• 1) CLASSIFICATION: Ph. Arthropoda, SubPh. Crustacea, Cl. Malacostraca, SubCl. Eumalacostraca, SupOr. Peracarida, Or. Amphipoda, SubOr. Corophioidea, Fam. Ischyroceridae

(TITLE & PRECIS OF PAPER: numbered items are explained below; they need NOT be numbered in your own reports)

• 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 they evolved from terminal leg segments is not always clear. Microjassa helps us understand claw evolution because claw form varies from thumbless (simple clasping) to fully thumbed (truly claw-like) among different species.

• 4) Males use sexually dimorphic second gnathopods to grasp females (mate guarding) prior to the molt when mating occurs. In some species, the terminal leg segment (dactyl) simply folds against the adjacent segment (propus) to form a clasping structure. In others, a rigid tubercle projects from the propus, forming a 'thumb' against which the dactyl may close. This clasping structure looks like the fully-developed claws of crabs and lobsters.

• 5) Conlan included 20 morphological characters for nine species in a cladistic analysis. Her cladogram revealed a gradual phylogenetic trend from unthumbed to fully-thumbed. The most derived species even had multiple thumbs! This tree also revealed that the oldest species were tropical, species of intermediate age evolved in cold-temperate waters, and the most recently evolved warm-temperate species derived from cold-temperate ancestors.

• 6) Conlan concludes: 1) that the claw-like second gnathopods in male Microjassa have evolved from simple clasping limbs by the gradual amplification of a rigid, thumb-like projection of the propus, and 2) that morphological diversification within the genus coincided with climatically-driven shifts in geographic range. This study illustrates nicely how cladistic analyses offer a powerful tool for inferring patterns of morphological and biogeographical evolution.

• 1) Classification (only needs to be done once, since all papers will deal with the biology of the same genus; this classification must include the family, order and all the appropriate taxanomic ranks above the level of order).

• 2) Full citation (author, year, title, journal, volume, pages)

• 3) Why did authors do the study?

• 4) Background information required to understand the significance of the study.

• 5) Summary of methods & results

• 6) Summary of general conclusions

-- Your final report should contain annotations for FOUR separate papers (two per page) all on the same genus of invertebrate.

-- You must submit a PHOTOCOPY OF THE ABSTRACT of each paper for which you do an annotation.

-- TOTAL LENGTH of each annotation (excluding the title) should not be more than 250 words; all four annotations must fit on two sides of a page.

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