Heteralepas cornuta ( Darwin, 1852 )

Young, Paulo S., 2001, Deep-sea Cirripedia Thoracica (Crustacea) from the northeastern Atlantic collected by French expeditions, Zoosystema 23 (4), pp. 705-756 : 707-710

Heteralepas cornuta ( Darwin, 1852)

( Figs 1-3 )

Alepas cornuta Darwin, 1852: 165 , pl. 3, fig. 6. — Hoek 1883: 29; 1907a: 34. — Weltner 1897: 239. — Gruvel 1905: 161, fig. 178.

Heteralepas cornuta – Pilsbry 1907a: 101. — Nilsson- Cantell 1921: 246; 1927: 756; 1938: 27. — Broch 1927a: 538, fig. 510; 1927b: 16, pl. 4, figs 26-29. — Newman 1960: 109. — Ross et al. 1964: 312. — Stubbings 1964: 107; 1965: 880; 1967: 239. — Ross 1975: 17, fig. 1. — Weisbord 1979: 9, pl. 1, fig. 6. — Rosell 1981: 287, pl. 4, fig. g-l; 1991: 31, fig. 5d. — Zevina 1982: 116, fig. 102. — Jones et al. 1990: 6. — Young 1995: 239; 1998a: 12, figs 3, 4c.

Heteralepas (Heteralepas) cornuta – Krüger 1911: 29.

MATERIALEXAMINED. — SEAMOUNT 2, stn CP 121, 28°06.26’N, 15°51.82’W, 200 m to 28°06.76’N, 15°51.06’W, 200 m, 22 specimens, tl up to 6.8 mm (MNHN Ci 2821, MNRJ 13884).

DESCRIPTION

Cuticle ( Fig. 1A ) smooth on capitulum, except for minor transverse grooves near aperture, and wrinkles on peduncle, not pilose. Aperture nearly half length of capitulum, folded. Scutal area inconspicuous. Carinal margin of capitulum with two conspicuous triangular projections, one at middle of capitulum margin and another on capitulum base, both projections with distinctly hyaline apex. Peduncle cylindrical, almost length one-third of capitulum, with one obtuse projection on middle of carinal margin. Appearance of carinal projections are progressive with growth; smaller specimens may have only uppermost projection and intermediate size specimens may have only two carinal projections ( Fig. 3 ).

Labrum ( Fig. 1B ) prominent, with one row of equal teeth (33). Palp ( Fig. 1C ) acuminate with long pinnate setae on distal half and few short simple setae on proximal half of inner margin. Mandible ( Fig. 1D ) with three acute teeth and pointed denticulate lower angle; distance between first and second teeth twice distance between second and third; second and third teeth with upper margins slightly denticulate. Maxilla I ( Fig. 1E ) with three large spines on upper angle, followed by wide notch with few small spines (four to five), and lower squared projection with several (20-19) unpaired medium to small spines. Maxilla II ( Fig. 1F ) bilobed, anterior lobe large, nearly squared; posterior lobe small, rounded; both covered by several long simple setae.

Cirri with article setation of lasiopod type. Cirrus I ( Fig. 2A ) with unequal rami, anterior ramus two-third length of posterior ramus; shorter ramus with wider articles than those of posterior ramus, both rami covered by numerous simple or slightly pinnate setae; articles of protopodite with plumose setae on postero-distal angle. Cirrus II rami subequal, but articles of anterior ramus much wider, with simple and long pinnate setae. Cirri III and IV with rami equal in length and width. Cirri V and VI ( Fig. 2B ) with anterior rami long and posterior rami greatly reduced, approximately one-third length of anterior rami. Median articles of cirri V and VI 1.7 time wider than long ( Fig. 2C ), with one pair of long simple setae, more than four times width of article, and two pairs of short simple setae; postero-distal angle with one-third simple setae. Articles of reduced rami approximately six times longer than wide ( Fig. 2D ), with one small seta on antero-distal angle and few setae on postero-distal angle.

Caudal appendage ( Fig. 2B, E ) multiarticulated (eight to nine articles) approximately equal to length of protopodite of cirrus VI, with setae on distal margins. Number of articles of cirri I-VI and caudal appendage is presented in Table 1. Penis short, covered with fine setae.

REMARKS

Heteralepas cornuta has an unusual distribution, with records from the Indo-Malaysian region, Atlantic Ocean ( Senegal, Florida, West Indies [type locality] and Brazil) and off Chile ( Darwin 1852: 165; Broch 1927b: 16; Nilsson-Cantell 1938: 27; Ross et al. 1964: 312; Ross 1975: 17; Stubbings 1964: 107, 1965: 880; Rosell 1981: 287, 1991: 31; Jones et al. 1990: 6; Young 1995: 239, 1998a: 12). Most of these records were from depths between 70 and 200 m, but Stubbings (1965) found it at 750 m from Senegal and Ross (1975) at 4235-4315 m from off Chile. The new record of this species from the Canary Islands at 200 m is in consonance with its known distribution. The odd distribution, especially its depth distribution, suggests we may be identifying more than one species as H. cornuta . Some differences on the figures of various authors are apparent in external characters: Darwin (1852: pl. 3, fig. 6) figured a specimen with three equal-sized triangular projections on the posterior margin of the capitulum, and a smooth peduncular margin. Broch (1927b: pl. 4, fig. 29) in his fully developed specimen, observed only two triangular projections on the capitulum and a small projection on the peduncle. In his figure the third projection, depicted by Darwin near the occludent margin, is lacking. Ross (1975: fig. 1) figured a specimen with three small blunt projections on the capitulum and a smooth peduncle. Rosell (1981: pl. 4, fig. g) only figured two short projections on the posterior margin of the capitulum.

The full grown specimens I reported from the eastern Atlantic ( Young 1998a: fig. 4c; herein, Fig. 1A ) have the pattern described by Broch (1927b) which was also based on northeastern Atlantic specimens. Furthermore, no stage of the present specimens ( Fig. 3 ) have the patterns observed by Darwin (1852) and Ross (1975).

There are no difference between the appendages of eastern Atlantic specimens of Broch (1927b) and the specimens studied herein, except they have a larger number of articles. Darwin (1852: 166) described in detail the appendages of specimens from the West Indies. Of this description, I could observe only differences between the mandible and cirral counts. The mandibles described by Broch (1927b) and by myself from the eastern Atlantic had the upper margins of the teeth denticulate. Furthermore, Darwin’s (1852) article counts are larger than those of mine, but his caudal appendage has fewer articles. Darwin’s larger specimens was about 7 mm in capitulum length, the one figured by Broch about 6 mm (inferred from his pl. 4) and mine 5 mm. Ross (1975: fig. 1) figured the appendages of H. cornuta from deep water in the eastern Pacific. On the intermediate articles of his specimens cirrus VI has small spines on the lateral surface which are absent in the present specimens and the article counts are far greater.

Therefore, there are some differences between the specimens from the Atlantic (East and West), Pacific and Indian oceans. I cannot propose if these differences are populational or specific variations but the latter seems more likely. Several specimens from these localities must be studied to solve this problem. Hutchins (1952: 194) recorded H. cornuta fouling buoys, based on the unpublished data of I. M. Newell, from Woods Hole Oceanographic Institution. The depth range of H. cornuta does not encompass shallow waters where buoys are found. Therefore, this is probably a misidentification.

Figures

FIG. 1. — Heteralepas cornuta (Darwin, 1852), SEAMOUNT 2, stn CP 121; A, left lateral view; B, labrum and palp outline; C, palp; D, mandible; E, maxilla I; F, maxilla II. Scale bars: A, 2 mm; B-F, 0.2 mm.

FIG. 2. — Heteralepas cornuta (Darwin, 1852), SEAMOUNT 2, stn CP 121; A, cirrus I; B, cirrus VI and caudal appendage; C, median article of cirrus VI; D, detail of the 7 and 8th article of posterior ramus of cirrus VI; E, detail of the 6 and 7th article of caudal appendage. Abbreviations: a, anterior ramus; C I, cirrus I; C VI, cirrus VI; ca, caudal appendage; p, posterior ramus. Scale bars: A, B, 0.5 mm; C, 0.3 mm; D, E, 0.1 mm.

FIG. 3. — Heteralepas cornuta (Darwin, 1852), SEAMOUNT 2, stn CP 121. Outlines of the capitulum and peduncle of some specimens with different sizes. Scale bar: 1 mm.