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CIRRIPEDES Barnacle Larvae Barnacle larvae are common and, occasionally, abundant in marine and estuarine plankton samples . The larvae pass through six similar naupliar stages before metamorphosing into the cyprid stage. Most nauplii use their anterior appendages for both swimming and feeding. Nauplii typically feed on phytoplankton, but some species are omnivorous. The cyprid (or cypris) larva is a nonfeeding stage specifically adapted for selecting the proper substrate for settlement. The cyprid swims using six pairs of posterior (thoracic) appendages. When testing the substrate, the cyprid “walks” around using its two antennules and senses the surface contour with the setae at the rear. Chemical cues are also used; sites with previous barnacle settlements are especially favored. At settlement, waterproof glue from the cement gland anchors the incipient barnacle in place. A dramatic metamorphosis into the adult form follows immediately. Barnacle Nauplius Larva Two horns on the head and their penchant for swimming upside down distinguish barnacle nauplii from the nauplii of penaeid shrimps and copepods. A pigmented eyespot is usually visible. Nauplii in the Semibalanus and Amphibalanus (=Balanus) group have cephalic shields distinctly different from those of Chthamalus. Nauplii occur at all seasons but especially in spring. The most common coastal barnacles, including Chthamalus fragilis, Amphibalanus venustus, A. amphitrite, and A. improvisus, are widespread. Barnacle nauplii are common to abundant in estuaries. Amphibalanus eburneus and A. subalbidus are the most common low-salinity barnacles of both Atlantic and Gulf estuaries and sometimes occur near freshwater. Semibalanus balanoides is a high-salinity northern species common in New England, ranging south to North Carolina. The first stage nauplii are about 0.2 mm. Because of their small size, retention of early nauplii in nets is often low. Later stages may reach 0.9 mm before the transition to the cyprid stage. References. Qiu et al. 1997. Barnacle Cyprid (or Cypris) Larva Cyprids (usually <0.5 mm long) have a smooth, flexible, and translucent bivalved covering that may or may not enclose the jointed appendages. Color is pale yellow to light brown with a somewhat reddish eyespot near the center of the body. The seedlike shape resembles ostracods and bivalves, but those groups have hard shells with surface sculpturing. Distinguishing separate species of cyprids is seldom feasible. Cyprids are relatively common, especially near the bottom, but are seldom as abundant as nauplii. Geographic distributions follow those of nauplii above. References. Berntsson et al. 2000; Dineen and Hines 1994; Elbourne and Clare 2010; Faimali et al. 2004; Lagersson and Hoeg 2002; Mullineaux and Butman 1991; Pechenik et al. 1993; Thiyagarajan 2010; Tremblay et al. 2007. USEFUL IDENTIFICATION REFERENCES Lang, W. H. 1979. Larval development of shallow water barnacles of the Carolinas (Cirripedia: Thoracica) with keys to naupliar stages. NOAA Technical Report NMFS Circular 421. 39 pp. CIRRIPEDES 137 Chthamalus fragilis Amphibalanus venustus Balanus sp. nauplius stage IV (of VI) nauplius stage IV of (VI) cyprid 0.1 mm 0.1 mm 0.1 mm ...


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