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|Coral lovers! - vi som älskar korallrev!||Introduction to the Illustrated species list - introduktion till den illustrerade artlistan||Guide to all phyla with an illustrated species list||Guide till alla fyla med illustrerad artlista||Species list- artlista|
Guide to all phyla found on the settling panels
Here follows brief introductions to all the phyla (groups of higher taxonomic ranking) in the material from the Saekken reef, and if you click on the images you will be directed into a photo gallery of the different species within this particular phylum.
This is the Illustrated species list.
(If you find erraneous identifications or want to give feedback of some other kind, please contact me at the e-mail address at the bottom of this page)
[40,000 described species] Foraminiferans are one-celled (with a few multicellular exceptions) eukaryotic organisms producing more or less intricate tests (outer skeletons) of calcium carbonate or particles. Forams are heterotrophic and include herbivores, carnivores, and omnivores. Feeding is by phagocytosis and 'reticulopodia' (long cell protrusions) is used for pray capture, i.e. vesicles at the tip of the reticulopodia secrete a sticky substance that adheres the pray. Most species present on the panels were very small, measured in mm, while some of the arborescent were several cm. There are deep-sea species of foraminiferans that can reach up to one meter, still only consisting of one single cell. The diversity in this group is astonishing. Being a difficult group, the names is often followed by a question mark.
[12,000 species described] The ciliates is a diverse group with both planktonic and benthic mobile or sessile species. They are singled-celled like forams, but can develop branching or linear colonies. They can live as ecto- or endosymbionts and some ciliates are important mutualistic symbionts inside the digestive tracts of herbivores, converting plant material into more easily metabolized forms. The specimens found in this material were from the families; Zoothamniidae, Folliculinidae, Stentoridae. There were both mobile and sessile specimens, solitary and colonial. Many was found living in small crevices or in old bryozoans. One was found living on the operculum (tube blocking part of tentacles) of a bristleworm (Hydroides norvegica). The marine zoothamnids and folliculinids are well known, but only two marine species of Stentoridae are described, and none of the found belonged to those.
[5,500 species described] The sponges are sessile, suspension-feeding, multicellular organisms, but without true tissues. They function very much like protists (Protoctista, e.g. forams, ciliates, amoebas) at the level of nutrition uptake, cellular organisation, gas exchange, and response to stimuli. This makes them more like colonies of single-celled organisms. Most of the cells are 'totipotent', capable of changing form and function to adjust for the needs of the colony. The water circulation is driven by ciliated cells ('choanocytes'), i.e. the water is drawn in through many smaller openings and is let out of one or few larger openings. There are three classes of sponges; Calcarea (with inner skeletal parts, 'spicules', of calcium carbonate), Hexactinellida ('glass sponges', with siliceous hexactinal spicules), and Demospongiae (with siliceous simple spicules supported by collagen, 'spongin').
[11,000 species described] The cnidarians is a highly diverse group that includes jellyfish, sea anemones, corals, hydroids, sea fans, and siphonophores. The body plan is simple, with single-cell layers of ecto- (epidermis) and endoderm (gastrodermis), and a non-cellular mesoglea in between. They have an oral-aboral body axis, and with a primarily radial symmetry that can be further modified to biradial, quadriradial or some other form. Reproduction is both sexual and asexual (e.g. by budding, fragmentation) and they exhibit alternation of asexual polypoid and sexual medusoid generations with a high degree of variation of how this is expressed. The main charachteristic of cnidarians is the 'cnidae', stinging or adhesive structures used for protection or feeding and anchoring - e.g. in the planula larvae of corals they might function as anchoring devices when the larva is ready to settle and metamorphose. The cnidae is produced by a specialized cell called cnidocyte, and there are several types of cnidocytes, e.g. nematocysts (true toxic stinging-cells charged with phenols and proteins), spirocysts (with adhesive mucoprotein or glucoprotein), ptychocysts (mechanically adhesive, only in ceriantharians to produce the tube).
[1,300 species described] Nemerteans (nemertea = Greek for 'sea nymph', someone found them beautiful...), or 'ribbon worms', range from less than 1 cm to several meters in length. Their bodies are very flexible and can stretch out several times their contracted length. There are some planktonic or symbiontic (in molluscs or other invertebrates) species, but in general they are living on the seafloor (benthic). A few freshwater, and terrestrial specis are also known. They have an eversible proboscis that is unique to this phylum and most of them are active predators, although some scavengers are known. The proboscis apparatus can extend as far as half the body length and when eversed it coils around the pray which is then drawn into the mouth. Some species are very colorful and with different patterns, e.g. Tubulanus annulatus, in Sweden known as the 'christmas present worm' due to its crossing stripes.
PHYLUM: ANNELIDA Class: Polychaeta
[16,500 species described] The bristleworms (Polychaeta = many chaeta) is a group within Annelida (which includes earthworms and leeches) with parapodia equipped with bristles on most body segments as a characteristic. The bristleworms are mainly marine but there are freshwater species, and even terrestrial ones. They are often grouped into two basic groups; the active predators (errantia) and the sessile suspension-feeders or deposit feeders (sedentaria), although this is not a taxonomically valid grouping. Practically all are benthic, there is only one monogeneric family with pelagic life style (Tompteridae). The size range is impressing; from less than 1 mm to over 3 m in length. The largest species found in the present material is Eunice norvegica, this species can become 30 cm and is gigantic in comparison with all others found.
[93,000 species described] The molluscs include the best known invertebrates; the snails and slugs (Gastropoda, 70,000 species), clams (Bivalvia, 20,000 species), squids, and octopuses (Cephalopoda, 900 species). But there are small molluscs that are less known, i.e. chitons (Polyplacophora), Monoplacophora, tusk shells (Scaphopoda), and the vermiform shell-less Aplacophora. The gastropods is charecterized by having one shell but includes the subclass Opisthobranchia (slugs, nudibranchs, pteropods) with no, or reduced, shells. Bivalves is characterized by having two valves as the name implies. The chitons and monoplacophorans are evolutionary relics with a long history on the planet and early fossil records. The Monoplacophorans were only known from lower Paleozoic fossils before living specimens were discovered as late as 1953. Chitons has 8 shell plates while monoplacophorans looks like limpets, with one shell. Tusk shells has an elongate tubular shell with openings at both ends. The cephalopods include Nautilus with the characteristic external shell, and cuttlefish with internal or absent shell, just like squids and octopuses.
[over one million species described; of which 67,000 belong to Crustacea] The arthropods is characterized by jointed outer skeletons and although several groups of arthropods are present in the marine environment (e.g. mites and sea spiders) I will concentrate on crustaceans. The diversity is astonishing, ranging from the tiny ostracods, copepods etc, to the Japanese spider crab with a leg span of 4 m. Also the barnacles belong to the crustaceans. They outcompete insects by far in both taxonomic diversity and number. Giving a fair resumé of crustaceans would demand far much more space than available here, so I will let the images speak for themselves. Look into the gallery!
[4,500 species described] The bryozoans (or 'moss animals') are colonial organisms emanating from a sexually produced individual called the 'ancestrula'. The ancestrula then reproduces asexually to produce a colony of clones. The colony consists of specialized individuals; i.e. autozooids with lophophores (tentacle crowns) for feeding, and heterozooids, non-feeding individuals responsible for other functions of the colony (e.g. attachment. The individual zooids reside in zoecia, small calcareous or gelatineous cascets. Most bryozoans are hermaphrodites with each zooid capable of producing both eggs and sperm, but often one colony consist of both female and male individuals. They brood their embryos in gonozooids (modified zoecia) or embryo sacs (invaginations of the body wall).
[335 now living species of more than 12,000 described from fossil records] Brachiopods (Greek 'brachium', arm; 'poda', feet) superficially resemble bivalves with their two shells, however, beneath the shell is not the fleshy foot of a mollusc. The internal morphology reveals a relationship to bryozoans, or the lophophores; a horse shoe shaped crown of tentacles ('lophophore'). Three different species were present in this material, two from the class Articulata, with two shells, and one from the class Inarticulata, with one shell. While the Articulata use a pedicle for attachment, the Inarticulata is firmly attached with groups of muscles that leaves a skull like shape on the substrate if removed.
[7,000 species described] Sea stars and sea urchins is probably familiar to everyone, but this group also contain less familiar groups like the brittle stars (image), sea lilies, feather stars, and sea cucumbers. There is a great size span in this group, with brittle stars and sand dollars of less than 1 cm, to sea cucumbers up to 2 m in length. This is a marine group, although some species are adapted to brackish water, and they are present from sea shore down to thousands of meters in the abyssal zone. The present material contained several species of brittle stars (Ophiuroidea) and one species belonging to the class Crinoidea (feather stars). These two groups are found mainly in deep-sea habitats. The brittle stars resemble sea stars in that they have a central disk with five arms (a few species have six arms), sometimes branching (e.g. in Gorgonocephalus, 'basket stars'). The arms are set off from the central disc more distinct than in sea stars and are long and slender, tapering only slightly towards the tips. Brittle stars display numerous feeding strategies including predation, deposit feeding, scavenging, and suspension feeding (some by mucus traps). The feather stars (Crinoidea, also including sea lilies) look quite different, with a body shape more cup-like ('calyx'-shaped) and the oral surface facing upwards instead of down, as in sea stars and brittle stars. They also have five arms, although branching to the double. Instead of lying 'face down' on the seafloor, they are attached by a cluster of jointed feet ('cirri') to a hard substrate, elevated from the bottom, adapted for suspension feeding. The cirri are not permanently attached to the substrate, if disturbed they can easily let go and swim away. The juvenile feather stars ('pentacrinoid'), however, are attached to the substrate by a stalk, just like the adult sea lilies. When mature, they loosen themselves from the stalk and swims off to search for a more current exposed spot with better feeding. Another characteristic of the echinoderms is, of course, the ability of regeneration of lost limbs.
[85 species described] This is a very obscure and poorly known group of organisms including three classes; acorn worms (Enteropneusta), pterobranchs (Pterobranchia), and Planctosphaeroidea (consisting of only one 'species' which probably is a larval stage, although nobody knows what it will be when it grows up). The two latter is so obscure that they haven't even got common names. The only species found in this material (Rhabdopleura normani) belong to the Pterobranchia, and I'll concentrate on this species alone. Rhabdopleura is a colonial species, with the individuals (zooids) connected by a mutual stolon, and as in Bryozoa the colony starts with one sexually produced individual that produce a colony of clones by budding. The connective tissues in the stolon are blood red, giving a characteristic look to the colony. The individual tubes are transparent and annulated, perpendiculary directed from the substrate. The animal itself is sac-like, with two tentacle bearing arms that they use for prey capture by secreting a mucus net held up between the arms. The individuals are connected to the rest of the colony by a muscular stalk, leding down to the stolon, that is used when they retreat into the tube. When I first saw this creature I was pretty sure to have found something completely new, but when consulting our 'all-knowing' Oracle of South Scandinavian invertebrates, Hans G. Hansson, he knew directly what this was and added; 'we haven't seen this for 20 years!'. This is exclusive images!
[almost 50,000 species described] Chordates are the phylogenetic root to all vertebrates, and characterized by having a notochord, a dorsal, hollow nerve cord - the beginning of a backbone. Us vertebrates are a subphylum to Chordata, together with Urochordata (tunicates), and Cephalochordata (lancelets). Here, I concentrate on the sea squirts (class Ascidiacea), a group within the tunicates. This is a group of marine suspension feeders (except for some deep-sea predatory species), with a solitary or colonial life style. The notochord is present only in the larva, while lost in the adult sea squirt, i.e. they are so highly modified to their way of life that they reduced the notochord in favour to a more 'slimmed' design. The body of a sea squirt is a hollow 'tunic', with an incurrent (oral) and excurrent (atrial) siphon for water exchange and feeding. The identification of sea squirts involves dissecting the animal to have a look at the curving of the intestines, stomach and gonad placement etc. A time consuming job that was not feasible with this extensive material. There are some guiding external features that gives a hint on what family to start with, e.g. the Styelidae is characterized by having 4 lobes on the siphons. Two species of Pyuridae (i.e. Pyura tesselata and Boltenia echinata) are so distinct and can't be mistaken, as you will see. Being colonial narrows it down as well.
PHYLUM: NEMATA (NEMATODA)
[25,000 species described] The roundworms and threadworms (Greek 'nema', thread) are well known since they include many parasitic species that has been of great concern in human and veterinary medicine. There are, however, many free-living marine species that are self-supporting. In this material they were found in agglutinated sediments, very difficult to detect, and there were probably many times more of them than the few I saw. As an example there can be as many as 90,000 nematodes in a single rotting apple, or up to 9 billion per acre in farmland soil.
[20,000 species described] The flatworms (Greek 'platy', flat; 'helminth', worm) are unsegmented worms that are free-living or parasitic. Free-living marine species can be very colorful and they use cilia and mucus for gliding across the substrate, predating or scavenging on any animal matter. A few are herbivores, gracing on microalgae, and some species switch from grazing to scavenging as they mature. Some species lives as commensal (lat. 'con', same; 'mensa', table) symbionts in or on a host animal, doing no damage, while others abuse the hospitality and nibble on the host, causing various degrees of damage
[150 species described] The entoprocts are small, sessile, solitary or colonial organisms with a simple body plan; an attachment disc, stalk, and a cup like body with a circle of tentacles. Colonial forms are growing from a mutual stolon. The 'body' has a separated mouth and anus at each end of a simple stomach and intestine only distinguished by the cell lining. They were at first thought to belong to the bryozoans, or represent a primitive ancestral condition to the latter. The final resolution of their taxonomic belonging is yet to be discovered.
PHYLUM: CHAETOGNATHA (no image)
[100 species described] Arrow worms are small marine planktonic or benthic predators (0.5 to 12 cm in length) with an elongate body lined with lateral fins, as well as a tail fin. They feed upon planktonic crustaceans like copepods, and even small fish. The benthic genus (Spadella), like the one found in this material, are ambush predators, attached to a substrate they await for someone to pass by...
Source: Brusca & Brusca: Invertebrates (2nd ed)