Hong Kong Corals & the Associated Marine Life

> Other marine organisms

Flatworms are most commonly known for their parasitic members including flukes (Class Trematoda) and tapeworms (Class Cestoda). Free-living flatworms (Class Turbellaria) are found in tropical shallow waters. They are the most spectacular members of the group and hence often confused with the nudibranchs.

Most free living flatworms feed on detritus or small invertebrates. They do not have gills for respiration. Oxygen is absorbed from the surrounding water by diffusion through the skin. Flatworms normally crawl on the bottom but they can swim by undulating their thin and flattened bodies.

Pseudobiceros  bedfordi  (Pseudocerotidae)

This distinctively colourful flatworm is one of the most common flatworms seen in Hong Kong and the Indo-Pacific. Sometimes, you may find them swimming in the water column with a beautiful, undulating motion. It mainly feeds on tunicates and crustaceans.

Phylum Annelida consists of three major groups that include terrestrial (e.g. earthworms), freshwater (e.g. leeches) and marine species (e.g. polychaetes). The distinguishing characteristic of an annelid is the segmented body. 

Annelid is divided into a linear series of similar segments from the head to the tail. Growth involves formation of a new segment anterior to the tail. The head bears sensory organs for processing environmental information.

Most of the polychaetes are marine dwellers. They are extremely abundant and widespread in the ocean. Many of them are benthic (e.g. bristle worms), while some are pelagic and tube-dwelling (e.g. fan-worms). With different body forms, polychaetes feed in different ways, such as deposit feeding, filter feeding and raptorial feeding.

Worms in families Serpulidae and Sabellidae are all tube-dwelling. The serpulid worms secrete calcareous tubes while the sabellids produce tubes of sand grains and organic matrices. Some species may have a modified tentacle for closing the tube.	Tubes of  Protula  magnifica  (Serpulidae)
Protula  magnifica  (Serpulidae)	This is one of the most distinctive feather-duster worms, having a calcareous tube that is white on the outside and bright red inside around the lip. It can be commonly seen on shallow coral communities.
The calcareousness of this feather-duster worm is about 2mm in diameter. It reproduces asexually into a colony.	Filogranella  elatensis  (Serpulidae)
Chloeia  flava  (Amphinomidae)	The brown markings on each segment of the body distinguish this fire worm from the others. The bristle feet are filled with venom, which will cause a burning pain when touched. It can be seen crawling along the sandy sea bottom in search of prey, or occasionally, swimming in the water column.