Starfish don’t possess brains or blood, but they do possess eyes which allow them to observe their surroundings. Furthermore, starfish have the ability to regenerate their arms should an unwelcome guest appear unannouncedly.
Once fertilized eggs hatch into bipinnaria larva, the animal moves to the ocean floor where it undergoes metamorphosis into an adult form with radially symmetrical features.
Reproduction
Starfish are marine invertebrates with a central disc-shaped body encased by arms. Found throughout all oceans, starfish inhabit every habitat imaginable from rocky shores to sea grass beds, kelp beds and coral reefs – some species can even live 9,000 metres below the surface! Additionally, starfish possess amazing regeneration capabilities – some tropical varieties even forming new starfish from just an arm fragment!
Starfish may look familiar, but they actually belong to a different subclass than fish: Echinoderms. Starfish fall under this subgroup, more closely related to sea cucumbers, sea urchins and sand dollars than to other fish species. Just like these other echinoderms, starfish lack internal skeletons but instead rely on calcium carbonate plates covered with spines and granules for rigidity – an adaptation that gives starfish some defensive capabilities as well.
Starfish lifespan depends on their species; typically it ranges between 10 and 34 years. Starfish have reproductive capabilities both sexually and asexually depending on the species they belong to; some even change gender during their lives! They move around using small legs located on their arms while adhering to surfaces using suction cups located there as well.
Starfish typically feature five arms, but there are species with 6, 12, or even 50 arms! Their length varies, from mottled starfish with their long gangly arms, to sunflower stars with shorter more symmetrical ones such as those found in sunflower fields. Their distinctive star shape comes from their radial symmetry; making them great ocean dwellers capable of living both cold and warm waters as well as shallow depths or even on sandy seabeds.
Benthic predators such as oysters are opportunistic predators that feed on benthic invertebrates and algae, using their tube feet to pry open clams or oysters before devouring their contents with their tube feet before withdrawing them back into their bodies and eating again. When digesting, their heart-shaped cardiac stomach will eject out through their mouth to process all this food before withdrawing it back into their bodies once finished digesting.
Feeding
Starfish (sometimes known as sea stars) are invertebrates with hard, spiny skin belonging to the Echinodermata phylum, alongside other familiar sea creatures like sea cucumbers and urchins. Like most Echinodermata organisms, starfish possess five-part radial symmetry; each arm extends outward from a central disc. Starfish feed on soft animals covered by shells made of calcium carbonate such as mussels or clams covered by hard shells made of calcium carbonate shells using suckers similar to those used by an octopus’ suckers on tube feet in order to open shells before devouring it using various digestive enzymes which break it down and digest its food before feeding it back onto another hard shelled animal covered in calcium carbonate shell.
Starfish cannot defend themselves and are often preyed upon by crabs, sea urchins, marine birds and sharks. Additionally, starfish are susceptible to pollution and disease and any starfish washed up onto shore may quickly die of dehydration before becoming food for land dwelling animals such as crabs.
One of the more fascinating characteristics of starfishes is their remarkable ability to regrow lost limbs; although this process may take up to one year. A research team at Queen Mary University of London discovered that certain neuropeptides help trigger stomach relaxation and retractions that allow starfishes to retract and inhales food.
Researchers conducted experiments with captive starfish, such as counting their rings on their skin and analyzing digestive processes. The experimenters noticed that starfish in deep waters had shorter intervals between rings than their shallower water counterparts, suggesting slower growth rates due to food availability or other environmental conditions.
Starfish use their arms to form fan-shaped feeding methods and move along the ocean floor, catching small fish and crustaceans. Their stomach has two sections – cardiac and pyloric. Once their prey has been caught, the starfish pushes its cardiac stomach out through its mouth into the food before digestive enzymes are released to break it down further before passing to their pyloric stomach for digestion and absorption of essential nutrients.
Movement
Though most are familiar with starfishes’ five arms and how they cling to rocks during low tide, few know that these voracious predators scour the seafloor looking for prey – moving body parts as necessary if necessary – and even using any one of their hundreds of “claws” (fins). The estimated 2,000+ species of sea stars all possess special symmetry that allows them to move in any direction led by any one of their hundreds of “fins”.
Starfish have highly sensitive tube feet at the tips of each arm that, through a series of contraction and relaxation procedures, enable it to wiggle its way across a substrate. But how does it know when it should make its next move? Unlike other echinoderms, starfish lack a central brain which sends signals for individual feet to move. Instead, each foot contains sensors which detect touch and smell changes in its environment – one such sensor being located inside each foot (the bulb inside each foot actually), that when contracted sends signals down an extension signal which expands as it retracts back down when relaxed (retracting).
Scientists compared the movement rates of crown-of-thorns starfish (Acanthaster solaris) across three substrate types – sand, coral rubble and hard coral substrate – using generalized linear models to assess differences in mean and maximum displacement over 15 seconds intervals; they discovered that movement rate corresponded with overall diameter.
Scientists conducted studies to understand the relationship between substrate type and movement by testing each of three substrates against various characteristics of starfish such as mouth size, arm number and total body diameter. Furthermore, temperature and light were evaluated to ascertain any impacts they had on movement.
Researchers found that substrate type significantly affected the rate at which crown-of-thorns starfish moved across a substrate, with coral rubble being most affected due to being less compacted and therefore needing to cover a larger area per displacement. Temperature also played an influential role, as warmer temperatures allowed faster movement from crown-of-thorns starfish.
Regeneration
Starfish are known for their amazing ability to regrow damaged limbs after breaking them off, an amazing feat for marine animals with no brain. Scientists continue studying this phenomenon with hopes of learning ways to assist human patients regrow lost limbs.
Regenerative power of starfishes can be attributed to cells known as coelomocytes. Coelomocytes are responsible for moving to areas of injury first and performing numerous important functions including protecting internal environments from foreign materials, healing wounds, initiating restoration of missing structures and producing organelles and protein components that contribute to regeneration of their starfish hosts.
Male and female starfish use different techniques to reproduce: both produce eggs and sperm from their bodies, which then combine and fuse to form a zygote, developing into larva that feed on small planktonic organisms before eventually reaching radial symmetry before becoming an adult starfish.
Starfish come in various species that all live different lifespans; the average lifespan for starfish can reach 35 years; larger starfish tend to outlive smaller ones.
Starfish have incredible regenerative capabilities that enable them to endure for an incredibly long time, protecting against predators and aiding reproduction. Scientists have studied this aspect of starfish life to see how we could use its powers for medical treatments for humans.
Scientists have recently discovered three distinct patterns of regeneration in starfish. Unidirectional regeneration occurs if more than half of its body remains undamaged; disk-dependent bidirectional regeneration allows regeneration if part of its central disc remains present; while thirdly there is radial unidirectional regeneration which allows only distal arms to regenerate.