Tim Pearce

by Tim Pearce

Chemicals in our medications, supplements, foods, and beverages often pass through our bodies and wind up in our wastewater. Antidepressants are one of the more common pharmaceuticals in wastewater, and in some samples, concentrations of the stimulant caffeine exceeded those of pharmaceuticals (Raj et al. 2021). Although treatment plants can remove more than 50% of caffeine, the enormous popularity of caffeine consumption by humans results in such large levels of this chemical in wastewater that caffeine is sometimes used as an indicator of human-caused pharmaceutical pollution. These chemicals, along with our vitamins and other food additives, can affect freshwater organisms.

In this blog, I focus on two common chemicals: Prozac (fluoxetine) and caffeine (e.g., coffee, tea). 

Prozac in low concentrations stimulates reproduction in marine and freshwater bivalves (Fong & Ford 2014), as well as in some freshwater snails, including the invasive New Zealand mud snail (Pomatopyrgus antipodarum). Interestingly, high concentrations of Prozac decreased reproduction in the snails. 

Clams on Prozac release gametes or young (Fong & Ford 2014). Small freshwater pill clams (Sphaeriidae) brood their young, and Prozac stimulates the release of these brooded offspring. In freshwater mussels, Prozac stimulates release of their larvae. Our knowledge of this effect can be used to augment propagation efforts to support recovery of endangered freshwater mussel species, but only with a clear understanding of these fascinating creatures’ full reproductive cycle. As part of their development, freshwater mussel larvae temporarily attach themselves to the gills of fish. If Prozac in the water of a natural setting stimulated larval release at times when fish hosts were absent or the larvae were too immature to attach, then the Prozac would be counterproductive to mussel reproduction.

Caffeine negatively affects marine bivalves by inducing oxidative stress (Júnior et al. 2019), leading to degradation of cell membranes (Silvia et al. 2022). When exposed to environmentally relevant concentrations of caffeine, the freshwater clam Corbicula fluminea experienced physiological changes, including DNA damage (Aguirre-Martínez et al. 2015). Caffeine might have less effect on freshwater snails. One study on the freshwater snail Helisoma trivolvis showed little effect of caffeine on adult survival, but normal embryonic rotation in developing eggs was slowed at higher caffeine concentrations (Sanchez & Prezant 2016). (The caffeine used as a slug repellent in terrestrial agriculture is in much greater concentrations than that found in wastewater.)

If you needed another reason to reduce your consumption of pharmaceuticals and caffeine, the fact that it affects reproduction in freshwater creatures could be a consideration.

These findings about anti-depressants in our wastewater give new meaning to the phrase, “Happy as a clam.”

Timothy A. Pearce, PhD, is the head of the mollusks section at Carnegie Museum of Natural History.

Literature Cited

Aguirre-Martínez, G.V., DelValls, A.T. & Martín-Diaz, M.L. 2015. Yes, caffeine, ibuprofen, carbamazepine, novobiocin and tamoxifen have an effect on Corbicula fluminea (Müller, 1774). Ecotoxicology and Environmental Safety, 120: 142–154.

Fong, P.P. & Ford, A.T. 2014. The biological effects of antidepressants on the molluscs and crustaceans: a review. Aquatic Toxicology, 151: 4-13.

Júnior, C.A.M., Luchiari, N.C. & Gomes, P.C.F.L. 2019. Occurrence of caffeine in wastewater and sewage and applied techniques for analysis: a review. Eclética Química Journal, 44(4): 11-26.

Raj, R., Tripathi, A., Das, S. & Ghangrekar, M.M. 2021. Removal of caffeine from wastewater using electrochemical advanced oxidation process: a mini review. Case Studies in Chemical and Environmental Engineering, 4: 100129.

Sanchez, D. & Prezant, R.S. 2016. Influence of diphenhydramine HCl and caffeine on embryonic development and adult reproductive success of the freshwater gastropod Helisoma trivolvis. American Malacological Bulletin, 34(2): 92-102.

Silvia, S., Cravo, A., Rodrigues, J., Correia, C. & Almeida, C.M.M. 2022. Potential impact of UWWT effluent discharges on Ruditapes decussatus: an approach using biomarkers. Advances in Environmental and Engineering Research, 2(2): doi:10.21926/aeer.2102015 [18 pp].

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by Dr. Timothy A. Pearce

A reader recently asked whether snails can feel love. I sometimes wonder that too; do my pet snails feel any affection for me? I don’t know the answer, but I’ll discuss this intriguing question from two perspectives: biochemical and philosophical.

Biochemically, many of our emotions are influenced by hormones. For example, higher levels of the hormone oxytocin are associated with greater trust and affection. Hormones in other species might have similar effects, for example, oxytocin in octopuses is associated with behaviors that are reasonably interpreted as affection. Humans and octopuses are very different evolutionarily – the common ancestor between our lineages occurred a very long time ago, at least 500 million years ago. The presence of oxytocin as an influencing hormone in both humans and octopuses could be interpreted as, (a) the ability to produce and respond to oxytocin might have been present in all or most animals living 500 million years ago and consequently is present in most modern animals that descended from those ancestors, or (b) the ability to produce and respond to oxytocin might have evolved independently in the lineage that led to humans and in the lineage that led to octopuses. A recent paper (Kumara et al. 2020) reported oxytocin-like proteins in a wide variety of vertebrates and invertebrates, suggesting the first possibility, that oxytocin might be widespread in animals due to shared common ancestry. If oxytocin, and other hormones that are associated with what we humans experience as love, are present in snails, then it could be reasonably argued that snails at least have the potential to feel love.

Philosophically, in an evolutionary perspective, what would love be good for? Love in the broad sense might be useful in social organisms to strengthen bonds between individuals such as partners, parents and offspring, and group members working toward a common goal. Inter-species bonds, such as humans and their pets, or even between individuals of non-human species, are reasonably interpreted as manifestations of love. However, these evolutionary benefits of love are for social species, and I can’t think of any social snails. Snails do not show evidence of mate fidelity or parental care, and they do not seem to crave each other’s company. Although snails sometimes gather in large numbers, my study of such aggregations suggests mutually valued resources are the cause of such occurrences rather than a desire to be together (Pearce & Porter 2011). So, I can’t think how the capacity to experience love would be useful to a snail in a way that evolution could select for a snail’s ability to feel love.

Snails do copulate, for reproduction, and that can be interpreted as a form of love. Some snails use calcareous darts, often called “love darts” as part of a courtship dance before copulation (the darts themselves are not used in sperm transfer). Reproductive behaviors are probably influenced by hormones. I like to think that snails find reproduction to be a pleasurable experience, but we really don’t have much idea what is pleasurable to a snail.

We sometimes use the word love to mean intense liking. In this sense, snails might have the capacity to love. I have noticed some of my pet snails are so attracted to cucumbers that I commonly say, “Snails love cucumbers.” I interpret the consumption of cucumbers as being deeply satisfying to snails.

In summary, snails might have the biochemical potential to feel love, but they might not have a socially-mediated evolutionary reason to feel love. They engage in reproductive behaviors, but we don’t know whether they feel love or pleasure during reproduction. At least some snails seem to have an intense like for cucumbers. Maybe snails do feel love, and maybe they don’t; we don’t know. You are free to believe as you like. Your pet snail Fluffy might really love you!

Timothy A. Pearce, PhD, is the head of the mollusks section at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Literature Cited

Kumara, S., Vijayasarathya, M., Venkatesha, M.A., Sunita, P. & Balaram, P. 2020. Cone snail analogs of the pituitary hormones oxytocin/vasopressin and their carrier protein neurophysin. Proteomic and transcriptomic identification of conopressins and conophysins. Biochimica et Biophysica Acta (BBA) – Proteins and Proteomics, 1868(5): 140391

Pearce, T.A. & Porter, K.A. 2011. Do Philomycus carolinianus (Gastropoda: Philomycidae) prefer to congregate? Nautilus 125: 83-85.

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by Timothy A. Pearce

Despite typical depictions of outer space creatures in movies and on TV, the chance that extra-terrestrial aliens will look like us is vanishingly small, and they are also likely to think and communicate very differently than we do. Most species on Earth communicate with smells (note that most animal species on Earth are insects), while fewer species, including humans, communicate primarily with sight and sound. As far as I know, humans are the only ones on Earth using radio waves to communicate, although radio transmitters and receivers are external to our biological bodies. (Nerds will point out that radio waves and light waves are all part of the electromagnetic spectrum, just pulses of the same phenomenon at different frequencies.) 

If we humans actually made contact with extra-terrestrial alien intelligence, how would we communicate with them? Extra-terrestrial organisms, likely being completely separate instances of life, and potentially evolving under dramatically different temperatures and chemical environments (think cold moons of Jupiter or Saturn where the solvent of life could be liquid hydrocarbons instead of water), might not use smell, sight, or sound as Earth creatures do. They might have very different ways of conveying information. 

I suggest if we want to practice communicating with space aliens, we should look no further than our 8-legged ocean intelligence: the octopus. The octopus is evolutionarily the most different of all the intelligences on Earth. Here, I include in the “intelligence club” organisms such as primates (including humans), cetaceans (dolphins and whales), certain birds (parrots, jays, and crows), and cephalopods (particularly octopus). If you’d like to include other favorite creatures capable of acquiring and applying knowledge, such as elephants, dogs, and horses, well sure, we can include them in the intelligence club. What I want you to notice is that all of them except the cephalopods are vertebrate animals, and all but the birds are mammals. 

The cephalopods are the most different of all those intelligences. The cephalopod and vertebrate lineages split from each other more than half a billion years ago. Although the common ancestors of the different vertebrate lineages were not likely highly intelligent, something about the vertebrate body plan might have been a precursor for intelligence. If this is the case, we might expect similarities in the different instances of vertebrate intelligence. On the other hand, because cephalopods and their intelligence came from a very different ancient ancestor, it is as different an intelligence as we can find on Earth. To appreciate how different, look up the fundamental difference between protostomes (including octopus) and deuterostomes (including vertebrates).

I suggest that our best chance to practice communicating with space aliens is to practice communicating with octopuses.

One other non-vertebrate I can think of that might be considered for the intelligence club is the jumping spider (family Salticidae, particularly genus Portia), whose intelligent hunting behaviors indicate they can reason and learn. And hey, they have eight legs, just like the octopus. Coincidence? What do you think?

Timothy A. Pearce, PhD, is the head of the mollusks section at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

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by Timothy A. Pearce

When classifying organisms into broad categories, many people would group snails with insects rather than mammals. When it comes to diet, however, snails are much more like mammals than insects. That’s because, when choosing what to eat, insects tend to be specialists, while most mammals, and most snails, tend to be generalists. This pattern is especially striking when considering just herbivorous species.

Many herbivorous insects specialize on eating one or a few species of plants, and most often within a single plant family. For example, when we think of tent caterpillars, we expect to see them on cherry trees. In the caterpillar life stage of butterflies and moths, 69% of species feed upon just a single family of plants. If you look at just tropical butterflies and moths found within 25 degrees of the equator, the figure rises to 83% (Forister et al. 2015). Herbivorous mammals, on the other hand, tend to be generalists, eating a wide variety of plants from numerous plant families. Snails, it turns out, have broad diets including a variety of plants from numerous plant families, making snails more like mammals than insects, at least in their diets.

Of course, there are exceptions. While most herbivorous mammals are generalists, two mammals are famous diet specialists. Can you think of them? Hint: one eats bamboo, the other eats Eucalyptus leaves. Did you come up with panda and koala? Good for you! Similarly, while most insects are diet specialists, sometimes we do hear about plagues of locusts that have broad diets, so they eat practically every green thing in sight.

Most plants make chemicals that are not directly involved in growth or other metabolic functions. Scientists call these chemicals secondary compounds. In fact, secondary compounds are responsible for many of the distinct aromas and tastes in the spices we rely upon to flavor our cooking. But why would plants bother making secondary compounds that don’t directly benefit the plant? The most common hypothesis for why plants make secondary compounds is to protect the plants from diseases or herbivores.

Herbivores have ways (e.g., enzymes) to detoxify or reduce the effects of plant chemical defenses. Herbivorous insects that specialize on a few related species of plants can, over evolutionary time, develop strategies that effectively detoxify the defenses of those plants. Sometimes co-evolution results, an ongoing process in which the plant will modify its secondary compound to be more toxic, then the insect will develop the ability to detoxify that, and so on. The plant’s arsenal of chemical defenses protects it from the vast majority of herbivorous insects, but not the insects that specialize on that particular plant group. For example, milkweed is fed on by only a very few insects, including monarch butterfly caterpillars, that have countered its defenses.

In contrast to specialist insect herbivores, mammals tend to eat a wide variety of plant species. Consequently, mammals need general detoxification strategies that will protect them from a variety of plant secondary compounds. Thanks to detoxification enzymes located mostly in our livers and kidneys (Freeland & Janzen 1974), we can enjoy eating a wide variety of tasty plants without being poisoned.

Like herbivorous mammals, herbivorous snails also have general detoxification strategies, which might account for their large livers, where most of the detoxification occurs.

Now you know one way that snails are more like cows than insects: their diet!

Here is a joke about snails eating:

Two snails were munching a tasty salad made with a large number of different plants. One of the snails accidently dropped one of the exotic leaves from the salad. The other snail said, “You can still eat it, use the five-hour rule.”

Timothy A. Pearce is the head of the Section of Mollusks at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Literature Cited

Forister, M.L., Novotny, V., Panorska, A.K., Baje, L., Basset, Y., Butterill, P.T., Cizek, L., Coley. P.D., Dem, F., Diniz, I.R., Drozd, P., Fox, M., Glassmire, A.E., Hazen, R., Hrcek, J., Jahner, J.P., Kaman, O, Kozubowski, T.J., Kursar, T.A., Lewis, O.T., Lill, J., Marquis, R.J., Miller, S.E., Morais, H.C., Murakami, M., Nickel, H., Pardikes, N.A., Ricklefs, R.E., Singer, M.S., Smilanich, A.M., Stireman, J.O., Villamarín-Cortez, S., Vodka, S., Volf, M., Wagner, D.L., Walla, T., Weiblen, G.D. & Dyer, L.A. 2015. Global insect herbivore diet breadth. Proceedings of the National Academy of Sciences, 112(2):442-447; DOI: 10.1073/pnas.1423042112

Freeland, W.J. & Janzen, D.H. 1974. Strategies in herbivory by mammals: the role of plant secondary compounds. American Naturalist, 108(961): 269-289.

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