Aeolidia loui Kienberger, Carmona, Pola, Padula, Gosliner & Cervera, 2016

            During the past decade or so, DNA-based research from multiple laboratories (including those of Juan Lucas Cervera, Ángel Valdés and Terry Gosliner) has resulted in numerous taxonomic changes to the Heterobranch fauna of the eastern Pacific and elsewhere. The majority of these studies have re-examined species with wide or even disjunct distribution patterns, resulting in specimens from previously-identified species now considered species in their own right. This is a case in point.

            Aeolidia papillosa (Linnaeus, 1761) had traditionally been known as a single, wide-ranging species in the northern hemisphere and from Chile. Shallow water specimens from California were assigned to this species (Marcus, 1961; MacFarland, 1966), and deep water specimens were considered A. herculea Bergh, 1894, or A. papillosa herculea. Kienberger et al. (2016) have shown that these animals are actually part of a species complex of sibling species. The Chilean species is A. campbellii (Cunningham, 1871), and A. filomenae (Kienberger et al., 2016) occurs in the northeast Atlantic from Scotland to Portugal. The amphiboreal Aeolidia papillosa is restricted to the northern Atlantic and northern Pacific. In the northeast Pacific it ranges from Cook Inlet, Alaska, to Washington. Both A. herculea and the newly-named A. loui have papillate (or rugose) rhinophores; the other three species have smooth rhinophores. Aeolidia herculea has been reported from Kamtchatka (as the synonym A. grandis Volodchenko, 1941), and in California from the Farallon Islands, Monterey Bay (as the synonym A. farallonensis Gosliner & Behrens, 1996), and Santa Barbara Island (type locality; not Alaska; see Behrens, 2004: 26). Kienberger et al. (2016) reported the distribution of A. loui from Cape Arago, Oregon, to San Diego, California (type locality, Duxbury Reef, central California). Steve Gardner’s images in BOW 407 from La Jolla Shores are of A. loui.

            In our new book, Invertebrados Marinos del Noroeste de México / Marine Invertebrates from Northwest Mexico (Bertsch & Aguilar Rosas, 2016), we report southern range extensions of Aeolidia loui to Punta Baja, Baja California, and, Punta Norte, Isla de Cedros.

            The coloration of Aeolidia loui is rather variable, ranging from translucent white to bright orange or brown. There are opaque white marks on the dorsum; some may be covered with light-ochre or brown spots/flecks. Distinguishing this species from the other shallow water species of Aeolidia are the rugose, warty rhinophores, and the bristly, flattened cerata, which are broader at their base. Bertsch (1974) published the first SEMs 4A,4B,4C of the radula of this species (as A. papillosa). Aeolidia loui differs from its deep-water Californian congener by possessing a cleioproctic, not pleuroproctic, anus.