Hesione reticulata von Marenzeller, 1879

Jimi, Naoto, Salazar-Vallejo, Sergio I. & Kajihara, Hiroshi, 2017, Designation of a neotype and redescription of Hesionereticulata von Marenzeller, 1879 from Japan (Annelida, Hesionidae), ZooKeys 657, pp. 29-41 : 31-36

Hesione reticulata von Marenzeller, 1879 Figs 1, 2, 3

Hesione reticulata von Marenzeller, 1879: 129-131, pl. 3, fig. 4; Izuka 1912: 192-194, pl. 2, fig. 7; Imajima and Hartman 1964: 80; Uchida 2009: 36-37, fig. 1.

Hesione splendida Hessle 1925: 13-15 (non Savigny in Lamarck, 1818; partim, smallest specimen with transverse white bands belongs elsewhere).

Hesione pantherina Fauvel 1937: 59-60 (non Risso, 1826).

Hesione intertexta Wu et al. 1975: 75, pl. 2, figs 7-8 (non Grube, 1878).

Type material.

Northwestern Pacific, Japan. Neotype NSMT Pol N-620, and three paraneotypes NSMT Pol 113205, NSMT Pol 113206, NSMT Pol 113207, Zaimokuza (35°18'02.9"N, 139°33'02.9"E), rocky bottom, 1 m depth, 19 Mar. 2016, N. Jimi & Hesione Tanaka, coll. Paraneotypes (NSMT Pol 113205 - NSMT Pol 113207) 40-47 mm long, 4 mm wide).

Neotype locality.

Zaimokuza (35°18'02.9"N, 139°33'02.9"E), rocky bottom, 1 m depth.

Description.

Neotype (NSMT Pol N-620) complete. Body cylindrical, medially swollen (Fig. 1A), damaged, 43 mm long, 4 mm wide in chaetigers 8-9 (not including parapodia), 16 chaetigers (chaetae and parapodia of 2nd left, 8th right, and 9th right chaetigers removed for observation; dorsal cirri of 3rd and 7th chaetigers removed for DNA extraction).

Dorsal pigmentation pattern consisting of longitudinal, brownish, subcontinuous, irregular lines; no reddish brown longitudinal broken line on median line; single, irregularly-shaped spot (formed by absence of brown pigment, through which basement pale tan to wheat body color seen) on each chaetiger except 2nd, arranged mid-dorsally (larger anteriorly; reduced medially and posteriorly); and additional row of similar but smaller spots on lateral cushion on each side; silvery white spots absent. Cirrophores yellow; cirrostyles yellow to whitish; parapodial lobes whitish (Fig. 1 B–E). After six months in ethanol, pigmentation limited to dorsal, pale brown, discontinuous longitudinal bands (Fig. 2A).

Integument smooth, annulated, giving impression of being tuberculated, especially along posterior region; longitudinal ridges absent in lateral cushions.

Prostomium heart-shaped, wider than long (Fig. 1B, E); anterior margin truncated; lateral margins rounded in anterior body, but expanded posteriorly; posterior margin cleft, as long as 1/6 prostomial length; longitudinal furrow shallow; dark transverse line present on prostomial anterior margin. Antennae digitate, twice longer than wide. Eyes blackish, on center of prostomium; anterior and posterior eyes in trapezoidal arrangement; anterior eyes slightly more separated than posterior eyes; anterior eyes ovoid (appearing longer than wide), posterior eyes rounded.

Tentacular cirri tapered, longest complete anterior cirri reaching chaetiger 5. Lateral cushions slightly projected, entire, with smooth surface.

Parapodia with dorsal cirrophore twice longer than wide, articulated (Fig. 3A, E). Cirrostyle basally cylindrical, medially and distally articulated, as long as body width, including parapodia (Fig. 3A, F). Neuropodia with parallel sides, cylindrical (Fig. 3A). Acicular lobe double; upper tine twice larger than lower one, digitate (Fig. 3B); lower tine of 8th chaetiger of NSMT Pol N-620 and 9th chaetiger of NSMT Pol 113205 adhered or fused to upper tine and difficult to observe (Fig. 3C), it can be clearly confirmed on other four parapodia examined. One acicula present, blackish. Neurochaetae 19-28 per bundle, blade size decreasing ventrally (Fig. 3C); neurochaetal blades bidentate, 3-4 times longer than wide, subdistal tooth shorter and wider than distal one; guard reaching apical tooth (Fig. 3D). Ventral cirrophore three times wider than long; cirrostyle articulated, surpassing chaetal lobe tip.

Prepygidial segment with two cirri, three times as long as body width of previous chaetiger (chaetiger 16). Pygidium smooth, trapezoidal, as long as wide, cylindrical (Fig. 1D); anus with two anal cirri; anal cirri tapered.

Venter without pigmentation, with longitudinal midventral depression.

Pharynx divided into three rings, with relative lengths 1.5:1.5:1; basal ring with similar pigmentation as anterior end (Fig. 1E); dorsal papilla pale, longer than wide (length: width 1.5:1).

Oocytes not visible.

Inner anatomy

(observed in paraneotypes NSMT Pol 113205-113207). Pharynx and esophagus thick, muscular, yellowish, continuing into darker, shorter stomach; enteric caeca extending anteriorly along two or three chaetigers (Fig. 2B). Stomach contents included gastropod (Fig. 2C) and amphipod remains as prey items.

Remarks.

The nomenclatural status of Hesione reticulata von Marenzeller, 1879 has been unclear due to several reasons: there is no type material, some diagnostic features were not clarified in the original description, the species has been recorded from the Red Sea, and some authors have regarded it as a junior synonym of other species within the genus. Consequently, in order to comply with the International Code of Zoological Nomenclature ( ICZN 1999, Art. 75.3) we are herein proposing a neotype.

The above description and illustrations will clarify the taxonomic status of Hesione reticulata (Art.75.3.1), and its diagnostic and differential features have been included in the description and illustrations (Arts 75.3.2, 75.3.2), and will be contrasted below. Our enquiries on the existence of type material of Hesione reticulata to Dr. Helmut Sattmann, Curator of Marine Invertebrates, in the Naturhistorisches Museum, Vienna, where Emil von Marenzeller used to work and produced all of his publications, indicate that type material is absent (Art. 75.3.4), probably destroyed or never deposited. The original collector was Carl Koerbl ( von Marenzeller 1879: 131) and some of his specimens were donated to the Vienna Museum by Richard von Drasche-Wartinberg ( Sato and Sattmann 2009), but there is no type material available there.

The neotype fits the original description and because it was recently collected, it even matches the general pigmentation pattern which is not long-lasting in ethanol. Further, as happens in some other species of Hesione , they are simultaneous hermaphrodites ( Bergmann 1902, 1903), so that differences in pigmentation pattern among different specimens cannot be attributed to sex (Art. 75.3.5). Thus, the morphology of our material does not contradict von Marenzeller’s (1879) original description of Hesione reticulata , nor the general features subsequently described by Izuka (1912: 192), Imajima and Hartman (1964: 80), and Uchida (2009: 36-37).

The original specimen was collected in the east coast of Enoshima (35°18'07"N, 139°29'00"E), and the neotype was found in Zaimokuza (35°18'02.9"N, 139°33'02.9"E), nearly four kilometers away, such that we are confident these two localities belong to the same ecological unit (Art. 75.3.6). The neotype of Hesione reticulata has been deposited in the National Science Museum, Tokyo, which holds the most important polychaete collection in Japan, and has a very important tradition in the scientific study of polychaetes from Japan and elsewhere (Art. 75.3.7).

Another taxonomic relevance of our study lies in the identification of the dorsal color pattern in the living state as a clear distinguishing feature between Hesione reticulata , Hesione intertexta , and Hesione cf. ehlersi sensu Uchida (2009). The color pattern agrees with von Marenzeller’s (1879) description of the holotype which had, over a reddish-brown background, irregular spots fused into wide bands along some anterior segments continuing to the end of the body. von Marenzeller (1879) mostly relied on this complex reticulated pigmentation pattern for justifying the establishment of Hesione reticulata .

Ngamniyom et al. (2014) and Lee and Ong (2015) characterized the two western Pacific species, Hesione cf. picta and Hesione intertexta . The former has wide dorsal transverse bands, by which Hesione cf. picta can be separated from Hesione intertexta and Hesione reticulata , because the latter two have dorsal, longitudinal, discontinuous dark bands with paler spots mid-dorsally and along dorsal surface of lateral cushions. Furthermore, Hesione intertexta and Hesione reticulata also have tiny antennae and neurochaetal blades with guards approaching distal tooth. Based on these shared characteristics, Wu et al. (1975) viewed Hesione reticulata as a junior synonym of Hesione intertexta . Our observation, however, clearly shows that they differ in pigmentation pattern: in Hesione reticulata the paler spots are smaller, and the mid-dorsal ones tend to be round, whereas in Hesione intertexta they are longer than wide and markedly larger.

Uchida (2009) described Hesione cf. ehlersi , a species with similar morphological features to Hesione reticulata . Indeed, von Marenzeller’s original description of Hesione reticulata could apply to both species. As Uchida (2009) stated, dorsal pigmentation in life is useful for discrimination of the two species; Hesione cf. ehlersi has a reddish brown longitudinal broken line on the median line, whereas Hesione reticulata lacks this line. Further study is needed to resolve the taxonomic position of Hesione cf. ehlersi .

The vivid images of the dorsal color pattern in Hesione reticulata , along with the COI barcoding sequence provided in this paper, will contribute to future taxonomic revision of the genus Hesione .

Hesione reticulata was regarded as a distinct species by Hartman (1959: 185) and it can be distinguished from its former synonyms Hesione intertexta , Hesione splendida as indicated by Augener (1913) and Hessle (1925), or from Hesione pantherina as suggested by Fauvel (1937) as follows: from Hesione splendida , Hesione reticulata can be separated by the dorsal pigmentation; it is brownish in Hesione reticulata , but pearly gray in Hesione splendida (Savigny, 1822), whereas from Hesione pantherina , Hesione reticulata can be distinguished because the guard tooth in Hesione reticulata reaches the apical tooth, whereas those in Hesione pantherina do not ( Monro 1926).

One of the important discoveries in our observation of the specimens of Hesione reticulata is that the acicular lobe in this species is doubled, comprised of the upper and lower tines, a character state that separates Hesione species in two groups, each with approximately the same number of species (SISV pers. obs.). von Marenzeller (1879, fig. 4) illustrated a parapodium excised from the middle part of the body in the holotype specimen, indicating that there was a single, thick, finger-shaped acicular lobe, unlike the doubled lobe that we observed in this study. Izuka (1912) and Imajima and Hartman (1964) also described the acicular lobe as a single lobe. In two of the six parapodia examined (left one on the 2nd, right one on the 8th, and right one on the 9th chaetigers from NSMT Pol N-620; right one on the 9th chaetiger from NSMT Pol 113205; and left ones on the 3rd and 9th chaetigers from NSMT Pol 113207), the lower tine adhered to the upper tine. It appeared as if it were a single parapodial lobe, but a careful observation showed that it actually represents a doubled lobe. The reason the acicular lobe was described as ‘single’ in the previous studies may be that the lower tine in their material was deformed in preservation to lie below the upper tine, or to contact closely to the upper tine. The original illustration ( von Marenzeller 1879, fig. 4) clearly indicates that the acicular lobe was placed under the chaetal bundles on the glass slide. This must have made the acicular lobe difficult to be observed, which would also explain why the adjacent upper and lower tines were hardly detected. This feature further adds to the distinction between Hesione reticulata and Hesione intertexta : the acicular lobe in Hesione reticulata is double whereas it is single in Hesione intertexta .

The record of Hesione reticulata by Imajima (1997: 171) might not belong to the same species because he indicated that the acicular lobe was single ("a superior conical papilla"), and because unlike our specimens, his material was collected from 230-250 m depth in Suruga Bay. Other specimens recorded as Hesione reticulata by Imajima (2003: 132-134), collected in shallow water, were characterized as having acicular lobe single ("a superior conical papilla"), and are regarded as belonging to another species.

Distribution. Hesione reticulata has so far been recorded only from Japan: Kanagawa ( von Marenzeller 1879; Izuka 1912; this study), Shizuoka and Wakayama ( Izuka 1912), and the middle of Honshu to Kyushu ( Uchida 2009).

Key to species of Hesione from Japan

(modified from Uchida 2009)