The Leopard Slug (Limax maximus) (literally, "great slug"), also known as the great grey slug this is one of the largest kinds of keeled air-breathing land slug in the world.
Limax maximus is the type species of the genus Limax. The adult slug measures 10-20 cm (4-8 in) in length and is generally a light greyish or grey-brown with darker spots and blotches, although the coloration and exact patterning of the body of this slug species is quite variable.
This species has a very unusual and distinctive mating method, where the pair of slugs use a thick thread of mucus to hang suspended in the air from a tree branch or other structure.
Although native to Europe, this species has been accidentally introduced to many other parts of the world.
The body length of adults of this slug species is 10-20 cm (4-8 in).
The greater part of the body is rounded, but there is a short keel on its tail, with about 48 longitudinal rows of elongate, detached tubercles.
The animal's body color is pale-grey, ash-colored, brownish or sometimes yellowish-white. The body is longitudinally streaked or spotted with black. The shield is always black-spotted. The sole of the foot is ash or yellowish-ash colored, and the color is always uniform. The foot-fringe is pale, with a row of minute submarginal blackish tubercles.
Every Limax maximus differs slightly in its pattern of black spots
The tentacles are very long and slender. The reproductive pore is near the base of the right upper tentacle.
The shield is oblong, about one-third of the total length of the animal. The shield is rounded in front, angular behind, and forming an angle of about 80 degrees when in motion, usually of a similar tint to the body, but boldly marbled or maculate with black, somewhat concentrically and interruptedly ridged around a sub-posterior nucleus.
The pneumostome is just posterior to the mid-point of the mantle, as it is in all Limacidae.
The mucus is colorless and iridescent, and not very adhesive.
Although color varieties have no actual taxonomic significance, a large number of color varieties have been described, prominent among them being the varieties serpentinus, vulgaris, cellarius (typical), johnstoni, maculatus, ferrussaci, obscurus, fasciatus and rufescens, of Alfred Moquin-Tandon, and cornaliee, of Pini.
As well as different tints and markings, various shades of color exist in Limax maximus:
The shell of Limax maximus is reduced and internal, under the shield. The occurrence of this internal shell was known to Pliny the Elder; the shell was used by the ancient physicians for the sake of its carbonate of lime.
The calcitic shell is situated beneath the hinder part of the shield, and is perceptible through the skin. The color of the shell is whitish. The shape of the shell is oblong-oval and thin, slightly convex above, and correspondingly concave beneath, with a membranous margin. The apex or nucleus is at the posterior margin but inclined towards the left side, and forming the apophysis by which the shell is organically attached to the animal. The length of the shell is 13 mm (1/2 inch) and the width of the shell is 7 mm (1/4 inch). Shells of different Limacidae species are undiagnostic: in other words, they are not helpful for identification purpose.
Digestive system: The formula of the radula is: 62-73/ × 138-157. The intestine has six convolutions and is without a caecum. Of the six convolutions of the intestine, four are imbedded in the liver, and two hang freely in the body cavity.
The nervous system is composed of the typical ganglia. The pedal ganglia are placed beneath the radula sac and joined together by an anterior and a posterior commissure. The abdominal ganglion lies a little to the right of the median line. The visceral ganglia occupy the angle between the lingual sheath and the oesophagus and the buccal ganglia are widely separated but joined together by a commissure nearly as thick as the ganglia themselves.
Reproductive system: The hermaphrodite gland (HG) is elongated and large, and is connected with spermoviduct (SD) by means of the hermaphrodite duct (HD) which takes its course through a portion of the albumen gland (AG). The spermoviduct is thick and well convoluted, and separates further down into a vas deferens or sperm-duct (VD) and an oviduct (OV). The former opens into the upper end of a very long penis (P), to which a strong retractor muscle (PRM) is attached. The lower portion of the penis unites with that of the oviduct at the genital orifice, so that there is no vestibule. The receptaculum seminis (RS) opens into the lower end of the penis near the junction of the two ducts.
This species is widely distributed but it is generally considered to be native to Europe.
The indigenous distribution of Limax maximus is western and southern Europe and part of western Africa also, maybe originally Mediterranean.
Great Britain - Limax maximus was described from a scientific point from England in Animalium Angliae Tres Tractatus … Alter de Cochleis tum Terrestribus tum Fluviatilibus by Dr. Martin Lister among first three British slugs in 1678. However the existence of Limax maximus in England was indicated twelve years before in Christopher Merret's Pinax Rerum Naturalium Britannicarum in 1667.
Limax maximus is a nocturnal animal which feeds at night.
It is inactive in its habits, not very prolific, and exudes a thick and glutinous slime which is iridescent when dried. When alarmed, or at rest, this slug merely draws its head within the shield, but does not otherwise contract its body. When irritated, it is said to expand its shield.
The homing faculty is strongly developed in this species, which, after its nocturnal rambles or foraging expeditions, usually returns to the particular crevice or chink in which it has established itself.
Limax maximus is capable of associative learning, specifically classical conditioning, because it is capable of aversion learning and other types of learning. They can also detect that there are deficiencies in a nutritionally incomplete diet, if the essential amino acid methionine is experimentally removed from their food.
The slugs are almost always found near human habitation — usually in lawns, gardens, cellars or in other damp areas.
This species is not gregarious. It frequents gardens, damp and shady hedgerows and woods, hiding during the day beneath stones, under fallen trees, or other obscure and damp places. It does however exhibit a decided preference for the vicinity of human habitations, and readily takes up its abode in damp cellars or outbuildings.
In Ireland, this predilection for human dwellings is not exhibited, and the species is restricted to woods and other similar places. It may even be met with almost within high-water mark on the seashore.
Limax maximus is omnivorous. It is of benefit as a detrivore for it cleans up dead plants and fungi, and as a carnivore for it hunts down other slugs with its top speed of 6 in/min. However it is also eats young crops faster than they can grow and so is listed as a major agricultural pest by State Departments of Agriculture from Florida to Oregon.
The eggs of this slug are deposited in a cluster, slightly attached to each other. Eggs are transparent, elastic and slightly yellowish in color. The size of the egg is 6×4.5 mm. They hatch in about a month.
The tiny slugs which emerge from the eggs need at least two years to reach sexual maturity.
The lifespan of Limax maximus is 2.5–3 years.
The mating habits of Limax maximus are considered unusual among slugs: the hermaphrodite slugs court, usually for hours, by circling and licking each other. After this, the slugs will climb into a tree or other high area and then, entwined together, lower themselves on a thick string of mucus, evert their white translucent mating organs (penises) from their gonopores (openings on the right side of the head), entwine these organs, and exchange sperm. Both participants will later lay hundreds of eggs.
A commonly seen practice among many slugs is apophallation, when one or both of the slugs chews off the other's penis. The penis of these species is curled like a corkscrew and often becomes entangled in their mate's genitalia in the process of exchanging sperm. When all else fails, apophallation allows the slugs to separate themselves. Once its penis has been removed, a slug is still able to participate in mating subsequently, but only using the female parts of its reproductive system.