Biodiversity and Biogeography of Chthamalid Barnacles from the North-Eastern Pacific (Crustacea Cirripedia) Author Benny K. K. Chan Author H. - N. Chen Author P. R. Dando Author A. J. Southward Author E. C. Southward text PLoS ONE 2016 2016-03-09 11 3 1 51 journal article 10.1371/journal.pone.0149556 f02345d5-4425-434a-8574-883833ae0b6f PMC4784953 26958842 1161582 Chthamalus anisopoma Pilsbry, 1916 Figs 2A and 6–8 Chthamalus anisopoma Pilsbry, 1916: 317, pl 74, fig 2–2f. [ 2 ]—Barnes & Barnes, 1965: 392. [ 26 ]—Henry, 1942: 127. [ 27 ]—Henry, 1943: 372. [ 28 ]—Henry, 1960: 144 [ 29 ]—Kolosvary, 1941: 70. [ 30 ]—Nilsson-Cantell, 1921: 276. [ 31 ]—Pitombo & Burton, 2007: 14. [ 12 ] Specimens examined. AJS-2, 36 specimens, intertidal shores, La Paz Bay, Baja California, 24° 13' N, 110° 18.6' W, 3 Nov 1978; AJS-3, 6 specimens, intertidal shores, Point Lobos,Todos Santos, Baja California Sur, Mexico, 23° 24.8' N, 110° 57' W, 4 Nov 1978. TEPE78-24, 12 specimens, intertidal rocks, Isla Cerralvo, Baja California Sur, Mexico, 24° 08' N, 109° 48' W, 14 April, 1978; TEPE78-35, 36 specimens, La Paz Promenade, Baja California Sur, Mexico, 24° 09' N, 110° 15' W, 18 April, 1978. Diagnosis. Chthamalus with strongly asymmetrical scuta and terga. Orifice often filled by left or right tergum and scutum. Cirrus I distalmost segment of posterior ramus with 2–3 bidenticulate setae. Cirrus II with bidenticulate setae with basal guards on the 4 distalmost segments of the posterior ramus and with bidenticulate setae with basal guards on the two distal segments of the anterior ramus. White tergoscutal flaps in fresh specimens. Description. Shell white, depressed conic, external surface strongly and irregularly ribbed ( Figs 2A and 6A ). Eroded specimens often have the basal region of the shell ribbe d but the apical region is smooth. Orifice elliptical and often closed by the left tergum and scutum ( Figs 2A and 6A ). Tergoscutal flaps have white edge ( Fig 2A ) (the white colour is still visible after preservation in formalin or ethanol). Scutum and tergum strongly asymetrical ( Fig 6B–6D ). Individuals can have the left scutum and tergum larger than the right scutum and tergum or vice versa ( Fig 6B and 6D ). The larger scutum is triangular, with equal sides, the smaller one is narrower. The external surface of the scutum is smooth with growth lines near the basal margin ( Fig 6C ), occludent margin smooth, tergal margin with shallow articular ridge, not extending beyond the tergal margin. Adductor muscle scar oval, lateral depressor muscle scar oval and smooth. Tergum triangular to trapezoid, 3–4 lateral depressor muscle crests on basal margin ( Fig 6B and 6D ) Segment counts on cirri I-III were based on five specimens collected from La Paz Bay, Baja California (AJS-2). Segment counts on cirri IV-VI were based on a single specimen from La Paz Bay, Baja California (AJS-2) ( Table 4 ). Cirrus I: posterior ramus with 6 or 7 segments, anterior ramus 7- or 8-segmented, both rami with serrulate setae dominant, the distalmost segment of the posterior ramus with 2–3 bidenticulate setae ( Fig 7A and 7B , Table 4 ). Cirrus II: posterior ramus 5-segmented, anterior ramus 6- or 7-segmented, serrulate type setae dominant on both rami. Posterior ramus with bidenticulate setae with basal guards on the 4 distalmost segments ( Fig 7C and 7D , Table 4 ), anterior ramus with bidenticulate setae with basal guards on the two distalmost segments ( Fig 7C and 7E , Table 4 ). Cirri III-VI: similar in morphology, serrulate type setae dominant, anterior ramus similar in length to the posterior ramus. Cirrus III: anterior ramus 13 to 19-segmented, posterior ramus 11 to 16- segmented ( Fig 7F , Table 4 ). Cirrus IV: anterior ramus 17-segmented, posterior ramus 15-segmented ( Fig 7G ). Cirrus V and VI: anterior ramus 18-segmented, posterior ramus 17-segmented ( Fig 7H ). Intermediate segments of anterior rami of cirri IV-VI have 4 pairs of long serrulate setae and 1 pair of short serrulate setae ( Fig 7F–7H ). Maxilla bilobed, with serrulate setae on both lobes ( Fig 8A ). Maxillule notched, 2 large and 4 medium sized setae above notch, 16 setae below notch of cutting margin ( Fig 8B ). Mandible has 4 major teeth, first tooth separated from the remainder, fourth tooth bi-dentate. Pecten long and straight, with 30 fine teeth, inferior angle tipped with two pointed teeth ( Fig 8C and 8D ). Mandibular palp rectangular, with serrulate setae on all margins ( Fig 8E and 8F ). Labrum V-shaped, with ~ 10 small teeth on both sides of the cutting margin ( Fig 8G ). The middle notch with dense setae ( Fig 8H ). Penis without basi-dorsal point. Distribution. Present in the Gulf of California and on the Pacific coast of Baja California Sur to at least 23° 27' N. Remarks. C . anisopoma is sympatric with C . alani nom. nov. and C . hedgecocki on some shores. C . anisopoma can be easily identified in-situ by its strongly asymmetrical opercular plates, also by its white tergoscutal flaps when open under water ( Fig 2A ).