The M. W. Johnson’s phyllosoma slide collection goes digital
Dr. Martin W. Johnson (1893-1984) was an American oceanographer and plankton researcher who worked for 50 years at the Scripps Institution of Oceanography, University of California, San Diego (SIO). He is most famous for discovering the biological nature of the “deep scattering layer” (often called “false bottom”), and thus solved a mystery of great military implications in the detection of submarines and navigation. During the latter part of his career, and already in retirement, he devoted his time to one of his main research interests: the larval development of lobsters. He published numerous papers on the development of the large, leaf-like larvae of spiny lobsters (Palinuridae) and slipper lobsters (Scyllaridae), which are called “phyllosoma” (a term derived from the Greek words phyllon, leaf, and soma, body).
plankton. He subsequently went on to investigate the distribution and development of phyllosoma stages of various species of slipper lobsters such as Evibacus princeps (see photos).
Phyllosoma are unique among crustacean larvae in that they have a very long planktonic life, in some species over 1 year. They are unusually large, flattened, delicate, and transparent. After passing through several phyllosoma stages, the larva undergoes a molt and transforms into an immature lobster that now starts living on the sea floor and resembles the adult animal. Handling of these leaf-like larvae is difficult. To observe the anatomy of these larvae, Dr. Johnson prepared slides by staining them with Fast Green, run up through ethyl alcohols, and cleared in clove oil. The large larvae had to be mounted on a glass pane because they were much larger than the standard microscopic slides, and then flooded with Balsam or Clarite. Some of the mounted slides are as big as 8” x 10”.
Linsey Sala, a larval specialist from SIO Pelagic Invertebrates Collection who traveled to IZ to photograph and digitize the slides. This collaboration between SIO and IZ was supported by the Rathbun Fund for crustacean research.
To view the over 300 slides in this collection, visit the Invertebrate Zoology public database. Many of these images will soon also be available for viewing through the SIO Pelagic Invertebrates collection database.