Halgerda graphica (Bill Rudman's Sea Slug Forum) is redescribed based on examination of two specimens; one collected in 1904 from Middle Harbour, Sydney, Australia, housed at the Australian Museum, Sydney, and another specimen collected in 1990, from Port Moorowie, near the type locality (Kangaroo Island, South Australia). The reproductive system is described and illustrated for the first time.
This species has frequently been misidentified due to having similar external morphology to other Halgerda species. A comparison is made to those species. Halgerda graphica has a unique combination of external and internal characters that confirm it as a distinct Halgerda species. The external characters include a “hieroglyphic” pattern of yellow and black markings on the notum, small, similar-size dark spots on the ventral surface ( Sea Slug Forum), a small, sparse, dark-colored gill and rhinophores with a white base, dark tip and a dark line on the posterior side. The external color variations of Halgerda dichromis Fahey and Gosliner, 1999, H. okinawa Carlson and Hoff, 2000 (Sea Slug Forum) and H. willeyi Eliot, 1904 (Sea Slug Forum) are also described, illustrated and compared to externally similar species.
It is the unique combination of external morphological characters such as the color and pattern on the notum, the structure and color of the gills and rhinophores that help to distinguish each species, although examination of internal morphology can confirm the identification.
Basedow and Hedley (1905) described the nudibranch Halgerda graphica from two specimens.
Fahey, S. J. and Gosliner, T. M. 2003. Redescription of Halgerda graphica Basedow and Hedley, 1905 with observations on external morphological variation within selected species of Halgerda (Mollusca, Nudibranchia) Proceedings of the California Academy of Sciences, 54:393-406
WEBMASTER'S NOTES: The paper in its entirety can be downloaded from the Academy. Just go to the IZG publications page and point and click! File is about 753 KB!
Photo courtesy of Terry Gosliner
Taxonomic text courtesy of Shireen Fahey
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