Phylum Kamptozoa

Classification

Kingdom: Animalia
Phylum: Kamptozoa
Order: Solitaria
Family: Loxosomatidae
Order Coloniales
Suborder: Astolonata
Family: Loxokalypodidae
Suborder: Stolonata
Family: Pedicellinidae
Family: Barentsiidae

General Information

The phylum Kamptozoa is also known as Entoprocta, with the two terms being used interchangeably. Common names are the nodders, because they tend to “bob” around on the end of their stalks, and goblet worms. The phylum encompasses two orders, four families, sixteen genera, and approximately 150 species. The invertebrates are sessile, with most species forming colonies, however solitary species do exist. Kamptozoa are acoelomate.

Distribution

Kamptozoa are mostly marine animals, with two known freshwater species. They are found in all the world’s oceans, ranging from the shallow intertidal zone to 500 m deep.

Ecology

Kamptozoa are found on a variety of substrata, including rocks, stones, shell remains, and man-made objects. Some species live on specific host animals, such as polychaetes, bryozoans, sponges, and other marine invertebrates. The organisms are food for small crustaceans and molluscs. Kamptozoa are the only prey of the nudibranch genus Trapania. For years it was thought the nudibranchs were feeding on the sponges they were associated with, but it is now know they were feeding on the kamptozoa which were living on the sponge.

Form

Kamptozoa average 1 mm in length but can range from 0.1 to 7 mm. The body consists of cup-shaped calyx and is supported by a slender, flexible stalk which attaches basally to the substratum. At the top of the calyx is an encircling tentacular crown of 8 to 30 solid tentacles, which are an extension of the body wall. The space enclosed by the tentacles contains the mouth at the anterior end and the anus at the posterior end. The fact that both the mouth and the anus are located within the central space is where the term Entoprocta is derived, which means “inside anus”. This feature distinguishes them from the Bryozoa which have the anus opening outside the feeding tentacles. The bryozoa are also known as Ectoprocta, meaning "outside anus". The stalk of the kamptozoa is equipped with longitudinal muscle fibers. When these muscle contract it produces the nodding motion of the calyx. Some solitary species are capable of locomotion. This is accomplished by using the sucker at the end of the stalk to glide along the surface, whereas others move by somersault.

Nutrition

Kamptozoa are filter feeders using their crown of tentacles to capture suspended organic particles and small phytoplankton. Cilia located laterally on the tentacles generate a feeding current that enters the central space. Suspended particles passing between the tentacles are trapped by the lateral cilia, where they are then transferred to the frontal cilia located on the inside of the tentacles. The frontal cilia transport the particles to the mouth, were they are ingested. The gut is U-shaped and contains a mouth, esophagus, stomach, intestine, rectum, and anus. The stomach is large, with enzymatic secretion and digestion taking place here. The stomach and intestine have numerous microvilli and are therefore thought to be the site of absorption.

Transport, Excretion, Nervous System

The nervous system in kamptozoa consists of a single large ganglion in between the mouth and the anus from which individual nerves reach out to the whole body. There are no special respiratory organs; instead gaseous exchange takes place over the surface of the body. The water current generated by the animal carries feces away from the mouth out through the central space in such a way that it does not contaminate the food bearing cilia.

Reproduction and Development

Kamptozoa reproduce either asexually by budding, or sexually with internal fertilization. Kamptozoa may have distinct sexes but more often they are hermaphroditic. Each zooid contains one or two pairs of saclike gonads located between the central space and the stomach. Many species have planktotrophic larvae which, after a short free swimming period of usually a couple of hours, the larvae settle on the bottom. Many larvae undergo metamorphosis, which in extreme cases involves the 180° rotation of the future calyx to attain the inverted condition of the adult. The larvae of the family Barentsiidae are shown in the picture to the left. In some species, the larva does not develop directly into an adult, but rather produces buds from which the adults are derived.

Phylogeny

Biologist first classified kamptozoa as bryozoans, however when it was discovered kamptozoa are acoelomate they were reclassified. At present they are thought to be trochozoans. Many biologists believe that the similarities between bryozoa and kamptozoa are convergent adaptations for sessile filter feeding by small animals. This conclusion is supported by the absence of a coelom, the location of the anus within the crown of tentacles and spiral cleavage, none of which are true for bryozoans. There are no obvious affinities between kamptozoa and other taxon except possibly the cycliophora which is thought to be its sister-taxon.

Fossil Record

It is known that the Kamptozoa are an ancient group of animals, however there has been only one fossil record, belonging to the extant genus Barentsia. This fossil was collected from the Upper Jurassic in England.

Four Families

Within the kamptozoan phylum there are four families. The Loxosomatidae are solitary with most living in association with other marine invertebrates. The distinguish feature of this family is the presents of a tall anal cone with elevates the anus. The Loxokalypodidae are solitary as well, with the stalk possessing muscle fibers throughout its length. The Pedicellinidae are colonial and have numerous unsegmented stalks arising horizontally from one stolon or form upright branching stems. This is shown in the above picture. The larvae of this family undergo complex metamorphosis. The Barentsiidae are colonial as well, and have a stalk which is divided into segments. The proximal and distal segments are muscular, but intervening segments lack muscles.

Annotated Bibliography

1. Wood, T.S. 2005. Loxosomatoides sirindhornae, new species, a freshwater kamptozoan from Thailand (Entoprocta). Hydrobiologia. 544: 27-31.

My first paper describes a new species of freshwater kamptozoa, Loxosomatoides sirindhornae, found in central Thailand. This makes the count of freshwater kamptozoan species two. Colonies of L. sirindhornae were collected on submerged substrata from November 2002 and March and August 2003. It was determined this species is from the Family Pedicellinidae. The calyx of L. sirindhornae possesses 12-16 colorless tentacles. The stalk is unsegmented and unbranched and does not exceed lengths of 0.45 mm. The species is found in water temperatures ranging from 29-32°C and have little tolerance for brackish water. Loxosomatoides sirindhornae is depicted in the above figure.



2. Iseto, T., Yokuta, Y., Hirose, E., 2007. Seasonal change of species composition, abundance and reproduction of solitary entoprocts in Okinawa Island, the Ryukyu Archipelago, Japan. Mar. Biol. 151: 2099-2107.

This paper examines seasonal change in composition, abundance and methods of reproduction in solitary kamptozoa. Kamptozoa were collected monthly from December 2000 to November 2001 using 12 glass slides. The slides were held vertically in a plastic slide box. Large windows were opened at the top and bottom of the slide box to allow for the passage of water and organisms. Once collected, the species were identified and the occurrence of sexual and asexual reproduction was examined. It was determined there is a seasonal pattern of abundance, with abundance being high in the summer and low in the winter. Of the 18 322 individuals examined only 0.37% possessed embryos and all of them were found in July and August in contrast to budding being observed each month in all species. It was concluded high water temperatures induced sexual reproduction.



3. Yakovis, E.L. 2002. Substrate preference of a non-colonial kamptozoan, and its interactions with bryozoan hosts. Mar. Biol. 141: 1109-1115.

This paper describes specific substrate preferences of Loxosomella nordgaardi and its interactions with bryozoan hosts. Yakovis wanted to determine whether there was preference to occupying living bryozoan colonies rather then other available substrate. Sampling of the White Sea was carried out from June to September 1994 – 1997. Of the 1145 L. nordgaardi specimens found on substrates, 93.5% of were collected from the surface of bryozoan colonies, whereas only 6.5% was located on algal substrate. The abundance was found to be 60 times greater on bryozoan colonies than on algal blades. It was discovered L. nordgaardi aggregate on large colonies formed by host species with relatively large tentacle crown diameters. This preference combined with the preference of living bryozoans probably indicates a dependence on the host produced flow shown in the figure below.