The Doubtful Facelina – Facelina dubia is a species of sea slug belonging to the family Facelinidae. It is a colorful and relatively common nudibranch found in various coastal regions. The species’ name “dubia” reflects a degree of uncertainty among marine biologists regarding its taxonomic classification.
Description & Characteristics
Facelina dubia is a relatively small nudibranch, reaching a maximum size of approximately 25 mm in length. It exhibits a distinctive, elongated body with a slender, pointed head. The body’s coloration is highly variable, ranging from white to yellow, orange, and even red. This variability is often influenced by the diet of the individual, which can also impact the presence and intensity of pigmented spots and markings on the body.
The species’ most prominent characteristic is a series of cerata – finger-like projections along its dorsal surface. These cerata are covered with stinging cells called nematocysts, which are obtained from the nudibranch’s prey and serve as a defense mechanism against predators. In Facelina dubia, these cerata are usually tipped with bright orange or yellow, providing a striking contrast against the base color of the body.
Habitat and Occurrence
The Doubtful Facelina – Facelina dubia primarily inhabits the intertidal zone, a region of the coastline that lies between the high and low tide marks. This zone is characterized by fluctuating water levels and exposure to air, making it a challenging environment for marine organisms. Facelina dubia thrives in these dynamic conditions, utilizing the intertidal zone as a vital habitat for foraging and reproduction. The species can also be found in the shallow subtidal, a zone extending below the intertidal, where it often resides amongst rocky crevices and seaweed beds.
Facelina dubia exhibits a wide distribution across temperate and subtropical regions of the world. This sea slug is particularly common in the North Atlantic, where it occurs along the coasts of Europe and North America. It is often observed in marine ecosystems along the coast of the United Kingdom, Ireland, France, Spain, Portugal, and parts of the United States. Facelina dubia is also known to occur in the Mediterranean Sea, extending its presence across various regions of the world.
Taxonomy
The species Facelina dubia belongs to the Class: Gastropoda, Order: Nudibranchia, and Family: Facelinidae. Gastropods are a vast and diverse class of mollusks, encompassing snails, slugs, and limpets. Nudibranchia, also known as sea slugs, are a highly specialized group within the gastropods, characterized by their lack of shells and vibrant coloration. The family Facelinidae, to which Facelina dubia belongs, is a diverse group of sea slugs known for their elongate bodies and distinctive cerata.
Feeding
Facelina dubia is a food specialist, meaning it has a highly specific dietary preference. This nudibranch primarily feeds on hydrozoa polyps, a type of colonial animal belonging to the phylum Cnidaria. Hydrozoans are commonly found in intertidal and subtidal zones, and they play a crucial role in marine ecosystems. Facelina dubia effectively exploits these resources, utilizing its specialized feeding apparatus to extract nutrients from its preferred prey.
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