Overview of the anatomy of Arion vulgaris

Arion vulgaris is an important pest in agriculture and it is quite a big slug. It can reach up to 12 cm. It is widely distributed through the Europe. I think, it could be more widely used as a model organism at least in education about basal anatomy of slugs. Despite that, I found no many photos of its anatomy. It is probably because of this species is not usually necessary to be dissected for identification. When some anatomy photos are available, then they are depicting only a part of the reproductive system dissected from the body of the slug and/or they are black-and-white only.

 

I have briefly dissected the slug: I have removed the body wall (with ovotestis (=glandula hemaphroditica) and with a part of hepatopancreas also accidentally removed) and I have kept the head undissected in detail. This specimen comes from Olomouc, the Czech Republic and I have collected and dissected it on the 11th August 2011.

Arion_vulgaris_anatomy

There are visible the following structures of the reproductive system:

 

atrium. Atrium is short in comparison of Arion rufus.

 

epiphallus

 

bursa copulatrix

 

oviductus. There should be a ligula within the oviductus that is an identification character of this species, but the ligula is not visible on the photo here, because I did not cut the wall of oviductus.

 

spermoviductus

 

glandula albuminalis

 

ductus hermaphroditicus (white thin meandering like tube)

 

glandula hemaphroditica and hepatopancreas. Part of hepatopancreas and probably the whole glandula hemaphroditica is accidentally removed from this dissected slug.

 

There is also visible tube like digestive system and glandulae mucosae:

 

oesophagus comes from the frontal part and is contected to the hepatopancreas

 

intestine comes from hepatancreas back to frontal part and it ends with anus, that is not visible here.

References and further reading:

 

(in Czech) Horsák M., Juřičková L., Beran L., Čejka T. & Dvořák L. 2010: Komentovaný seznam měkkýšů zjištěných ve volné přírodě České a Slovenské republiky. [Annotated list of mollusc species recorded outdoors in the Czech and Slovak Republics]. – Malacologica Bohemoslovaca, Suppl. 1: 1–37.

 

(in Russian) ГУРАЛЬ-СВЕРЛОВА Н. В. & ГУРАЛЬ Р. И. [Gural-Sverlova N. V. & Gural R. I.] 2011: Морфологические, анатомические и поведенческие особенности слизней из комплекса Arion lusitanicus (Arionidae) на западе Украины. [Morphological, anatomical and behavioural peculiarities of the slugs from the Arion lusitanicus complex in Western Ukraine]. – Ruthenica. 21(2): 97-111.

 

(in Polish) Riedel A. & Wiktor A. 1974: Arionacea. Ślimaki krążałkowate i ślinikowate: Gastropoda, Stylommatophora. Fauna Polski 2, Warszawa. 141 pp.

Underground life of Boettgerilla pallens

Boettgerilla_pallens_juvenile

Boettgerilla pallens in the terrarium

Sometime in August 2011 – I have added soil from the garden into the terrarium. It is the plastic transparent box, vertically placed it has inner dimesions like this: 17 cm high, 8.3 cm length. The inner dimension (the width) is 28 mm. The box have the same dimensions as a box that you have allready seen in my previous post. I have placed one earthworm to the terrarium.

The same box but larger could be useful to watching earthwors. A Czech book for teenargers recommends box for earthworms like this: 30×30×2.5 cm. So my terrarium for slugs is probably too thick to easy wath the undergound life.

 

It was placed in absolute dark in cupboard those times without slug. The earthworm has been making earthworm burrows and it has been producing earthwom faeces.

Terrarium

16th September 2011 – I have collected one adult Boettgerilla pallens in the garden.

17th September 2011 – I have placed the slug into the prepared terrarium. I have added the second earthworm into the terrarium, because I have thought, that the one have not survived.

 

It is thought, that Boettgerilla pallens is afraid of direct light, so the three sides of the terrarium are placed in the mild shadow all the time. Maybe I should keep it in more darker place.

 

The slug has immeditelly moved into the center of the terrarium. It has been moving inside the soil at the same speed as it is moving over the surface of the soil.

Boettgerilla_pallens_adult

I think, that it is resting in the upper part of small “caves”, when there are small caves available. At least I have seen resting my slug in such place few times.

 

Sometime I have found out, that there are in fact two earthworms in the terrarium. There are also two about 6 mm long millipedes (Diplopoda).

 

I have been adding food sources to the terrarium very rarely (about four times for the last 2.5 months). Food sources were fresh or rotting leaves of probably Common Dandelion Taraxacum officinale (rotting leaves were from other of my terraria inhabited with other gastropod species). When I have been adding food, I have been also adding some water. The terrarium is not water-resistant and when there is too much water, it will appear under the terrarium.

 

AnimalBase is claiming that the slug is feeding also on aerthworm faeces. If so, then Boettgerilla had always enough food.

 

I usually see no slug even if I will carefully check all transparent sides.

 

25th October 2011 – I have found out that there are at least two juvenile Boettgerilla pallens. The juvelines are white, while adults are grey.

Boettgerilla_pallens_adult_and_juvenile

Gunn (1992) studied the life cycle of this species. He have described eggs as transparent when laid and later white. There was not mentioned the size of eggs. Unfortunatelly I have seen no eggs. Juveniles hatch after 20-22 days at 17 °C. The temperature conditions in my room is 21 °C, because I live there. Adults survive egg-laying and die shortly after, but the can survive “for over a month”. I think, that my slug have laid the eggs. It is possible, that eggs or even such small juveniles were in the soil since August. Egg laying was recorded since August to October in Wales.

 

27th October 2011 – The adult Boettgerilla pallens is still alive.

 

2 November 2011 – I have taken photos of one juvenile. It was about 4 mm long.

The foot of juvenile slug:

Boettgerilla_pallens_juvenile_footBoettgerilla_pallens_juvenile_foot_2

3rd November 2011 – The adult Boettgerilla pallens is still alive.

References:

 

(in Czech) Dobroruková J. & Dobroruka L. J. (1989). Malá tajemství přírody. Albatros, 177 pp., page 82.

 

Gunn A. (1992). “The ecology of the introduced slug Boettgerilla pallens (Simroth) in North Wales”. Journal of Molluscan Studies 58(4): 449-453. doi:10.1093/mollus/58.4.449 (the first page extract)

 

“Species summary for Boettgerilla pallens. AnimalBase, last modified 28 December 2008, accessed 8 September 2010.