Lab Activity 9.2
Biota 2: Invertebrates Found on Beachrock Surfaces

  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 found on beachrock surfaces.

Top  Instruction

Use the information below to fill out the checklist of the biota of beachrock 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 on top of beachrock at Playa Estacion, Puerto Penasco, Sonora, Mexico.

It should be used to complete lab activity 9.2.

 

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.

 

Eriphia squamata
"Lumpy-clawed Crab"
Phylum  Arthropoda
Class  Crustacea
Order   Decapoda
Family   Xanthidae
Morphology Its body (carapace) is usually 1-2 inches wide. It is mottled gray to green and its legs are banded with black.
Feeding Feeds at night. Forages for worms, algae and smaller crabs.
Defense Large claws that can pinch. Will defend its territory savagely. Hides during the day in holes or crevices.
Reproduction Males pass spermatophores to females during copulation. Females carry fertilized eggs under abdomenal flap. Hatchlings are zoea larvae that develop in the plankton.
Habitat Occurs in great numbers in the lower midintertidal zone of rocky shores.
Distribution Ranges from upper Gulf to Ecquador and Galapagos Islands.
Other One of the most common crabs - very territorial.

 

Tetraclita squamosa
"Thatched barnacle"
Phylum  Arthropoda
Class  Crustacea
Order   Thoracica
Family   Tetraclitidae
Morphology A large barnacle, 3/4 - 1 inch in diameter, conical, dull red to gray or white. May live singly or in large clumps. Uses a very strong "glue" to attach themselves to rocks.
Feeding Uses its feather-like feet to sweep through the water and trap small particles of food. It then retreats inside the shell to deposit the food into its mouth. Feeds on both plants and animals (omnivore).
Defense May close off its shell in case of predators or lack of water.
Reproduction Simultaneous, cross-copulating hermaphrodites. Hatchlings are nauplius larvae that develop in the plankton.
Habitat Common on exposed rocks in higher intertidal zones. May also be found on turtles, boat bottoms or other floating objects.
Distribution Puerto Penasco, Puertecitos, Gonzaga Bay and Los Angeles Bay.
Other Empty barnacle shells have a vital roll in the community by providing a protected place where smaller organisms may take refuge. "Glue" has been studied for possible application in denistry.

 

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.

 

Othilia tenuspina
"Black-tipped starfish"
Phylum  Echinodermata
Class  Asteroidea
Order   Spinulosa
Family   Echinasteridae
Morphology Brownish-gray with dark red-black tipped rays, the ventral side is yellowish-orange. On the rays are small spines.
Feeding They invert their stomachs, engulf their prey, and begin the digestion process while their stomach is still outside their body.
Defense A creamy fluid is secreted from pores in the rays when the animal is disturbed. 
Reproduction A synchronized release of sperm and eggs into the water. This is triggered by the previous release of a chemical substance, called a pheromone, into the water, signaling everyone to get ready for the "big day".
Habitat Found on rocks at the low tide level where there is some current.
Distribution Northern Gulf of California, sporadically in the southern Gulf
Other Can regenerate into a whole animal if at least 1 arm and 1/5 disk is present.

 

Polyclinum laxum
"Black, colonial tunicate"
Phylum  Chordata
Class  Ascidiacea
Order   Enterogena
Family   Polyclinidae
Morphology Generally forms a smooth, raised colony, dark brown to black, with yellow to white individuals arranged in oval or circular groups. Usually 5 - 10 cm across. Individually they are transparent, stiff, and are covered by a jellylike tunic.
Feeding Filter small particles from the water using a sticky, basket-like pharynx.
Defense Produce distasteful biochemicals
Reproduction Produce planktonic "tadpole" larvae that have chordate characteristics.
Habitat Live on the surfaces or undersides of rocks
Distribution Gulf of California
Other Common inhabitant of Puerto Penasco.



Lab Activity 9.2 Biota 1