BRANCHIOPOD DIVERSITY IN SAN DIEGO COUNTY, CALIFORNIA, USA MARIE A SIMOVICH, Biology Department. University of San Diego, and San Diego Natural History Museum, San D iego , CA 921/0 MiCHAEL FUGATE, Biology Department. University of California. Riverside. CA 92521 1992 TRANSAOlONS OF THE WESTERN SEalON OF THE WILDLIFE SOCIETY 28:6-/4 Abstract: Branchiopod crustaceans (fairy, clam. and tadpole shrimp) are common faunal elements in ephemeral aquatic habitats. All arc adapted to the temporary presence of water and to specific sets of environmental parameters (e.g., salinity. temperature, pH). These organisms arc often overlooked due to the limited time they and their habitat exists. San Diego County provides a diversity ofephemeral habitats ranging from coastal vernal pools to desert playas. However. only one branchiopod species has previously been reported from the area . Our studies have revealed a diverse fauna of four specie s of fairy shrimp in three families , three species of clam shrimp in two families, and one species of tadpole shrim p. Two of the fairy shrimp have range s almost entirely restricted to San Diego County and are threatened with extinction due to habitat loss. The tremendous loss of temporary aquatic habitats obs. and D. Belk, pers . comm.). The Conchostraca and worldwide has increased interest both in their unique and Notostraca have not been recently reviewed but are highly endemic flora and fauna and in their conservation represented by at least eightand four species, respectively (Jain 1976. Holland 1978. Dimentrnan 1981. Holland (Wootton and Mattox 1958, Lynch 1966 , Sassaman and Jain 1981. Herbst 1982. Jain and Moyle 1984. Belk 1989, Ahl1991 , Sassaman 1991, unpubl. data). Fiveof and Eriksen 1990, Belk et al. 1991, Jeffries 1991, Shoup the seven endemic fairy shrimp have only recently been 1991). The loss of habitat poses a threat not only to the described., and due to urban and agricultural expansion species living in the pools, some ofwhich have potential most warrant consideration as threatened or endangered uses for humans for food (Cheatham 1984, Sorgeloos et (Eng et al. 1990). al. 1986, Mitchell 1991), but also to numerous species of San Diego County specifically has experienced a waterfowl that feed on temporary pool organisms (Krapu tremendous loss of habitat and the review of Eng et al. 1974, Swanson et al. 1974, Driver 1981, Miiller 1987, (1990) and the subsequent description ofa new endemic Shoup 1991). fairy shrimp (Fugate, in press) make obvious the lack of The branchiopods in the orders Anostraca (fairy information on the county'sbranchiopod fauna. Prior to shrimp and brine shrimp), Conchostraca (clam shrimp) this study, only one branchiopod species was reported and Notostraca (tadpole shrimp) are often the dominant from San Diego County (Balko and Ebert 1984, Ebert fauna ofthe early successional stages of ephemeral water and Balko 1987, Eng et a:r 1990). Due to the diversity (Sublette and Sublette 1967, Ebert and Balko 1984, of habitats in the county, it was thought more species Dodson 1987) and have been used extensively for might be present. The present paper presents information aquaculture (Belk et al. 1991). Many branchiopods have on the distribution and biology ofbranchiopods from San specific habitat requirements (e.g., temperature, pH, Diego County. alkalinity, etc .) (Shantz 1905, Prophet 1963, Procter 1%4, Horne 1967, Moore 1967,Broch 1969, McCarraher STUDY AREA 1970, Brown and Carplan 1971, Hillyard and Vinegar Eng et al . (1990) divided California into eight 1972, Alexander 1976, Belk 1977a, Moore 1979, Donald regions, two of which are represented in San Diego 1983, Thiery 1987, Brach 1989, Eng et al. 1990 ). Due County: the South Coast Mountains, occupying the to these requirements, they, like other ephemeral pool western two-thirds of the county, and the Colorado plants and animals, are prone to endemism (Eng et al. Desert, occupying Anza Borrego State park and the 1990, Mura 1991) . surrounding area. Eight South Coast Mountain sites California's temporary inland waters and saline were sampled (Fig . 1,Table 1). These sites are primarily lakes support a diverse. but poorly studied branchiopod vernal pool complexes in various states of disturbance fauna(Wootton andMattox 1958, Lynch 1%6, Sassaman (Bauder 1986, Zed1er 1987). These pools typically fill 1989, Eng et al. 1990, Ahl 1991, Sassaman 1991). The during winter or early spring rains. Four COlorado twenty described species of Anostraca in California, Desert sites were sampled (Fig. 1, Table 1). These sites seven of which are endemic. comprise forty-four per cent are primarily playas except the Mortero Wash site which of the total species diversity in the United States (Eng et is a pool formed in a desert wash. The desert sites can fill al. 1990, Belk and Serpa 1992, Fugate in press) and from either cool winter rains or warm summer another is currently being described (M. Fugate, pers . thunderstorms, 6 TRANS. WEST. SECT. WILDL SOc. 28: 1992 Branchiopod D iversity · Simovich and Fugate 7 METHODS species hatches from 0-25°C, tolerates temperatures up Samples have been collected since 1988 by either to 36°Casan adult (Belk 1977a), and is found overa wide sampling with aquatic dip nets after rainfall filled pools range of pH and salinity values (McCarraher 1970, Eng or by hydrating soil samples in the laboratory. Soil et al. 1990) . Development times in the laboratory or the samples consisted of sediment from the top 2-5 em ofdry field can beas short as 8 to 12 days (Donald 1983, Fugate pools. These samples were washed through 500 and 180 unpubl. data) at some temperatures. um sieves and the soil in the 180 um sieve was examined Bran chinecla lindahli was the only species previously for branchiopod eggs. The eggs of most branchiopods reponed from San Diego County (Balko and Eben 1984, can be identified to genus and in some cases to species Eben and Balko 1984, Eng et al. 1990) . However, (Alonso and Alcarez 1984. Mura 1986, 1991, Mura and reexamination (by M. Fugate and D. Belk) ofthe voucher Thiery 1986, Thiery and Gasc 1991). Samples with eggs specimens from these studies has shown them to be were hydrated by placing 150 rnl of sediment in a 10 Branchinecta sandiegoensis. The species was gallon aquarium and adding 251ofdeionized water. The subsequently found in desert playas whichalso contained aquaria were continuously illuminated with fluorescent combinations of Thamnocephalus platyurus, Eocyzicus light and"grow lights" , aerated vigorously for 24 hours, digu eti and/or Triops newberryi (Table 1). Branchinecta stirred and then gently aerated. Upon hatching, shrimp lindahli was also found in a single road rut on Naval Air were fed small amounts of baker's yeast until they Station Miramar and a few individuals in one rut on Del reached a length of at least one centimeter at which time Mar Mesa (Table I, Fig. 1). they were fixed or frozen. Hydrations were conducted at Branchinecta sandiegoensis Fugate, although temperatures, between 10° and 25° as these temperatures collected in 1962 and deposited in collections of the bracket the ranges of species inhabiting San Diego (Eng United StatesNational Museum, Washington, D.C., was et al. 1990 , Sirnovich, unpubl. data). misidentified as B. lindahli, This species was recognized Branchiopods were identified by comparison with as a new species in 1990 and was recently described original descriptions or re-descriptions of species, but (Fugate 1992 in press). Only limited information on its species identification isproblematic in both Conchostraea physiological requirements and life history exists. It was and Notostraca (Belk 1989, Sassaman 1991) . The found usually in shallow « 30 ern) pools, predominantly species ofthe clam shrimpfamily Cyzicidae, for instance, on mesas, after winter and spring rains, at water have often been described using size-dependent characters temperatures of 1O-26°C. Our preliminary laboratory without accompanying development studies and we have results suggest that the species can hatch at cool chosen to accept the earliest name recorded in the temperatures (1O-15°C) (un publ. data). literature for species, consistent with the International This species is currently known only from San Diego Code of Zoological Nomenclature. Animals were fixed County samples (Table!, Fig. I ) and from Valle de las in 10% formalin or Bouin's solution andthen transferred Palmas, Baja California None, Mexico (presumably the to70%ethanolor were frozen for protein electrophoresis. same mesa system) . It iscommonly the only branchiopod Voucher specimensand their collection data are available species in a pool, but was found in the same two pools as in the UDiversity of San Diego Branchiopod Collection. Streptocephalus woottoni and Cyzicus californicus at Otay Mesa and in a pool with S. woottoni at Naval Air RESULTS AND DISCUSSION Station Miramar . In these mixed pools, B. sandiegoensis Eight branchiopod species were found in San Diego was found earlier in the season than the other species. County: four fairy shrimp species in threefamilies, three Also, a few B. lindahli «0.1%) were found with it in one clam shrimp species in two families, and one tadpole rut on Del Mar Mesa. shrimp (Table 1).Present collections may underestimate TheU.S. Fish and Wildlife Service hasbeen petitioned the total diversity in the county, due to both the limited to list B. sandiegoensis as an endangered species (D. sampling of pools and the specific requirements of Hogan, pers. comm.) due to its restricted distribution and individual species which may prevent all the species the loss of approximately 97% of this habitat in San present from hatching after a natural filling or hydration. Diego (E. Bauder, T. Oberbauer, pers. comm.). Streptocephalus woottoni Eng, Belk and Eriksen is Anostraca (Fairy Shrimp) California's most restricted endemic fairy shrimp. This Branchine cta lin dahli Packard is common species was described from five large (>750 rn")and deep throughout western North America (Eng et al.