Lumbrineriopsis dulcis, Scamparle Teodoro & Steiner & Amaral, 2023

Scamparle Teodoro, Nalita Maria, Steiner, Tatiana Menchini & Amaral, Antonia Cecilia Zacagnini, 2023, A new species of Lumbrineriopsis (Annelida, Eunicida, Lumbrineridae) from southeastern Brazil, ZooKeys 1174, pp. 175-189 : 175

Lumbrineriopsis dulcis sp. nov.

Figs 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8

Description.

Holotype complete, 0.5 mm wide, 23 mm long, 178 chaetigers. Complete adult paratypes (16 specimens): 0.3-0.75 mm wide, 4.5-43 mm long, 45-254 chaetigers. Incomplete adult paratypes (79): 0.3-0.9 mm wide, 1-71 mm long, 12-243 chaetigers. Complete juveniles paratypes (4): 0.2 mm wide, 5-11 mm long, 56-75 chaetigers. Incomplete juvenile paratypes (14): 0.1-0.25 mm wide, 5-11 mm long, 11-54 chaetigers. Body yellow or whitish in preserved specimens. Prostomium long, acuminate, 1.5-2.5 times longer than peristomium (Figs 1A, B , 4 ). Peristomial rings slightly demarcated, both with equal length or first ring twice as long as the second one, both slightly narrower than the following segments (Figs 1A, B , 4 , 5A ); without mouth pads. Jaw apparatus light brown (Fig. 7 ). MI forceps-like, with attachment lamella, basal external projection, basal inner portion sharper and connected to the maxillary carriers (Figs 1E , 7E ). Maxillary carriers 1.5 to twice as long as MI, with tiny irregular structures in anterior end (Figs 1E , 7E ). MII connected to the inner base of MI by a ligament, 6 or 7 teeth with curved and rounded end, the 2 basal teeth being the smallest (Figs 1E, F , 7E, F ); attachment lamella small and not easily visible (Fig. 7F ). MIII with 2 aliform expansions and 1, rarely 4 or 5 teeth (Figs 1E, G , 7E, F ). Broad MIV with 11-16 denticles of the same size, tiny irregular structures in attachment lamella (Figs 1E, H , 7F ). Maxillary formula: MI = 1 + 1, MII = 6 + 7, MIII = (1-5) + (1-5), MIV = (11-16) + (11-16). Mandibles composed of 2 juxtaposed rods free one to another along entire length (Fig. 7 ). Inner margin with a more evident longitudinal chitinous cord, ending distally in a broad plate with 10-16 denticles on its border (Figs 1C, D , 7A , 8A, B ); more evident in juveniles (Figs 1D , 8A, B ), sometimes not visible in adults (Fig. 7B-F ). Calcareous plate and growth rings of mandibles absent. Parapodia with pre-chaetal lobe short and slightly triangular in anterior and median region (Figs 2A-C , 6A-C , 8D-G ), and truncated in post-median and posterior regions (Figs 2D-F , 5C , 6D-F ). Post-chaetal lobe triangular to digitiform, longer than the pre-chaetal lobe; no morphological variation along the body. Two simple limbate chaetae in the supra-acicular bundle and 1 simple bidentate hooded hook in the subacicular bundle, both present throughout the whole body (Figs 2 , 3 , 5C , 6A, C, F , 8D-G ). Limbate chaetae with smooth edge, equal in size along the whole body, ventral ones with slightly wider limb. Hooks increasing gradually in size throughout the body; both teeth straight and directed distally, of equal size in first chaetigers (Fig. 3B, E ), from chaetiger 5, inferior tooth slightly directed laterally, from chaetiger 10, inferior larger than the superior (Figs 3H, L , 8D-G ). Hoods gradually shorter along the body. Parapodia with 2 transparent to light-brown aciculae (Figs 2 , 3C, F, I, J, M, N , 8D-G ), ventralmost projecting beyond the parapodium (Fig. 8D-G ) and larger from median region (Figs 2D , 8F, G ); some individuals with 3 aciculae in posterior region, about chaetiger 100 (Fig. 2F ). Pygidium rounded, without anal cirri (Fig. 5D ).

Etymology.

The specific epithet “dulcis” is a tribute to the Doce River, which flows into an estuary in the Atlantic Ocean, where L. dulcis is recorded.

Materials examined.

117 specimens, including 99 adults and 18 juveniles, from Espirito Santo (ES) and Rio de Janeiro (RJ) states. Holotype: ZUEC-POL 21500 (ES), 21°4'4.76"S, 40°14'14.14"W, 150 m, 23 Jan 2012 . Paratypes preserved in 70% alcohol (each lot with 1 specimen): ZUEC-POL 21501 (ES), 19°42'26.81"S, 39°39'5.27"W, 14 m, 15 Jul 2011; ZUEC-POL 21502 (ES), 19°49'52.15"S, 39°52'24.51"W, 30 m, 16 Jul 2011; ZUEC-POL 21504 (ES), 20°11'25.75"S, 40°2'15.87"W, 40 m, 13 Jul 2013; ZUEC-POL 21505 (ES), 18°52'31.35"S, 39°8'41.34"W, 40 m, 15 Jul 2013; ZUEC-POL 21506 (ES), 20°1'3.73"S, 39°50'13.76"W, 53 m, 16 Dec 2010; ZUEC-POL 21507 (ES), 20°12'20.26"S, 39°57'59.7"W, 50 m, 20 Jan 2012; ZUEC-POL 21508 (ES), 19°31'51.66"S, 39°3'4.04"W, 150 m, 9 Dec 2011; ZUEC-POL 21509 (ES), 19°36'30.6"S, 39°10'19.39"W, 400 m, 26 Jun 2013; ZUEC-POL 21510 (ES), 21°12'14.60"S, 40°42'27.62"W, 15 m, 22 Jul 2009. Paratypes on stubs for SEM: ZUEC-POL 21522 (ES), 20°34'53.42"S, 40°6'27.43"W, 50 m, 21 Jan 2012; ZUEC-POL 21523 (ES), 20°6'44.162"S, 40°54'44.44"W, 30 m, 17 Jul 2009. Paratypes mounted on slides: ZUEC-POL 21524 (ES), 19°31'51.66"S, 39°3'4.04"W, 171 m, 9 Dec 2011; ZUEC-POL 21526 (ES), 22°8'9.28"S, 40°27'27.44"W, 103 m, 6 Mar 2009; ZUEC-POL 22898 (ES), 19°49'57.38"S, 39°52'14.02"W, 33 m, 15 Dec 2010; ZUEC-POL 22899 (ES), 20°11'25.75"S, 40°2'15.87"W, 40 m, 13 Jul 2013; ZUEC-POL 22902 (ES), 19°36'30.6"S, 39°10'19.39"W, 360 m, 26 Jun 2013; ZUEC-POL 22904 (ES), 19°49'57.38"S, 39°52'14.02"W, 33 m, 15 Dec 2010. Additional material preserved in alcohol 70 % (each lot with 1 specimen): ZUEC-POL 21511 (RJ), 21°40'25.12"S, 40°58'26.52"W, 18 m, 19 Jul 2009; ZUEC-POL 21512 (RJ), 21°33'54.61"S, 40°42'53.90"W, 23 m, 20 Jul 2009; ZUEC-POL 21513 (RJ), 21°11'0.91"S, 40°28'27.11"W, 26 m, 5 Mar 2009; ZUEC-POL 21514 (RJ), 22°6'22.01"S, 40°43'42.32"W, 47 m, 17 Jul 2009; ZUEC-POL 21515 (RJ), 22°6'20.06"S, 40°43'41.63"W, 47 m, 17 Jul 2009; ZUEC-POL 21516 (RJ), 21°55'50.85"S, 40°25'59.21"W, 47 m, 23 Jul 2009; ZUEC-POL 21517 (RJ), 22°6'41.46"S, 40°54'44.21"W. 52 m, 17 Jul 2009; ZUEC-POL 21518 (RJ), 22°45'49.07"S, 41°45'33.35"W, 53 m, 16 Jul 2009; ZUEC-POL 21519 (RJ), 22°8'9.28"S, 40°27'27.44"W, 65 m, 23 Feb 2009; ZUEC-POL 21520 (RJ), 22°12'37.0"S, 40°13'18.76"W, 100 m, 24 Feb 2009; MZUSP 4912 and MZUSP 4913 (ES), 20°34'45.78"S, 40°11'30.74"W, 41 m, 20 Jan 2012; MZUSP 4914 (ES), 18°52'32.61"S, 39°8'42.82"W, 40 m, 18 Jan 2012; MZUSP 4915, MZUSP 4916 and MZUSP 4917 (ES), 19°36'30.6"S, 39°10'19.39"W, 360 m, 26 Jun 2013; MZUSP 4918 (RJ), 21°59'3.657"S, 40°25'11.070"W, 52 m, 6 Jul 2009; MZUSP 4919 (RJ), 22°56'2.563"S, 41°53'51.338"W, 48 m, 28 Feb 2009; MZUSP 4920 (RJ), 22°6'42.185"S, 40°54'44.182"W, 29 m, 26 Feb 2009; MZUSP 4921 (RJ), 22°12'53.401"S, 40°51'12.488"W, 52 m, 26 Feb 2009; MZUSP 4922 (RJ), 22°17'42.207"S, 40°26'59.691"W, 104 m, 23 Feb 2009; MZUSP 4923 and MZUSP 4924 (RJ), 21°44'19.481"S, 40°17'15.642"W, 50 m, 9 Mar 2009; MZUSP 4925 (RJ), 21°44'19.481"S, 40°17'15.642"W, 49 m, 9 Mar 2009; MZUSP 4926 (RJ), 21°44'19.591"S, 40°17'15.669"W, 50 m, 8 Jul 2009; MZUSP 4927 (RJ), 22°37'31.715"S, 41°21'52.696"W, 54 m, 16 Jul 2009; MZUSP 4928 (RJ), 22°11'30.609"S, 40°5'24.468"W, 44 m, 17 Jul 2009; MZUSP 4929 (RJ), 21°10'16.281"S, 40°45'58.437"W, 21 m, 22 Jul 2009; MZUSP 4930 (RJ), 21°44'39.982"S, 40°43'8.573"W, 21 m, 19 Jul 2009; MZUSP 4931 (RJ), 21°39'31.643"S, 40°31'25.347"W, 28 m, 23 Jul 2009. Additional material mounted on slides: ZUEC-POL 21525 (RJ), 22°19'3.839"S, 40°5'28.581"W, 386 m, 30 Jan 2009; ZUEC-POL 21527 (RJ), 21°44'19.481"S, 40°17'15.642"W, 50 m, 9 Mar 2009; ZUEC-POL 21528 (RJ), 21°28'2.517"S, 40°56'20.614"W, 16 m, 10 Mar 2009; ZUEC-POL 22897 (RJ), 21°50'20.765"S, 40°31'38.459"W, 28 m, 13 Mar 2009; ZUEC-POL 22900 (RJ) 22°12'37.087"S, 40°13'18.731"W, 100 m, 24 Feb 2009; ZUEC-POL 22901 (RJ), 21°50'20.765"S, 40°31'38.459"W, 33 m, 7 Mar 2009; ZUEC-POL 22903 (RJ), 21°50'20.765"S, 40°31'38.459"W, 28 m, 13 Mar 2009; ZUEC-POL 22905 (RJ), 21°10'16."S, 40°45'58."W, 21 m, Nov 2020; ZUEC-POL 22906 (RJ), 21°44'19.481"S, 40°17'15.642"W, 50 m, Nov 2020; ZUEC-POL 21503 (RJ), 22°11'30.609"S, 40°5'24.468"W, 44 m, Nov 2020.

Type locality.

Southeastern Brazil, Espírito Santo state.

Distribution and habitat.

The distribution of this new species encompasses the states of Espírito Santo and Rio de Janeiro in southeastern Brazil, from the mouth of the Doce River to the continental slope (at depths between 14 and 400 m) in mud, sand, mixed sandy-mud bottoms, in sand with biological debris, and between limestones.

Remarks.

The nuchal organ was observed dorsally at the base of the prostomium in specimens analyzed under SEM (Fig. 4C ) but is difficult to visualize under the stereoscopic microscope due to the small size of the specimens.

The specimens are very small, and the jaw apparatus very delicate, especially the mandibles (Figs 7A, B, E, F , 8A-C ). There is no evidence of a chitinous ligament joining the pair of mandibles. In juveniles (Fig. 8A-C ), each mandible is composed of a distal denticulated plate and a chitinous longitudinal rod, which remains prominent in the adult (on its inner side) and from where the mandible expands laterally and grows, which is the pattern observed in many other species of Eunicida . The color of this lateral portion can vary from intense light brown (Fig. 7A, B ), colorless (Fig. 7D, E ) to almost transparent (Fig. 7F ), while the internal chitinous rod and anterior end remain always visible.

The notopodium, which is described as slightly developed in the description of the genus ( Carrera-Parra 2006), was not observed in the new species. The post-chaetal lobe, which is digitiform, relatively short, and projected backward, sometimes is not properly positioned for visualization under the stereoscopic microscope, or sometimes appearing to be absent in slide preparation (Fig. 8F, G ). Thus, care is required in positioning and placing of the coverslip to prevent some structures from being overlooked during observation under the microscope. However, the post-chaetal lobe is clearly digitiform in SEM images (Fig. 5C ). There is a fixed number of two limbate chaetae along the entire body.

Figures

Figure 1. Lumbrineriopsis dulcis sp. nov. A anterior end, dorsal view (ZUEC-POL 21515) B anterior end, ventral view (ZUEC-POL 21515) C mandibles (adult), dorsal view (ZUEC-POL 22897) D right mandible (juvenile), ventral view (ZUEC-POL 22900) E jaw apparatus, dorsal view (ZUEC-POL 21524) F MII, detailed view (ZUEC-POL 21524) G MIII, detailed view (ZUEC-POL 21524) H MIV detailed view (ZUEC-POL 21524). Arrows of C, D teeth of mandibles; arrows of G teeth of MIII. Scale bars: 125 µm (A, B); 31.25 µm (C); 25 µm (D); 31.25 µm (E-G); 12.5 µm (H).

Figure 2. Lumbrineriopsis dulcis sp. nov. (ZUEC-POL 21527) A parapodium 1 B parapodium 5 C parapodium 11 D parapodium 59 E parapodium 97 F parapodium 100. All parapodia in anterior view. Scale bars: 31.25 µm.

Figure 3. Lumbrineriopsis dulcis sp. nov. (ZUEC-POL 21527) A simple limbate chaetae B simple bidentate hooded hook C acicula D simple limbate chaetae E simple bidentate hooded hook F acicula G simple limbate chaetae H simple bidentate hooded hook I, J aciculae K simple limbate chaetae L simple bidentate hooded hook M, N aciculae A-C parapodium 1 D-F parapodium 5 G-J parapodium 11 K-N parapodium 59. Scale bars: 31.25 µm.

Figure 4. Lumbrineriopsis dulcis sp. nov. (SEM micrographs). (ZUEC-POL 21523) A, B anterior end, ventrolateral view C anterior end, dorsolateral view. m - mouth, pe - peristomium, pr - prostomium, sp - sensory pit. Scale bars: 200 µm (A); 100 µm (B, C).

Figure 5. Lumbrineriopsis dulcis sp. nov. (SEM micrographs). (ZUEC-POL 21522) A parapodia 1 and 2 B parapodia 30 - 35 C parapodium 33 D pygidium, posterior end, dorsal view (chaetae are broken, except one limbate). lc - limbate chaetae, pa - parapodium, pe - peristome, pi - pygidium, psl - post - chaetal lobe, sbhh - simple bidentate hooded hook. Scale bars: 50 µm (A, B); 10 µm (C); 50 µm (D).

Figure 6. Lumbrineriopsis dulcis sp. nov. (SEM micrographs). (ZUEC-POL 21522) A parapodium 1, anterior view B parapodia 9 and 10, anterior view C parapodium 12, anterior view D parapodia 29 and 32 E parapodium 30, anterior end F parapodium 65, anterior view. lc - limbate chaetae, psl - post - chaetal lobe, sbhh - simple, bidentate, hooded hook. Scale bars: 10 µm.

Figure 7. Lumbrineriopsis dulcis sp. nov. Mandibles (adult) A ZUEC-POL 22897 B ZUEC-POL 21526 C ZUEC-POL 22898 D ZUEC-POL 21524 jaw apparatus (adult) E ZUEC-POL 21525 F ZUEC-POL 22899 G ZUEC-POL 22905 anterior end, ventral view, partially everted pharynx. al - attachment lamella, ph - pharynx, MI - maxillae I, MII - maxillae II, MIII - maxillae III, MIV - maxillae IV, md - mandible, pr - prostomium. Scale bars: 45 µm (A); 40 µm (B, D); 50 µm (C); 48 µm (E); 52 µm (F); 200 µm (G).

Figure 8. Lumbrineriopsis dulcis sp. nov. A jaw apparatus (juvenile), ZUEC-POL 22900 B mandible (juvenile), ZUEC-POL 22900 C jaw apparatus (juvenile), ZUEC-POL 22901 D parapodium 7, ZUEC-POL 22527 E parapodium 8, ZUEC-POL 22527 F parapodium 96, ZUEC-POL 22528 G parapodium 97, ZUEC-POL 22528. psl - post-chaetal lobe. Scale bars: 25 µm (A-C, F, G); 15 µm (D, E).