The Cubozoa offer insight into the early evolution of vision.
From: Advances in Marine Biology, 2013
Related terms:
- Cnidaria
- Ctenophora
- Hydrozoa
- Scyphozoa
- Metamorphosis
- Actiniaria
- Freshwater
- Mitochondrial Genome
- Hydra
- Animalia
Biology and Ecology of Irukandji Jellyfish (Cnidaria: Cubozoa)
Lisa-ann Gershwin, ... Scott Condie, in Advances in Marine Biology, 2013
2.4.3 Visual evolution
The Cubozoa offer insight into the early evolution of vision. While the slit and pit eyes may provide visual information that the lensed eyes cannot, the lensed eyes nonetheless receive far more light and provide better spatial perception than the slit and pit eyes (Garm et al., 2008). And even though apparently out of focus, blurry images are better than no images (Nilsson et al., 2005). Garm and his colleagues (2011) proposed that having different eye types specialised for different visual tasks might require less neural processing than if the information for multiple behaviours were to pass through one eye.
Cubozoan behaviours (discussed in the succeeding text) suggest that at least some species are able to perceive colour, suggesting that the Cubozoa might represent early development of colour vision. O’Connor and her colleagues (2010) thought that colour vision can eliminate the brightness noise of flickering from surface ripple. Whether colour vision has allowed these animals to move into flickering coastal habitats, or whether living in coastal habitats selected for improved visual perception, is unclear.
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Development and Phylogeny of the Immune System
Thomas C.G. Bosch, in Encyclopedia of Immunobiology, 2016
Cnidaria as Model Systems in Comparative Immunology
The phylum Cnidaria is comprised of remarkably diverse andecologically significant taxa, such as the Anthozoa (reef-forming corals and sea anemones); swimming Scyphozoa (jellyfish); Cubozoa (box jellies); and Hydrozoa, a diverse group that includes all the freshwater cnidarians (such as the freshwater polyp Hydra) as well as many marine forms (Figure1). Cnidarians originated early in the history of metazoan evolution, as indicated by fossil evidence (Ausich and Babcock, 1998; Cartwright etal., 2007; Chen etal., 2002; Hagadorn and Waggoner, 2000; and Han etal., 2010) and molecular phylogenies (Dunn etal., 2008; Peterson etal., 2004; Peterson etal., 2008; Hejnol etal., 2009; and Park etal., 2012). Their early phylogenetic position as well as the diversity in cnidarian life histories (solitary vs colonial, sessile vs pelagic) and habitats (marine vs freshwater) raises several important issues relating to the origin of immunity. In the absence of protective layers such as cuticulae, Cnidarians must have effective mechanisms to defend against invading microbial pathogens. Moreover, successful growth means for many Cnidarian species to be able to distinguish between friends and foes, that is, to allow symbiotic algae to live within the endodermal epithelial cells and to close the doors for all other intruders. In addition, Cnidarians such as sea anemones and corals have extremely long life spans, were discovered to be more than 4200-years old (Roark etal., 2009) – and, therefore, must have some very effective immune systems in order to assure longevity. How do Cnidarians interact so successfully with their environment? How did the cross-kingdom communication systems between Cnidaria and microbes evolve?
Figure1. The early occurrence of Cnidaria on Earth. Members of different Cnidarian classes serve as models for studying the evolution of innate immunity and host–microbe interactions.
Although cnidarians have a long history as model systems in comparative immunology (Campbell and Bibb, 1970; DuPasquier, 1974, 2001), the underlying molecular mechanisms only recently have been uncovered. Results from Cnidaria genome projects in Nematostella (Putnam etal., 2007), Hydra (Chapman etal., 2010), and Acropora (Shinzato etal., 2011) have revealed that the genomes of these early emerging animals with their seemingly simple body plans are unexpectedly complex. They possess most of the gene families found in bilaterians and have retained many ancestral genes that have been lost in Drosophila and Caenorhabditis elegans (Kusserow etal., 2005; Miller etal., 2005; Technau etal., 2005; Schwaiger etal., 2014). In addition, Cnidarians have evolved rich epithelial defense mechanisms to cope with the variety of immunological challenges they encounter. Characterization of the innate immune repertoire of Cnidarians is, therefore, of both fundamental and applied interest – it not only provides insights into the basic immunological ‘tool kit’ of the common ancestor of all animals, but is also likely to be important in understanding human barrier disorders by describing ancient mechanisms of host–microbial interactions and the resulting evolutionary selection processes.
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Phylum Cnidaria
Fatma El-Bawab, in Invertebrate Embryology and Reproduction, 2020
Gonadogenesis
Cnidarian gonads are not distinct organs, but are merely massive assemblages of gametes in the interstitial spaces of the body tissue (diffused gonads). Interstitial cells which will be sperm or egg stem cell, accumulate each in its specific area of the column and become a gonad. In Hydrozoa, the gonads are ectodermal, while in Scyphozoan, Cubozoa, and Anthozoa, the gonads are endodermal in origin. No accessory cells of somatic origin participate in the formation of these gonads.
Grassi et al. (1995) studied gametogenesis in the strain ‘Scotland 1989’ Hydra vulgaris (Pallas, 1766), which is well identified by Campbell (1989). The obtained specimens were successfully mass-cultured in ‘finger bowls (260cm)’ at 14°C in artificial culture medium, by careful keeping and good feeding, the culture covers an observation period of 4years (1989–1993). During this time, two gametogenically active specimens (No. 1 and No. 2) bearing side by side testes and eggs (Fig. 5.6A (c)) were isolated from the mass-culture and kept individually in ‘wells (11cm)’ to observe their behaviour regarding budding and gametogenic activities. This work provided data for the condition of the polyps as well as numbers of buds, testes, oocytes, eggs, and many others. In fact, only there are the sites of stages of gametogenesis and bud formation in one sexual period (Fig. 5.6A) recorded.
The onset of each sexual period is characterized by the appearance of an initially small number of testes, which emerge as conical outgrowths mostly of the subtentacular body ectoderm (Fig. 5.6A (a1)), well before signs of oogenesis are apparent. On the other hand, the beginning of oogenesis is signalled by a patchy milky thickening of the polyp’s ectoderm within the middle region of the polyp’s body (Fig. 5.6A (b3)), and shortly afterwards by the formation of one or more polymorphic aggregates of interstitial cells (Fig. 5.6A (c4)).
The growth and gametogenesis of each gonad causes this portion of the tissue to bulge, stretch and eventually rupture to release the gametes. Hydrozoans release their gametes directly to the outside, whereas the other three cnidarian groups release their gametes into the gastric cavity and later expel them to the outside through the mouth.
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Phylum Cnidaria
Nadine C. Folino-Rorem, in Thorp and Covich's Freshwater Invertebrates (Fourth Edition), 2015
Introduction
General Features of the Phylum
Cnidarians are commonly known as sea anemones, corals, jellyfishes, and hydroids and are represented by more than 10,000 species in aquatic habitats around the world (Collins, 2009). Of these species, fewer than 40 occur in freshwater habitats (Jankowski etal., 2008). A given cnidarian life cycle may include two stages characterized by a particular body form: the polyp and the medusa (Figure 9.1). The polyp is typically sessile whereas the medusa is motile and is commonly known as a jellyfish. A unique feature of metazoan members of this phylum is that the body is diploblastic (consisting of two tissue layers), and consequently lacks well-developed organ systems. Between these two tissue layers is the mesoglea, a gelatinous matrix. The inner layer is the endoderm, often referred to as the gastrodermis; its primary function is digestion (Figure 9.2). The outer tissue layer, called the ectoderm or epidermis, includes cnidocytes—the distinctive diagnostic feature of the phylum. These specialized cells contain organelle-like structures called cnidae or cnidocysts that aid in prey capture, defense, and, in some instances, adherence to a substrate. Cnidocysts and the cnidocytes that house them exist as three types: nematocysts and nematocytes, spirocysts and spirocytes, and ptychocysts and ptychocytes. Nematocysts are the most familiar of the three cnidocysts. They are present throughout all classes, and the types, sizes, and shapes of cnidocyts (collective referred to as cnidome) are used in cnidarian taxonomy/systematics (Bouillon etal., 2006). Of the 30 types of nematocysts (Kass-Simon and Scappaticci, 2002; Fautin, 2009), only five or six are present in freshwater species; it not clear whether homotrichous microbasic euryteles occur in addition to heterotrichous microbasic euryteles (Figures 9.3 and 9.4).
FIGURE 9.1. Schematics of the two body forms present in the phylum Cnidaria: letter (a) represents the sessile polyp and letter (b) represents the motile medusa (Rupert etal., 2004).
FIGURE 9.2. A cross-section of Hydra representing the two tissue layers typical of Cnidaria, the outer epidermis and inner gastrodermis. The mesoglea is a gelatinous non-tissue layer between the two (Rupert etal., 2004).
FIGURE 9.3. Nematocyst types present in Cnidaria. Numbers 3, 6, 10 (possibly 18), 19, and 24 are present in freshwater organisms (Mariscal, 1974).
FIGURE 9.4. Nematocysts present in Cordylophora: (a) scanning electron micrograph of a discharged desmoneme (number 3 in Figure 9.3); notice the coiled tubule; (b) scanning electron micrograph of a discharged eurytele (number 18 or 19 in Figure 9.3); notice the capsule and spine-bearing tubule.
Courtesy of Abby Reft.General Systematics
Much effort has been devoted to clarifying the taxonomy of the phylum Cnidaria Verrill, 1865. A well-accepted approach defines two clades or groups, among which six classes are distributed (Daly etal., 2007). The first group is the single class Anthozoa, Ehrenberg, 1834, which includes the sea anemones and corals. The second group is the subphylum Medusozoa, Petersen, 1979, which encompasses the remaining five classes of cnidarians: Cubozoa Werner, 1975 (box jellyfish), Hydrozoa Owen, 1843 (hydroids), Polypodiozoa Raikova, 1988 (parasitic), Scyphozoa Götte, 1887 (true jellyfish), and Staurozoa Marques and Collins, 2004 (stalked jelly fish) (Jankowski etal., 2008; Raikova, 2008; Collins, 2009). Of these six classes, only Hydrozoa and Polypodiozoa contain genera that inhabit fresh water. The class Hydrozoa consists of two subclasses: Hydroidolina Collins, 2000 and Trachylina Haeckel, 1879. Among the three orders within Hydroidolina, the Anthoathecata Cornelius, 1992 (=Anthomedusae or Athecata) includes the majority of freshwater cnidarians. These freshwater representatives are classified in the genera Cordylophora Allman, 1944 and Hydra Linnaeus, 1758 (Cartwright etal., 2008). The subclass Trachylina is divided into four orders; within these orders, only the order Limnomedusae includes freshwater organisms. These representatives include Astrohydra Hashimoto, 1985, Calpasoma Fuhrmann, 1939, Craspedacusta Lankaster, 1880, and Limnocnida Dumont, 1976 (Collins etal., 2008) (Table 9.1). In current taxonomy, the family Olindiidae within the order Limnomedusae includes the genera Astrohydra, Calpasoma, Craspedacusta, and Limnocnida. However, similarities between the polyp stages of Astrohydra, Calpasoma, and Craspedacusta suggest that these three genera may be synonymous (Jankowski, 2001; Lewis etal., 2012). Astrohydra and Calposoma each have one known species. There are three species for Limnocnida and several (8–11) species are suggested for Craspedacusta (Bouillon etal., 2006; Zhang etal., 2009). The resolution of these species designations awaits additional research along with more morphological and molecular analyses of worldwide samples. Despite recent and thorough efforts to clarify taxonomic schemes for the Cnidaria, ambiguities still exist. As morphological and molecular information continue to become available, taxonomic revisions are likely to occur throughout the phylum and especially within the class Hydrozoa (Schuchert, 2010).
TABLE 9.1. A Summary of Taxonomy and Associated Nematocyst Types (If Available in the Literature) for Freshwater Cnidaria
| Subclass | Order | Family | Genus | Species | Nematocyst Type |
|---|---|---|---|---|---|
| Trachylina | Limnomedusae | Olindiidae | Astrohydra (Hashimoto, 1981) | japonica | Unknown |
| Trachylina | Limnomedusae | Olindiidae | Calposoma (Fuhrmann, 1939) | dactylopterum | Heterotrichous microbasic eurytele |
| Hydroidolina | Anthoathecata | Oceaniidae or Clavidae or Cordylophoridae | Cordylophora (Pallas, 1771) | caspia japonica mashikoi solangiae | Desmonemes microbasic euryteles |
| Trachylina | Limnomedusae | Olindiidae | Craspedacusta (Lankaster, 1880) | chuxiogensis iseana sowerbii sinensis vovasi | Heterotrichous microbasic euryteles |
| Hydroidolina | Anthoathecata | Hydridae | Hydra (Linnaeus, 1758) | 12–15 Species | Desmonemes, stenoteles, holotrichous isorhizas, atrichous isorhizas |
| Trachylina | Limnomedusae | Oliandiidae | Limnocnida (Günther, 1893) | indica nepalensis tanganicae | Microbasic euryteles |
| Hydroidolina | Anthoathecata | Bougainvillidae | Velkovrhia (Matjašic & Sket, 1971) | enigmatica | Desmonemes microbasic euryteles |
| Undecided | Undecided | Polypodiidae | Polypodium (Ussov, 1885) | hydriforme | Atrichous isorhizas holotrichous isorhizas |
All representatives listed are in the class Hydrozoa with the exception of Polypodium hydriforme in the class Polypodiozoa (Bouillon etal., 2006; Daly etal., 2007; Evans etal., 2008; Zhang etal., 2009; Calder, 2010; Schuchert, 2004, 2010).
Within the order Anthoathecata, the designated family name for Cordylophora is being evaluated. The names of Oceaniidae Eschscholtz, 1829, historically accurate Cordylophoridae von Lendenfeld, 1885, and Clavidae McCrady, 1859 have been used. Using Oceaniidae is provisional until more morphological and molecular data are available to clarify family status (Calder, 2009, personal communication; Schuchert, 2009, personal communication). Species delineation for Cordylophora also needs clarification. Lack of species consensus resulted in part from the high degree of morphological plasticity among Cordylophora populations and erroneous identification in taxonomic history. Previous taxonomic reclassifications recognize four Cordylophora species: caspia, japonica, mashikoi, and solangiae (Folino-Rorem, 2009). However, recent molecular findings support the existence of multiple species of Cordylophora based on their occurrence in freshwater versus brackish habitats (Folino-Rorem etal., 2009).
Likewise, clarification of species in the genus Hydra within the family Hydridae requires attention. Campbell (1987) established four groups within the genus based on nematocysts and morphology. These groups—“vulgaris,” “oligactis,” “braueri,” and “viridissima”—currently provide a basis for delineating the probable 12–15 species of Hydra (Martínez etal., 2010; Schuchert, 2010).
The endoparasite Polypodium hydriforme is the sole representative in the class Polypodiozoa. As previously mentioned, the status of this organism in the phylum Cnidaria is still under debate and therefore, more work is needed to clarify its taxonomic status (Table 9.1).
Phylogenetic Relationships
The phylogenetic relationships within the phylum Cnidaria are still in flux. Collins (2009) presented the most recent hypothesis of Cnidarian phylogeny (Figure 9.5). Cnidaria diverged early in the metazoan lineage during the Ediacaran period and are most closely related to Bilateria (Collins, 2009). The phylum is monophyletic, and the establishment of phylogenetic relationships revolves around cnidae and life cycles, specifically with regard to whether the medusa or polyp body form was more basic or primitive. An accepted evolutionary scenario is that the anthozoans are the most primitive, holding a basal position in the phylum compared with the other classes. This approach supports the polyp-first or polypoid ancestor hypothesis, with the Anthozoa being one of two monophyletic clades: (class) Anthozoa and (subphylum) Medusozoa. Therefore, this supports the evolution of freshwater cnidarians from marine ancestors (Bridge etal., 1992; Daly etal., 2007). Within the sister taxon Medusozoa Petersen, 1979, five of the six Cnidaria classes are present; of these five classes two, the Hydrozoa and Polypodiozoa, contain freshwater representatives (Raikova, 2008; Collins, 2009; Cartwright and Nawrocki, 2010). Among the five classes, the Cubozoa and Scyphozoa are more closely related, relative to the class Hydrozoa. The Hydrozoa are more closely related to the classes Scyphozoa and Cubozoa, whereas the Staurozoa and Anthozoa are most distantly related, respectively (Collins etal., 2006). Within the class Hydrozoa, there are two monphyletic clades or subclasses: Trachylina Haeckel 1879 and Hydroidolina Collins 2000 (Cartwright etal., 2008; Collins etal., 2008). Changes in the current taxa in both of these subclasses are anticipated as future work addresses morphological and molecular data (Collins, 2009).
FIGURE 9.5. A proposed phylogenetic scheme for the phylum Cnidaria. The classes of Polypodiozoa and Hydrozoa with the ∗ include freshwater Cnidaria (Collins, 2009).
The inclusion of the remaining class Polypodiozoa within the Medusozoa has been muddied by attempts to clarify the phylogenetic position of the Myxozoans, and is an interesting example of how thoroughness in assessing molecular data can be controversial. This class consists of the endoparasite Polypodium hydriforme, but more thorough molecular analyses are required to establish a more definitive phylogenetic status. At this point, the class Polypodioza is considered to be in the phylum Cnidaria (Raikova, 2008; Evans etal., 2008, 2010; Collins, 2009).
Distribution and Diversity
The majority of freshwater Cnidaria are global in distribution with the exception of a few regional locations for Polypodium hydriforme and Velkovrhia enigmatica (Table 9.2). The endoparasite Polypodium hydroforme is limited by its host’s distribution, although it may be more prevalent throughout fisheries than is currently known in Europe and North America. Velkovrhia enigmatica occurs in caves in Balkans and Slovenia (Zagmajster etal., 2011). Perhaps the distribution of these species is more prevalent and has yet to be documented.
TABLE 9.2. Global Distribution of Freshwater Cnidaria
| Biographic Region | Astrohydra | Calposoma | Cordylophora | Craspedacusta | Hydra | Limnocnida | Polypodium hydroforme | Velkovrhia enigmata |
|---|---|---|---|---|---|---|---|---|
| Afrotropical | + | − | + | + | + | + | − | − |
| Antarctic | − | − | − | − | − | − | − | − |
| Australasian | − | − | + | + | + | − | − | − |
| Indomalaya | − | − | + | + | + | + | − | − |
| Nearctic | − | + | + | + | + | − | + | + |
| Neotropical | − | − | + | + | + | − | − | − |
| Oceania | − | + | + | + | + | − | − | − |
| Palaearctic | + | + | + | + | + | − | + | + |
The negative sign means either the organisms do not occur in the region or there are no known published accounts at this time; a positive sign indicates the presence in that region (Rahat and Campbell, 1974a; Dumont, 1994; Jankowski, 2001; Jankowski etal., 2008; Folino-Rorem, 2009; Fritz etal., 2009; Calder, 2010; Martínez etal., 2010; Zagmajster etal., 2011).
In contrast, Hydra is cosmopolitan in distribution, although two of the three groups that include brown hydra (“vulgaris,” “oligactis,” and “braueri”) are restricted to the Northern Hemisphere: the “braueri” and “oligactis” groups (Martínez etal., 2010). The prevalence and distribution of Cordylophora, a euryhaline hydroid with established populations in both freshwater and brackish, have been underestimated and often overlooked because this cnidarian is often entangled in field collections with filamentous green algae or freshwater bryozoa (Folino-Rorem etal., 2009).
The medusae stages of Craspedacusta and Limnocnida, although unpredictable in appearance within the same locale from one year to the next, are much more conspicuous than the microscopic polyp stage. Species of Craspedacusta are distributed through the world, whereas species of Limnocnida are more limited in global distribution (Table 9.2). It is likely that the polyp stages for Astrohydra, Calpasoma, Craspedacusta, and Limnocnida are underreported owing to their small size, leading to infrequent discovery and potential sparse distribution records.
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First records and presence over time of the cubozoan Carybdea marsupialis (Linnaeus, 1758) on the southwestern Spanish coast (Northeast Atlantic)
C. Rodríguez-García, ... R. Cabrera-Castro, in Regional Studies in Marine Science, 2021
1 Introduction
The Cubozoa cnidaria class, named for its cube-shaped bells, includes two orders (Carybdeida and Chirodropida) of approximately 40–50 species found in the different oceans and seas on the planet (Bentlage et al., 2010; Kingsford and Mooney, 2013). These species are categorized into eight different families (Carybdeidae, Tripedaliidae, Tamoyidae, Carukiidae, Alatinidae, Chiropsellidae, Chirodropidae and Chiropsalmidae) and are all characterized by two body layers, four pedalia, one on each vertex of the bell, a velarium with gastric diverticula, and rhopalium with organs of balance (Bentlage and Lewis, 2012; Gueroun et al., 2015; Toshino et al., 2015). The orders Carybdeida and Chirodropida are similar in that they both have venomous species that cause or may cause death in humans (Gershwin et al., 2010; Bentlage and Lewis, 2012; Kingsford and Mooney, 2013), and their species prefer to inhabit sandy substrates (Santhanam, 2020) and have a similar diet composition based on crustaceans and small fishes (Nogueira-Junior and Haddad, 2008; Kingsford and Mooney, 2013; Santhanam, 2020). Regarding their geographical distribution, both orders cohabit the same geographical areas, upwelling areas with a similar temperature range, mainly tropical but also temperate according to the FAO area distributions (FAO, 2020). However, only species of the order Carybdeida are found in the Mediterranean (Kingsford and Mooney, 2013; Santhanam, 2020; Karunarathne and DeCroos, 2020). The characteristics that differentiate the two orders in their free-swimming phase are the number of tentacles per pedicle, the mode of fertilization, the location of nematocysts, the presence of gastric saccules, the size, and the number of families and species in each order (Southcott, 1996; Bentlage et al., 2010; Tahera and Kazmi, 2006; Kingsford and Mooney, 2013; Avila-Soria, 2009; Kramp, 1961; Bordehore, 2014; Garcia-Rodríguez et al., 2020) (Table1).
Table 1. Main differences between the existing cubozoa orders: Carybdeida and Chirodropida. BH: Bell Height.
| Characteristic | Carybdeida | Chirodropida |
|---|---|---|
| Familiesa,b,c | Five | Three |
| Speciesd | 31 | 10 |
| Sized,e | Lower average BH than Chirodropida (1–25cm) | Higher average BH than Carybdea (5–32.5cm) |
| Tentaclesf,g | One, simple o tripartite, per pedalia | Up to 15 per pedalia |
| Nematocystsg | In umbrella and tentacles | In tentacles |
| Stomach bagsf | Four without gastric saccules. | Four with eight gastric saccules. |
| Fertilizationb,h | Internal and External | External |
| Water Temperaturei | 17–35°C | 19–35°C |
| Distributioni | FAO Area: 27, 31, 34, 37, 47, 51, 57, 61, 71, and 77. | FAO Area: 31, 34, 47, 51, 57, 61, 71, and 77. |
Area 27 (Atlantic Northeast); Area 31 (Atlantic, Western Central); Area 34 (Atlantic, Eastern Central); Area 37 (Mediterranean and Black Sea); Area 47 (Atlantic, Southeast); Area 51 (Indian Ocean, Western); Area 57 (Indian Ocean, Eastern); Area 61 (Pacific, Northwest); Area 71 (Pacific, Western Central); Area 77 (Pacific, Eastern Central).
- a
- Southcott (1996).
- b
- Bentlage et al. (2010).
- c
- Tahera and Kazmi (2006).
- d
- Kingsford and Mooney (2013).
- e
- Avila-Soria (2009).
- f
- Kramp (1961).
- g
- Bordehore (2014).
- h
- Garcia-Rodríguez et al. (2020).
- i
- Data compiled by authors.
In addition to their ecological importance within the ocean’s food chains as predators, medusae can interfere with the development of important activities such as tourism, as some of their species possess a highly toxic venom that can cause death to bathers or divers (Kokelj et al., 1992; Rottini et al., 1995; Fernández-Rubio et al., 2012; Santhanam, 2020).
The species Carybdea marsupialis (Linnaeus, 1758) is a box-jellyfish belonging to the order Carybdeidae which is distributed in the tropical and subtropical waters of the Atlantic Ocean and the Mediterranean Sea (Kramp, 1961; Bordehore et al., 2011; Gueroun et al., 2015; Pulis, 2015). It has been observed sporadically in mass aggregations in the Adriatic Sea (Boero and Minelli, 1986; Mizzan, 1993; Giampiero et al., 1997; Bettoso, 2002; DiCamillo et al., 2006), as well as occasionally on the African and Spanish Mediterranean coasts (Bordehore et al., 2011; Gueroun et al., 2015), and is the only known species of box-jellyfish found in these areas (Acevedo et al., 2019) (Fig.1). Recently it has also been recorded in Portuguese Atlantic waters (Rodrigues et al., 2020). Carybdea marsupialis is an oviparous and bipartite species with a two-phase life cycle: 1 — polyp and 2 — pelagic (Cutress and Studebaker, 1973; Bordehore et al., 2011). In the polyp stage it lives fixed to the substrate and reproduces asexually to form the box-jellyfish which will go on to live in a pelagic form (Cutress and Studebaker, 1973; Bordehore et al., 2011, 2014). Bordehore et al. (2011) located this medusa species in Denia (East Spain) at depths between 0.5 and 1.2 m, whilst Gueroun et al. (2015) observed it at 1.3–2m depth on the coast of Tunisia.
Fig. 1. Distribution of published records of C. marsupialis throughout the Mediterranean, including observations made in the study area in the Atlantic margin. Each point represents recorded locations by different authors (represented by color). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 2. Carybdea marsupialis. (A) Representation of the measurements taken of the captured medusae, distinguishing certain morphological characteristics. (B) A example of medusa preserved in 70% ethanol. Scale bar 5mm.
Carybdea marsupialis plays an important role within marine food chains in very localized areas, exercising top-down control as a predator of zooplankton and ichthyoplankton (Larson, 1976; Nogueira-Junior and Haddad, 2008). Under this control, it is the abundance of the predator that will determine the abundance of the rest of the trophic links located below. Within this framework, a mass proliferation of C. marsupialis would exert greater pressure on the lower links, the zooplanktonic and ichthyoplanktonic communities, decreasing their abundance, causing an imbalance in the food chain and, therefore, a change in the dynamics of the ecosystem (Bordehore et al., 2011). A mass proliferation of this species could be detrimental both to the ecosystem and to the economic sector of coastal areas that are mostly dependent on tourism (Gueroun et al., 2015). Similarly, a massive increase in cubozoans on beaches could lead to their temporary closure as these species could seriously risk the health of bathers and divers due to their neurotoxic and hemolytic properties, which noticeably affect human red blood cells (Rottini et al., 1995; Sánchez-Rodríguez et al., 2006). In Australia, in the case of the species Chironex fleckeri, the authorities warn of its presence on beaches (Fernández-Rubio et al., 2012) and even prohibit bathing.
The aim of this paper is to describe the presence of C. marsupialis for the first time on different beaches of the Gulf of Cadiz. For this purpose, morphometric relationships, size distribution, and the relationship between abundance and water temperature were analyzed.
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Visual Acuity and the Evolution of Signals
Eleanor M. Caves, ... Sönke Johnsen, in , 2018
Although there are 10 recognized optical eye types [5], here we focus on camera and apposition compound eyes. Camera eyes are the principal eye type of vertebrates, although they are also found across some invertebrate taxa (gastropods, scallops, arachnids, cubozoa, alciopid polychaetes, and certain copepods) [5]. They comprise a single image-forming unit, an internal lens and a typically external cornea, that focuses an image onto a retina comprised of photoreceptor cells. Compound eyes are found across insects and crustaceans, as well as some chelicerates, annelids, and bivalve mollusks. Apposition compound eyes are comprised of multiple optical units, known as ommatidia, which are tubular structures consisting of at least one lens that funnels light to a group of photoreceptor cells.
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The jellyfish joyride: causes, consequences and management responses to a more gelatinous future
Anthony J. Richardson, ... Mark J. Gibbons, in , 2009
The Cnidaria comprise three main groups of jellyfish, all of which can pose problems to human health. Most species of the Class Scyphozoa, which includes the large, bell-shaped jellyfish commonly washed up on beaches, have a polyp stage that buds off small medusae. They are found in all pelagic environments, but attain greatest abundances near the coast. Approximately 200 species have been described. Jellyfish of the Class Cubozoa are cuboidal and most are fist size or smaller, although a few are much larger, such as the deadly Australian sea wasp Chironex, which has a polyp stage in its life cycle; however, unlike other cnidarians, the polyp develops into a single medusa without budding. There are ∼20 species, restricted to temperate and tropical shelf waters. Super-Class Hydrozoa is a diverse group that includes colonial siphonophores, such as the Portuguese-man-of-war Physalia. Most are thumbnail size and display both life-cycle stages, but in others the medusa or polyp is lost. Hydrozoa are found in all oceans and have 3700 described species.
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https://www.sciencedirect.com/science/article/pii/S0169534709000883