Geographic Range

Biogeographic Regions

nearctic 

 

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  native 
  

 

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  palearctic 
  

 

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  native 
  

 

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  oriental 
  

 

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  native 
  

 

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  ethiopian 
  

 

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  native 
  

 

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  neotropical 
  

 

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  native 
  

 

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  australian 
  

 

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  native 
  

 

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  antarctica 
  

 

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  native 
  

 

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  arctic ocean 
  

 

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  native 
  

 

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  indian ocean 
  

 

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  native 
  

 

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  atlantic ocean 
  

 

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  native 
  

 

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  pacific ocean 
  

 

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  native 
  

 

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  mediterranean sea 
  

 

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  native 
  

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  Other Geographic Terms
  
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  holarctic 
  
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  cosmopolitan
  

Habitat

Ctenophores are exclusively marine animals. They may be found from coastal areas to open waters and are most typically planktonic, from surface waters down to 2,000 to 3,000 meters. A few species are epibenthic or benthic, and may be found in warm waters or on deep, cold, ocean floors; these are often found in association with echinoderms, cnidarians, or sponges. (Brusca and Brusca, 2003; Mills, 2010; Waggoner, et al., 2006; Wrobel, 2012)

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  Habitat Regions
  
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  temperate 
  
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  tropical 
  
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  polar 
  
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  saltwater or marine
  

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  Aquatic Biomes
  
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  pelagic 
  
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  benthic 
  
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  reef 
  
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  oceanic vent 
  
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  coastal 
  
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  abyssal
  

Systematic and Taxonomic History

Evolutionary relationships within Ctenophora are largely unresolved. Based on morphological and molecular analyses there is at least one polyphyletic order within phylum Ctenophora, Cydippida. The relationships of ctenophores to other metazoan phyla remain an open question, with different analyses alternately finding sister lineage to cnidarians, bilaterians, a clade containing cnidarians, placozoans, and bilaterians, or to all other animal phyla. (Dunn, et al., 2008; Harbison, 1985; Podar, et al., 2001; Ryan, et al., 2010)

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  Synapomorphies
  

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  biradial symmetry
  
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  eight rows of fused ciliary bands (ctenes)
  
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  presence of colloblasts
  
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  aboral sense organ
  
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  cydippid larva (lacking in beroid sp.)
  

Physical Description

Comb jellies have a wide variety of body shapes, from small, roughly spherical species of less than a centimeter in diameter, to flattened, ribbon-shaped forms that reach lengths of up to two meters. They are of biradially symmetrical and acoelomate. Most ctenophores are colorless, but some deep sea species are highly pigmented (often colored similarly to the invertebrates with which they are associated). It was once assumed that all ctenophores are bioluminescent; however, recent research shows that some species (members of genus Pleurobrachia for example) are not capable of producing light. Bioluminescent ctenophores produce calcium-activated phytoproteins. (Brusca and Brusca, 2003; Haddock and Case, 1995; Mills, 2010)

Body shape and robustness is directly related to the environment in which a species lives. Coastal species need to be tougher to withstand the force associated with wave motions, while pelagic species are often very fragile. Species in order Cydippida are typically round or oblong, with small (less than 3 cm in diameter), solid bodies. They have two tentacles used for capturing prey, which are usually branched. Species in order Lobata are generally larger than cydippids, and have expandable, sticky oral lobes used for capturing prey. The lobes have small tentacles within them. Members of order Beroida have cylindrical or flat, sac-like bodies, which open to engulf prey. Ctenophores of order Platyctenida are benthic organisms and most resemble sea slugs, but have branched feeding tentacles, similar to those of cydippids. (Brusca and Brusca, 2003; Mills and Haddock, 2007; Mills, 2010; Wrobel, 2012)

Ctenophore bodies are composed of two layers of epithelial tissue: an outer epidermis and inner gastrodermis. These sandwich the mesoglea, a jelly-like layer of mesenchymal tissue. True muscular cells, arranged in longitudinal and radial fibers, are found within the mesenchyme and provide the majority of support to the body and assist in movements associated with feeding. At some point in the life history of all comb jelly species (usually at all stages), the outer body bears eight plates of long, fused cilia, called “ctenes". These ciliary bands are the primary means of locomotion, and their beating is coordinated by an apical sense organ containing a calcareous statolith. In species with tentacles, these structures are armed with colloblasts, cells that discharge adhesive substances to aid in subduing prey. (Brusca and Brusca, 2003)

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