14 Difference Between Sea Slug and Sea Cucumber with Similarities

What is the difference between a sea slug and a sea cucumber?

Telling the difference between invertebrates is a daunting experience. Sea slug and sea cucumber fall in this category. But there are some hidden morphological features that can help to tell the differences.

The main difference between sea cucumber and seal slug is that the former is a type of gastropod that belongs to the phylum Mollusca whereas the latter belongs to the class Holothuroidea under the phylum Echinodermata.

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Comparison Table (Sea Slug and Sea Cucumber)

Basic Terms Sea Slugs Sea Cucumbers
DescriptionIt is a shell-less marine mollusk that comes with bright colors and a few appendages on the upper surfaceIt is an echinoderm with a thick worm-like body that has tentacles around the mouth and rows of tube feet along the body
TaxonomyPhylum MolluscaPhylum Echinodermata
Related toClams and oysterSea stars and sea urchins
Number of species1781250
Length40cm20cm
ColorationEnormous colorationVaries from the brow, black to the olive green
SkinSoft skinSpiny skin
HeadDefined headUndefined head
DietSeaweeds, sea lettuces, fish, starfish, crabs, seahorsePlankton, detritus, algae, or waste materials
RespirationSkin or naked gillsRespiratory trees
CommunicationChemical signalsHormonal signals
ReproductionHermaphroditeEither sexually, asexually, or regeneration
LifespanUp to 1 years2-5 years
ExamplesChromodoris annae, Dendronotus frondosus, and Acanthodoris pilosaChocolate-chip sea cucumber, Apostichopus japonicus, Holothuria scabra, black sea cucumber

What Is a Sea Slug?

Difference Between Sea Slug and Sea Cucumber

It is a marine invertebrate that look-like a terrestrial slug. It is also known as nudibranch and ocean’s butterfly. The creature lives in a water reef and belongs to the phylum Mollusca.

The sea slug is shellless and has a bilateral symmetry body. Organs occur in the coelom and sensory organ on the head. Muscular foot enhances locomotion.

These creatures have soft skin that is brightly colored. Sea slugs have the capability of detecting light and darkness. They breathe through the skin or naked gills.

Sea slug examples include Chromodoris Annae, Dendronotus Frondosus, and Acanthodoris Pilosa. The invertebrate feeds on seaweeds, sea lettuces, fish, starfish, crabs, seahorses, etc.

What Is a Sea Cucumber?

Difference Between Sea Slug and Sea Cucumber

It is a soft-bodied invertebrate that lives in shallow waters and others in the depth of ocean bottom. The invertebrate belongs to the phylum Echinodermata and class Holothuroidea.

The sea cucumber has a leather-like appearance and varied in color. The most common colors associated with sea cucumber are black, brown, and olive green.

The endoskeleton occurs below the skin with calcified structures. The creatures have undefined heads and lack brains.

Sea cucumber examples are Apostichopus japonicus, Holothuria scabra, black sea cucumber, etc. The invertebrates feed on plankton, detritus, algae, or waste materials.

Main Difference between Sea Slug and Sea Cucumber

  1. Sea slug belongs to the phylum Mollusca and sea cucumber belongs to phylum Echinodermata.
  2. The number of species of sea slug is 178 and those of sea cucumber is about 1250
  3. Sea slug reaches 40cm while sea cucumber reaches 20 cm
  4. Sea slug have enormous coloration while sea cucumber is black, brown, or olive green
  5. Sea slugs have soft skin while sea cucumbers have spiny skin
  6. Sea slugs have a defined head while sea cucumbers have an undefined head
  7. Sea slugs use the chemical signal for communication while sea cucumbers use hormonal signals

Similarities between Sea Slug and Sea Cucumber

  1. Both have tentacles
  2. Have reduced internal skeleton
  3. Dwell at the bottom of the sea
  4. Have bilateral symmetry body
  5. Have variable size, shape, and colors
  6. Both are marine invertebrates

In Conclusion

Sea slug is a soft-bodied invertebrate with enormous coloration and sea cucumber is a marine invertebrate with a spiny skin. The core difference between sea cucumber and sea slug is based on their taxonomy and physical features.

More Sources and References

  1. https://en.wikipedia.org/wiki/Sea_slug
  2. https://en.wikipedia.org/wiki/Sea_cucumber

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