Mucus, from the epidermis of the sole, and urea, from the urine of a nearby host, can stimulate eggs to hatch, possibly increasing the chances of larvae to make contact with a host. During the oncomiracidium stage, individuals of Entobdella soleae find their hosts by chemoreception to a substance secreted by the host's mucus cells in its epidermis. A theorized search pattern for hosts is accomplished with the coupling of horizontal transport of larvae by water currents and photopositive and photonegative vertical movements. Photopositive vertical movements become less frequent as the larvae grow older. Larvae have also been shown to find prey in the presence of only infra-red light. It is hypothesized that pheromone attractions allow for early mating among the individuals.
Other Communication Modes: pheromones
Perception Channels: infrared/heat ; chemical
Entobdella soleae has no special conservation status.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
The life cycle of Entobdella soleae is largely dependent on the presence and hypoactivity of a host sole. Individuals secured to the lower surface of the host lay eggs that become secured to the substrate via a sticky coating. This prevents the eggs from being taken away from a population of hosts by currents should the parental host change location. After approximately a month of development, larvae emerge from the egg within 5 minutes of being activated by an environmental stimulus. Studies suggest that the hatching of the eggs is rhythmic with respect to light and that sole mucous or urea activate the embryos. The larval form that hatches from the egg is referred to as an oncomiracidium. This free swimming larvae locates a host; attachment may occur as quickly as 2 minutes after hatching and must be completed within 24 hours, before the oncomiracidium depletes its energy and dies. The oncomiracidium attaches to the host’s upper anterior surface before migrating to the lower surface. Upon attachment, the parasite sheds its ciliated epidermal cells. The exact duration of the larval stage is not reported in literature. However, it is suggested to last approximately 40 days, the length of time required to complete the migration process to the lower surface of the host where it subsequently reaches sexual maturity. Thus, with the exception of the egg, there is little to no uninfective period throughout the life cycle of E. soleae.
Development - Life Cycle: metamorphosis
Because Entobdella soleae is a skin parasite capable of causing death of its host, Solea solea, this monogenean parasite is an economic hindrance for humans. Solea solea is a versatile fish used in cooking and highly valued for its taste in Europe.
There are no known positive effects of Entobdella soleae on humans.
Entobdella soleae is a skin parasite. The host is specific for this monogenean parasite and is Solea solea, a flatfish. In the wild, only a few parasites are found on a given host. In fish farms, a few hundred parasites can be found per fish, causing mass skin inflammation and death.
Ecosystem Impact: parasite
Species Used as Host:
Entobdella soleae is a skin parasite of Solea solea and uses its pharynx as its feeding organ. There are glands in the pharynx that secrete proteolytic enzymes to digest the epidermis of the flatfish. The pharynx sucks in the digested food in liquid form for absorption in the intestinal diverticula.
Animal Foods: fish
Primary Diet: carnivore (Piscivore )
Entobdella soleae is a monogenean flatworm and an ectoparasite of the common sole (Solae solae). As such, its range is limited to geographic areas inhabited by the common sole, mostly in the eastern Atlantic Ocean from Norway to Senegal and in the Mediterranean Sea. The common sole is frequently harvested for food in Europe, and a large number of parasitic infections by E. soleae have been reported in captivity.
Biogeographic Regions: atlantic ocean (Native ); mediterranean sea (Native )
Entobdella soleae is generally found in temperate, marine environments high in host availability. Entobdella soleae has extremely high host exclusivity, with literature citing only three possible host species, all within genus Solae, with a strong preference for Solae solae over other soleid fish. Solae solae is most commonly found hidden within the sand or mud in shallow waters. While larvae may initially be free-swimming, adults live exclusively on the skin of the host. A free-swimming larva will attach to the dorsum of the host and migrate toward the host's ventral surface, which is in contact with the sea floor, where it completes development and reproduces.
Range depth: 0 to 152 m.
Habitat Regions: temperate ; saltwater or marine
Aquatic Biomes: benthic
Individuals of Entobdella soleae have a lifespan of up to 6.5 months. There is no observed difference between those individuals obtained from the wild and those grown in a laboratory setting.
Range lifespan
Status: wild: 6.5 (high) months.
Range lifespan
Status: captivity: 6.5 (high) months.
The average size of Entobdella soleae has not been clearly defined in the current literature. However, studies reference specimens of 2 to 6 mm in length. Entobdella soleae exhibits the typical monogenean body plan. It is flat, translucent, and has a large, disc-shaped haptor, a posterior organ used for semi-permanent attachment to the host. A distinguishing feature of the organism is its unique prohaptor, an anterior structure with two adhesive pads. These adhesive pads secrete a strong cement that temporarily attaches the organism to a substrate and are critical for locomotion.
Range length: 2 to 6 mm.
Other Physical Features: ectothermic ; bilateral symmetry
There are no known predators of Entobdella soleae reported in literature.
Due to the relatively low population density of Entobdella soleae in the wild, (1 to 3 individuals per host), it has been suggested that there is a mechanism for pheromonal attraction between individuals. This is supported by the fact that there is a layer of stagnant water between the host sole and the sea floor. This small but stable volume of water would allow for pheromones to be transmitted without interruption from current and may be part of the reason that adults migrate to the lower surface of the host. Due to the lack of concrete evidence, however, the exact mechanism for the attraction of mates has yet to be determined.
Entobdella soleae is a protandrous hermaphrodite that reproduces sexually. Although each organism houses both male and female organs, it is believed that self-fertilization is not possible due to the fact that the male reproductive organs cease to operate at the same time the female reproductive organs become active. Clutch size and gestation period of this hermaphroditic monogenean are highly variable depending on the size of the individual. One study found that medium to large individuals may produce 30 to 60 eggs a day with gestation periods lasting anywhere from 5 seconds to 168 minutes. Additionally, as the size of the organism increases, there is a slight increase in the size of the eggs produced.
Range gestation period: 0.08 to 168 minutes.
Key Reproductive Features: iteroparous ; sequential hermaphrodite (Protandrous ); sexual ; oviparous
Entobdella soleae does not provide any parental involvement.
Parental Investment: no parental involvement
Entobdella soleae is a monogenean (Platyhelminth) skin parasite of the common sole, Solea solea, an important food fish. They are approximately 2 to 6 mm in length. It is flat, translucent, and has a large, disc-shaped haptor, a posterior organ used for semi-permanent attachment to the host.[1] Typically, 2-6 parasites are found on wild sole, but in intensive fish farms this can rise to 200-300 parasites per fish, causing skin inflammation and sometimes death of the sole. E. soleae can live up to 120 days in seawater.[2]
The life cycle of Entobdella soleae follows the life patterns of their marine bottom-living host. The Solea solea would bury itself in the sediment for some time each day. The parasites are attached to the bottom of their host, in which when their hosts bury themselves, the parasite lays their eggs. The eggs are anchored to the sea bottom so that they wouldn't be swept away by the water currents. When the eggs hatched the oncomiracidia emerges and invades the anterior part of the upper surface of the fish. This part of the fish is the only part that is exposed when the fish is buried. After entering and developing on the upper surface of the fish, it migrates down toward the lower surface of the fish where they reach sexual maturity. Adult parasite would distribute throughout the lower surface of the host and are oriented with the adhesive organ upstream.[3]
Entobdella soleae larvae are called oncomiracidia. They are free-swimming and ciliated. These oncomiracidia are likely to attach to the host's upper surface where they migrate forwards toward the fish's head and then migrate to the underside of the sole, where they remain.[4]
Entobdella soleae utilizes suction through a posterior disc-shaped haptor to achieve semi-permanent attachment to the sole's skin.[5] E. soleae demonstrate host-specific behavior by attaching to the sole epidermis by the presence of sole mucous cells.[6]
The characteristic of the pad tegument might demonstrate a possible role in detachment of the parasite to the host. These features include an isolated tegument and the microvillus surface network of the pad tegument.[5]
The surface of the adhesive pads of E. soleae is encompassed by tegument that contains perforations of numerous rod-carrying ducts through pepper-pot apertures and ducts of spheroidal secretory bodies. Rods are distributed uniformly and intensely electron-dense within their ducts. Spheroidal secretory bodies are both tightly packed and have less electron density than rods. Moreover, the tegument on the surface of the parasite is isolated from the general tegumentary syncytium by a cell boundary. The tegument also contains secretory bodies.[5]
A 4-5 µm layer of cement bonds the adhesive pad of E. soleae via tegumental microvilli and the sole's epidermal furrows during attachment. Rod-shaped secretory bodies are the major substance of the cement.[5]
During locomotion on the skin of the sole, the anterior region of E. soleae temporarily attaches to the skin via two pads through an adhesive secretion. These adhesive pads contain two glandular secretions packaged in rods and spheroidal bodies. The locomotion step of E. soleae on the skin sole starts through elongation of the body with the haptor attached. Before attachment of the adhesive pads to the sole's skin, liquid spheroidal bodies quickly spread across the surface of the adhesive pads and bundles of rod-like secretory bodies leave the pepper-pot apertures of rod-carrying ducts. The synergy of both secretions produces the cement that binds the parasite to the host.[5]
The post-larval migration of E. soleae on the host’s surface ranges from 10–40 days; maintenance of navigational signals must remain intact over the entire period of migration.[7]
During migration, E. soleae larva utilizes the physical features of the host's scales as guidance for movement towards the head. The haptor attaches to the host’s scales as a lock and key mechanism where the axis of the haptor aligns with the longitudinal axis of the sole towards the head.[7]
Adult E. soleae lays tetrahedral eggs that have a tanned protein shell. A detachable operculum constitutes one of the tetrahedron corners of the egg. The cap-like operculum is bonded to the rest of the egg-shell by a thin cement layer. The opercular bond is strong, and operculum detachment only occurs through the actions of oncomiracidium and the secretion of hatching fluid by glands from the head region. The oncomiracidium of E. soleae escapes through an aperture of the operculum during hatching.[8]
The eggshell of E. soleae has a similar structural appearance to those of Fasciola hepatica, but without a membrane on the egg-shell lining. The egg's shell is produced by integration of shell material droplets from vitelline cells. Hatching occurs via chemical removal of the opercular cement and physical rupture of the rest of the egg-shell and opercular bond.[8]
Egg hatching of E. soleae induces a releaser response where the larva swims up and down the water column in the ocean to find the sole host.[7]
E. soleae consist of two hatching strategies: quick hatching in the presence of sole skin mucus and spontaneous hatching in the absence of the host. During the natural cycle of illumination, egg hatching is rhythmical: most larvae emerge a few hours after dawn. When fully developed eggs are in contact with sole body mucus during the illumination cycle, hatching is enhanced. The enhanced egg hatching indicates that the sole body mucus contains a potent hatching stimulant.[9]
Entobdella soleae is a monogenean (Platyhelminth) skin parasite of the common sole, Solea solea, an important food fish. They are approximately 2 to 6 mm in length. It is flat, translucent, and has a large, disc-shaped haptor, a posterior organ used for semi-permanent attachment to the host. Typically, 2-6 parasites are found on wild sole, but in intensive fish farms this can rise to 200-300 parasites per fish, causing skin inflammation and sometimes death of the sole. E. soleae can live up to 120 days in seawater.
Entobdella soleae is een soort in de taxonomische indeling van de platwormen (Platyhelminthes). De worm is tweeslachtig en kan zowel mannelijke als vrouwelijke geslachtscellen produceren. De soort leeft in zeer vochtige omstandigheden.
De platworm behoort tot het geslacht Entobdella en behoort tot de familie Capsalidae. De wetenschappelijke naam van de soort werd voor het eerst geldig gepubliceerd in 1864 door van Beneden & Hesse.
Bronnen, noten en/of referenties
