 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Spirobranchus giganteus" – news ·newspapers ·books ·scholar ·JSTOR(February 2018) (Learn how and when to remove this message) |
| Christmas tree worm | |
|---|---|
.jpg) | |
| S. giganteus onPorites | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Annelida |
| Clade: | Pleistoannelida |
| Clade: | Sedentaria |
| Order: | Sabellida |
| Family: | Serpulidae |
| Genus: | Spirobranchus |
| Species: | S. giganteus |
| Binomial name | |
| Spirobranchus giganteus | |
Spirobranchus giganteus, commonly known as theChristmas tree worm, is apolychaete worm belonging to the familySerpulidae building calcareous tubes. TheS. giganteus lives incoral reefs in theCaribbean.
.jpg)
Both its common and Latin names refer to the two chromatically hued spiral structures, the most common feature seen by divers. The multicolored spirals are highly derived structures for feeding and respiration.
Spirobranchus giganteus is similar to most tube-buildingpolychaetes. It has a tubular, segmented body of an approximate length of 3.8 cm (1.5 in)[2] covered withchaetae, small appendages that aid the worm's mobility. Because it does not move outside its tube, this worm does not have any specializedappendages for movement or swimming.
The worms' most distinct features are two "crowns" shaped likeChristmas trees. These are highly modifiedprostomial palps, which are specialized mouth appendages. Each spiral is composed of feather-like tentacles calledradioles, which are heavilyciliated and cause any prey trapped in them to be transported to the worm's mouth. While they are primarily feeding structures,S. giganteus also uses itsradioles for respiration; hence, the structures commonly are called "gills".
One major difference between Christmas tree worms and otherSabellida fan worms is that the latter do not have any specialized body structures to plug their tube holes when they withdraw into them.Spirobranchus giganteus, like many other members of its family, possesses a modified radiole that usually bears a plug called theoperculum, that it uses to secure its hole when withdrawn into its tube.
As anannelid,S. giganteus possesses a completedigestive system and has a well-developed closedcirculatory system. Like other annelids, these worms possess well-developed nervous systems with a central brain and many supportingganglia, includingpedal ganglia, unique to thePolychaeta.Spirobranchus giganteus has a faster mitochondrial sequence evolution than other annelids because of its nucleotide composition and divergence of protein sequences.[3] Like other polychaetes,S. giganteus excretes with fully developednephridia. When they reproduce, they simply shed their gametes straight into the water where the eggs and spermatozoa become part of thezooplankton to be carried by the currents.
Spirobranchus giganteus occur from the Caribbean to the Indo-Pacific.[1]
S. giganteus is commonly found embedded entirely in heads of massive corals, such as stony coralsPorites andbrain corals. Like members of its family, it can secrete acalcareous tube around its body. This tube serves as the worm's home and protection. Calcareous tube can reach up to 20 cm in length. They are usually deeply embedded in the coral skeleton.[4]S. giganteus usually settles onto an existing head of living coral before secreting its tube, thereby increasing its level of protection as coral tissue overgrows the calcareous tube. When the worm retreats into its tube, the opening is shut using an operculum, which is further protected by sharp, antler-shaped spines.[5]
Assedentary inhabitants of coral reefs, Christmas tree worms feed primarily byfilter feeding. They use their brightly colored radioles to filter microorganisms from the water, which are then deposited straight into the worm's digestive tract.
Few organisms are known to feed on tube-borne polychaetes andS. giganteus is no exception. The relationship betweenS. giganteus and its host corals is still poorly understood, but occasionally the movement of the operculum can abrade the coral tissue, and that mortality of the coral tissue is enhanced when the worm's operculum hosts filamentous algae.[6]
While the worm itself has no commercial fishery importance, it is of interest to marine aquarists and divers. The variously colored worm crowns make extremely popular underwater photographic subjects forsport divers. Manyaquarists who have miniature reef aquaria purposely include heads of coral thatS. giganteus specimens inhabit.[citation needed][7]
As the species is widespread and relatively common, no conservation efforts focus on this species (or polychaetes in general). This species was thought to be exclusively found in coralheads, however they have also recently been described asepibionts on the giant clam speciesTridacna squamosa in theGulf of Thailand.[8] The conservation status of the host species which it inhabits varies.
Spirobranchus essentially translates to "spiral branchia", referring to the worm's unique crown.
There are both male and female Christmas tree worms,Spirobranchus giganteus. They reproduce by casting their eggs and sperm into the water. The eggs are fertilized in the water then develop into larvae that settle on coral heads and then burrow into the coral to form their burrows.[9]
.jpg)
%2c_Anilao%2c_Filipinas%2c_2023-08-22%2c_DD_193.jpg)
