[mdcorcoran]

hey all...
I noticed some type of snail critter crawling on my back glass today. It's definitely not a snail that I've purchased, and I haven't added any new LR in over a year, so I was really surprised to see him. His movement is different from that of any snail I've ever seen, as he almost completely lifts his body off the glass between steps. He has a very long reaching tentacle in front of him, and his leg stretches very far also. Any idea as to what he is, and whether he is helpful or harmful? I think I might trap him while I have him in sight, just in case.

 

[deathmatch782]

conch
the snout and the leg give it away

they are great algae and detrius eaters i have one in my 75

 

[ChrisPrusha]

I believe queen conchs are the ones that climb glass (as opposed to fighting conchs). He's gonna get big.

 

[deathmatch782]

my fighting conch climbs the glass
mostly stays on the sand and rocks though

 

[tdwyatt]

conch
the snout and the leg give it away

they are great algae and detrius eaters i have one in my 75

MOST of the conch or conch-like snails are algae and detritus eaters, however there are a few genera that are similar in appearance that are predatory carnivores...

True Conchs are members of the Family Strombidae, and are strictly herbivorous. Within this family are several genera, including the genera Strombus (the true Conchs), Lambis (the spider conchs), Tibia spp. (tibias), Varicospina (beak shells) and the Tterebellum spp.. Even though these all have different morphologies, there are certain internal structural traits that tie all these togehter as a taxonomic group. However, there are many similar genera of the carnivorous whelks, in particular to the genus Strombus that so closely resemble the herbivorous snails that they are frequently misidentified as such. Their shells are both tapered at each end with the front end elongated out into a calcareous spout or siphon. The only real means of differentiating these different snail groups is to study their fine morpohology and behavior. When the snail in question extends its snout/probiscus from its shell, look closely for the eyes, in particular for the presence or absence of eye stalks. In all of the animals in the herbiverous conch group, the eyes quite evident, with long stalks, visible eyeballs, and observable pupils. In the predatory whelks, the eyes are typically located at the base of the sensory tentacles at the top of the head, usualy present as small black dots in the flesh of the head. The conchs have a long protruding proboscis which they use to bite off chunks of algae wheras the whelks usually hqave short snouts and a rasping "licking" means of feeding. In a very real sense, conchs are not rasping grazers but biting algae eaters, a task at which they excel. From your description of both the locomotion, the photos, and the general behavior or your specimen, I think your snail is safe for the tank, however, I would still watch it for a while, just to make sure...

All strombids are animals of the sand and have a small muscular foot which is not adapted to crawling on rocks. They actually move by lurching or jumping, termed saltutory locomotion. This mode of locomotion is good for moving through sandy sediments, but is inefficient and largely ineffective as these snailis grow to sizes above 2 to 3 cm when moving on rocks. This results in these creatures staying in the sand once they reach some size. For this reason, the conchs usually require a sand bed with some depth to it to successfully curate these mollusks. Generally, as a rule of thumb, there should be about one to two square feet of open sand with some algae coverage per inch of snail shell length. Conchs will move around in the sand at the bases of the live rock while foraging and remove algae from quite high up on the rocks using their proboscus while their bodies are still buried. These snails are quite entertaining to watch, although you may need to stay up late at night to see some of their behaviors.

The Queen Conch, Strombus gigas, will grow to quite large sizes given enough algae, with adults reaching sizes of up to 40 to 50 cm. Growth rates of up to 3cm a month in captivity have been reported when adequately fed. However, this often results in the snail becoming so large that it outstrips the ability of a system to supply adequate nutrition, and the conch dies from starvation. Other smaller conchs are equally good at grazing on algae, and should be purchased instead of the queen conchs. Several of the smaller conchs, such as the Florida Fighting Conch, Strombus alatus, are much better suited for the janitorial role we assign these creatures. These conchs have the habit of disappearing under the sand for extended periods, actually moving along under the surface of the sediments eating algae. Occasionally they may stay in one place, using their proboscis to forage in the sediments up to several cm from their stationay position. Although they MAY seem to be totally covered by the substrate, they extend their eyes to or slightly above the sediment's surface, such that through careful inspection one can find them by searching the sediment for the telltale eye stalks.

For more info on conchs vs whelks, see:

http://www.gastropods.com/Taxon_pages/Family_STROMBIDAE.html
http://www.sms.si.edu/irlfieldguide/Melong_corona.htm
http://www.wetwebmedia.com/snailcompfaqs.htm

for some thumbnail pix for attempts at better ID, see http://www.gastropods.com/Taxon_pages/Family_STROMBIDAE.html

HTH

 

[mdcorcoran]

MOST of the conch or conch-like snails are algae and detritus eaters, however there are a few genera that are similar in appearance that are predatory carnivores...

so...when you say predatory carnivores, are you talking about taking down fish and inverts, or mostly corals? I've had a handful of mysterious fish and invert deaths lately (in the past 5 months). My levels have all been great.

 

[Sophie's mom]

Are they related to the Nassarius? They look alot alike. My Nassarius come out swinging when I put brine shrimp in the tank. I have to destract them so my blood shrimp can eat! I didn't know they were carnivores.
Anyone?

 

[tdwyatt]

...when you say predatory carnivores, are you talking about taking down fish and inverts, or mostly corals?

The whelks (depending on specie) are predatory on other snails, clams and oysters, misc other inverts, many types of corals, and any dead fishes etc. they can locate, although I don't think they are quite fast enought yo catch even sleeping fishes... :nuts:

Are they related to the Nassarius? They look alot alike. My Nassarius come out swinging when I put brine shrimp in the tank. I have to destract them so my blood shrimp can eat! I didn't know they were carnivores.

They are all mullusks, and as a group are all conchiferians, but in terms of their ancestrial relationships regarding even simple similarities like torsion and pulmonary relationships, may vary widely. They are all Prosobranchs in that they respire through gills and their gills, mantle cavities, and anus are located at the anterior of the body (torsion is clearly evident). However, delineation of the snails as a group starts at this point. The majority of the prosobranchs are divided into three groups based on their ability to expoit their environmental habitats based on anatomicqal differences: archeogastropoda, mesogastropoda, and neogastropoda (there are other flags involving physiology and anatomy as well, but we're just going to discuss their environmental flags). The archaeogastropods are pretty much limited to the surfaces of rocky substraates or the surfaces of kelps or other firm seaweed thalli where the water is relatively clean and free of suspended particulates. Their gill structure is such that their bipectinate gills are suspended from the dorsal and ventral membranes in the ventiliating current within the shells of these creatures, exposing a very large surface area to potential fouling if exposed to large amounts of suspended materials. The mesogastropods and neogastropods do not utilize membranous suspension of gills, using instead a direct attachment of the gill axis to the mantle wall such that the filaments on the side of the attachment are absent, and those on the other side extend into the mantle, making the gills monopectinate, allowing for a higher percentage of suspended particulates in the ventilating current while reducing the likelihood of fouling of the gills. In addition to these gill evolutions, there is the development of an inhalent siphon (especially in neogastropods) as an extension and inward rolling of the mantle. This allows for intake of surface waters for ventiliation in burrowing species, and acts in some carnivores as a sensory organ for potential food items. In this sense, thes snails in question are very closely related due to their abiity to exploit the substrates and utilize their ventilating currents to their advantages, however, conchs possess specialized feeding apparati that allow them to be superior algal feeders (as discussed previously), wheras many of the whelks have specialized raduli (toothed tongues) that alow them to rasp through shells of potential victims in order to feed on them.

Lots of stuff to talk about with these creatures, a very interesting subject. See either Ruppert/Barnes, Invertebrate Zoology or Purchon, RF, Biology of the Mollusca for more details.

Nassarius as a rule are carnivorous/omnivorous, although I do not think them predatory beyond the occasional feeding on sick or dying fishes (meals of opportunity). They lack the specialied feeding developments for algal feeding tht the conch's employ, although they do have the substrate ventilation apparati that the conchs do.

HTH