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Lecture

Arthropods II and Hormones

4 Pages
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Department
Biology (Sci)
Course Code
BIOL 111
Professor
Irene Gregory- Eaves

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Description
25/10/11 Arthropods II Hormones = chemical messenger substance produced by endocrine system Ex. Termite behavior and morphology differences is induced by hormones released because of the environment and pheromone cues Diversity: 4 groups: 1. Myriapod: millipedes and centipedes 2. Chelicerates: spiders and mites and scorpions 3. Crustaceans: dominant marine environment 4. Hexapods: dominant in terrestrial environment, includes insects 1. Myriapods: countess feet 2 regions: head, trunk - Centipedes (chilopoda): - 1 pair of appendages per segment - Carnivores - less diverse - Millipedes (diplopoda - 2 pairs of app. Per segment - detritovores, herbivores - more diverse 2. Chelicerates: - have chilicerate (modified head appendage) Ex. Horseshoe crabs, pycnogonids, arachnids - No jaw (mandibles) - 2 body regions: cephalothoraxes – appendages, abdomen – no appendages - Pairs of appendages: 1. Chelicerae – fangs 2. Pedipalps – copulatory organs, pincers 3. Walking legs (4 pairs) 3. Crustaceans: Ex. crabs, daphnia, barnacles, etc… - Dominant marine arthropods in freshwater and terrestrial environment - Head + thorax or cephalothorax + abdomen - Appendages off each segment - Compose “zooplankton” important food source for fish 4. Hexapods: - largest groups - abundant in all enviros but deep sea - 3 body regions: - head: antennae, mouthparts - thorax: 3 pairs of walking legs maybe wings - abdomen: no appendages - non-insect hexapods have internal mouth parts 25/10/11 Insects: Unique to insects is their external mouthparts  huge diversity for consumption/feeding - herbivores, detritovores, fluid drinkers, predators, scavengers, parasites Flight: wings ~320mya a) ancestral multi-branched appendage b) in crayfish = gas exchange c) in drosophila = wings Wings have been secondarily lost in some species Respiratory system: - Insects and most myriapods: holes (spiracles) open into tubular tracheae which branch to finer tubes, carry O 2o body cells - Crustaceans: have gills - Chelicerates: have spiracles and trachea, book gills/book lungs - Book gills: in horseshe crabs: look like pages in a book - Book lungs: have similar structure but internally (in spiders, scorpions), protected for gas exchange prevent lungs from desiccating Open circulatory system: - Dorsal tubular heart (1 chamber) with pores (ostia) drives blood into hemocoael spaces - One-way valves Feeding: - Spend energy to acquire it: - Emergences: Insects responding to environment and making nearly faithful copies of themselves Ex. May fly emergence triggers: streams had low flow and hot temperature discovered in environmental survey - experiment: studied emergence by varying stream flow and temperature Sexual reproduction: - Most species are dioecous (sexes are separate) - lay eggs (exception: scorpion, holds eggs in female abdomen then babies sit on female back until 1 molt) - On land: Internal fertilization - some use spermatophoes = waterproof packets of sperm, when fertilization not completely internal - In Water: internal (crabs, only occurs right after molting) or external (barnacles) Daphnia life cycle: 25/10/11 - Parthenogenic cycle
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