Loimia megaoculata, Carrerette, Orlemir & Nogueira, João Miguel De Matos, 2015

Carrerette, Orlemir & Nogueira, João Miguel De Matos, 2015, The genus Loimia Malmgren, 1866 (Annelida: Terebellidae) off the Brazilian coast, with description of three new species and notes on some morphological characters of the genus, Zootaxa 3999 (1), pp. 1-31 : 8-16

Loimia megaoculata sp. nov.

( Figures 3–6 ; Table 1)

Type series. Holotype MZUSP 0 2363 (coll. 22º12'33"S 40º13'25"W, 99 m, 05.Jul.2009). Paratype 1 MZUSP 0 2364 (coll. 22º46'49"S 41º3'39"W, 78 m, 02.Jul.2009). Paratype 2 MZUSP 0 2365 (coll. 21º58'59"S 40º25'16"W, 52 m, 25.Feb.2009). Paratype 3 AM W.47671 (coll. 22º12'26"S 40º14'13"W, 92 m, 24.Feb.2009). Paratype 4 AM W.47672 (coll. 22º3'37"S 40º24'15"W, 55 m, 06.Jul.2007). Paratype 5 USNM 1273436 (coll. 22º1'18"S 40º20'19"W, 60 m, 24.Jul.2009). Paratype 6 USNM 1273437 (coll. 22º19'27"S 40º37'25"W, 73 m, 24.Jul.2009). Paratype 7 ZUEC 16674 (coll. 22º51'57"S 40º57'35"W, 92 m, 03.Jul.2009). Paraype 8 ZUEC 16675 and paratype 9 ZUEC 16676 (coll. 22º19'27"S 40º37'25"W, 73 m, 04.Jul.2009). Paratype 10 MZUSP 0 2366 (coll. 22º17'37"S 40º27'5"W, 103 m, 04.Jul.2009).

Additional material examined. Project HABITATS/PETROBRAS: State of Rio de Janeiro—Campos Basin: 21º42'33"S 40º9'5"W, 147 m, 25.Aug.2009, 4 specs; 22º7'35"S 39º54'21"W, 680 m, 30.Aug.2009, 4 specs; 22º19'27"S 40º37'25"W, 73 m, 04.Jul.2009, 3 specs; 22º17'37"S 40º27'5"W, 103 m, 04.Jul.2009, 1 spec.

Additional material examined for comparison. Loimia grubei sensu Blankensteyn (1988) — ZUEC 6131 (coll. 24°53'00"S 46°46'07"W, 47 m, 1 spec.); ZUEC 6043 (coll. 24°16'00"S 46°01'02"W, 50 m, 1 spec.). L. medusa sensu Blankensteyn (1988) — ZUEC 6044 (coll. 26°29'05"S 48°21'04"W, 38 m, 1 spec.). Loimia bandera Hutchings, 1990 : holotype, AM W.201924 (coll. 6 km S.E off Port Island, New Territories, 24 m, S/edge, coll. 5.Apr.1986); paratypes AM W.201926–7 (coll. Hong Kong, Tap Mun, 22°29'N 114°22'E, Apr.1986). Loimia batilla Hutchings & Glasby, 1988 : holotype, AM W.5162 (coll. Moreton Bay 20°26'S 147°05'E, Queensland, Australia, coll. 1971); paratype AM W.7097 (coll. Middle Banks off Tangalooma, 27°12'S 153°21'E, Queensland, Australia, coll. 1972); paratype AM W.7106 (coll. Middle Banks off Tangalooma, 27°12'S 153°21'E, Queensland, Australia, coll. 1972); paratype AM W.7107 (coll. Moreton Bay 20°26'S 147°05'E, Queensland, Australia, coll. 1970). Loimia triloba Hutchings & Glasby, 1988 : paratype AM W. 200558 (coll. Australia, Queensland, Low Isles, Great Barrier Reef, 16°23'S 145°34'E). Loimia medusa (Savigny in Lamark, 1818): neotype, LACM-AHF Poly 1656 (coll. Upper Persian Gulf, coll. Tetra Tech, Apr.1982, shallow shelf).

Description. Small, fragile, cylindrical worms, not markedly swollen anteriorly ( Figs 3 C–E; 5A, C), anterior segments compact, all about same length except for shorter segments 1 and 2; chaetigers progressively longer on segments 12–20. Complete specimens with 26–48 (26) segments, 3.7–5.1 (4.1) mm long, 0.3–0.9 (0.3) mm wide (Table 1). Preserved body colourless, except for dark brown transverse ventral band at intersegmental line of segments 2 and 3. Prostomium at base of dorsal side of upper lip; basal part of prostomium with 2 rows of eyespots, upper row with 5–6 large eyespots at each side, progressively smaller laterally, arranged in oblique band ( Fig. 3 A, C, G); other row at posterior margin of basal part of prostomium, with much smaller, irregularly scattered eyespots, in broad band; distal part of prostomium forming shelf-like process from which short and cilindrical buccal tentacles originate ( Figs 3 A–G; 5A–F). Peristomium restricted to lips; upper lip short, wider than long, nearly circular and folded laterally; lower lip short, rectangular, cushion-like, partially hidden by membrane connecting lobes of segment 1 ( Figs 3 A–G; 5A–I). Segment 1 visible entirely, dorsally short, with relatively short paired lobes originating dorso-laterally, aligned with line of notopodia; lobes with oblique dorsal margins, continuing across ventrum as low lobes; distally rounded, roughly circular, barely reaching mid-length of upper lip, then oblique towards lower lip; tips and ventral edges connected by membrane ( Figs 3 A–G; 5A–B, E–F). Segment 2 short, conspicuous laterally and dorsally, ventrally separated from segment 3 forming first mid-ventral shield ( Figs 3 A–F; 5B, F); segment 3 longer than the previous ones, with paired low lobes, thin, ear-like, distally rounded; with wide bases about as large as tips of lobes, originating dorso-laterally, near anterior margin of first pair of notopodia (these on segment 4), terminating aligned with ventral edge of neuropodia, laterally to partially fused mid-ventral shield of segments 3–4 ( Figs 3 A–G; 5A–B, E–I); dorsal margins oblique, terminating far from bases of branchiae ( Figs 3 A–G; 5A–B, E–I); segment 4 partially fused mid-ventrally to the mid-ventral shield of segment 3; following anterior segments about same size. Three pairs of branching branchiae, on segments 2–4, each with short basal stem ( Fig. 5 C–F); pairs of branchiae progressively shorter, all ventrally aligned. Rectangular, smooth, swollen midventral shields on segments 2–12, slightly crenulated and completely separated from each other, smooth from segment 5, progressively narrower to last ( Figs 3 A–B, D–F; 5A–B); a distinctly narrower pad on segment 13 is frequently present, divided by two transverse bands; from segment 14, shields replaced by mid-ventral groove extending posteriorly ( Figs 3 A–B; 5A–B). Cylindrical, short notopodia, on segments 4–20, bearing narrowlywinged chaetae in both rows, those from posterior row longer, with wings on distal half of chaetae ( Figs 4 A–D; 6A–C). Neuropodia beginning from segment 5, as low rectangular ridges slightly raised from surface of body until segment on which notopodia terminate ( Figs 3 A–B, D–F; 5A–B, E–F), thereafter as elongate, prominent pinnules ( Fig. 3 A, H); neuropodia bearing pectinate uncini, arranged in double rows on segments 11–20, tori aligned ventrolaterally from segment 5 to posterior body, rows partially intercalated on ventral edges of neuropodia, then completely separate, uncini in crest-to-crest to back-to-back arrangement ( Figs 4 D; 6F–G). Uncini pectinate, higher than long, with concave base, prominent, triangular heel directed backwards, and prow downwardly directed, continuing as long ligament ( Figs 4 E–H; 6E–I); uncini of region with notopodia with six teeth, progressively shorter upwards, basal-most tooth larger, in line with prow, distal-most tooth as short spine on top, barely visible under light microscope, conspicuous under SEM ( Figs 4 D–F; 6E–H); neuropodia from region after notopodia terminate with uncini with up to 6–7 teeth, frequently varying within tori, sometimes distal-most tooth sided by one minute tooth at each lateral ( Figs 4 G; 6I). Nephridial and genital papillae not visible. Anus surrounded by crown of short, rounded papillae ( Fig. 3 H).

Remarks. Loimia megaoculata sp. nov., is shorter than most species of Loimia and has large eyespots, to our knowledge not found in any other species of the genus. Loima megaoculata sp. nov., has eyespots arranged in two rows, the upper one with 5–6 large eyespots on each side, beginning dorso-laterally and progressively smaller lateral and upwards, with other row at posterior margin of basal part of prostomium, with small, irregularly scattered eyespots.

Two other species of Loimia have eyespots on basal part of prostomium, L. triloba Hutchings & Glasby, 1988 (Table 2), originally described from Australia ( Hutchings & Glasby 1988, 1995; Londonõ-Mesa & Carrera-Parra 2005; Londonõ-Mesa 2009) and L. medusa ( Hutchings & Glasby 1995; JMMN personal observation). In addition to the eyespots, L. triloba also has uncini with 5–6 teeth ( Fig. 2 D, F, K, L), similar to L. megaoculata sp. nov. However, L. triloba differs from L. megaoculata sp. nov., in having two rows of small eyespots, arranged laterally, lacking larger eyespots as in L. megaoculata sp. nov. In addition, L. triloba has lobes of the segment 1 continuing dorsally as free, completely encircling the body, lateral lobes of segment 3 with the base narrower than the tip, and a pair of shorter lateral lobes on segment 4 ( Fig. 1 B, G). In contrast, in L. megaoculata sp. nov., the lobes of the segment 1 originate dorso-laterally, at line of notopodia, with large mid-dorsal gap, the lobes of segment 3 have bases at least as wide as tips, and there are no lobes on segment 4.

The neotype of L. medusa also has eyespots, but few, only laterally ( Hutchings & Glasby 1995; JMMN, personal observation). Loimia medusa differs from L. megaoculata sp. nov., however, in addition to the arrangement and shape of the eyespots, by having a pair of large, high and circular lobes on segment 1; nearly circular ones on segment 3, with narrower base than tip, upper dorsal margins reaching the bases of the branchiae; rectangular and progressively longer mid-ventral shields, as well as uncini with 4–5 teeth only ( Figs 1 D, J; 2C, G, L). In contrast, L. megaoculata sp. nov., also has distally rounded, roughly circular lobes of segment 1, but they are distinctly shorter than those of L. medusa , the lobes of segment 3 have bases at least as wide as tips, the mid-ventral shields are also rectangular, but they are evenly-sized, instead of progressively longer, and the uncini have 6–7 teeth.

Four other species resemble L. megaoculata sp. nov., with regard to the presence of ventral shields extending to segment 12, L. bandera , L. batilla , L. medusa and L. bermudensis Verrill, 1900 , although in L. megaoculata sp. nov., a distinctly narrower pad on segment 13 is also frequently present. A comparison of all these species is provided in Table 2, together with the other species used for comparisons with the remaining species described in this paper.

TABLE 2. List of species of Loimia used for comparison with the species described in this paper, with the main morphological characters used for the identification. Sources: Hutching and Glasby (1988); Hutchings (1990); characters of Loimia bandera , L. batilla , L. medusa , and L. triloba examined directly from type-material.

Type locality Eyespots Lateral lobes, segment 1 Lateral lobes, segment 3 Ventral Nephridial and Uncini (number of

shields (segs) genital papillae teeth)

(segs) bandera Pacific Ocean, Hong Absent Originating dorso-laterally, Originating laterally to 3– 12, 6–8 5–6

Kong close to origin of branchiae of origin of branchiae, rectangular

segment 2, continuing across almost fused to anterior

ventrum as low lobes; lobes margin of segment 3

distally straight

batilla Queensland, Australia Absent Mid-dorsally fused to each Nearly circular, oblique, 3–12 3, 6–8 5–6

other, forming low collar originating laterally to the across dorsum; oblique dorsal origin of branchiae,

margins, relatively short and extending across ventrum distally rounded

bermudensis Bermuda, Atlantic Ocean Absent Large, projecting forwards, Wide base, nearly same 3–12 – 5

well-developed, extending length as lobes of

laterally surrounding upper segment 1, terminating

lip and ventrally lower lip away from mid-ventral

shield, and with dorsal

edge almost as long as

first lobe, slightly

developed, not covering

base of branchiae

crassifilis SE Asia, Philippines Absent Foliaceous lobes, with rounded 5–11 – 4–5 end, connecting each other

by a membrane. Well expanded

grubei Philippine Islands Absent High, with rounded end Low, rounded end 3–14 – 5–6

......continued on the next page TABLE 2. (Continued)

Type locality Eyespots Lateral lobes, segment 1 Lateral lobes, segment 3 Ventral Nephridial and Uncini (number (morphology) (morphology) shields genital papillae of teeth: (Aterior (segments) (segments) X Posterior)

ingens SE Asia, Philippines Absent Mid-dorsally fused to each Well developed, with pair – – 3–7

other, forming low collar arising from junction of

across dorsum segments 2–3

medusa Red Sea Present Large and distally rounded, Large, nearly circular, with 3–12 3, 6–8 4–5

dorso-laterally, aligned with narrower base, dorsal margin

notopodia of segment 4, reaching bases of branchiae

with oblique dorsal margin

minuta Dry Tortugas, Florida Absent Projecting forwards, With short base, not connected 2–17 – 5

laterally surrounding upper to ventral shield, and with

lip dorsal edge slightly developed

salazari Xcacel, Mexican Absent Covering both upper and Well developed dorsal lobe 2–14, 17 – 4–5 Caribbean lower lips; laterally, covering base of branchiae

reaching level of notopodia

triloba Three Isles , Queensland: Dark, arranged Mid-dorsally fused to each Nearly circular originating at 3–16 6–8 5–6 Great Barrier Reef, in 2 lateral rows other, forming low collar level of dorsal edge of

across dorsum; oblique neuropodia, terminating far

dorsal margins and distally from ventral edges of

rounded neuropodia

Loimia bandera was originally described from Hong Kong ( Hutchings 1990) and differs from L. megaoculata sp. nov., in having a narrow basal V-shaped part of the prostomium lacking eyespots, and uncinial teeth exhibiting minor differences in size from the basal- to the distalmost teeth ( Fig. 2 A, E), while in L. megaoculata sp. nov., the basal part of the prostomium is longer, not V-shaped and has eyespots, and the uncinial teeth are markedly shorter distally. In addition, the mid-dorsal gap between the lobes of the segment 1 of L. bandera is distinctly narrower than present in L. megaoculata sp. nov. ( Fig. 1 F), while the lobes of the segment 3 are larger and oblique, instead of rounded. The Australian species L. batilla also differs from L. megaoculata sp. nov., in the same characters as L. bandera , i.e., prostomium lacking eyespots, and uncinial teeth exhibiting minor differences in size from the basalto the distalmost teeth (see Table 2).

Loimia bermudensis Verrill, 1900 , which was described from Bermuda and has never been collected again since the original description ( Londoño-Mesa 2009), differs from L. megaoculata sp. nov., in the number of uncinial teeth, 5 teeth per uncinus throughout the body, instead 6 on anterior body chaetigers and 7 on posterior ones, as in L. megaoculata sp. nov.. In addition, L. bermudensis has all uncinial teeth of similar size, while in L. megaoculata sp. nov., considerable differences occur ( Figs 4 D–G; 6E–I).

Finally, L. megaoculata sp. nov., shares some characteristics with L. armata sp. nov., also described in the present paper, as discussed in the Remarks of the description of that species (see below).

Etymology. We attribute to this taxon the epithet “ megaoculata ” in reference to the presence of the large eyespots on the basal part of prostomium.

Type locality and distribution: State of Rio de Janeiro (Campos Basin).

Figures

FIGURE 1. Loimia batilla (Holotype, AM W. 5162): (A). Anterior part, ventral view; (I). Anterior part, lateral view. L. triloba (Paratype, AM W. 200558): (B). Anterior part, ventral view; (G). Anterior part, dorsal view. L. bandera (Holotype, AM W. 201924): (C). Anterior part, ventral view; (F). Anterior part, dorsal view. L. medusa (Neotype, LACM-AHF Poly 1656): (D). Anterior part, ventral view; (J). Anterior part, lateral view. L. armata sp. nov. (Paratype, MZUSP 02368): (E). Anterior part, ventral view; (H). Anterior part, ventro-lateral view. Numbers refer to the segments; P = Prostomium; ul = upper lip. Scale bars: A – B = 1 mm; C – G = 500 µm; H – J = 400 µm.

FIGURE 2. Loimia bandera (Paratype, AM W. 201927): (A). Anterior uncini, segment 5; (E). Uncini of the segment 11; (H). Posterior uncini, segment 25. L. batilla (Paratype, AM W. 7100): (B). Anterior uncini, segment 5; (I). Posterior uncini, segment 25. L. medusa (Neotype, LACM-AHF Poly 1656): (C). Anterior uncini, segment 5; (G). Uncini of the segment 11; (J). Posterior uncini, segment 25. L. triloba (Paratype, AM W. 200558): (D). Anterior uncini, segment 5; (F). Uncini of the segment 11; (K). Posterior uncini, segment 25; (L). Posterior uncini, segment 34. Scale bars: A, C – D, G = 50 µm; B = 30 µm; E = 3 µm; F = 5 µm; H – L = 20 µm.

FIGURE 3. Loimia megaoculata sp. nov. (Holotype, MZUSP 02363): (A). Complete animal, ventral view; (B). Anterior part, ventral view; (C). Anterior part, dorsal view; (D). Anterior part, right lateral view; (E). Anterior part, left lateral view; (F). Detail of the anterior part, lobes on anterior segments, ventral view; (G). Detail of the anterior part, prostomium and lobes on segment 3, dorsal view (letter P is on segment 1); (H). Detail of the pygidium. Numbers refer to segments; II = lower lip; P = prostomium; ul = upper lip. Scale bars: A = 1 mm; B – C = 500 µm; D – F = 400 µm; G – H = 200 µm.

FIGURE 4. Loimia megaoculata sp. nov. (Holotype, MZUSP 02363): (A). Notopodium of the segment 17; (B). Detail of the notopodium of the segment 20; (C). Detail of the notochaetae of the segment 10; (D). Uncini of the segment 12; (E). Detail of an uncinus of the segment 8; (F). Uncini of the segment 19; (G). Detail of an uncinus of the segment 22. Scale bars: A = 50 µm; B = 30 µm; C = 20 µm; D, F = 5 µm; E, G = 3 µm.

FIGURE 5. Loimia megaoculata sp. nov. (Paratype, MZUSP 02366): (A). Anterior part, lateral view; (B). Anterior part, ventral view; (C). Anterior part, dorsal view; (D). Detail of the anterior part, dorsal view; (E). Detail of the anterior part, ventral view; (F). Anterior part, right lateral view; (G). Anterior part, left lateral view; (H). Detail of anterior part, lobes on anterior segments, lateral view; (I). Detail of anterior part, lobes on anterior segments, dorso-lateral view. Numbers refer to segments; II = lower lip; P = prostomium; ul = upper lip. Scale bars: A = 200 µm; B – C = 300 µm; D – F = 400 µm; G – I = 500 µm.

FIGURE 6. Loimia megaoculata sp. nov. (Paratype, MZUSP 02366): (A). Notopodium of the anterior segment; (B). Detail of notopodia of segments 9 – 10; (C). Detail of notochaetae of segment 19; (D). Close up view of wing on chaetae from posterior row of posterior region with biramous parapodia; (E). Uncini from anterior segment; (F). Uncini from segment 15, double rows of uncini; (G). Detail of uncini from segment 17; (H). Uncini from posterior region with biramous parapodia; (I). Detail of an uncinus from posterior body. Scale bars: A = 50 µm; B = 30 µm; C = 20 µm; D = 2 µm; E – G = 3 µm; H – I = 4 µm.