Abstract: Three new species of saccocirrids from interstitial sand habitats off O'ahu, Hawai'i, are described. Two are from subtidal depths, 9-33 m, and the third is from the intertidal to 3.5 m deep on a fringing reef and at Hanauma Bay, the Marine Life Conservation District and public park. The two deeper-water species, Saccocirrus oahuensis, n. sp. and S. waianaensis, n. sp., have 76-119 and 157-210 segments, respectively; they also have bilateral gonads but lack a pharyngeal pad. The third, S. alanhongi, n. sp., has 35-47 segments, unilateral gonads, and a muscular pharyngeal pad. These species are distinguished from 18 known Saccocirrus spp. by their unique chaetation, number of segments, presence or absence of ventral cilia, and pygidial adhesive structures. Saccocirrus oahuensis consumes foraminiferans, and S. alanhongi contained diatoms, unicellular algae, and ostracods. These species add to the interstitial fauna of O'ahu and cooccur with polychaetes Nerilla antennata (Nerillidae) and protodrilids (Protodrilidae), and Kinorhyncha. Saccocirrus alanhongi withstands almost daily disturbance by 600-1200 bathers per day entering the sandy swimming holes in the reef at Hanauma Bay.
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SACCOCIRRIDS WERE FIRST recorded from Hawai'i in 1979, when they were found in sand on a shallow fringing reef near Pearl Harbor on the south shore of O'ahu, Hawai'i (Bailey-Brock 1979). This unnamed species from Fort Kamehameha reef was added to the polychaete fauna as Saccocirrus sp. in a revision of C. H. Edmondson's Reef and Shore Fauna of Hawai'i (Bailey-Brock 1987). Saccocirridae were classified as "Archiannelida," which included Protodrilidae, Nerillidae, Dinophilidae, and Polygordiidae (Jouin 1971, Westheide 1985). This old grouping of five families has since been discarded (Westheide 1985, 1990) and all are families of Polychaeta. Westheide's papers emphasized the interstitial habitat as a unifying characteristic of eight families, including the five just listed and Protodriloidae, Diurodrilidae, and Parergodrilidae. Representatives of two families, Mesonerilla fagei and Nerilla antennata (Nerillidae) and Protodrilus sp. (Protodrilidae), are known from Hawai'i (Bailey-Brock 1987, 1999). Recently another protodrilid species, Parenterodrilus sp., was collected off Ni'ihau, Hawai'i, and awaits further study. In this paper we add three species of Saccocirrus collected from sand habitats in a shallow bay and on fringing reefs to depths of 35 m off O'ahu, Hawai'i.
MATERIALS AND METHODS
Collections were made by hand with a corer 7.6 cm in diameter by 5 cm deep from 0.5- to 3.5-m depths in Hanauma Bay and from the seaward side of the intertidal reef flat at Fort Kamehameha, bordering the entrance to Pearl Harbor. Scuba divers collected sediment cores of medium-grain calcareous sand off Wai'anae, and at Mamala Bay stations off the south shore of O'ahu. Those from greater depths (50 m or more) were taken with a van Veen grab deployed from a research vessel. All were preserved in 10% buffered formalin and Rose Bengal for 24 hr or more, elutriated over 0.50- and 0.25-mm mesh sieves, and stored in 70% ethanol. Preserved specimens were mounted in glycerol on slides and examined with phase contrast and dark and bright field microscopy. Magnifications for line drawings...