Ashinkailepas kermadecensis Buckeridge

Buckeridge, John S., 2009, Ashinkailepas kermadecensis, a new species of deep-sea scalpelliform barnacle (Thoracica: Eolepadidae) from the Kermadec Islands, southwest Pacific, Zootaxa 2021, pp. 57-65 : 61-64

Ashinkailepas kermadecensis Buckeridge sp. nov.

( Figure 1 ; Figure 2 A–C; Figure 3 A–C; Plate 1: figures 1–14)

Diagnosis. Ashinkailepas with capitular plates possessing strong apico-basal ridges crossed by well defined transverse growth ridges; tergum with prominent, narrow, apico-basal ridge; apico-medial latus ridge weak; defined central apico-basal “platform” absent; carina broadly arched; apex of scutum confluent with occludent angle of tergum.

Holotype: NIWA-44722 ( Figure 1 ; Plate 1: figure 5), a complete specimen (capitulum length 20.5mm, peduncle length 17.0mm).

Paratypes: NIWA-18008, a series of 12 specimens (including Plate 1: figure 4, which is comprised of two large individuals), capitulum lengths ranging from 3.5–20.5mm (see Table 1 ); J-55679 (comprising an adult with attached juvenile, Plate 1: figure 7) and J-55680 (Plate 1: figure 11).

Derivation of name. Geographic (Kermadec Ridge, South Pacific Ocean).

Material examined. NIWA 18008: 15 individuals ranging in size from 4.9–37.5mm (three of these possess attached juveniles), from stn. KOK0505/51, 31º51.65’S, 180º48.71’E at 1165 metres. Collected on 18th April 2005.

Geographic and environmental setting. The collection was made from waters in the southern part of the Kermadec Ridge, in the southwest Pacific Ocean – c. 1000 kilometres to the northeast of the North Island of New Zealand. This is a part of a northeast trending volcanic arc, more than 1300 kilometres long, comprising up to 40 volcanoes, many of which are actively venting ( Wright et al., 2006). The barnacles were attached to vestimentiferan tubeworms growing on the northern wall of the southern-eastern caldera of the Wright Volcano. The substrate is mainly basaltic, with diffuse low-temperature venting (8–9ºC) adjacent to the sampling site (de Ronde et al., 2007).

Description. Capitulum comprising eight approximate, calcareous plates: carina, rostrum, and paired terga, scuta, and medial latera ( Figure 1 ); laterally compressed to slightly less than diameter of peduncle; plates with transverse growth ridges clearly defined, crossed by fine but well-formed apico-basal striae; incurved apices of carina and rostrum extending beyond capitulum for up to 15% of length, becoming more arcuate in adults; carina with umbo apical, tectum broad with sharp, prominent medial apico-basal ridge in profile appearing finely toothed due to strong transverse growth lines and striae (Plate 1: figures 1–3), parietes very narrow; tergum quadrangular, with sharp medial apico-basal ridge and faint secondary ridge extending from tergal apex to apex of medial latus; scutum quadrangular, tergal margin concave, gently incurved, occludent margin convex, basal angle sharp – generally c. 90º but ranging from 65–95º; medial latus triangular, apical angle c. 40º, generally 1.5x longer than wide, sometimes (Plate 1: figure 2) length and width approximate; peduncle with scales on outer (uncompressed) side large, triangular, up to 3x as wide as high, with protruding apices, arranged as vertical rows below carina and rostrum with two further rows below (where carinolateral and rostrolateral plates would be if this species had them); scales on inner compressed side small, apices rounded, only c. 1.5x as wide as high.

Internally, capitular plates are unremarkable. For the most part they are smooth except for where a plate extends beyond the soft tissue: here a zone of fine growth lines parallel the plate margin, e.g. in the tergum of NIWA-18008 (Plate 1, figure 2) this extends as a 1.2mm band from the apex to the occludent angle, and to a point adjacent to the apex of the carina; scutum with a shallow, smoothly rounded depression in the upper half of plate for adductor muscle attachment, just below the apex there is a very short groove marking where it interlocks with the tergum; median latus smooth; carina and rostrum smooth, except for fine growth lines in apical region where plate extends beyond capitulum.

Labrum with row of very small teeth; mandibles moderately stout, with large superior tooth and two wellformed, lower teeth with spines, inferior angle with terminal spines arranged as cone; first maxillae (maxillules) hatchet-shaped, densely covered with setae; second maxillae large, with moderately flat cutting edge possessing abundant spines ( Figure 2 B); cirri long ( Table 3), filamentous, delicate; cirri I and II with robust proximal segments ( Figure 3 A,B); intermediate segments of cirrus VI with three pairs of long simple setae. Caudal appendages small, blunt, uni-articulate, a little under half length of basal segment of pedicel of cirrus VI ( Figure 3 C); penis with short, fine, terminal setae.

Remarks. The ratios of capitulum to peduncle length are provided in Table 1 , and demonstrate that the ratio, although falling within a range from 1:1 to 1:2·86 appears to be independent of size ( Table 2). Yamaguchi et al. (2004) carried out some extensive biometrics that appear to distinguish A. seepiophila from other neolepadines. Analysis of the variable capitular plates of A. kermadecensis (see Plate 1), suggests that ratios between capitulum length and width, and the degree of carinal curvature are unlikely to be a valuable distinguishing feature for this taxon – either between the two known species of Ashinkailepas or Neolepas species. Ashinkailepas is readily distinguished from other neolepadines by the short, curved peduncle, ornamented capitular plates and large rostrum. Although A. kermadecensis sp. nov. closely resembles A. seepiophila , it may be distinguished by its more heavily sculpted capitulum. The tergum of A. kermadecensis sp. nov. also lacks the central flat apico-basal platform and is proportionately slightly more elongate than A. seepiophila . In adult A. seepiophila , the apices of the scutum extend beyond the tergal basi-occuldent angle – this has not been observed in adult? A. kermadecensis . Although cirrus I is similar in both taxa, cirrus II is apparently longer and more filamentous in A. kermadecensis . Nonetheless, the trophi (labrum, palps, mandibles, first and second maxillae), cirri and caudal appendages conform to those of most vent barnacles (see Yamaguchi et al., 2004).

Ashinkailepas kermadecensis sp. nov. has been recovered from the same region as another neolepadine, Vulcanolepas osheai ( Buckeridge, 2000) , which occurs in very large numbers near hydrothermal vents at 34º52’S, 179º04’E (between 1313–1645 metres). Vulcanolepas osheai possesses unornamented capitular plates and a longer peduncle with very much smaller, non-protruding scales.

appearance of having been bitten off (predation?)

cirrus Dissected paratype from NIWA-18008 (Plate 1 Figure 2 ). Capitulum length 20.5 mm. anterior ramus posterior ramus

I 27 28

II 35 41

III 40 56

IV 53 51+

V 60 51+

VI 27 + 63+

c.a. 1 1

Figures

FIGURE 1. Ashinkailepas kermadecensis Buckeridge sp. nov. Paratype NIWA- 18008 (Plate 1: Figure 1). Capitulum comprising eight approximate, calcareous plates: carina (c), rostrum (r) and paired terga (t), scuta (s) and medial latera (ml); is = imbricating scale of the peduncle; oa = occludent angle of tergum. Note the broadly arched profile of the carina, and on the tergum, the weak longitudinal ridge on the scutal side that extends to a point near the apex of the medial latus.

FIGURE 2. Ashinkailepas kermadecensis Buckeridge sp. nov. Trophi. A: Left mandible; B: Left second maxilla; C: Labrum with palps (setae not shown).

FIGURE 3. Ashinkailepas kermadecensis Buckeridge sp. nov. Appendages (setae not shown). A: Cirrus I; B: Cirrus II; C: Basal segment of cirrus VI, showing short, blunt, uniarticulate caudal appendage at base.

Tables

TABLE 1. Ratios of capitulum length to peduncle length in Ashinkailepas kermadecensis Buckeridge sp. nov. Although specimens of A. kermadecensis nov. with a capitulum length of less than 14 mm are juveniles, they nonetheless demonstrate an ontogeny wherein peduncle growth follows that of the capitulum.

capitulum	peduncle	C: P Ratio
3.5 4.0	1.5 1.4	2.33 2.86
5.0	4.0	1.25
8.5 9.0	3.0 7.0	2.83 1.29
10.5	4.5	2.33
13.0 14.0	8.5 7.0	1.53 2.00
14.8	8.5	1.74
15.0 16.0	6.5 12.5	2.31 1.28
16.5	15.0	1.10
18.5 18.8	14.5 8.8	1.28 2.14
19.0	9.5	2.00
19.0 20.5	12.5 9.5	1.52 2.16
20.5	17.0	1.21