(Quoy and Gaimard, 1827)
A pelagic snail with a completely transparent uncoiled, needle-like shell. The visceral mass is seen through the shell. The wings are undulated at the border. The balancer is clearly seen at the left mantle border.
Shell small, long, tubular and not curved, round in cross-section [S.subula-shell]. The surface has faint transverse striation; in between these striae are very minute longitudinal striations. The width of the aperture in adults is smaller than the shell diameter, just posterior to the aperture. A triangular tooth may be found dorsally and a triangular incision ventrally at the aperture border. The groove [S.subula-g ] at the dorsal side of the shell is variable and more or less twisted so the caudal point of the groove is at the left of the median line and the cranial point in the median [S.subula-a/g ]. The posterior shell parts, with the embryonic shell, are pointed and show two constrictions above each other.
Radula formula: 1-1-1 [S.subula-r].
Juveniles: the shell development is regular so that the juvenile represents the pointed oval protoconch I with cylindrical protoconch II gradually but slowly increasing in width and finally showing two incisions. The soft parts develop slower than the shell so that after the veliger stage a skinny stage occurs. In this stage the too small soft parts are long drawn in a adult shell.
Shell completely transparent. The rose or red visceral mass is seen through the shell. The wings are rose-coloured.
Length of the shell up to 13 mm. The rear angle of the shell is 11°.
Styliola subula is a good swimmer that feeds on epipelagic phytoplankton and protozoa. Living in the upper layers, where it can occur in mass blooms. The temperature range and salinity range are about 13.8°-27.8°C and 36.8ä and 36.5ä, respectively.
Epipelagic. Styliola subula displays a clear diurnal vertical migration. The juveniles migrate up and down over 300 m while the adults migrate over 400 m. The maximum depth at which the species was recorded is 1500 m, but it is found most frequently between 50-100 m.
Distribution in the North Sea
Possibly in the northern North Sea, entering from the NE Atlantic.
All oceans between 40°N-40°S. In the Atlantic sometimes as far north as 60°N, transported by the Gulf Stream; NW off the British Isles, from where it might enter the northern North Sea.
[After Van der Spoel et al., 1997]