''Lepas testudinata'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

goose barnacle Goose barnacles, also called percebes, turtle-claw barnacles, stalked barnacles, gooseneck barnacles, are filter-feeding crustaceans that live attached to hard surfaces of rocks and flotsam in the ocean intertidal zone. Goose barnacles form ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Lepadidae Lepadidae is a family of goose barnacles, erected by Charles Darwin in 1852. There are about five genera and more than 20 described species in Lepadidae. Genera These genera belong to the family Lepadidae: * '' Conchoderma'' von Olfers, 1814 (wh ...

. First observed in 1834, ''Lepas testudinata'' has undergone several reclassifications, and its relationship to other ''

Lepas ''Lepas'' is a genus of goose barnacles in the family Lepadidae. Species Species in the genus include: * '' Lepas anatifera'' Linnaeus, 1758 * '' Lepas anserifera'' Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known a ...

'' species is still the subject of ongoing research. ''L. testudinata'' is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to temperate waters in the

China Seas The China Seas consist of a series of marginal seas in the Western Pacific Ocean, around China. They are the major components signifying the transition from the continent of Asia to the Pacific Ocean.Pinxian Wang, Qianyu Li, Chun-Feng Li, ''Geol ...

, Australian Sea, and the Indo-West Pacific, and there are two distinct subgroups within the species. This barnacle species exclusively colonizes free-floating debris and tidewrack, and can form colonies of over 1000 members at a time. Due to this colonization habit, ''L. testudinata'' plays a role in

biofouling Biofouling or biological fouling is the accumulation of microorganisms, plants, algae, or small animals where it is not wanted on surfaces such as ship and submarine hulls, devices such as water inlets, pipework, grates, ponds, and rivers that ...

and often serves as a

foundation species In ecology, the foundation species are species that have a strong role in structuring a community. A foundation species can occupy any trophic level in a food web (i.e., they can be primary producers, herbivores or predators). The term was coine ...

when preyed upon.

Taxonomy

''Lepas testudinata'' is a

in the

. The species was likely first observed in 1834 by

Jean René Constant Quoy Jean René Constant Quoy (10 November 1790 in Maillé, Vendée, Maillé – 4 July 1869 in Rochefort, Charente-Maritime, Rochefort) was a French naval surgeon, zoologist and anatomist. In 1806, he began his medical studies at the school of naval ...

and

Joseph Paul Gaimard Joseph Paul Gaimard (31 January 1793 – 10 December 1858) was a French naval surgeon and naturalist. Biography Gaimard was born at Saint-Zacharie on January 31, 1793. He studied medicine at the naval medical school in Toulon, subsequen ...

, and was initially named ''Lepas elongata''. In 1892, Carl Wilhelm Samuel Aurivillius described what he believed to be a separate species as ''Lepas testudinata,'' with its official classification as ''Lepas (Lepas) testudinata''. In 1978, Brian Arthur Foster declared ''Lepas elongata'' a

nomen oblitum In zoological nomenclature, a ''nomen oblitum'' (plural: ''nomina oblita''; Latin for "forgotten name") is a disused scientific name which has been declared to be obsolete (figuratively "forgotten") in favor of another "protected" name. In its pr ...

since it had not been used since the 1920s. Foster concluded that ''Lepas elongata'' is

synonymous A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

with ''Lepas testudinata'' due to their similar geographical distribution and peduncle structure. In this same paper, Foster also declared ''Lepas affinis'' (named by

Lancelot Alexander Borradaile Lancelot Alexander Borradaile (26 September 1872 – 20 October 1945) was an English zoologist, noted for his work on crustaceans and his books ''The Invertebrata'' and ''Manual of Elementary Zoology''. Legacy Borradaile may be best known for hi ...

, 1916) a synonym.

Description

''Lepas testudinata'' is a

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

filter feeding Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a spe ...

barnacle Barnacles are arthropods of the subclass (taxonomy), subclass Cirripedia in the subphylum Crustacean, Crustacea. They are related to crabs and lobsters, with similar Nauplius (larva), nauplius larvae. Barnacles are exclusively marine invertebra ...

. Their

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses Science Biology * Seashell, a hard outer layer of a marine ani ...

is made of two bivalved pieces that are both made up of five symmetrical

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

plates laid on top of one another; this five-plate structure is found in all ''Lepas'' species. ''L. testudinata'' has a defined

abdominal The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

segment and its adductor muscles are situated in front of the head shield. Adults can grow up to . In 2015, Philipp H. Schiffer and Hans-Georg Herbig hypothesized that the number of plates increased as the species

evolved Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...

, but a 2012 study by Marcos Pérez-Losada and colleagues argued that the modern day 5-plate structure is a result of

secondary loss In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

, or the evolutionary reversion to an ancestral physiology. They concluded that

evolutionary pressure Evolutionary pressure, selective pressure or selection pressure is exerted by factors that reduce or increase reproductive success in a portion of a population, driving natural selection. It is a quantitative description of the amount of change o ...

s are not driving the species to have thicker shells. Located antero-laterally from the head shield, ''L. testudinata'' employs a frontal horn, a

sensory organ A sense is a biological system used by an organism for sensation, the process of gathering information about the surroundings through the detection of stimuli. Although, in some cultures, five human senses were traditionally identified as su ...

made up of

glandular tissue A gland is a cell or an organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also function to remove unwanted substances ...

. Additionally, the species employs a photoreceptive naupliar eye within the

mantle cavity The mantle (also known by the Latin word pallium meaning mantle, robe or cloak, adjective pallial) is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of ...

. ''Lepas testudinata'' has a single, muscular peduncle (also referred to as a stem or a stalk) that can extend from the shell and affix it to an object; the

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

of this stalk is largely dependent on the object ''L. testudinata'' has affixed itself to. When affixed to

kelp Kelps are large brown algae or seaweeds that make up the order (biology), order Laminariales. There are about 30 different genus, genera. Despite its appearance and use of photosynthesis in chloroplasts, kelp is technically not a plant but a str ...

, the peduncle is smooth and can be up to in length. This compares to non-kelp forms that have a short and spiny peduncle. It is still unclear if these two phenotypes represent two distinct lineages within the species or indicate a yet to be understood morphological adaptation.

Life cycle

''Lepas testudinata'' is

hermaphroditic A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

, and the species does not demonstrate

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

. ''L. testudinata'' reproduces via broadcast spawning, meaning that the

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

s are

fertilized Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or off ...

in the barnacle's mantle cavity. The eggs hatch into nauplii larvae and then pass through six naupliar stages. Following this, they enter a non-feeding cyprid larval stage, known as the settling stage. From there, they

metamorphose Metamorphosis is a biological process by which an animal physically developmental biology, develops including birth, birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through ...

into their final,

adult An adult is an animal that has reached full growth. The biological definition of the word means an animal reaching sexual maturity and thus capable of reproduction. In the human context, the term ''adult'' has meanings associated with social an ...

stage. Similar to other '' Cirripedia'' species, ''L. testudinata'' employs a set of

compound eye A compound eye is a Eye, visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidium, ommatidia, which are tiny independent photoreception units that consist of a cornea, lens (anatomy), lens, and p ...

s prior to metamorphosis, where they are partially lost and continue to function in a reduced state throughout maturation.

Ecology and colonization

Similar to other species of barnacles, ''Lepas testudinata'' forms

colonies A colony is a territory subject to a form of foreign rule, which rules the territory and its indigenous peoples separated from the foreign rulers, the colonizer, and their '' metropole'' (or "mother country"). This separated rule was often or ...

along tidewrack,

driftwood Driftwood is a wood that has been washed onto a shore or beach of a sea, lake, or river by the action of winds, tides or waves. It is part of beach wrack. In some waterfront areas, driftwood is a major nuisance. However, the driftwood provides ...

, and man-made items. They do not affix themselves to stationary objects, instead they exclusively prefer mobile, floating objects. This preference has allowed the species to become widespread across temperate oceans in the Southern Hemisphere. ''L. testudinata'', in particular, shows a preference to colonize on the

species ''

Ecklonia maxima ''Ecklonia maxima'', or sea bamboo, is a species of kelp native to the southern oceans. It is typically found along the southern Atlantic coast of Africa, from the very south of South Africa to northern Namibia. In these areas the species dominat ...

.'' The species can regularly form colonies greater than 1000 members and has a tendency to colonize

plastic pollution Plastic pollution is the accumulation of plastic objects and particles (e.g. plastic bottles, bags and microbeads) in the Earth's environment that adversely affects humans, wildlife and their habitat. Plastics that act as pollutants are catego ...

when available. Their colonization of man-made objects is the main factor in the species' dispersal throughout the South African region. Off the coast of

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

, the

sea slug Sea slug is a common name for some Marine biology, marine invertebrates with varying levels of resemblance to terrestrial Slug, slugs. Most creatures known as sea slugs are gastropods, i.e. they are Sea snail, sea snails (marine gastropod moll ...

Fiona pinnata ''Fiona pinnata'', common name Fiona, is a species of small pelagic nudibranch (sea slug), a marine (ocean), marine gastropod mollusk in the superfamily Fionoidea. This nudibranch species lives worldwide on floating objects on seas, and feeds mai ...

'' predates ''Lepas'' species barnacles, and ''L. testudinata'' is often found colonizing the kelp species ''

Durvillaea antarctica ''Durvillaea antarctica'', also known as ' and ', is a large, robust species of southern bull kelp found on the coasts of Chile, southern New Zealand, and Macquarie Island.Smith, J.M.B. and Bayliss-Smith, T.P. (1998). Kelp-plucking: coastal eros ...

''.Willan R. C. (1979) "New Zealand locality records for the aeolid nudibranch ''Fiona pinnata'' (Eschscholtz)". ''Tane'' 25: 125
PDF
/ref> Along with other species of ''Lepas'' barnacles, ''Lepas testudinata'' poses a major risk to

damage, as colonies can form on man-made structures and damage them. ''L. testudinata'' also functions as a

when their colonies wash ashore, where they are then consumed by

scavenger Scavengers are animals that consume Corpse decomposition, dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a he ...

s. A 2021 study by Thomas Mesaglio and colleagues found that the presence of washed-up ''L. testudinata'' colonies on beaches result in

ecological succession Ecological succession is the process of how species compositions change in an Community (ecology), ecological community over time. The two main categories of ecological succession are primary succession and secondary succession. Primary successi ...

that significantly increases the

species diversity Species diversity is the number of different species that are represented in a given community (a dataset). The effective number of species refers to the number of equally abundant species needed to obtain the same mean proportional species abundan ...

of the local environment.

Distribution and evolution

''L. testudinata'' is broadly

distributed Distribution may refer to: Mathematics *Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations *Probability distribution, the probability of a particular value or value range of a varia ...

throughout the Southern hemisphere and its range extends into parts of the

Northern hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

, though it is strictly limited to

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

waters. More specifically, it is distributed throughout the

, Australian Sea, and the

Indo-West Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the s ...

. The species was not observed in

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

's seas until the 1990s, and ongoing research seeks to determine if it was accidentally introduced to this region or not. Despite this wide range, ''L. testudinata'' is generally considered a rarely observed species. The species has not been evaluated by the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

Mitochondrial A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...

data of ''L. testudinata'' shows that there are two subgroups within the species, one in

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

n waters, and one in

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 ...

n waters. While the exact relationship between these subgroups is unknown, Schiffer and Herbig proposed that the genetic deviation of these two groups is caused by ''L. testudinata's''

native range Species distribution, or species dispersion, is the manner in which a biological taxon is spatially arranged. The geographic limits of a particular taxon's distribution is its range, often represented as shaded areas on a map. Patterns of distr ...

being noncontinuous. The species cannot survive in Antarctic waters and the Antarctic current system thus forms a barrier between the South African and Australian subgroups. Analyses of the 18S gene places ''L. testudinata'' within an

ingroup In social psychology and sociology, an in-group is a social group to which a person psychologically identifies as being a member. By contrast, an out-group is a social group with which an individual does not identify. People may for example ...

to '' L. anatifera'' but analysis of the 28S sequence places it within an ingroup to ''L. australis''. Due to the broad similarities in morphology between these three species, their overall phylogeny is considered to be very closely related and is the subject of continued research. The following

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

shows the phylogenetic position of ''L. testudinata'' among select members of the genus ''Lepas'', based upon comparison of the 18S gene:

References

External links

* {{Portal bar, Crustaceans, Marine life Barnacles of the Indian Ocean Barnacles of the Pacific Ocean Crustaceans described in 1892 Taxa named by Carl Wilhelm Samuel Aurivillius