No common name

Sagitta planctonis

ORDER

Aphragmophora

FAMILY

Sagittidae

TAXONOMY

Sagitta planctonis Steinhaus, 1896, south Equatorial Current, Atlantic Ocean.

OTHER COMMON NAMES

None known.

PHYSICAL CHARACTERISTICS

Individuals have 8-11 hooks, 6-9 anterior teeth, and 10-14 posterior teeth. Maximum adult body length is 1.46 in (37 mm), and relative tail length is 19-21% of total body size. The body is large, firm, and opaque. There are two pairs of lateral fins and a fin bridge. Anterior fins are long, angular, partially rayed, and reach the middle of the ventral ganglion. Posterior fins are long, angular, and partially rayed. There is a large col

larette and gut diverticula. Eyes are small with T-shaped pigment spots. Seminal vesicles are conical and touch posterior fins. Ovaries are very broad and long, reaching the neck region; ova are fairly small

DISTRIBUTION

Shallow-mesopelagic and cosmopolitan, occurring between 40°N and 40°S.

HABITAT

Occurs in the pelagic realm of tropical and subtropical regions of the ocean, at depths of 328-1,640 ft (100-500 m).

BEHAVIOR

Shows evidence of diurnal vertical distribution. Juveniles occur at higher levels in the water column than the adults. Rapid darting movements are made over short distances to catch prey.

FEEDING ECOLOGY AND DIET

Prefers small copepods. Feeds at night after moving to superficial layers.

REPRODUCTIVE BIOLOGY

Reproduces once or twice a year, depending on water temperature. Hermaphroditic, and sperm is stored in the oviducts waiting for the eggs to mature. Fertilized eggs are released in sea water. There is no larval stage.

CONSERVATION STATUS Not listed by the IUCN.

SIGNIFICANCE TO HUMANS None known. ♦

evidence has revealed substantial genetic differences between populations from the North and Mediterranean seas.

DISTRIBUTION

Neritic, occurring in the North, Mediterranean, and Black seas.

HABITAT

Lives in shallow pelagic waters of the Mediterranean, Black, and North seas, especially where the continental shelf is relatively wide. Reported to tolerate different degrees of salinity and may inhabit inshore waters and estuaries. Occurs in the western part of the Baltic Sea as long as the salinity is not too low.

BEHAVIOR

Nothing is known.

FEEDING ECOLOGY AND DIET

Prefers small copepods. Feeds at night after moving to superficial layers.

REPRODUCTIVE BIOLOGY

Reproduces once a year, during the summer months with a peak in late August. Hermaphroditic, and sperm is stored in the oviducts waiting for the eggs to mature. Fertilized eggs are released in the sea water. There is no larval stage.

CONSERVATION STATUS

Not listed by the IUCN.

SIGNIFICANCE TO HUMANS

Used as an indicator species to follow the movement of water masses. ♦

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