Introduction to Marine Invertebrates Ref: Lesson 18

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