mollusks: mollusca

anonymous asked:

Why are slugs catergorized with mollusk even though they do not have a shell?

There are several reasons why. Firstly, not all slugs lack shells. Several slugs have (small) internal shells and in some species these shells are obvious 


In others the shell is typically buried in the the mantle or reduced to just calcium crystals, others do completely lack a shell. Secondly, and probably most importantly, “slugs” evolved from molluscs! “Slugs” are not a real taxonomic category as the term slug is given to any shell-less gastropod so slugs are in no way a monophyletic group. Anyways, we call slugs molluscs because they evolved from molluscs! Slugs in most cases (I’m not getting into marine lineages) are descended from snails that eventually lost or had a reduction in their shells. 

Finally and this is definitely the most important reason, not all molluscs have shells! The phylum mollusca has multiple classes, which typically united via the presence of a muscular foot or a mantle:


Octopodes lack true shells and there is even a whole class of molluscs that completely lack shells, the aplacophora (which translates to: not plate bearing). Aplacophorans are pretty rare and worm like in form, most species are burrowers and many have calcium spicules embedded in their mantles to provide rigidity. 






I was recently reading a paper (Indirect paleo-seagrass indicators (IPSIs): A review)* on ways in which paleontologists can infer the presence of ancient seagrass beds (seagrasses are apparently really bad at being fossilized) and found this really cool fossil!  It’s a middle Eocene oyster (Cubitostrea) whose shell overgrew a colony of hydroids (Dynamena) that were growing on a seagrass blade!  You can see the impression of the hydroids pretty clearly (they’re the deep screw-shaped gougy impressions), and if you look more closely you can see the subtle vertical lines that are the impressions of the ancient seagrass leaf veins!  so awesome.   

*it’s behind a paywall, but if you’re interested I can send you a Google drive link!

anonymous asked:

Heyhey! I was wondering, do you have any pets?

HEYHEY! Yes I do! I have snails! - 3 garden, and 1 strawberry.

This is Marvin, named so because he’s ALWAYS eating (Hank Marvin… Starving…Cockney rhyming slang… no? okay..), he’s a garden snail (Helix aspersa).

He’s literally the stupidest little dude ever.

Next up we have Humphrey, also a garden snail (Helix aspersa)

He is also a daft little noot, but far less daft than Marvin.

Last in the terrible trio of garden snails is Gerard.

He’s old. He’s grumpy. He’s fabulous.

And the last of my snails isn’t actually a garden snail, but a Strawberry snail (Trochulus striolatus). His name is Franklin. He is the most adorable little thing in the entire world.


Ugh he’s just so precious.


Ocean acidification is predicted to have detrimental effects on many marine organisms and ecological processes. Despite growing evidence for direct impacts on specific species, few studies have simultaneously considered the effects of ocean acidification on individuals (e.g. consequences for energy budgets and resource partitioning) and population level demographic processes.

A new study claims that the acidification of the ocean could be negatively altering the population dynamics of marine species and preventing them from being able to adapt to future climate change. In particular, the study examines the gastropod banded dye-murex (Hexaplex trunculus), a widespread Mediterranean mollusc.  and its response to ocean acidification over numerous generations, and found that they trade-off the maintenance of their shells in order to compensate for the living conditions of acidified oceans, which poses a higher cost of living.

UK researchers  discovered that that these changes to the energy budget may not be the same for males and females, and at a population-level, those individuals contributing to reproduction change year-on-year, resulting in a genetic drift that could hinder the potential for genetic adaptation to ocean acidification

Acclimatization can buffer populations against the immediate impacts of ocean acidification, and even provide time for adaptation (…) However, it can also result in stress-induced energetic trade-offs, and unless organisms can compensate for the extra costs caused by ocean acidification, then they may suffer negative consequences in the form of reduced growth, development and reproduction. said Samuel Rastrick, who participated in the research.

Even against a background of high gene flow, ocean acidification is driving individual- and population-level changes that will impact eco-evolutionary trajectories.