Thalassinidean shrimp are among the most common burrowing organisms of marine intertidal and shallow subtidal environments, and may be common in deep-sea habitats as well. These organisms rely on self-constructed burrows for a wide variety of needs including shelter, reproduction, and feeding. Except for a larval phase which may be pelagic, most thalassinidean shrimp spend their entire life within the burrow. (Griffis and Suchanek 1991)
One well known thalassinidean on the Pacific coast of North America is the ghost shrimp Neotrypaea californiensis (formerly known as Callianassa californiensis), which burrows in muddy sand with enough clay and organic matter to make it reasonably cohesive and to provide material for lining its tunnels. This shrimp has a waxy pale pink and orange appearance. The largest individuals may reach 10 cm (excluding appendages). Burrows usually have a number of branches and turnaround chambers, with at least two openings to the surface, providing for some circulation of seawater through the tunnel system. Burrow openings are typically in the middle of little piles of sand or sand mixed with small pebbles. (Kozloff 1993)
This shrimp is abundant in mud flats of bays and estuaries on the west coast of North America. Individuals average from 5 to 8 cm in length and vary from a whitish yellow to orange-red. A striking feature is the possession of an exceedingly large cheliped, or claw, which may be on either the right or left side. This inequality in size of the chelipeds is largely a sexually dimorphic trait, for in the females the difference between left and right is much smaller. (MacGinitie 1934)
These shrimp, which are awkward and relatively helpless outside their burrows, are found most abundantly in tidal regions from zero to one foot in depth, and are restricted to bottoms of mixed sand and mud of a consistency that allows the construction of fairly permanent burrows. Neither very loose sand nor very soft mud will work. Individuals are occupied almost constantly in extending or adding new tunnels to their burrows, which often connect with those of other individuals (such connections, however, are continually being blocked off and tunneled around). The burrows are extensive and are being added to continually because the animals sift sandy mud to extract detritus, which constitute this shrimp's diet. The continual turning over of the soil and the aeration of the subsoil by the burrows of this shrimp are important to the entire community of mud-dwellers, and a variety of other species are commonly found on the bodies and in the burrows of these shrimp. (MacGinitie 1934) These associated animals include pea crabs; the scaleworm Hesperonoe complanata; a small clam, Cryptomya californica, whose siphons open into the burrow instead of to the surface; and the goby Clevelandia ios (although not restricted to Neotrypaea burrows, this small fish is regularly found in their vicinity). (Kozloff 1993) The presence of burrowing Neotrypaea californiensis may increase or decrease populations of other marine soft-sediment species (Posey 1986).
Predators include fish such as staghorn sculpin. Commensals in the burrow include the polychaete scaleworm Hesperonoe complanata, the snapping shrimps Betaeus harrimani and B. ensenadensis, and the pea crabs Scleroplax granulata, Pinnixia franciscana, and P. schmitti, the burrowing clam Cryptomya californica, and the goby Clevelandia. Commensals on the animal include the copepods Clausidium vancouverense and Hemicyclops thysanotus, as well as the parasitic isopod Ione cornuta on the gills.
Neotrypaea californiensis can be found at intertidal locations within the regions of the North American West Coast ranging from Mutiny Bay, Alaska to Tijuana River, San Diego County, California and El Estuario de Punto Banda, Baja California Norte, Mexico.
Biogeographic Regions: nearctic (Native ); pacific ocean (Native )
Neotrypaea californiensis is found in the middle to low intertidal zone from southeastern Alaska to Baja California (Dumbauld et al.1996 and references therein).
Neotrypaea californiensis is found in soft sediment habitats in estuaries and coastal lagoons from southern Alaska to northern Mexico (MacGinitie 1934; Morris et al. 1980, cited in Pernet et al. 2008).
Body coloration ranges between shades of orange, pink, and red. Some individuals may also exhibit a very pale coloration, almost white. The main body parts of Neotrypaea californiensis follow a generalized decapod body plan: two differently-shaped claws (with one major cheliped, often several times larger than the opposite claw); five pairs of legs, three paddle-shaped swimming legs (pleopods), a fan-like tail (uropod), telson, flattened eyestalks, and two pairs of antennae. The exoskeleton is fringed with numerous fine hairs.
Females bearing eggs carry them on their abdomen. The egg mass may vary in color between individuals, from light yellow to deep scarlet. The major cheliped is sexually dimorphic, being larger on males. The major cheliped can account for up to a quarter of a ghost shrimp's weight.
Average mass: 1-5 g.
Average length: 10-12 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: male larger; sexes shaped differently
Labadie and Palmer (1996) conducted a morphometric analysis of claw size and shape variation in the strikingly heterochelous (i.e. having very different chelae, or claws) ghost shrimp Neotrypaea californiensis. Master claws approached 25% of total body weight in mature males, but rarely exceeded 10% in females. Minor claws were less than 3% of body weight in both sexes. The proportions of right versus left master claws did not differ significantly from 50:50. Males exhibited a greater positive allometry (disprortionate growth of claws) than did females in both master and minor claw size, but master claws differed more than minor claws. Sexual dimorphism was also observed in master, but not minor, claw shape: compared to females, mature male master claws: a) were proportionally higher relative to their length; b) exhibited a deeper propodal notch and consequently a larger gape; c) developed a more slender and more distally hooked dactyl; and d) exhibited more well-developed teeth around the periphery of the claw gape. Evidence suggests that the evolution of these unusual master claws has been significantly influenced by sexual selection.
In males, the major claw is often twice as long as the minor claw; in females, the major claw exceeds the minor claw by less than 50% in length (Carlton 2007).
Neotrypaea gigas is very similar to N. californiensis, though the claw of the adult male N. gigas is longer and more slender than that of N. californiensis (Brusca and Brusca 1978; see Brunet et al. 2008 and references therein for other characters distinguishing these two species). The Blue Mud Shrimp (Upogebia pugettensis) has a faint bluish color and lacks an oversized claw (Brusca and Brusca 1978). It is much hairier than N. californiensis and usually does not heap up sand around the burrow openings. It may occur in even muddier areas than those where N. californiensis is found, though the two species often occur together. (Kozloff 1993)
Neotrypaea californiensis live as infauna in intertidal areas between the middle to low intertidal zones, on sandy beaches or tidal flats in estuaries. Ghost shrimp habitat is distinguished by numerous holes that are the entrances and exits of their burrows. Ghost shrimp are constantly excavating complex tunnels under the sand.
Although the majority of time is spent building tunnels, ghost shrimp do come to the surface at times, where predation can occur.
Range depth: 0.76 (low) m.
Habitat Regions: saltwater or marine
Aquatic Biomes: benthic ; coastal
Other Habitat Features: estuarine ; intertidal or littoral
Water temperature and chemistry ranges based on 4 samples.
Depth range (m): 0 - 110
Temperature range (°C): 8.291 - 9.107
Nitrate (umol/L): 9.815 - 23.764
Salinity (PPS): 32.654 - 33.431
Oxygen (ml/l): 3.698 - 5.588
Phosphate (umol/l): 1.205 - 1.945
Silicate (umol/l): 16.608 - 31.690
Depth range (m): 0 - 110
Temperature range (°C): 8.291 - 9.107
Nitrate (umol/L): 9.815 - 23.764
Salinity (PPS): 32.654 - 33.431
Oxygen (ml/l): 3.698 - 5.588
Phosphate (umol/l): 1.205 - 1.945
Silicate (umol/l): 16.608 - 31.690
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
Habitat: Intertidal in muddy sand. In areas of compact mud the burrow entrances may appear as small "volcanoes" on the surface
Ghost shrimp ingest plankton and detritus deposits scraped from the sediments during burrowing. Plankton is also obtained as water and detrital materials pass over the body and are collected on the hairs of their second and third walking legs.
To find enough food, ghost shrimp tunnel almost constantly, reworking the sediment to a depth of as much as 76 cm.
Animal Foods: aquatic or marine worms; zooplankton
Plant Foods: phytoplankton
Other Foods: detritus
Foraging Behavior: filter-feeding
Primary Diet: planktivore ; detritivore
Neotrypaea californiensis is a deposit feeder, ejecting a portion of the material processed in the burrow to produce the surface mounds. (Griffis and Suchanek 1991).
The vigorous burrowing activities of ghost shrimp have such dramatic effects on their habitats of soft sediment that these animals are often considered ecosystem engineers. By aerating the surface sediment through burrowing, the ghost shrimp provide an environment attractive to other species including the blind goby, three species of pea crabs, two species of clams, a copepod, a shrimp, polynoid worms, and isopods, all of which live within the burrows.
Ecosystem Impact: creates habitat; soil aeration
- mudflat visor shrimp, Betaeus ensenadensis
- copepods, Hemicyclops thysanotus, Clausidium vancouverense
- polynoid worms, Hesperonoe
- arrow goby, Clevelandia ios
- pea crab, Scleroplax granulata
- pea crabs, Pinnixa franciscana, P. schmitti
Although ghost shrimp typically inhabit deep burrows, they are susceptible to predation because they sometimes venture outside of their burrow entrances. Fishes and invertebrates are significant predators when the tide is high, whereas shorebirds and humans prey on ghost shrimp when the tide is low. Shorebirds that feed on ghost shrimp include the long-billed curlew Numenius americanus and the willet Catoptrophorus semipalmatus. Some fish predators include the Pacific staghorn sculpin, Leptocottus armatus.
- Pacific staghorn sculpin, Leptocottus armatus
- Long-billed curlew, Numenius americanus
- Willet, Catoptrophorus semipalmatus
Weitkamp et al. (1992) observed Gray whales (Eschrichtius robustus) in Puget Sound, Washington, U.S.A., creating feeding pits on littoral sand flats dominated by ghost shrimp (Neotrypaea californiensis). The whales removed an extensive biomass of shrimp from the pits. Ghost shrimp standing stock was 2 to 5 times lower inside than outside feeding pits, equivalent to a removal of 3 to 6 kg of shrimp per pit. An estimated 2700 to 3200 feeding pits were present on 19 km of sand flat in 1990, while 19000 feeding pits were documented over the same region in the spring and summer of 1991. Weitkamp et al. estimated that 10 to 12 and 75 tons of shrimp were removed from the pits in 1990 and 1991, respectively. Ghost shrimp represent an energetically valuable prey for gray whales, providing 2 to 15 times higher standing stocks than any other reported prey. (Weitkamp et al. 1992)
Many Neotrypaea californiensis bear symbiotic copepods (Clausidium vancouverense). These small reddish copepods (about 2 mm) can be seen through the translucent portion of the carapace covering the gills (it is unclear whether these they affect host fitness). A related species, Hemicyclops thysanotus, may also be present. In the northern part of their range, Neotrypaea californiensis may be infected by the parasitic bopyrid isopod Ione cornuta, the presence of which is indicated by the carapace bulging in the gill region where it is attached beneath. The fat, asymmetrical female, up to about 2 cm long, is accompanied by a small, slender male. (Kozloff 1993; Pernet et el. 2008) Pernet et al. (2008) discuss the risk of inadvertently introducing this parasite to southern California, where it is apparently not native, via the live bait trade. Pernet et al. found live, brooding I. cornuta at high frequencies (5.8% overall) among ghost shrimp imported from Oregon or Washington and purchased from three southern California bait shops in 2005 to 2007. This is likely higher than in the populations from which these bait shop ghost shrimp were collected, given that their overall estimate of prevalence in northern populations was 1.1% (though the authors note that there is likely among-estuary variation in prevalence that they not detect). Pernet et al. suggest that the higher prevalence of bopyrids in bait shop populations could be due to the preferential harvesting of larger ghost shrimp by bait diggers--as in many host-parasite interactions, larger ghost shrimp are probably more likely to be infected (O’Brien and Van Wyk 1985). The limited data available on the relationship between bopyrid infection and ghost shrimp reproductive status support the hypothesis that I. cornuta prevent successful reproduction in female hosts. (Pernet et al. 2008 and references therein)
Life History and Behavior
Tactile: This species uses its antennae, chelipeds, and sensory hairs (called cuticular mechanoreceptors, covering most of the body) to sense physical objects in the environment.
Vision: Eyestalks are acute with divergent tips, and bear a pigmented cornea in the middle of the eyestalk.
Communication Channels: visual ; tactile ; chemical
Perception Channels: visual ; tactile ; chemical
MacGinitie (1934) provides a detailed description of burrowing behavior, as well as a discussion of the functions of the various appendages in offense and defense, walking, digging, feeding, swimming, cleaning, and so on.
Neotrypaea californiensis matures between 18 and 24 months. Mature individuals can be found closest to the ocean and they grow much faster compared to individuals located nearer to shore. Larger sized females with larger eggs can be found within intertidal areas.
Females carry their fertile eggs on their abdomen and the eggs are released in June or July. The newly released ghost shrimp larvae (zoea) drift for six to eight weeks in the water column as zooplankton, passing through five zoeal stages before transforming into a megalops. There zoeal stages take place over 6 to 8 weeks. They will return to estuarine habitats as megalopae on flood tides during August.
Ghost shrimp in the wild have an average lifespan of 3-5 years. The primary factor affecting lifespan is the level of available nutrients. Nutrient availability is directly related to the distance of the colony to an estuary. Longer-lived shrimp are found closer the mouth of an estuary.
Status: wild: 5 years.
Status: wild: 3-5 years.
Using olfactory receptors on their antennules called aesthetascs, a male ghost shrimp detects water soluble substances released by premolt females. Once a female is found, the male will follow and protect her from predators and other suitors with his major cheliped, until she molts. This process is known as temporary mate guarding. After the female molts, the male mates with her and then leaves her to find another premolt female.
Mating System: polygynandrous (promiscuous)
Though the mating behavior of the ghost shrimp is largely unknown, it is agreed that the males use the major cheliped to fight other males for reproductive access to females.
The female will carry her brood of eggs for approximately 3 to 5 months. Hatching occurs in June or July. The newly released ghost shrimp larvae (zoea) drift for six to eight weeks in the water column as zooplankton, passing through five zoeal stages before transforming into a megalops. They will return to estuarine habitats as megalopae on flood tides during August.
Breeding interval: April to August
Breeding season: Begins in April
Range number of offspring: 200 to 1,400.
Range gestation period: 3 to 5 months.
Average time to independence: Eggs are carried and protected by the female for 3- 5 months before hatching, releasing larvae into the water column as plankton months.
Average age at sexual or reproductive maturity (female): 18-24 months months.
Average age at sexual or reproductive maturity (male): 18-24 months months.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
Ghost shrimp reproduce seasonally. The female will carry her brood of eggs for approximately 3 to 5 months until they hatch, usually in June or July.
Parental Investment: precocial ; female parental care ; pre-hatching/birth (Protecting: Female)
In a study in Willapa Bay, Washington (U.S.A.), ovigerous (egg-bearing) Neotrypaea californiensis were found throughout spring and summer (April to August). Females extruded red eggs in spring that developed and hatched from June to August (evidenced by the presence of empty egg cases on the pleopods, or "swimming legs"). The average density of N. californiensis was 150 to 450 shrimp per square meter (an intermediate density compared to other studies). Females reach sexual maturity at 2 to 3 years of age. The egg-brooding period for these shrimp is 5 to 6 weeks. Females invest about 30 to 40% of their body weight in egg production, producing thousands of eggs each. (Dumbauld et al. 1996 and references therein)
Evolution and Systematics
Systematics and Taxonomy
Manning and Felder (1991) published a revision of the American Callianassidae in which they proposed a new genus, Neotrypaea, to which they transferred the shrimp then known as Callianassa californiensis. This change has been widely accepted (e.g., Carlton 2007).
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Relevance to Humans and Ecosystems
No known negative economic importance for humans.
Neotrypaea californiensis is used as live bait by fishermen. Fishermen commonly call them one-armed bandits because of their one long cheliped.
Positive Impacts: food
Neotrypaea californiensis is sometimes treated as a pest by commercial oyster farmers in Washington State, U.S.A., who may spray sediments with carbaryl (an organocarbamate pesticide) at low tide to control shrimp populations. The activities of the shrimp increase turbidity and sediment deposition rates and reduce the compaction of intertidal sediments. The chronic disturbance from their burrowing causes oysters and other sessile (stationary) bivalves, especially settling larvae and spat, to either sink into the mud or be smothered and die. (Dumbauld et al. 1996 and references therein) Carbaryl applications kill not only the shrimp but non-target species as well, including economically important ones such as Dungeness Crabs (Cancer magister) and English Sole (Parophrys vetulus). Commercial crabbers and other groups who have economic, recreational, and environmental interests in the estuaries have generally opposed these chemical applications that oyster growers maintain is essential to sustain production levels. This conflict and associated policy issues were reviewed by Feldman et al. (2000).
Neotrypaea californiensis (formerly Callianassa californiensis), the Bay ghost shrimp, is a species of ghost shrimp that lives on the Pacific coast of North America. It is a pale animal which grows to a length of 11.5 cm (4.5 in). One claw is bigger than the other, especially in males, and the enlarged claw is thought to have a function in mating. N. californiensis is a deposit feeder that lives in extensive burrow systems, and is responsible for high rates of bioturbation. It adversely affects oyster farms, and its numbers are controlled in some places by the application of pesticides. It carries out an important role in the ecosystem, and is used by fishermen as bait.
Description and life cycle
Adult N. californiensis have one claw larger than the other, and in the males, the "master claw" can make up as much as 25% of the animal's mass – compared to only 10% in females – with the minor claw making up around 3% of the total body mass in both sexes. The enlarged claw is equally likely to be on the right side or the left side. The male's larger claw is thought to be used in agonistic encounters or during mating, and may be the result of sexual selection.
N. californiensis was originally described in 1854 by James Dwight Dana as a member of the genus Callianassa, giving the type locality as "California"; the material Dana studied was probably collected from San Francisco Bay or Monterey, but the original specimens have since been lost. In 1991, Raymond Manning and Darryl Felder transferred the three species in that genus that come from California and Oregon into the new genus Neotrypaea. N. californiensis is distinguished from the other two species of Neotrypaea by the lack of a rostrum (which is present in Neotrypaea gigas) and the acute and diverging tips of the eyestalks (which are short, blunt and not diverging in Neotrypaea biffari).
Ecology and human impact
Both Neotrypaea californiensis and the mud shrimp Upogebia pugettensis live in mudflats and sandy substrates in the intertidal zone of estuaries in western North America. N. californiensis is found from Mutiny Bay, Alaska to Punta Abreojos, Mulegé, Baja California Sur, Mexico. Its habitat is also used for the aquaculture of the Pacific oyster, Crassostrea gigas. Since the bioturbation carried out by N. californiensis and U. pugettensis reduces the productivity of the oyster beds, they are considered pests. Their effects may, however, have knock-on effects across the entire ecosystem, and may buffer it from the hazards of nutrient enrichment and increase primary and secondary productivity by increasing the amount of dissolved inorganic nitrogen.
The burrows made by N. californiensis have many branches, and a number of other animals live in them, including snapping shrimp of the genus Betaeus, the copepod Clausidium vancouverense, and the crab Scleroplax granulata. The gut flora of N. californiensis includes a wide range of bacteria, comprising around 40% Alphaproteobacteria, 20% gram-positive bacteria, 20% in the Cryptophaga–Flavobacteria–Bacteroides group, and 5% of each of Gammaproteobacteria and Epsilonproteobacteria. Predators of N. californiensis include bottom-dwelling fish and Dungeness crabs (Metacarcinus magister).
N. californiensis has a negative impact on oyster production, and as a result, the insecticide carbaryl (1-napthyl N-methyl carbamate) is sprayed in some areas (including Willapa Bay, Washington) to reduce the population of N. californiensis. The addition of shelly debris also reduces numbers of N. californiensis both by preventing the settlement of larvae, and through predation on the young N. californiensis by young Dungeness crabs in the shelly debris.
N. californiensis is used as fishing bait, and is frequently transported alive between U.S. states, prompting fears that existing population structure may be obliterated, and that it could introduce the castrating parasitic isopod Ione cornuta outside its native range.
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