Harmothoe acuminata Willey, 1902

Barnich, R., Fiege, D., Micaletto, G. & Gambi, M. C., 2006, Redescription of Harmothoe spinosa Kinberg, 1856 (Polychaeta: Polynoidae) and related species from Subantarctic and Antarctic waters, with the erection of a new genus, Journal of Natural History 40 (1 - 2), pp. 33-75 : 59-67

Harmothoe acuminata Willey, 1902

( Figure 9A–J ; Table III) Harmothoe crosetensis acuminata Willey 1902, p 266 , Plate 43 Figures 3 , 9–11 . Harmothoe crosetensis: Bergström 1916, p 284 , Plate 2 Figure 4 ; Monro 1939, p 96 (part);

Knox and Cameron 1988, p 31, Figures 60, 61. [not H. crosetensis ( McIntosh, 1885) ] Harmothoe crosetensis type B: Uschakov 1962, p 159. [not H. crosetensis ( McIntosh, 1885) ] Harmothoe crosetensis type A: Averincev 1972, p 119, Table 1. [not H. crosetensis ( McIntosh,

1885)]

Type material

Harmothoe crosetensis acuminata: BMNH 1902.1.8.93–4, lectotype (cs in two fragments; designated, described, and figured herein) and BMNH 2005.2455, paralectotype (cs, strongly bent), ‘‘ Southern Cross’ ’ Expedition, Cape Adare , 9 January 1900, 26 fathoms.

Lagisca crosetensis: BMNH 1885.12.1.68, lectotype (cs in two fragments) and BMNH 2005.2454, paralectotype (af), ‘‘ Challenger’ ’ Expedition, St. 147, 46 ° 169S, 48 ° 279E, near the Crozet Islands, 30 December 1873, 1600 fathoms, diatom ooze (see description of Harmothoe crosetensis above).

Additional material. One spm. (cs), ANT XIII/3, 39/018, AGT; one spm. (cs in two fragments), ANT XIII/3, 39/025, AGT; one spm., SMF 15164 (af), ANT XIII/3, 39/025, AGT; one spm. (af with separate elytra), ANT XIII/3, 39/025, AGT.

Diagnosis

Elytral margin with digitiform papillae; near anterior elytral margin surface with conical, pointed, or blunt microtubercles, central and posterior part of elytron with numerous, pointed, thorn- to spine-shaped macrotubercles getting larger towards posterior margin.

Description (based on lectotype of Harmothoe crosetensis acuminata )

Body with 34 segments. At anterior end ( Figure 9A ), prostomium bilobed, with cephalic peaks; ceratophore of median antenna in anterior notch, style of median antenna missing; lateral antennae inserted ventrally with papillate, tapering styles; anterior pair of eyes situated dorsolaterally on widest part of prostomium, posterior pair dorsally near hind margin of prostomium; palps papillate, tapering.

Tentaculophores inserted laterally to prostomium, each with a single notochaeta and a dorsal and ventral tentacular cirrus with styles of cirri regenerating or broken (style of right dorsal tentacular cirrus missing). Second segment with first pair of elytra, biramous parapodia, and long buccal cirri.

Fifteen pairs of elytra, covering dorsum, on segments 2, 4, 5, 7, then on every second segment to 23, 26, 29, 32; last two segments cirrigerous; outer lateral margin, posterior margin, and posterior half of elytra with digitiform papillae; near anterior elytral margin surface with conical, pointed, or blunt microtubercles, central and posterior part of elytron with numerous, pointed, thorn- to spine-shaped macrotubercles getting larger towards posterior margin ( Figure 9B–D ). Cirrigerous segments with distinct dorsal tubercles; dorsal cirri with cylindrical cirrophore and style papillate, abruptly tapering subdistally. Ventral cirri with smooth, tapering style.

Parapodia biramous; notopodia with elongate acicular lobe; neuropodia with elongate prechaetal acicular lobe with digitiform supra-acicular process; neuropodial postchaetal lobe shorter than prechaetal lobe, rounded; tips of noto- and neuroacicula penetrating epidermis ( Figure 9E ). Notochaetae stouter than neurochaetae; notochaetae with distinct rows of spines and long bare, blunt to pointed tip ( Figure 9F ); neurochaetae falcate, with rows of spines distally; upper and lower neurochaetae unidentate, tip of middle neurochaetae bidentate with minute secondary tooth (often abraded) ( Figure 9G–J ).

Nephridial papillae distinct from segment 6.

Measurements

Lectotype of Harmothoe crosetensis acuminata (BMNH 1902.1.8.93-4), cs in two fragments, some middle segments cut off ( Figure 9 ): L 21 mm, W 6.5 mm for 34 segments; paralectotype (BMNH 2005.2455), cs, strongly bent: L 30 mm, W 10 mm for 37 segments; additional specimen (SMF 15164), af: L 18 mm, W 6 mm for 22 segments.

Remarks

Since the differences between H. crosetensis and H. acuminata have been extensively discussed above, we focus here only on the characters separating H. acuminata from H. serrata Day, 1963 (see also above). Both species share papillate elytral margins and surface and pointed, thorn- or spine-shaped elytral macrotubercles. But in H. serrata thorn-shaped macrotubercles are only present near the posterior elytral margin, while in H. acuminata macrotubercles are thorn- to spine-shaped, covering the central and posterior part of the elytron and becoming larger towards the posterior margin.

Among the Antarctic species described herein, the two species belonging to the new genus Antarctinoe (see below), i.e. A. ferox ( Baird, 1865) and A. spicoides ( Hartmann-Schröder, 1986) , are also characterized by thorn-shaped, pointed macrotubercles. However, in these two species the characteristic papillae occurring at the elytral margin and the surface of both H. acuminata and H. serrata are missing. Furthermore, species belonging to Antarctinoe gen. nov. differ from Harmothoe in the characteristic length and orientation of the notochaetae (for more details, see below) and the exclusive presence of unidentate neurochaetae.

Distribution

Antarctic region : South Georgia and Graham region ( Bergström 1916), Weddell Sea , and Cape Adare, Ross Sea (type locality) .

Antarctinoe gen. nov.

Type species. Harmothoe (Eunoe) spica spicoides Hartmann-Schröder, 1986 .

Diagnosis

Body dorsoventrally flattened, short, with fewer than 50 segments; dorsum covered only partly by elytra, except first two to three pairs. Fifteen pairs of elytra on segments 2, 4, 5, 7, on alternate segments to 23, 26, 29, and 32. Dorsal cirri with cylindrical cirrophore and long style on segments lacking elytra; pair of nodular dorsal tubercles on cirrigerous segments. Ventral cirri short (except on second segment), consisting of cirrophore and style on all segments.

Prostomium bilobed, with distinct cephalic peaks and three antennae; ceratophore of median antenna in anterior notch, lateral antennae with ceratophores inserted ventrally to median antenna; a pair of palps present; two pairs of eyes, anterior pair situated dorsolaterally on widest part of prostomium, posterior pair dorsally near hind margin of prostomium; pharnyx with nine pairs of border papillae and two pairs of hooked jaws. Facial tubercle present.

First or tentacular segment with a pair of tentaculophores inserted laterally to prostomium, each bearing a dorsal and a ventral tentacular cirrus and a single notochaeta. Second or buccal segment with first pair of elytra, biramous parapodia, long ventral cirri, and a nuchal lobe.

Parapodia biramous, both rami with elongate acicular lobe; noto- and neuropodia of about same size; neuropodia with digitiform supra-acicular process; tips of noto- and neuroacicula penetrating epidermis. Bases of neuropodia ventrally without tubercles between ventral cirrus and body wall. Notochaetae of several kinds (depending on the species); all known species with very long, stout notochaetae, some projecting laterally, the majority projecting dorsally to meet mid-dorsally; longest stout notochaetae distinctly longer than longest neurochaetae (up to about twice the length).

Neurochaetae falcate with unidentate tip.

Nephridial papillae distinct from segment 6 to the end of the body. Pygidium with one pair of anal cirri.

Remarks

In our material from the Weddell Sea, we found specimens belonging to two species having very long, stout notochaetae projecting dorsally to meet mid-dorsally, unidentate neurochaetae, and the same ornamentation of the elytra, but differing in the number of notochaetal types and the shape of the notochaetal tips. In the literature specimens showing only short and very long stout notochaetae with more or less blunt tips, were referred to Hermadion or Harmothoe ferox , to Eunoe spica , or to Harmothoe crosetensis among others. Specimens with up to four kinds of notochaetae (i.e. short notochaetae with pointed tip; very long stout notochaetae with pin-like tip; fine, slender notochaetae with pointed to pinlike tip; and capillary notochaetae with pointed tip; with the presence of the latter two types occurring only in large specimens) were described as Harmothoe (Eunoe) spica spicoides or H. crosetensis (for extensive synonymy see below).

We establish herein the new genus Antarctinoe gen. nov. for the two species A. ferox ( Baird, 1865) and A. spicoides ( Hartmann-Schröder, 1986) , described below, and characterized mainly by the presence of 15 pairs of elytra, fewer than 50 segments, prostomium with cephalic peaks, neuropodia with a supra-acicular process, very long stout notochaetae mostly orientated dorsally to meet mid-dorsally, and unidentate neurochaetae.

Antarctinoe gen. nov. is easily separated from Harmothoe Kinberg, 1856 due to the exclusive presence of unidentate neurochaetae, never being distinctly bidentate as in Harmothoe . Furthermore, the very long stout notochaetae orientated to protect the dorsum are a unique character of Antarctinoe enabling the further distinction between this genus and Harmothoe , and also from Eunoe Malmgren, 1865 . To our knowledge, in the latter two genera the longest stout notochaetae are never distinctly longer than the longest neurochaetae (usually shorter or of about same length) and mostly orientated laterally (see Barnich and Fiege 2000, 2003, 2004).

The differentiation between Antarctinoe and Hermadion Kinberg, 1856 is rather easily demonstrated. Our investigations of a syntype of Hermadion magalhaensi Kinberg, 1856 (SMNH-532), i.e. the type species of the genus, showed that Hermadion is characterized by rounded anterior prostomial edges without cephalic peaks and acicular neuropodial lobes without supra-acicular process, while Antarctinoe shows a prostomium with cephalic peaks and neuropodia with a distinct supra-acicular process distally at the acicular lobe. Furthermore, the characteristic size and orientation of the notochaetae as described above for Antarctinoe are not found in Hermadion .

Etymology

The name refers to the geographical area (Antarcti -) and to the closely related genus Eunoe (-noe); gender feminine.

Antarctinoe spicoides ( Hartmann-Schröder, 1986) comb. nov.

( Figures 10A–G , 11A–E ) Harmothoe (Eunoe) spica spicoides Hartmann-Schröder 1986, p 73 , Figures 1–4 ; Hartmann-

Schröder and Rosenfeldt 1990, p 92. [new synonymy] Eunoe spica spicoides: Stiller 1996, p 33 , Plate 14. Hermadion rouchi: Benham 1921, p 46 , Figures 43–47. [not Hermadion rouchi Gravier, 1911 ].

Harmothoe crosetensis: Ehlers 1913, p 442 , Plate 27 Figures 1–4 ; Monro 1939, p 96 (part). [not Harmothoe crosetensis ( McIntosh, 1885) ]

Harmothoe crozetensis [sic]: Augener 1932b, p 17, Figure 1 . [not H. crosetensis ( McIntosh, 1885) ]

Harmothoe crosetensis type C: Uschakov 1962, p 159, Plate 3 Figures A–G. [not H. crosetensis ( McIntosh, 1885) ]

Harmothoe crosetensis type B and C: Averincev 1972, p 119, Table 1. [not H. crosetensis ( McIntosh, 1885) ]

Harmothoe crosetensis: Hartman 1964, p 28 , Plate 7 Figure 5 (part). [not H. crosetensis ( McIntosh, 1885) ]

Type material

Harmothoe (Eunoe) spica spicoides: ZMH P-18608, holotype, South Shetland Islands Expedition, ‘‘ Meteor’ ’ 56, St. 195, 61 ° 26.79S, 52 ° 06.39W, 18 January 1981, 650 m,

Additional material. Ten spms (9 cs, 1 af), ANT XIII/3, 39/006, AGT; one spm., SMF 15165 (cs), ANT XIII/3, 39/006, AGT; three spms (2 cs, 1af), ANT XIII/3, 39/009, AGT; one spm. (af), ANT XIII/3, 39/012, GSN; one spm. (cs), ANT XIII/3, 39/013, GSN; three spms (cs), ANT XIII/3 1996, 39/015, GSN; two spms (cs), ANT XIII/3, 39/017, GSN; 19 spms (9 cs, 10 af), ANT XIII/3, 39/029, GKG; 17 spms (13 cs, 4 af), ANT XV/3, 48/049; one spm. (cs), ANT XV/3, 48/277.

Diagnosis

Elytral margin smooth; elytral surface with conical microtubercles with blunt to pointed tip; thorn-shaped macrotubercles scattered in posterior half of elytron. Long, stout notochaetae projecting dorsally to meet mid-dorsally with rows of spines distally and pin-like tip; large specimens with additional fine, slender notochaetae with pointed to pin-like tip, and capillary notochaetae with pointed tip. Neurochaetae falcate, unidentate.

Description

The description is based on the holotype of Harmothoe (Eunoe) spica spicoides , but notochaetal characters are complemented by an additional specimen from the Weddell Sea (SMF 15165); see ‘‘Remarks’’ section below.

Body with 42 segments. At anterior end ( Figure 10A ), prostomium bilobed, with cephalic peaks; ceratophore of median antenna in anterior notch, style missing; lateral antennae inserted ventrally, styles missing; anterior pair of eyes situated dorsolaterally on widest part of prostomium, posterior pair dorsally near hind margin of prostomium; palps missing.

Tentaculophores inserted laterally to prostomium, each with a single notochaeta and a dorsal and ventral tentacular cirrus with styles papillate, slightly inflated subdistally, then abruptly tapering (styles missing, except for left dorsal tentacular one). Second segment with first pair of elytra, biramous parapodia, and long buccal cirri.

Fifteen pairs of elytra, covering dorsum, on segments 2, 4, 5, 7, then on every second segment to 23, 26, 29, 32; last 10 segments cirrigerous; elytral margin smooth; elytral surface with conical microtubercles with blunt to pointed tip; thorn-shaped macrotubercles scattered in posterior half of elytron, mainly near outer lateral and posterior margin ( Figure 10B, C ). Cirrigerous segments with distinct, dorsal tubercles; dorsal cirri with cylindrical cirrophore and style smooth to slightly papillate, slightly inflated subdistally, then abruptly tapering. Ventral cirri with slightly papillate, tapering style.

Parapodia biramous; notopodia of about same size as neuropodia with elongate acicular lobe; neuropodia with elongate prechaetal acicular lobe with digitiform supra-acicular process; neuropodial postchaetal lobe shorter than prechaetal lobe, rounded; tips of noto- and neuroacicula penetrating epidermis ( Figures 10D , 11A ).

Notochaetae of several kinds depending on the size of the specimen; small to mediumsized specimens with short, stout notochaetae with rows of spines and more or less pointed tip and long, stout notochaetae projecting dorsally to meet mid-dorsally with rows of spines distally and pin-like tip ( Figures 10E, F , 11B, C ); large specimens additionally with fine, slender notochaetae with rows of spines distally and pointed to pin-like tip, and capillary notochaetae with rows of spines distally and pointed tip ( Figure 11A–E ). Neurochaetae falcate with unidentate tip ( Figure 10G ).

Nephridial papillae distinct from segment 6.

Measurements

Holotype of Harmothoe (Eunoe) spica spicoides (ZMH P-18608), cs, figured herein ( Figure 10 ): L 33 mm, W 8 mm for 42 segments (medium-sized); additional large specimen figured (SMF 15165), cs ( Figure 11 ): L 49 mm, W 10 mm for 43 segments. Smallest specimen found: L 15 mm, W 4 mm for 30 segments (last few segments missing); largest specimen found: L 50 mm, W 14 mm for 40 segments.

Remarks

Ehlers (1913) described as Harmothoe crosetensis specimens with the characteristic notochaetae and unidentate neurochaetae of Antarctinoe spicoides . He supposed that the orientation and length of the notochaetae and the occurrence of additional slender or capillary notochaetae could be features of an epitokous stage. But since we found these characters also in small, immature specimens, they cannot be epitokous; neither are they sex-related, since we found both males and females with these characters. Ehlers (1913) also noted the resemblance of his specimens with Hermadion ferox ( Baird, 1865) , referred herein to Antarctinoe ferox . But, according to him specimens of H. ferox have elytra which do not cover the dorsum, which is true for large specimens only, as we could confirm by our observations. As demonstrated below, A. spicoides can be clearly separated from A. ferox by the presence of pin-like tips in the long, stout notochaetae and the occurrence of additional slender and capillary notochaetae in larger specimens.

Influenced by Ehlers, Monro (1939) described an atokous form of Harmothoe crosetensis (referred herein to H. acuminata Willey, 1902 ) and an epitokous form, which we recognize as A. spicoides . The differences observed by Monro are not related to the reproductive stage of the specimens, but in this case two genera and species have been confused: (1) Harmothoe acuminata characterized by at least some bidentate neurochaetae, relatively short notochaetae orientated mostly laterally, and elytra with papillate margin and surface and numerous thorn- to spine-shaped macrotubercles; and (2) Antarctinoe spicoides with unidentate neurochaetae, long, stout notochaetae projecting dorsally to meet mid-dorsally with pin-like tip (large specimens with additional slender and capillary notochaetae), and elytra without papillae at margin and surface and thorn-shaped macrotubercles scattered only in posterior half of elytron.

According to our observations the occurrence of additional slender and capillary notochaetae is size-related. The holotype of Harmothoe (Eunoe) spica spicoides is a mediumsized specimen with a width of 8 mm having no additional notochaetal types. But we found also specimens of about the same size with few capillary and slender notochaetae; all larger specimens showed numerous additional notochaetae.

Among the larger specimens we found males and females as well, thus, the occurrence of different kinds of notochaetae is not due to sexual dimorphism. Sex determination proved to be rather difficult since the specimens were not in a sexually reproductive stage, the dissection of the gonads revealing mostly immature sperm or eggs.

Distribution

Widely distributed in the Antarctic region: South Shetland Islands (type locality), Elephant Island ( Hartmann-Schröder and Rosenfeldt 1990), Weddell Sea (cf. also Stiller 1996), Bouvet and Bridgman Island ( Augener 1932b); King George Land ( Ehlers 1913; Monro 1939), Commonwealth Bay ( Benham 1921).

Figures

Figure 1. Harmothoe spinosa (holotype, SMNH-type-409). (A) Anterior end; palps and styles of antennae and cirri missing, right 2nd and 3rd parapodia cut off; (B) right elytron from anterior body region; (C) left elytron from segment 2; (D) detail of posterior margin of same; (E) right cirrigerous parapodium of segment 16, posterior view, style of dorsal cirrus missing; (F) short notochaeta; (G) long notochaeta; (H) tip of same; (I) middle neurochaeta; (J) tip of same; (K) tip of upper neurochaeta; (L) tip of lower neurochaeta. Scale bars: 1 mm (A–C); 250 mm (D, F, G, I); 500 mm (E); 50 mm (H, J–L).

Figure 2. Harmothoe exanthema (holotype; ZMUC POL 1671). (A) Anterior end; style of right dorsal cirrus of segment 3 missing; (B) right elytron from mid-body region; (C) detail of outer lateral margin of same; (D) macrotubercles from posterior part of elytron; (E) right cirrigerous parapodium of unknown segment, posterior view, style of dorsal cirrus missing; (F) long notochaeta; (G) tip of same; (H) middle neurochaeta; (I) tip of same; (J) tip of upper neurochaeta; (K) tip of lower neurochaeta. Scale bars: 1 mm (A, B); 250 mm (C, D, F, H); 500 mm (E); 50 mm (G, I–K).

Figure 3. Harmothoe fuligineum (SMF 15162). (A) Anterior end; styles of left lateral antenna, left and right dorsal and left ventral tentacular cirri, and right dorsal cirrus of segment 3 missing; (B) right elytron of segment 5; (C) detail of area near outer lateral margin of same; (D) left cirrigerous parapodium of segment 12, posterior view, style of dorsal cirrus missing; (E) long notochaeta; (F) tip of same; (G) middle neurochaeta; (H) tip of same; (I) tip of upper neurochaeta; (J) tip of lower neurochaeta. Scale bars: 2 mm (A, B); 250 mm (C); 500 mm (D); 250 mm (E, G); 100 mm (F, H–J).

Figure 4. Harmothoe fullo (lectotype, ZMB 685). (A) Anterior end; style of right dorsal tentacular cirrus regenerating; (B) left elytron from unknown segment in mid-body region; (C) detail of mound of same; (D) right elytron from unknown segment in mid-body region; (E) right elytragerous parapodium of segment 11, posterior view; (F) long notochaeta; (G) tip of same; (H) middle neurochaeta; (I) tip of same; (J) tip of upper neurochaeta; (K) tip of lower neurochaeta. Scale bars: 2 mm (A, B, D); 250 mm (C); 500 mm (E); 250 mm (F, H); 100 mm (G, I– K).

Figure 5. Harmothoe antarctica (lectotype, BMNH 1885.12.1.59). (A) Anterior end; right palp and style of median antenna missing; (B) left elytron from unknown segment in mid-body region; (C) detail from posterior margin of same; (D) right elytragerous parapodium from unknown segment, anterior view; (E) long notochaeta; (F) tip of same; (G) middle neurochaeta; (H) tip of same; (I) tip of upper neurochaeta; (J) tip of lower neurochaeta. Scale bars: 2 mm (A, B); 250 mm (C, E, G); 1 mm (D); 100 mm (F, H–J).

Figure 9. Harmothoe acuminata (lectotype, BMNH 1902.1.8.93–4). (A) Anterior end; styles of median antenna and right dorsal tentacular cirrus missing, tips of styles of remaining tentacular cirri broken; (B) left elytron of segment 5; (C) detail from area near anterior margin of same; (D) detail of posterior margin of same; (E) right elytragerous parapodium from mid-body region, posterior view; (F) long notochaeta; (G) middle neurochaeta; (H) tip of same; (I) tip of upper neurochaeta; (J) tip of lower neurochaeta. Scale bars: 2 mm (A); 1 mm (B); 250 mm (C, D, F, G); 500 mm (E); 50 mm (H–J).

Figure 10. Antarctinoe spicoides (holotype, ZMH P-18608). (A) Anterior end; palps and styles of antennae and cirri missing, except for left dorsal tentacular one; right tentaculophore and right second parapodium cut off; (B) right elytron from unknown segment; (C) detail of outer lateral margin of same; (D) right cirrigerous parapodium from mid-body region, posterior view; (E) distal half of short, stout notochaeta; (F) tip of long, stout notochaeta; (G) distal part of middle neurochaeta. Scale bars: 2 mm (A); 1 mm (B, D); 250 mm (C, E–G).

Figure 11. Antarctinoe spicoides (SMF 15165). (A) Left cirrigerous parapodium of segment 18, posterior view; (B) tip of long, stout notochaeta; (C) tip of short, stout notochaeta; (D) tip of fine, slender notochaeta; (E) tip of capillary notochaeta. Scale bars: 2 mm (A); 100 mm (B–E).