Rosalindidae is a family of

cnidarians Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...

belonging to the order

Anthoathecata Anthoathecata, or the athecate hydroids, are an order of hydrozoans belonging to the phylum Cnidaria. A profusion of alternate scientific names exists for this long-known and heavily discussed group. It has also been called Gymnoblastea and (with ...

Description

Rosalindidae are

hydrozoans Hydrozoa (hydrozoans; from Ancient Greek ('; "water") and ('; "animals")) is a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial spe ...

that are characterized by their ability to form colonies of

polyps A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase-shaped body. In solitary polyps, the aboral (opposite to oral) en ...

and attach to various surfaces, such as seaweed and shells, in the ocean. Rosalindidae are classified as

invertebrates Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum ...

. They are considered epibionts, which rely on other invertebrates to live and develop. Although

hydroids Hydroids are a life stage for most animals of the class Hydrozoa, small predators related to jellyfish. Some hydroids such as the freshwater '' Hydra'' are solitary, with the polyp attached directly to the substrate. When these produce buds, ...

like Rosalindidae typically live on hard substrates and among

coral Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...

rubble, as well as colonize

scleractinia Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a mo ...

, researchers have found Rosalindidae growing on larger animal hosts such as ''Cladocarpus paradiseus'' hydroids. Rosalindidae form monomorphic colonies (monomorphism) in contrast to the polymorphic colonies (polymorphism) that characterize other hydrozoan families. Rosalindidae make up the order Anthoathecata – a hydroid group generally known for its fragility due to the lack of a

perisarc Hydrozoa (hydrozoans; from Ancient Greek ('; "water") and ('; "animals")) is a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial spec ...

to protect its

gonophore A gonophore is a reproductive organ in members of the Hydrozoa which produces gametes. It is a sporosac, a Medusa (biology), medusa or any intermediate stage. The name is derived from the Greek words (, "that which produces seed") and (, "-bear ...

s and hydranths. However, colonies of polyps that fall under the genus ''Rosalinda'' possess a perisarcal skeleton composed of hydranths with several

tentacles In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

covering the body. ''Rosalinda'' was also reported having

cnidocyte A cnidocyte (also known as a cnidoblast) is a type of cell containing a large secretory organelle called a ''cnidocyst'', that can deliver a sting to other organisms as a way to capture prey and defend against predators. A cnidocyte explosively ...

s composed of stenoteles and mastigophores.

Distribution

Rosalindidae are globally distributed. They have been reported in the Northeast and Northwest

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

, the Central Eastern Atlantic off the African coast, the Northwestern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

, the

Bass Strait Bass Strait () is a strait separating the island state of Tasmania from the Mainland Australia, Australian mainland (more specifically the coast of Victoria (Australia), Victoria, with the exception of the land border across Boundary Islet). The ...

off

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

, the Western

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

, and the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

. Between 2001-2005, many species of the family Rosalindidae were discovered off the Southeastern U.S. coast, near the east coasts of

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

and

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

. Rosalindidae were spotted growing in deep-coral ecosystems in these oceanic areas, ranging from the deep-

neritic The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

to bathyal zones. One species, ''Rosalinda incrustans'', inhabited the northern Gulf of Mexico, but this same species was also found growing in the Northeastern Atlantic and Western Mediterranean Sea. Another ''Rosalinda'' colony was discovered attached to a different hydroid colony - ''Cladocarpus paradiseus'' - on the Jacksonville lithoherms at 595 m deep. This is the first time that researchers have observed this phenomenon. Other species of the Genus ''Rosalinda'' were discovered in the

Bay of Biscay The Bay of Biscay ( ) is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Point Penmarc'h to the Spanish border, and along the northern coast of Spain, extending westward ...

at approximately 440 m deep. ''Rosalinda williami'' was spotted in the Northeastern Atlantic. ''Rosalinda marlina'' was reported in shallow waters near Australia. Species of the Genus ''Rosalinda'' have also been found in the Northwestern Pacific Ocean. ''Rosalinda naumovi'' was identified in the shallower waters of the Northwestern Pacific while another unidentified species was discovered in

Sagami Bay lies south of Kanagawa Prefecture in Honshu, central Japan, contained within the scope of the Miura Peninsula, in Kanagawa, to the east, the Izu Peninsula, in Shizuoka Prefecture, to the west, and the Shōnan coastline to the north, while the i ...

, Japan. One research expedition discovered Rosalindidae species among coral mounds near the West African coast. These species were found growing on bivalves (

Bivalvia Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

). Near Northern Angola, ''Rosalinda'' ''nowaldi'' colonized the bivalve ''Acesta angolensis''. Off the coast of

Mauritania Mauritania, officially the Islamic Republic of Mauritania, is a sovereign country in Maghreb, Northwest Africa. It is bordered by the Atlantic Ocean to the west, Western Sahara to Mauritania–Western Sahara border, the north and northwest, ...

, ''Rosalinda lundalvi'' inhabited the bivalve ''Acesta excavata''.

Reproduction

Rosalindidae species that have been discovered thus far release

planula A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and also in some species of Ctenophores, which are not related to cnidarians at all. Some groups of Nemerteans also produce larva ...

larvae. However, further research needs to be conducted to determine whether Rosalindidae exhibit a medusa, or adult stage, of life. Rosalindidae are generally known to be sexually reproductive.

Diet

Rosalindidae are part of a larger group of hydrozoans, which consume

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater Aquatic ecosystem, ecosystems. The name comes from the Greek language, Greek words (), meaning 'plant', and (), mea ...

zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

, and tiny suspended particles using their tentacles. Little is known about the specific diet of Rosalindidae.

Movement

Much of the research on Rosalindidae focuses on their polyp form. In this stage, these hydrozoans are sedentary, relying on other hard substrates and hydrozoans to attach and assemble themselves. One Rosalindidae species, ''Rosalinda incrustans'', was found colonizing a spider crab (''Anamathia rissoana'').

References

Capitata Cnidarian families {{Anthoathecata-stub