Heteralepas segonzaci, Young, 2001

Young, Paulo S., 2001, Deep-sea Cirripedia Thoracica (Crustacea) from the northeastern Atlantic collected by French expeditions, Zoosystema 23 (4), pp. 705-756 : 711-715

Heteralepas segonzaci n. sp.

( Figs 4 ; 5 )

TYPE MATERIAL. — Holotype: 1 hermaphrodite, SEA- MOUNT 2, stn TS 267, 34°22.50’N, 30°22.50’W, 2235 m, tl 23.5 mm (MNHN Ci 2825); paratype: 1 complemental male originally attached to the hermaphrodite, tlp 1.0 mm (MNHN Ci 2826).

ETYMOLOGY. — Named in honor of Dr Michel Segonzac, who was largely responsible for making them available for this study.

DIAGNOSIS. — Capitulum with irregular deep and wide grooves; aperture more than half length of capitulum; carinal margin without crest, only a wide, angled region basally. Peduncle almost one-third length of capitulum. Cirrus I with anterior ramus three-quarter length of posterior ramus. Median articles of cirri VI almost three times wider than long, having short, wide seta posterior to major apical setae of anterior margin; distal margin with simple scales on posterior half.

DESCRIPTION

Cuticle ( Fig. 4A, B ) with irregular deep and wide groovesonthecapitulum,especiallyonesurrounding aperture; transverse grooves near aperture, wrinkled near aperture and on peduncle, not pilose.Aperture ( Fig. 4C, D ) more than half of capitulum length, folded. Scutal area inconspicuous, without crest. Carinal margin of capitulum without conspicuous crests, only a wide and angled region basally.Peduncle cylindrical, almost one-third of capitulum length.

Labrum ( Fig. 5A ) little prominent, with one row of equal teeth (± 20) and some smaller teeth (± 4) on lateral surfaces. Palp ( Fig. 5A, B ) long, acuminate with several long simple setae on distal half and on inner margin. Mandible ( Fig. 5C ) with four acute teeth, last on rounded, sparcely denticulate, lower angle; distance between first and second teeth twice or less distance between second and third; first to third teeth with lower margin having strong, sharp denticles; second to fourth teeth with upper margins slightly denticulate. Maxilla I ( Fig. 5D ) with two large and one medium spine on upper angle, followed by wide notch with few fine, medium spines and strong, small spines (four to five), lower squared projection with numerous (20-30) unpaired medium to small spines. Maxilla II ( Fig. 5E ) bilobed, anteri- or lobe large, slightly notched in middle, nearly quadrangular; posterior lobe small, rounded; both covered by several, long, slightly pinnate setae. Cirri with article setation of lasiopod type. Cirrus ( Fig. 5F ) with unequal rami, anterior ramus three-quarter length of posterior ramus; shorter ramus with articles slightly wider than those of posterior ramus, both rami covered by numerous simple or long pinnate setae; articles of protopodite with plumose setae on posterodistal angle; one filamentary appendage at its base. Cirri II with subequal rami, and cirri III and IV with equal rami, both having simple and long, slightly pinnate setae. Cirri V and VI with anterior rami long, posterior rami reduced, approximately one-third and two-fifth length of anterior rami, respectively. Median articles of cirri V and VI ( Fig. 5G ) almost three times wider than long, anterior margin with one pair of long slightly pinnate setae, four times width of article, and two pairs of short simple setae, and one short strong seta posterior to large setae; postero-distal angle with one to five simple setae; distal margin with simple scales on posterior half. Distal articles of reduced rami approximately two times longer than wide, basal articles as long as wide, with few setae on distal margin. Caudal appendage ( Fig. 5H ) with 13-15 articles little longer than protopodite of cirrus VI, with setae on distal margins. Number of articles of cirri I-VI and caudal appendage is presented in Table 2. Penis short, covered with fine setae.

Complemental male only reduced in size, with fully developed cirri.

REMARKS

The single specimen has a small complemental male attached immediately below the aperture. When examining the specimen I had doubts if it was actually a male or a juvenile which attached to the first one. The position where it was fixed, just beneath the aperture of the hermaphrodite strongly suggests it is a male. Otherwise the hermaphrodite was incubating several nauplii.

Kolbasov & Zevina (1999) described a species of Paralepas which has the first complemental male known for the family. This present find suggests that complemental males are perhaps more widely distributed in the Heteralepadidae .

Heteralepas segonzaci n. sp. was collected at a greater depth than H. microstoma , which first alerted me that it was probably a different species. I first thought that the grooves on the capitulum were only generated by external factors instead of by its own growth. None of the other species of Heteralepas have these deep irregular grooves on the capitulum. On its left side, a rounded scar is due to the presence of a serpulid tube, but the other grooves especially a large one posterior to the aperture does not appear to be the result of settlement of other animals or by predators. Besides the grooves, the aperture size, the absence of crests and the peduncle size distinguish this species from H. microstoma .

Aside from the characteristic reduction of the posterior rami of cirri V and VI, the other characters of mouth and thoracic appendages appear to be very conservative in Heteralepas species. Observable differences appear to be only the relative size of the cirral rami and caudal appendages, the number of articles and the ornamentation of the articles. Presently, however, it is difficult to review these characters because most of the appendages of the species are poorly or not described at all.

Besides H. segonzaci n. sp. found at 2235 m only H. cornuta (Darwin) from 4315 m ( Ross 1975: 17) and H. lankesteri (Gruvel, 1900) from 1497 m ( Gruvel 1900a: 195) were recorded in depths greater than 1000 m. On the other hand, only H. cornuta ( Darwin, 1852) , H. microstoma ( Gruvel, 1901) and H. rex (Pilsbry, 1907) ( Gabon) are recorded from the eastern Atlantic.

Figures

FIG. 4. — Heteralepas segonzaci n. sp., holotype, SEAMOUNT 2, stn TS 267; A, B, right and left lateral view; C, rostral view; D, detail of the aperture with small male below. Scale bars: A-C, 5 mm; D, 2 mm.

FIG. 5. — Heteralepas segonzaci n. sp., holotype,SEAMOUNT 2, stn TS 267; A, labrum and palp; B, mandible; C, maxilla I; D, maxilla II; E, cirrus I; F, median articles of cirrus VI; G, protopodite of cirrus VI and caudal appendage. Abbreviations: a, anterior ramus; C I, cirrus I; C VI, cirrus VI; ca, caudal appendage; p, posterior ramus. Scale bars: A-D, F, 0.5 mm; E, G, 1 mm.