Pseudonereis brunnea, Conde-Vela, 2018

Conde-Vela, Víctor M., 2018, New species of Pseudonereis Kinberg, 1865 (Polychaeta: Nereididae) from the Atlantic Ocean, and a review of paragnath morphology and methodology, Zootaxa 4471 (2), pp. 245-278 : 254-257

Pseudonereis brunnea sp. n.

Figures 5A, D ; 6

Pseudonereis gallapagensis de León-González 1997: 236 , Figs. 141a–e (non Kinberg, 1865).

Type material. Gulf of Mexico, Mexico. Holotype ECOSUR 0 191, La Mancha, Veracruz (19°36'0.30"N 96°22'19.61"W), 27 May 2004, 1– 2 m depth, Coll. MA Hernández-Álvarez. Paratypes ECOSUR 0 192 (6), La Mancha, Veracruz (19°35'10.16"N 96°22'38.88"W), 3 July 2003, 1– 2 m depth, Coll. MA Hernández-Álvarez. ECOSUR 0 193 (3), La Mancha, Veracruz, 23 July 2003, 1– 2 m depth, Coll. MA Hernández-Álvarez.

Additional material. Gulf of Mexico, Mexico. ECOSUR P2926 (12), La Mancha, Veracruz (19°35'7.49"N 96°22'38.74"W), 23 July 2003, 1– 2 m depth, Coll. MA Hernández-Álvarez. ECOSUR P2927 (10), La Mancha, Veracruz (19°35'13.64"N 96°22'39.24"W), 23 September 2004, 1– 2 m depth, Coll. MA Hernández-Álvarez. ECOSUR P2928 (10), La Mancha, Veracruz (19°35'10.16"N 96°22'38.88"W), 27 April 2004, 1– 2 m depth, Coll. MA Hernández-Álvarez. ECOSUR P2929 (1), La Mancha, Veracruz (19°35'7.49"N 96°22'38.74"W), 27 May 2004, 1– 2 m depth, Coll. MA Hernández-Álvarez. ECOSUR P2930 (1), La Mancha, Veracruz (19°36'4.91"N 96°22'18.09"W), 28 September 2003, 1– 2 m depth, Coll. MA Hernández-Álvarez. ECOSUR P2931 (6), Montepío, Veracruz (18°38'46.97"N 95°5'44.19" W), basaltic rocky shore, 1 April 2004, 1– 2 m depth, Coll. MA Hernández- Álvarez. USNM 174868 (68), Boca del Río, Veracruz, 10 September 1996, Coll. ML Jones.

Type locality. La Mancha Lagoon, Veracruz, Mexico (19°36'0.30"N 96°22'19.61"W), Gulf of Mexico.

Etymology. The specific name stems from the Latin adjective brunneus, - a, - um, meaning brown, referring to the even brown pigmentation present in this species.

Description. Holotype (ECOSUR 0191) complete, 24 mm long, 2.1 mm wide, 72 chaetigers; two paratypes (ECOSUR 0192) complete, larger one 23 mm long, 2 mm wide at chaetiger 10, 70 chaetigers, smaller one 22 mm long, 1.8 mm wide at chaetiger 10, 72 chaetigers, both used for showing pharynx and chaetae.

Body tapered, pigmented. Dark brown pigment in anterior end, more intense on prostomium and achaetous ring, discoloring posteriorly; pigment brown uniform in prostomium, with two narrow, pale lines behind each antenna, a central triangular spot arising from posterior margin of prostomium, becoming wider toward posterior end of prostomium, surrounding eyes and with a medial pale line between them; palps light brown, paler toward inner margins of palpophores, yellowish spots on palpostyles ( Fig. 6A, H ).

Prostomium longer than wide; antennae digitiform, half as long as prostomium, slightly surpassing palps; eyes subequal, black, lenticulated, in trapezoidal arrangement, anterior pair semilunar, posterior pair rounded ( Fig. 6A, H ). Achaetous ring twice as long as first chaetiger; four pairs of anterior cirri, cirrophores conspicuous, longest cirri reaching chaetiger 4 ( Fig. 6A ).

Pharynx dissected in holotype, partially everted in paratypes; jaws brown, thick, 11 teeth, cutting edge completely dentate. Maxillary ring: I= 2 cones in vertical line; II= 3-3 comb-like rows in triangle; III= 4 comb-like rows in triangle; IV= 5-5 comb-like rows and additional cones, merged cones and P-bars, in sigmoid ( Fig. 6I ). Oral ring: V= 1 cone; VI= 1-1 shield-shaped bars with pointed and blunt tips ( Fig. 5A ); VII–VIII= one furrow row with 11 P-bars ( Fig. 5D ) and one ridge row with 9 cones in a single band, rows vertically displaced; furrow and ridge regions with one paragnaths each ( Fig. 6J ).

Parapodial cirri pattern. Dorsal cirri longer than notopodial dorsal ligules in anterior region, becoming shorter toward posterior end; basally inserted to notopodial dorsal ligules in most anterior segments, displaced medially in medial segments, subdistal in posterior segments, and distal in posterior-most ones. Ventral cirri subequal and basally inserted to neuropodial ventral ligules throughout body.

First two chaetigers with neuroaciculae only, remaining ones with both noto- and neuroaciculae. In first two chaetigers ( Fig. 6C ), dorsal cirrus basal, 1.5 times longer than dorsal ligule. Dorsal ligule subconical, blunt, slightly longer than neuroacicular ligule. Neuroacicular ligule subconical, blunt, as long as neuropodial ventral ligule; postchaetal lobe rounded, as long as neuroacicular ligule; neuropodial ventral ligule digitiform. Ventral cirrus basal, as long as neuropodial ventral ligule.

In anterior and middle chaetigers ( Fig. 6D–E ), dorsal cirrus medial, 1.5 times longer than notopodial dorsal ligule. Notopodial dorsal ligule subconical, blunt, as long as notopodial ventral ligule; notopodial ventral ligule rounded to digitiform, as long as neuroacicular ligule. Neuroacicular ligule subconical, twice as long as neuropodial ventral ligule, distally bilobed, superior lobe much smaller than inferior one; postchaetal lobe rounded, as long as neuroacicular ligule; neuropodial ventral ligule digitiform. Ventral cirrus basal, as long as neuropodial ventral ligules.

In posterior chaetigers ( Fig. 6F ), dorsal cirrus subdistal, as long as notopodial dorsal ligule. Notopodial dorsal ligule pennant-like, twice as long as notopodial ventral ligule; notopodial ventral ligule digitiform, twice as long as neuroacicular ligule. Neuroacicular ligule subconical, slightly longer than neuropodial ventral ligule, distally bilobed, both superior and inferior lobes subequal, sometimes inconspicuous; postchaetal lobe rounded, as long as neuroacicular one; neuropodial ventral ligule digitiform. Ventral cirrus basal, as long as neuropodial ventral ligule.

In posterior-most chaetigers ( Fig. 6G ), dorsal cirrus distal. Notopodial dorsal ligule foliose, pennant-like, 1.6 times longer than wide, 2.5 times longer than dorsal cirrus, 3–4 times longer than notopodial ventral ligule; notopodial ventral ligule digitiform, twice as long as neuroacicular ligule. Neuroacicular ligule subconical, blunt, slightly longer than neuropodial ventral ligule; postchaetal lobe rounded, as long as neuroacicular one; neuropodial ventral ligule digitiform. Ventral cirrus basal, slightly shorter than neuropodial ventral ligule.

Notochaetae homogomph spinigers. Neurochaetae homogomph spinigers and heterogomph falcigers in supraacicular fascicles, heterogomph spinigers and falcigers in sub-acicular fascicles.

Notopodial homogomph spinigers pectinate, teeth narrow, decreasing in size toward distal end ( Fig. 6N ). Neuropodial homogomph spinigers as notopodial ones; neuropodial heterogomph spinigers pectinate, basal teeth coarse, decreasing in size toward distal end ( Fig. 6M, O ). Neuropodial heterogomph falcigers falcate, pectinate, teeth narrow present basally, half to two thirds of inner edge edentate, distal tip stout, blades and articulation region of shaft dark brown ( Fig. 6K–L ); supra-acicular falcigers stouter than sub-acicular ones ( Fig. 6K – L ).

Pygidium crenulated; anal cirri cirriform, as long as last six segments ( Fig. 6B ).

Variation. The results of the analysis of body variation and paragnaths number are summarized in Tables 1 and 2. W3 had the highest coefficient of correlation with TL, followed by W10, L3, and L10; notably, nCh had no correlation with TL. RTC had low correlation with TL. Variation in paragnath number was very low, varying in one or two paragnaths in the areas I, V and VII–VIII. The number of paragnaths in the areas V, VI and VII–VII is similar to found in other Pseudonereis species ( Bakken 2007, Table 1).

TABLE 1. Descriptive statistics of some body measures in three Pseudonereis species. Only complete specimens were considered for analysis. Abbreviations: TL= total length; L3 and L10= length at chaetiger 3 and 10, respectively; W3 and W10= width at chaetiger 3 and 10, respectively; nCh= number of chaetigers; RTC= reach of largest anterior cirrus).

Remarks. P. brunnea sp. n. resembles P. gallapagensis , but some differences can be noted. In P. brunnea sp. n., the anterior eyes are semilunar, whereas in P. gallapagensis they are rounded. Furthermore, in. P. brunnea sp. n., dorsal cirri are 1.5 times longer than notopodial dorsal ligules in anterior and middle chaetigers, whereas in P. gallapagensis they are 1.0–1.2 times longer. In P. brunnea sp. n., neuroacicular ligules are distally bilobate in anterior-most chaetigers only and sometimes inconspicuous, whereas in P. gallapagensis they are distally bilobate throughout body and lobes become inconspicuous in posterior-most chaetigers. Moreover, in P. brunnea sp. n., notopodial dorsal ligules are 3–4 times longer than notopodial ventral ones, whereas in P. gallapagensis they are 7– 8 times longer.

P. brunnea sp. n. also resembles P. deleoni Villalobos-Guerrero & Tovar-Hernández, 2013 , but they differ in some relevant features. In P. brunnea sp. n., the anterior pair of eyes are semilunar, whereas in P. deleoni they are rounded. Moreover, P. brunnea sp. n. has even brown pigment in anterior body and fading out toward posterior end, whereas P. deleoni has brown spots forming three rows in anterior segments, and only the central row remains in posterior chaetigers ( Villalobos-Guerrero & Tovar-Hernández 2013, Fig. 2A ). Furthermore, in P. brunnea sp. n., inferior and superior lobes of the neuroacicular lobes are conspicuous in anterior chaetigers only, whereas in P. deleoni they are conspicuous throughout body.

Differences between P. brunnea sp. n. and P. citrina sp. n. are more obvious due to the absence of dark brown pigment, anterior pairs of eyes rounded, dorsal cirri 2–3 times longer than notopodial dorsal ligules, and translucent notopodial dorsal ligules in posterior chaetigers in the latter species. Specimens identified as P. gallapagensis by de León-González (1997) from Veracruz and Tamaulipas, Gulf of Mexico, match with the current definition. The description of P. gallapagensis by Dueñas-Ramírez & Quiros-Rodríguez (2012) from Córdoba, Colombian Caribbean, resembles P. brunnea sp. n., but it requires further examination of specimens to determine if they are conspecific. Record of P. gallapagensis by Rioja (1960: 297) from Veracruz likely belongs to P. brunnea sp. n., but the greenish pigmentation described for the specimens and the short description lacking illustrations prevent its reliable inclusion into P. brunnea sp. n. Record of P. gallapagensis by Fauchald (1977a: 32–33) from Caribbean Panama likely belong to P. brunnea sp. n., but re-examination of the specimens is needed to ensure the identification. Additional records of P. gallapagensis ( Hartman 1944; Ibárzabal 1986; de León-González et al. 1999) lack descriptions to ensure its belonging to P. brunnea sp. n. or another species.

Distribution. Gulf of Mexico.

Figures

FIGURE 2. The midventral pharynx area in some nereidid genera. A, midventral area in Alitta succinea (ECOSUR P2729). B, midventral area in Pseudonereis gallapagensis (USNM 24266). C, midventral area in Nereis garwoodi (ECOSUR P2831). D, midventral area in Perinereis floridana (ECOSUR P1100). E, midventral area in Hediste cf. diversicolor (USNM 58131). F, midventral area in Kainonereis polaris (USNM 55514). G, midventral area in Platynereis magalhaensis (ECOSUR P2935). A– B and E–F show pharynges fully everted; C–D show pharynges partially everted; G shows a pharynx dorsally dissected. The midventral area in all drawings is highlighted in white.

FIGURE 5. Classification of some rectangular-base paragnaths. A, shield-shaped bars. B, crescent-shaped bars. C and D, pointed bars (P-bars). Drawings show the tip (dark brown) and base (light brown) of paragnaths, in both anterior and superior views; each drawing is accompanied with a picture of the same paragnath and at the same view. Green arrowheads point toward the anterior end of the body, showing the relative position of the paragnaths in relation to the pharynx axis. Blue vertical triangles point to the distal tip of the paragnaths; red triangles point the midpoint of the bases, and white dotted lines represent the bases’ altitude lines. A, D, Pseudonereis brunnea sp. n. (ECOSUR P2926); B, Perinereis floridana (ECOSUR P1100); C, Nereis garwoodi (ECOSUR P2831).

FIGURE 6. Pseudonereis brunnea sp. n. Holotype A–H (ECOSUR 0191); paratypes I–O (ECOSUR 0192). A, anterior end, dorsal view. B, posterior end, dorsal view. C, chaetiger 2, right parapodium. D, chaetiger 10, right parapodium. E, Chaetiger 26, right parapodium. F, chaetiger 46, right parapodium. G, chaetiger 65, right parapodium. H, close up of anterior end. I, maxillary ring, frontal view. J, oral ring, frontal view. K, supra-acicular heterogomph falciger, chaetiger 55. L, sub-acicular heterogomph falciger, chaetiger 55. M, sub-acicular heterogomph spiniger, chaetiger 55. N, notopodial homogomph spiniger, chaetiger 55. O, sub-acicular heterogomph spiniger, chaetiger 55. Black triangles= points used for length measurement. Scale bars: A, B, 1 mm; C–G, 0.2 mm; H–J, 0.5 mm; K–M, 10 µm; N, O, 30 µm.