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Revealing hidden diversity among upside-down jellyfishes (Cnidaria: Scyphozoa: Rhizostomeae: Cassiopea): distinct evidence allows the change of status of a neglected variety and the description of a new species
Abstract
Morphological variability within Cassiopea is well documented and has led to inaccuracies in the establishment of species boundaries in this taxon. Cassiopea medusae specimens from the Western Pacific (Japan and the Philippines) were analysed using multiple lines of complementary evidence, including types of cnidae, macro-morphology and molecular data. These observations lead to the recognition of two distinct species: Cassiopea mayeri, sp. nov. and a previously synonymised variety now raised to species level (Cassiopea culionensis, stat. nov.). These species can be distinguished from each other using morphological features. Herein, sexually dimorphic traits are included for the first time in the descriptions of Cassiopea species. Nematocyst types not previously observed in the genus are also reported. Molecular analyses, based on individual and combined markers (16S + cytochrome c oxidase I, COI), also support two distinct species; they are not sister taxa, and both are nested together within a clade of other Cassiopea members from the Australian and Indo-Pacific regions. Species richness is underestimated in the Western Pacific region, and integrative approaches are helpful to reveal and describe species. The systematics of Cassiopea is far from completely understood, but the present study represents an important further step.
... Despite this, Cassiopea continued to be reported in the scientific literature using outdated identification keys and taxonomic understanding. Many papers have discussed this issue (Stamper et al. 2020;Ohdera et al. 2018;Morandini et al. 2017;Graham and Bayha 2007;Holland et al. 2004), and recent Cassiopea reports include thorough descriptions that integrate molecular phylogenetics and morphology (Gamero-Mora et al. 2022;Stamper et al. 2020, Arai et al. 2017Morandini et al. 2017). However, most reports do not use a standardized set of observations or nomenclature when referring to macromorphology, which prevents the scientific community from scrutinizing species identifications. ...
... The observed phenotypic plasticity of macromorphological characters suggests that macromorphology alone is insufficient as a means for accurate species identification. While DNA barcodes have emerged as a standard tool for distinguishing among closely related, cryptic species in Scyphozoa (e.g., Gamero-Mora et al. 2022;Lawley et al. 2021;Bayha et al. 2017;Holland et al. 2004;Dawson and Jacobs 2001), the cnidome (census of nematocysts) potentially represents another suite of characters that may assist species identification. Cnidome characterizations and descriptions are common practice in other cnidarian groups such as anemones (e.g., Acuña et al. 2003;Fautin 1988) to facilitate species identification. ...
... Cnidome characterizations and descriptions are common practice in other cnidarian groups such as anemones (e.g., Acuña et al. 2003;Fautin 1988) to facilitate species identification. While cnidome descriptions are becoming more common in scyphozoan taxonomy and systematics, within Cassiopea, cnidomes have only been reported for four species: Cassiopea andromeda Forskål, 1775 (Cengiz et al. 2021;Gülşahin 2016;Heins et al. 2015;Östman 2000;Jensch and Hofmann 1997), Cassiopea xamachana Bigelow, 1892(Ames et al. 2020Jensch and Hofmann 1997), Cassiopea mayeri Gamero-Mora, Collins, Boco, Geson III & Morandini, 2022(Gamero-Mora et al. 2022, and Cassiopea culionensis Light, 1914(Gamero-Mora et al. 2022. ...
This contribution investigates phenotypic plasticity in Cassiopea ornata Haeckel, 1880 from Guam, Micronesia. We collected C. ornata from two distinct habitats and used DNA barcoding for species identification. With this, we were able to document intraspecific phenotypic variation between populations that is likely reflective of distinct ecotypes rather than species-specific disparities. In particular, macromorphological characters, such as vesicle shapes and sizes, have been used as characters to discriminate among species of Cassiopea varied between populations. In addition, we uncovered differences in cassiosome structure and composition between populations that suggest differences in trophic modes across populations. Conducting a meta-analysis of a comprehensive cnidome dataset, we show that nematocysts may provide important information for species delineation and identification in Cassiopea, a suite of characters not fully exploited thus far. We interpret differences in vesicle and cassiosome morphology in conjunction with nematocyst size disparities as a reflection of environment-mediated shifts in trophic strategy (photo-autotrophy versus heterotrophy). Given the interest in Cassiopea as a model organism, the observations presented herein lay out a roadmap for studies that aim at linking environmental heterogeneity to phenotypic plasticity.
... The relative distances for the Discomedusae were proposed and discussed inDaglio et al. (2017), with a tetramodal outcome, presenting an intraspecific value at ~0.006 ± 0.005 and interspecific between congeneric species of ~0.12 ± 0.04. Main references:(Abboud et al., 2018; Arai et al., 2017; Armani et al., 2013; Bayha et al., 2010; Daglio & Dawson, 2017; Dawson & Hamner, 2005; Dong et al., 2016; Galil et al., 2017;Gamero-Mora et al., 2022;Gómez Daglio et al., 2022;Gotoh et al., 2017;Holland et al., 2004;Maas et al., 2020; Rizman-Idid et al., 2016; Souza & Dawson, 2018;Stampar et al., 2021; Swift et al., 2016; Swift & Dawson, 2020). ...
Upside-down jellyfish are a group of benthic scyphozoans belonging to the genus Cassiopea, whose members are in symbiosis with dinoflagellates and inhabit tropical and subtropical waters. Although there are some studies of the genus in the Caribbean, these are limited. In Cuba, the group's studies are restricted to reports on taxonomic lists and, as far as we know, no one has performed any analyzes of the densities of these jellyfish in seagrass or mangrove ecosystems in Cuba. In this work, the populations of Cassiopea spp. in Jardines de la Reina National Park (JRNP) were characterized, for the first time for this Marine Protected Area and Cuba. One hundred 1m2 square frames were placed at 14 JRNP sites. For each site, the species, density, size of the individuals, and abiotic factors were determined. Density and diameter comparisons were made between sites, zones, and regions within the JRNP. The percentage of the benthic cover was determined and a correlation was made between density and diameter. A total of 10,803 individuals were recorded, of which 7,618 belong to Cassiopea xamachana and 3,185 belong to Cassiopea frondosa. Both species share a niche and no evident segregation was detected according to abiotic variables. Significant differences were detected in comparisons of density and size across sites and zones. Density and size in the JRNP were negatively correlated, and higher aggregations of the species were observed at lower sizes. Density mean values ranged from 2.18 to 14.52 ind. /m 2 with maximum values of 79 ind. /m 2. Cayo Alcatraz was the site found to have the highest density while Cachiboca was the site with the lowest density. The average bell diameter size of the individuals ranged from 9.34 to 15.31 cm for the sampled sites, with minimum and maximum values of 2.5 cm and 32.6 cm. The smallest size was recorded at Cayo Alcatraz while the largest size was reported for Boca de las Anclitas. The environmental factors evaluated showed no significant relationship with the density or diameter of Cassiopea, while the Thalassia testudinum cover was negatively correlated with Cassiopea density at all fourteen sites in the JRNP. The percentage of Cassiopea coverage was higher than those reported in the literature, with four sites exceeding 20% coverage. In general, the populations of Cassiopea spp. in the JRNP did not differ greatly, although a higher density was observed towards the eastern region of the park. It was shown for the first time for the species that density and size have a negative correlation. Future studies are required to quantify the impact of Cassiopea on coastal marine ecosystem processes and to further determine how anthropogenic changes may be altering the function of these tropical ecosystems.
Cryptic species have been detected across Metazoa, and while no apparent morphological features distinguish them, it should not impede taxonomists from formal descriptions. We accepted this challenge for the jellyfish genus Aurelia, which has a long and confusing taxonomic history. We demonstrate that morphological variability in Aurelia medusae overlaps across very distant geographic localities. Even though some morphological features seem responsible for most of the variation, regional geographic patterns of dissimilarities are lacking. This is further emphasized by morphological differences found when comparing lab-cultured Aurelia coerulea medusae with the diagnostic features in its recent redescription. Previous studies have also highlighted the difficulties in distinguishing Aurelia polyps and ephyrae, and their morphological plasticity. Therefore, mostly based on genetic data, we recognize 28 species of Aurelia, of which seven were already described, 10 are formally described herein, four are resurrected and seven remain undescribed. We present diagnostic genetic characters for all species and designate type materials for newly described and some resurrected species. Recognizing moon jellyfish diversity with formal names is vital for conservation efforts and other studies. This work clarifies the practical implications of molecular genetic data as diagnostic characters, and sheds light on the patterns and processes that generate crypsis.
The massive occurrence of jellyfish in several areas of the world is reported annually, but most of the data come from the northern hemisphere and often refer to a restricted group of species that are not in the genus Cassiopea. This study records a massive, clonal and non-native population of Cassiopea and discusses the possible scenarios that resulted in the invasion of the Brazilian coast by these organisms. The results indicate that this jellyfish might have invaded the Brazilian coast multiple times.
To better understand how ecosystems are changing, a multifaceted approach to measuring biodiversity that considers species richness (SR) and evolutionary history across spatial scales is needed. Here, we compiled 162 datasets for fish, bird and plant assemblages across the globe and measured how taxonomic and phylogenetic diversity changed at different spatial scales (within site α diversity and between sites spatial β diversity). Biodiversity change is measured from these datasets in three ways: across land use gradients, from species lists, and through sampling of the same locations across two time periods. We found that local SR and phylogenetic α diversity (Faith's PD (phylogenetic diversity)) increased for all taxonomic groups. However, when measured with a metric that is independent of SR (phylogenetic species variation, PSV), phylogenetic α diversity declined for all taxonomic groups. Land use datasets showed declines in SR, Faith's PD and PSV. For all taxonomic groups and data types, spatial taxonomic and phylogenetic β diversity decreased when measured with Sorensen dissimilarity and phylogenetic Sorensen dissimilarity, respectively, providing strong evidence of global biotic homogenization. The decoupling of α and β diversity, as well as taxonomic and phylogenetic diversity, highlights the need for a broader perspective on contemporary biodiversity changes. Conservation and environmental policy decisions thus need to consider biodiversity beyond local SR to protect biodiversity and ecosystem services.
Chrysaora (Pèron & Lesueur 1810) is the most diverse genus within Discomedusae, and 15 valid species are currently recognised, with many others not formally described. Since Chrysaora fulgida (Reynaud 1830) was first recognised as occurring off the south west (SW) coast off South Africa, the species has been variously synonymised with Chrysaora hysoscella (Linnaeus 1767) and Chrysaora africana (Vanhöffen 1902). Using DNA evidence alongside multivariate tools to analyse quantitative morphometric and meristic data, as well as information from the cnidome, we unambiguously separate C. fulgida from C. hysoscella; we resurrect C. africana as a valid species and recognise a new species, Chrysaora agulhensis sp. nov. Full descriptions of C. fulgida, C. africana and C. agulhensis sp. nov. are provided. The species have different geographical patterns of distribution around the region, with restricted areas of overlap: C. agulhensis sp. nov. is found along the southern coast of South Africa and over the Agulhas Bank, C. fulgida extends from Cape Point in South Africa to southern Angola, and C. africana can be found from southern Namibia northwards to the Gulf of Guinea. The species can be readily separated in the field by a combination of tentacle/lappet number and shape, colour patterns and the form of the oral arms.
Snorkelers in mangrove forest waters inhabited by the upside-down jellyfish Cassiopea xamachana report discomfort due to a sensation known as stinging water, the cause of which is unknown. Using a combination of histology, microscopy, microfluidics, videography, molecular biology, and mass spectrometry-based proteomics, we describe C. xamachana stinging-cell structures that we term cassiosomes. These structures are released within C. xamachana mucus and are capable of killing prey. Cassiosomes consist of an outer epithelial layer mainly composed of nematocytes surrounding a core filled by endosymbiotic dinoflagellates hosted within amoebocytes and presumptive mesoglea. Furthermore, we report cassiosome structures in four additional jellyfish species in the same taxonomic group as C. xamachana (Class Scyphozoa; Order Rhizostomeae), categorized as either motile (ciliated) or nonmotile types. This inaugural study provides a qualitative assessment of the stinging contents of C. xamachana mucus and implicates mucus containing cassiosomes and free intact nematocytes as the cause of stinging water. Cheryl L Ames, Anna Klompen et al. describe cassiosomes, stinging cell structures in the mucus of the upside-down jellyfish Cassiopea xamachana. They show that these motile cell masses consist of an outer epithelial layer largely composed of nematocytes surrounding centralized clusters of endosymbiotic dinoflagellates.
This study provides the first observation that umbrellar tissue can lead to the formation of virtually all body structures in jellyfish of the order Rhizostomeae. The regeneration process was observed in two specimens of the upside-down jellyfish Cassiopea xamachana Bigelow, 1892, one housed at the Vienna Zoo, Austria and the other in a laboratory at the University of São Paulo, Brazil. The process was triggered by an injury and ended with the formation of two new sets of body structures. Our observation offers evidence that C. xamachana has a hidden regenerative capacity exceeding that previously recorded.
A previous study detected mixing of two deeply split mtDNA clades (Clade I and Clade II) for Atlantic and Mediterranean populations of the medusozoan Pelagia noctiluca . The north hemisphere glaciations and the Messinian salinity crisis have been proposed as the two main biogeographic events related to the isolation between the Atlantic Ocean and the Mediterranean Sea. We tested if the splitting time between Clade I and Clade II of P. noctiluca was associated with one of these geological events. Our study was based on DNA sequence data of mitochondrial (COI and 16S ribosomal RNA) and nuclear (18S ribosomal RNA, internal transcribed spacer 1 and 5.8S ribosomal RNA) genes from populations of the Atlantic and Pacific Ocean and the Mediterranean Sea. The rise of the Isthmus of Panama was used to calibrate substitution rates for COI. This calibration was based on the detection of a shallow but significant genetic structure between P. noctiluca populations from the Pacific and the Atlantic Oceans. Considering our calibration for COI, we refute a possible origin of Clades I and II during the Messinian salinity crisis. Our estimates suggest the origin for a putative common ancestor of Clades I and II around 2.57 Ma (with 95% 2.91–2.22 HPD), roughly corresponding to the Gelasian stage of the early Pleistocene. These alterations include changes in the sea level and oceanic currents at the Strait of Gibraltar and other regions of the Mediterranean basin, and could explain the origin of the two P. noctiluca clades.
The Philippines is often highlighted as the global epicenter of marine biodiversity, yet surveys of reef-associated fishes in this region rarely extend beyond shallow habitats. Here, we improve the understanding of fish species diversity and distribution patterns in the Philippines by analyzing data from mesophotic coral ecosystems (MCEs; 30–150 m depth) obtained via mixed-gas rebreather diving and baited remote underwater video surveys. A total of 277 fish species from 50 families was documented, which includes thirteen newly discovered and undescribed species. There were 27 new records for the Philippines and 110 depth range extensions, indicating that many reef fishes have a broader geographic distribution and greater depth limits than previously reported. High taxonomic beta-diversity, mainly associated with family and genus turnover with depth, and significant effects of traits such as species body size, mobility and geographic range with maximum recorded depth, were observed. These results suggest that MCEs are characterized by unique assemblages with distinct ecological and biogeographic traits. A high proportion (60.5%) of the fish species are targeted by fishing, suggesting that Philippine MCEs are as vulnerable to overfishing as shallow reefs. Our findings support calls to expand conservation efforts beyond shallow reefs and draw attention to the need to explicitly include deep reefs in marine protected areas to help preserve the unique biodiversity of MCEs in the Philippines.
Scyphozoans are currently causing great concern worldwide due to the effects of their blooms on the marine environment. During a field survey in Beibu Gulf, South China Sea, on 27 May 2015, we found specimens of a rhizostome jellyfish that had not previously been recorded in Chinese seas. The morphological characters and DNA sequences of several specimens were examined in the laboratory. These specimens had the following morphological characters: hemispherical umbrella with reticular grooves; eight large semicircular velar lappets alternating with narrow lappets in each of the 8 octants; laterally flattened mouth-arms with numerous flat, membranous branches bearing many clubs and intermediate filaments; non-anastomosed broad perradial canals and anastomosed narrow interradial canals. The morphological characters of these rhizostome jellyfish were consistent with descriptions of Versuriga anadyomene. Furthermore, phylogenetic analysis of mitochondrial 16S rDNA and nuclear 18S rDNA gene fragments confirmed that these specimens were in the same cluster as V. anadyomene collected in Palau. Therefore, this rhizostome jellyfish was identified as V. anadyomene. This is the first record of the genus Versuriga and the species V. anadyomene in Chinese seas. The arrival of this species may be attributed to physical transport from the coastal waters of South East Asia.
Mastigias, the 'golden' or 'spotted' jellyfish, is distributed throughout the Indo-Pacific. Specimens are identified routinely as Mastigias papua, although eight species were described historically, and molecular analyses evince at least three phylogenetic species. Understanding species diversity in Mastigias has become a priority because of its growing relevance in studies of boom-bust dynamics related to environmental change, cryptic species, local adaptation, parallel evolution, and peripatric speciation. However, species delimitation and identification are inhibited by a dearth of type specimens for most species, including M. papua. We address these issues by resampling Mastigias from the type locality in Waigeo, West Papua, as well as in the Philippines, and by comparing cytochrome c oxidase subunit I and up to 34 morphological characters of 268 Mastigias specimens from surrounding regions in the Indo-Pacific. We also gathered data from the historical descriptions of the eight species of Mastigias to estimate the identity of the two other currently revealed clades. Using this integrative taxonomic approach, we re-describe Mastigias papua as endemic to the tropical western Pacific islands (including Papua, Palau, Enewetak) and designate a neotype for the species. Additionally, based on morphological similarity and geographic overlap, we identified a second clade most probably as M. albipunctatus (from Japan, Komodo, Berau and Philippines) and a third clade tentatively as either M. andersoni or M. ocellatus. This study highlights the benefits of combining molecular analyses, samples from type locations, traditional descriptions and statistical analyses of morphological variation in systematic studies, and the concomitant potential of such studies to increase understanding of evolutionary patterns and processes in Scyphozoa.
Symbiont-bearing Larger Benthic Foraminifera (LBF) are ubiquitous components of shallow tropical and subtropical environments and contribute substantially to carbonaceous reef and shelf sediments. Climate change is dramatically affecting carbonate producing organisms and threatens the diversity and structural integrity of coral reef ecosystems. Recent invertebrate and vertebrate surveys have identified the Coral Triangle as the planet’s richest center of marine life delineating the region as a top priority for conservation. We compiled and analyzed extensive occurrence records for 68 validly recognized species of LBF from the Indian and Pacific Ocean, established individual range maps and applied Minimum Convex Polygon (MCP) and Species Distribution Model (SDM) methodologies to create the first ocean-wide species richness maps. SDM output was further used for visualizing latitudinal and longitudinal diversity gradients. Our findings provide strong support for assigning the tropical Central Indo-Pacific as the world’s species-richest marine region with the Central Philippines emerging as the bullseye of LBF diversity. Sea surface temperature and nutrient content were identified as the most influential environmental constraints exerting control over the distribution of LBF. Our findings contribute to the completion of worldwide research on tropical marine biodiversity patterns and the identification of targeting centers for conservation efforts.
Background
The phylogeny of Cnidaria has been a source of debate for decades, during which nearly all-possible relationships among the major lineages have been proposed. The ecological success of Cnidaria is predicated on several fascinating organismal innovations including stinging cells, symbiosis, colonial body plans and elaborate life histories. However, understanding the origins and subsequent diversification of these traits remains difficult due to persistent uncertainty surrounding the evolutionary relationships within Cnidaria. While recent phylogenomic studies have advanced our knowledge of the cnidarian tree of life, no analysis to date has included genome-scale data for each major cnidarian lineage.
Results
Here we describe a well-supported hypothesis for cnidarian phylogeny based on phylogenomic analyses of new and existing genome-scale data that includes representatives of all cnidarian classes. Our results are robust to alternative modes of phylogenetic estimation and phylogenomic dataset construction. We show that two popular phylogenomic matrix construction pipelines yield profoundly different datasets, both in the identities and in the functional classes of the loci they include, but resolve the same topology. We then leverage our phylogenetic resolution of Cnidaria to understand the character histories of several critical organismal traits. Ancestral state reconstruction analyses based on our phylogeny establish several notable organismal transitions in the evolutionary history of Cnidaria and depict the ancestral cnidarian as a solitary, non-symbiotic polyp that lacked a medusa stage. In addition, Bayes factor tests strongly suggest that symbiosis has evolved multiple times independently across the cnidarian radiation.
Conclusions
Cnidaria have experienced more than 600 million years of independent evolution and in the process generated an array of organismal innovations. Our results add significant clarification on the cnidarian tree of life and the histories of some of these innovations. Further, we confirm the existence of Acraspeda (staurozoans plus scyphozoans and cubozoans), thus reviving an evolutionary hypothesis put forward more than a century ago.
Electronic supplementary material
The online version of this article (10.1186/s12862-018-1142-0) contains supplementary material, which is available to authorized users.
The upside-down jellyfish Cassiopea xamachana (Scyphozoa: Rhizostomeae) has been predominantly studied to understand its interaction with the endosymbiotic dinoflagellate algae Symbiodinium. As an easily culturable and tractable cnidarian model, it is an attractive alternative to stony corals to understanding the mechanisms driving establishment and maintenance of symbiosis. Cassiopea is also unique in requiring the symbiont in order to complete its transition to the adult stage, thereby providing an excellent model to understand symbiosis-driven development and evolution. Recently, the Cassiopea research system has gained interest beyond symbiosis in fields related to embryology, climate ecology, behavior, and more. With these developments, resources including genomes, transcriptomes, and laboratory protocols are steadily increasing. This review provides an overview of the broad range of interdisciplinary research that has utilized the Cassiopea model and highlights the advantages of using the model for future research.
Upside-down jellyfish, the genus Cassiopea is widely distributed in coastal regions of tropical
and subtropical waters all over the world. It is extremely difficult to classify and identify species in the genus.
In this study, Cassiopea spp. were surveyed in marine lakes and a lagoon in Palau Islands, and their speciesdiversity
was inferred based on a molecular phylogenetic analysis and morphological observations. We collected
the jellyfishes from six sites of marine lakes and a lagoon and analyzed their COXI gene. The phylogenetic
analysis discriminated 4 highly differentiated lineages and the jellyfishes in the 2 lineages were identified
as C. ornata and C. andromeda, respectively, in comparison with the previous data. The jellyfishes in the other
2 lineages were unreported lineages. Only a species inhabits most marine lakes, although 3 species sympatrically
inhabit the lagoon. Although their morphological characters are quite different between individuals of
marine lakes and a lagoon even in the same species, those are similar between the different species in marine
lakes. Such complicated morphological variations make extremely difficult to classify and identify Cassiopea
spp.
Background
Species of the scyphozoan family Pelagiidae (e.g., Pelagia noctiluca , Chrysaora quinquecirrha ) are well-known for impacting fisheries, aquaculture, and tourism, especially for the painful sting they can inflict on swimmers. However, historical taxonomic uncertainty at the genus (e.g., new genus Mawia ) and species levels hinders progress in studying their biology and evolutionary adaptations that make them nuisance species, as well as ability to understand and/or mitigate their ecological and economic impacts.
Methods
We collected nuclear ( 28S rDNA) and mitochondrial (cytochrome c oxidase I and 16S rDNA) sequence data from individuals of all four pelagiid genera, including 11 of 13 currently recognized species of Chrysaora . To examine species boundaries in the U.S. Atlantic sea nettle Chrysaora quinquecirrha , specimens were included from its entire range along the U.S. Atlantic and Gulf of Mexico coasts, with representatives also examined morphologically (macromorphology and cnidome).
Results
Phylogenetic analyses show that the genus Chrysaora is paraphyletic with respect to other pelagiid genera. In combined analyses, Mawia , sampled from the coast of Senegal, is most closely related to Sanderia malayensis , and Pelagia forms a close relationship to a clade of Pacific Chrysaora species ( Chrysaora achlyos, Chrysaora colorata , Chrysaora fuscescens , and Chrysaora melanaster ). Chrysaora quinquecirrha is polyphyletic, with one clade from the U.S. coastal Atlantic and another in U.S. Atlantic estuaries and Gulf of Mexico. These genetic differences are reflected in morphology, e.g., tentacle and lappet number, oral arm length, and nematocyst dimensions. Caribbean sea nettles (Jamaica and Panama) are genetically similar to the U.S. Atlantic estuaries and Gulf of Mexico clade of Chrysaora quinquecirrha .
Discussion
Our phylogenetic hypothesis for Pelagiidae contradicts current generic definitions, revealing major disagreements between DNA-based and morphology-based phylogenies. A paraphyletic Chrysaora raises systematic questions at the genus level for Pelagiidae; accepting the validity of the recently erected genus Mawia , as well as past genera, will require the creation of additional pelagiid genera. Historical review of the species-delineating genetic and morphological differences indicates that Chrysaora quinquecirrha Desor 1848 applies to the U.S. Coastal Atlantic Chrysaora species (U.S. Atlantic sea nettle), while the name C. chesapeakei Papenfuss 1936 applies to the U.S. Atlantic estuarine and Gulf of Mexico Chrysaora species (Atlantic bay nettle). We provide a detailed redescription, with designation of a neotype for Chrysaora chesapeakei , and clarify the description of Chrysaora quinquecirrha . Since Caribbean Chrysaora are genetically similar to Chrysaora chesapeakei , we provisionally term them Chrysaora c.f. chesapeakei . The presence of Mawia benovici off the coast of Western Africa provides a potential source region for jellyfish introduced into the Adriatic Sea in 2013.
Tapeworms of the genus Anindobothrium Marques, Brooks & Lasso, 2001 are found in both marine and Neotropical freshwater stingrays of the family Potamotrygonidae. The patterns of host association within the genus support the most recent hypothesis about the history of diversification of potamotrygonids, which suggests that the ancestor of freshwater lineages of the Potamotrygonidae colonized South American river systems through marine incursion events. Despite the relevance of the genus Anindobothrium to understand the history of colonization and diversification of potamotrygonids, no additional efforts were done to better investigate the phylogenetic relationship of this taxon with other lineages of cestodes since its erection. This study is a result of recent collecting efforts to sample members of the genus in marine and freshwater potamotrygonids that enabled the most extensive documentation of the fauna of Anindobothrium parasitizing species of Styracura de Carvalho, Loboda & da Silva, Potamotrygon schroederi Fernández-Yépez, P. orbignyi (Castelnau) and P. yepezi Castex & Castello from six different countries, representing the eastern Pacific Ocean, Caribbean Sea, and river basins in South America (Rio Negro, Orinoco, and Maracaibo). The newly collected material provided additional specimens for morphological studies and molecular samples for subsequent phylogenetic analyses that allowed us to address the phylogenetic position of Anindobothrium and provide molecular and morphological evidence to recognize two additional species for the genus. The taxonomic actions that followed our analyses included the proposition of a new family, Anindobothriidae fam. n., to accommodate the genus Anindobothrium in the order Rhinebothriidea Healy, Caira, Jensen, Webster & Littlewood, 2009 and the description of two new species—one from the eastern Pacific Ocean, A. carrioni sp. n., and the other from the Caribbean Sea, A. inexpectatum sp. n. In addition, we also present a redescription of the type species of the genus, A. anacolum (Brooks, 1977) Marques, Brooks & Lasso, 2001, and of A. lisae Marques, Brooks & Lasso, 2001. Finally, we discuss the paleogeographical events mostly linked with the diversification of the genus and the protocols adopted to uncover cryptic diversity in Anindobothrium.
The endosymbiosis between cnidarians and dinoflagellates of the genus Symbiodinium is key to the high productivity of tropical coral reefs. In this endosymbiosis, Symbiodinium translocate most of their photosynthates to their animal host in exchange for inorganic nutrients. Among these, carbon dioxide (CO2) derived from host respiration helps to meet the carbon requirements to sustain photosynthesis of the dinoflagellates. Nonetheless, recent studies suggest that productivity in symbiotic cnidarians such as corals is CO2-limited. Here we show that glucose enrichment stimulates respiration and gross photosynthesis rates by 80 and 140 %, respectively, in the symbiotic upside-down jellyfish Cassiopeia sp. from the Central Red Sea. Our findings show that glucose was rapidly consumed and respired within the Cassiopeia sp. holobiont. The resulting increase of CO2 availability in hospite in turn likely stimulated photosynthesis in Symbiodinium. Hence, the increase of photosynthesis under these conditions suggests that CO2 limitation of Symbiodinium is a common feature of stable cnidarian holobionts and that the stimulation of holobiont metabolism may attenuate this CO2 limitation.
Anthropogenic nutrient inputs enhance microbial respiration within many coastal ecosystems, driving concurrent hypoxia and acidification. During photosynthesis, Symbiodinium spp., the microalgal endosymbionts of cnidarians and other marine phyla, produce O2 and assimilate CO2 and thus potentially mitigate the exposure of the host to these stresses. However, such a role for Symbiodinium remains untested for noncalcifying cnidarians. We therefore contrasted the fitness of symbiotic and aposymbiotic polyps of a model host jellyfish (Cassiopea sp.) under reduced O2 (~2.09 mg/L) and pH (~ 7.63) scenarios in a full-factorial experiment. Host fitness was characterized as asexual reproduction and their ability to regulate internal pH and Symbiodinium performance characterized by maximum photochemical efficiency, chla content and cell density. Acidification alone resulted in 58% more asexual reproduction of symbiotic
polyps than aposymbiotic polyps (and enhanced Symbiodinium cell density) suggesting Cassiopea sp. fitness was enhanced by CO2-stimulated Symbiodinium photosynthetic activity. Indeed, greater CO2 drawdown (elevated pH) was observed within host tissues of symbiotic polyps under acidification regardless of O2 conditions. Hypoxia alone produced 22% fewer polyps than ambient conditions regardless of acidification and symbiont status, suggesting Symbiodinium photosynthetic activity did not mitigate
its effects. Combined hypoxia and acidification, however, produced similar numbers of symbiotic polyps compared with aposymbiotic kept under ambient conditions, demonstrating that the presence of Symbiodinium was key for mitigating the combined effects of hypoxia and acidification on asexual reproduction. We hypothesize that this mitigation occurred because of reduced photorespiration under elevated CO2 conditions where increased net O2 production ameliorates oxygen debt. We show that
Symbiodinium play an important role in facilitating enhanced fitness of Cassiopea sp. polyps, and perhaps also other noncalcifying cnidarian hosts, to the ubiquitous effects of ocean acidification. Importantly we highlight that symbiotic, noncalcifying cnidarians may be particularly advantaged in productive coastal waters that are subject to simultaneous hypoxia and acidification.
This study provides new and additional data on morphology and a phylogenetic analysis of the recently described species Pelagia benovici Piraino, Aglieri, Scorrano & Boero, 2014 from the Northern Adriatic (Mediterranean Sea). Comprehensive morphological analyses of diagnostic characters, of which the most significant are marginal tentacles anatomy, basal pillars, gonad pattern, subgenital ostia and exumbrellar sensory pits, revealed significant differences from the currently known genera Sanderia, Chrysaora and Pelagia in the family Pelagiidae. A phylogenetic analysis of mitochondrial genes (COI, 16S rRNA, 12S rRNA) and nuclear ribosomal genes (28S rRNA, ITS1/ITS2 regions), together with cladistic analysis of morphological characters, positioned Pelagia benovici as a sister taxon with Sanderia malayensis, and both share a common ancestor with Chrysaora hysoscella. Pelagia benovici does not share a direct common ancestor with the genus Pelagia, and thus we propose it should not belong to this genus. Therefore, a new genus Mawia, gen. nov. (Semaeostomeae : Pelagiidae) is described, and Pelagia benovici is renamed as Mawia benovici, comb, nov.
As part of the German Barcode of Life campaign, over 3500 arachnid specimens have been collected and analyzed: ca. 3300 Araneae and 200 Opiliones, belonging to almost 600 species (median: 4 individuals/species). This covers about 60% of the spider fauna and more than 70% of the harvestmen fauna recorded for Germany. The overwhelming majority of species could be readily identified through DNA barcoding: median distances between closest species lay around 9% in spiders and 13% in harvestmen, while in 95% of the cases, intraspecific distances were below 2.5% and 8% respectively, with intraspecific medians at 0.3% and 0.2%. However, almost 20 spider species, most notably in the family Lycosidae, could not be separated through DNA barcoding (although many of them present discrete morphological differences). Conspicuously high interspecific distances were found in even more cases, hinting at cryptic species in some instances. A new program is presented: DiS-tats calculates the statistics needed to meet DNA barcode release criteria. Furthermore, new generic COI primers useful for a wide range of taxa (also other than arachnids) are introduced.
Molecular analyses have increased knowledge of the number and distribution of morphologically cryptic species in the world’s oceans and, concomitantly, the identification of non-indigenous species (NIS). However, traditional taxonomy and accurate delimitation of species’ life histories and autecology lag far behind, even for the most widely distributed taxa such as the moon jellyfish Aurelia species complex. Here we analyse mitochondrial cytochrome c oxidase subunit I (COI) and nuclear 28S ribosomal DNA (28S) gene sequences to assign polyps, ephyrae, and medusae collected in the Mediterranean Sea to different phylogenetic species. We find evidence for three Aurelia species, none referable to the type species of the genus, A. aurita, and describe the anatomical, morphometric, and developmental variation within and between them. We identify A. coerulea and A. solida as established non-indigenous species (NIS) in the Mediterranean Sea. We describe A. relicta sp. nov., an endemic species currently unique to a population in the marine lake of Mljet (Croatia). These results demonstrate the usefulness of integrative approaches to resolve taxonomic uncertainty about cryptic species complexes, identify patterns of marine biodiversity, and recognize NIS in marine ecosystems.
For individuals living in environmentally heterogeneous environments, a key component for adaptation and persistence is the extent of phenotypic differentiation in response to local environmental conditions. In order to determine the extent of environmentally induced morphological variation in a natural population distributed along environmental gradients, it is necessary to account for potential genetic differences contributing to morphological differentiation. In this study, we set out to quantify geographic morphological variation in the moon jellyfish Aurelia exposed at the extremes of a latitudinal environmental gradient in the Gulf of Mexico (GoM). We used morphological data based on 28 characters, and genetic data taken from mitochondrial cytochrome oxidase I (COI) and nuclear internal transcribed spacer 1 (ITS-1). Molecular analyses revealed the presence of two genetically distinct species of Aurelia co-occurring in the GoM: Aurelia sp. 9 and Aurelia c.f. sp. 2, named for its divergence from (for COI) and similarity to (for ITS-1) Aurelia sp. 2 (Brazil). Neither species exhibited significant population genetic structure between the Northern and the Southeastern Gulf of Mexico; however, they differed greatly in the degree of geographic morphological variation. The morphology of Aurelia sp. 9 exhibited ecophenotypic plasticity and varied significantly between locations, while morphology of Aurelia c.f. sp. 2 was geographically invariant (i.e., canalized). The plastic, generalist medusae of Aurelia sp. 9 are likely able to produce environmentally-induced, " optimal " phenotypes that confer high relative fitness in different environments. In contrast, the non-plastic generalist individuals of Aurelia c.f. sp. 2 likely produce environmentally-independent phenotypes that provide the highest fitness across environments. These findings suggest the two Aurelia lineages co-occurring in the GoM were likely exposed to different past environmental conditions (i.e., different selective pressures) and evolved different strategies to cope with environmental variation. This study highlights the importance of using genetics and morphometric data to understand jellyfish ecology, evolution and systematics.
Scyphozoans of the genus Cassiopea (Cassiopeidae) are notable for their unusual benthic habit of lying upside-down with tentacles facing upwards, resulting in their common name, "upside-down jellyfish". In Australia, five named species of Cassiopea have been recorded from the tropical north. Cassiopea are frequently noted worldwide as invasive species and here, we report the first records of the genus and family from temperate eastern Australia on the basis of specimens collected from two widely separated coastal lakes, Wallis Lake and Lake Illawarra; these specimens represent southern range extensions of the genus by approximately 600 km and 900 km, respectively. Cassiopea from Lake Illawarra and Wallis Lake appear to represent different species, which we assign to C. ndrosia and C. cf maremetens, respectively, noting morphological discrepancies from published accounts.
An unfamiliar scyphozoan jellyfish species has been observed along the Mediterranean coast of Israel since 2003. Morphological characters such as the densely anastomosed radial canals and the stalked cupped appendages on the oral arms identified it as closely allied to Cotylorhiza. Comparison with the type of C. erythraea, collected over a century ago in the Suez Canal, shows close similarity. Molecular analyses based on the mitochondrial barcoding gene cytochrome oxidase sub unit I (COI) and 28S ribosomal DNA support its placement among the Cepheidae. This is the fifth-introduced scyphozoan species recorded along the Mediterranean coast of Israel. The presence of sexually mature specimens detected as far back as 2003, and the occurrence of the species in the past summer at sites nearly 90 kms apart, indicate the existence of widespread, established populations.
Cnidocyst nomenclature is based on the structure of the tubule and its armature as viewed in the light microscopy (LM). Investigations utilising optically improved LM and scanning electron microscopy have revealed some errors in the interpretation of the fine structure of tubules and armature of nematocysts. Categories of nematocyst have been modified, therefore, to incorporate observations made with new visualising techniques. Isorhizas are defined as nematocysts whose tubule is of uniform or nearly uniform thickness proximal to the midpoint, while b-mastigophores are nematocysts with a rod shaped encapsulated shaft and a prominent armature on the everted shaft. The category of amastigophores is retained but redefined as p-amastigophores for the V-shaped notch at the base of encapsulated shaft. The trirhopaloids are found to be similar to the birhopaloids. Mesobasic is redefined as an intermediate length of discharged shafts between micro-and macrobasic. Astomocnidae is redefined as entangling nematocysts and stomocnidae as penetrants.
We describe a new species of
Crambionella
,
C. helmbiru
, from central Java, Indonesia. The combination of the mean number of lappets per octant (14), presence of foliaceous appendages amongst frills on oral-arms, absence of tubercles on the velar lappets, proportion of terminal club length to oral-arm length (0.28), and the body colour distinguish this species from three previously described congeners. In addition, the analysis of partial sequences of the cytochrome c oxidase subunit I gene indicate substantial genetic differences from both
Crambionella orsini
and
Crambionella stuhlmanni
, supporting the validity of this new species. A combination of morphological and genetic approaches determined that the remarkable differences in exumbrellar colours observed in specimens are simply intra-specific variation. Surprisingly, this species has been commercially harvested for more than 20 years and is well-known to the local people in the region, yet it had remained unknown to science until this point. The commercial fisheries targeting this formerly unknown species are also described in detail.
Cyanea is a genus of large bloom-forming scyphozoans, including some of the most conspicuous representatives of megaplankton. Its taxonomy has been revised repeatedly throughout the last century due to the fact that most of the morphological characteristics of Cyanea species, such as color, structure of gastrovascular system and number of tentacles, may overlap greatly in different populations. Here, we report a new species of Cyanea, Cyanea tzetlinii sp. nov., from the White Sea, which is distinguishable from all previously described Cyanea species by an eye-spot-bearing bulb formed at the base of each rhopalium. This well-recognizable morphological characteristic is supported at the molecular level by a substantial genetic distance in mitochondrial (CO1: 9.6–10.6 %, 16S RNA: 3.1–3.5 %) as well as nuclear (ITS: 5.0 %, 18S RNA: 0.1 %) loci, making it the sister species to Cyanea capillata. Taking into account the young geological age of the White Sea and a substantial genetic divergence between C. tzetlinii sp. nov. and the nearest sister species, we suppose that C. tzetlinii sp. nov. has been advected to the White Sea from elsewhere and may also inhabit other Arctic seas. Past ecological studies in the White Sea and possibly in other Arctic Seas could have conflated C. tzetlinii sp. nov. with other species, which likely affected the analyses.
The genus Ciona is an interesting ‘taxonomic case’ because its evolutionary history and taxonomy have not yet been resolved completely. In this study, we present new findings, describing specimens of an unidentified Ciona species collected along the north-eastern coasts of Sardinia (Tyrrhenian Sea, Mediterranean Sea). Applying an integrative taxonomic approach, based on the joint examination of morphological and molecular traits, we identify these specimens as a new species, Ciona intermedia sp. nov. Morphological comparisons and peculiarities of the habitat first revealed that these Ciona specimens have intermediate characters compared with other Ciona species. Molecular characterization (based on three mitochondrial regions: two already used for discriminating Ciona cryptic species and a newly developed one) confirmed that our specimens could not be assigned to any previously molecularly-characterized species. Both molecular phylogenetic reconstructions and morphological data clearly indicate C. intermedia as sister clade of Ciona edwardsi. Our findings add further complexity to the taxonomy of Ciona, underlying the importance of an integrative taxonomic approach for the study of the evolutionary history of this enigmatic genus.
A new species of Chrysaora is described from five specimens collected off Turkey in the Eastern Mediterranean Sea during December 2018. The species is characterised by its pale exumbrella, milky to creamy in colour, bearing faint and narrow markings, strap-like marginal tentacles, semi-rounded to tongue-shaped lappets, and a prominent dark spot on the exumbrella above each rhopalium. Analysis of the COI gene indicates that it may be most closely related to Chrysaora africana (Vanhöffen 1902), from which it is nevertheless 10.2 % different. It is unclear whether the species represents a previously undetected and endemic species from the Mediterranean, or whether source populations are located in the Red Sea and the northern Indian Ocean.
The upside-down jellyfish Cassiopea is a benthic scyphozoan, considered a non-indigenous invasive species in the Mediterranean, forming large blooms in eutrophic areas. Taxonomy of the genus Cassiopea is extremely difficult because morphological/meristic characters used are variable within the same species, overlapping among different species, and cryptic species have been identified by molecular markers; nine Cassiopea species are recognized on the basis of molecular study. Mediterranean records of Cassiopea have been ascribed to andromeda species on the basis of a hypothesized invasion pathway from the Suez Canal. In the current study, an analysis of the main morphological characters of the sampled Cassiopea jellyfish from Palermo (Tyrrhenian Sea) was carried out and subsequently, molecular analyses were performed by using COI barcode in order to identify the species. Molecular data were compared with published information in GenBank. Morphological characters were highly variable, but molecular analyses confirmed that Mediterranean Cassiopea specimens belong to andromeda species. Moreover, high values of sequence divergence were found between Mediterranean Cassiopea and the other C. andromeda from the Red Sea, Hawaii and Florida. These results lead to a discussion of possible explanations linked to life history features of the species. Two different explanations are proposed; the first is that Mediterranean C. andromeda , finding a suitable ecological niche good for colonization and proliferation, could have been isolated in Palermo Harbour. The second considers the possibility of multiple introduction events by human transport as demonstrated for other non-indigenous jellyfish; in this case Cassiopea genetic differences increased in the invaded area.
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.
The »World Atlas of Jellyfish« presents in a lavishly illustrated multi-author compendium the more than 260 species of medusae (Scyphomedusae and Cubomedusae) described so far. The general, first part deals with their structure, complex life cycles and rare fossil records. But it also details on collection, cultivation and fishery methods, even gives hints for photography and cooking recipes. Additionally, it covers the nature of medusae venoms, the effects and treatment of their stings. The second part gives concise systematic descriptions of all jellyfish species and their developmental stages known so far. Numerous illustrations, distribution maps, taxonomic keys and literature lists allow for detailed identification and information. Outstanding among the wealth of wonderful illustrations are hitherto unpublished artistic colour paintings by Ernst Haeckel. The beauty of the animals is underlined by the demanding typesetting of the book. This »Atlas« is a unique overview summarizing our knowledge on the world’s jellyfish in all their facets. It is of importance not only for scientists worldwide, but also a source of fascination for divers and lovers of marine life. [AVAILABLE ONLY AS HARD COPY]
A new species of the Marphysa sanguinea group, M. iloiloensis n. sp. (Annelida: Eunicida: Eunicidae), is described from the Marine Annelids Hatchery of the Southeast Asian Fisheries Development Center, Aquaculture Department (SEAFDEC- AQD), Iloilo Province, Philippines. It represents the first record of this group in the Philippines. The new species is most similar morphologically to M. hongkongensa Wang, Zhang & Qiu, 2018, but can be distinguished from it by having fewer branchial filaments, a pair of faint eyes (absent in M. hongkongensa), and in slight differences in jaw morphology and chaetation. The embryos of the new species develop inside a jelly cocoon attached to the entrance of the adult burrow; this is the first time that egg-containing cocoons have been found in any species of the sanguinea-group. Phylogenetic analysis based on the mitochondrial gene cytochrome c oxidase subunit I (COI) revealed that Marphysa iloiloensis n. sp. is genetically distinct from all other analysed Marphysa species and forms a sister group to M. hongkongensa. A revised identification key to members of the sanguinea-group in Southeast Asia is provided.
Two new species of scyphozoan jellyfishes from tropical Australian waters are described. The first, Sanderia pampinosus, n. sp., from waters off northern Western Australia, represents the first record of the genus from Australia. It differs from its only other congener, S. malayensis Goette, 1886, in having: (1) almost double the number of gonadal papillae at about half the body size; (2) horseshoe-shaped gonadal rings; and (3) eradial tentacles that are flattened in the oral-aboral direction and have nematocyst clusters on all sides. The second species, Netrostoma nuda, n. sp., from the Great Barrier Reef region, has been erroneously identified in the past as N. coerulescens. Species distinctions in the genus rely on the number and relative position of warts or papillae on the central dome; in contrast, N. nuda lacks warts and papillae, and instead has a large gelatinous knob at the apex of the bell. A key to the species of Netrostoma is provided, along with a synoptic list of previous reports of scyphozoans in tropical Australian waters.
Jellyfish blooms might be driven by the alterations in seawater temperature (SWT) associated with climate change. The physiological responses of jellyfish to changing SWT, however, are poorly understood. Therefore, we asked the question: how do sudden changes (±6 °C) in SWT affect the physiological performance of the jellyfish Cassiopea sp.? We measured the changes in mitochondrial cellular respiration (i.e., in term of the electron transport system (ETS) activity), superoxide dismutase (SOD) activity, and lipid peroxidation (LPO) to assess the jellyfish's physiological performance. In acute treatments (2 h), ETS increased only in response to cooling (to 20 °C) while SOD remained unchanged. In response to chronic treatment (2 weeks), ETS, SOD and LPO increased, while body mass decreased in response to cold (20 °C). In contrast, the heat-treated (32 °C) jellyfish did not increase their metabolic demands nor show signs of oxidative stress (OS). Moreover, they gained body mass. Because chlorophyll-a remained unchanged in all chronic-treated jellyfish, the cold-induced OS is more likely due to cellular respiration, not photosynthesis. Overall, Cassiopea sp. seems more sensitive to decreases in SWT then to increases. Therefore, Cassiopea sp. might benefit from the future projected rises in SWT, which could result in increased population abundance and an expansion in geographic distribution. Overall, these finding add new physiological evidences on jellyfish tolerance and might be used as a framework for further studies aiming at better understanding of jellyfish physiology.
Jellyfish blooms are enigmatic, in part due to uncertainty surrounding the geographic extents of populations and underlying causes and effects of demographic change. We aimed to promote understanding of likely drivers of macromedusae blooms by addressing 2 questions about patterns of genetic diversity: (1) Do congeneric individuals found within the same large marine ecosystem (LME) comprise a single species? (2) Do congeneric individuals from different LMEs represent different species? We DNA-barcoded (cytochrome c oxidase subunit I) 804 specimens in 16 medusozoan genera across 32 LMEs. We calculated K2P pairwise sequence divergence between congeneric individuals and estimated geodesic distance between all sample locations within and between LMEs; additionally, we calculated pairwise ?ST among conspecific samples within LMEs. While LMEs reasonably served as a proxy for species in -76% of between- LME comparisons, LME boundaries did not match species boundaries in -24% of inter-regional comparisons. Moreover, -19% of within-LME comparisons showed cryptic species and -67% showed substantial intra-specific phylogeographic structure. The overall rate of mismatch of the scale of LMEs and the scale of genetic structure in macromedusae is likely >70%, because the barcoding and phylogeographic analyses employed here cannot yet distinguish even finer-scale ecologically important population structure. These results were mirrored in analyses using Longhurst's Biogeographical Provinces. Meroplanktonic species often were genetically structured on scales of 10s to 100s of km, though holoplanktonic species may be eurymictic across 1000s to 10000s of km. We also found tentative evidence of onshore-offshore, depth, and latitudinal trends in population structure. When studying the causes and consequences of jellyfish blooms, more accurate descriptions of genetic and geographic differentiation are crucial.
Cryptic species could represent a substantial fraction of biodiversity. However, inconsistent definitions and taxonomic treatment of cryptic species prevent informed estimates of their contribution to biodiversity and impede our understanding of their evolutionary and ecological significance. We propose a conceptual framework that recognizes cryptic species based on their low levels of phenotypic (morphological) disparity relative to their degree of genetic differentiation and divergence times as compared with non-cryptic species. We discuss how application of a more rigorous definition of cryptic species in taxonomic practice will lead to more accurate estimates of their prevalence in nature, better understanding of their distribution patterns on the tree of life, and increased abilities to resolve the processes underlying their evolution.
Species richness in the seas has been underestimated due to the combined challenges presented by the taxonomic impediment, delimitation of species, preponderance of cryptic species, and uneven sampling effort. The mismatch between actual and estimated diversity varies by region and by taxon, leaving open questions such as: are hotspots for well-known taxa also hotspots for poorly known taxa? We address these challenges and this question for shallow-water scyphozoan jellyfishes in the Tropical Eastern Pacific (TEP). We increased sampling effort at 34 coastal locations along the TEP, and combined analyses of four molecular markers and up to 53 morphological characters. We applied phylogenetic analyses under Bayesian and maximum likelihood frameworks, barcoding, and statistical multivariate analyses of morphological data to estimate species richness. Where only five Discomedusae were reported previously, we found a total of 25 species. Of these, 22 species are new to science, two are non-indigenous, and one is a previous record; the other four prior records had been misidentified. The new discoveries evince the need to evaluate the evolutionary relationships with neighbouring regions to understand fully the origins of jellyfish diversity in the TEP and will lead to revision of the systematics and taxonomy of Scyphozoa.
Our observations on scyphomedusae from selected Philippine embayments identified specific animals commensal with five species of rhizostome scyphomedusae, Acromitoides purpurus, Mastigias sp., Phyllorhiza punctata, Rhopilema hispidum and Versuriga anadyomene. Acromitoides purpurus medusae harbor the crab Charybdis feriata, the carangid fish Alepes djedaba and the poecilostomatoid copepod Paramacrochiron sp. The carangid A. djedaba was an associate of the blue morph of A. purpurus and Rhopilema hispidum in Panguil Bay. A black-pigmented Alepes sp. was found associated with burgundy A. purpurus medusae in Carigara Bay. Charybdis feriata juveniles are common commensals of all morphs of A. purpurus, R. hispidum and P. punctata medusae. Only the zooxanthelate Mastigias sp. lacked animal symbionts. We invoke the “meeting-point hypothesis” and the general theory of fish aggregation to floating structures to explain fish symbiosis with their medusan hosts. The invertebrate-medusa associations are attributed to feeding behaviors and predator avoidance by resident commensals. This study provides record of the poorly studied scyphozoan species and their association with animals in Philippine waters. Finally, we discuss the potential reasons why the golden spotted jellyfish, Mastigias sp., appears to lack animal commensals.
Do all animals sleep? Sleep has been observed in many vertebrates, and there is a growing body of evidence for sleep-like states in arthropods and nematodes. Here we show that sleep is also present in Cnidaria, an earlier-branching metazoan lineage. Cnidaria and Ctenophora are the first metazoan phyla to evolve tissue-level organization and differentiated cell types, such as neurons and muscle. In Cnidaria, neurons are organized into a non-centralized radially symmetric nerve net that nevertheless shares fundamental properties with the vertebrate nervous system: action potentials, synaptic transmission, neuropeptides, and neurotransmitters . It was reported that cnidarian soft corals and box jellyfish exhibit periods of quiescence, a pre-requisite for sleep-like states, prompting us to ask whether sleep is present in Cnidaria. Within Cnidaria, the upside-down jellyfish Cassiopea spp. displays a quantifiable pulsing behavior, allowing us to perform long-term behavioral tracking. Monitoring of Cassiopea pulsing activity for consecutive days and nights revealed behavioral quiescence at night that is rapidly reversible, as well as a delayed response to stimulation in the quiescent state. When deprived of nighttime quiescence, Cassiopea exhibited decreased activity and reduced responsiveness to a sensory stimulus during the subsequent day, consistent with homeostatic regulation of the quiescent state. Together, these results indicate that Cassiopea has a sleep-like state, supporting the hypothesis that sleep arose early in the metazoan lineage, prior to the emergence of a centralized nervous system.
Model-based molecular phylogenetics plays an important role in comparisons of genomic data, and model selection is a key step in all such analyses. We present ModelFinder, a fast model-selection method that greatly improves the accuracy of phylogenetic estimates by incorporating a model of rate heterogeneity across sites not previously considered in this context and by allowing concurrent searches of model space and tree space.
Cnidarians are considered ancestral metazoans and, therefore, are important taxa for studying animal evolution. However, little is known about the group’s genome size (C value), which is an important parameter in whole-genome sequencing. To address this issue, we measured the C values of 27 cnidarian species from Japan, using flow cytometry, and found that they ranged from 0.26 to 3.56 pg. Excluding the results for Agalma elegans and Physalia physalis (order Siphonophorae), which had the highest C values among the species included in the present study, the C values for the cnidarians were 0.26–1.49 pg. In particular, we found that hydrozoans possessed relatively large and wide-ranging C values, indicating that evolution within the group involved considerable gains or losses of genomic content. Overall, the C values reported in the present study could be valuable for whole-genome sequencing, using next-generation sequencers, and for future research in cytogenetics.
Molecular analyses have revealed many cryptic species in the oceans, often permitting small morphological differences to be recognized as diagnosing species, but less commonly leading to consideration of cryptic ecology. Here, based on analyses of three nuclear DNA sequence markers (ribosomal 18S, 28S, and internal transcribed spacer 1 [ITS1]), two mitochondrial DNA markers (cytochrome c oxidase subunit I [COI] and ribosomal 16S), and 55 morphological features, we revise the classification of the enigmatic jellyfish genus Drymonema. We describe a new scyphozoan family, Drymonematidae, elevating the previous subfamily Drymonemidae to accommodate three species: the type species D. dalmatinum from the Mediterranean region, for which we identify a neotype; the western South Atlantic species D. gorgo; and a new species, D. larsoni from the western Atlantic and Caribbean, which also is described here. This revision emphasizes the remarkable morphological disparity of Drymonematidae from all other scyphomedusae, including allometric growth of the bell margin distal of the rhopalia, an annular zone of tentacles on the subumbrella, and ontogenetic loss of gastric filaments. Anatomical innovations are likely functionally related to predatory specialization on large gelatinous zooplankton, most notably the phylogenetically younger moon jellyfish Aurelia, indicating evolution of the feeding niche in Drymonematidae. This family-level revision contributes to the growing body of evidence that scyphomedusae are far more taxonomically rich, their biogeography is a more detailed mosaic, and their phenotypes are more nuanced than traditionally thought. Ecological and evolutionary responses to environmental change, past or future, are likely to be commensurately diverse.
Scientific enquiries into jellyfish blooms and associated problems are often deterred by the lack of taxonomical and ecological studies worldwide. Taxonomic difficulty is attributed to the high degree of morphological variations among and within species. To date, only two scyphozoan jellyfish species have been documented from field surveys in Malaysian waters, whereas another four Malaysian scyphozoan and two cubozoan jellyfish species have been mentioned in toxicological studies. None of these species have, however, been verified. This study thus aimed to document and resolves the uncertainty of earlier identified species in the region using morphology and molecular DNA sequencing. Jellyfish specimens were collected from Malaysian waters in the Straits of Malacca, South-China Sea and the Sulu-Sulawesi Sea over two years (June 2008 to October 2010), and their DNA sequences were compared with those from the Atlantic and Pacific regions. Ten scyphozoan and two cubozoan species were recorded in Malaysian waters (South China Sea and Straits of Malacca). These jellyfish included eight species from the order Rhizostomeae (Rhizostomatidae, Lobonematidae, Mastigiidae, Catostylidae and Cepheidae), two species from Semaestomeae (Pelagiidae and Cyaneidae) and two species from class Cubozoa; one from order Carybdeida (family Carukiidae) and another from order Chirodropida (family Chiropsalmidae). Molecular identification of species using phylogenetic approaches was based on DNA sequences of partial cytochrome oxidase I (COI), 16S and internal transcribed spacer (ITS1) regions. The COI phylogenetic tree of Cubozoa and Scyphozoa species from the Atlantic and Pacific regions showed distinct clustering of six Malaysian jellyfish species. However, most of the deeper divergences and relationships between the families were unresolved, which were also observed in the 16S and ITS1 phylogenetic trees. The Malaysian edible species Lobonemoides robustus, Rhopilema hispidum and Rhopilema esculentum were grouped within Rhizostomeae, whereas other scyphozoans showed phylogenetic affinities to Semaestomeae and Kolpophorae. Chrysaora and Cyanea appeared non-monophyletic, however their paraphyly was not confirmed. This study has provided the much needed baseline information on the taxonomy of Malaysian jellyfish species which have been substantiated by partial COI, 16S and ITS1 sequences. A total of 12 putative species of jellyfish were identified, which encompassed 12 genera.
Upside-down jellyfish (genus
Cassiopea
) can be found in tropical coastal waters worldwide. Until now reports of the genus from Brazilian waters have been scant. We report here medusae and scyphistomae collected from Cabo Frio, Rio de Janeiro state. Although we could not unambiguously identify the material using morphological criteria, genetic sequence data (COI) indicate that the Brazilian jellyfishes are genetically similar to those from Bermuda, Hawaii and Florida, which are related to specimens from the Red Sea (
Cassiopea andromeda
). We hypothesize that the presence of
C. andromeda
in Brazil is due to an invasion event, as the scyphistomae were found growing over the known invasive ascidian
Styela plicata
. Estimation of divergence time between Brazil (Cabo Frio) and Florida/Bermuda populations is that it occurred at the beginning of ship movement to South America.
Evolutionary inference can be complicated by morphological crypsis, particularly in open marine systems that may rapidly dissipate signals of evolutionary processes. These complications may be alleviated by studying systems with simpler histories and clearer boundaries, such as marine lakes—small bodies of seawater entirely surrounded by land. As an example, we consider the jellyfish Mastigias spp. which occurs in two ecotypes, one in marine lakes and one in coastal oceanic habitats, throughout the Indo-West Pacific (IWP). We tested three evolutionary hypotheses to explain the current distribution of the ecotypes: (H1) the ecotypes originated from an ancient divergence; (H2) the lake ecotype was derived recently from the ocean ecotype during a single divergence event; and (H3) the lake ecotype was derived from multiple, recent, independent, divergences. We collected specimens from 21 locations throughout the IWP, reconstructed multilocus phylogenetic and intraspecific relationships, and measured variation in up to 40 morphological characters. The species tree reveals three reciprocally monophyletic regional clades, two of which contain ocean and lake ecotypes, suggesting repeated, independent evolution of coastal ancestors into marine lake ecotypes, consistent with H3; hypothesis testing and an intraspecific haplotype network analysis of samples from Palau reaffirms this result. Phylogenetic character mapping strongly correlates morphology to environment rather than lineage (r = 0.7512, p < 0.00001). Considering also the deeper relationships among regional clades, morphological similarity in Mastigias spp. clearly results from three separate patterns of evolution: morphological stasis in ocean medusae, convergence of lake morphology across distinct species and parallelism between lake morphologies within species. That three evolutionary routes each result in crypsis illustrates the challenges of interpreting evolutionary processes from patterns of biogeography and diversity in the seas. Identifying cryptic species is only the first step in understanding these processes; an equally important second step is exploring and understanding the processes and patterns that create crypsis.
Nematocyst types of Cassiopea andromeda were investigated. Medusae samples were taken from Güllük Bay, Muğla, Turkey. Nematocyst samples from oral arms of C. andromeda were observed on LM and photographed. Birhopaloid and a-isorhiza nematocyst types were found in C. andromeda. Moreover, it was seen that nematocyst sizes increased with increasing the bell diameters of the individuals. Also, the venom of the species were isolated and injected intramuscularly to Cyprinus carpio juveniles. Partial paralysis, raking, inability to move the fins, and death were observed in the juveniles consequently. This study is a preliminary work on nematocysts and venom of C. andromeda. Further studies on neurotoxic effects of nematocyst venoms of this species should follow. Up until this study, there were no studies done on this subject in Turkey. Thus, this is the first time in Turkey the results were obtained from C. andromeda which is the lessepsian species entered the Suez Canal.
Haplotype networks are an intuitive method for visualising relationships between individual genotypes at the population level. Here, we present popart, an integrated software package that provides a comprehensive implementation of haplotype network methods, phylogeographic visualisation tools and standard statistical tests, together with publication-ready figure production. popart also provides a platform for the implementation and distribution of new network-based methods – we describe one such new method, integer neighbour-joining. The software is open source and freely available for all major operating systems.
Our investigations on different developmental stages of the jellyfish Cassiopea andromeda (Forskål, 1775) provide updated descriptions of nematocyst types and asexual reproduction modes, which were documented by drawings and high-resolution photographs. In contrast to previous studies that only described three types of nematocysts, we revealed five types: a-isorhizas, O-isorhizas, euryteles, large oval birhopaloids, and small lemon-shaped birhopaloids. Comparisons of undischarged and discharged capsules revealed significantly smaller capsule volumes (48-51 %) in the latter. We provide capsule lengths and widths ranges for each capsule type (undischarged) and developmental stage. We demonstrate that for most capsule types the calculated capsule volumes were positively correlated with the progressing development and increasing size of the five developmental stages, namely bud, polyp, strobila, ephyra, and medusa. O-isorhizas were only present in the latter three stages probably due to a change in diet related to a changing life style. Besides asexual reproduction by swimming buds and monodisc strobilation common in rhizostome Kolpophorae, we documented lateral polyp budding for the first time in this taxon. Our results demonstrate that cultivating living specimens facilitate detailed descriptions of nematocysts and reproductive modes in metagenetic cnidarians, which cannot be achieved by studies on preserved material.
The present-day global maximum for marine biodiversity has been located in Southeast Asia since at least the earliest Miocene. The history of biota in the region has been inferred from the present-day biogeography and phylogeny of extant organisms, but these analyses do not provide adequate tests of the various hypotheses proposed for the origins of the
diversity hotspot. The papers in this special issue present the results of an interdisciplinary research project designed to reconstruct the history of shallow marine biota and habitats within the hotspot and help understand the ecological context responsible for the maintenance of the diverse regional biota. A series of remarkably complete and fresh exposures were studied from the Kutai Basin (East Kalimantan, Indonesia) that included thick lower to upper Miocene sections of deltaic and marine sediments including abundant and extremely well preserved fossils. New stratigraphic and environmental frameworks allowed comparison of biota from habitats ranging from shelf-edge reefs to nearshore shallow seagrass meadows and coral carpets. Diversity was overall high throughout the interval, especially when compared to diversity in similar modern turbid mixed
carbonate-siliciclastic settings. This points to the previously unrecognized importance of these mesophotic habitats for the development of the diverse reef-associated communities in the modern-day hotspot.