Heteralepas newmani, Mifsud, Constantine, 2017

Mifsud, Constantine, 2017, A new pedunculate barnacle (Cirripedia: Heteralepadidae) from the Mediterranean with notes on reproduction, Zootaxa 4319 (3), pp. 561-578 : 566-576

Heteralepas newmani sp. nov.

( Figs 2–5 )

Type material. The holotype (specimen A), two paratypes (specimens B and C), all from which DNA sequences were obtained, and their complemental males, are deposited in the Museum of Natural History, Mdina, Malta, collection number NMHMC 040a.

Etymology. Named in honor of the American cirripedologist, William A. Newman, who has devoted a large part of his scientific life to studies of the natural history, systematics, and taxonomy of recent and fossil cirripeds.

Material. Twenty-six specimens were found in 2008 attached to a derelict nylon mooring line at 100 – 150 m depth in the Mediterranean Sea off Malta at 35°51.315’ N, 14°11.707’ E ( Fig. 1 , Table 3 ). The line was anchored in ~ 458 m depth, with its upper end drifting with the currents in the water column. The line became entangled with a fisherman’s bottom long lines and was brought up as by-catch; the barnacles were attached at the "top" of the line, corresponding to 100 – 150 m depth, among a large colony of the hydroid Sertularia gayi (Lamouroux, 1821) and a few specimens of Scalpellum scalpellum (Linnaeus, 1767).

Diagnosis. Capitulum ovoid, surface somewhat roughened, without tubercles, carinal ridge or indications of insertions of carapace adductor muscle present; aperture length ~one-half height of capitulum, with crenulate or flaring lips. Peduncle wrinkled. Capitulum 1.6–2.2 times longer than peduncle.

Description. Medium-sized species, total length 1.0– 2.3 cm; peduncle short relative to capitulum (latter 1.6– 2.2 times longer); distinct demarcation between capitulum and peduncle ( Fig. 1 , Tables 2–4); peduncular length 0.32–0.88 cm, width 0.33–0.58 cm; capitular length 0.7–1.38 cm, width 0.62–1.24 cm. Capitulum globular, surface rugged; some specimens colonized by hydroids and foraminifera ( Fig. 2 B ). Aperture half height of capitulum, crenulated, flaring from side. Area below aperture swollen in chin-like fashion, protrusions or clear carinal ridge not evident. Mouth parts typical for Heteralepas species ( Fig. 3 ). Mandible ( Fig. 3 A–C ) with 4 teeth including inferior angle; surface covered with numerous fine setae; lower margins of teeth 1–3 pectinate (with 5–7 short, stout spines under first and second teeth, 3 under third, more rounded teeth on the margin beneath fourth tooth). First maxilla ( Fig. 3 D, E ) with notched cutting edge, 3 major spines and ~15 lesser spines below notch, 2 clumps of fine setae along superior margin, similar setae along inferior margin, lateral surfaces clothed with numerous fine setae. Labrum with pectinations along margin (fig 3F).

Number of cirral segments varying substantially with size of hermaphrodite ( Table 5: three specimens, 1.02, 1.33 and 2.26 mm total length, respectively). Cirrus I not separated from more posterior cirri, modified as maxilliped, rami relatively short, unequal, densely setose ( Fig. 4B ). Cirri II–VI similar in structure, setation ctenopod ( Fig. 4 ). Cirri II–IV with long, subequal rami subequal to outer rami of cirri V and VI. Inner rami of cirri V and VI atrophied, shorter than outer rami, with fewer than half number of segments of outer rami (cirrus V, inner ramus 18–28 segments, outer with 48–78 segments; cirrus VI, inner ramus with 15–22 segments, outer ramus 41– 72).

Caudal appendages with 10–12 articles. Penis annulated, without specialized hooks or grapples, clothed distally with numerous long, fine setae (fig 5).

Molecular analysis. Comparison of the sequences of the COI and S12 genes from three of the present type specimens of H. newmani sp . nov. (A, B, C; Tables 3 , 4) with corresponding sequences from H. japonica revealed calculated p-distances of 15% and 8% respectively, compared to a within species p-distance for H. newmani sp nov. of <0.1%. Chan et al. (2009) reported p-distances for COI and S12 of <2.2% within species and divergences of>8% between species for Heteralepas japonica and H. canci Chan et al., 2012 .

SP A SP B SP C Capitulum Width (cm) 1.24 0.75 0.62

Length (cm) 1.38 0.99 0.70 Peduncle (P) Width (cm) 0.58 0.39 0.33

Length (cm) 0.88 0.34 0.32 C+P 2.26 1.33 1.02 C/P 1.57 2.87 2.20 Aperture (A) Length (cm) 0.64 0.52 0.37 A/C 0.46 0.53 0.53 Cirrus I Inner ramus 12 13 11 Articles Outer ramus 22 27 17 Cirrus II Inner ramus 45 42 41 Articles Outer ramus 48 51 47 Cirrus III Inner ramus 56 50 47 Articles Outer ramus 61 52 50 Cirrus IV Inner ramus 52 47 41 Articles Outer ramus 73 51 45 Cirrus V Inner ramus 18 26 18 Articles Outer ramus 75 48 43 Cirrus VI Inner ramus 19 22 14 Articles Outer ramus 72 51 41

Caudal appendage 12 10 10 Reproduction. This species has both large hermaphrodites and small complemental males, the latter found on 35% of the hermaphrodites ( Figs 6–8 , Table 3 ). The males resemble minute hermaphrodites and range from 1.2 to 4.47 mm in total length, with the peduncle clearly shorter than the capitulum. In one male, article counts of the inner and outer rami of Cirri V and VI were 5 and 22, respectively, of both limbs.

Of the 15 males, 11 were attached below the aperture and two above, with the remaining two found just inside the lower part of the aperture. In general, one male was found attached to one hermaphrodite, but a maximum of four were observed on the largest specimen. Hermaphrodites with males had a capitular length of> 0.75 cm. One hermaphrodite bore a not-yet-metamorphosed, 1.1 mm long, presumably male, cypris larva ( Fig 9 ).

Based on the presence of eggs and complemental males, hermaphrodites with a capitular length of <0.7 cm are likely juveniles ( Table 3 ). Seven of the hermaphrodites with capitula of>1.0 cm in height had eggs or egg masses, with eggs size ranging from 0.16– 0.61 mm.

Parasite. Eight specimens of a parasitic epicaridean isopod were removed from the mantle cavity of one of the hermaphrodites (Paratype C) ( Fig. 10 ). Two males and six females in different stages of maturity were attached to the barnacle by their heads, with the exception of one female that had recently metamorphosed and which was attached by a pair of slender periopods, comparable to those illustrated for Proteolepas bivincta Darwin, 1854 (q.v., Pl. 24, Fig. 7 ) found on Heteralepas cornuta ( Darwin, 1852) from the West Indies. Based on these limbs, Darwin (1854) concluded that Proteolepas was a barnacle, but Newman (1962; 1967) suggested it was more likely a copepod or an epicaridean isopod. Bocquet-Védrine (1972) found a comparable form on the balanomorph Perforatus perforatus (Bruguière, 1789), from the coast of France, and she and her husband not only demonstrated that it was attached to the host by its second periopods, but also that it belonged to the Crinoniscidae Bonnier, 1900 ( Bocquet-Védrine & Bocquet 1972). Hosie (2008) subsequently described Crinoniscus cephalatus from the mantle cavity of the scalpellomorph Amigdoscalpellum costellatum (Withers, 1935) from New Zealand. He mentioned that the second periopods of an immature female are “extremely elongate ‘guy-lines’ up to as long as the body”. But while relatively long in the mature female (c.f. his Fig. 4A, B ), the second periopods in both illustrations are by no means as slender as in Proteolepas and in our new form from the Mediterranean. In passing, it needs to be noted here that Williams & Boyko (2012) were not convinced P. bivincta was an epicaridean and dubbed it nomen dubium. A more complete report concerning the present isopod, which is likely a new species of the genus Crinoniscus , is intended for publication elsewhere.

Taxonomic discussion. The possession of atrophied inner rami on cirri V and VI is the principal diagnostic feature of Heterolepas s. s. Of the 28 formerly described species of Heteralepas , none has been recorded in the Mediterranean Sea (Table 1). This genus is generally difficult to identify to species level since, unlike most other stalked cirripeds, it lacks the calcified valves that aid identification in other genera. Thus, the main characters available to discriminate the species of this genus are the relative proportions of the capitulum, peduncle and aperture, in addition to the sculpturing of the capitulum and aperture and the number of segments in the cirri. The mouthparts are generally very morphologically similar in all the species of this genus.

Zevina (1982) divided Heteralepas into two groups, those with the peduncle obviously longer than the capitulum and those with the peduncle shorter. Caution needs to be exercised here because peduncular length is likely to be influenced by age as well as the strength and direction of prevailing currents. However, for H. newmani sp . nov., the relationship between length of the peduncle and the capitulum is near linear ( Fig. 8 ) and thus it apparently belongs to the latter group ( Fig. 1 , Table 2). Based on its overall size, the relative length of the peduncle (1.2–2.9 times shorter than the capitulum), the length of the aperture relative to the capitulum (one-half), the lack of protrusions, scutal marks or depressions, or a carinal ridge on the capitulum, and the number of segments of cirri V and VI, the only reasonable matches among the previously described species are H. malaysiana Annandale, 1905 and H. fessa Zevina & Schreider, 1992 (see Table 2 for morphological comparisons). In addition to both species being known only from the Indo-West Pacific, both have a weak carinal ridge, unlike H. newmani and, additionally, H. malaysiana has wart-like protrusions. Neither species is well described morphologically; however, by thoroughly comparing the morphology of H. newmani sp . nov. with existing species in the genus (Table 2), we conclude that it is clearly different from all formerly described species.

Comparison of the sequences from three of the present type specimens of H. newmani sp . nov. (A, B and C; Tables 3 , 4) with corresponding sequences from H. japonica available in GenBank® revealed calculated pdistances of 15% and 8% respectively, compared to a within species p-distance for H. newmani of <0.1%. Chan et al. (2009) reported p-distances for COI and S12 of <2.2% within species and divergences of>8% between species of Heteralepas . The present limited molecular data support the morphology-based conclusion that Heteralepas newmani sp. nov. represents a previously undescribed species.

Figures

FIGURE 1. Map showing the locality where 26 specimens Heteralepas newmani sp. nov. were a nylon line anchored in about 458 m depth was brought up as a by catch on a fisherman’s bottom long lines. The line was drifting with the currents in the water column, and specimens were attached at the " top " of the line corresponding to 100 - 150 m depth.

FIGURE 2. Detailed morphological description Heteralepas newmani sp. nov. is based on specimens A, B, and C in figure A, B and C (see also Table 4) all to same scale.

FIGURE 3. Heteralepas newmani sp. nov., mouth parts from species A (Table 4). A, Mandible; B, pectination of first tooth; C, pectination of teeth 2 - 3; D-E: First maxilla, F; Labrum with pectinations. Scale 500 mm replies to A, D & F.

FIGURE 4. Heteralepas newmani sp. nov., (specimen A): A, Prosoma and thorax with appendages; B, cirrus I; C, cirrus II; D, cirrus V; E, cirrus VI (See also table 4 and 5).

FIGURE 5. Heteralepas newmani sp. nov.,: A, caudal appendages between pedicels of the 6 th cirri (species A); B, penis (species 3) (See also tabel 4 and 5).

FIGURE 6. Heteralepas newmani sp. nov. (specimen 5) with two complemental males, and below (specimen 4) with one male. The complemental male is typically sitting below the aperture of the hermaphrodite (see also Table 3 and Fig 7). Scale lower right = 1 mm.

FIGURE 7. The position of Heteralepas newmani sp. nov. (specimen RS 3, Table 3) on a nylon mooring line with a 4.5 mm long complemental dwarf male attached below aperture. Inside the same specimen are hundreds of eggs resembling cyprids that could indicate a direct development to cyprids without a free nauplius stage.

FIGURE 8. Near linear relationship between length of the peduncle and the capitulum. The occurrence of complemental males on the hermaphrodite of Heterealepas newmani sp. nov. in relation to length of peduncle and capitulum. Triangle indicates presence of complemental male and number of males is provided when> 1.

FIGURE 9. Complemental male of Heteralepas newmani sp. nov. Above metamorphosing cyprid still within cyprid shell found attached to specimen 3, and below whole male.

FIGURE 10. The isopod parasite (Crinoniscidae) found in the mantle cavity of Heteralepas newmani sp. nov. (specimen C, Table 2) resembles Proteolepas Darwin, 1854, a genus recognized by Hosie (2008). The specimens illustrated include six females in different stages of maturation and two males (lower left; Hosie in litt. Hosie, 2017). Upper right, a maturing virtually legless recently molted female attached to host tissue by its long very slender second pereiopods. These males and females are morphologically similar to those of Crinoniscus (Hosie in litt. 2017). Proetolepads bivincta Darwin, 1854 was found on Heteralepas cornuta Darwin, 1851 from the West Indies, but now also known in the Atlantic from the NW Africa north to the mouth of the Mediterranean. Therefore, it is important to note that Darwin’s H. cornuta is clearly distinct from the new species, H. newmani (see text).