Chthamalus panamensis Pilsbry, 1916

Pitombo, Fábio Bettini & Burton, Ron, 2007, Systematics and biogeography of Tropical Eastern Pacific Chthamalus with descriptions of two new species (Cirripedia, Thoracica), Zootaxa 1574 (1), pp. 1-30 : 15-17

Chthamalus panamensis Pilsbry, 1916

( Figures 16–18 )

The original description of C. panamensis by Pilsbry (1916) lacked a description of the “soft parts”. Therefore, a supplementary description of C. panamensis based on one specimen collected at the type locality is provided. The specimens were collected at Punta Culebra, formerly Culebra Island and also known as Quarantine Island in the early nineties.

Material. Specimens from Punta Culebra, Panama City, Panama. One specimen was used for the supplementary description: MNRJ-20440.

Supplementary description. Shell: externally brown to white with narrow, deep folding reaching apex; internally of wall white when cleaned, sheath brown, orifice wide; articulation between scutum and tergum presenting a slight angle; rostro-carinal and orifice aperture diameters 7.5mm and 2.5mm, respectively.

Scutum: both plates corroded in upper part, growth lines only in the lower third; length/width ratio of right and left plates 1.9 and 2.0, respectively; plates symmetric; occludent margin of left scutum with growth lines on inner face occupying 17% its height (right scutum not showing inward growth); articular furrow wide, articular ridge short, not reaching tergal margin; adductor muscle ridge weak, not reaching basal margin; lateral depressor muscle pit deep, smooth; sum of occludent angles 147 0; ratio between width of adductor muscle insertion and width of scutum at level of adductor muscle 0.3 for both plates.

Tergum: wide, ratio between scutal and carinal margins 0.85 for both plates; scutal margin of left tergum 1% higher than right; spur short, wide; right plate with 3 tergal depressor muscles crests, extending about 1/3 of carinal margin, left plate with 4 tergal depressor muscles crests, extending about 1/5 of occludent margin; deep, wide, strong longitudinal furrow on outer face close to scutal border in both plates.

Labrum: upper margin concave, bearing row of short conical teeth.

Palps: upper margin covered by single row of shor smooth setae proximally and distally towards superodistal angle, setae lengthening to form clump; very long, pinnate setae on distal margin lengthening toward infero-distal angle.

Mandible: quadridentoid, fourth tooth double, row of approximately 20 closely spaced, fine spines below; lower angle of left mandible with 3 strong spines, right mandible with 2 strong spines.

Maxilla I, cutting edge with 3 steps; upper angle with pair of developed spines and 1 shorter marginal spine, 4 and 3 slender spines below; notch weak, row of 6 subequal spines below, lower one short, thick, bifid, on left and right maxillae, respectively; inferior angle protuberant, covered with row of slender spines with one strong central spine.

Cirrus I: right and left cirri composed of 8 (outer) and 6 (inner) articles; inner face of articles of both rami covered with long, acuminate, pinnate setae; outer face of outer rami with longitudinal row of long setae; inner rami without bidenticulate setae.

Cirrus II: right cirrus composed of 6 (outer) and 5 (inner) articles, left cirrus formed by 6 (outer) and 6 (inner) articles; bidenticulate setae with basal guards (complex setae) present on inner face of distal articles of both cirri; right and left outer rami with 4 and 6 complex setae on distal articles; right and left inner rami with 3 and 2 complex setae on distal article, respectively; inner face of articles covered with long, acuminate, finely pinnate setae.

Cirrus III: right and left cirri antenniform, right cirrus composed of 20 (outer) and 14 (inner) articles; left cirrus formed by 19 (outer) and 14 (inner) articles; inner face of outer rami with 4 pair of long setae on 3 (right) and 4 (left) medial articles; inner face of both inner rami with 4 pairs of long setae on 6 (right) and 5 (left) medial articles; short setae on protuberance between each pair of long setae; most distal article of each ramus with group of 3 stout setae distally, feature repeating from cirri IV to VI.

Cirrus IV: right cirrus composed of 17 (outer) and 15 (inner) articles; left cirrus with 14 (outer) and 15 (inner) articles; inner face of outer rami with 4 pairs of setae on 5 (right) and 6 (left) medial articles; inner face of both inner rami with 4 pair of setae on 8 medial articles.

Cirrus V: right cirrus composed of 16 (outer) and 15 (inner) articles; left cirrus with 14 (outer) and 16 (inner) articles; inner face of outer rami with 4 pairs of setae on 11(right) and 10 (left) medial articles; inner face of inner rami with 4 pair of setae on 11 (right) and 8 (left) medial articles.

Cirrus VI, right cirrus composed of 16 articles on both rami; left cirrus is formed by 16 (outer) and 17 (inner) articles; inner face of both outer rami with 4 pairs of setae on 9 (right) and 10 (left) medial articles; both inner rami with 5 pair of setae on 10 (right) and 9 (left) medial articles.

Penis with genital aperture surrounded by tuft long setae, 4 longitudinal rows of long setae radially placed on distal third.

Distribution. Punta da Mita, Banderas Bay to Panama ( Figure 8 ).

Habitat. Chthamalus panamensis , like C. hedgecocki , is found in the upper midlittoral zone preferably on wave-exposed shores, but it is also found at protected sites.

Remarks. Chthamalus panamensis belongs to the C. fissus group as it has bidenticulate setae with basal guards on cirrus II and lacks conical spines on the outer ramus of cirrus I. Within the C. fissus group, the articular ridge not extending beyond the tergal margin is the main feature that distinguishes C. panamensis from C. proteus , C. fragilis and C. anisopoma . The form of the tergum, quadrangular in C. panamensis and triangular in C. fissus , distinguishes the species. The presence of a longitudinal furrow on the outer face of the tergum, a feature shared with C. hedgecocki , distinguish these two species from all others within the genus. However, C. panamensis presents a well-marked furrow on both plates.

Figures

FIGURE 8. Distribution of Chthamalus hedgecocki sp. nov., C. panamensis Pilsbry and C. dalli Pilsbry along the western coast of the Americas. Symbols mark the localities from where specimens were examined; encircled symbols indicate localities where the COI gene was sequenced.

FIGURE 16. Chthamalus panamensis Pilsbry, 1916, MNRJ-20440. Shell with opercular plates not removed. Scale bar = 1mm.

FIGURE 17. Chthamalus panamensis Pilsbry, 1916, MNRJ-20440. Opercular plates. A–D scuta; E–H terga; A, C, E, F left plates; B, D, G, H right plates; A, B, F, G outer face; C, D, E, H inner face. Scale bar = 1mm.

FIGURE 18. Chthamalus panamensis Pilsbry, 1916, MNRJ-20440. A Mandible; B Maxilla I. Scale bar = 0.05 mm.