“Worm” has numerous meanings, including: a weak or despicable person; a self-replicating, detrimental computer program; or, the coiled pipe of a still in which vapor is cooled and condensed. In this article, however, worm means a creeping or burrowing sedentary invertebrate animal with a long, slender, soft body and no true limbs. That description is unlikely to inspire you to look for marine worms, which would be a shame, because all are interesting and some are beautiful. 

The worms of which I speak are the tube worms within the group known as polychaetes. This article describes four commonly encountered while diving SoCal waters. They could also be named “the pop-up worms” for their habit of instantly disappearing down their tubes at the first hint of danger, only to reappear moments later, slowly unfurling their tentacular crowns, many of which come in a variety colors. The crowns are used for respiration and to capture food, so they are deployed a great deal of the time. When there is no current to bring them food, small species have another feeding mode. They extend their crowns as far as possible and sweep them over the area around them, searching for edibles.
According to the LA County Natural History Museum website: “The class Polychaeta consists of a very diverse group of segmented worms (unlike round worms or flatworms, which are not segmented) that live primarily in ocean habitats. The closest relatives of polychaetes are the earthworms and leeches, which comprise the class Clitellata, all of which are members of the phylum Annelida. Among the over 80 plus polychaete families and more than 10,000 described species there is an amazing array of body forms and sizes.”
The bodies of most annelids are composed of identical short segments (complete with organs such as kidneys and gonads). There is a head on one end, an anus/tail on the other. The sexes are separate in most polychaetes and they release eggs and sperm into the sea. The free-swimming larvae that hatch from the fertilized eggs have bodies ringed by a girdle of cilia. Once they settle down and morph into their final form, polychaetes grow by adding body segments. Some can regenerate heads and tentacles.
Polychaetes secrete one of two types of tubes, hard or soft. Of the four worms described here, the Christmas tree worm, a member of Serpulidae family, is the only one that produces a hard, calcareous tube. Two of the worms, the feather duster and Bispira turneri, belong to the Sabellidae family and produce soft tubes. Honeycomb tube worms are members of the Sabellariidae family and their tubes consist of sand grains cemented together.
Christmas tree worm (Spirobranchus spinosus): The name is apt; the tentacular crown consists of three circles with the largest at the bottom and the smallest at the top. These worms do, indeed, resemble a Christmas tree when seen from the side. While those found off our shores aren’t green, worms that color are found in tropical waters. My photos of SoCal Christmas tree worms include animals that are red, red and white, all white, yellow and blue. These are tiny worms with crowns only three-quarters of an inch wide and about an inch high. 
Christmas tree worms are found from Central California to Baja. They inhabit shallow waters, from the intertidal zone down to 40 feet.
Feather duster worm (Eudistylia polymorpha): These are among the largest tube worms found in SoCal waters and they come in three basic colors; orange, white and maroon. It’s not unusual to find all colors represented when several animals live close by. I chose a white feather duster for this article because black eyespots can be seen on the branches. According to A Living Bay, these compound eyespots are light sensitive and individuals may have as many as 240. Designed to detect the shadows of predators, they are exceptionally sensitive to motion.
Feather duster worms build soft but tough tubes that resemble parchment. When the animal retreats into the tube, the end collapses to close it. Feather dusters are among the polychaetes that are able to regenerate their heads and crowns.
A feather duster’s branches have tiny hairs (cilia) on them and are used for respiration and filtering food from the water. The cilia move food down the branches toward the mouth in the center.
Feather duster worms are found from Alaska to SoCal, from low intertidal waters to depths of about 130 feet. They seem to prefer colder, deeper waters than Christmas tree worms. Sites that are rich with feather duster worms include shipwrecks such as the Olympic, along with Begg and Wilson Rocks. 
Honeycomb tube worm (Phragmatopoma californica): These colonial worms build reefs on rocky bottoms with both water motion and fine sand nearby. Each two-inch worm constructs a tube about .157 inches in diameter by cementing grains of sand together. The tubes form a sturdy, honeycomb-like mass that can be more than six feet across. 
While some colonial marine animals (aggregating anemones, for example), can reproduce by cloning, honeycomb tube worms cannot. The reefs grow as free-swimming honeycomb larvae settle down on them.
Honeycombs have short, thread-like purple tentacles. They can retreat into their tubes and close them with an operculum. Since some honeycomb reefs are out of water at low tide, this very useful feature helps prevent predation and keeps the worms from drying out.
Honeycomb tube worms are found from Central California to Baja, from intertidal waters to depths of 240 feet.
The worm with no common name (Bispira turneri): The worm pictured with this article may or not be turneri. SoCal waters host a number of undescribed Bispira species, according to Leslie Harris, Manager of the LA County Natural History Museum’s Polychaetous Annelids Collection. Often, the only way to tell which is which of the described species is by an extensive examination of the animal, obviously not possible with a single photo. 
Says Harris, “The genus name, Bispira, comes from the Latin for two (bi) and spiral or coil (spira). These animals have crowns that are split into a left and right side. In many species there are only a small number of feathery branches on each side so the crown looks like a simple circle. Worms like Eudistylia have so many branches that the distinction between the two halves is obscured and they produce the big masses reminiscent of our feather dusters.” Bispira sperm is white, the eggs are usually pink, turquoise or green.
I’ve only photographed two Bispira; one off San Clemente Island and the other off Catalina.
The author wishes to acknowledge the continuing contributions of Genny and Shane Anderson. I could not do this column without their exceedingly generous help and expertise. 
Polychaete Stats
Phylum: Annelida 
Class: Polychaeta 
Subclass: Canalipalpata 
Order: Sabellida 
Family: Sabellidae 
(Bispira turneri, Eudistylia polymorpha)
(Phragmatopoma californica)
(Spirobranchus spinosus)
Reproduction: Sexual