Melanopsis praemorsa (LINNAEUS 1758)

Over 200 species of the genus Melanopsis were scientifically described for the Mediterranean region alone. Several of these "species" were described by considering non-significant variabilities of different shell characteristics, others just on the basis of a geographic isolation from the next or next-to-the-last populations existing at the time of description. After intensive research by GLAUBRECHT (1996) several localizations with intermediary characteristics could be identified, and thus the editor follows his arguments that there is a superspecies highly variable in shape with the type species Melanopsis praemorsa (LINAEUS 1758) present in the entire area. Biomolecular and further interdisciplinary research is currently being carried out in order to clear up the nomenclature further. 

In transition, the most important of the recent species currently accepted are portrayed separately in the first two paragraphs of this page.

Description:

This snail species' dextral shells, highly variable in form, show pronouncedly globose whorls and a wide concial shape. Forms with flatter whorls have an overall ovoid shape. In nature, the shells grow to 20 to 25 mm (max. 30) long and about 10 mm wide. There are forms with lateral ridges, quite often with stepped whorls. In general, their whorls are flat or less globose. The most striking  characteristic of all those forms listed below is a siphostome part at the lowest end of the aperture. The aperture and the operculum are pointed on the upside. The empty shell shows an only slightly thicker outer lip. The inner lip (on the body whorl) shows a white uneven flare especially in the upper part.

The corneous operculum is elliptic and has a terminal nucleus. The discoidal foot onset on the operculum's inner side is especially enlarged in the lower part.

The shell color varies between light brown (Toscana, the Aegean) and black (Andalusia, Jordan). Spiralling bands (as can be seen with M. costata on this page) can be found in several forms, however, this is also highly variable within the respective populations. The operculum is reddish-brown. The snail's foot is very short and broadens squaring at the front. The wrinkled mouth part is clearly set off from the foot, the active animal stretches it out in a trunk-like manner. On the outside of the bases of the long broach-shaped tentacles the eyes are located. The animal's color is a pale grey to black with light speckles.

Adult females can be sexed by the help of a little pigmented whiteish dot that can also be slightly swollen. This reproductive opening is located on the right side of the foot at the front, over the foot seam.

When reading the following portraits please keep in mind that there are interjacent forms with intermediate characteristics in areas where the species ranges overlap. There do not seem to be true species barriers within the highly polymorph superspecies!

Melanopsis praemorsa(LINNAEUS 1758): Smooth-walled form with blackish shell and a body intensively black in color.

Melanopsis cariosa(LINNAEUS 1767) = M. costellata (FÉRUSSAC 1823): Ridged form with very short whorls (Andalusia). Individual shells with knobby rigdes on the spine. (In Andalusia) pale grey to flesh-colored body.

Melanopsis dufouri(FÉRUSSAC 1823): According to the shell phenotype an intermediate form between M. praemorsa and M. cariosa.

Melanopsis tricarinata(BRUGUIÈRE 1789): Form with three prominent spiralling ridges.

Melanopsis penchinati(BOURGUIGNAT 1868): Small form with lateral ridges.

Melanopsis lorcana: (GUIRAO 1854): ?.

Melanopsis etrusca(VILLA 1862): Smooth-walled form with light brown shell.

Melanopsis parreyssii(PHILIPPI 1847): Form frequently with knobby lateral ridges on the spine. Shell length up to 18 mm and 8.5 mm wide with up to 7 stepped whorls. The shell is of a pale horn color, often with a brownish band above the suture. 

Melanopsis buccinoidea(OLIVIER 1801): Smooth-walled form with up to 6 flat whorls. The animals shown here originate from Rhodos/Greece and are characterized by a fine orange-colored suture between the dark brown whorls and a black body. Shell from Basra/Iraq, up to 17 mm long and 8 mm wide.

Melanopsis costata(OLIVIER 1804): Ridged form with pronouncedly globose whorls. The animals shown here originate from the south-west of Turkey. In this habitat snails with shells of up to 19 mm in length and 9 mm width were found. The largest part of them was single-colored, either dark brown or of a blackish blue-grey. Individual snails had light grey spiralling bands with smooth transitions to the basic color. The snails' bodies are black with lighter speckles.

Melanopsis nodosa(FÉRUSSAC 1823): Ridged form with up to 7 stepped whorls. The ridges are frequently knobby on the spire. Shells from Basra/Iraq up to 17 mm long and 8 mm wide.

Range/Habitat:

Melanopsis species are found around the Mediterranean Sea and, towards the East, as far as Iran:

Melanopsis praemorsa: Spain (Andalusia (southern slope of the Sierra Morena and the Betic Cordilleras) to Valencia), Morocco, Algeria, Tunisia.    Habitat 4

Melanopsis cariosa: Spain (south-west of the Guadalquivir basin/Andalusia), Morocco, Algeria.

Melanopsis dufouri and Melanopsis tricarinata: South-eastern Spain (Valencia).

Melanopsis penchinati: Nothern Spain (upper catchment area of the Rio Jalón: thermal spring in Alhama de Aragón, Monasterio de Piedra).

Melanopsis lorcana: Spain.

Melanopsis etrusca: Western Italy (Toscana, Latium), Spain (Ibiza and Formentera).

Melanopsis parreyssii: Romania (Püspökfürdö), Hungary (released to the wild: Magaret Island/Budapest).

Melanopsis buccinoidea: Greece (Aegaean catchment area and islands); Cyprus; Turkey (Anatolia, spring region of the Euphrat); in the Lebanon, Syria, Jordan and Israel (furtherly in catchment areas of the Meditaerranean Sea, but also east of the Jordan River in oases and wadis); Egypt (only Sinai); Iraq (Euphrat, Tigris); Iran.

Melanopsis costata: Syria (Lake Homs, upper reaches of the Orontes, Bir Jaloud Oasis), Lebanon (lower reaches of the Litani), Israel and Jordan (catchment area of the Jordan River, Lake Tiberias), Southern Turkey.

Melanopsis nodosa: Jordan, Iraq (Euphrat), Iran.

Melanopsis species can be found in the Mediterranean region in a wide range of limnic water bodies: cold and warm springs, brooks, rivers, canals and trenches, lakes and ponds. In Europe they do not populate brackish estuaries. As a rule, they do not dwell on soft substrates but on stony or rocky ground.

This snail was especially found on water plants in water bodies in the boglands of Iraq. In the estuaries on muddy soils as well as on stony substrate.

In Morocco, they can also be found in subterranean feeder canals with low current and muddy-sandy substrate in abundant numbers.

Water parameters:

According to oberservations by GLAUBRECHT (1996) this snail prefers waters rich in oxygen and calcium. The author has not been able to find previously known Spanish populations in eutrophic water bodies or water bodies whose balance was severely disturbed.

In the Mediterranean region this species can exclusively be found in fresh water. Isolated forms have been known from inland Iran in the area around Chiraz that tolerate a salinity of up to 4.5 g/l.

According to IDAGHDOUR (1991 in: MOUAHID et al. 1996) Melanopsis tolerates various current velocities in nature (0.12 to 0.44 m/s), temperatures between 13.3 and 25.6 °C, salinities of up to 35‰ as well as pH values between 7 and 8.3.

As an example of a natural habitat of Melanopsis costata in south-western Turkey some water parameters have been posted on German Aquarienschnecken-Forum (see Weblinks). Very detailed physical and chemical water parameters for Lake Tiberias (Lake Kinneret), in which Melanopsis costata is also known to live, including the seasonal development of water temperatures, can be found in the "World Lakes Database" on the Internet (see Weblinks).

Reproduction:

As many other front-gilled snails, Melanopsis is dioecious.

When researching a Moroccan population, MOUAHID (1996) constated a stable relation between male and female snails of 2:1 in the course of the year.

Animals kept in aquariums with stony substrate preferred to lay their egg clutches on (overhanging) undersides of stones. No clutches were found on the aquarium panes or on the underside of floating Styropor® chunks. The brownish gelatinous clutches, with one pointed end, are an average 3.0 mm (1.8 to 5.5 mm) long and 1.0 mm (0.5 to 1.4 mm) wide. Depending on their size the respective number of eggs varies from 2 to 32 (average of 17) as well as the size of the individual eggs of 228 to 457µm. The same eggs were found by MOUAHID outdoors year-round, scattered in soft substrate. His conclusion was that, depending on the substrate, the snails lay individual eggs in soft substrates, which are less easy to see there, as well as egg clutches on hard substrate.

GLAUBRECHT (1996) researched the embryonic whorls on shells of various Mediterranean origins with the electron microscope. On the basis of significant structural changes he could prove that the shells of the young snails have only a diameter of 0.3 mm when hatching and 1.25 whorls. In aquariums containing those snails gathered by him in Andalusia in May young snails showed up in September. He did not observe matings or egg clutches. As  BANDEL observed (in: GLAUBRECHT, 1996), young snails are always first found in waters of Jordan in spring (April-May).

Life span:

ELKARMI & ISMAIL (2006, see Weblinks) could constate a considerable size classification when closely examining shells originating from Azraq Oasis/Jordan. On the basis of the seasonal reproduction of Melanopsis there the authors were able to conclude a life span of 5 years.

Food:

Melanopsis has adapted, with the help of a very long radula equipped with "carnassial teeth", to scrape diatoms and other algae from hard substrates, according to GLAUBRECHT (1996). They also eat detritius and carrion, however. As the author mentioned above observed outdoors and in the aquarium those snails also eat large macrophytes and root tips of aquatic plants.

Users of the Aquarienschnecken board have only been able to verify those snails eating the following aquatic plants: Water wisteria (Hygrophila spec.), Nymphoides spec. and Java fern (Microsorium spec.). In the habitat (lake in south-western Turkey) no M. costata could be found in the large clumps of milfoil (Myriophyllum spec.), however, many of them were rasping the algae growth from stones only a few meters away. In the aquarium the following aquatic plants were not eaten: arrowhead (Sagittaria subulata), fanwort (Cabomba spec.), Anubia spec. and moss balls (Cladophora aegagropila).

In the aquarium they also take (fish) food rests and zucchini in addition to their diet.

MOUAHID (1996) fed his snails kept in the laboratory with algae, salad, apple and carrot slices.

Behavior:

According to observations of users of the Aquarienschnecken board Melanopsis snails are mostly seen on substrates covered with algae (stones, glass panes), which can be explained by their diet. They do not dig themselves into the ground and hardly ever crawl a small way above the water surface.

Socialization in the aquarium:

On one type locality of Melanopsis costata in Turkey also the freshwater shrimp Palaemonetes antennarius can be found, which, during a socialization experiment with the domestic ramshorn snail (Planorbarius corneus), spared not a single freshly hatched young ramshorn snail. Likewise, there were finds of the freshwater crab Potamon potamios in the snails' locations, which also likes to eat snails. At least this form of the Melanopsis snail is obviously well protected from those two potential predators by its thick-walled shell and the operculum.

There are not many records on socializing Melanopsis with other species in the aquarium. When kept together with other snails (like e.g. ramshorn snails, Malayan trumpet snails, spring bladder snails, freshwater nerites) or dwarf shrimp (like e.g. crystal red bees), no problems have been reported so far. Crayfish (e.g. Cherax "tiger") can significantly decimate the population, though.

Additional information:

The smooth-shelled snails shown as Melanopsis buccinoidea (OLIVIER 1801) on this site originate from the Greek island of Rhodos. Some of these specimens were brought into Germany in fall 2006 (see Weblinks: Aquarienschnecken-Forum).

The ridged and banded snails shown here as Melanopsis costata (OLIVIER 1804) originate from Mugla province in south-western Turkey. Few specimens of these were also brought into Germany in fall 2006. The editor would like to thank some of the staff of University Berlin again for the scientific determination in this place. 

The German name "Maurenschnecke“ (moor snail) was introduced by GLAUBRECHT (1996), who opinates that all of the species to be found around the Mediterranean Sea of the genus Melanopsis belong to the superspecies Melanopsis praemorsa (LINNAEUS 1758). He chose this name, on the one hand, because the Linnaean type material came from Andalusia/Spain, which had been occupied by the moors for over eight centuries, and on the other hand, as the spread of Islam at the end of the first millenium is practically the same as the range this snail can be found in.

Literature:

GLAUBRECHT, M. (1996): Evolutionsökologie und Systematik am Beispiel von Süß- und Brackwasserschnecken (Mollusca: Caenogastropoda: Cerithioidea): Ontogenese-Strategien, paläontologische Befunde und historische Zoogeographie. Backhuys Publishers, Leiden, NL. ISBN 90-73348-52-8.

[Morphology, anatomy, reproductive biology, range with map etc.]

GLÖER, P. (2002): Süßwassermollusken Nord und Mitteleuropas. Bestimmungsschlüssel, Lebensweise, Verbreitung. In: Die Tierwelt Deutschlands. Conchbooks, Hackenheim. ISBN 3-925919-60-0.

[Characteristics, range etc., only for Melanopsis parreyssii]

MOUAHID, A. et. al. (1996): Observation of spawn in Melanopsis praemorsa (Prosobranchia: Melanopsidae). Journal of Molluscan Studies. Vol. 62, (3): 398-402.

[Research about the reproduction of a Moroccan form outdoors and in the aquarium]

Weblinks

This page was actualized on August 26, 2008

Author: schneckli

Translator: Ulrike Bauer