Sea Cave Fauna

Elliott, William R., Reddell, James R., Rudolph, D. Craig, Graening, G. O., Briggs, Thomas S., Ubick, Darrell, Aalbu, Rolf L., Krejca, Jean & Taylor, Steven J., 2017, The Cave Fauna of California, Proceedings of the California Academy of Sciences 64, pp. 1-311 : 25

Sea Cave Fauna

California’s sea caves sometimes have dark zones, and may contain many marine invertebrates and fishes that are attracted to dim light, darkness, or the shelter that crevices provide. California sea lions and harbor seals sometimes shelter in the caves ( Fig. 12 in the contiguous photographic section). A troglobitic isopod has been found in two caves.

Henderson (1983, 1988) described in detail the marine ecology of two caves on Santa Cruz Island. Diablo Anchorage Cave has two entrances and is subject to the prevailing, violent northwest swell, which enters the west entrance and exits the smaller east entrance, a blowhole. The cave is usually submerged and the bottom is floored with boulders, influencing the variety of invertebrates. The high flow of seawater and nutrients support filter feeders such as white sponge (Fig. 13), blue sponge, corals, barnacles, rock mussels, polychaete worms, and their predators, such as California spiny lobster. Resident fishes include rockfish, opaleye, perch, sheepshead, blacksmith, senioritas, spiny dog shark, and swell shark (scientific names are listed in Appendix 1). The two sharks are night or dim-light feeders especially attracted to this cave, forming tangled masses of many sharks.

Fry’s Harbor Cave has one entrance in the lee of Santa Cruz Island, calmer water than Diablo Anchorage Cave , less nutrient input, and a silty bottom with breakdown false floors creating upper and lower galleries. This environment attracts a different community. There are few lobsters, but many black abalone feeding on algal bits and kelp drifting in from the entrance. Green anemones grade from green near the entrance to translucent white with pink highlights, owing to a loss of symbiotic green algae in their tissues in the darkness. Commonly seen are giant rock scallops and nudibranchs, including a new species discovered there, Jorrunna pardus , the leopard spot nudibranch.

Two mainland sea caves, Brigadune Cave ( Cliff House Cave ) and Sutro Baths Cave ( Sutro’s Cave ), San Francisco County, contain an undescribed troglobitic terrestrial isopod, “Undetermined Oniscidea .” Cliff House Cave’s entrance is usually partly blocked with granitic beach sand and tree trunks. These are the only records of a troglobite from California sea caves .

A few caves on the Farallon Islands contain the troglophilic rhaphidophorid cricket, Farallonophilus cavernicolus , a genus unique to those islands. The cricket colonies are moderately large

(see Crickets overview below). The Farallon Islands were connected to the mainland during the low sea level stands in the late Pleistocene Epoch between about 25,000 and 15,000 ka and/or about 125,000 ka. Perhaps the crickets were distributed from the mainland to the present islands, and became isolated there relatively recently. The arboreal salamander, Aneides lugubris , is also known from sea caves on the Farallons and mainland caves (see Herpetofauna overview and Appendix 1).

Another troglophile, Brackenridgia heroldi (Fig. 14), may have originated from littoral environments; the Oniscidea were ultimately derived from marine ancestors (Broly et al. 2013). This terrestrial isopod, though blind and depigmented, was originally known from the seashore at San Mateo, San Mateo County, and up to 1,200 m in Muir Woods, Marin County, where it occurs in leaf litter and other organic debris. It is known from 39 terrestrial caves in eight counties from the Mojave Desert to Sierra Nevada North, but not from a sea cave. It was transplanted from McLean’s Cave to the Transplant Mine. Other species in the genus, all troglobitic, are known from Arizona , New Mexico, Texas, and eastern Mexico.

Figures

FIGURE 12 (top left). California sea lions huddle on a ledge in Painted Cave, a sea cave on Santa Cruz Island. DB. FIGURE 13 (top right). Sea cave life on Anacapa Island, Ventura Co.; white anemones and sponges have lost their mutualistic algae in the cave’s darkness. Image 25–30 cm wide. DB. FIGURE 14 (center left). Brackenridgia heroldi, 6 mm, Trichoniscidae, troglophile, Clough Cave. JK. FIGURE 15 (center right). Uroctonites sequoia, 4 cm, Vaejovidae, troglophilic scorpion, Clough Cave, Tulare Co., Sequoia National Park. JK. FIGURE 16 (bottom left). Uroctonus mordax scorpion, 5 cm, trogloxene, Clough Cave. JK. FIGURE 17 (bottom right). Hubbardia pentapeltis, about 5 mm, a male schizomid or short-tailed whipscorpion from southern California, similar to Hubbardia shoshonensis from Shoshone Cave. The male’s flagellum (tail) is sculpted, the female’s is simple. MH. Photographers: Dave Bunnell, Marshal Hedin, Jean Krejca.