A DESCRIPTION OF THE NAUPLIAR STAGES OF THE BARNACLES ,BALANUS GLANDULA DARWIN, BALANUS CARIOSUS PALLAS, AND BALANUS CRENA TUS BRUGUIÈRE (CIRRIPEDIA, THORACICA) BY E. SANFORD BRANSCOMB and KAREN VEDDER Friday Harbor Laboratories, Friday Harbor, Washington 98250, U.S.A. INTRODUCTION Larval descriptions for the balanomorph barnacles found in Puget Sound are limited to studies of Balanus crenatus Bruguière, 1789 (cf. Pyefinch, 1949; Herz, 1933), Balanus hesperius Pilsbry, 1916 (cf. Barnes & Barnes, 1959b), Balanus balanus (L., 1758) (cf. Crisp, 1962; Barnes & Costlow, 1961) and Balanus nubilis Darwin, 1854 (cf. Barnes & Barnes, 1959a). Two of the common intertidal balanomorphs, Balanus glandula Darwin, 1854 and Balanus cariosus (Pallas, 1788), whose range includes much of the east coast of the North Pacific, have not been described at all. In an attempt to fill these gaps this study provides descriptions of all three intertidal balanoid species found in Puget Sound: B. glandula, B. cariosus, and B. crenatus. Our description of B. crenatus is not in agreement with previously published descriptions (Pyefinch, 1949; Herz, 1933). MATERIALS AND METHODS Adult barnacles were collected from the shore at Friday Harbor Laboratories and the eggs removed. Eggs which were sufficiently developed hatched spontaneously. Because metamorphosis to the second naupliar stage occurs shortly after hatching, we preserved some stage I larvae immediately in a 10% formalin solution. Thereafter, samples were removed daily and pre- served. We fed the larvae a mixture of Thalassiosira-_ fluaiatilis and Skeletonema costatum (Greville) and maintained the cultures through the cyprid stage. Larvae were stained with Gentian violet for 60 seconds prior to examination. Appendages for each naupliar stage were then removed, examined under a microscope, and drawn by means of a camera lucida. Several individuals at each stage were examined to establish a definitive setal formula for each naupliar stage. 84 I . TABLE I Setal types of cirriped nauplii / S simple s spine P plumose st stub D plumodenticulate Y "rabbit-eared" stub C cuspidate SP S, sometimes P . G gnathobase P' P, sometimes D ' RESULTS Lang (1979) has reviewed the diagnostic characteristics used to describe barnacle nauplii. We have adopted his setal terminology (summarized with corresponding abbreviations in table I) to describe the four types which we found: 1. Simple setae taper to a point and have no setules or projections. 2. Plumed setae have few to many projections and also taper to a point. Plumation can be variable and may also be difficult to discern. 3. Plumodenticulate setae are plumed proximally with a serrated tip. 4. Cuspidate setae have an enlarged base which tapers to a tip. They may be plumed or denticulate. We found that all three species show the stage-specific features typical in other balanomorph nauplii, described by Lang (1979). Stage I larvae are characterized by collapsed frontal horns. For determining stages II through VI we found it sufficient to examine the preaxial setae of the first antenna, Ai : stage II, no preaxial setae; stage III, one preaxial seta; stage IV, two preaxial setae; stage V, three preaxial setae; stage VI three preaxial setae and three eyes. At times the two additional eyes were not visible in preserved larvae; however, stage VI is the only stage at which there are six pairs of spines easily discernible on the abdominal process. The setal formulae established for the appendages are given in tables II-IV, and the sketches for the various stages and appendages are shown in figures 1 through 8. ' DISCUSSION As Crisp (1962) noted, usually neither setae nor setules are lost in subse- quent stages once they have appeared. We found one occurrence of a plumed seta's replacement by a simple one between stages II and III on the Balanus crenatus mandible. Other apparent occurrences in our tables derive from how the setae lay on the slide; and we determined a PPPS configuration, for exam- ple, to be equivalent to PSPP. There may also be occasions when a plumed seta appears on an individual nauplius a stage earlier than indicated by the tables, apparently due to the variation occurring within broods. Setules are .