Why Molluscs?

It’s been asked of us before “Why study molluscs?” and more recently “Why make mollusc playing cards?”

Why study molluscs?

Because they are very interesting, cool and some even taste great…

Detail from a Sailor's Valentine

Detail from a Sailors Valentine by Bill Jordan

Most of us are familiar with at least a few species of mollusc (Phylum Mollusca), mostly as food like oysters and clams, or as garden pests like snails and slugs. Molluscs have long been important to humans, with solid evidence of man’s use of molluscs as food, tools and ornamentation extending back to the Middle Stone Age (127,000 years ago) in Africa and Eurasia¬†. Today molluscs remain a very important global food source (in excess of 16 million metrics tons of protein) worth in excess of $15 billion . Just as shells provided our ancestors with a trade medium (shell beads) and canvas for art, today the trade (legal and illegal) of sea shells and pearls continues, as does use of shells in art and as inspiration.

Of all the animals, the Mollusca have the second largest number of present day species with 200,000+ species. There are in excess of 130,000 described species of mollusc alive today and conservative estimates put the number of undiscovered or un-described living species at 70,000 or more . The fossil record for Mollusca includes about 70,000 described extinct species and extends back at least to the Cambrian (543 to 490 Million years ago) and possibly to the Neoproterozoic (~543 – 1000 million years ago) if Kimberella proves to be a mollusc.

A Mesonychoteuthis hamiltoni being prepared for study in New Zealand

A sub-adult Mesonychoteuthis hamiltoni being prepared for study in New Zealand

Aside from sheer numbers of extant and extinct species, the molluscs are also one of the most diverse groups of animals, with 8 classes of living organisms and at least two additional classes from the fossil record. Shelled molluscs range in size from less than 1mm (Omalogyra fusca) to the giant clam (Tridacna gigas) at well over a 1.25 meters. While most molluscs are shelled, shell-less molluscs also vary immensely in size (and shape) from 1mm long eyeless worm-like members of the Aplacophora class, which are found living between grains of sand, to the the colossal squid (Mesonychoteuthis hamiltoni), a well-named deep-sea predator which reaches total lengths of at least 14 meters (~46 feet – the length of a bus!) with a dinner plate sized eye that rivals ours in complexity.

Molluscs are an extremely diverse and important group of animals (evolutionarily, ecologically, economically and gastronomically), which makes them both fun and challenging to study. They are found in just about every ecosystem in the world. Often they function as ecosystem engineers, like oysters and other bivalves, which filter the water and can form large reefs. Although there are may molluscs in freshwater and on land, most molluscs are marine. Molluscs have adopted a wide variety of feeding modes including scraping detritus and diatoms from rocks, filter feeding, herbivory and carnivory. There are molluscs with gills and molluscs with lungs, molluscs with and without eyes (and just about every type of eye in-between!), molluscs with a radula (a rasping tongue like organ found only in molluscs) and molluscs without. Some molluscs have very simple brains, others are extremely complex (very intelligent those cephalopods!).

Why mollusc cards?

Unfortunately what makes them fun and challenging to study can also sometimes make it difficult to explain, especially to all age groups and often in a very limited time frame. There is no “All molluscs have….” rule for molluscs as there are with most other animal groups. Any simplification risks over-simplifying, yet we rarely have time – or attention span – to go into a great deal of detail. We wanted to have an outreach product that we could use with a wide range of ages and education levels as a fun reinforcement tool that focuses attention on the diversity of marine molluscs . We wanted something that could augment our other outreach activities during presentations, but that could also be left with a class and continue to educate curious minds. We wanted something kids and adults could, and would, pick up and use to play the card games they already know, but then be able to see and read about molluscs at the same time. Thus the Mollusc Playing Cards were born.