Systematic Zoology Field Trip Activity

Phylum Arthropoda

Activity # 8

Phylum Arthropoda (Gr. Arthron, joint, and pous, podos, foot) is the most extensive phylum in the animal kingdom, composed of more than three fourths of all known species. Approximately there are 900,000 known species of arthropods. Few arthropods exceed 60 cm in length, and most are far below this size. The largest is the Japanese crab Macrocheira which has approximately a 4 m span; the smallest is the parasitic wood worm mite Demodex, which is less than 0.1 mm long. Arthropods possess the following characteristics.

Bilaterally symmetrical; with metameric body divided into tagmata consisting of head and trunk; head, thorax and abdomen; or cephalothorax and abdomen.

Jointed appendages; primitively, one pair to each somite, but number often reduced and appendages often modified for specialized functions.

Arthropods are acoelomate protostomes with well developed organ systems.

They have a complex muscular system, with exoskeleton for attachment, striated muscles for rapid actions, smooth muscles for visceral organs; no cilia.

Reduced coelom in adult; most of the body cavity consists of homocoel (sinuses, or spaces, in the tissues) filled with blood.

Complete digestive system; mouthparts modified from appendages and adapted for different methods of feeding.

Open circulatory system, with dorsal contractile heart, arteries, and hemocoel.

Respiration by body surface, gills, tracheae, air tubes), or book lungs.

Paired excretory glands called coxal, antennal, or maxillary glands present in some, homologous to metameric, nephridial system of annelids; some with excretory organs, called malphigian tubules.

Nervous system of annelid plan, with dorsal brain connected by a ring around the gullet to a double nerve chain of ventral ganglia; fusion of ganglia in some species; well developed sensory organs

Sexes usually separate, with paired reproductive organs and ducts; usually internal fertilization; oviparous or ovoviviparous; often with metamorphosis; parthenogenesis in a few forms.

Subphylum Trilobitomorpha

Extinct trilobites, with body divided by longitudinal furrows into three lobes (an axial lobes flanked by lateral lobes) head, thorax, and abdomen distinct; appendages biramous (two branched)

Subphylum Chelicerata

Appendages include chelicerae and commonly pedipalps and four pairs of walking legs; body usually divided into cephalothorax (fused head and thorax) and abdomen; mandibles and antennae lacking.

Class Merostomata

Aquatic chelicerates characterized by a swordlike telson at the end of the body, five to six pairs of abdominal appendages modified as external gills and a cephalothorax bearing one pair of widely spaced compound eyes.

Subclass Eurypteridia: Extinct ‘Water Scorpions”

Subclass Xiphosurida: Horseshoe crabs

Class Pycnogonida: (“compact knee”) have lots of knees, but they seem more gangly than compact, since these animals are nearly all multijointed legs, with very little body. Ex. sea spiders

Class Arachnida: Scorpions, whip scorpions, pseudoscorpions, solpugids, opilionids, spiders, ticks, and mites. Four pair of legs; segmented or unsegmented abdomen with or without appendages and generally distinct from cephalothorax; respiration by gills, trachea, or book lungs; excretion by malpighian tubules or coxal gland ; dorsal bilobed brain connected to ventral ganglionic mass with nerves; simple eyes; chiefly oviparous ; no true metamorphosis. Ex. Argiope, Centruroides

Subphylum Crustacea

Mostly aquatic, with gills, exoskeleton hardened with calcium carbonate; have cephalothorax and abdomen; 10 pairs of jointed appendages; two pairs of antennae; mandibulate; primitive forms have nauplius larvae.

Brachiopods, copepods, ostracods, barnacles, isopods, amphipods, euphasids, shrimps, lobsters, hermit crabs, crabs, etc.

Subphylum Uniramia

Primitively terrestrial with tracheae and malphigian tubules; one pair of antennae; mandibulate; three pairs of walking legs as adults which give them comparatively short, compact body, preadaptive to taking to the air.

Class Chilipoda: Centipedes. Name means "100 legs". Dorsoventrally flattened body; each with 1 pair of legs per body segment, one pair of long antennae; oviparous . Ex. Cermatia, Lithobius, Geophilus

Class Symphyla: Garden centipedes. Slender ( 1 to 8 mm) with long; fliform antennae; body consisting of 15 to 22 segments with 10 to 12 pairs of legs; no eyes. Ex. Scutigerella

Class Diplopoda: Millipedes. Name means "1000 legs". Subcylindrical body; head with short antennae and simple eyes; body with variable somites; short legs; usually two pairs of legs to a somite; oviparous. Ex. Julus, Spirobolus

Class Pauropoda: Pauropods. Minute ( 1 to 1.5 mm); cylindrical body consisting of double segments and bearing9 to 10 pairs of legs; no eyes. Ex. Pauropus

Class Insecta: Insects. Body with distinct head, thorax, and abdomen; pair of antennae; mouthparts modified for different food habits; head of six fused somites; thorax of three somites; abdomen with variable number , usually 11 somites; thorax with two pairs of wings ( sometimes one pair or none) and three pairs of jointed legs; usually oviparous; gradual or abrupt metamorphosis.

Subphylum Mandibulata traditionally has included all arthropods having antennae and mandibles, but appears to be a polyphyletic grouping and so is replaced here by subphylum Crustacea and subphylum Uniramia.

Objectives

1. To be able to familiarize with the different representative species of this phylum.

2. To determine the generalized body plan of arthropods.

3. To classify different arthropods species.

Materials

Fresh specimens

Crab ( Male and Female)

Shrimps

Different representative species of arthropods

Procedure

1. Examine the external parts of the fresh specimens of crab and shrimps. Draw and label their

external parts. Give their taxonomic account and its common name.

2. Draw the different representative species of arthropods. Give their taxonomic account and its

common name.

Systematic Zoology Laboratory Activity

ACTIVITY # 8

PHYLUM ARTHROPODA

Name:________________________________________________Score:_________________

Course/Yr & Sec._________________________Group #________Date:__________________

Taxonomic Account

Phylum: Arthropoda

Class: Crustaecea

Order: Decapoda

Family: Penaeidae

Genus: Penaeus

Species: monodon

Scientific Name: Penaeus monodon

Common Name: Giant Tiger Prawn

External Parts: Crab Male

Taxonomic Account

Phylum:

Class:

Order:

Family

Genus:

Species:

Scientific Name:

Common Name:

Taxonomic Account

External Parts: Crab Female

Phylum:

Class:

Order:

Family

Genus:

Species:

Scientific Name:

Common Name: