Travisia amoyanus, Yang & Wu & Wang & Zhao & Hwang & Cai, 2022

Yang, Deyuan, Wu, Xuwen, Wang, Zhi, Zhao, Xiaoyu, Hwang, Jiangshiou & Cai, Lizhe, 2022, Redescription of a rarely encountered species Travisa chinensis Grube, 1869 (Annelida, Travisiidae), including a description of a new species of Travisa from Amoy, China, ZooKeys 1128, pp. 1-17 : 1

Travisia amoyanus sp. nov.

Figs 4A-O , 5A-H

Travisia chinensis Monro, 1934: 374, fig. 8.

Material examined.

Holotype. Complete MBM287243: Xiamen, China, 24°27.14'N, 118°11.19'E, 24 July 2021, ethanol . Paratypes. One complete (MBM193597), two complete (MBM286089), Xiamen , China, 24°35.04'N, 118°10.09'E, 19 April 1963, formalin. Five complete (MBM286088), Xiamen , China, 24°26.30'N, 118°10.11'E, 2014-2016, formalin. Four complete (MBM286075), Xiamen, China, 24°30.49'N, 118°16.30'E, 2014-2016, formalin. One complete (MBM287244), one complete (MBM287245), one complete (MBM287248), one complete (MBM287249), one complete (MBM287250), same data as the holotype, ethanol one complete (MBM287246), one complete (MBM287247), same data as the holotype, formalin .

Diagnosis.

Prostomium pointed, conical. Body with 34 or 35 segments and 33 or 34 chaetigers. Branchiae cirriform from chaetiger 2 to chaetiger 28-32. Larger triangular lateral parapodia lobes or lappets well developed from chaetiger 15. Pygidium with a larger ventral triangular cirrus and about six lateral cirri around.

Description.

Preserved specimens white to grey, and living specimens reddish (Fig. 4D, F, G ). Body length 18.0-45.0 mm (holotype, 30.0 mm) and 2.0-5.6 (holotype, 3.0 mm) width at widest segment. Prostomium conical, distally pointed. Eyes and prostomial processes absent (Fig. 4A-C, H-N ). Peristomium with a pair of nuchal organs (Fig. 4A, H, L ). Mouth opening between chaetiger 1 and 2 (Fig. 4C, D, M ). Body surface with fine papillae except the distal part of prostomium and branchiae (Fig. 4A-E, G-M ).

Branchiae simple, cirriform with 27-31 pairs (holotype: 31 pairs on the left side, 30 pairs on the right side), from chaetigers 2 to chaetigers 28-32. In preserved specimens, branchiae length nearly uniform except for chaetiger 2 and about the last 10 chaetigers.

Body with 34 or 35 segments and corresponding 33 or 34 chaetigers. All chaetae capillary, with a narrow wing (limbate) at one side (Fig. 5 F ).

Parapodia biramous, without pre- and postchaetal lobes, notopodial and neuropodial chaetal rami well separated except the posterior end. Interramal pores or lateral sense organs between notopodial and neuropiodial chaetal rami from chaetiger 1 to every succeeding segment, except that occasionally hidden or absent on segment 34 or 35.

Prominent parapodia lateral lappets from chaetiger 15, well developed. Notopodial lobes (lappets) above the bundle of notochaetae. Neuropodial lobes below neurochaetae but missing on last one or two chaetigers. Notopodial and neuropodial lobes triangular except toward the anus, where they become longer and more cylindrical.

Nephridial pores present on chaetigers 3-14, anterior and posterior pores smaller than middle ones. First chaetiger biannulate, chaetigers 2-19 triannulate ventrally and dorsally, chaetigers 20-27 biannulate, 28-34 (35) segments uniannulate. Posterior margin of the last seven or eight segments with more or less obvious crenulations dorsally. Midventral groove absent, if have, present from last four segments (Fig. 4D ).

Pygidium as long as about last three segments with a larger triangular mid-ventral process and six lobes. Inner anus with many cirriform papillae.

MG staining pattern.

The body surface of specimens has a distinctive staining pattern: the posterior part of the first and the third ring of chaetigers 2-14 show significant staining; from chaetigers 15 to the posterior end the body is deeply stained (Fig. 5 ).

Variations.

Morphological comparison of 23 specimens is provided (Suppl. material 1: table S5). Maximum length ranged from 1.8 to 4.5 mm. Branchiae distribution is frequently asymmetrical on both sides of the body, most specimens have a narrow range (N = ± 1), except MBM286089-spec.3 (28 pairs on left, 31 pairs on right).

The maximum number of branchiae ranged from 27-31 pairs among individuals (Fig. 6 ). Eighteen specimens had 34 segments, and five specimens had 35 segments. Fourteen specimens had 34 chaetigers, and nine specimens had 33 chaetigers.

Body subfusiform in preserved specimens, swollen medially (Fig. 5D, E ), while in living specimens, the segments are nearly equal between the prostomium and the anus, usually swollen at the anterior part of the body because of the worm’s peristalsis (Fig. 5A-C, H-N ).

Type locality.

Coastal waters of Xiamen, China.

Etymology.

The specific epithet, amoyanus, refers to the type locality of Amoy, the pronunciation of local dialect of Xiamen, a coastal city in Fujian Province, China.

Biology.

Travisia amoyanus inhabits sandy sediments from the intertidal to the subtidal (1-2 m depth). It can be strongly malodorous, and the body surface is covered by a viscous mucus tube with sand grains adhering (Fig. 5F ).

Remarks.

Travisia amoyanus sp. nov. clearly differs from T. chinensis in the total number of segments and chaetigers, the beginning of parapodial lappets, and the shape of pygidium. In T. amoyanus (34 or 35 segments, 33 or 34 chaetigers), parapodial lappets start from chaetiger 15 and the pygidium with a large triangular mid-ventral process, whereas in T. chinensis (30 segments, 29 chaetigers), neuropodial lappets start from chaetiger 16 and notopodial lappets from chaetiger 19 and the pygidium bears no large triangular mid-ventral lobe.

Travisia amoyanus sp. nov. resembles several species in having a similar number of segments and chaetigers (35-36), such as T. concinna (Kinberg, 1866) (35 segments and chaetigers) from South Africa, T. arborifera (36 chaetigers) from Indian Ocean, and T. filamentosa (35-36 segments, 35 chaetigers) from California. However, T. amoyanus sp. nov. can be distinguished from T. arborifera and T. filamentosa by having cirriform branchiae, the latter two species have branched branchiae. Travisia amoyanus sp. nov. differs still from T. concinna in having 31 (vs 33) pairs of branchiae, and parapodial lappets starting from chaetiger 15 (vs 17 or 18). In addition, T. amoyanus sp. nov. has 31 pairs of branchiae and parapodial lappets from chaetigers 15, while T. fusiformis Kudenov, 1975 has 34 pairs of branchiae, notopodial lappets from chaetigers 2 and neuropodial lappets from chaetiger 17.

Travisia amoyanus sp. nov. is much closer to T. japonica Fujiwara, 1933 from Japan and T. gigas Hartman, 1938 from California in the starting segments of parapodial lappets. But, the new species and T. gigas can be distinguished in the following aspects: (1) 34 or 35 segments and 33 or 34 chaetigers in T. amoyanus , 46 segments and 46 chaetigers in T. gigas ; (2) 31 pairs of branchiae in T. amoyanus , 44 pairs in T. gigas ; (3) pygidium with a large triangular mid-ventral process and six cylindrical lobes in T. amoyanus , without triangular mid-ventral process in T. gigas .

Travisia japonica is considered to have a wide-ranging body segment count (32-43 segments), and the species has been recorded from a wide range of geographic regions ( Dauvin and Bellan 1994). However, Fujiwara (1933) stated explicitly that T. japonica has a relatively fixed number of segments (39, seldom 40) based on examination of a considerable number of specimens. Therefore, in this comparison, we used the original description data and suggest that records of T. japonica from non-Japanese areas need to be re-evaluated and might represent potentially undescribed species.

Travisia amoyanus sp. nov. is distinguishable from T. japonica by the following characters: the number of segments (34 or 35 in T. amoyanus vs 39 or 40 in T. japonica ), the number of chaetigers (33 or 34 in T. amoyanus vs 39 or 40 in T. japonica ), the number of branchiae (27-31 pairs in T. amoyanus vs 25 pairs in T. japonica ), the distribution of interramal pores (1-33 or 34 chaetigers in T. amoyanus vs 1-29 chaetigers in T. japonica ), the number of nephridial pores (12 pairs in T. amoyanus vs 11 pairs in T. japonica ). In fact, the difference between these two species also had been noticed by Monro (1934: p374): " T. japonica Fujiwara is close to T. chinensis (regarded herein as T. amoyanus ), but has 39 to 40 chaetigers".

Distribution.

Currently only found from Xiamen coastal waters.

Figures

Figure 4. Travisia amoyanus sp. nov. A-F holotype (MBM 287243) H-O paratypes (H MBM 193597; I-K MBM 287249; L MBM 287248; M-O MBM 287244) A-C living specimen in dorsal, lateral, and ventral view, respectively D fixed specimen in ventral view E same, in dorsal view F detail of capillary chaeta G tube H fixed specimen in lateral view I-K alive, in dorsal, lateral, and ventral views, respectively L alive, in lateral view M-O alive, dorsal, lateral, and ventral views, respectively. Abbreviations: pr, prostomium; per, peristomium; nuO, nuchal organ; mo, mouth; br, branchiae; chaet, chaetiger; IntP, interramal papilla; Pl, parapodia lateral lappet; np, nephridial pores; ntc, notochaetae; npc, neurochaetae; Py, pygidium; ac, anal cirri; Vc, Pygidial ventralmost cirrus.

Figure 5. Travisia amoyanus sp. nov., stained with methyl green. Paratypes (A, B MBM 286089 - spec. 1; C-F MBM 286089 - spec. 2) and non-type specimen (G, H MBM 286088 - Spec. 1) A, C, G whole body in dorsal view B, E, H whole body in ventral view D posterior end in dorsal view F posterior region in ventral view Abbreviations: Vc, Pygidial ventralmost cirrus.

Figure 6. Scatter diagram illustrating variability of five key characters with the body length. Abbreviations: Toc, total number of chaetigers; Tos, total number of segments; Mob, Maximum of branchiae; Sopl, start of parapodial lappets on chaetiger; Sob, start of branchiae.