Nebalia bipes

Geographic Range

Nebalia bipes is native to coastal waters throughout the North Atlantic, extending from the eastern Nearctic region to the northernmost parts of the Palearctic region. Within the Palearctic region, it has been identified near the shores of the Greenland, Iceland, Faeroes, Norway, and Spitsbergen, and in the Kattegat, North Sea, English Channel and the Mediterranean, where it has been found on the coast of Italy. This also makes it a Holarctic species.

• Biogeographic Regions
• nearctic nearctic
  • native native
• palearctic palearctic
  • native native

• Other Geographic Terms
• holarctic holarctic

Habitat

Small marine crustaceans in the order Leptostraca , live in coastal temperate, tropical, and saltwater environments ranging anywhere from 1 to more than 2,000 m in depth. Nebalia bipes stays closer to the surface, preferring to inhabit zones between 5 and 60 m in depth. In addition to coastal areas, Nebalia bipes is also able to inhabit estuarine environments and areas with brackish water, such as the North Sea. They prefer to bury themselves under soft clay beneath rocks with little-to-no exposure to light and low oxygen levels. N. bipes lives in close association with submerged detritus accumulations and the macrofauna found within them, thriving in the lower stratum layer.

• Habitat Regions
• temperate temperate
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• coastal coastal
• brackish water brackish water

• Other Habitat Features
• estuarine estuarine

Physical Description

The body of Nebalia bipes is slender, with the characteristic crustacean anatomy of an anterior head, middle thorax, and posterior abdomen. It has no cephalothorax and its thoracic segments are not fused with its head. Fully grown, Nebalia species have a maximum length of 17 mm, but tend to stay around 4.5 mm in the wild. Nebalia bipes is milky-white to translucent in appearance, with antennae below its eyes and an abdomen composed of seven segments, instead of the usual six. It has a hinged rostral plate covering its head, which is laminar and lacks a terminal spine. A large, rounded bilobed carapace covers its thorax and most of its abdomen. This protects its first and second maxilla, its carapace abductor, and the palp of its maxillula.

Nebalia bipes has well-developed, red-pigmented eyes due to a high concentration of carotenoids and a lack of ommochromes present in most other crustacean eyes. Both male and female Nebalia bipes have first antenna pairs that are shorter in length than their second antenna pairs. The second antenna pair is whiplike and longer in males, reaching lengths close to the length of their bodies. The first four pairs of pleopods in the thorax are biramous, and the last two are uniramous and rudimentary. The abdomen of Nebalia bipes terminates in a caudal furca with long rami. This is unusual for animals in the class Malacostraca , but common in other crustacean groups. The rami are narrow and longer in males than in females.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• ornamentation ornamentation

Development

It should be noted that the developmental processes of animals in the genus Nebalia closely resembles that of animals in the subclass Eumalacostraca . Nebalia bipes transitions from an unripened egg in the ovary to a four-celled embryo within a few hours. This freshly laid egg has a central nucleus and a mostly-central cytoplasm. Following the thickening of the blastophore, a U-shaped germinal band is formed where the arm segments are developed. The mesodermal mass then becomes differentiated into an anterior mesoderm and posterior endoderm, which separates malacostracans from other crustaceans. Once the papilla elongates and all the segments are differentiated internally, the unhatched Nebalia bipes embryo extends anteriorly to the labrum and is ready to hatch from the vitelline membrane. The embryo then passes through three stages separated by ecdyses, leaves the brood pouch, and becomes free-swimming as a benthic juvenile. During its gastrulation period, all internal tissues are formed and the ectoderm and mesoderm of all seven abdominal segments are established. The gonads then secrete either a male or female hormone. The genital rudiment appears when the species is about 3 mm long, notably late in embryonic life. The adult populations of Nebalia bipes vary greatly, with males being comparatively scarce. The rudiment appearance also marks the beginning of the premature adult stage. All major parts of its exoskeleton are now formed from the mandibular-maxillary bars, and the development of both the antennal gland and maxillary gland commence. Nebalia bipes from this point forth is considered to be in its fully-developed adult form.

Reproduction

Nebalia is a polygynandrous genus in the order Leptocrustraca and can reproduce during all seasons. To find and attract mates, Nebalia bipes exhibits a circadian periodicity swimming rhythm, which is transmitted hereditarily. Nebalia bipes is highly adaptable and can breed with relative ease.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

There is no set breeding season for Nebalia bipes and the species begins to reproduce after 30 to 100 days of life, depending on water temperature. Reproductive maturity happens faster in warmer waters. Females lay between 20 to 80 eggs per litter, increasing proportionally with the size of mothers.

All embryonic development takes place within a maternal incubating cavity enclosed by long feathery bristles, carried by the end of the endopodites of the thoracic appendages. Young are incubated from 10 to 20 days, depending on the water temperature. At a stable 18°C, incubation lasts for a dozen days. Young only leave the incubation cavity after having acquired a complete adult structure.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• ovoviviparous ovoviviparous

Parental investment for Nebalia bipes includes internal fertilization of their young, spending 10 to 20 days developing the embryonic papilla in the maternal incubating cavity. With this investment, Nebalia bipes feed its young by use of a yolk sac, which in early stages has such a high rate of absorption that the volume of the sac increases and can be utilized after hatching. The yolk sac later develops into the liver and intestines. This method of parental care is less expensive than milk production seen in Mammalia. However, this also means Nebalia bipes has less acute hearing and sense of smell. There are no documented cases of benthic juveniles learning from their parents, rather young seem to develop a natural rhythm of synchronization within a day of incubation release in a natural daylight cycle. Thus, paternal investment pre-independence seems to be little to none.

• Parental Investment
• precocial precocial
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female

Lifespan/Longevity

Not much is known about the lifespan of Nebalia bipes in the wild. However, it does exhibit the natural pattern that finds the sooner an individual has offspring, the sooner it dies. In captivity at 18°C, a female can survive for up to 10 months after producing three broods - the first brood is produced at the 80-day mark. This suggests there is a life-to-birth ratio of 3.75, making their lifespan less than those reported for other leptostracan species. Limits to the lifespan of Nebalia bipes include water temperature, water depth, and dissolved oxygen concentration.

Behavior

Nebalia bipes is a colonial species, and can be found in populations of 2 million or more. It also has a mobile adult form, that locomotes with its twelve pleopods, one for each side of the six abdominal segments, excluding the seventh segment which houses the telson. Pleopods 1 to 4 are large and biramous and are all found on the specialized abdomen. These biramous appendages help Nebalia bipes swim. Locomotion in Nebalia bipes could be used as a model for Palaeozoic phyllocarid crustaceans, as the functional importance of the natatory pleopods suggests a similar free-swimming lifestyle with burrowing habits. Species in the genus Nebalia are known as 'sea fleas' due to their similar appearance and tendency to bite flesh if convenient to them. However, unlike the flea order Siphonaptera , Nebalia species are not parasitic and only attack humans if they get too close to their food source or have a cut and are stagnant in the water.

• Key Behaviors
• natatorial natatorial
• motile motile
• sedentary sedentary
• colonial colonial

Home Range

Nebalia bipes generally stays within detritus mat fauna - that is stratified dead plant material on the ocean floor - for its entire life. However, there is higher dispersion in Summer as mats expand and less dispersion as mats contract in Winter and Spring. Nebalia bipes displays a circadian swimming rhythm and is more active at night and dusk than during the day.

Communication and Perception

Nebalia bipes has well-developed eyes for visual communication and two sets of antenna for tactile communication. Its eyes are bright red from the high concentration of carotenoids in the water and low exposure to light compared to other crustaceans. Nebalia bipes is thought to use vision less often tactile communication. The second sets of antennae on Nebalia bipes can grow as long as the body in males and are mostly used as ornamentation, but still work as sensory organs. Species in the genus Nebalia use their antennae for the majority of communication and perception, but there are minimal studies to characterize their exact communication patterns.

• Communication Channels
• visual visual
• tactile tactile

• Perception Channels
• visual visual
• tactile tactile

Food Habits

Nebalia bipes is a scavenger and detritivore, consuming dead and dying marine creatures found on the seafloor. It eats using its three mouthparts, the paired uniramous mandibles, uniramous first maxillae, and biramous second maxillae. Food availability is limited by light availability because their nutrients are photosynthetic and rooted in unstable substratum in coastal sediments.

• Primary Diet
• carnivore carnivore
  • scavenger scavenger
• detritivore detritivore

• Animal Foods
• aquatic crustaceans
• zooplankton zooplankton

• Plant Foods
• phytoplankton phytoplankton

• Other Foods
• detritus detritus

Predation

Fishes are the only abundant predators known to prey on Nebalia bipes . Due to its widespread location in coastal waters, the species of fish that prey on Nebalia bipes are foraging fish, including members of the family Clupeidae and other small fish such as halfbeaks, silversides, and smelt.

The only known method Nebalia bipes utilizes to avoid predation is taking refuge in detritus matter on the seafloor. Larger refugia increase the carrying capacity, which allows for both greater population sizes and reproduction rates.

Ecosystem Roles

In their detritus-dominated habitats, Nebalia species are heavily preyed on during all seasons by various fishes. They also help with biodegradation. They can account for over 99% of species found within detritus mat, proving to have a large ecosystem role in coastal waters as prey. Their ability to biodegrade waste also helps with the three stages of biodegradation, contributing to biodeterioration. This process is possible because they interact with abiotic factors, facultative anaerobic bacteria, aerobic bacteria, and microorganisms.

• Ecosystem Impact
• biodegradation biodegradation

Economic Importance for Humans: Positive

Being the only living members of the order Leptostraca , species in the genus Nebalia serve as valuable research opportunities and education of extinct methods of locomotion, reproduction, and general behavior. Nebalia bipes was the first species in its order to be described in 1780, and periodic research makes it one of the more studied marine crustaceans. This offers more history on methods of evolution in the class Malacostraca , which is not found in more adapted species.

• Positive Impacts
• research and education

Economic Importance for Humans: Negative

There are no known adverse effects of Nebalia bipes on humans.

Conservation Status

There is no special conservation status Nebalia bipes or other Nebalia species. There are no known causes of endangerment to their populations. However, all wildlife found in coastal waters experience human interference of tidal action, as humans use sea defenses to prevent flooding, limiting the coastal range of inhabitants. Tidal action is a potential problem for this species, as they live in lower coastal depths, and this action removes parts of their habitat.

Additional Links

Encyclopedia of Life

Contributors

Allison Clark (author), Colorado State University, Brooke Berger (editor), Colorado State University, Galen Burrell (editor), Special Projects.

References

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