phylum ARTHROPODA

R. A. Davis
Professor of Biology and Geology
College of Mount St. Joseph
Cincinnati, Ohio, 45233-1670

The following are comments and other information relating to the arthropods and onychophorans. This compilation definitely is neither comprehensive or exhaustive. Thus, in addition to the following, you should study as much other material related to the subjects mentioned as you "can get your hands on". To this end, toward the bottom of this WEB-page are listed some bibliographic references that might prove useful. There also is an ankyliography (a list of links) to web-sites that may contain some useful information.

If you have some suggestions as to how this WEB-page might be improved, please, contact me.

R. A. Davis
Professor of Biology and Geology
College of Mount St. Joseph
Cincinnati, Ohio, 45233-1670

Phylum Arthropoda is, by far, the most diverse phylum of kingdom Animalia. This, of course, is the result of a long and intricate evolutionary history. However, the authors of many biology text-books and laboratory-manuals do not seem to think that the phylum had any evolutionary history; at least, oftimes virtually nothing is said of extinct arthropods, including the trilobites, which were the most significant arthropods during the Paleozoic Era!

Phylum Onychophora includes worm-shaped animals that each bear numerous legs. They seem to be closely related to the Arthropoda. Indeed, some workers even consider them to belong in phylum Arthropoda.

The following is based on the classificatory schemes presented in various publications. However, it may not include all taxa listed therein, because we may not have specimens of all of them for you to study. The various schemes of classification do not always correspond with one another, nor does that presented below correspond exactly (and sometimes not even inexactly) with other classificatory schemes. Moreover, there is no doubt that the scheme presented below will be subject to considerable change in future years.

(Please, recall that botanists tend to use the taxonomic level "Division" for what zoölogists call "Phylum".)

examples: Cambarus, Homarus, Minippe, Orconectes, Pacifastacus, Panulirus, Procambarus

(The onychophorans seem to be closely related to the arthropods. Indeed, some workers even consider them to belong in phylum Arthropoda.)

Classes Chilopoda and Diplopoda sometimes have been included in a single class, the Myriapoda, and members of the classes commonly are referred to collectively as "myriapods".

Subphyla Crustacea and Uniramia sometimes have been referred to as belonging in a single taxon, the Mandibulata, and members of the subphyla sometimes are referred to collectively as mandibulates. On the other hand, some workers (for example, Margulis and Schwartz [1998, p. 268] use Mandibulata as a synonym for Uniramia.)

The term Entomostraca has been used for all crustaceans except the malocostracans.

genus	higher taxa
Acheta ("house-cricket")	Uniramia, Insecta, Orthoptera
Apis	Uniramia, Insecta, Hymenoptera
Argiope	Chelicerata, Arachnida, Araneae
Balanus ("acorn barnacle")	Crustacea, Cirripedia
Blaberus	Uniramia, Insecta, Orthoptera
Branchinecta	Crustacea, Branchiopoda, Anostraca
Cambarus	Crustacea, Malacostraca, Decapoda
Centuroides	Chelicerata, Arachnida, Scorpiones
Cyclops	Crustacea, Copepoda
Cypris	Crustacea, Ostracoda
Daphnia	Crustacea, Branchiopoda, Cladocera
Drosophila	Uniramia, Insecta, Diptera
Eubranchipus	Crustacea, Branchiopoda, Anostraca
Eutrombicula	Chelicerata, Arachnida, Acari, Prostigmata
Homarus	Crustacea, Malacostraca, Decapoda
Ixodes	Chelicerata, Arachnida, Acari
Julus	Uniramia, Diplopoda
Latrodectus	Chelicerata, Arachnida, Araneae
Lepas ("goose-neck barnacle")	Crustacea, Cirripedia
Limulus ("horse-shoe crab")	Chelicerata, Merostomata, Xiphosurida
Lithobius	Uniramia, Chilopoda
Minippe ("stone-crab")	Crustacea, Malacostraca, Decapoda
Orconectes	Crustacea, Malacostraca, Decapoda
Pacifastacus	Crustacea, Malacostraca, Decapoda
Panulirus	Crustacea, Malacostraca, Decapoda
Periplaneta	Uniramia, Insecta, Orthoptera
Procambarus	Crustacea, Malacostraca, Decapoda
Romalea ("lubber grasshopper")	Uniramia, Insecta, Orthoptera
Scolopendra	Uniramia, Chilopoda
Scutigera	Uniramia, Chilopoda
Spirobolus	Uniramia, Diplopoda

In order to understand this group of organisms, how they function, how they evolved, and so on, you will need to know a number of words, their definitions, and how and when to use the words. Thus, you should put together a list of such words, definitions, and notes. Here are some items to start you in compiling your own list.

Note that many terms in the material in this WEB-page have not been listed separately in this glossary. This does not mean that it would be a wise idea for you to ignore the terms in the material above.

(If a word you seek is not in the following, you might find it in the general glossary.)

Said of insects that undergo direct development (without metamorphosis) [cf.: hemimetabolous, holometabolous]

Said of insects that undergo incomplete metamorphosis [cf.: ametabolous, holometabolous]

Metamerism in which different metameres along the length of the animal's body differ from one another. The differences in the metameres may be the result of specialization of different metameres, the fusion of metameres, or a combination. The result is that different metameres or groups of metameres may perform different functions.

Said of insects that undergo complete metamorphosis [cf.: ametabolous, hemimetabolous]

A member of one of the classes Chilopoda and Diplopoda. In former years, it was common to include the centipedes and the millipedes in a single class called Myriapoda.

Subphyla Crustacea and Uniramia sometimes have been referred to as belonging in a single taxon, the Mandibulata, and members of the subphyla sometimes are referred to collectively as mandibulates. On the other hand, some workers (for example, Margulis and Schwartz [1998, p. 268] use Mandibulata as a synonym for Uniramia.)

One of the plates that make up a somite. [cf.: pleuron, somite, sternum, tergum]

One of the body-regions of an arthropod; formed by the fusion of metameres. [cf.: somite]

Abramoff, Peter, and Robert G. Thomson, 1994, Laboratory Outlines in Biology VI: W. H. Freeman and Company, New York, ix + 526 p., specifically, p. 317-323.

Barnes, Robert D., 1987, Invertebrate Zoology [fifth edition]: Saunders College Publishing, Philadelphia, ix + 893 p. ----- V.

Hickman, Cleveland P., jr., Frances M. Hickman, and Lee B. Kats, 2001, Laboratory Studies in Integrated Principles of Zoology (tenth edition): McGraw-Hill, Boston. xvi + 443 p., specifically, Exercise 13 ("The Chelicerate Arthropods", p. 203-209), Exercise 14 ("The Crustacean Arthropods", p. 211-224, and Exercise 15 ("The Uniramia Arthropods", p. 225-247).

Hickman, Cleveland P., jr., and Lee B. Kats, 2004, Laboratory Studies in Integrated Principles of Zoology (12th edition): McGraw-Hill, Boston, xiv + 434 p. (spiral-bound; ISBN 0-07-243994-0).

Hickman, Cleveland P., jr., Larry S. Roberts, and Allan Larson, 1997, Integrated Principles of Zoology (tenth edition): Wm. C. Brown, Dubuque, Iowa. xix + 901 p., specifically, chapters 19-21, p. 369-430.

Lytle, Charles F., 1996, General Zoology. Laboratory Guide (twelfth edition): Wm. C. Brown, Dubuque, Iowa, xvi + 368 p.

Lytle, Charles F., and John R. Meyer, 2005, General Zoology Laboratory Guide [fourteenth edition]: McGraw-Hill, Boston, xxiii + 372 p. [ISBN 0-07-234900-X; spiral-bound].

Oehler, Charles, 1974, The Medical Significance of Spiders at Cincinnati, Ohio: Journal of the Cincinnati Museum of Natural History, 23(3):1-11, + 7 pls. ----- V.

Margulis, Lynn, and Karlene V. Schwartz, 1998, Five Kingdoms. An Illustrated Guide to the Phyla of Life on Earth: W. H. Freeman and Company, New York, xx + 520 p.

Purves, William K., David Sadava, Gordon H. Orians, and H. Craig Heller, 2001, Life. The science of biology [sixth edition]: Sinauer Associates, Inc./W. H. Freeman and Company, specifically, Ch. 32 ("Ecdysozoans: The Moulting Animals", p. 564-576).

Rasnitsyn, Alexandr P., and Donald L. J. Quicke, 2001, History of Insects: Kluwer: Dordrecht, The Netherlands, 544 p.

Raven, Peter H., George B. Johnson, and Stuart Ira Fox, 1999, Biology [fifth edition]: WCB/McGraw-Hill, Boston, xxviii + 1284 p.

Raven, Peter H., George B. Johnson, Jonathan B. Losos, and Susan R. Singer, "2005" (actually in print in 2004!), Biology [seventh edition]: McGraw-Hill, Boston, xxiii + 1250 p., plus appendices, and so on. [ISBN 0-07-291845-4; hardbound].

Treatise on Invertebrate Paleontology. [various authors and dates, 1959 - present: Geological Society of America and University of Kansas Press:

Van De Graaff, and John L. Crawley, 1998, A Photographic Atlas for the Zoology Laboratory [third edition]: Morton Publishing Company, Englewood, Colorado, 185 p. ----- V.

Vodopich, Darrell S., and Randy Moore, 1999, Biology Laboratory Manual (fifth edition): WCB/McGraw-Hill, Boston. xi + 546 p., specifically, p. 391-403.

(Editorial note: The word "ankyliography" is analogous to the word "bibliography", but is derived from the Greek word "ankylion", which denotes a link in a chain [as opposed to "biblion", "book"].)

Dr. Scott A. Stockwell maintains a file of frequently asked questions and answers about scorpions. There are also links to other scorpion-related web-sites.

The About Lobsters web-page is actually about so-called "spiny lobsters" (as opposed to "Maine lobsters").

Here is a list of preserved material of the Arthropoda and Onychophora (including microscope slides) that is available in the Department of Biology.

There is no specific laboratory-exercise we are using in class. A number of the laboratory-manuals listed in the Bibliography contain exercises you might find useful to guide your study, as do other publications not listed.

One of the best ways to stimulate your observational skills is by making drawings of the specimens you examine. Moreover, drawings definitely help jog the memory, once the specimens themselves no longer are available. Hence, you should make drawings of all the specimens you study. These do not need to be equal to the renderings of a professional artist. However, each of your drawings should be well labelled, both as to what is shown and as to the parts and features thereof. There should be a scale on each drawing, of course. Accompanying each drawing should be notes of your observations of colours, changes over the time you observed the specimen, behaviour of the animal (if it was alive), and so on. Again, the goal is to stimulate your observational skills and your memory.

This web-page was constructed using MS-FrontPage and its version of html. The results have been previewed by way of MS Internet Explorer. Unfortunately, things that look fine when viewed with Internet Explorer sometimes look rather peculiar when viewed with Netscape. For example, there can be unexpected and unpredictable changes in the size, shape, style of type, or some combination of these. Moreover, sometimes different versions of Internet Explorer do not present the same web‑page in the same way; for example, hyphens in one version can mutate into empty rectangles in another. Alas!

9 March 2000; 26 February; 1 March 2001; 19, 20, and 26 February 2002; 13 March 2007; 08 and 14 October 2007; 15 July 2008

cf.	=	compare to (from the Latin "conferre", "to compare")
q.v.	=	see the entry for the previous word (from the Latin "quod vide", "which see")

TBC	=	citation incomplete or otherwise suspect; it definitely needs to be checked against the original.
V	=	verified with the original publication
[ ]	=	note / annotation
{ }	=	source of information