Assignment:
Primary Literature Summary
Each student will write a short (250 to 300 word, excluding the classification and citation) summary of a paper from the primary scientific literature which focuses upon a particular invertebrate species. Below is a sample summary that will help you know how to approach this assignment.
Example Literature Summary
CLASSIFICATION
1) Ph. Arthropoda, SubPh. Crustacea, Cl. Malacostraca, SubCl. Eumalacostraca, SupOr. Peracarida, Or. Amphipoda, SubOr. Corophioidea, Fam. Ischyroceridae, Gen. Microjassa
SUMMARY OF PAPER
2) Conlan, K.E. 1995. Thumb evolution in the amphipod genus Microjassa Stebbing (Corophioidea:Ischyroceridae). Journal of Crustacean Biology 15:693-702.
3) Claws have evolved many times in the Crustacea, but how did they evolve from the jointed segments of a simple walking leg? The amphipod genus Microjassa helps us study claw evolution because claw form varies from thumbless in some species (simple clasping or subchelate) to fully thumbed in other species (truly claw-like or chelate).
4) Males use sexually dimorphic second gnathopods (claws) to grasp females prior to the molt when mating occurs. This phenomenon, called mate guarding, occurs in many crustacean species. In some species of Microjassa, the terminal leg segment (dactyl) simply folds tightly against the adjacent leg segment (propus) to form a hook-like clasping structure. In others, a rigid projection extends from the terminal end of the propus, forming a ‘thumb' against which the dactyl may close. This clasping structure looks surprisingly like the fully-developed claws of crabs and lobsters.
5) Conlan conducted a phylogenetic analysis of nine species, using 20 morphological characters. When gnathopod form was mapped onto her cladogram, she discovered a gradual evolutionary trend from unthumbed to fully-thumbed ‘claws'. The most derived species even had multiple thumbs!
6) Conlan concludes that the claw-like second gnathopods in male Microjassa evolved from simple clasping limbs by the gradual amplification of a rigid, thumb-like projection of the propus. This study illustrates nicely the value of cladistics analysis for inferring the history of morphological evolution and how a key morphological adaptation (claws) evolved via gradual transformation of a walking leg.
7) (240 words)
Permission to use this example and exercise was granted by Richard Palmer, Systematics and Evolution Group,
Department of Biological Sciences, University of Alberta
Readings:
Leaf Toughness Affects Leaf Harvesting
By The Leaf Cutter Ant, Atta cephalotes