Classification

 

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What does Aplysia dactylomela mean?

The genus name, Aplysia, has its origins in the greek word aplysia, which means "filth" or "an uncleanable sponge", referring to the nasty purple ink that the Spotted Sea Hare ejects (Scarborough 1992).

The specific epithet, dactylomela, is more challenging to define.  It must be broken into first its suffix, dactylo-, from the Greek word "daktulos", which literally means "finger-like" or "fingered" (MyWord 2007), and the suffix, -mela, a word of Latin / Greek origin which means "blackness" (Uhl 1997).

Thus, Aplysia dactylomela is defined as a filthy, uncleanable sponge with black finger-like projections on its body, which may refer to the two parapodia on its head, along with the dirty appearance created through the black rings which encompass its body.

 

Taxonomic Classification

 

Jump To Section:    Domain  -  Major Eukaryotic Clade  -  Kingdom  -  Phylum  -  Class  -  Order  -  Family  -  Genus  -  Species

 

Life Exists

Domain

Archaea

Eukarya

Bacteria

Major Eukaryotic Clade

SAR

Archaeplastida

Excavata

Opisthokonta

Amoebozoa

Kindom

Choanoflagellates

Animalia

Fungi

Diploblasts, Eumetazoa

Triploblasts, Bilateria

Protostomia

Lophotrochozoa

Trochozoa

Phylum

Deuterostomes

Ecdysozoa

Platyhelminthes

Annelida

Mollusca

Cnidaria

Porifera

Class

Cephalopoda

Bivalvia

Gastropoda

Polyplacophora

Order

Archaeogastropoda

Heterostropha

Anaspidea

Neogastropoda

Family

Akeridae

Aplysiidae

Notochidae

Genus

Aplysia

Species

Aplysia californica

Aplysia dactylomela

Aplysia brasiliana

Aplysia morio

 

 

 

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Taxonomic Level Descriptions

 

Eukarya

A. dactylomela belongs in the domain Eukarya because its cells contain true nuclei.  The sister domain to the Eukarya is the Archaea, and the sister taxon to the Eukarya and Archaea combined is the Bacteria (Campbell and Reece 2008).

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Opisthokonta

Second, the Spotted Sea Hare belongs to the major Eukaryotic clade Opisthokonta, which has the synapomorphy of a posterior- mounted flagellum (Campbell and Reece 2008).  Another organism in the Opisthokonta is the Beaver.

Domain						Eukarya
Major Eukaryotic Clade	SAR			Archaeplastida		Excavata		Opisthokonta		Amoebozoa

Sister to the Opisthokonta are the Amoebozoa, consisting of the kingdoms of the lobose amoebae, cellular slime molds, and plasmodial slime molds.  An example is the Slime Mold.  The Amoebozoa has the synapomorphy of having pseudopodia.  Closest related to these taxa are the Excavata, characterized by excavated feeding grooves.  The Excavata contains the kingdoms of the diplomonads, parabasalids, and euglenids.  There are two sister taxa which, together, are sister taxa themselves with the excavata: the SAR and Archaeplastida.  The SAR (Stramenopila, Alveolata, and Rhizaria), have an extra plastid whose possible origin comes from endosymbiosis with a red alga.  Sister to the SAR is the Archaeplastida, which has undergone endosymbiosis with a cyanobacteria, giving members of this kingdom an extra plastid, and includes the Silver Maple (Campbell and Reece 2008).

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Animalia

Next, A. dactylomela is an animal (Kingdom Animalia) (Campbell and Reece 2008).  This means that it is multicellular, and ingests other animals to obtain nutrients (heterotrophic).  In Animalia, A. dactylomela is in many subgroups.  First, it has at least two germ layers, the endoderm and ectoderm, which places it in the diploblasts, and it has true tissues which are organized into germ layers, thus resulting in gastrulation, which places it in the Eumetazoa (Schulz n.d.).  Further, A. dactylomela has three germ layers and bilateral symmetry, taking it out of the possible Cnidarians and placing it with the triploblasts and in Bilateria.  Since the mouth of this organism develops from the blastopore of the gastrula and the mesoderm splits in two to form the coelem, A. dactylomela is a protostome (Protostomia) (Campbell and Reece 2008).  In addition, it has trochophore larva, which immediately places it in Lophotrochozoa and then Trochozoa (Speer 2000).

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Mollusca

Finally, the phylum.  A. dactylomela is an organism that has three main body parts: a muscular foot, a visceral mass, and a large mantle.  These characteristics, along with the fact that it is a coelomate, places A. dactylomela with the slugs, snails, octopuses, oysters, clams and squids in the phylum Mollusca (Campbell and Reece 2008).

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Gastropoda

During the embryonic development of A. dactylomela, the visceral mass rotates up to 180 degrees.  In fact, it rotates so much that the anus and mantle cavity end up above its head!  This is called torsion, a common characteristic of organisms in the class of the gastropods.  Also, A. dactylomela has a symmetrical body, a reduced or absent shell, a foot for locomotion, a radula, a large and flat muscular foot for crawling and a rounded or conical one-piece shell.  Its head is present and it is freshwater or terrestrial.  The A. dactylomela is a clear member of the Gastropoda (Campbell and Reece 2008, Marine n.d.(b)).

The Spotted Sea Hare is also a member of the Opisthobranchia, a subclass in the gastropods.  Organisms in this subclass are hermaphrodites, both marine and macroscopic, and don’t totally rely on a rigid external shell (Marine n.d.(c)).

Phylum			Mollusca
Class	Cephalopoda		Bivalvia		Gastropoda		Polyplacophora

There are four major classes in the phylum Mollusca.  The first is Cephalopoda, which consists of organisms such as squids, octopuses ( including the Giant Pacific Octopus ), cuttlefishes, and chambered nautiluses.  The only molluscs with a closed circulatory system, the cephalopods in general are also active predators, using their tentacles and modified foot to grasp and kill their prey (Campbell and Reece 2008).

The second class of Mollusca are the bivalves.  As their name implies, bivalves have a shell which is divided into two halves that are hinged together.  Mostly suspension feeders, Bivalvia consists of clams, mussels, scallops, and oysters (Campbell and Reece 2008).

Another class in the phylum Mollusca is the Polyplacophora.  The Polyplacophora consists of chitons, marine animals with an oval-shaped body covered by a eight-dorsal-plate shell (Campbell and Reece 2008).

Lastly, the fourth major class of the phylum Mollusca is Gastropoda, which is the class in which Aplysia dactylomela resides.  In short, gastropods are characterized by a developmental phenomenon called torsion, in which, during embryonic development, the visceral mass of the organism rotates up to 180 degrees (Campbell and Reece 2008).

Another organism in the phylum Gastropoda is Bithynia tentaculata.

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Anaspidea

Next is the order Anaspidea.  Members of the Anaspidea have tentacles (rhinophores) in the shape of rabbit ears, warts and other projections cover body in addition to a neck-like region behind head that merges into the plump trunk of the animal.  A. dactylomela exhibits each of these traits (Animal Diversity Web 2000).

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Aplysiidae

In the Anaspidea, there are only three families: the Akeridae, Aplysiidae and the Notorchidae.  Because of Aplysia dactylomela’s internal shell, elongated head, oral tentacles, rhinophoral tentacles, smooth mantle with both opaline (defensive gland with pearly fluid) and purple (defensive gland with purple dye) gland openings, reduced mantle cavity, parapodial lobes from an expanded foot and an enlarged radula, it belongs in the family Aplysiidae (Marine n.d.(e)).

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Aplysia

Placing the A. dactylomela into the correct genus is a fairly simple task, as there is only one genus in the family Aplysiidae: Aplysia (Marine n.d.(d)).

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Aplysia dactylomela

Since this organism shows a body and shell that are brown with light, black-lined spots on both the outside and inside of the parapodia, it has the specific epithet of dactylomela and thus its scientific name is Aplysia dactylomela (Marine n.d.(a)).

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