Interesting Features IntroductionPelagia noctiluca belong to the Animalia kingdom. They belong to the Cnidaria Phylum and fall under the Scyphozoa class. Pelagia noctiluca have one of the most painful stings out of all jellyfish, and live in the open ocean across the Atlantic and the Mediterranean. Derived from the Latin word, pelagia means “of the sea”, nocti means night, and luca represents light; therefore, pelagia noctiluca is a seawater organism with the capability to light up or glow in the dark, as seen in figure 1.0. Phylum Cnidaria branch out into three major classes; Hydrozoans, Scyphozoans, and Anthozoans. Some of the organisms that are found in this Phylum are jellyfish, sea anemones, corals and hydras.
Cnidarian organisms are characterized by their radially symmetrical body plans. Rather than being bilaterally symmetric, like most other animal phyla, these organisms have a rounder symmetric shape. Cnidaria also possess three distinct tissue layers; outer protective epidermis, middle layer (Endoderm), and inner layer (gastrodermis) for digesting. Though these creatures do take in and digest food, they only contain one opening, covered by tentacles leading to an internal digestive cavity known as the gastrovascular cavity. These creatures lack internal organs and a central nervous system. Instead, their nerves are distributed in a net-like fashion that covers the whole body.
These organisms also lack muscle cells, making them slow and/or mostly motionless. Most Cnidarians have tentacles and nematocysts (specialized stinging cells). When in contact with prey, nematocysts use springing barbs that can inject toxins. This is how jellyfish kill their prey, anything that floats by, jellyfish sting and then consume. One hypothesis about the nematocysts origin is that they were prokaryotic endosymbionts that survived in eukaryotic cell bodies as mutualists.
Scyphozoa Containing approximately 200 species, Scyphozoans are a marine class of the phylum Cnidaria, also known as a true jellyfish. Scyphozoa Medusae grow to sizes bigger than those found among Hydrozoans. The sizes range from a couple centimetres to larger than 2two metres.
The nervous system of these creatures has developed further than many other Cnidarians; instead of a net, they posses a nerve ring circulating the rim of the bell portion of the medusa. This nerve ring helps jellyfish sense prey as well as danger. Jellyfish are carnivores, though they will eat plants and plant residue. Some Scyphozoans contain symbiotic dinoflagellates inside body tissues; they lie upside down in sunny patches and photosynthesize, receiving energy from carbohydrates fixed by algae. General Appearance and Body Plan Next, the pelagia noctiluca species are radially symmetrical creatures, their “umbrellas” range from 2cm to over 2m. As seen in figure 1.1, pelagia noctiluca have very distinct tissue layers, outer protective epidermis, the middle layer, endoderm and the inner layer, called the gastrodermis.
The mesoglea of cnidarians are not as highly developed as the mesoderm of other animal groups, being primarily gelatinous with only a few fibrous or amoeba-like cells (Cnidaria, 2016) . As displayed, they lack most organs and only have one body opening, acting as the mouth and anus. The outer and inner nerve rings also shown in figure 1.1 as well as sense organs on the outer part of the jellyfish. The umbrella, the most prominent feature, is divided into eight lobes, where sensory organs such as light receptors and odor pits are located.
The umbrella of a pelagia noctiluca is bell shaped or hemispherical. The bell exemplifies a frilled edge, eight thin stinging tentacles and four lobes hanging from the mouth, called oral arms. The colour of these organisms can range from purple-blue to brown-red. Pelagia noctiluca light up when disturbed, they appear to glow and may leave behind a luminous mucus. Evolutionary History Now, pelagia noctiluca have a long history of existence, dating back to before the Dinosaurs. There is evidence that this group is primitive, meaning they evolved before the evolution of bilateral symmetry. The oldest fossilized Cnidarians were soft-bodied. Fossils from the Cambrian Period (542- 488 million years old) have identified pelagia noctiluca as Cnidarian-related species.
Representatives of the four modern classes have been identified in Ediacaran Fauna of the Precambrian Period (between 542 and 635 million years ago.) Cnidarians are the earliest known mammals to have organized tissues – epidermis and gastrodermis and a nervous system. These organisms were also the first mammals to swim using muscle movement, rather than floating with the waves.
Jellyfish were the earliest animals to evolve muscle-powered swimming in the seas (Jellyfish Evolution, 2006). Since they have no bones/body parts, fossils are rare and quite hard to revitalize. The oldest ancestors of jellyfish can be traced back as long as 700 million years ago. The Conulariids, which existed from the Cambrian Period to the Triassic Period (251 million to 199.6 million years ago) are considered by some scientists to be skeletal remains of scypha polyps, either ancestral to the coronates or without modern derivatives ( Hand, C. H., & Fautin, D. G.
, 2017). Since then Jellyfish have further evolved by using a propulsion method to move and by using foraging strategies. As seen in Figure 1.
2, Meduzoanian ancestors have branched off to different sub-groups starting with the Cubomedusae. The timeline exemplifies the bell diameter and bell fineness throughout each jellyfish species. The data showcases how they have evolved as well as the movements each organism uses (jetting, rowing and mixed.) The Jellyfish are proof of evolution from one common ancestor, notice in the newer species, the bell diameter has shrunk and bell fineness as gotten larger, this indicates factors in the environment that have caused most of the newer species to adapt differently. Life Cycle Pelagia noctiluca have many stages throughout their life cycles. Pelagia noctiluca reproduce sexually and asexually, able to take on two different body forms. Adult jellyfish, known as a medusa, release eggs or sperm into the ocean through their mouth.
The type of fertilization can be external or internal. As seen in figure 1.3, an egg becomes fertilized, it then develops into a planula, another term for larvae. The planula then attaches itself to flower-like polyps and feed on plankton using their mouth and tentacles.
The polyps than reproduce asexually by budding into medusae, a full jellyfish form. From there, the jellyfish carries out all other life activities until it dies. Jellyfish are a form of plankton, which means that their delicate bodies have a hard time resisting currents in the ocean (The Importance of Jellyfish in the Ocean’s Food Chain, 2017). Therefore, Pelagia noctiluca are usually short lived, (2-4 months) they tend to die due to harsh waters and predators such as sea turtles. In captivity, pelagia noctiluca can live for up to 3 years.
Ecological Role Pelagia noctilucas main role in the environment today is to mainly maintain balance the delicate ocean’s ecosystem. Jellyfish have a direct effect on the food supply – many times they are prey for sea turtles, sunfish, spadefish, crabs, and scavengers on the ocean floor and even some larger mammals. Some people hunt and consume Jellyfish, primarily in Japan. Jellyfish prey on shrimp, plankton and other small organisms. Some of the positive impacts jellyfish have on the ecosystem are that they transport carbon to greater ocean depths, serve as a food source for many other organisms, enhance biodiversity and contribute to medical advances. Some of the negative effects this species may have on the environment are; adding millions in dollars to fishing and tourism businesses, interrupting power and freshwater production, and over-populatting, disrupting other resources. (Grabowski, M, 2018.) Deep sea organisms may avoid deceased Jellyfish because of jellyfish blooms, causing them to accumulate and undergo slow decomposition from microbes, depleting oxygen at the seafloor and depriving fish and scavengers of food resources.
Jellyfish blooms (swarms) are growing due to enrichment of nutrients and climate change; two human influences. Concern to Humans?Jellyfish have been labeled as a nuisance species, likened to that of wasps, cockroaches, and others, obscuring any understanding of their value (positive, neutral, or negative) in terms of ecosystem services, ( New Study Exploring Impacts and Benefits of Jellyfish, 2014.)Jellyfish have lately been tending to “bloom” or swarm highly populated waters, causing a negative impact on fishing and tourism industries, humans, and the environment. The sting of a Pelagia noctiluca is toxic to humans, causing whip-like scars across the body.
If allergic, anaphylactic shock can occur, this is obviously a huge problem to swimmers in highly jellyfish populated ocean waters. One possible use of their fluorescent protein is as a genetic marker to detect protein movement or gene expression in research in developmental, environmental and medical biology. (Manning 1997) This is a huge benefit to humans and the economic industry.
Pelagia noctiluca, among many other species of jellyfish, come in a wide variety of colour and sizes and have the ability to glow. The mucus jellyfish hold has the ability to power medical devices. Pelagia noctiluca have no brain, blood or central nervous system. Jellyfish are made up of mostly water, 95%. Jellyfish evolved before dinosaurs and have the ability to clone themselves. Jellyfish population rates are rapidly increasing, leading to a whole new environment in the ocean’s ecosystem. The movements of bell-shaped jellyfish have provided researchers with a new understanding of propulsion.
The flexibility of their umbrella-like bodies allow them to pulse upwards and downwards without expending much energy (Badore, M, 2018). Jellyfish have a lot to offer to research; in the way they move, produce and carryout life. For humans, jellyfish have both positive and negative effects. Hopefully in the future, scientist will learn more about jellyfish and put their benefits to scientific use, all while limiting the negative impacts of jellyfish on the environment.