Exogone brasiliensis, Fukuda & Menezes-Moura & Guimarães & Ruta, 2019

Fukuda, Marcelo Veronesi, Menezes-Moura, Andrezza Ribeiro, Guimarães, Carmen Regina Parisotto & Ruta, Christine, 2019, A new species of Exogone Ørsted, 1845 (Annelida: Syllidae: Exogoninae) from Brazilian waters, Papéis Avulsos de Zoologia 59, pp. 1-8 : 2-6

Exogone brasiliensis sp. nov.

( Figs. 1‑3 )

Exogone (Exogone) sp. 3 sensu Fukuda (2010): 144 -146, Fig. 42.

Exogone (Exogone) sp. nov. C sensu Menezes (2012): 70 -73, Fig. 23.

Type material: Holotype ( MZUSP 3395 ): Campos Basin, State of Rio de Janeiro, offshore, 2246’54”S 41°03’33”W, 77 m, 02 Jul 2009. Paratypes: Campos Basin, State of Rio de Janeiro, offshore, 2142’53”S 40°10’15”W, 98 m: 16 specs ( ZUEC-POL 21353 ); 223’45”S 40°9’59”W, 76 m: 16 specs ( MNRJP 002205 ), 06 Jul 2009; 2246’54”S 41°3’33”W, 77 m: 18 specs ( MZUSP 3396 , paratype 1; MZUSP 3397 , 17 paratypes), 02 Jul 2009. State of Sergipe, offshore, 10°52’16”S 36°34’24”W – 50 m: 1 spec ( CZUFS-POL 00001 , 1 paratype).

Additional material analysed: ‘REVIZEE’. State of Rio de Janeiro, 22°02’S 40°05’W, 93 m: 1 spec ( MZUSP 3461 ), 02 Mar 1998 ; 23°08’S 41°00’W, 100 m: 1 spec, 01 Mar 1998; 23°20’S 41°22’W, 110 m: 7 specs ( MZUSP 3462 ), 28 Feb 1998 ; 23°26’S 41°15’W, 145 m: 4 specs, 27 Feb 1998; 24°02’S 43°30’W, 147 m: 1 spec, 14 Feb 1998. State of Santa Catarina, 29°28’S 48°09’W, 210 m: 1 spec, 22 Mar 1998. ‘ Habitats’. State of Rio de Janeiro, Campos Basin , 21°09’9”S 40°16’7”W, 103 m: 26 specs ( MZUSP 3511 , 3512 ), 21 Jul 2009 ; 21°17’31.899”S 40°48’19.935”W, 24 m: 2 specs ( MZUSP 3405 ), 08 Mar 2009 ; 21°28’02.517”S 40°56’20.614”W, 16 m: 1 spec ( MZUSP 3401 ), 10 Mar 2009 ; 21°45’13”S 40°14’70”W, 67 m: 20 specs ( MZUSP 3407 , 3408 ), 14Mar 2009 ; 22°23’39”S 40°20’40”W, 153 m:5specs ( MZUSP 3429 ), 23 Fev 2009 ; 22°03’45”S 40°09’59”W, 75 m: 13 specs ( MZUSP 3433 , 3434 ), 25 Fev 2009 ; 22°46’54”S 41°03’33”W, 78 m: 39 specs ( MZUSP 3419 ), 22 Fev 2009 ; 23°11’30”S 41°00’47”W, 150 m:10 specs ( MZUSP 3414 ), 21 Fev 2009 ; 23°36’14”S 41°21’29”W, 142 m: 2 specs ( MZUSP 3411 ), 01 Mar 2009. ‘ Ambes’. State of Rio de Janeiro, Espírito Santo Basin , 19°33’20”S 38°42’52”W, 160 m: 2specs, 16 Jul 2013 ; 19°43’14”S 39°33’34”W, 50 m:6 specs, 14 Jul 2013; 21°03’31”S 40°22’59”W, 39 m: 3 specs, 11 Jul 2013; 20°34’53”S 40°06’27”W, 49 m: 43 specs, 12 Jul 2013; 20°35’23”S 39°55’01”W, 146 m: 2 specs ( MZUSP 3517 , 3518 ), 13Jul2013. ‘Petro/mar’. State of Alagoas, 10°18’02”S 36°07’04”W, 30 m: 1 spec ( CZUFS-POL 00006 ), Jun 2002, 1 spec ( CZUFS-POL 00007 ), Dez 2002, 1 spec ( CZUFS-POL 00008 ), Jun 2003. ‘Petro/mar’. State of Sergipe, 10°57’03”S 36°50’17”W, 30 m: 1 spec ( CZUFS-POL 00005 ), Jun 2002. ‘Marseal’. State of Sergipe, 10°52’32”S 36°49’20”W, 50 m :

6 specs ( CZUFS-POL 00002 ) ; 11°10’00”S 36°52’17” W, 50 m: 1 spec ( CZUFS-POL 00003 ) ; 10°10’34”S 36°08’17”W, 50 m: 1 spec ( CZUFS-POL 00004 ) .

Comparative material analysed: Exogone aristata Hartmann-Schröder, 1982 , Australia, Western Australia, Beacon Island, NE entrance to Goss Passage (28°27’54”S 113°46’42”E), in coral substrate covered by algae, 24 m: 1 spec ( AM W26989), coll. P. Hutchings, 25 May 1994, det. G. San Martín, 2000; Beacon Island, off S end of Long Island (28°28’48”S 113°46’18”W), in dead coral substrate covered by coralline algae, 4-5 m: 3 specs ( AM W26990), coll. P. Hutchings, 25 May 1994, det. G. San Martín, 2000. Exogone dwisula Kudenov & Harris, 1995 , USA, California, Santa Maria Basin, between Purissima Point and Point Arguello (34°42’34”N 120°47’54”W), 100 m: 2 specs (paratypes, AM W22190) and 3 specs (paratypes, USNM 170913), coll. ‘DSR/V Diaphus’, 28 Jul 1984, det. L. Harris, 1995. Exogone heterosetosa McIntosh, 1885 , Australia, Western Australia, Long Island, Goss Passage (28°28’18”S 113°46’18”W), on dead coral covered with coralline algae and boring bivalves, 8 m: 10 specs ( AM W27057), coll. C. Bryce, 22 May 1994, det. G. San Martín, 2000. Exogone longicornis Westheide, 1974 , Ecuador, Galápagos Islands, Santa Cruz: 1 spec (holotype, ZMH P-13618), coll. and det. W. Westheide, 1972, 1974. Exogone mompasensis Martínez, Adarraga & San Martín, 2002 , Spain, Basque Country, Guipúzcoa, San Sebastián, Punta de Mompás (43°20’10”N 01°57’40”E): 12 specs (holotype, MNCN 16.01/8710; paratypes, MNCN 16.01/10118), coll. 08 Apr 1997. Exogone rolani San Martín, 1991, USA, Florida, Port Everglades (26°07’42”N 80°04’48”W), 17 m: 2 specs (paratypes, USNM 101327).

Description: Body thin and elongate, longest specimen analysed ca. 6 mm long, 0,17 mm wide. Palps triangular, distally rounded, almost entirely fused, with conspicuous line of fusion and, sometimes, distal notch ( Figs. 1A , 2A ). Prostomium ovate, shorter than palps, with two pairs of nearly coalescent eyes in trapezoidal arrangement; anterior eyespots absent; antennae inserted close to each other, slightly anteriorly to anterior pair of eyes; median antenna elongated, subdistally thin, almost seven times as long as lateral antennae;lateral antennae digitiform to ovate ( Figs. 1A , 2A ). Peristomium shorter than following chaetigers, sometimes covering posterior part of prostomium, including posterior pair of eyes; peristomial cirri ovate,slightly shorter than lateral antennae ( Figs.1A , 2A ). Dorsal cirri small, rounded to ovate, shorter than peristomial cirri, present on all chaetigers ( Figs. 1A , 2A ); ventral cirri small, rounded to ovate, with same size as dorsal ones, or slightly smaller ( Fig. 2B ). Parapodia 1-5 with ca. 10 falcigers each; shafts of falcigers subdistally spinulated throughout; on chaetigers 1 and 2, shafts of the two dorsalmost falcigers modified, subdistally inflated, with acute tip ( Fig. 1B ); blades of anteriormost falcigers modified, 1-3 dorsalmost sometimes spinulated with short spines, distally bidentated ( Figs. 1C , 3H ), remaining anterior body falcigers with blades progressively longer ventralwards, smooth, with subdistal tooth conspicuously longer, distal tooth reduced ( Figs. 1D , 3 A-B, G-H); blades 6-12 µm long, ventralmost ones approximately twice as long as dorsalmost ones. From proventricle level onwards, parapodia with 1 spiniger-like chaeta and 3-4 falcigers each; spiniger-like chaetae with subdistally enlarged shafts, with coarse spinulation forming ridges in some chaetae( Fig.3D );blades of spiniger-like chaetae relatively short, ca. 20 µm long on midbody ( Figs. 1E , 3 C-D), 16- 12 µm on posterior body ( Figs. 1F , 3D ), unidentate, with short basal spinulation; blades of falcigers spinulated, bidentate, with subdistal tooth larger than distal one and subtle dorso-ventral gradation in length, blades ca. 10- 8 µm long on midbody, slightly shorter on posteri- or body ( Figs. 1 E-F, 3C, E-F). Dorsal simple chaetae on anterior body slightly sigmoid, subdistally spinulated, with acute tip ( Fig. 1G ), protruding for short extension from parapodial lobes; from midbody onwards, dorsal simple chaetae nearly straight and subdistally enlarged on one side, with acute, rounded tip ( Figs. 1H , 3 C-D); ventral simple chaetae only present on posteriormost chaetigers, sigmoid, bidentate, with subdistal tooth larger than distal one ( Figs. 1I , 3I ). Anterior body parapodia with 2 aciculae each, distally inflated, hollow ( Fig. 1J ); from midbody onwards, parapodia with only 1 acicula each, similar to anterior body aciculae, but progressively thicker towards posterior body ( Fig. 1K ). Pygidium with a pair of long anal cirri, slightly longer than median antenna ( Fig. 2E ). Pharynx extending through 5-6 segments, with opening densely surrounded by cilia and conical tooth in anterior ⅓ of its length ( Figs.1A , 2 B-D); proventricle extending for 5-6 segments, with ca. 40 rows of muscle-cells ( Fig. 1A ).

Remarks: Exogone brasiliensis sp. nov. is characterized by having the two dorsalmost falcigers modified on chaetiger 1 and 2, with shafts subdistally inflated, with acute tip; falcigers of chaetigers 1-5 modified, ventralmost blades smooth, with subdistal tooth distinctly larg- er than the distal one, conspicuously longer than those from chaetiger 6 onwards; dorsal simple chaetae, from midbody onwards, subdistally enlarged on one side, with acute, rounded tip; and proventricle extending for 5-6 segments, with ca. 40 rows of muscle-cells.

Exogone brasiliensis sp. nov. belongs to a group of species of the genus that presents falciger blades with subdistal tooth larger than the distal one and elongat- ed median antenna, reaching beyond tip of palps. This group also encompasses Exogone aristata , Exogone heterosetosa , Exogone longiantennata Hartmann-Schröder, 1979 , Exogone longicornis , Exogone mompasensis and Exogone rostrata Naville, 1933 . However, E. aristata differs from E.brasiliensis sp. nov. by the presence of aristae (large distally directed spines, usually extending beyond the tip of the chaeta) on falciger blades and on dorsal and ventral simple chaetae; E.longiantennata has no eyes neither dorsal cirri on chaetiger 2; both E.longicornis and E.rostrata present shafts of spiniger-like chaetae of chaetiger 1 with a subdistal thickening forming a triangular process, which is absent in E. brasiliensis sp. nov. Finally, E. heterosetosa and E. mompasensis differ from E. brasiliensis sp. nov. by having spiniger-like chaetae modified, with shafts distally inflated and strongly spinulated, and relatively short, triangular blades.

Exogone dwisula and Exogone naidina also have compound chaetae of the first chaetigers with modified blades. However, different from Exogone brasiliensis sp. nov., modified falciger blades in both these species present no denticle corresponding to the distal tooth, and they show a pronounced spine at the base of the blades, sometimes distally directed, giving the blades the appearance of a “can opener” ( Kudenov & Harris, 1995; San Martín, 2003, 2005). In addition, both E. dwisula and E.naidina have dorsal simple chaetae on posterior body sigmoid, subdistally inflated and spinulated, with acute tip, while E.brasiliensis sp. nov. presents dorsal simple chaetae straighter than usual for the genus, subdistally swollen only on one side, distally rounded.

Perhaps the most similar species to Exogone brasiliensis sp. nov. is Exogone rolani , by having enlarged median antenna, dorsal cirri on all chaetigers, falcigers with subdistal tooth larger than distal one, and shafts of falcigers on chaetigers 1-5 modified, with large, pointed, oblique tip ( Paresque et al., 2014). However, E. rolani differs from E. brasiliensis sp. nov. by having spiniger-like chaetae on all chaetigers and with longer blades than those of E. brasiliensis sp. nov., up to 25 µm long, while spiniger-like chaetae are absent from the first 5 chaetigers of E. brasiliensis sp. nov., and the longer blades are up to 20 µm long. Furthermore, E.rolani presents dorsal simple chaetae with a more common morphology to the genus, sigmoid, subdistally spinulated, with acute tip (see Paresque et al., 2014, figs. 7C, G, K), while, from midbody onwards, dorsal simple chaetae of E. brasiliensis sp. nov. are quite unique, nearly straight and subdistally swollen on one side only, distally rounded. Finally, despite extending for a similar number of chaetigers, the proventricle in E. brasiliensis sp. nov. presents more muscle cell rows than that of E. rolani (ca. 40 × ca. 29).

Etymology: This species was named brasiliensis because the type locality is in Brazil and the species presents a large distribution along the coast.

Distribution: Atlantic Ocean: Brazil (Alagoas, Sergipe, Espírito Santo, Rio de Janeiro and Santa Catarina).

Figures

Figure 1. Exogone brasiliensis sp.nov. (A) anterior body,dorsal view;(B) compound chaeta,chaetiger 1; (C) dorsalmost compound chaetae,anterior body;(D) ventralmost compound chaetae, anterior body; (E) compound chaetae, midbody; (F) compound chaetae, posterior body; (G) dorsal simple chaeta, anterior body; (H) dorsal simple chaeta,posterior body;(I) ventral simple chaeta;(J) aciculae,anterior body;(K) acicula,posterior body.Scale bars:A,150 µm;B-K,10 µm.

Figure 2. Exogone brasiliensis sp. nov., SEM. (A) anterior body, dorsal view; (B) anterior body, ventral view (pharynx everted); (C-D) everted pharynx, frontal and ventral view,respectively;(E)pygidium,dorsal view.Scale bars:A-B,50 µm; C-D,10 µm;E,20 µm.

Figure 3. Exogone brasiliensis sp. nov.,SEM.(A-B) ventralmost falcigers,chaetigers 2 and 3, respectively;(C) chaetae, mid- to posterior body;(D) spiniger-like and dorsal simple chaetae,posterior body;(E) ventralmost falciger,posterior body;(F) dorsalmost falciger,midbody;(G) chaetae,chaetiger 4; (H) falcigers,chaetiger 4; (I) ventral simplechaeta.Scale bars:A-B,D,F,H, 2 µm;C,10 µm; E, I, 1 µm;G,5 µm.