Introduction to Marine
Invertebrates
Ref: Lesson 18
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. 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
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 bodiesKnown as active filter feeders
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
Active filter feeder - Clams Wastes (CO2 & food) released through excurrent
siphon
Active pumping allows animal to counteract buoyancy of plankton
Geoduck Clam – “Gooey duck”
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
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=H
PhAGyDceLo
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
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
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
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
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