Bathyporeia pelagica

Researched By	Lizzie Tyler	Data Supplied By	University of Sheffield
Refereed by	This information is not refereed.
Taxonomy
Scientific name	Bathyporeia pelagica	Common name	Sand digger shrimp
MCS Code	S456	Recent Synonyms	None
Phylum	Crustacea	Subphylum
Superclass		Class	Eumalacostraca
Subclass	Peracarida	Order	Amphipoda
Suborder	Gammaridea	Family	Pontoporeiidae
Genus	Bathyporeia	Species	pelagica
Subspecies
Additional Information	The Gammaridea are difficult to identify and reference should be made to Lincoln (1979) for guidance.
Taxonomy References	Hayward & Ryland, 1995b, Hayward et al., 1996, Howson & Picton, 1997, Lincoln, 1979, Fish & Fish, 1996, Hayward, 1994
General Biology
Growth form	Articulate	Feeding method	Surface deposit feeder, Sub-surface deposit feeder
Mobility/Movement	Swimmer, Burrower	Environmental position	Infaunal
Typical food types	Organic matter	Habit	Free living
Bioturbator		Flexibility	High (>45 degrees)
Fragility	Intermediate	Size	Very small(<1cm)
Height	Insufficient information	Growth Rate	Insufficient information
Adult dispersal potential	100-1000m	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
Additional Information	Characteristic feeding method Bathyporeia pelagica is an epistrate feeder, individual sand grains are rotated by the mouth parts and organic matter removed, essentially 'sand-licking' (Fish & Fish, 1996). Pelagic phase Species of the amphipod genus Bathyporeia leave the protection of the sand at night to swim. Such activity is also a feature of certain species of benthic amphipods, particularly of those belonging to the families Haustoriidae, Phoxocephalidae, Oedicerotidae, Calliopiidae, Atylidae and Dexaminidae (Fage, 1933). The swimming activity of Bathyporeia pelagica shows both a circatidal and circasemilunar periodicity (Watkin, 1939a; Fincham, 1970a & 1970b; Preece, 1971). Bathyporeia pelagica emerges on the early ebb of high tides, and is two or three times more active on night-time tides than during the day. It is likely that endogenous rhythm of Bathyporeia pelagica is modulated by temperature, the natural Light/Day cycle (nL/D) and tides acting as exogenous synchronizing factors. This endogenous rhythm will also 'free-run' in animals kept under constant environmental conditions (Fincham, 1970b). However, it is not yet known which exogenous stimulus is most important in re-phasing the activity cycle to keep in tune with seasonally changing tides and nL/D ratios (Hayward, 1994). It is difficult to state exactly why Bathyporeia pelagica has this activity rhythm. Feeding is an unlikely cause since this is conducted whilst buried in the sand. It seems more likely that swimming is connected with the reproductive cycle. Whilst the species swims most nights, a maxima occurs 4-9 days after a new moon when there is less rapid water movement over the beach than at spring tides. As a result mating couplings may be more successful (see reproduction).
Biology References	Fish & Fish, 1996, Hayward, 1994, Fage, 1933, Fincham, 1970a, Fincham, 1970b, Preece, 1971, Watkin, 1939(a), Watkin, 1939(b), Hayward & Ryland, 1995b, Julie Bremner, unpub data
Distribution and Habitat
Distribution in Britain & Ireland	Found on sandy coasts of Britain and Ireland.
Global distribution	This species has been recorded from the Netherlands and the Channel coast of France.
Biogeographic range	Not researched	Depth range
Migratory	Diel
Distribution Additional Information	Salinity tolerance Bathyporeia pelagica is an intertidal species restricted to the lower half of the tidal range by its intolerance to changes in salinity. In experimental studies, Preece (1970) found that Bathyporeia pilosa had a wider salinity tolerance than Bathyporeia pelagica. In both species, gravid females and juvenile males tolerated hyposaline conditions (3.6psu & 10.8psu) better than mature males, and that an increase in temperature (5°C to 15 °C) lowered the tolerance to hyposaline conditions. The differences in salinity tolerance between the species are considered to be important in determining their vertical distribution on the shore. Field studies (Watkin, 1942; Fish & Preece, 1970) have shown that Bathyporeia pilosa extends into areas where salinity fluctuations are pronounced, whilst Bathyporeia pelagica occurs in areas of higher and more stable salinity. Changes in distribution Vertical migration into the tidal waters occurs on most nights of the year. However, the species retain their zonation closely when swimming in the tidal waters, which suggests that the time they remain in the water is short or that several cyclical migrations are made (Watkin, 1939a). Seasonal changes in vertical distribution and abundance are considered to be influenced by salinity-temperature fluctuations acting in association with maturation. For instance, Fish & Preece (1970) observed the disappearance of Bathyporeia pelagica from their sampling site at Ynyslas, west Wales in March 1967 and specimens were not recorded again until October. In subsequent years the disappearance of Bathyporeia pelagica was sudden and characterized by the movement of a large proportion of the population to the lowest levels of the shore.
Substratum preferences	Water column (pelagic), Fine clean sand	Physiographic preferences	Strait / sound, Estuary, Enclosed coast / Embayment
Biological zone	Upper Eulittoral, Mid Eulittoral, Lower Eulittoral	Wave exposure	Moderately Exposed, Sheltered
Tidal stream strength/Water flow	Insufficient information, See additional information, Insufficient information	Salinity	Full (30-40 psu)
Habitat Additional Information
AMBI Group (Borja et al., 2000)	I
Distribution References	Hayward & Ryland, 1995b, Hayward et al., 1996, Howson & Picton, 1997, Lincoln, 1979, Watkin, 1939(b), Fish & Preece, 1970, Watkin, 1942, Preece, 1970, Fish & Fish, 1978, Ladle, 1975, Hayward & Ryland, 1995b, Julie Bremner, unpub data
Reproduction/Life History
Reproductive type	Gonochoristic	Developmental mechanism	Ovoviviparous, Brooding
Reproductive Season	Spring and autumn	Reproductive Location	As adult
Reproductive frequency	Annual episodic	Regeneration potential	No
Life span	1 year	Age at reproductive maturity
Generation time	<1 year	Fecundity	15
Egg/propagule size		Fertilization type	Internal
Larvae/Juveniles Larval/Juvenile dispersal potential 10-100m Larval settlement period Insufficient information Duration of larval stage
Additional Information	Annual reproductive cycle Fish & Preece (1970) described the reproductive cycle of Bathyporeia spp. The sexes are separate and pair whilst swimming, but there is no prolonged precopula behaviour. Mature females of Bathyporeia pelagica may produce a sequence of broods. Whilst one set of embryos develop in the brood pouch, oogonia enlarge in the ovary. Development of an egg to the stage when it is released as a juveniles takes about 15 days, and this cycle is thought to be related to the phases of the moon (Watkin, 1939b; Fish, 1975). Females produce up to 15 eggs (J. Fish, pers. comm.). Two reproductive peaks occur in spring and autumn suggesting that the over-wintering population matures slowly and reproduces in the spring, and their progeny mature rapidly over 5 months to reproduce in the autumn of the same year. Fish & Preece (1970) found that between November and February the population of Bathyporeia pelagica on a sandy beach at Ynyslas, west Wales, consisted entirely of non-reproducing juveniles. Salvat (1967) recorded a similar generation delay for some populations of species on the west coast of France, but in other regions reported reproduction throughout the year. It is likely that temperature may be an important factor. During the breeding season, gravid females are readily identified by the presence of blue eggs in the brood chamber (Fish & Fish, 1996). The ratio of the sexes in Bathyporeia pelagica varies throughout the year unlike Bathyporeia pilosa where there is a continuous dominance of females in the population (Fish & Preece, 1970).
Reproduction References	Fish & Fish, 1996, Watkin, 1939(b), Salvat, 1967, Fish & Preece, 1970, Fish, 1975, Julie Bremner, unpub data