Anguillosyllis elegantissima, Maciolek, 2020

Maciolek, Nancy J., 2020, Anguillosyllis (Annelida: Syllidae) from multiple deep-water locations in the northern and southern hemispheres, Zootaxa 4793 (1), pp. 1-73 : 53-56

Anguillosyllis elegantissima n. sp.

Figures 25–26

urn:lsid:zoobank.org:act:AC7C7D62-921C-456A-A4D2-C676D3331358

Material examined. (44 specimens from 26 stations) South China Sea, off Brunei. Coll. J.A. Blake, Chief Scientist: Sta. 29, 4 Jun 2011, 5°43′01.15997″N, 114°06′07.18190″E, 1537 m, holotype ( MCZ 147937 ) . Coll. P. Neubert: Sta. DA1, 1 Jul 2011, 5°24′13.24084″N, 113°30′31.39787″E, 1709 m, 3 paratypes ( MCZ 147938 ) ; Sta. SA4, 29 Jun 2011, 5°36′08.70546″N, 113°40′11.51490″E, 2135 m, 2 paratypes ( MCZ 147939 ) ; Sta. SE1, 28 Jun 2011, 5°33′07.24983″N, 113°46′11.03389″E, 1894 m, paratype ( MCZ 147940 ) . Coll. J.A. Blake, Chief Scientist: Sta. 25 , 5 Jun 2011, 5°47′23.69441″N, 114 ◦ 10′48.45326″E, 1402 m, 2 paratypes ( MCZ 147941 ) ; Sta. 61 , 31 May 2011, 5°40′32.90422″N, 114°13′15.64893″E, 1050 m, 2 specimens ( MCZ 147942 ) ; Sta. WH-Jaring-SW, 4 Jun 2011, 5°43′13.87265″N, 114°08′13.15762″E, 1463 m, 1 specimen ( MCZ 147943 ) ; Sta. WH-Jokit-NE, 6 Jun 2011, 5°53′28.38401″N, 114°11′57.24436″E, 1400 m, 2 specimens ( MCZ 147944 ) ; Sta. WH-Jokit-SW, 5 Jun 2011, 5°46′27.76503″N, 114°07′33.98027″E, 1487 m, 4 paratypes ( MCZ 147945 ) . Coll. P. Neubert, Chief Scientist: Sta. AN7, 28 Jun 2011, 5°32′32.92542″N, 113°51′01.24946″E, 1585 m, 1 specimen ( MCZ 147946 ) ; Sta. DA2, 1 Jul 2011, 5°24′13.64904″N, 113°28′04.25708″E, 1760 m, 2 specimens ( MCZ 147947 ) ; Sta. DA4, 1 Jul 2011, 5°26′16.75004″N, 113°31′00.09025″E, 1851m, 1specimen ( MCZ147948 ) ; Sta. JA2, 30Jun2011, 5°27′55.53448″N, 113°32′57.69642″E, 1954 m, 2 specimens ( MCZ 147949 ) ; Sta. JA6, 30 Jun 2011, 5°31′02.11247″N, 113°36′27.60639″E, 1999 m, 3 spec- imens ( MCZ 147950 ) ; Sta. ME11, 25 Jun 2011, 5°20′47.88353″N, 113°33′12.39024″E, 1719 m, 2 specimens ( MCZ 147951 ) ; Sta. ME14, 26 Jun 2011, 5°25′20.73778″N, 113°39′02.48164″E, 1792 m, 2 specimens ( MCZ 147952 ) ; Sta. ME16, 26 Jun 2011, 5°24′24.44585″N, 113°35′28.03023″E, 1805 m, 1 specimen ( MCZ 147953 ) ; Sta. SA1, 29 Jun 2011, 5°34′05.57104″N, 113°39′44.09821″E, 2075 m, 1 specimen ( MCZ 147954 ) ; Sta. SA3, 3 Jul 2011, 5°35′09.05425″N, 113°38′49.25754″E, 2117 m, paratype ( MCZ 147955 ) ; Sta. SA5, 29 Jun 2011, 5°36′56.59222″N, 113°41′07.37801″E, 2162m, 1specimen ( MCZ147956 ) ; Sta. SE2, 29Jun2011, 5°31′21.71605″N, 113°42′18.56434″E, 1955 m, 5 paratypes ( MCZ 147957 ) ; Sta. SE5, 28 Jun 2011, 5°35′44.35485″N, 113°47′09.29726″E, 1947 m, 1 specimen ( MCZ 147958 ) ; Sta. TA1, 1 Jul 2011, 5°23′48.33272″N, 113°24′08.80925″E, 1866 m, 1 specimen ( MCZ 147959 ) ; Sta. TA2, 2 Jul 2011, 5°27′21.29666″N, 113°27′06.30764″E, 1981 m, 1 specimen ( MCZ 147960 ) ; Sta. TA3, 1 Jul 2011, 5°24′43.00263″N, 113°23′10.96051″E, 1896 m, 2 specimens ( MCZ 147961 ) ; Sta. TA5, 2 Jul 2011, 5°27′50.62360″N, 113°26′34.31837″E, 2008 m, 1 specimen ( MCZ 147962 ) .

Description. Body with 10 setigers ( Figs. 25A , 26 A–B) except for two juveniles with nine setigers each; up to 3.4 mm long, most specimens 1–1.5 mm long without anal cirri, holotype 2.3 mm; maximal width 1.0 mm without parapodia, 1.5 mm including parapodia but without setae; overall appearance widens from setigers 1 through 5 due to lengthening parapodia and increasingly long setae, then narrows through setiger 10. Palps long, oval, completely fused, often arched dorsally, narrowing to smoothly rounded anterior tip; palps with elongated internal structure with bulbous proximal end visible in several specimens ( Fig. 25G, I ); prostomium roughly oval in shape, with three club-shaped antennae in nearly transverse row, two lateral antennae only slightly anterior to medial one; eyes lacking. Peristomium shorter than following segments, with two very small rounded tentacular cirri. Nuchal cilia not evident, even when stained with Shirlastain A; small possible sense organ near lateral junction with prostomium seen on larger specimens ( Fig. 26E ). Eversible pharynx with three crowns, distal crown with 10 soft papillae ( Fig. 25 H–I); tooth absent. Proventricle in four setigers, barrel-shaped, posterior end gently ( Fig. 26A ) or sharply ( Fig. 26B ) tapered; ca. 30–35 rows of muscle cells; post-ventricle with dorsal circlet of cells retaining MG stain.

Dorsum biannulate through first three setigers, setiger 4 triannulate or quadriannulate, setigers 5–6 triannulate, annulations present but indistinct thereafter ( Figs. 25A , 26D ). Parapodia uniramous, short, broad, truncate on setiger 1, directed somewhat anteriorly ( Figs. 25A, G ; 26 A–B, D); parapodia remaining broad but becoming longer through setiger 5, together with setae giving wide, triangular aspect to anterior body; parapodia narrower, elongated, rectangular in subsequent setigers. Parapodia with very small anterior lobe, posterior lobe absent; dorsal lobe glandular, short, rounded, most obvious on setigers 1–5 ( Fig. 25G ). Rounded external structures (glands?) on anterior and posterior margins of anterior parapodia ( Fig. 25A , 26C ). Dorsal cirri long, thin, seen only on setiger 1, possibly lost from additional setigers; ventral cirri very thin, filiform, inserted midway between body and distal end of parapodia on all setigers ( Fig. 25A ).

Setae emerging from distal end and ventral face of parapodia; ventral setae most numerous in anterior setigers, present but in reduced numbers in posterior setigers. All setae compound, with heterogomph shafts, one side measuring 3 times length of other ( Fig. 25B, D ). Setiger 1 with at least 50 setae: 5–10 dorsal setae with curved shafts arched anteriorly, with very short (8–10 µm) serrated falcigerous blades with rounded blunt tips ( Fig. 25A, B ); additional setae with shafts directed laterally, with longer (20–50 µm) blunt, serrated blades and even longer (100–120 µm) thin, sinuous blades with serrations visible at proximal end; curved shafts and shortest blades not present after setiger 1. Blades becoming even longer (150–300 µm) in subsequent setigers ( Fig. 25F ), including several with very long, fine, whip-like spiniger-like tips, these giving a full, flowing appearance to anterior setigers. Mid-body setigers with about 35–40 setae, reduced to 20 or fewer in setigers 7–10. Each parapodium with stout aciculae in both anterior and posterior edges ( Fig. 25C ); aciculae numbering 3–5 per parapodium; some aciculae thinner, with bent tip ( Fig. 25E ), most with tapered pointed tip.

Pygidium with four thin, filiform cirri, easily lost ( Fig. 25A ).

Several specimens with eggs in coelom of setigers 6–10; specimens appearing bulky, bloated posteriorly; eggs measuring 60–85 µm in diameter.

Remarks. Anguillosyllis elegantissima n. sp. is most similar to A. lanai from Brazil; both species have elongated, tightly fused palps and 10 setigers, with the largest specimens of A. lanai measuring up to 2.0 mm in length and A. elegantissima n. sp. measuring up to 3.4 mm long. The free-palp species A. palpata and A. aciculata n. sp. are also large species, both reaching nearly 3 mm length; whereas, the majority of specimens of Anguillosyllis examined in this study were about 1 mm in length. At each of two stations (MCZ 147941 and MCZ 147947), one of two specimens of A. elegantissima n. sp. was considerably smaller than the other and had nine rather than ten setigers; these are considered to be juveniles. For example, at Sta. 25 (MCZ 147941), one specimen measured 2.8 mm long and the other measured a bit less than 1 mm long. The smaller specimen had nine fully developed setigers and a pointed bud with an acicula representing setiger 10.

Both A. lanai and A. elegantissima n. sp. have external glands associated with the dorsal bases of the parapodia: in A. lanai a single gland is reported near the insertion of the dorsal cirrus whereas in A. elegantissima n. sp. there are glands at both the anterior and posterior bases of the parapodium.

The strikingly uneven heterogomph shaft of A. elegantissima n. sp. is not present in A. lanai , although Fig. 13G in Barroso et al. (2017) suggests that one side may be longer than illustrated in Fig. 14 C–D.

Although indistinct and difficult to count, the number of muscle rows in the barrel-shaped proventricle were reported as ca. 12 for A. lanai compared with 30–35 in A. elegantissima n. sp. Especially when Shirlastain A is used, A. elegantissima n. sp. is clearly seen to have biannulate and triannulate (and possibly quadriannulate) setigers, whereas A. lanai does not. Anguillosyllis lanai has many fewer setae than A. elegantissima n. sp., which has up to 50 setae in the first setiger, with several curved anteriorly in a graceful arc, and 35–40 setae in mid-body setigers; whereas, A. lanai has only up to 15 setae in anterior setigers. Anguillosyllis elegantissima n. sp. has up to five aciculae per parapodium; A. lanai has only two aciculae per parapodium.

Etymology. The species name elegantissima is derived from the Latin word elegans, and refers to the graceful, Bali-dancer-like appearance of this species.

Records. South China Sea, off Brunei, 1050–2162 m.

Figures

FIGURE 13. Anguillosyllis hadra n. sp. Paratype (MCZ 148520):A, setigers 4–7; B, setigers 4–5; C, parapodial glands, setiger 5; D, parapodial gland, setiger 5; E, dorsal glands, setiger 5.

FIGURE 14. Anguillosyllis hampsoni n. sp. Paratype (USNM 1480263): A, entire specimen, dorsal view; B, falcigers from setiger 3; C, anterior end including setigers 1 and 2, dorsal view; D, setiger 8, dorsal view; E, setigers 10 and 11, dorsal view. Abbreviations: Acb—acicular bump, aL—anterior lobe, dC—dorsal cirrus, dL—dorsal lobe, nuc—nuchal cilia, pL—posterior lobe, vC—ventral cirrus.

FIGURE 25. Anguillosyllis elegantissima n. sp. Holotype (MCZ 147937): A, entire specimen, dorsal view. Paratype (MCZ 147957): B, setae from setiger 1. Paratype (MCZ 147940): C, aciculae from setiger 3; D, setae from setiger 1; E, acicula from setiger 10; F, seta from setiger 6; G, anterior end. Paratype (MCZ 147955): H, everted pharynx. Paratype (MCZ 147957): I, anterior end, dorsal view, pharynx everted.

FIGURE 26. Anguillosyllis elegantissima n. sp. Holotype (MCZ 147937): A, entire specimen, dorsal view. Paratype (MCZ 147945): B, dorsal view; Paratype from Sta. DA-1 (MCZ 147938): C, setigers 1–6, dorsal view, arrows indicate glandular structures at anterior and posterior bases of parapodia. Holotype (MCZ 147937): D, anterior end with Shirlastain A, dorsal view, showing biannulate and triannulate segments. Paratype (MCZ 147941): E, dorsal view of possible sensory structure on prostomium. Abbreviations: per—peristomium, pro—prostomium, pss—possible sensory structure.