Introduction to Marine Invertebrates Ref: Lesson 18 Introduction to Marine Invertebrates

Kingdom Animalia 97% of animals on Earth are invertebrates Except for insects, most are marine Exception is Phylum Chordata which contains both.

97% of animal species on Earth are invertebrates 97% of animal species on Earth are invertebrates. On Earth today, insects are the most numerous invertebrates. Many vertebrates are described as "fish", encompassing a large group of disparate classes or subphyla.

Structure and Function of Feeding in Invertebrates Found nearly everywhere in the ocean Majority speak their juvenile stages in the plankton community

Structure and Function of Feeding in Invertebrates As adults – attach to substrates Seafloor Inside self-created shells/skeletons Floating among plankton Crawling on seafloor Swimming within water column

Coral

Adult: much larger than juveniles Figure 1: One example of a complex life cycle in a marine invertebrate. In this case, a benthic adult brittlestar releases its gametes into the water column where fertilization occurs and development takes place over a period of days to weeks. During this period a planktonic larval stage develops which is morphologically dissimilar from the adult. Eventually the larva settles as a benthic juvenile and the cycle repeats itself in the next generation. This pattern is common among marine invertebrates and the size of the egg is positively correlated with parental investment and predicts the length of the developmental period. Note that the images are not to scale. The adult is many times larger than the egg, larval and juvenile stages Adult: much larger than juveniles

Niches Multiple body forms allow for invertebrates to take on many “jobs” in their ecosystem Each species occupies a different niche Ex: 2 species of fish might eat the same smaller fish species, but one hunts at night while the other hunts during the day

Ex: Barnacles

Morphology Important characteristic of how the organism carries out its niche is its structure In animals, it is termed anatomy Study of processes within its anatomy is called physiology

Body Plans Asymmetry – animal lacks symmetry Simplest animals Radial - arranged around a central axis so that each part extends from the center Tend to be sessile (immobile) Bilateral – has identical halves Best for mobile creatures

Evolution of Body Plans

Anatomy

Physiology of Starfish

Feeding Techniques 1) Filter feeding Great deal of food suspended in water column Plankton or remains of larger organisms

Feeding Techniques Many bivalves pump water through their bodies Known as active filter feeders

Bivalves pump water through incurrent siphon Bivalves have a characteristic muscular foot on bottom and siphon on top Bivalves pump water through incurrent siphon Feather-like gills are enlarged to gather oxygen and food Covered in cilia which beat to maintain constant water flow Cilia trap food and push towards digestive system Mouth, stomach, intestine, and anus Clams, common bivalve mollusks, look like simple organisms, but have complex organ systems. The structures you see in the diagram have different functions. For example, gills extract oxygen from the water, while the heart pumps blood carrying oxygen and other materials to the animal's other organs.

Active filter feeder - Clams Wastes (CO2 & food) released through excurrent siphon Active pumping allows animal to counteract buoyancy of plankton Clams, common bivalve mollusks, look like simple organisms, but have complex organ systems. The structures you see in the diagram have different functions. For example, gills extract oxygen from the water, while the heart pumps blood carrying oxygen and other materials to the animal's other organs.

Geoduck Clam – “Gooey duck” This large Geoduck Clam dug by divers near Discovery Bay of Washington State is often called a "gooyduck". It shows the large siphons that some bivalves have. Water is sucked in through the incurrent siphon, and then filtered by the gills before the water is expelled through the excurrent siphon

Suspension Feeding Type of filter feeding in which organisms do not create their own water currents Rely on movement of water to bring them food Ex: Crinoids Crinoids are also known as sea lilies. They look like flowers but are actually echinoderms. They use their feathery arms to suspension feed.

Suspension Feeders Members of Phylum Echinodermata are suspension feeders Lined with tube feet connected to animal’s water vascular system Sticky tube feet capture food particles Transfer food to mouth an digestive system https://www.youtube.com/watch?v=HPhAGyDceLo

3) Deposit Feeders Feed on detritus – remains of decomposing plants and animals on seafloor Sift through sediment for food particles Ex: Sea Cucumber

3) Deposit Feeders Uses modified feet around its mouth to scoop sand in Important to marine ecosystem to recycle nutrients Sea cucumbers have a slimy, rubbery texture. Delicacy in Asian countries, where they feel they benefit one’s health to reduce blood pressure. Tasteles so often prepared with flavorful ingredients.

3) Deposit Feeders Unique strategy for evading predators When threatened, permanently eject all internal organs through mouth or anus This is called evisceration Distracts predator so sea cucumber can escape Eventually organs grow back and its good as new https://www.youtube.com/watch?v=aCxKFc3XtJs

4) Herbivory Eat plants and algae (including seaweed, some of which are protists) Ex: Sea Urchin Will puncture your foot, some contain toxins

Sea Urchins Coordinate tube feet and spines to move slowly along seafloor and rocks Specialized organ called Aristotle’s Lantern – resembles ancient Greek lantern Urchin pushes 5 teeth through its mouth Scrapes pieces of kelp or algae

Aristotle’s Lantern The broken sea urchin in this photograph allows us to get a view of Aristotle's Lantern, a sharp structure used to bite off pieces of algae. Notice the five teeth made up of calcium carbonate that make up the structure. Recall that one of the characteristics of echinoderms is their five-part radial symmetry.

Urchins are major part of Sea Otter’s diet Urchins are major part of Sea Otter’s diet. Keeps the population in check

5) Predation Many invertebrates feed on other animals Predators that subsist almost solely on other animals are carnivores - Ex: Sandworm from Phylum Annelida - classic segmentation, crosswire rings

5) Predation Polychaetes that have fleshy extensions called parapodia bristles used for swimming or crawling powerful hook-like jaws to grab their prey