Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks, annelid, and cnidarians.
The Placozoa are a basal form of marine free-living (non-parasitic) multicellular organism. They are the simplest in structure of all animals. Three genera have been found: the classical Trichoplax adhaerens, Hoilungia hongkongensis, and Polyplacotoma mediterranea, where the last appears most basal. The last two have been found only since 2017. Although the Placozoa were first discovered in 1883 by the German zoologist Franz Eilhard Schulze (1840–1921) and since the 1970s more systematically analyzed by the German protozoologist Karl Gottlieb Grell (1912–1994), a common name does not yet exist for the taxon; the scientific name means "flat animals".
Sponges, the members of the phylum Porifera, are a basal animal clade as a sister of the Diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like mesohyl sandwiched between two thin layers of cells. The branch of zoology that studies sponges is known as spongiology.
The California sea hare is a species of sea slug in the sea hare family, Aplysiidae. It is found in the Pacific Ocean, off the coast of California in the United States and northwestern Mexico.
Trichoplax adhaerens is one of the three named species in the phylum Placozoa. The others are Hoilungia hongkongensis and Polyplacotoma mediterranea. The Placozoa is a basal group of multicellular animals (metazoa). Trichoplax are very flat organisms around a millimetre in diameter, lacking any organs or internal structures. They have two cellular layers: the top epitheloid layer is made of ciliated "cover cells" flattened toward the outside of the organism, and the bottom layer is made up of cylinder cells that possess cilia used in locomotion, and gland cells that lack cilia. Between these layers is the fibre syncytium, a liquid-filled cavity strutted open by star-like fibres.
Demosponges are the most diverse class in the phylum Porifera. They include 76.2% of all species of sponges with nearly 8,800 species worldwide. They are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite. They are predominantly leuconoid in structure. Their "skeletons" are made of spicules consisting of fibers of the protein spongin, the mineral silica, or both. Where spicules of silica are present, they have a different shape from those in the otherwise similar glass sponges. Some species, in particular from the Antarctic, obtain the silica for spicule building from the ingestion of siliceous diatoms.
Sea apple is the common name for the colorful and somewhat round sea cucumbers of the genus Pseudocolochirus, found in Indo-Pacific waters. Sea apples are filter feeders with tentacles, ovate bodies, and tube-like feet. As with many other holothurians, they can release their internal organs or a toxin into the water when stressed.
Navanax inermis, common name the California aglaja, is a large species of predatory sea slug, a marine opisthobranch gastropod mollusk in the family Aglajidae. Navanax is not a nudibranch, even though it somewhat resembles one; it belongs to a more ancient lineage of opisthobranchs called the cephalaspideans or head shield slugs and snails.
The following outline is provided as an overview of and topical guide to zoology:
Marine invertebrates are the invertebrates that live in marine habitats. Invertebrate is a blanket term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a vertebral column, and some have evolved a shell or a hard exoskeleton. As on land and in the air, marine invertebrates have a large variety of body plans, and have been categorised into over 30 phyla. They make up most of the macroscopic life in the oceans.
Homosclerophorida is an order of marine sponges. It is the only order in the monotypic class Homoscleromorpha. The order is composed of two families: Plakinidae and Oscarellidae.
Amphimedon queenslandica is a sponge native to the Great Barrier Reef. Its genome has been sequenced. It has been the subject of various studies on the evolution of metazoan development.
Spongia officinalis, better known as a variety of bath sponge, is a commercially used sea sponge. Individuals grow in large lobes with small openings and are formed by a mesh of primary and secondary fibers. It is light grey to black in color. It is found throughout the Mediterranean Sea up to 100 meters deep on rocky or sandy surfaces.
Chondrocladia lyra, also known as the lyre sponge or harp sponge, is a species of carnivorous deep-sea sponge first discovered off the Californian coast living at depths of 10,800–11,500 feet (3,300–3,500 m) by Welton L. Lee, Henry M Reiswig, William C. Austin, and Lonny Lundsten from the Monterey Bay Aquarium Research Institute (MBARI).
Aquarium de La Rochelle is a family-owned public aquarium in La Rochelle, France. It has a surface area of over 8,445 m2 (90,901 sq ft) with 3 million litres of seawater. It has 73 display aquaria and 150 quarantine aquaria exhibiting more than 12,000 animals of 600 different species. It has an average of 800,000 visitors per year.
Oscarellidae is a family of marine sponges.
Geodia barretti is a massive deep-sea sponge species found in the boreal waters of the North Atlantic Ocean, and is fairly common on the coasts of Norway and Sweden. It is a dominant species in boreal sponge grounds. Supported by morphology and molecular data, this species is classified in the family Geodiidae.
Jean Vacelet is a French marine biologist who specialises in the underwater fauna of the Mediterranean. After earning his licence at the Faculté des Sciences de Marseille and learning to dive in 1954, he specialised in the study of sponges at the Marine station of Endoume, and there he has stayed faithful to both sponges and place for more than half a century. His research has included all aspects of sponges: taxonomy, habitat, biology, anatomy, their bacterial associations, and their place in the evolution of multi-celled animals. He has studied them not only in the Mediterranean but in the Indian Ocean and the Pacific. Exploration of underwater grottoes, together with Jacques Laborel and Jo Hamelin, revealed the existence of sponges dating from very ancient geological periods and the unexpected existence of carnivorous sponges, and surprisingly, the grottoes in some ways mimicked life at much greater depths.
Gert Wörheide is a German marine biologist who works mainly on marine invertebrates. He earned his doctorate in geobiology from Georg-August-Universität, following this with a post-doctorate at Queensland Museum (1998-2002), where he worked with John Hooper on sponges,a collaboration which continues.
