Zootaxa 3972 (3): 328–342 ISSN 1175-5326 (print edition) www.mapress.com/zootaxa/ Article ZOOTAXA Copyright © 2015 Magnolia Press ISSN 1175-5334 (online edition) http://dx.doi.org/10.11646/zootaxa.3972.3.2 http://zoobank.org/urn:lsid:zoobank.org:pub:8C688C67-9652-4DB7-8640-E1BA37EB76EC Gorgonolaureus bicornutus sp. nov (Crustacea: : ) from off South-East Taiwan with notes on morphology and distribution

GREGORY A. KOLBASOV1,4, BENNY K.K. CHAN2 & ALEXANDRA S. PETRUNINA3 1White Sea Biological Station, Biological Faculty, Moscow State University, 119991, Moscow, Russia. E-mail: [email protected] 2Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan. E-mail: [email protected] 3Invertebrate Zoology Department, Biological Faculty, Moscow State University, 119991, Moscow, Russia. E-mail: [email protected] 4Corresponding author. E-mail: [email protected]

Abstract

A new ascothoracidan species, Gorgonolaureus bicornutus sp. nov., has been discovered off south-eastern Taiwan at a depth of 227 m. Five females were found in permanent cysts on the branches of a plexaurid octocoralian alcyonacean (for- mer “gorgonian”), Echinogorgia sp. These specimens are assigned to the genus Gorgonolaureus on account of their hav- ing an enlarged and inflated carapace with a long, slit-like aperture, long dorsal thoracic horns, no filamentary appendages associated with the first pair of thoracopods, and rudimentary telsonic spines. Gorgonolaureus bicornutus differs from its congeners in having two long, naked dorsal horns on thoracomeres 2 and 3, the number of seminal receptacles in the tho- racopods, and the higher number of stout setae on the fifth antennular segment. The characters that unite the genus Gor- gonolaureus are redefined as follows: i) the absence of filamentary appendages associated with the first pair of thoracopods; ii) the possession of 1–3 dorsal horns distributed singly among thoracomeres 1–3; iii) the absence of prom- inent proximal teeth medially on the mandibles; iv) the possession of short or rudimentary telsonic spines; and v) host pref- erence, with most species infecting octocorals of the suborder Halaxonia (mostly of the family Plexauridae) and never the calcaxonian families Chrysogorgiidae and Isididae. The gorgonian-infecting genera Gorgonolaureus and Isidascus are Tethyan relics that have survived only in the Western Pacific and the Eastern Atlantic, respectively, while their relatives in the genera Cardomanica and Thalassomembracis have disjunct Western Atlantic/Western Pacific distributions, thus ex- emplifying a major pattern of Tethyan reliction.

Key words: Gorgonolaureus, Ascothoracida, , morphology, distribution

Introduction

Species of the genus Gorgonolaureus Utinomi, 1962 together with the genera Isidascus Moyse, 1983, Cardomanica Lowry, 1985, Thalassomembracis Grygier, 1984, and probably Flatsia Grygier, 1991, represent a more advanced grade of morphological organization in the adult females of synagogid ascothoracidans compared with the most generalized (primitive) fully bivalved genera Synagoga Norman, 1888, Waginella Grygier, 1983 and Sessilogoga Grygier, 1990. Gorgonolaureus parasitizes colonies of halaxonid and calcaxonid octocoralian alcyanaceans (former gorgonians). The parasite is encapsulated and covered directly by a number of adjoining host polyps, forming a cyst. The inner body of Gorgonolaureus resides in an enlarged carapace with a slit-like ventral aperture. The adult stages have six-segmented, prehensile antennules and piercing mouthparts (especially maxillae). The dorsal sides of thoracomere 2, and sometimes thoracomeres 1 and 3, bear long dorsal horns. As in most Ascothoracida, these are dioecious species with large attached females and small motile cypridiform males, but these are described only for two species, G. muzikae Grygier, 1981 and G. tricornutus Grygier, 1991 (Grygier, 1981, 1991). Grygier (1981) originally interpreted these males as ‘protanders’, but later reinterpreted them as gonochoristic adult males (Grygier, 1987b). The true dioecious species of other ascothoracids of the order Dendrogastrida having large modified females accompanied with dwarf cypridiform males have a different morphology of the ‘male’ and ‘female’ cypridiform larvae. However, the cypridiform larvae of Gorgonolaureus, as

328 Accepted by D. Jones: 11 May 2015; published: 12 Jun. 2015 well as lower synagogids have not been studied. In light of this observation, it appears that until the morphological differences between putative ‘males’ and ‘females’ have been discerned, life histories (protandric and/or dioecious) among the lower Ascothoracida will remain unclear. At least five naupliar instars have been reported for G. muzikae and G. decurvatus and three naupliar instars for G. vietnamianus, based on retained naupliar molts carried by brooded larvae inside the carapace chamber of the females (Grygier 1981a, 1981b, 1987a, 1991). Gorgonolaureus muzikae has been noted to be frequently infected by hyperparasitic cryptoniscoid isopods (Grygier 1981b). Six species of the genus Gorgonolaureus were described previously from the tropical waters of the Pacific Ocean and north-western Australia (Fig. 8). These are G. bikiniensis Utinomi, 1962 collected off Bikini Atoll, Marshall Islands, depth 213–221 m, from the gorgonian Paracis squamata (Utinomi 1962; Grygier 1981a); G. muzikae Grygier, 1981 from Hawaii, depth 326–460 m, from the gorgonians Placogorgia sp. and Astromuricea sp. (Grygier 1981b, 1987a, 1987b); G. decurvatus Grygier, 1991 off north-western Australia, depth 90–98 m, from the gorgonian Pterostenella plumatilis; G. vietnamianus Grygier, 1991 from South Vietnam, depth 83 m, from the gorgonian Placogorgia sp.; G. tricornutus Grygier, 1991 from New Caledonia, depth 640 m, from the gorgonian Eunicella sp. (Grygier 1991); and G. helenae Kolbasov, 2004 off South Vietnam, depth 120, from a gorgonian of the family Plexauridae (indicated as Paramuriceidae) (Kolbasov 2004). A new species, G. bicornutus, was collected off south-eastern Taiwan, depth 227 m, from the gorgonian Echinogorgia sp.that differs morphologically from all congeners described previously. This is the first finding of Gorgonolaureus in Taiwan and the fifth record of any kind of ascothoracidans from Taiwan or Taiwanese waters, including three unidentified petrarcid galls in scleractinian Turbinaria species from southern Taiwan and Lanyu Island (Grygier, 1991), and an undetermined laurid, Baccalaureus sp., from the zoanthid Palythoa sp. (Grygier, 1996).

Materials and methods

A large colony of plexaurid octocoral was collected by deep sea coral trawling boat in Bashi Channel off south- eastern Taiwan (Fishing Boat “Shun-Yi”). The colony was fixed with absolute ethanol and deposited in the collections of the Coastal Ecology Laboratory of the Biodiversity Research Center, Academia Sinica, Taiwan. Six ascothoracidan cysts covered by living polyps were found in the colony. One cyst was empty but the other five contained living parasites (Fig 1A). Three specimens were studied with light microscopy (holotype) and SEM (two paratypes). Polyp tissues were removed from the parasite carapace by forceps and needles (Fig. 1B). The photos of the cysts and the carapace were made using a stereomicroscope Leica MZ 6. The carapaces of the holotype and two paratypes were dissected to observe the morphology of the body and its structures. The dissected holotype was mounted in glycerol on glass slides and examined using a WILD M 20 light microscope. Line drawings were made using oil immersion with an Olympus BX 51 microscope with Nomarsky differential interference contrast microscopy. Two dissected paratypes were post-fixed in 2% OsO4 for 2 hrs, dehydrated in acetone and critically point dried from CO2, sputter-coated with platinum–palladium and examined in a JEOL JSM-6380LA scanning electron microscope at operating voltages of 15–20 kV at the University of Moscow. The resulting photographs were touched up using a CorelDraw X3 Graphics Suite.

Taxonomy

Class Thecostraca Gruvel, 1905

Subclass Ascothoracida Lacaze-Duthiers, 1880

Order Laurida Grygier, 1991

Family Synagogidae Gruvel, 1905

GORGONOLAUREUS FROM TAIWAN Zootaxa 3972 (3) © 2015 Magnolia Press · 329 Genus Gorgonolaureus Utinomi, 1962

Gorgonolaureus bicornutus sp. nov.

Type material. Six female specimens (holotype and 5 paratypes; no males found) in polyp-surrounded cysts on a single colony of an halaxonian alcyonacean (“gorgonian”) Echinogorgia sp. (Plexauridae; determined by Prof. T.N. Molodstova) in a jar from the collections of the Coastal Ecology Laboratory, Biodiversity Research Center, Academia Sinica, Taiwan, collected at 21º11’43.3’’ N, 120º51’47.3’’ E, depth 227 m, Bashi Channel, south-eastern Taiwan, and fixed in absolute ethanol. The holotype and 4 paratypes are deposited in the Zoological Museum of Moscow State University under registration numbers Mg. 1220 (holotype) and Mg. 1221 (paratypes). The other paratype (no. ASIZCR000327) is deposited in the Biodiversity Research Museum, Biodiversity Research Center, Academia Sinica, Taiwan. Diagnosis. Carapace of adult female 2.7–3.0 mm height, length 70–80% height; covered with simple and multifid teeth, anterior part of aperture with edge straight, posterior with edge scalloped. Two long, naked, dorsal horns on second and third thoracomeres. Fifth antennular segment with 14–16 stout spinulose setae; sixth segment without spines of surfaces; claw guard with 4 thick aesthetasc-like terminal setae; proximal sensory process distinctly separated from claw guard, with 3 thick aesthetasc-like terminal and one short sub-terminal setae. Maxillae with bifid, harpoon-shaped tips. Thoracopods II–V each with 3 seminal receptacles. Telsonic spines rudimentary. Furcal rami without spines or teeth; ventral margin not recurved; with 3 terminal and 3 subterminal setae on distal end. Description of female (based on holotype and paratypes Mg. 1221). Carapace milky-grey in alcohol; univalved with curved, slit-like ventral aperture along midline (Figs 1, 2A–C), upper dorsal part with spherical brood chamber larger than lower ventral part (Figs 1C, 2B, 5A). Carapace with three inflations on ventral side smaller than brood chamber, one postero-ventral (hillock with aperture, Figs 1B, 2 A, C) and two mid-ventral laterally to aperture (Figs 1D, 2C). Dimensions of carapace (holotype): height 3.0 mm, length 2.3 mm, maximum width (at top) 2.16 mm, isthmus (just below globular dorsal part) 1.13 mm. Aperture long, single (no separate aperture for oral cone), with thickened margins, anterior half with straight margin (Figs 1D, 2C), posterior half with scalloped interlocking margins (Figs 1C, 2B). External surface of carapace covered with cuticular teeth, rare and simple on lateral sides, dense and multifid on postero ventral hillock with scalloped aperture (Figs 1D, 5D). Lateral sides of carapace without noticeable gut and ovarian diverticula (Figs 1B, 2A). Internal surface of carapace mantle in postero-ventral area covered with dense, ctenoid scales consisting of 10–20 long, thin denticles, 10–25 μm in length, underlain by row of long, thin, simple setae near valve margin, tiny and rare pores found between ctenoid scales (Fig. 5B, C). Body attached antero-ventrally by adductor muscle, occupying ventral third of carapace chamber (Figs 2D, 5A). Oral cone situated opposite anterior part of aperture, covered by host tissue; thorax with thoracopods and abdomen with furcal rami lie opposite to free, posterior, scalloped part of aperture. Length of body (anterior-most part to tips of furcal rami) 2.19 mm (holotype Fig. 2D), 1.86 mm (paratype Fig. 5A). Body consisting of head with prehensile antennules and prominent oral cone on ventral side, followed by 6 thoracic segments with 6 pairs of biramous thoracopods, and 5-segmented abdomen, including telson with a pair of furcal rami. Size of thoracomeres gradually decreasing from first to sixth (Figs 2D, 5A). Transverse band of setae absent on anterio-dorsal side of first thoracic segment. Two long, naked, dorsal horns ~1.3–1.4 mm length, slightly curved posteriorly, on second and third thoracic segments (Figs 2D, 5A). Feeble ctenoid scales cover all surfaces of trunk somites (Fig. 5G). Sixth thoracic segment bearing pair of latero-ventral, drop-like epaulets ~150 μm length, with dense, sharp, cuticular protrusions in distal bulbous part (Fig. 5E, F). Prehensile antennules 6-segmented, Z-shaped when folded, tips reaching to mid-length of oral cone (Fig. 2D– F). First segment massive, irregularly-shaped, almost lacking setae; second segment short, trapezoidal, with tuft of thin setae on anterior (preaxial) edge; third segment subtriangular, with row of thin setae along anterior edge; fourth segment short, trapezoidal, with 5–6 stout, spinulose setae on anterior edge; fifth segment elongate, 210 µm long, sub-rectangular, with 14–16 stout, spinulose seate along curved anterior edge, several pairs of small, thin setae on distal half of straight posterior edge. Sixth segment slightly shorter than fifth, with slightly curved posterior and recurved anterior edges, several tufts of small, thin setae on posterior edge; both segments spineless, lateral surfaces bearing feeble ctenoid scales (Figs 2E, F, 6A). Robust, curved claw with smooth surface inserted

330 · Zootaxa 3972 (3) © 2015 Magnolia Press KOLBASOV ET AL. distally on sixth segment; 3 short, thick setae at base of claw, 1 each on outer and inner sides, 1 on anterior edge of segment (Figs 2E, F, 6A, B). Claw guard cylindrical, ~50–60 µm long, inner surface with flange, bearing 4 thick, aesthetasc-like terminal setae (Figs 2E, F, 6A, B). Proximal sensory process same size as but distinctly separated from claw guard, with 3 thick, aesthetasc-like terminal setae and 1 short, sub-terminal seta (Figs 2E, F, 6C). Oral cone triangular with elongated distal part (Figs 2D, 3C), formed by large labrum surrounding mouthparts (Figs 3A, 6D). Labrum with mid-line posterior suture corresponding to its lateral margins (Fig. 6D), proximal part wide, inflated, distal tip narrow, sharp (Fig. 6E), lateral surfaces with feeble ctenoid scales (Fig. 6F). Mouthparts grouped together, maxillae longest (Fig. 6G). Medial languette elongated, tongue-shaped, with pointed distal part covered by row of setae, 2 rows of setae along anterior (outer) edge at middle and proximal parts (Fig. 3I). Mandibles (Fig. 3B–D) with broad basal part, and narrow, sharply pointed distal tip; lateral (outer) edge with

FIGURE 1. Gorgonolaureus bicornutus sp. nov., general appearance, light microscopy, female, holotype. (A) Gorgonian cyst with parasite in situ, left side, lateral view (free margins of aperture ‘ap’ indicated with arrow). (B) Carapace on gorgonian rod, right side, lateral view (soft polyp tissue removed). (C) Carapace, posterio-ventral view. (D) Carapace, anterio-ventral view. Abbreviations: ap—aperture of carapace. Scale bars in µm.

GORGONOLAUREUS FROM TAIWAN Zootaxa 3972 (3) © 2015 Magnolia Press · 331 FIGURE 2. Gorgonolaureus bicornutus sp. nov., general appearance and antennules, female, holotype. (A) Carapace, lateral view. (B) Carapace, posterio-ventral view. (C) Carapace, anterio-ventral view. (D) Position of inner body proper inside carapace, lateral view (left valve of carapace removed, thoracic segments numbered in Roman). (E) Right antennule, lateral view (segments numbered). (F) Left antennule, distal segments 4–6, lateral view. Abbreviations: a1—antennule, ab— abdomen, ad—adductor muscle, ap—aperture of carapace, cg—claw guard, cl—claw, dh—dorsal horns, fr—furcal rami, oc— oral cone (oral pyramid), ps—proximal sensory process, thp1–6—thoracopods 1–6. Scale bars in µm.

332 · Zootaxa 3972 (3) © 2015 Magnolia Press KOLBASOV ET AL. FIGURE 3. Gorgonolaureus bicornutus sp. nov., mouth parts, female, holotype. (A) Oral cone, front view. (B, C) Mandibles. (D)—Enlarged cutting edge of mandible. (E, F) Maxillules. (G) Maxillae. (H) Enlarged distal ends of maxillae. (I) Medial languette. Abbreviations: lb—labrum, md—mandible, mxI—maxillule, mxII—maxilla. Scale bars in μm.

GORGONOLAUREUS FROM TAIWAN Zootaxa 3972 (3) © 2015 Magnolia Press · 333 FIGURE 4. Gorgonolaureus bicornutus sp. nov., thoracopods (numbers on B–D correspond to thoracopodal setation in Table 1), furcal ramus, rudimentary penis, female, holotype. (A) Right thoracopod 1, front view. (B) Right thoracopod 2, front view. (C) Right thoracopod 3, rear view. (D) Right thoracopod 4, rear view. (E) Right thoracopod 5, rear view. (F) Right thoracopod 6, front view. (G) Left furcal ramus, outer side. (H) Distal end of right furcal ramus, inner side. (I) Rudimentary penis (dotted) on ventral side of first abdominal segment (ab1). Abbreviations: ab1—first abdominal segment, ba—basis, co—coxa, en— endopod, ex—exopod, sr—seminal receptacles in coxae. Scale bars in µm.

334 · Zootaxa 3972 (3) © 2015 Magnolia Press KOLBASOV ET AL. FIGURE 5. Gorgonolaureus bicornutus sp. nov., ultrastructure of carapace and body proper (SEM), female, paratype. (A) Inner body proper inside carapace, lateral view (left carapace valve removed). (B) Inner surface of posterio-ventral part of carapace and distal halves of furcal rami. (C) Enlarged part of mantle cuticle on inner surface of posterio-ventral part of carapace (tiny pores indicated by arrowheads). (D) Multifid teeth on external surface of carapace at posterio-ventral edge of aperture. (E) Posterior part of thorax (segments numbered in Roman) with abdomen (segments numbered in Arabic). (F) Lateral epaulet on sixth thoracic segment. (G) ventral surface of third abdominal segment. Abbreviations: ab—abdomen, ad— adductor muscle, ap—edge of aperture, dh—dorsal horns, ep—epaulet, fr—furcal rami, te—telson, thp1–6—thoracopods. Scale bars in µm.

GORGONOLAUREUS FROM TAIWAN Zootaxa 3972 (3) © 2015 Magnolia Press · 335 FIGURE 6. Gorgonolaureus bicornutus sp. nov., ultrastructure of antennules and oral cone (SEM), female, paratype. (A) Sixth antennular segment, outer surface (arrowheads indicating ctenoid scales). (B) Claw and claw guard of sixth antennular segment, inner surface. (C) Proximal sensory process. (D) Labrum, forming oral cone, rear view (closed rear margins of labrum indicated by arrowheads). (E) Enlarged tip of labrum from ‘D’. (F) Ctenoid scales on surface of labrum from ‘D’. (G) Mouth parts. Abbreviations: cg—claw guard, cl—claw, md—mandible, mxI—maxillule, mxII—maxillae, ps—proximal sensory process. Scale bars in µm.

336 · Zootaxa 3972 (3) © 2015 Magnolia Press KOLBASOV ET AL. FIGURE 7. Gorgonolaureus bicornutus sp. nov., ultrastructure of furcal rami (SEM), female, paratype. (A) Distal ends of furcal rami with tuft of tick aesthetasc-like setae. (B) Posterior end of telson with proximal parts of furcal rami and rudimentary telsonic spine. (C) Furcal rami, external and internal sides. (D) Transverse rows of ctenoid scales on internal surface of furcal ramus. Abbreviations: fr—furcal rami, rts—rudimentary telsonic spine, te—telson. Scale bars in µm. several bands of few, long setae at basal part, row of long setae along distal tip; cutting (inner) edge with row of long setae, several noticeable multifid teeth in basal half, small sharp denticles in distal part. Maxillules (Fig. 3E, F) with broad base gradually narrowing to distal part, with blunt tip, row of dense, long setae along inner edge, row of thicker setae on outer edge in distal part. Long, piercing maxillae (Figs 3G, H, 6G) fused at bases, ~80% of their length free, lateral flanges in distal part, bifid harpoon-shaped tips. Thoracopods I and VI (Fig. 4A, F) cylindrical, smaller than others; thoracopods II–V flattened, size decreasing from II to V (Fig. 4B–E). Thoracopods covered by numerous fine setae, segments bearing large, plumose setae. Coxae longer than wide, extensively lined with fine setae along outer and inner margins of thoracopods II–IV (Fig. 4B–C) but only along inner margin of thoracopod I (Fig. 4A); tuft of fine setae at distal part of inner margin and row of fine setae along outer margin ofthoracopod V (Fig. 4E). Protopod of thoracopod VI lacking fine setae (Fig. 4F). Margins of bases of thoracopods I–V lined with fine setae. 3 elongated, ampoule-shaped seminal receptacles at outer margins of coxae of thoracopods II–V (Fig. 4B–E). Exopods 2-segmented, slightly longer than 3-segmented endopods of thoracopods II–V. Exopods of thoracopods I, VI significantly larger than 2-segmented endopods (Fig. 4A, F). Setation including large, plumose setae of holotype given in Table 1. Single lateral coxal seta (position 1) present in thoracopods II–IV (Fig. 4B–D), but medial coxal seta (position 9) found only in thoracopod III (Fig. 4C). Exopods having 5–7 setae on distal segments (position 4), endopods having 2–5 setae on distal segments.

GORGONOLAUREUS FROM TAIWAN Zootaxa 3972 (3) © 2015 Magnolia Press · 337 Table 1. Thoracopodal setation of holotype of Gorgonolaureus bicornutus sp. nov., numbers of positions indicated in Fig. 4, parentheses used in case of 2-segmented endopods. thoracopod/position 1 2 3 4 5 6 7 8 9

I — — — 5 2 (—) — —

II 1 — 1 6 3 1 — 1 —

III 1 — — 6 5 1 2 1 1

IV 1 — — 7 5 — 1 1 —

V — — — 6 5 1 1 1 —

VI — — — 7 5 (1) 1 —

Abdominal segments of different sizes (Fig. 5E), first largest, segments 3, 4 small and short, fifth segment (telson) with pair of terminal furcal rami. First segment with rudimentary, bifurcated penis, length ~240 µm, on ventral side (Fig. 4I). Penis with two smaller distal processes (each 100 µm length) on elongated proximal shaft (140 µm). Telsonic spines rudimentary (Fig. 7B). Furcal rami (Figs 4G, 5E, 7C) 310–350 µm length, triangular, with convex outer and concave inner surfaces, ventral margin not recurved. External surface with ctenoid scales along dorsal and ventral margins (Fig. 7B), field of dense, thin setae on lateral surface, denticles or teeth lacking (Figs 4G, 7B). Inner surface covered by dense transverse rows of ctenoid scales (Fig. 7C, D). Distal part of furcal ramus bearing group of 3 subterminal and 3 subterminal/medial thick setae covered by dense citicular villi, medial terminal seta longest (Figs 4H, 7A). Remarks. The main differences between all known species of Gorgonolaureus are indicated in Table 2 and, as will be noted, most of the species are characterized by the presence of a single dorsal horn on the second thoracomere. Only G. tricornutus from New Caledonia has two long and one short dorsal horn on thoracomeres 1– 3, respectively. The new species described in the present study differs from G. tricornutus in having only two long dorsal horns, and on thoracomeres 2 and 3, 14–16 stout setae on the fifth antennular segment, instead of the 5 in G. tricornutus, harpoon-shaped bifid tips of the maxillae (trifid and non harpoon-shaped in G. tricornutus), and by fewer seminal receptacles and furcal setae (Table 2). Two species G. vietnamianus and G. helenae are widely allopatric in the same region as G. bicornutus (Grygier 1991, Kolbasov 2004), from which it differs not only in having two dorsal horns instead of one, but also by the greater number of stout setae on the fifth antennular segment. It also differs from G. helenae by the bifid harpoon- shaped tips of the maxillae and the presence of 3 seminal receptacles in thoracopods II–V, and from G. vietnamianus in having 3 seminal receptacles in thoracopods II–V instead of 5–9, and by fewer furcal setae. Etymology. From the Latin bi- meaning two, and cornu meaning horn, in reference to the two thoracic horns.

Discussion

Taxonomy and morhopology. Grygier (1991) tentatively assigned G. tricornutus to Gorgonolaureus because it had several dorsal horns (one each on thoracomeres 1 to 3) instead of a single one on thoracomere 2 that is characteristic of most species of this genus. Adult females of other gorgonian-infesting ascothoracidans of the genera Isidascus Moyse, 1983 (one species) and Cardomanica Lowry, 1985 (three species) also possess three or four dorsal thoracic horns (Moyse 1983; Grygier 1984; Lowry 1985), but on thoracomeres 2–4 or 2–5, never on thoracomere 1 as in G. tricornutus, and no species of Gorgonolaureus has a horn posterior to thoracomere 3. Furthermore, the dorsal horns of Isidascus bassindalei Moyse, 1983 are relatively shorter but more massive than those of Gorgonolaureus species. All species of Gorgonolaureus lack the long filamentary appendages that are

338 · Zootaxa 3972 (3) © 2015 Magnolia Press KOLBASOV ET AL. present in both Isidascus and Cardomanica. Species of the latter two genera also have prominent proximal teeth medially on the mandible, which Gorgonolaureus species lack. Cardomanica species have long telsonic species that are comparable in length to the furcal rami, but these spines are short or rudimentary in all species of Gorgonolaureus. Females of Isidascus have a uniramous penis, but this organ is bifurcate in females of both Cardomanica and Gorgonolaureus.

FIGURE 8. Map of distribution of species of Gorgonolaureus and genera Thalassomembracis, Cardomanica and Isidascus: 1—G. bikiniensis, 2—G. muzikae, 3—G. decurvatus, 4—G. vietnamianus, 5—G. tricornutus, 6—G. helenae, 7—G. bicornutus, —Thalassomembracis, —Cardomanica, —Isidascus.

Species of Cardomanica and Isidascus infest octocorals of the suborder Calcaxonia, viz., species of the families Chysogorgiidae and Isididae, respectively. In contrast, most species of Gorgonolaureus have been found on octocorals of the suborder Halaxonia (mostly of the family Plexauridae), with only G. decurvatus infecting a species of the calcaxonian family Primnoidae (Table 2). Species of Gorgonolaureus never inhabit calcareous galls, as does Isidascus bassindalei, and they are encapsulated by a greater number of host polyps than are species of Cardomanica (Grygier 1991). One other synagogid genus, Thalassomembracis Grygier, 1984 consisting of 7 described species, also infests calcaxonians of the genus Chrysogorgia, but these ascothoracidans have special superficial grapnels on the carapace, an antero-ventral anchoring protrusion, a short carapace aperture, and fewer well-armed antennules in adult females than in species of the other three genera (Grygier 1984, 1990). The number of dorsal horns cannot be a firm taxonomical trait for Gorgonolaureus species, because species having a single horn do not form a distinct morpho-group through their other main morphological characters (see Table 2). The characters that may unite species of Gorgonolaureus are the following: i) the absence of basal filamentary appendages on thoracopod I; ii) 1–3 dorsal horns on thoracomeres 1–3, but no dorsal horn on thoracomeres 4 or 5; iii) no prominent proximal teeth medially on the mandibles; iv) short or rudimentary telsonic spines (in common with Isidascus); and v) the majority of species inhabit octocorals of the suborder Halaxonia (mostly family Plexauridae) but never the calcaxonid families Chrysogorgiidae and Isididae.

GORGONOLAUREUS FROM TAIWAN Zootaxa 3972 (3) © 2015 Magnolia Press · 339 Host Plexauridae (Holaxonia) Plexauridae (Holaxonia) Primnoidae (Calcaxonia) Plexauridae (Holaxonia) Plexauridae (Holaxonia) Gorgoniidae (Holaxonia) Plexauridae (Holaxonia) Distal setae of furcal ramus (1 long 3 terminal + 3 middle) subterminal/medial + 4-9 terminal short 4-5 medial (middle 3 terminal + 1 short) subterminoventral, 7-11 medial thin lost) rami ? (furcal 14-20 and 7-11 terminal medial setae + 18 6 terminal subterminal/medial + 4-5 11-13 terminal subterminal/ medial Number of of Number seminal receptacles of II-V thoracopods 3 2 usually 2, 1 occasionally 2, 4 10-20 at least 6-8 15 or (maybe more) 5-9 - - - - - Tips of of Tips maxillae bifid, harpoon shaped bifid, harpoon shaped bifid, harpoon shaped teeth trifid, not bent bifid, harpoon shaped teeth trifid, not bent bifid, harpoon shaped Position of proximal proximal Position of process sensory separateddistinctly claw guard from claw behind directly guard claw behind directly guard behind claw directly guard separateddistinctly claw guard from separatedslightly claw guard from separateddistinctly claw guard from th Gorgonolaureus Spines on 6 on Spines antennular segment absent absent present present present absent absent th Number of of Number setae stout 5 on antennular segment 14-16 5 7 6 11-12 5 7 s of of species the genus on on Dorsal horns Dorsal horns morphology and position 2 long naked dorsal horns on thoracomeres 2, 3 dorsal 1 long long with horn setae 2 thoracomere 1 long naked horndorsal on 2 thoracomere 1 long naked horndorsal on 2 thoracomere 1 long naked horndorsal on 2 thoracomere 1 and 2 long short naked dorsal horns on 1-3 thoracomeres 1 long naked with dorsal horn ctenaeminute on 2 thoracomere Main diagnostic character Main diagnostic Characters pecies G. bicornutus G. bikiniensis G. decurvatus G. helenae G. muzikae G. tricornutus G. vietnamianus S Table 2.

340 · Zootaxa 3972 (3) © 2015 Magnolia Press KOLBASOV ET AL. Geographical distribution. The genus Gorgonolaureus exclusively inhabits tropical seas (Fig. 8), ranging from the low sub-tidal to the upper bathyal zones (83–640 m). Six of the seven species of Gorgonolaureus are found in western and central parts, but not in the eastern part, of the Pacific Ocean, and only G. decurvatus is described from the eastern part of Indian Ocean adjacent to the Pacific (Fig. 8). Thus, the genus Gorgonolaureus has Indo-West Pacific or rather West Pacific distribution that is also characteristic for the most of barnacles (Darwin 1854). Its bathyal relatives of the genera Cardomanica and Thalassomembracis, inhabit gorgonians of the genus Chrysogorgia and have distinct West Atlantic/West Pacific distributions (Fig. 8). The genera Cardomanica and Thalassomembracis exhibit the major Tethyan reliction pattern that is also characteristic for some acrothoracican and bathyal thoracican barnacles (Newman & Ross 1971, Newman & Tomlinson 1974; Foster 1981; Kolbasov 2009), whereas the other gorgonian-infesting genera, Gorgonolaureus and Isidascus, represent Tethyan relics that consequently survived in the West Pacific and the East Atlantic. A remarkable disjunction by most any measure is the distinctly amphitropical distribution of Cardomanica (Fig.8).

Key to adult females of the species of the genus Gorgonolaureus

1a Single dorsal horn on second thoracomere ...... 2 1b Two or three dorsal horns on thoracomeres 1–3 ...... 6 2a Dorsal horn with long setae...... G. bikiniensis Utinomi 2b Dorsal horn without long setae ...... 3 3a Coxae of thoracopods II–V with 2–4 seminal receptacles, proximal sensory process directly behind claw guard ...... 4 3b Coxae of thoracopods II–V with more than 5–20 seminal receptacles, proximal sensory process distinctly separated from claw guard ...... 5 4a Coxa of thoracopod V with 2 seminal receptacles, free ends of maxillae bent, tips bifid, harpoon-shaped...... G. decurvatus Grygier 4b Coxa of thoracopod V with 4 seminal receptacles, free ends of maxillae straight, tips trifid ...... G. helenae Kolbasov 5a Fifth antennular segment with 11–12 stout setae along anterior edge, thoracopods II–V with 10–20 seminal receptacles...... G. muzikae Grygier 5b Fifth antennular segment with 7 stout setae along anterior edge, thoracopods II–V with 5–9 seminal receptacles...... G. vietnamianus Grygier 6a Thoracomeres 1, 2 with long and thoracomere 3 with short dorsal horns, tips of maxillae trifid, not bent ...... G. tricornutus Grygier 6b Thoracomeres 2, 3 with 2 long dorsal horns, tips of maxillae bifid, harpoon-shaped ...... G. bicornutus sp. nov.

Acknowledgements

We are indebted to Prof. T.N. Molodtsova for identification of the host. The authors would like to thank Dr Tze- Huen Tu and Dr Ming-Shou Jeng (Academia Sinica, Taiwan) for offering the octocoral colony collected by the fishermen. We are indebted to our anonymous referees for invaluable comments helped us to improve the manuscript. For GAK and ASP this work was financially supported by the Russian Foundation for Basic Research (grants 14-04-92002 NNS_a, 15-29-02447 ofi_m, 15-29-02601 ofi_m) and the grant of the Council of President of Russian Federation NSH-1801.2014.4. SEM investigations were supported by the Russian Scientific Foundation, grant 14-50-00029. For BKKC, this work was supported by Taiwan-Russian collaboration funding (MOST-100- 2923-B-001-004-MY3, MOST-103-2923-B-001-003-MY3) granted by the Ministry of Science and Technology, Taiwan.

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