Tergipes tergipes

Tergipes tergipes. Length 2.5mm. Digestive gland orange-brown in some cerata, others empty. Colour reflects that of hydroid consumed. White ovotestis in translucent body. Flanks, rear of head and rhinophores tinted brown. Sept. 2010. LWS, Mersey Estuary.

Species

Tergipes tergipes

Photographer / copyright holder

I.F. Smith

Tergipes tergipes. Brown digestive gland ziz-zagging left and right to connect single cerata resembles zig-zag stem of Obelia geniculata (hydroid) on which it often feeds. March 2011. LWS, Menai Strait, Wales.

Species

Tergipes tergipes

Photographer / copyright holder

I.F. Smith

Tergipes tergipes. Length 2.5mm. Dark brown digestive gland and light brown contents of cerata resemble hydroid. Two spawn capsules, greatly swollen by water after laying, resemble reproductive bodies of hydroid. Sept. 2010. LWS, Mersey Estuary.

Species

Tergipes tergipes

Photographer / copyright holder

I.F. Smith

Tergipes tergipes. Foot (edge wrinkled in image) narrower than body. No propodial expansion. March 2011. LWS, Menai Strait, Wales.

Species

Tergipes tergipes

Photographer / copyright holder

I.F. Smith

Distribution and status

Atlantic coasts from Iceland and Norway to eastern U.S.A. and Spain, and around Mediterranean. Also recorded in S. Africa and Brazil (GBIF map).
Common all round Britain and Ireland, but overlooked as small size requires inspection of hydroids under magnification. Densities of 500 /m² recorded.

Ecology and behaviour

Lower shore and sublittorally to 20m. On hydroids growing on stones, Laminaria fronds, piers, floating structures and ships; even isolated small stones in pools in mud. Zig-zag digestive gland resembles stalk of Obelia geniculata (EML) which is frequently found, with T. tergipes on it, on fronds of Laminaria hyperborea growing in moderate wave exposure. Also on many other hydroids, such as Laomedia flexuosa (WoRMS) on sheltered shores and in estuaries down to 10 ppt salinity. Simultaneous hermaphrodite. Spherical or kidney-shape transparent spawn capsules [5], each containing about 30 white ova, produced throughout the year. Spawn capsules easier to detect, and about ten times more numerous, than adults. Short veliger stage of about a week before metamorphosis. Matures in 5 weeks, ovotestis developed in 2.5mm long specimens, so many generations p.a..

Similar species

Eubranchus exiguus (Alder & Hancock, 1848)

Often occurs in company with T. tergipes, but usually less numerous.
Similar size to T. tergipes; frequently 4 - 6mm long.
Sparse urn shape cerata able to expand balloon-like, surface not knobbly [Ee5].
Olive or brown blotches on body, no zig-zag digestive gland [Ee7].

Key identification features

Smooth slender cerata arranged singly [2].
Brown digestive gland zig-zags between cerata [7].
Small, usually 5mm or less long, rarely 8mm.

References and links

Alder, J. & Hancock, A. 1845-1855. A monograph of the British nudibranchiate mollusca. London, Ray Society.
Thompson, T.E. & Brown, G.H. 1984. Biology of opisthobranch molluscs 2. London, Ray Society.

Current taxonomy;
World Register of Marine Species (WoRMS)
Irish distribution maps and prey organisms
Picton, B.E. & Morrow, C.C., 2010. Encyclopedia of Marine Life of Britain and Ireland (EML).

Taxon version key

[NBNSYS0000178319]

Sort order

6029

Taxonomic group

Marine slug