Image courtesy of Jan Kocian
Skyline, Fidalgo Island, Washington
Triopha catalinae (Cooper, 1863)
This white and orange nudibranch has earned its common name, the Clown Dorid. They are flamboyant bryozoan-feeders have a white to grey-tan body, with varying numbers of large conical or rounded orange dorsal tubercles. The orange to reddish rhinophores and gills are darker than the orange-colored tubercles. The frontal veil has 8-12 orange processes. Living animals can reach 70 to 80 mm in length.
Animals have been found, commonly at times, in the middle intertidal zone to 115 feet deep on kelp or rocky substrates on which grow their arborescent and encrusting bryozoan prey. It ranges from Alaska to El Tomatal, Baja California; it has been found in the Gulf of California at Bahía de los Ángeles (Bertsch & Aguilar Rosas, 1984 and 2016).
In the past several weeks, while diving on Whidbey Island, Washington, our colleague Jan Kocian has found and photographed a number of Triopha catalinae with their egg masses. This is especially notable, and presented here are the first photographs of the living animal with its egg mass in the field. Goddard (1984), reporting on his extensive studies of nudibranchs at Cape Arago, Oregon, noted that “I have never seen T. catalinae egg masses in the field. Egg masses laid in aquaria are large, pinkish-white, coiled ribbons laid on edge.”
These egg masses are Type A: “The egg mass is in the form of a ribbon attached along the length of one edge, capsules occurring throughout most of it. This is common amongst dorids, which whilst laying may grip the mass between foot and mangle edge tending to flatten it....This is probably not the sole cause of the flattened shape.” Type A is “usually coiled since the parent crawls in a spiral whilst laying its eggs, as described by Alder & Hancock” (Hurst, 1967: 256).
Dr. Anne Hurst (1967: 261) described the egg masses of Triopha catalinae (under the now-synonymized name Triopha carpenteri) 1967, black-and-white photo] she studied at Friday Harbor Laboratories: “Egg masses were laid in the laboratory only between April and June although specimens had been kept at all other times of the year. The white or cream ribbon is laid in a loose coil and its wavy free edge is considerably longer than the attached one....The ribbon is about 1.4 cm wide. Capsules are smooth-walled and may contain 1 or 2 eggs, those with 2 being larger and more oval, some being pointed at one end. Capsules with only 1 egg are more numerous, but in a few egg masses capsules with from 5 to 7 eggs were frequent.” The egg diameter ranges from 75-87 µm (Goddard, 2004: Table 1, page 1960).
Thompson (1961) classified the larval shells of Sacoglossa and Acoela into two groups: Shell-type 1. Spiral shells, normally forming 3/4 to 1 whorl only. Shell-type 2. Egg-shaped “inflated” shells. Based on information presented by Costello (1939) he considered this species (as T. carpenteri), to have larval shell Type 1, which was confirmed with Hurst’s (1967: Figure 24: 7) illustration of the veliger shell. Shell length at hatching ranged from 131-134 µm (Hurst, 1967; Goddard, 2004). There are no known photographs of the living veliger of Triopha catalinae.
This species illustrates very well the reasons that I became enamored with studying nudibranchs and other heterobranchs: they are beautiful and there is still lots to discover about their biodiversity and natural history. It is a science still being written (Bertsch, 2020).
Bertsch, Hans. 2020. A history of eastern Pacific marine heterobranch research. The Nautilus 134(2): 71-88.
Bertsch, Hans & Luis E. Aguilar Rosas. 1984. Range extensions of four species of nudibranchs along the Pacific Coast of Baja California, Mexico. The Nautilus 98(1): 9-11.
-----. 2016. Invertebrados Marinos del Noroeste de México / Marine Invertebrates of Northwest Mexico. Instituto de Investigaciones Oceanológicas, UABC, Ensenada, xxxii + 432 pp.
Costello, D. P. 1939. Some effects of centrifuging the eggs of nudibranchs. Journal of Experimental Zoology 80: 473-499.
Goddard, Jeffrey H. R. 1984. The opisthobranchs of Cape Arago, Oregon, with notes on their biology and a summary of benthic opisthobranchs known from Oregon. The Veliger 27(2): 143-163.
-----. 2004. Developmental mode in benthic opisthobranch molluscs from the northeast Pacific Ocean: feeding in a sea of plenty. Canadian Journal of Zoology 82: 1954-1968.
Hurst, Anne. 1967. The egg masses and veligers of thirty northeast Pacific opisthobranchs. The Veliger 9(3): 255-288.
Thompson, T. E. 1961. The importance of the larval shell in the classification of the Sacoglossa and the Acoela (Gastropoda Opisthobranchia). Proceedings of the Malacological Society of London 34(5): 233-238.