Travisia hernandezalcantarai sp. nov.

Zoobank: urn:lsid:zoobank.org:act: 42EA1216-FE10-4C05-9541-E14E38DC390E

(Figs 6‒10)

Type Material. Holotype, ICML-EMU-14079, TALUD XII. Sta. 29, 02 April 2008, 19º19’37”N, 105º26’20”W, off Jalisco, Mexico,BS, 1609‒1643m. Paratypes,ICML-EMU-14080-A, TALUD XI. Sta. 26, 10June2007, 18º33’12”N, 104º32’12”W, off Colima, Mexico, BC, 1918 m, 1 specimen. ICML-EMU-14080-B, TALUD XI. Sta. 27, 11 June 2007, 18º41’00”N, 104º33’07”W, off Colima, Mexico, BC, 1305 m, 1 specimen. ICML-EMU-14080-C, TALUD XI. Sta. 28, 11 June 2007, 18º48’05”N, 104º32’36”W, off Colima, Mexico, BC, 1050 m, 1 specimen. UAA, TALUD XII. Sta. 5, 28 March 2008, 16º58’28”N, 100º55’20”W, off Guerrero, Mexico, BC, 1849 m, 1 specimen mounted in gold for SEM. ICML-EMU-14082-A, TALUD XII. Sta. 10, 28 March 2008, 17º11’03”N, 101º28’05”W, off Guerrero, Mexico, BC, 1290 m, 1 specimen. ICML-EMU-14082-B, TALUD XII. Sta. 14, 30 March 2008, 17º36’20”N, 102º01’59”W, off Guerrero, Mexico, BC, 1245 m, 1 specimen. ICML-EMU-14083-A, TALUD XII. Sta. 20, 31 March 2008, 17º54’20”N, 103º10’45”W, off Guerrero, Mexico, BC, 1992 m, 1 specimen. ICML-EMU-14083-B, TALUD XII. Sta. 27, 02 April 2008, 18º40’28”N, 104º35’51”W, off Colima, Mexico, BC, 1158 m, 1 specimen. UANL-8282, TALUD XII. Sta. 28, 02 April 2008, 18º50’19”N, 104º34’14”W, off Colima, Mexico, BC, 1080 m, 1 specimen.

Diagnosis. Travisia with annulate branchiae from chaetiger 2, 22‒25 pairs of branchiae and 26‒28 chaetigers. Mid-ventral groove present. Nuchal organs remarkably large. Parapodial lappets absent.

Description. Holotype 32 mm long (20‒39 mm long in paratypes), 8 mm width (7‒9 mm wide in paratypes) with 26 chaetigers (27‒28 chaetigers in paratypes). Body yellowish to cream-colored in alcohol; robust, grub-like (Fig. 8A‒B) with rugose epidermis and remarkable, transverse rows of spherical papillae (Fig. 6A‒B). Prostomium small, conical, pointed, smooth (Figs 6A, C‒D, F, 8A‒D, 9A‒B). Nuchal organs dorsolateral, teardrop-shaped splits, remarkably large (Figs 6A, C‒D, F, 8C, 9B). Eyes absent. Mouth ventral between chaetigers 1 and 2, upper lip with short elongate annulations of chaetiger 1, lower lip with short annulation of chaetiger 2 (Fig. 8A‒D). Pharynx not everted in all specimens.

Peristomium uniannulated. Chaetiger 1 biannulated (Figs 8C‒D, 9A‒B). Chaetigers 2 to 13‒14 triannulated (Figs 8A‒B, D, 9A). Chaetigers 15‒17 biannulated (Fig. 8A‒B). Chaetigers 18 to the end uniannulated (Fig. 8A‒B).

Peristomium covered with spherical papillae (Fig. 8C); dorsal side with distal part squared (lateral and distal sides forming right angles), narrower than prostomium width (Fig. 6C‒D, F). Basal part with rounded lateral margins, three times broader than distal part (Fig. 6C‒D, F). First, second and third chaetigers with lateral sides covered by sub-triangular packages of equal-sized spherical papillae (Figs 6A, C‒D, F, 8C, 9A‒B), dorsal side with posterior margin of packages festooned (Fig 6A, C‒D, F). From chaetiger 2 towards posterior end, each segment with rows of spherical papillae around body as follows: A, anterior chaetigers (chaetigers 2‒13) with three rows of spherical papillae (Figs 7E, 8A); B, median chaetigers (chaetigers 14 to 17) with two rows of spherical papillae: median row with large papillae, external row with small papillae (Fig. 7F). C, Posterior chaetigers (from chaetiger 18 to the end) without rows of papillae, all integument covered in full by iminute papillae (Fig. 9F), increasing gradually in size from the anterior margin of each segment to posterior margin (Fig. 7A, I). Posterior margin of each segment flap-like (festooned), with ventral sides longer than dorsal sides (Fig. 7I). Papillae located basally in lateral borders of each segment twice as long as internal papillae, spherical to oval-shaped (Figs 7I, 9A, D‒E). In last 10 segments, lateral-most papillae from within basal margin spherical, +3 times the size of internal papillae (Fig. 7J).

Interamal sensory pores C-shaped, large (almost as wide as branchial basis) (Fig. 9E), located between notochaetae and neurochaetae from chaetiger 1 until near last segments. Lateral neuropodial nephridiopores not seen under light or SEM microscopy.

Branchiae annulate (Figs 9C‒E, 10C, E), 24 pairs in holotype (22‒25 pairs in paratypes) starting at chaetiger 2 (Fig. 9A‒B) and extending to chaetiger 25 (chaetiger 22 in six paratypes, chaetiger 24 in one paratype). First pair short, increasing gradually in size towards chaetiger 10 (Figs 7G‒J, 8B), decreasing in size gradually to posterior end (Figs 7J, 8B).

Parapodia biramous (Figs 9D‒E, 10C, E). All noto- and neurochaetae translucent, spinulose capillaries (Figs 9E, 10D, F). Last 2‒4 segments achaetous (Fig. 9F). Noto- and neuropodial lappets absent (Figs 7G‒H, 9D, F). A shallow, mid-ventral groove present only on last 10‒12 abdominal segments (Fig. 6E).

Pygidium short, terminal (not shifted to side), thick; anus ventral with 12 lobes in a circle, without anal cirri (Figs 6E, 7A‒D, 8A‒B, 9F).

Etymology. The species is named after Dr. Pablo Hernández-Alcántara, a Mexican polychaete systematist and ecologist, and a long-time friend and colleague. The species is named in recognition of his contribution to the study on spatial and bathymetric trends of polychaetes in Western Mexico. The species-group name is a noun in the genitive case (ICZN, 1999, Art. 31.1.2).

Remarks. Travisia hernandezalcantarai sp. nov., is unique among the species currently recognized in the genus by having nuchal organs remarkably large, as long as the tip of the prostomium.

Travisia hernandezalcantarai sp. nov., and T. pupa can be distinguished based on the following features: 1, Travisia hernandezalcantarai sp. nov., does not have parapodial lappets whereas they are present in T. pupa; 2, nuchal organs large, teardrop-shaped in T. hernandezalcantarai sp. nov., versus discrete, narrow splits in T. pupa; 3, peristomium with an inverted T-shaped area dorsally in T. hernandezalcantarai sp. nov., versus a triangular-shaped area in T. pupa; 4, lateralmost papillae on the posterior margin of each terminal segment being up to 3 times larger than internal papillae in T. hernandezalcantarai sp. nov., versus all papillae from the posterior margins less than 2 times larger than internal papillae in T. pupa; and 5, a mid-ventral groove restricted to posterior segments of the body in T. hernandezalcantarai sp. nov., whereas it is present along the entire body in T. pupa.

Based on the presence of a ventral groove and as stated in the remarks section for T. pupa, T. hernandezalcantarai sp. nov., and T. pupa should be added to the group B1 proposed by Plathong et al. (2023). Group B1 is composed by T. fusiformis Kudenov, 1975 (intertidal, from the Gulf of California, Mexico), T. hobsonae Santos, 1977 (10‒110 m depth, Tampa Bay, Florida, USA), T. thailandensis Plathong, Plathong & Salazar-Vallejo, 2023 (50‒80 m, Gulf of Thailand), T. pupa and T. hernandezalcantarai sp. nov., Travisia hobsonae is characterized by having branchiae starting at chaetiger 3 and prostomium with pustules (Santos 1977), whereas in T. fusiformis, T. thailandensis, T. pupa and T. hernandezalcantarai sp. nov., branchiae appear in chaetiger 2 and the prostomium lacks pustules. In T. fusiformis, T. thailandensis and T. pupa the mid-ventral groove is present along body whereas the mid-ventral groove extents only to posterior segments in T. hernandezalcantarai sp. nov., Travisia fusiformis has 34‒35 chaetigers, T. thailandensis 26‒28 chaetigers and T. hernandezalcantarai sp. nov., 26‒28 chaetigers. Travisia fusiformis, T. thailandensis, and T. pupa have parapodial lappets. In T. fusiformis, neuropodial lappets are small, conspicuous and well-developed from chaetiger 17 to the end of the body; in T. thailandensis, parapodial lappets from the anterior region are small and neuropodial lappets become progressively larger in posterior region; in T. pupa, lappets are well-developed in three quarters of the body segments (anterior); T. hernandezalcantarai sp. nov., lacks lappets altogether.

Abiotic conditions. The specimens of Travisia hernandezalcantarai sp. nov., were collected in sediments from 1050–1992 m deep, under the following environmental conditions: temperature, 2.3–5.2°C; salinity, 34.53–34.63; dissolved oxygen, 0.03–1.49 ml O 2 /l; %CO, 0.91–4.64; sediments composition variable, including mixed, sandy mud, muddy sand, and mud (Table 1).