Lab Activity 9.4
Biota 2: Invertebrates Found Under Boulders

  Directions

Study the instructional material below. Be sure to click on each of the photographs for an enlarged view in a separate window. The larger version is necessary to complete the assignment. It opens in a separate window which can be resized by grabbing the bottom right corner and dragging it. It can also be moved by grabbing the top heading bar and dragging it. Be sure to close the extra window by using the X in IBM, or the close box in MAC when you are finished using them.

  Introduction


In this lab activity you will study the invertebrates under boulders.

Top  Instruction

Use the information below to fill out the checklist of the biota of boulder microhabitats.

Be sure to write about what you are learning in the lab section of your notebook. You will be expected to answer questions about the lab activity during the lab self test and lab quiz. It helps to have your text and coloring books open beside you for support.

 
Supporting Information
Refer to the Assigned Readings Below:
Marine Biology Textbook none
Marine Biology Coloring Book none
 

This picture gallery summarizes the invertebrates found under boulders at Playa Estacion, Puerto Penasco, Sonora, Mexico.

It should be used to complete lab activity 9.4.

 

Geodia mesotriaena
"Fuzzy gray sponge"
Phylum  Porifera
Class  Demospongiae
Order   Choristida
Family   Geodiidae
Morphology Its color varies from white, gray, brown to purple on the outside and white or pale cream inside. The sponge spreads laterally into a massive cake, often forming very large colonies. Topped by leathery with many excurrent openings (oscula). A distinctive feature of this sponge is that the large pores(oscula) are restricted to sieve plates, which are leathery discs about 2-3 sm in diameter, with many openings. Its internal chambers shelter many other creatures including small porcelain crabs, brittle stars, and segmented worms.
Feeding Filter feeding
Defense Unpalatable
Reproduction Asexual budding and sexual spawning
Habitat Lives in the lowest tidal area under boulders.
Distribution From southern Alaska to the Gulf of California.
Other Predators are few including some nudibranchs and brittle stars. Its internal chambers shelter many other creatures including small porcelain crabs, brittle stars, and segmented worms.

 

Prosthiostomum multicelis
"Tan flatworm"
Phylum  Platyhelminthes
Class  Turbellaria
Order   Polycladida
Family   Prosthiostomidae
Morphology Body pale with a tan overcast and slightly yellow margins. Long, slender (to 30 mm) tapering to a bluntly pointed posterior.
Feeding Carnivorous on small invertebrates
Defense Ability to cling to the undersides of stones in very cramped quarters
Reproduction Cross copulating hermaphrodites
Habitat Undersides of rocks or within crevices or holes of reefs
Distribution Southern California to the Gulf of California
Other  

 

Thelepus nearsetosus
"Spagetti worm"
Phylum  Annelida
Class  Polychaeta
Order   Sedentaria
Family   Terrebellidae
Morphology Large body (to 150 mm long) divided into anterior thorax and posterior abdomen. There are three pairs of bushy gills and numerous thin tentacles near the head.
Feeding Use outstreched tentacles to feed on detrital particles on the surface.
Defense Can retract into a tube constructed of sand grains, bits of shell and mucus cement.
Reproduction Separte sexes and spawning
Habitat Among rocks and sand in the low intertidal and shallow subtidal.
Distribution Northern Gulf of California
Other  

 

Petrolisthes gracilis
"Slender rock slider"
Phylum  Arthropoda
Class  Crustacea
Order   Decapoda
Family   Porcellanidae
Morphology Small, very flat, bluish-green crab with white spots. Small, fifth pair of legs folded over the back edge of the body. The legs and body are relatively hairless.
Feeding Filter particles from water using the hair on their mouth parts
Defense Hard exoskeleton and ability to cling to the undersides of stones in very cramped quarters
Reproduction Separate sexes. Females brood eggs under their abdominal flaps until they hatch.
Habitat Found under stones.
Distribution From the upper Gulf of California and Bahia Magdalena to as far south as Bahia Tongola-Tangola, Mexico.
Other  

 

Petrolitshes hirtipes
"Fringed rock slider"
Phylum  Arthropoda
Class  Crustacea
Order   Decapoda
Family   Porcellanidae
Morphology Small, very flat, brown crab with small, fifth pair of legs folded over the back edge of the body. The legs all bear a long fringe of hair.
Feeding Filter particles from water using the hair on their legs and mouth parts
Defense Hard exoskeleton and ability to cling to the undersides of stones in very cramped quarters
Reproduction Separate sexes. Females brood eggs under their abdominal flaps until they hatch.
Habitat Common under stones and in crevices of reefs, coral and sponges in the lower intertidal.
Distribution Lower Pacific Baja and throughout the Gulf of California.
Other  

 

Clibanarius digueti
"Red-fingered hermit crab"
Phylum  Arthropoda
Class  Crustacea
Order   Decapoda
Family   Diogenidae
Morphology Red in appearance, has an unexplained olive color phase. Light speckling (blue) over the chelipeds and walking legs, antennaes are bright red to orange, carapace is tan to gray.
Feeding Filter feeders and scavengers
Defense Occupies the shell of a dead snail
Reproduction Separate sexes. Females brood eggs on pleopods until they hatch. April - September, the male gives a chase over a 12 hour period where the female is rotated, jiggled, tickled, and finally, seduced.
Habitat In the mid and upper intertidal zones, sandy short habitats with rock outcrops or shell debris, mangrove swamps, under boulders and rock surfaces.
Distribution Lower Pacific Baja and throughout the Gulf of California
Other Most common hermit crab of the Gulf of California. Gregarious at low tide forming clusters of up to 700 individuals. Disperse when the tide is changing.

 

Paguristes anahuacus
"Blue-eyed hermit crab"
Phylum  Arthropoda
Class  Crustacea
Order   Decapoda
Family   Diogenidae
Morphology Cream colored hermit crab with hairy, equal sized claws, and blue tipped antennae. Young have blue eyes.
Feeding Filter feeders and scavengers
Defense Occupies the shell of a dead snail
Reproduction Separate sexes. Females brood eggs on pleopods until they hatch.
Habitat Under boulders and on the surfaces of rocky shores in the lower intertidal, in tidepools and in the shallow subtidal
Distribution Gulf of California
Other Second most abundant rocky shore hermit crab in the Gulf of California. Gregarious.

 

Pilumnus townsendi
"Townsend's hairy crab"
Phylum  Arthropoda
Class  Crustacea
Order   Decapoda
Family   Xanthidae
Morphology Identified by four spines on the front outside edges of the body and spiny, hairy claws. Two different types of hairs on the purple body: one is long and stiff and the other is short and soft.
Feeding Scavengers who feed on floating food particles.
Defense Claws and hard exoskeleton and able to hide in small cavities
Reproduction Separate sexes. Females brood eggs on pleopods until they hatch.
Habitat Live under rocks and boulders; some prefer drainage channels in rocky areas where they have access to constant water.
Distribution Upper gulf to Bahia Manzanillo.
Other One of many hairy crabs living in the Gulf of California intertidal. Docile to handle, rarely large enough to pinch.

 

Tetragrapsis jouyi
"Square shore crab"
Phylum  Arthropoda
Class  Crustacea
Order   Decapoda
Family   Grapsidae
Morphology Small, dark, square bodied crab with equal sized claws and slender hairy legs.
Feeding Scavengers
Defense Claws and hard exoskeleton. Fast moving, cryptically colored and able to hide in small cavities
Reproduction Separate sexes. Females brood eggs on pleopods until they hatch.
Habitat Under rocks in sandy areas, sand and mud flats of the upper intertidal.
Distribution Gulf of California
Other  

 

Alpheus californiensis
"Snapping shrimp"
Phylum  Arthropoda
Class  Crustacea
Order   Decapoda
Family   Alpheidae
Morphology Colorful, fast, backwards swimming shrimp that are easily identified by their one large claw that is modified for making loud clicking or popping noises.
Feeding Snap large claw to stun prey. Use claw to grab small animals or morsels of food floating by.
Defense Hard shell on body (after molting, the body is soft. The shell hardens after a few hours, however, during that time they are vulnerable).
Reproduction Separate sexes. Females brood eggs on pleopods until they hatch.
Habitat Lives in tunnels under rocks in a sandy substrate.
Distribution Southern California to the Gulf of California, common at Puerto Penasco
Other If large claw is pulled off the other hand will develop a large claw.

 

Selenkothuria lubrica
"Sulfur cucumber"
Phylum  Echinodermata
Class  Holothuroidea
Order   Aspidochirota
Family   Holothruiidae
Morphology Maximum length of 15 cm, usually a sulfur-yellow color (tips of their feet), the base color ranges from gray-brown to purplish-black.
Feeding Plankton eaters.
Defense Will eject part of its stomach lining as a decoy when disturbed.
Reproduction Separate sexes and spawning
Habitat Under rocks in the lower mid intertidal zone in a cluster.
Distribution Ranges from upper Gulf of California to Ecuador and the Galapagos Islands.
Other  

 

Echinometra vanbrunti
"Purple sea urchin"
Phylum  Echinodermata
Class  Echinoidea
Order   Camarodonta
Family   Echinometridae
Morphology A dark purple urchin with long (one inch) slender spines.
Feeding Graze on algae
Defense The brittle spines may break off and cause puncture wounds that are very painful.
Reproduction Separate sexes and synchronous spawning
Habitat Intertidally on rocky substrate.Particularly in crevices and cavities in rocks and reefs, where it can avoid the full impact of the surf.
Distribution Northern Gulf of California to Peru and Galapagos Islands.
Other

 

Ophiocoma aethiops
"Black spiny brittlestar"
Phylum Echinodermata 
Class  Ophiuroidea
Order   Ophiurae
Family   Ophiocomidae
Morphology Largest and most striking brittle star, the arm spines are long and perpendicular to the arm axis. The aboral surface is purple-black. Diameter is 3.5 to 19.5 inches.
Feeding Opportunistic feeder that does eat carrion.
Defense Have break-away arms that they can regenerate. Seek darkness remaining under rocks during the day.
Reproduction Separate sexes and spawning.
Habitat Common on rocky shores, under rocks or in crevices of the lower mid intertidal zone.
Distribution East Pacific region, upper Gulf to Panama and the Galapagos Islands.
Other  

 

Ophiocoma alexandri
"Alexander's spiny brittlestar"
Phylum  Echinodermata
Class  Ophiuroidea
Order   Ophiurae
Family   Ophiocamidae
Morphology Large brittle star. Arm spines are perpendicular to the arm axis, arms are banded with gray and white. The disk is light brown or pale green, usually with a white blotch at the base of the arm spine. Diameter is 3.5 to 17.5 inches.
Feeding Opportunistic feeder
Defense Have break-away arms that they can regenerate. Seek darkness remaining under rocks during the day.
Reproduction Separate sexes and spawning.
Habitat Common in the rocky low to mid intertidal.
Distribution From the upper Gulf to Panama and the Galapagos Islands even to the Caribbean region.
Other  

 

Ophionereis annulata
"Ringed brittlestar"
Phylum  Echinodermata
Class  Ophiuroidea
Order   Ophiurae
Family   Ophiochitonidae
Morphology Small to medium-sized species of brittle star, arm spines perpendicular to the arm axis. Black and white in color. Diameter is 3 to 12.5 inches.
Feeding Filters particles from the water using its arms
Defense Have break-away arms that they can regenerate. Seek darkness remaining under rocks during the day.
Reproduction Separate sexes and spawning.
Habitat Found in the midtidal zone and occasionally in the low intertidal.
Distribution Ranges from southern California and the upper Gulf to Ecuador and the Galapagos Islands.
Other  

 

Heliaster kubinijii

"Gulf sun star"
Phylum  Echinodermata
Class  Asteroidea
Order   Forcipulata
Family   Heliasteridae

Morphology A pinkish-lavender seastar with black and green mottling, and 19 to 25 rays (starts life with 5 but adds rays as it matures). Diameter is 2.5 to 8 inches.
Feeding An indiscriminate top carnivore that prefers barnacles and small bivalves but will eat snails, chitons, small crabs and other invertebrates.
Defense Tough, spiny skin.
Reproduction Separate sexes and spawning. Spawn in early spring.
Habitat On and under rocks in the intertidal
Distribution Baja California, throughout the Gulf of California, south to Nicaragua
Other The most common starfish in the Gulf of California until 1978 when a massive die off occurred. The Gulf sun star has since made a come back but is still relatively rare.

 

Aplidium sp.
"Sea pork"
Phylum  Chordata
Class  Ascidiacea
Order   Enterogona
Family   Polyclinidae
Morphology Large, fleshy colonies made up of subunits. Each subunit contains many individuals arranged radially around an excurrent pore and covered by a gelatinous tunic. The colony is smooth and firm to the touch and from pale to vivid orange in color.
Feeding Filter feeder. Each individual produces a ventilating current using a ciliated, sticky basket-like paharynx to strain particles from the water.
Defense Produces distasteful, poisonous chemicals
Reproduction Sexually produced tadpole larvae have all the characteristics of chordates and are somewhat fish-like. These settle and transform into sessile adults which bud to produce a colony.
Habitat Under rocks in the intertidal and on rock surfaces in the subtidal.
Distribution  
Other  

 



Lab Activity 9.4 Biota 1