Invertebrate.

 Animals that lack backbones are known as invertebrates. Over 98% of species on Earth are invertebrates that rely on other strategies than a backbone for support such as hydrostatic pressure, exoskeletons, shells, and in some, even glass spicules. Some invertebrate phyla have only one species, while others like Arthropoda include more than 83% of all described animal species with over a million species. The most common marine invertebrates are sponges, cnidarians, marine worms, lophophorates, mollusks, arthropods, echinoderms and the hemichordates.

Result:

SC - Sea cucumber
SU - Sea urchin
GC - Giant clam

For the invertebrates, the highest percentage abundance of invertebrates is sea cucumber with 77.78%, while the least percentage abundance is sea anemone with only 0.93%. The highest density of invertebrates is sea cucumber with 0.78%. The percentage abundance of sea urchin is lower than the sea cucumber which only 17.59% which indicates the coral reef area of the Pulau Kapas is good enough. But, the truth is not that good as the survey of coral cover state that the coral reef area is in poor and very poor condition. The sea urchin was used as indicator as it is one of the longest lived species. Due to their capability to respond to injuries, host invasion, and cytotoxic agents, coelomocytes which is in the coelomic cavity of sea urchin are regarded as the immune effectors of the sea urchin. In fact, coelomocytes react to challenges with modifications in their motility, increased phagocytic and encapsulation activities, and release of cytotoxic factors (Matranga 1996). The abundance of sea cucumber in this area might be because of their natural behaviour is actually live near rocks, corals or seaweed. Although the sea cucumber is a favourite food of large marine fish but sea cucumber in this area tend to be able to do several tricks such as thrown up their entire digestive system. This behaviour might be possessed for every single sea cucumber until its population reached the highest percentage abundance among the invertebrates.