Solmissus incisa
Introduction
Solmissus incisa, commonly known as the dinner plate jelly, is an intriguing species of deep-sea jellyfish belonging to the family Solmissidae. This bioluminescent organism inhabits the mesopelagic zone of both the Atlantic and Pacific Oceans. Known for its distinctive flattened bell shape and long trailing tentacles, Solmissus incisa exhibits a unique life history and predatory behavior. Although previously classified as a single species found worldwide, recent research indicates that it may actually comprise multiple closely related species, varying in form and distribution.
Etymology and Common Name
The common name “dinner plate jelly” aptly describes the broad, flattened shape of its bell, which resembles a dinner plate when viewed from above. The scientific name “incisa” is derived from the Latin word meaning “cut” or “notched,” referring to the small indentations that encircle the edge of the bell. This nomenclature highlights the jellyfish’s distinctive morphology and helps in understanding its classification within marine biology.
Description
Solmissus incisa is characterized by its transparent body and broad, flattened umbrella, which can often appear almost colorless. The bell typically takes on a circular shape, contributing to the species’ plate-like appearance. Internally, the stomach and reproductive tissues may exhibit a pale white coloration. The number of tentacles on individuals of Solmissus incisa can vary, typically ranging from 22 to 24. This variation is attributed to differences in manubrial pouches—sac-like lobes located around the stomach and mouth at the center of the bell. Such variations suggest that what was once considered a singular species might encompass several cryptic species.
This jellyfish swims by contracting its bell and utilizes its long tentacles equipped with nematocysts—specialized cells that contain venomous barbs—to capture prey and defend against predators. These adaptations make Solmissus incisa an efficient predator in its deep-sea habitat.
Taxonomy and Phylogeny
Belonging to the order Narcomedusae, Solmissus incisa represents a group of hydrozoans that spend their entire lives suspended in the water column rather than adopting a benthic polyp stage, which is characteristic of many other hydrozoan species. Recent molecular studies have revealed significant genetic diversity among populations previously classified under Solmissus incisa. Observations indicate that these populations can differ morphologically and genetically from one another depending on their oceanic environments. As such, it has been proposed that this jellyfish may consist of several closely related species rather than being a single global entity.
Evolution
The evolutionary trajectory of Solmissus incisa is particularly noteworthy as it diverges from many other hydrozoans by not undergoing a benthic polyp stage in its life cycle. This adaptation allows for a fully planktonic existence throughout its life, which is thought to facilitate survival in deep pelagic environments where suitable surfaces for attachment are scarce. This evolutionary strategy aligns with the challenges posed by the deep-sea ecosystem, enabling Solmissus incisa to exploit available resources effectively.
Life Cycle and Reproduction
The life cycle of Solmissus incisa is distinct in that it does not include a benthic polyp stage like many other jellyfish species. Research conducted in the western North Atlantic suggests that individuals transition directly from larval stages into juvenile medusa. It is believed that reproduction occurs through sexual means via broadcast spawning; adults release eggs and sperm into the surrounding water for fertilization. Following this process, embryos develop into actinula larvae before maturing directly into juvenile medusa.
Juvenile Solmissus incisa start with only a few tentacles but gradually develop more as they grow larger. Interestingly, some adults have been observed with small cnidarian-shaped structures attached to their bells, which have led researchers to speculate about complex developmental stages within this species. These structures may represent brooded offspring or could potentially be parasites; however, definitive identification remains elusive.
Size
The size of Solmissus incisa varies significantly among individuals. Typically, adult jellies exhibit bells measuring several centimeters across, although some specimens can exceed 10 cm in diameter. The length of their tentacles often surpasses that of their bell diameter by several times, allowing them to effectively capture prey when extended forward or trailing behind them while swimming.
Habitat and Distribution
This mesopelagic species thrives at depths ranging primarily between 300 to 700 meters but has also been recorded at depths exceeding 1000 meters. Most sightings occur within specific depth ranges of 300–500 meters and 600–700 meters. Solmissus incisa has been observed predominantly in regions such as the North Pacific, North Atlantic, Gulf of Mexico, and temperate/tropical Pacific waters. Environmental conditions during sightings indicate a preference for temperatures between 11 and 12 degrees Celsius, alongside salinities ranging from 34 to 35 PSU.
Diet
As an active predator within its ecosystem, Solmissus incisa primarily feeds on gelatinous zooplankton including salps, other medusae, siphonophores, larvaceans, and various narcomedusae species. Utilizing its long tentacles equipped with nematocysts for capturing prey, once caught, food is transferred to its mouth for digestion. An interesting discovery was made when a specimen collected near Kaikata Seamount off Japan contained a whole fish in its stomach—a first recorded instance indicating that this jellyfish may consume larger prey than previously understood.
Predators and Prey
While Solmissus incisa is an effective predator itself, it likely faces predation from larger deep-sea fish, turtles, and other gelatinous organisms; however, specific predators remain poorly documented in scientific literature. Its diet mainly consists of gelatinous animals and assorted zooplankton including salps and siphonophores.
Parasites
Instances have been recorded where small opaque circular structures were found attached to the bell of Solmissus incisa. These structures were identified as juvenile cnidarians embedded within the medusa’s epidermis capable of extending and retracting their tentacles. Whether these organisms are parasitic or represent brooded offspring continues to be an area for further research.
Ecology
Solmissus incisa plays an important role as a predator within deep-sea food webs. By consuming other zooplankton species, it contributes significantly to carbon movement and energy transfer throughout pelagic ecosystems. Seasonal observations suggest that sightings are more prevalent during spring months between March and May when environmental conditions are favorable.
Conclusion
The study of Solmissus incisa reveals much about deep-sea ecosystems and highlights the complexity of marine life forms inhabiting these environments. As research continues to uncover variations within this species’ populations across different oceans, it underscores the necessity for ongoing exploration into jellyfish biodiversity and ecology in our oceans’ depths.
Artykuł sporządzony na podstawie: Wikipedia (EN).