Where does Alpheus randalli fit in this spooky world?

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Domain: Eukarya
Alpheus randalli, or Randall’s Shrimp, is in the domain Eukarya for several reasons.  The first reason comes right from the name Eukarya.  Alpheus randalli has a true nucleus, as well as membrane bound organelles and multiple linear chromosomes in its cells.

Kingdom: Animalia
Just like all other members of this kingdom, Alpheus randalli is a multicellular, heterotrophic organism.  It also lacks cell walls and is mobile throughout its life.  

Phylum: Arthropoda
This phylum is characterized by having distinct head and trunk segments in their body plans.  They also have a complete exoskeleton made of a sugar polymer called chitin.  This provides structural support and protection because it covers the organism’s entire body.  All members of the Arthropoda phylum are ecdysozoans, meaning they grow by molting, which will be covered in more depth on the Reproduction page.  Another characteristic is jointed appendages that can only bend in one plane at each joint.  Multiple joints on each appendage with alternate angles allow the organism to move in any direction.  All of these characteristics can be found in Alpheus randalli.  Other Arthropods are the damselfly, water scorpion, ostracods, fireflies, and many other organisms. 

This phylogenetic tree shows the link between the phyla Arthropoda, which is where Alpheus randalli would be found, to the broadest of classifications, the domain Eukarya.  Follow the bold lines and names to trace Alpheus randalli’s lineage. 

Class: Malacostraca
Alpheus randalli fits into this class because it has two pairs of antennae.  Other members of this group include crabs, shrimp, lobsters, krill and pill bugs.   

Order: Decapoda
Members of the Decapoda class have three segments or tagmata; the head (or cephalon), thorax (or pereion), and abdomen (or pleon).  Each of these segments is then broken up into repeating segments called metameres.  The name Decapoda is broken down to “deca” meaning ten and “pod” meaning foot.  This name comes from the five pairs of walking legs called pereiopods on five of the thorax metameres.  There is an estimate 14,756 extant species of Decapoda.

Family: Alpheidae
The family Alpheidae is a family of shrimp with snapping claws, specialized body form, facultative and obligate symbioses with many animal groups, including gobiid fish, molluscs, sponges, cnidarians and other crustaceans, and have moderate orbital hoods.  The snapping claws are used for defense and aggression and will be discussed more in the Spooky Story page of this site.  Orbital hoods are extensions of the carapace that partially or completely cover the eyes of these shrimp.  Scientists believe that the orbital hoods are protection from combative claw snaps from other shrimp (Anker, et. al. 2006).  This family is also monophyletic, meaning it shares one common ancestor (Anker, et. al. 2006).   

    Another incredibly interesting shrimp with an adapted forearm for a special purpose is the Mantis Shrimp, click here to learn more!

    This tree represents the current hypothesis of the relationships between the families and superfamilies found in the infraorder Caridea.  This infraorder is found in the order Decapoda.  As you can see from the phylogeny pictured above, Alpheidae is one of the most derived families found in Caridea.  Once again, the bolded lines represent the family Alpheidae’s lineage and subsequently Alpheus randalli’s lineage.  Since phylogenies are always hypotheses, they are always subject to change.  This representation could change as we find more information on all of the families.

Genus: Alpheus
This genus is the largest and most complex decapod genus (Spence and Knowlton 2008).  Shrimp in this genus are asymmetrical with the major chela, the snapping claw, being much larger and more calcified than the other.  These shrimp tend to look more like mini-lobsters than typical shrimp.  This genus of shrimp is commonly called Pistol Shrimp (Anker, et. al. 2006).  


Species: Alpheus randalli
Alpheus randalli has wide red stripes with some spots over a base color of a clear transparent to white.  Alpheus randalli, or Randall’s Shrimp, was named after John E. Randall, who first collected this species of snapping shrimp on May 7, 1971.  It was found living with an Amblyeleotris sp. of goby fish (Banner and Banner 1980).


    To read more about this symbiotic relationship between Alpheus randalli and the goby fish see the Interactions page.

But first, let's head to the Habitat page to learn where we can find these Pistol Shrimp.