten las estrategias de manejo para explotar la medusa en condiciones de sustentabilidad. EnglishThe aim of this research was to know the role of stakeholders involved in the cannonball jellyfish fishery in Guaymas, Sonora. Using the snowball method, semi-structured interviews were conducted, then hierarchized through the power / interest network of four quadrants, and related to a connection matrix. The result showed that the National Fishery Institute, buyers, processors, marketers and fishing cooperatives are the key players, with greater interest and influence in the management of the fishery. This analysis is useful to establish and enhance the management of jellyfish catch. It follows that there is a conflictive relationship and little cooperation among the said stakeholders, which prevents management strategies to exploit jellyfish fishing in conditions of sustainability from being respected.

Cannonball jellyfish has become the target of an important seasonal fishery in the Gulf of California. Research has focused mainly on biological and management aspects, yet linkages and dynamics between social and ecological components have received less attention. Based on an analysis of stakeholder perceptions and its comparison with available quantitative data, this study provides a holistic view of the fishery and its actors as part of a complex adaptive system. Stakeholders include artisanal fishers, owners of improvised and permanent processing plants, foreign buyers and funders, local managers, Mexican management entities, women, and Indigenous communities. Policy guidelines and management actions must address sustainability within various dimensions as understood by those interviewed: social equity, economic benefits, and environmental responsibility. To transition to sustainability, a transdisciplinary research approach is needed to provide management advice and to strengthen fishery governance through co-management decision-making strategies.

Jellyfish are non-model organisms that have brought the scientific community's attention over the last decades since the frequency and intensity of these species blooms around the world have increased significantly. The occurrence of blooms has been hypothesized due to the rise in seawater temperature associated with climate change. This fact has promoted an increased interest in studying jellyfish metabolic responses to face thermal stress and maintain cell homeostasis. In this study, the response of the cannonball jellyfish Stomolophus meleagris to short-term exposure to different temperatures was evaluated. The survival and respiratory rates, and the concentration of glucose, L-lactate, glycogen, ATP, and total soluble protein in the umbrella of adult jellyfish were measured. Low survival rates at extreme temperatures (18 and 33 °C) and an increase in the jellyfish respiratory rates were observed as seawater temperature raised. Rapid changes were detected in energy substrates such as glucose and glycogen that significantly varied at extreme temperatures and longer exposure periods. L-lactate levels increased after 2 h of exposure, and then remained steady at longer times of exposure. Soluble protein concentration decreased significantly in jellyfish exposed to extreme temperatures, and ATP increased after exposure to non-optimal temperatures (18, 28, and 33 °C). These results suggest that S. meleagris faces temperature changes through rapid metabolic responses that use energetic reserves, activate anaerobic metabolism, and display a remarkable ability to synthesize ATP and maintain energy, even at long exposure.

The digestive system and metabolism of the cannonball jellyfishStomolophussp. 2 are not well-known. The digestion study was critical to explain its ecology and bloom success. Different enzymes are involved in food digestion, which hydrolyze carbohydrates, proteins, and lipids. This study detected lipolytic activity in enzymatic extracts from gastric pouches ofStomolophussp. 2 collected in the summer of 2013 at Bahía de Kino, Sonora, México (28°47′47″N 111°57′25″W). Lipase/esterase activity showed optimal pH at 11.0 and 50–60 °C with a half-life (t1/2) of 33 min at 55 °C, whereas halotolerance of this activity was recorded from 0-4 M NaCl. Metal ions Ca2+and Mn2+did not affect the activity, but Mg2+decreased it 14.2% ± 3.15, while chelating agents as ethylenediaminetetraacetic acid reduced the activity 8.55% ± 2.13. Inhibition of lipase/esterase activity with tetrahydrolipstatin and paraoxon-ethyl decreased the activity 18.2% ± 2.3, and 62.80% ± 0.74, respectively, whereas phenylmethanesulfonyl fluoride (a protease inhibitor) did not affect it. The enzyme displayed a higher specificity for short-chain triglycerides, but triolein, coconut oil, olive oil, and fish oil were hydrolyzed. For the first time, phospholipase activity from the gastric pouch ofStomolophussp. 2 was detected using L-α-phosphatidylethanolamine from chicken egg yolk as a substrate. These results suggest thatStomolophussp. 2 hydrolyze several kinds of lipids, and lipolytic enzymes are active at alkaline pH under different saline conditions, which may be essential to digest different preys.

Stomolophus meleagris (Cannonball Jellyfish) is a common Cnidarian species in the coastal waters of Georgia. Libinia spp. (spider crab) juveniles commonly inhabit the bell of the Cannonball Jellyfish, but there is uncertainty as to whether the crabs are parasitic on the Cannonball Jellyfish or are commensals. To assess the nature of this symbiosis, Cannonball Jellyfish were randomly sampled at multiple sites along the Georgia coast. For each Cannonball Jellyfish, the number of juvenile spider crabs inhabiting the bell was recorded along with multiple measurements of Cannonball Jellyfish and spider crabs. Our results suggest that the symbiosis between the Cannonball Jellyfish and juvenile spider crabs is an example of commensalism and not parasitism.

This study describes the first record of the whale shark Rhincodon typus association with the cannonball jellyfish Stomolophus meleagris in the Gulf of California, Mexico. Whale sharks were observed swimming and feeding among swarms of jellyfish, suggesting competition and predatory behaviour given the overlap in food preferences between both species. This finding is relevant because of the species-wide distribution and the importance of these interactions, which should be considered in conservation strategies of R. typus and management of cannonball jellyfish fisheries.

The diet and feeding pattern of scyphomedusa Stomolophus meleagris (Rhizostomeae) was studied, by comparing stomach samples from different developmental stages and environmental zooplankton with the aim to determine diet composition, trophic niche breadth, selectivity and feeding overlap of this edible jellyfish species. Samplings were performed during April and December 2010 and in January 2011, in the coastal lagoon Las Guásimas (27°49′–27°54′N 110°40′–110°35′W), central Gulf of California, which consisted of zooplankton tows and jellyfish collections for stomach content. More than 39 prey items were identified in the gut contents (N = 69), from which eight taxa formed over 90% of the total. Fish eggs were considered main prey (58.6%), copepods (10.8%), veliger larvae of gastropod (13.0%) and bivalve (12.7%) were secondary prey while cirriped and decapod larvae were incidental prey (S. meleagris is a specialist predator and Pearre's index showed positive selection of fish eggs, gastropods, bivalves and cirripeds while selectivity was negative for copepods and appendicularians. The relative timing of these changes suggests that ontogenetic processes are closely related with shift in the diet, which indicates increasing predation pressure during development of the medusoid stage of this species, thus emphasizing their ecological importance in coastal ecosystems.

Studies of population genetic structure in relation to ecological and evolutionary processes are crucial for conservation genetics and particularly for sustainable management of fisheries. However, such knowledge is not always available for the management of fisheries, as is the case of the edible cannonball jellyfish Stomolophus spp. fishery in the Gulf of California, Mexico. The aim of this study is describe the population genetic structure of cannonball jellyfish in the Gulf of California. We used sequences of cytochrome oxidase I (COI) and microsatellite markers in five locations within the Gulf of California and the southern Pacific coast. Both COI and microsatellite markers corroborated the presence of two differentiated genetic lineages in the fishing areas, which diverged around 1.17 Mya: Stomolophus sp.1, distributed in the Golfo de Santa Clara; and Stomolophus sp.2, in the southern region of the Gulf of California and the Pacific coast of the Baja California peninsula. In addition, significant differentiation between the four locations within the lineage Stomolophus sp.2 was found (mean FST: 0.56 and 0.12 for COI and microsatellites respectively). Our results are consistent with the endemism and phylogeographic break hypotheses proposed for the northern region of the Gulf of California. We proposed that the historical geology and complex oceanography of the Gulf of California might be responsible of this species-level differentiation. Conversely, the population structure within Stomolophus sp.2 could be more related to the life cycle, and particularly due the short larval dispersal stage of cannonball jellyfish in the Gulf of California.