Hesione uchidai, Salazar-Vallejo, 2018

Salazar-Vallejo, Sergio I., 2018, Revision of Hesione Savigny in Lamarck, 1818 (Annelida, Errantia, Hesionidae), Zoosystema 40 (12), pp. 227-325 : 313-316

Hesione uchidai n. sp.

( Figs 55 , 56 )

urn:lsid:zoobank.org:act:C805FD51-1E9F-499C-ACA6-A7704D6D77FC

Hesione cf. ehlersi – Uchida 2010: 4-5, figs 1, 2 (partim).

TYPE MATERIAL. — Western Pacific. Philippines. Holotype, UF 4384 , Batangas Province, Verde Island Channel, Mabini, W side Bonito Island , Sta. VIP15-GP-0911 (13.6297, 120.9478; 13°37’46.9200”N, 120°56’52.0800”E), 1 m depth, 18.IV.2015, G. Paulay coll.

ADDITIONAL MATERIAL. — Japan. 13 specimens, MCZ 84730, Ryukyu Islands, Seragaki Tombs , 1.3 km ENE Maeki-zaki, Okinawa (26°30.4’N, 127°52.6’E), 6 m depth, silty-sand and coral rubble,

26.V.1995, R. F. Bolland coll. [8-14 mm long, 1-2 mm wide; most cirri lost; antennae minute; acicular lobe single, tapered; neurochaetal blades very long with tiny denticles, or long with better defined teeth]. — 1 specimen, MCZ 84732, Ryukyu Islands, Seragaki Beach , 1.3 km ENE Maeki-zaki, Okinawa (26°30.4’N, 127°52.6’E), 3 m depth, mixed sand and coral rubble, 21.III.1990, R. F. Bolland coll. [34 mm long, 3 mm wide; bent laterally; most dorsal cirri lost; pharynx fully exposed, divided into three rings, medial one longer, dorsal papilla slightly as long as wide; antennae tapered, directed anterolaterally, shorter than interocular distance; anterior prostomial margin with a shallow depression, longitudinal furrow shallow, becoming deeper towards postectal margin; eyes dark brown, anterior ones twice as large as posterior ones; dorsal cirri basally smooth; acicular lobe single, tapered; neurochaetal blades very long and long, with guard passing subdistal tooth; pygidium smooth, slightly darker than surrounding integument; anus with anal cirri invaginated] .

Philippines. 1 specimen, UF 4354 , Oriental Mindoro Province, Mindoro, Puerto Galera, Batangas Channel , “School Beach” (13.51688, 120.95983; 13°31’00.7680”N, 120°57’35.3880”E), VIP15 -GP-0017, 7-14 m depth, 8.IV.2015, G. Paulay coll. [body pale, with a dissection towards posterior region; eyes dark brown, anterior ones slightly larger than posterior ones; antennae minute, pale, difficult to see; pharynx exposed, dorsal papilla not seen; acicular lobe single, tapered; neurochaetae with pale handles, blades of about the same length in median chaetigers, decreasing in size ventrally in posterior chaetigers, with subapical tooth smaller, guard overpassing subapical tooth; however, in chaetiger 2 most very long with tips simplified, sometimes with teeth minute, or probably eroded].

Australia. 1 specimen, UF 1761 , Western Australia, Ningaloo Reef , ARMS site (-22.76912, 113.70458; 22°46’08.8320”S, 113°42’16.4880”E), 12 m depth, 1 Jun. 2010, team, coll. [28 mm long, 3 mm wide; antennae digitate, shorter than interocular distance; eyes dark brown, anterior ones slightly larger than posterior ones; acicular lobe single, tapered; neurochaetal blades include longer ones with smaller teeth and shorter ones with larger teeth] .

ETYMOLOGY. — This species is named after Dr Hiro’omi Uchida, in recognition of his publications on hesionid polychaetes, and because he illustrated the pigmentation pattern shown by living specimens of this species.

DISTRIBUTION. — From Japan to the Philippines to Western Australia, in mixed bottoms in areas up to 12 m water depth.

DIAGNOSIS. — Hesione with prostomium laterally curved; parapodia with dorsal cirri basally cylindrical, dorsal cirrophore twice as long as wide; aciculae blackish; acicular lobe single, digitate, basally swollen, lower tine missing; neurochaetal blades bidentate, 3-6 times as long as wide; teeth subequal; guards approaching subdistal tooth.

DESCRIPTION

Holotype (UF 4384) pale, without posterior region, with a series of longitudinal pale brown lines ( Fig. 55A ), middorsal one slightl wider, and some darker areas between lateral cushions in ethanol. Body 24 mm long, 4 mm wide, 14 chaetigers.

Prostomium subrectangular, as wide as long, anterior margin truncate, lateral margins slightly rounded, wider towards posterior margin, posterior margin covered by tentacular segment, posterior furrow deep, reaching close to posterior eyes level, ¼ as long as prostomial length; longitudinal depression barely defined. Antennae minute, blunt, almost transparent, twice as long as wide ( Fig. 55B ). Eyes dark brown, anterior ones slightly larger and more separated than posterior ones.

Tentacular cirri without tips, articulated throughout its length, longest one reaching chaetiger 5. Lateral cushions projected, most with surface smooth.

Anterior parapodia contracted, chaetal lobes slightly as long as wide ( Fig. 55C ); posterior parapodial lobes as long as wide ( Fig. 55E ), all truncate; dorsal cirri with cirrophores corrugated, 3 times as long as wide; cirrostyles basally cylindrical, smooth, annulated medially, distally articulated. Ventral cirri articulated, surpassing chaetal lobe.

Neuraciculae two, blackish, larger one thicker, tapered. Acicular lobe single, tapered, blunt ( Fig. 55C, E [insets]), shorter than chaetal lobe distal width.

Neurochaetae about 20 per bundle, blades at a certain angle from handle, bidentate, slightly decreasing in size ventrally, 3-4 times as long as wide ( Fig. 55D, F [insets]).

Posterior region lost; another specimen with posterior region tapered ( Fig. 56G ), pygidum with pale brown spots throughout its surface, anus colorless, projected, anal papillae not visible.

Pharynx partially exposed, distal ring longer than basal, median ring larger than others; anterior margin slightly eroded; dorsal papilla round, as long as wide (seen from above in Fig. 55B ). Oocytes not seen.

Pigmentation

Living specimens brownish ( Fig. 55A ) to pale brown ( Fig. 56A ) with longitudinal, irregular, continuous bands dorsally, and alternating reddish-brown thin bands and wider whitish areas middorsally; pigmentation pattern extended into lateral cushions with darker or paler pigmentations aligned transversally, dorsal deep yellow to whitish, probably fading out quickly in stressed specimens. Tentacular, dorsal cirri and neuropodial lobes pale. Prostomium with two lateral brownish bands, fused posteriorly; nuchal organs colorless.

Preserved specimens with dorsal, brownish longitudinal, irregular, thin bands, middorsal areas include a colorless squarish to as wide as long spot in chaetal lobes section, and a darker as long as wide spot immediately ahead of the colorless spots ( Fig. 56 A-D), smaller in chaetiger 1, progressively longer towards posterior end. The area having the middorsal darker spot, is slightly darker along a transverse band half as wide as each segment, better defined along anterior segments. In other specimens (UF 1170), having pigmentation less intense, these pigmentation bands are retained, especially along the anterior tip of lateral cushions. Pigmentation present in prostomium as small round spots ahead of eyes, or diffuse along the basal pharyngeal ring ( Fig. 56B ); anterior and posterior eyes dark brown, of similar size. Brownish pigmentation extended into lateral cushions leaving a paler area at the same level as the middorsal paler spot ( Fig. 56C ), giving the impression of two bands per segment.

REMARKS

In specimens from the Philippines, UF 4354 (22-24 mm long), medial chaetigers have upper bundle chaetae with longer blades, their teeth are smaller, point more distally, and guards are barely seen, whereas most other chaetae from the same bundle have shorter blades, their teeth are laterally directed, and guards approach distal tooth. This pattern is modified in anterior chaetigers because chaetae with longer blades and smaller, distally pointing teeth are more abundant. Smaller specimens from Japan, MCZ 84730 (8-14 mm long), have more chaetae with longer blades, and smaller teeth pointing distally, and in some chaetae teeth are not developed at all.

Uchida (2010: 4) provided two photos for what he regarded as H. cf. ehlersi . One is a dorsal view of the whole specimen; the other shows a few median body segments. In both, the discontinuous narrow darker, middorsal band is shown along with other paler longitudinal bands. Further, he also keyed out this species, as indicated elsewhere ( Jimi et al. 2017: 38), by emphasising the pigmentation pattern. Uchida (2010) regarded his material as resembling H. ehlersi Gravier, 1900 , but this latter species is colorless. Uchida might have confused the illustration for what Gravier recorded as H. pantherina Risso, 1828 (his figure 16 in plate 10). The illustration is a dorsal view of four midbody segments with longitudinal, discontinuous lines; this record, however, has been indicated above as belonging to H. ceylonica Grube, 1874 .

Hesione uchidai n. sp. resembles H. ceylonica Grube, 1874 , reinstated, because they have neurochaetal blades up to 6 times as long as wide. As indicated in the key below, they differ in the shape of the acicular lobes and size of neurochaetal blades. In H. uchidai n. sp. lobes are digitate, and blades are 4-6 times as long as wide, whereas in H. ceylonica the lobes are triangular or basally swollen, and blades are 5-6 times as long as wide. The pigmentation pattern of living specimens clearly separates these two species because in H. uchidai n. sp. the longitudinal bands are continuous, and there are discontinuous reddish brown bands, alternating with pale areas middorsally, whereas in H. ceylonica the longitudinal bands are discontinuous, interrupted by dorsal transverse pale, wide bands.

Figures

FIG. 55. — Hesione uchidai n. sp., holotype, UF 4384: A, alive, dorsal view; B, anterior body half, dorsal view, pharynx exposed; C, prostomium and basal pharynx ring, prostomium slightly oblique, bent dorsally (arrows point to antennae, asterisk indicates dorsal papilla); D, chaetiger 7, left parapodium, anterior view (inset: acicular lobe); E, same, neurochaetae (insets: blades); F, chaetiger 12, left parapodium, anterior view; G, same, neurochaetae (insets: blades). Scale bars: A, 2.2 mm, B, 2 mm; C, D, 0.3 mm; E, 150 µm; F, 0.5 mm; G, 230 µm.

FIG. 56. — Hesione uchidai n. sp., non-type specimen, UF 1761: A, complete, dorsal view; B, anterior region, dorsal view, depressed by a glass slide fragment; C, anterior end, dorsal view; D, chaetigers 4–6, dorsal view; E, chaetiger 3, right parapodium, anterior view (insets: neurochaetal blades); F, chaetiger 7, right parapodium, anterior view (insets: neurochaetal blades); G, posterior end, oblique dorsal view. Scale bars: A, 1.5 mm; B, C, 0.6 mm; D, 0.7 mm; E, 130 µm; F, 0.8 mm; G, 1.1 mm (photo A, G. Paulay).