Marine Biology: Arthropods and Echinoderms

Arthropoda major characteristics

-3 tissue layers, bilateral symmetry, complet gut and coelom

-external shell of chitin and segmentation/joint appendages

-rigid skeleton is molted for growth

-larval stage is morphologically distinct from adult stage

-antennae with small taste receptors

-compound or simple eyes

Chelicerata (arthropoda)

Body has two major sections, one with 6 pairs of appendages where the first pair have chelicaerae (movable claws)

Chelicerata Xiphosura characteristics

-Atlantic horseshoe crab

-body covered with hard carapace

-females large than males

-breed during spring and summer

How do chelicerata xiphosura reproduce?

The males attach to the females and fertilize eggs where they are then laid in the sand (between 60,000 and 120,000 eggs)

Chelicerata Pycnogonida

-sea spiders

-common in shallow water

-consume soft bodied organisms

-8 walking legs

-absorb oxygen through legs and transfer through diffusion

Crustacea (arthropoda) characteristics

-2 pairs of antennae and specialized mouthpart appendages

-appendages on thorax

-posterior abdomen has appendages for swimming or respiration

-range of feeding adaptations

Crustacea Malocostraca Decapoda

-crabs

-external skeleton of chitin

-molt as they age

-10 legs where front two are claws for catching and crushing, fighting and communication

-SEXUAL DIMORPHISM: where males have larger claws than femals

The blue crabs

-Crustacea Malacostraca Decapoda

-olive green to blue shell

-two appendages that act as paddles to swim

-in Chesapeake bay

The Lobsters

-Crustacea Malacostraca Decapoda

-protective exoskeleton must molt to grow

-long bodies

-live in crevices/burrow

-the first second and third pair of legs are claws

Crustacea Malacostraca Stomatopoda

-mantis shrimp

-burrow

-2nd pair of appendages are for combat and predation

-spearing (soft sediment)

-smashing (hard substrate)

-complex eyes

Crustacea Theocostraca

-exclusively marine

-encrusts self onto living or non-living surfaces

-secrete fast drying cement

-encased in calcium plates

-sessile filter feeders

-feed with cirri (feather appendages) which close with threat

-(barnacles)

Echinodermata

-3 tissue layers

-blind or complete gut

-circulatory system opens to coelomic cavity

-nerve ring; no brain

-excrete through diffusion

What are the main features of Echinodermata

Spiny skin enclosed in internal skeleton of interlocking calcium carbonate plates. Feeding and locomotion on tube feet connected to water vascular system (sea stars, sea cucumbers, and sea urchins)

What is the water vascular system of Echinodermata?

-water exchanged across dorsal sleeve (madreporite)

-combine with action of relief valves, movement of water increases suction in canal system

-uses 1,000 tube feed to apply suction and secrete mucus

-used for locomotion or food

Echinodermata asteroidea

-true starfish

-coastal ecosystems

-prey on sessile or slow moving organisms (mollusks, barnacles)

-has central disc and 5 arms

-reproduces sexually or asexually

-asexual reproduction through central disc fission and regeneration

-feeds by taking stomach out and digesting outside of body

Echinodermata echinoidea

-sea urchins, sand dollars, heart urchins

-covered in spines

-Aristotle’s lantern: jaw which scrapes algae, burrows in sand or feeds on sediment

Echinodermata crinoidea

-sea lilies and feather stars

-cup shaped body with upward reaching arms that catch zooplankton on tube feet

-sea lilies attached to substrate with stalk (some move) but if not attached they swim

-tube feet covered in mucus to catch food

Echinodermata holothuroidea

-sea cucumbers

-crown of tentacles that feed on sediment or directed upward to feed on zooplankton

-5 rows of tube feet for locomotion

Echinodermata ophiuroidea

-brittle stars and basket stars

-central disc and flexible arms that move animal without use of tube feet

-basket stars stay in crevices and stretch out at night to catch zooplankton with tube feet

-brittle stars live in sediment of on surface. Suspension feeders, sediment eaters or carnivores