Bad at Goodbyes

Rough Transcript

Intro 00:05

Welcome to Bad at Goodbyes.

On today’s show we consider the Greater Bermuda Land Snail

Species Information 02:05

The Greater Bermuda Land Snail is a critically endangered mollusk native to the island of Bermuda, in the Atlantic Ocean, roughly 700 miles east of the North American continent.

 

The Greater Bermuda Land Snail is a relatively large land snail, with adult shells reaching up to one inch in diameter. So like the size of a bottlecap. Pretty small, but compare to the also endangered Lesser Bermuda Land Snail, whose shell is about 1/3 of an inch in diameter, or to the Bermudian microsnail Vertigo marki, at 1/16th of an inch, our Greater Bermuda Land Snail, earns its name.

 

The Greater Bermuda Land Snail’s shell is a flattened disc shape, with 5-6 whorls of varied coloration: pale yellows, ambers, greens, deep reds, browns, often with very darker brown streaks or speckles. The shell’s surface is smooth and glossy, with small visible growth lines. There is great variation and diversity between different individuals’ shells, and they are really beautiful, like tiny twirled galaxies.

 

Snails grow their shells. Shell material is secreted by a specialized organ in the mantle, a fold of skin that covers the snail’s internal organs. The mantle edge contains glands that produce a mixture of proteins and minerals, which are deposited in layers, gradually building up the shell over time.

 

Shell growth begins even before birth. The initial shell, called the protoconch, is formed within the egg and then once hatched, the snail continues to add new material to the shell’s opening, resulting in a spiral pattern, the characteristic whorls we see on the shell.

 

As the snail grows, the shell increases in size and thickness. The new shell material is added at the outer edge, resulting in visible growth rings that can be used to estimate the snail’s age.

 

The snail’s shell is shelter, armor, protection from predation, camouflage, and helps regulate water loss. Unlike other invertebrates that swap shells as they grow, the snail keeps its shell throughout its life and can even repair cracks and breaks, secreting calcium carbonate to mend an injury.

 

The safety of its hard shell is so vital, because its body is a little squishy blob. It is thin skinned, soft and moist. The land snail is an invertebrate, which most simply means it does not have a skeletal backbone. Invertebrate are a wildly expansive and diverse class of species including ants, bees, beetles, Butterflies, clams, Corals, crabs, Earthworms, Jellyfish, lobsters, octopuses, oysters, shrimp, Spiders, squid and of course snails.

 

Snails, again lacking a skeletal backbone, instead have a hydrostatic skeleton, which means their body is supported by fluid pressure. So like imagine a water balloon, the water inside pushes outward against the balloon’s walls, creating pressure that gives the balloon its form and firmness.

 

Inside the snail is a cavity called a coelom, which holds most of the internal organs, is filled with a pressurized fluid that provides a kind of internal support system. But of course this is an extremely flexible and dynamic support structure, which allows the snail to somewhat change shape and size, retract entirely into its shell when threatened, and it facilitates locomotion.

 

Snail locomotion is totally amazing. Their foot is a strong, flexible organ located on the underside of the body. It contains a network of muscles that contract in a wave-like pattern, pushing downward in like a series of ripples that propel the snail forward. The muscle action works in tandem with the hydrostatic skeleton, the coelom, which allows the foot to deform and reshape to generate this wave action and the necessary pressure for movement.

 

For many snail species including our Greater Bermuda Land Snail this muscle action needs a little lubrication. So they’ll also secrete a specialized mucus to reduce friction and enable smooth movement. The mucus, produced by glands in the foot, creates a slippery track on which the snail glides. The mucus has protective qualities and is both lubricating and semi-adhesive, allowing the snail to traverse a variety of surfaces, even rough and sharp textures, and the semi-adhesive qualities allows for vertical climbing.

————

In the dream,

 

me and Alice Coltrane, Albert Einstein, Mary Oliver, Stephen Jay Gould, are playing free jazz in my practice space. “Tempo is relative,” Al says and we all nod. And in the dream, I’m reminded of the privilege of inconveniences. To walk to a place, because you have the time. To be slow under moonlight, safely. To meander in the storm because I know my home is dry and warm. Sometimes when I’m walking him home, I say to my nephew, “take it easy bub, maybe we will be a few minutes late, but at my pace we’ll have longer together.”

 

In the dream.

————

The Greater Bermuda Land Snail has a flattened cylindrical body that when extended is about 2 inches long. It is gray, blue-gray, brown-gray in color. It has a distinct head with two pairs of tentacles. These are the primary sense organs: Upper Tentacles, called ommatophores, “eye stalks”, are long, protruding from the top of the head and the very tip of each holds a simple eye, capable of detecting light and dark, movement, and basic shapes. 

 

The Lower Tentacles are shorter and generally downward facing, primarily used to sense touch and smell. All four tentacles can move independently, allowing the snail to gather information from different directions. And both sets are retractable. The snail can quickly withdraw the tentacles into its head for protection.

 

The snail’s mouth is located on the underside of its head. It feeds using its radula, this is a ribbon, a tongue-like structure, in the mouth, that’s covered in rows of tiny teeth. And so the snail extends its radula out of its mouth and scrapes its teeth against a food source. The teeth catch and hold food particles and then the radula is retracted, pulling the food bits into the snail’s mouth.

 

The Greater Bermuda Land Snail is an herbivore, and they are opportunistic feeders consuming available algae, palm nut, and decomposing plant matter, specifically dead palm fronds.

 

They are most active at night, to minimize water loss and avoid predators. During the day, to regulate body temperature and moisture, they shelter in cool, damp places, under rocks, logs, leaf litter, or in crevices. Their flattened shell shape is thought to be an adaptation to this behavior, allowing them to squeeze into smaller places.

 

The Greater Bermuda Land Snail is hermaphroditic, meaning they possess both male and female reproductive organs. That said, they do require a mate for viable reproduction. And we have observed some courtship behavior in which potential mates will circle one another gently touching their eyestalks, before copulation which is a like a mutual sperm transfer. Both individuals will release sperm within the other individual, which fertilizes eggs internally. The eggs are laid in clutches ranging from 10 to 50 eggs. And once hatched the young snails are born independent, immediately able to forage for food and seek shelter. And are believed to reach reproductive maturity in roughly 18 months. Lifespan is estimated at 2-3 years.

 

The fossil record suggests that the Land Snail has lived on the Bermuda Islands for over 1 million years.

 

The Greater Bermuda Land Snail was once widespread across the Bermuda archipelago, a group of islands located in the North Atlantic Ocean, roughly 700 miles east of the North American coast. Its native habitat is subtropical moist broadleaf forest, an ecosystem characterized by Bermuda palm and Baygrape with an understory of shrubs, ferns, and grasses, with the forest floor covered in leaf litter, stones, and decaying logs under which the snail shelters.

 

Bermuda’s climate is subtropical, with warm, humid summers and mild winters. Summer temperatures typically reach highs in upper 80s°F, while winter temperatures rarely drop below 50°F.

 

The snail shares these islands with Bermuda Skink, Jamaica Dogwood, Eastern Bluebird, Green Heron, Bermuda Cedar, Cloudless Sulphur Butterfly, American Coot, Olivewood, Fennel, Red Land Crab, Bermuda Rock Lizard, White-Eyed Vireo, Inkberry, Hurricane Spider, Bermuda Buckeye Butterfly, Land Hermit Crab, and many many more.

 

On Bad at Goodbyes we tend to want to give most attention to the species at hand, but I’d like to sidebar briefly because the Greater Bermuda Land Snail plays a vital supporting role in human scientific history. Bermuda Land Snails were the research subject of the doctoral dissertation of American paleontologist, evolutionary biologist, educator, and public intellectual Stephen Jay Gould. Gould, studying the snail’s fossil record in Bermuda developed, with Niles Eldredge, the theory of punctuated equilibrium. The idea, first proposed in 1972, is that evolution sometimes occurs in bursts of rapid change between long periods of relative stability. So a species will exhibit minimal evolutionary differentiation, over a long time, that’s the equilibrium part. Which will be punctuated by brief periods, often driven by new natural selection pressures, of rapid evolutionary change and speciation.

 

This theory, which is now so widely accepted that you may have studied it in school, is not a replacement for Darwin’s gradualism, which suggests that evolution proceeds at a slow and steady pace. But instead a complement: evolution is both slow and steady, and also sometimes punctuated by periods of rapid change and speciation.

 

And so Gould’s study of the Greater Bermuda Land Snail has significantly widened our view and understanding of evolutionary history.

 

Lastly, uh, I really like Stephen Jay Gould, his profoundly well-argued and researched refutation of racist methodologies in the historic measurement of human intelligence had a big impact on me when I was a young learner. The book is called the “Mismeasure of Man” and it’s a reminder of how bias and toxic ideology can pollute even our most rigorous truth seeking like the scientific method. And also a reminder that science and justice can be in real conversation in ways that uplift both.

 

When Gould is studying the snail in the 1960s their population is widespread across the larger Bermuda Islands. When he returns in the 1990s he finds their population shockingly and significantly reduced. This is just like Human hubris and shortsightedness. In the time between Gould’s studies, the predatory Rosy Wolfsnail had been intentionally introduced to Bermuda in an effort to control the population of another introduced invasive snail, the Milk Snail. The Rosy Wolfsnail population exploded feeding on, as may have guessed, not the Milk Snail but instead on native snail species, like the Greater Bermuda Land Snail. In the 1990s the Greater Bermuda Land Snail was considered extinct in the wild.

 

Until the discovery of two small remaining um, wild populations. One on Port’s Island: a tiny, less than a 1/4 of square mile, relatively undeveloped island of second growth forest roughly a mile from the main island. The other population was found in 2014, unbelievably, in an alley behind an ice cream shop in the capital city of Hamilton. Like this is one of the most rare snails in the world and roughly 300 individuals are surviving in the concrete cracks of this overgrown alleyway in the middle of one of Bermuda’s largest cities.

 

Individuals collected from the Hamilton alley population became the basis of captive breeding programs at the Bermuda Aquarium Museum and Zoo, and the UK’s London Zoo and Chester Zoo. The Hamilton population was then relocated to an outer island when building developers wanted to power-wash the alley.

 

These captive breeding programs have had mixed sucess: From 2016-2022, over 100 thousand Greater Bermuda Land Snail have been reintroduced across 27 sites in Bermuda, 10 of which are small, woodland island nature reserves where predators are either absent or controlled. A 2022 report suggests that four of these sites appear to be thriving, with the introduced population reproducing and spreading out in the habitat. Two other sites have failed, for unknown reasons. Monitoring of the remaining sites is in process.

 

Captive breeding, reintroduction, and habit restoration programs continue, but nevertheless the Greater Bermuda Land Snail has been considered critically endangered on the IUCN Red List since 2019 and their population is considered to be in decline.

 

Counts estimate that less than 4000 Greater Bermuda Land Snail remain in the wild.

Citations 26:41

Information for today’s show about the Greater Bermuda Land Snail was compiled from:

 

“Bionic Snail Robot Enhanced by Poroelastic Foams Crawls Using Direct and Retrograde Waves.”. Ji, Qinjie & Song, Aiguo. (2023). Soft Robotics. Vol 11. – http://dx.doi.org/10.1089/soro.2023.0077 

Envirotalk v.87 no.1 Spring 2023. Dr. Mark Outerbridge – https://static1.squarespace.com/static/501134e9c4aa430673203999/t/64414a030dc7664ce91691bf/1682000388899/87.1+Spring+2023.pdf 

“An evolutionary microcosm: Pleistocene and recent history of the land snail P. (Poecilozonites) in Bermuda”. Stephen Jay Gould. Bulletin of The Museum of Comparative Zoology, volume 138, issue 7, pages 407-531. 1969 – https://www.biodiversitylibrary.org/page/4631797 

“‘Extinct’ Bermuda snail is found in city alleyway”. Simon Jones. The Royal Gazette. Oct 25, 2014 – 

https://www.royalgazette.com/other/news/article/20141025/extinct-bermuda-snail-is-found-in-city-alleyway/  

The Government of Bermuda Department of Environment and Natural Resources – https://environment.bm/ 

“Habitat preferences of the Critically Endangered greater Bermuda land snail Poecilozonites bermudensis in the wild.” Copeland A, Hesselberg T. Oryx. Vol 56 No.1 :34-37. http://doi.org/10.1017/S0030605320000836  

IUCN – https://www.iucnredlist.org/species/77145002/77145257 

PBS Evolution Library – https://www.pbs.org/wgbh/evolution/library/03/5/l_035_01.html 

“Recovery plan for the endemic land snails of Bermuda; Poecilozonites bermudensis and Poecilozonites circumfirmatus.” Outerbridge, Mark & Sarkis, Samia. (May 2019). Institute of Environment and Natural Resources, Bermuda – http://doi.org/10.13140/RG.2.2.18957.79848 

“Reintroduction of the Bermudan snail.” Garcia, Gerardo & Jameson, Tom & Prince, Heather & Flewitt, Amber & Papp, Tamás & Richardson, Adam & Lopez, Javier & Outerbridge, Mark & Ovaska, Kristiina. (2020). BIAZA Field Conservation & Native Species Conference January 2020

“Tagging and location preferences to inform post-release monitoring of the Greater Bermuda land snail Poecilozonites bermudensis.” Flewitt, A., Williams, L., Preziosi, R., & Garcia, G. (2023). Journal of Zoo and Aquarium Research, Vol 11 No. 3, 345–349. https://doi.org/10.19227/jzar.v11i3.744 

Wikipedia – https://en.wikipedia.org/wiki/Bermuda_land_snail 

 

For more information about the conservation and protection of the Greater Bermuda Land Snail please visit

the Bermuda Department of Environment and Natural Resources at https://environment.bm/

Music 28:44

Pledge 35:23

I honor the lifeforce of the Greater Bermuda Land Snail. I will commit its name to my record. I am grateful to have shared time on our planet with this being. I lament the ways in which I and my species have harmed and diminished this species. I grieve.

 

And so, in the name of the Greater Bermuda Land Snail I pledge to reduce my consumption. And my carbon footprint. And curb my wastefulness. I pledge to acknowledge and attempt to address the costs of my actions and inactions. And I pledge to resist the harm of plant or animal kin or their habitat, by individuals, corporations, and governments.

 

I pledge my song to the witness and memory of all life, to a broad celebration of biodiversity, and to the total liberation of all beings.