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

(ANNOTATION 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 what is the sequence of intermediate forms by which they evolved from the jointed, terminal segments of a simple walking leg? The amphipod genus Microjassa helps us understand claw evolution because claw form varies from thumbless (simple clasping or subchelate) to fully thumbed (truly claw-like or chelate) among different species. (2 marks)

• 4) Males use sexually dimorphic second gnathopods to grasp females prior to the molt when mating occurs, a phenomenon known as mate guarding that occurs in many crustacean species. In some species of Microjassa, the terminal leg segment (dactyl) simply folds against the adjacent leg segment (propus) to form a lever-like clasping structure. In others, a rigid tubercle projects from the propus, forming a 'thumb' against which the dactyl may close. This clasping structure looks surprislingly like the fully-developed claws of crabs and lobsters. (2 marks)

• 5) Conlan included 20 morphological characters for nine species in a cladistic analysis. When gnathopod form was mapped onto her cladogram, this mapping revealed a gradual phylogenetic trend from unthumbed to fully-thumbed 'claws'. The most derived species even had multiple thumbs! (3 marks)

• 6) Conlan concludes 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. This study illustrates nicely how cladistic analyses offer a powerful tool for inferring patterns of morphological evolution and how a key morphological adaptation (claws) arose via gradual transformation of a walking leg. (3 marks)
  (248 words)

• 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 [all authors, year, full title of paper (no abbreviations), full journal title, volume, pages]; citation style should follow that used in one of the papers you chose.

• 3) Why did authors do the study? This should include a clear and simple question (stated in the form of a question) that identifies the general puzzle the paper attempts to solve (i.e., the broader relevance outside the paper; note- even the authors themselves may not do this well!).

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

• 5) Summary of main methods & results; include quantitative results where possible.

• 6) Summary of general conclusions including the answer to the question stated at the beginning.

-- Your final report should contain annotations for THREE separate papers all on the same genus of invertebrate, and a concluding section giving an summary and significance of all 3 annotations (100 words max., see lab guide for details).

-- You must submit a PHOTOCOPY OF THE ABSTRACT AND FIRST PAGE OF THE INTRODUCTION 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 three annotations, and the concluding summary, must fit on two sides of a page.

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