Review sheet 5
Biology 4900 – Behavior
James Adams and Kristen Sanders
Invertebrates -- Arthropods
Non Insect Arthropods
The classification of the phylum Arthropoda has been considered to contain 4-5
subphyla for a long time, though as time has passed, our understanding of the
relationships between these:
Trilobita (extinct)
Chelicerata -- this includes several different classes, including
Horseshoe Crabs, Arachnids (spiders, mites, ticks, scorpions), the unusual Sea
Spiders (Pycnogonida), and a bunch of other cool organisms.
Myriapoda -- this includes the well-known centipedes and millipedes, and
the less well known pauropods and symphylans.
Crustacea -- this large group includes a number of very well-known marine
organisms (crabs, shrimp, lobsters, barnacles), the widespread copepods, and the
aquatic/terrestrial isopods.
Hexapoda -- this is the insects, and the small soil-dwelling Protura,
Collembola and Diplura
Many earlier studies promoted the idea that hexapods were most closely related
to myriapods. However, the most recent studies involving molecular/DNA
comparisons suggest that hexapods are actually not only closely related to
crustaceans, but that the Crustacea are paraphyletic when hexapods are excluded
(see the link to "newest understanding of arthropod relationships" on my
website). The authors of the paper at the indicated link suggest that the
Crustacea and Hexapoda should be combined into the Pancrustacea.
Next, we’ll do a quick overview of mating systems, as this will apply not only
here, but in insects, other groups we’ve already talked about, and most
vertebrates. Important concepts
include: monogamy, polygamy
(polygyny, polyandry, and promiscuity), parthenogenesis
Chelicerates:
named for the pincher or fang-like mouthparts (chelicerae)
Many of these are predatory, and some are venomous, and we will look at
the feeding behaviors/predatory avoidance of several groups (sea spiders,
spiders [see pg. 271, box 8.1], scorpions, uropygids, camel spiders).
Additionally, we will look at spawning behavior/mating behavior in horseshoe
crabs and jumping spiders (also see pg. 270, and 333 [sexual suicide]). We’ll
further discuss mate guarding and male parental care in harvestmen
(daddy-longlegs, see pgs. 327 and 425), and different mating systems (polyandry
in pseudoscorpions boosting reproductive success in females, for instance, pg.
372). Some groups are also parasitic, like ticks.
Myriapods:
We will look at feeding behavior/predatory defense in both millipedes and
centipedes. Be aware that
millipedes are largely herbivorous or detritivorous, whereas centipedes are
active hunters, with large ones being able to kill vertebrates.
Crustaceans:
Crabs and lobsters are familiar to everyone – we’ll discuss these and the
freshwater crayfish as well. We will discuss a bit about mate signaling, and
fitness components indicated by claw size (see pg. 293); different morphs in
sponge isopod males (pg. 321); and (female defense) polygyny in marine amphipods
(pg. 381). We’ll also show prey capture videos for snapping (pistol) shrimp and
mantis “shrimp”, and then filter-feeding by barnacles. There are other groups of
crustaceans that include much smaller organisms (copepods, ostracods, decapods,
amphipods) that make up much of the zooplankton in the seas. In the terrestrial
environment, we can find terrestrial crabs, hermit crabs and isopods (woodlice –
pillbugs), though in all cases these species are found close to water or in
moist environments.