I Can’t Sleep - Sand Dollars | Gentle Bedtime Reading for Sleep

Episode Date: April 25, 2025

Unwind with this calm bedtime reading about sand dollars, designed to ease insomnia and bring gentle relaxation to your night. In this soothing episode, Benjamin explores these unique sea creatures, sharing their biology, habitats, and the stories people have told about them through history. His steady, comforting narration transforms fascinating natural details into a peaceful listening experience, helping quiet your mind and reduce stress. There is no whispering or hypnosis, only calm, fact-filled storytelling to guide you toward sleep. Press play, close your eyes, and let the world of sand dollars carry you into slumber. Want More? Request a topic: https://www.icantsleeppodcast.com/request-a-topic Listen ad-free & support: https://icantsleep.supportingcast.fm/ Shop sleep-friendly products: https://www.icantsleeppodcast.com/sponsors This content is derived from the Wikipedia article on Sand dollars, available under the Creative Commons Attribution-ShareAlike (CC BY-SA) license. Read the full article: Wikipedia – Sand dollars. Next Week on the I Can’t Sleep Podcast ➗ Pure Mathematics – Numbers so abstract, they’ll knock you out. 🦷 Dental Hygienist – Clean teeth, clear mind, fast asleep. 🔥 Iroh & Zuko – Tea, wisdom, and a journey worth dozing off to. New episodes drop Sunday, Tuesday, and Thursday at 6 PM MT. Until then… happy sleeping. 💤 Learn more about your ad choices. Visit megaphone.fm/adchoices

You're listening to a Glassbox media podcast. What if I told you that most of the modern day self-help advice you've been hearing could actually make you worse? The key to a better life isn't about feel-good gimmicks that sound catchy. The Mentally Stronger Podcast gives you access to a licensed therapist who shares science-backed tools that will actually change your life. Hi, I'm Amy Morin, psychotherapist, mental strength trainer, and international best-selling author. In each episode, we cover research-back strategies, like how to stop relying on willpower and start creating habits for lasting change. And the five mental strength-building exercises you can do from your couch. I also speak to world-class experts like Dr. Nicole Kane, who shares how to permanently heal anxiety by addressing the root cause.

With over 200 episodes in our catalog, this podcast is for you if you're ready to crush self-doubt, conquer challenges, and become stronger than ever with therapist-approved strategies that can change your life. Listen to Mentally Stronger with therapist Amy Morin, wherever you get your podcasts. Welcome to the I Can't Sleep podcast, where I bore you to sleep, one fact at a time. I'm your host, Benjamin Boster. Thanks to Megan Kay for sponsoring tonight's episode about Sand Dollars. Sandalers, also known as sea cookies or snapper biscuits in New Zealand and Brazil, or pansy shells in South Africa, are species of flat burrowing sea urchins belonging to the order

glipiasteroida. Some species, within the order, not quite as flat, are known as sea biscuits. Sand dollars can also be called Sanjolars. cakes or cake urchins. The term sand dollar derives from the appearance of the test's skeletons of dead individuals after being washed ashore. The test lacks its velvet-like skin of spines and has often been bleached wide by sunlight. To beachcomers of the past this suggested a large silver coin, such as the old Spanish dollar, which had a diameter of of 38 to 40 millimeters.

Other names for Sand Dollar include Sand Cakes, Pansy shells, Snapper biscuits, cake urchins, and sea cookies. In South Africa, they are known as pansy shells for the suggestion of a five-petaled garden flower. The Caribbean Sand Dollar, or inflated sea biscuit, is thicker in height than most. In Spanish-speaking areas of the Americas, the sandalers is most often known as Goleta de Mar, sea cookie.

The translated term is often encountered in English. In the folklore of Georgia and the United States, sand dollars were believed to represent coins lost by mermaids. Sand dollars diverged from other irregular equinoids, namely the cassiduloids, during the early Jurassic, with the first true sand-dollar genus, Tocayamus, arising during the Paleocene. Soon after Togochaemus, more modern-looking groups emerged during the Eocene. Sand-dollars are small in size, averaging from 80 to 100 millimeters. As with all members of the Order Clipiasteroida, they possess a rigid skeleton called a test. The test consists of calcium carbonate plates, arranged in a five-fold symmetric pattern.

The tests of certain species of sand daller have slits called lunials that can help the animal stay embedded in the sand to stop it from being swept away by an ocean wave. In living individuals, the test is covered by a skin of velvet textured spines, which are covered with very small. hairs, cilia. Coordinated movements of the spines enables sandalers to move across the seabed. The velvety spines of live sand dollars appear in a variety of colors, green, blue, violet, or purple, depending on the species. Individuals which are very recently dead or dying are sometimes found on beaches, with much of the external morphology still intact. Dead individuals are commonly found with their empty test devoid of all surface material and bleached white by sunlight. The bodies of adult sandalers like those of other equinoids display radial symmetry.

The petal-like pattern in sand dollars consists of five paired rows of pores. The pores are perforations in the endoskeleton through which bodia for ghat. exchange project from the body. The mouth of the Sandalor is located on the bottom of its body at the center of the petal-like pattern. Unlike other urchins, the bodies of Sandullers also display secondary front-to-back bilateral symmetry, with no morphological distinguishing features between males and females. Sand-dollars can be found in temperate and tropical zone, so that along all continents. Sandullers live in waters below the mean low tide line, on or just beneath the surface of sandy and muddy areas. The common sand daller can be found in the northern

hemisphere from the intertidal zone to the depths of the ocean, while the keyhole sandalers can be found on many a wide range of coasts in and around the Caribbean Sea. The spines On the somewhat flattened top side and underside of the animal, allow it to burrow or creeps through the sediment when looking for shelter or food. Fine hair-like cilia cover these tiny spines. Sandullers usually eat algae and organic matter found along the ocean floor. Those some species will tip on their side to catch organic matter floating in ocean currents. sanddollars frequently gather on the ocean floor, in part to their preference for soft bottom areas,

which are convenient for the reproduction. In 2008, biologists discovered that sand d'olar larvae will clone themselves for a few different reasons. When a predator is near, certain species of sand dollar larvae will split themselves in half, in a process they use to asexually clone themselves when sensing danger. The cloning process can take up to 24 hours and creates larvae that are two-thirds their original length, which can help conceal them from the predator. The larvae of these sandalers clone themselves

when they sense dissolved mucus from a predatory fish. The larvae exposed to this mucus from the predatory fish respond to the thread by cloning themselves. This process doubles their population and halves their size, which allows them to better escape detection by their predatory fish, but may make them more vulnerable to attacks from smaller predators like crustaceans. Sandullers will also clone themselves during normal asexual reproduction. will undergo this process when food is plentiful or temperature conditions are optimal.

Cloning may also occur to make use of the tissues that are normally lost during metamorphosis. The flattened test of the sand duller allows it to burrow into the sand and remain hidden from sight from potential predators. Predators of the sand daller are the fish species cod, flounder, sheep's head, and haddock. and headache. These fish will prey on sandullers even through their tough exterior. Sandullers have spines on their bodies that help them to move around the ocean floor. When a sand duller dies, it loses the spines and becomes smooth as the exoskeleton is then exposed. Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, animals, fungi, and bacteria.

External symmetry can be easily seen by just looking at an organism. For example, the face of a human being has a plane of symmetry down its center, or a pine cone displays a clear symmetrical spiral pattern. Internal features can also show symmetry, for example, the tubes in the human body responsible for transporting gases, nutrients, and waste products, which are cylindrical and have several planes of symmetry. Biological symmetry can be thought of as a balanced distribution of duplicate body parts or shapes within the body of an organism. Importantly, unlike in mathematics, symmetry and biology is always

approximate. For example, plant leaves, while considered symmetrical, rare match up exactly when folded in half. Symmetry is one class of patterns in nature, whereby there is a near repetition of the pattern element, either by reflection or rotation. While sponges and placazons represent two groups of animals which do not show any symmetry, i.e. are asymmetrical. The body plans of most multicellular organisms exhibit and are defined by some form of symmetry.

There are only a few types of symmetry which are possible in body plans. These are radial, cylindrical symmetry, bilateral, bi-radial, and spherical symmetry. While the classification of viruses as an organism remains controversial, Viruses also contain icosahedral symmetry. The importance of symmetry is illustrated by the fact that groups of animals have traditionally been defined by this feature in taxonomic groupings. The radiatta, animals with radial symmetry, formed one of the four branches of Georges-Cuvier's classification of the animal kingdom. Meanwhile, Bilateria is a taxonomic grouping, stills. use today to represent organisms with embryonic bilateral symmetry.

Organisms with radial symmetry show a repeating pattern around a central axis, such that they can be separated into several identical pieces when cut through the central point, much like pieces of a pie. Typically, this involves repeating a body part, four, five, six, or eight times around the axis, referred to as ten times. tetramarism, pentamerism, hexamerism, and octomerism, respectively. Such organisms exhibit no left or right sides, but do have a top and a bottom surface, or a front and a back. George Cuvier classified animals with a radial symmetry in the taxon radiata,

which is now generally accepted to be an assemblage of different animal phyla that do not share a single common ancestor, a polyphaletic group. Most radially symmetric animals are symmetrical about an axis extending from the center of the oral surface, which contains the mouth to the center of the opposite end. Three-fold triridial symmetry was present in trilobozoa from the late Ediacron period. Fourfold detramarism appears in some jellyfish, such as Aurelia marginalis. Flowering plants show five-fold pentamerism

in many of their flowers and fruits. This is easily seen through the arrangement of five carpels, seed pockets in an apple, when cut transversely. Among animals only the echinoderms, such as sea stars, sea urchins and sea lilies, are pentamerous as adults. with five arms arranged around the mouth. Being bilaterian animals, however,

they initially develop with mirror symmetry as larvae, then gain pentaradial symmetry later. Hexamerism is found in the corals and sea anemones, which are divided into two groups based on their symmetry. The most common corals in the subclass hexacoralia have a hexameric body plant. Their polyps have six-fold internal symmetry and a number of tentacles that is a multiple of six. Octamerism is found in corals of the subclass octacoralia.

These have polyps with eight tentacles and octameric radial symmetry. The octopus, however, has bilateral symmetry, despite its eight arms. Icozahedral symmetry occurs in an organism which contains 60 subunits, generated by 20 faces, each an equilateral triangle, and 12 corners. Within the icosahedron, there is two-fold, three-fold, and five-fold symmetry. Many viruses, including canine parvovirus, show this form of symmetry due to the presence of an icosahedral virochel. shell, such symmetry is evolved because it allows the viral particle to be built up of repetitive subunits, consisting of a limited number of structural proteins, encoded by viral genes,

thereby saving space in the viral genome. The icosahedral symmetry can still be maintained with more than 60 subunits, but only in multiples of 60. For example, the T3 Tomato Bushy Stunt virus has 60 times 3 protein subunits, 180 copies of the same structural protein. Although these viruses are often referred to as spherical, they do not show true mathematical spherical symmetry. In the early 20th century, Ernst Heckel described Heckel, 1904,

a number of species of radialaria, some of whose skeletons are shaped like various regular polyhedra. Spherical symmetry is characterized by the ability to draw an endless line, or great but finite number of symmetry axes through the body. This means that the spherical symmetry occurs in an organism if it is able to be cut into two identical halves through any cut that runs through the organism's center. True spherical symmetry is not found in animal body plans. Organisms which show approximate spherical symmetry include the freshwater green alga vulvax. Bacteria are often referred to as having a spherical shape. Organisms with bilateral symmetry contain a single plane of symmetry, the sagittal plane, which divides the organism into two roughly mirror image left and right halves.

approximate reflectional symmetry. Animals with bilateral symmetry are classified into a large group called bilateria, which contains 99% of all animals. All bilaterians have some asymmetrical features. For example, the human heart and liver are positioned asymmetrically, despite the body having external bilateral symmetry. The bilateral symmetry of bilaterians is a complex trait, which develops due to the expression of many genes. The bilateria have two axes of polarity.

The first is an anterior-posterior-ap axis, which can be visualized as an imaginary axis running from the head or mouth to the tail or other end of an organism. The second is the dorsal ventral dv axis, which runs perpendicular to the AP axis. During development, the AP axis is always specified before the DV axis, which is known as the second embryonic axis. The AP axis is essential in defining the polarity of bilateria and allowing the development of a front and back to give the organism direction. The front end encounters the environment before the rest of the body, so sensory organs such as eyes tend to be clustered there.

This is also the site where a mouth develops, since it is the first part of the body to encounter food. Therefore, a distinct head with sense organs connected to a central nervous system tends to develop. This pattern of development with a distinct head and tail, is called cephalization. It is also argued that the development of an AP axis is important in locomotion. Bilateral symmetry gives the body an intrinsic direction

and allows streamlining to reduce drag. In addition to animals, the flowers of some plants also show bilateral symmetry. Such plants are referred to as zygomorphic and include the orchid and pea families. He families and most of the fig ward family. The leaves of the plants also commonly show approximate bilateral symmetry. Biradiosymmetry is found in organisms which show morphological features, internal or external, of both bilateral and radiosymmetry.

Unlike radially symmetrical organisms, which can be divided equally along many planes, Birradiol organisms can only be cut equally along two planes. This could represent an intermediate stage in the evolution of bilateral symmetry from a radially symmetric ancestor. The animal group with the most obvious biarradial symmetry is the tenophores. In tenophores, the two planes of symmetry are one, the plane of the tentacles and two, the plane of the pharynx. In addition to this group, evidence for biradio symmetry has even been found in the perfectly radial freshwater polyp hydra, a nadirium.

Biridial symmetry, especially when considering both internal and external features, is more common than originally accounted for. Like all the trades of organisms, symmetry, or indeed asymmetry, evolves due to an advantage to the organism, a process of natural selection. This involves changes in the frequency of symmetry-related genes throughout time. Early flowering plants had radially symmetric flowers, but since then many plants have evolved bilaterally symmetrical flowers. The evolution of bilateral symmetry is due to the expression of cycloidia genes,

Evidence for the role of the cycloidia gene family comes from mutations in these genes, which cause a reversion to radial symmetry. The cycloidia genes encode transcription factors, proteins which control the expression of other genes. This allows their expression to influence developmental pathways relating to symmetry. Symmetry is often selected for in the evolution of animals. This is unsurprising since asymmetry is often an indication of unfitness, either defects during development or injuries throughout a lifetime.

While symmetry is known to be under selection, the evolutionary history of different types of symmetry in animals is an area of extensive debate. Traditionally, it has been suggested that bilateral animals evolved from a radial ancestor, Naderians, a phylum containing animals with radial symmetry, are the most closely related group to the bilatarians. Nadarians are one of two groups of early animals considered to have defined structure, the second being the tenophores.

Tenophores show by radial symmetry leading to the suggestion that they represent an intermediate step in the evolution of bilateral symmetry from radial symmetry. Interpretations based only on morphology are not sufficient to explain the evolution of symmetry. Two different explanations are proposed for the different symmetries in Naderians and bilateria. The first suggestion is that an ancestral animal had no symmetry, was asymmetrical, before Naderians and bilaterians separated into different evolutionary lineages. Radial symmetry could have then evolved in nadarians and bilateral symmetry in bilaterians. Alternatively, the second suggestion is that an ancestor of nadarians and bilaterians

had bilateral symmetry before the nadirians evolved and became different by having radial symmetry. Both potential explanations are being explored and evidence continues to fuel the debate. Although asymmetry is typically associated with being unfit, some species have evolved to be asymmetrical as an important adaptation. Many members of the phylum porifera sponges have no symmetry, though some are radially symmetric. The presence of these asymmetrical features requires a process of symmetry breaking during development, both in plants and animals. Symmetry breaking occurs at several different levels in order to generate the anatomical asymmetry which we observe. These levels include asymmetric gene expression, protein expression, and activity of cells. For example, left-right asymmetry in mammals has been investigated extensively in the embryos of mice.

Such studies have led to support for the nodal form. In a region of the embryo referred to as the node, there are small hair-like structures that all rotate together in a particular direction. This creates a unidirectional flow of signaling molecules causing these signals to accumulate on one side of the embryo and not the other. This results in the activation of different developmental pathways on each side and subsequent Asymmetry. Fluxuating asymmetry, F.A. is a form of biological asymmetry, along with anti-symmetry and direction asymmetry.

Fluctuating asymmetry refers to small random deviations away from perfect bilateral symmetry. This deviation from perfection is sought to reflect the genetic and environmental pressures experience throughout development. with greater pressure resulting in higher levels of asymmetry. Examples of F.A. in the human body include unequal sizes, asymmetry, of bilateral features in the face and body, such as left and right eyes, ears, wrists, and thighs. Research has exposed multiple factors that are associated with F.A. As measuring F.A. can indicate developmental stability, and it can also suggest the genetic fitness of an individual.

Human physical health is also associated with F.A. For example, young men with greater F.A. report more medical conditions than those with lower levels of F.A. Multiple other factors can be linked to F.A., such as intelligence and personality traits. Since Sandellers have a velvet-like texture, I'm going to read a little bit about velvet. Velvet is a type of woven fabric with a dense, even pile that gives it a distinctive soft feel. Historically, velvet was typically made from silk.

Modern velvet can be made from silk, linen, cotton, wool, synthetic fibers, silk cotton blends, or synthetic natural fiber blends. Velvet is woven on a special loom that weaves two thicknesses of the material at the same time. The two layers are connected with an extra warp yarn that is woven over rods or wires. The two pieces are then cut apart to create the fabric's pile, and the two lengths of fabric are wound on separate take-up rolls. This complicated process meant that velvet was expensive to make before industrial power looms became available,

and well-made velvet remains a fairly costly fabric. Velvet is difficult to clean because of its pile, but modern dry cleaning methods make cleaning more feasible. Velvet pile is created by cutting the warp yarns, while they are made the work yarns, while velveteing pile is created by cutting the weft yarns. Velvet can be made from several different kinds of fibers, the most expensive of which is silk. Much of the velvet sold today as silk velvet is a blend of silk and another fiber, often rayon or cotton.

Velvet made entirely from silk is rare and usually has market prices of several hundred US dollars per yard. Cotton is also used to make velvet, though this often results in a less luxurious fabric. Velvet can also be made from fibers such as linen, mohair, and wool. A cloth made by the Cuba people of the Democratic Republic of Congo from the Rafi palm is often referred to as Cuba velvet. Modern velvet can be polyester, nylon, viscous, acetate, or blends of synthetics and natural fibers. For example, viscous mixed with silk produces a very soft, reflective fabric. A small percentage of spandex is sometimes added to give the final material a certain amount of stretch, hence stretch velvet.

velvet. Velvet has a thick pile and can be cut pile up or piled down for more shine or more saturated color.