Overview

Brief Summary

Biology

This species feeds on sea squirts by biting lumps from the zooids (3). Breeding occurs in late spring and summer. The sexes are separate and fertilisation takes place internally following copulation. Females lay their eggs into sea squirts by biting holes in the colonies and then laying their flask-shaped egg capsules (each containing around 800 eggs) into the hole. After a few weeks the larvae hatch. They are free-swimming and pelagic for around a month (2) and are usually found in coastal waters during the summer (3). In some parts of the world, large cowrie shells were once used as currency, but this did not occur in Britain. The word cowrie originates from the Hindu and Urdu languages, as cowries are very common in the Indian Ocean (4).
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Description

The European or spotted cowrie is a marine mollusc that has an egg-shaped glossy shell featuring many transverse ridges with a long, narrow aperture on the underside (2). The upper surface of the shell is usually a reddish brown colour, and has three characteristic spots that allow the species to be identified easily (3). The head, tentacles, foot and body of this mollusc are brightly coloured; they may be red, yellow, green, brown or orange (3).
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Comprehensive Description

Description

 This species has a thickly calcified, glossy shell, with closely spaced transverse ridges. The shell is up to 12 mm long by 8mm wide. The upper surface is reddish-brown in colour with 3 diagnostic spots.The underside of the shell is flattened and white. The head, tentacles, foot and mantle are brightly coloured, from yellow, red, orange and brown, the foot often being paler. When the animal is active the mantle almost completely obscures the shell, and the mantle edge draws out anteriorly into a long siphon. The shell aperture is narrow, running the whole length of the shell, turned left at the ends with both sides ridged.Trivia monacha can be confused with Trivia arctica, the former being larger and having 3 distinctive brown spots on its shell. There is no operculum present, and the females have an additional ventral pedal gland. This species feeds on the ascidians Botryllus schlosseri, Botrylloides leachi, and Diplosoma listerianum.   Breeding occurs in late spring and summer. The female deposits flask-shaped egg capsules (each containing 800 eggs), in holes that have been eaten out of the ascidian. After a few weeks the larva emerge and are free swimmming for a few months. Juveniles (5 mm long) have a short spire, wide aperture and lack the characteristic ridging of mature adults.
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Distribution

Range

This cowrie is found around most British coasts (2). It is found as far south as the Mediterranean, and reaches the extreme north of its range in western France and Britain (3).
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Ecology

Habitat

 Trivia monacha is found on the lower shore and sublittorally on rocky coasts associated with its prey, colonial sea squirts.
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Depth range based on 58 specimens in 1 taxon.
Water temperature and chemistry ranges based on 7 samples.

Environmental ranges
  Depth range (m): 0 - 219.75
  Temperature range (°C): 9.022 - 11.855
  Nitrate (umol/L): 4.573 - 6.151
  Salinity (PPS): 35.008 - 35.218
  Oxygen (ml/l): 6.128 - 6.328
  Phosphate (umol/l): 0.333 - 0.525
  Silicate (umol/l): 2.315 - 3.419

Graphical representation

Depth range (m): 0 - 219.75

Temperature range (°C): 9.022 - 11.855

Nitrate (umol/L): 4.573 - 6.151

Salinity (PPS): 35.008 - 35.218

Oxygen (ml/l): 6.128 - 6.328

Phosphate (umol/l): 0.333 - 0.525

Silicate (umol/l): 2.315 - 3.419
 
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Found in association with its prey, colonial sea squirts (ascidians) including Botryllus schlosseri and Botylloides leachi (2) on the lower shore and in the sublittoral zone of rocky shores. It may also live in estuaries (3).
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Associations

Animal / rests in
egg capsule of Trivia monacha rests inside nibbled hole common test of Botrylloides leachi

Animal / rests in
egg capsule of Trivia monacha rests inside nibbled hole common test of Botryllus schlosseri

Animal / rests in
egg capsule of Trivia monacha rests inside nibbled hole common test of Diplosoma

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Conservation

Conservation Status

Status

Not threatened (2).
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Threats

This species is not currently threatened.
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Management

Conservation

Conservation action has not been targeted at this species.
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Wikipedia

Trivia monacha

Trivia monacha, also known as the European cowrie or spotted cowrie, is a species of small sea snail, a marine gastropod mollusc in the family Triviidae, the trivias.

The name Trivia means "common" and the word monacha means "solitary".

It is worth comparing this species with the similar species Trivia arctica, the northern cowrie.

Shell description[edit]

Lateral view of a shell of Trivia monacha
Five views of a shell of Trivia monacha
Seven Trivia nonacha shells, shown in close-up. A range of sizes is visible: the largest is about a centimeter across, the smallest about half a centimeter across. Five of the shells are face down, showing the ridged back of the shell, which is a pink-brown colour; the characteristic dark spots are visible.  One shell is on its side, and one is upside-down, showing the white underside and the slit where the animal sticks its tentacles out.  On the upside-down shell, four or five sand grains, about a millimeter across, are stuck on the aperture.
Adult Trivia monacha shells hand-picked from beachdrift, from near Aberffraw, Anglesey. Scale is in cm.

The shell of this species is glossy, convolute and lemon-shaped, with 20-30 transverse ridges. The dorsal part of the shell is a pinkish or reddish-brown with three characteristic darker spots in mature individuals, on spot anterior, the other posterior and one in the centre, all situated along a central line. Juvenile shells are all white or light-coloured. The apertural side is white and flattened. The aperture is narrow and runs along the whole length of the shell. At the ends it turns to the left in the direction of the swollen body whorl. The transverse ridges are strong and often bifurcate. The ones at the ends are almost U-shaped.

The shell length is up to a maximum of about 15 mm and its width about 8 mm.

The dark mantle is covered by few papillae, usually tipped with pale yellow. The mantle is drawn out into a long siphon anteriorly, extending over the whole (or almost the whole) shell. The foot is orange or bright yellow.

The breeding season is late spring or summer. The larvae have a very dark stomach and intestine. More developed larvae in the veliger stage have a two-lobed velum (a structure used for swimming and particulate food collection) that is slightly indented at sides. The larvae reach the adult form in about five to six months.

Distribution[edit]

This species occurs from the Mediterranean Sea to the Orkney islands north of Scotland, but is more common in the south.

In Orkney and some parts of Scotland, the species are known as 'groatie buckies'.

Habitat[edit]

This species usually lives on rocky shores or under stones below low tide, in other words is sublittoral, but the empty shells of this species are often washed up onto beaches. It is usually found together with compound ascidians (Botrylus, Botrylloides and Diplosoma). Trivia monacha lacks small denticles on the admedian teeth of the radula. Furthermore, the rows of teeth in the two species are different.

Feeding habits[edit]

This snail feeds on sea squirts and compound ascidians.

Similar species[edit]

Trivia monacha is sometimes confused with Trivia arctica. In fact they were considered to be two forms of the same species until 1925, when A. J. Peile published a paper in the Proceedings of the Malacological Society differentiating the two.[1] They can be differentiated by the radula, the shape of the penis and their larval stages. In Trivia monacha the penis is filiform and cylindrical, while in Trivia arctica the penis is large and flat.

It is now known that the larvae of the two species are readily distinguishable.

The Linnaean name Trivia europea, now lapsed, referred to the supposed single species. Linnaeus himself mentioned two kinds: Cypraea europea and Cypraea anglica, but these terms were intended as a geographical distinction and are not accepted as species names today.

References[edit]

  1. ^ Peile A. J. (1925). "The Differentiation as Species of the two forms of British Trivia". Proc. Malac. Soc. 1925, pp: 195-198.
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