Janolus anulatus Camacho-García & Gosliner, 2006
Janolus anulatus was formally described in 2006 by Yolanda Camacho-García and Terry Gosliner. However the first records of this species go back to May 1966, when the late Jim Lance found it at Windansea Reef in La Jolla (Lance, 1953-2001). Jim and colleagues also regularly found it at South Casa Reef (Hospital Point) in La Jolla, where on one low tide (June 10) during the strong 1983 El Niño, ace ‘brancher Jerry Jacobs found 18 specimens (Lance, 1953-2001).
Since then, Yolanda Camacho-García and Ali Hermosillo have documented J. anulatus from the Pacific coast of Costa Rica and Bahía de Banderas, Jalisco, Mexico, respectively.
With its spotted color pattern and papillate cerata, J. anulatus is strikingly different from J. barbarensis, J. fuscus, and J. sp. 2 of Behrens and Hermosillo (2005), the other three species of Janolus known from the northeastern Pacific Ocean. However, excepting the statement that J. anulatus “feeds on a brown bryozoan” (Behrens and Hermosillo, 2005), nothing has been recorded about the natural history of this species.
On 9 May 2012 Brenna Green and I were surveying the little intertidal reef at the east end of Carpinteria State Park for nudibranchs. At the end of two and a half hours on a calm and clear morning, we had found 132 individuals in 18 species, including a handful of Flabellina iodinea. A productive tide by any measure. As we were about to cross the small channel separating the reef from the beach, I mentioned to Brenna how I really wanted to someday find a couple of species I had never seen, but that Jim Lance had found many times in La Jolla, such as Janolus anulatus and Cuthona hamanni. I then stopped to look under one last ledge, spotted a couple more Hermissenda, and then noticed a grayish blob of a slug dangling out of the water from a small bushy bryozoan. I initially thought it might be a Dendronotus venustus, but as soon as we placed it in water, Brenna said, “No, something’s different about it.” I got out my hand lens, and was stunned to see the J. anulatus (14 mm long) pictured above, one of the two species I had mentioned literally 30 seconds earlier! Needless to say, I got pretty excited (so much so that I forgot to collect the slug’s substrate, which I routinely do I if I think it will provide new information on diet).
Back in the lab, I took images and then isolated the slug, hoping to obtain an egg mass. I also noticed in the vial a few tiny fecal pellets, so checked those for signs of potential prey, and saw that our specimen had been preying on a lightly calcified bryozoan, but the fragments were too broken up to identify to species. After seeing that nothing was known about the specific diet of J. anulatus, I decided that I needed to return to the ledge in Carpinteria to collect the colony on which I had found the slug.
So on 11 May I returned to the exact spot and collected what appeared to be the correct bryozoan colonies. Later that morning, back in the lab, I placed the slug on one of those colonies, in a small dish. The slug settled right in, and when I took a look under the dissecting scope, I was floored by the resemblance of the nudibranch to the bryozoan , and knew that that must be its prey based on the resemblance alone. This was confirmed as the slug began to feed, not leaving the bryozoan colony for days. The color pattern and papillate cerata of the slug provide a near perfect match for the branches of the bryozoan, right down to presence of the brown bodies in the older bryozoan zooids. Had the slug been under water on that day in Carpinteria, I doubt I ever would have seen it! The bryozoan turns out to be Synnotum aegyptiacum, a circum-tropical species.
In an added bonus, the slug laid multiple egg masses, which allowed me to document the development of its eggs into hatching planktotrophic larvae . In striking contrast to J. fuscus and J. barbarensis, J. anulatus encapsulates its embryos singly (why some nudibranchs pack in multiple eggs per capsule, and others only one, remains completely unknown).
My first Janolus anulatus, a range extension, and new information of diet and developmental mode - a good tide indeed.
Behrens, D. W. and A Hermosillo (2005) Eastern Pacific nudibranchs. Sea Challengers, Monterey, California
Camacho-García, Y. E. and T. M. Gosliner (2006) A new species of the zephyrinid nudibranch genus Janolus (Mollusca: Nudibranchia) from North America and Costa Rica. Revista de Biologia Tropical 54(4):1295-1305
Lance, J. R. (1953 – 2001) Field accounts of opisthobranchs from California. Department of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, California [unpublished field accounts in three binders]
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