Westheidesyllis San Martín, López & Aguado, 2009

Rodolfo Leandro Nascimento, Marcelo Veronesi Fukuda & Paulo Cesar de Paiva, 2024, Two new incertae sedis syllids (Annelida: Syllidae) from Brazilian oceanic islands, European Journal of Taxonomy 925 (1), pp. 46-66 : 53-54

Genus Westheidesyllis San Martín, López & Aguado, 2009

Type species

Eusyllis heterocirrata Hartmann-Schröder, 1959 , designated by San Martín et al. (2009).

Emended diagnosis

Small-sized, fragile bodies, easily loosing antennae and cirri. Transversal bands of cilia may be present on prostomium, peristomium and segments. Palps subtriangular, free from each other for most of their length, fused only at bases; prostomium oval to subpentagonal, with lateral antennae inserted near anterior rim, median antenna inserted posteriorly to lateral ones; eyes present or absent, sometimes only a pair; some species with pair of anterior eyespots. Peristomium distinct, with two pairs of peristomial cirri. Dorsal cirri alternating long cirri, more than twice as long as body width at corresponding segment, and short cirri, with length up to half width of corresponding segment. Parapodial glands occasionally present at the bases of parapodial lobes. Falcigers with homogomph articulation; blades short, bidentate, spinulated, with short spines. Dorsal simple chaetae from anterior to midbody posteriorwards. Ventral simple chaetae not known. Aciculae distally inflated, laterally expanded or knobbed. Pharynx longer or about same size as proventricle, with anterior tooth.

Remarks

When the genus Westheidesyllis was proposed, only three species were recognized: W. corallicola ( Ding & Westheide, 1997) , W. gesae ( Perkins, 1981) , and W. heterocirrata ( Hartmann-Schröder, 1959) .

Two species of the genus, W. gesae and W. heterocirrata , are very similar morphologically. Westheidesyllis gesae has long and thin spines on the anterior and midbody falciger blades, ciliation on the prostomium and as transversal bands of cilia in each segment, and proventricle extending for about three segments, with approximately 23 muscle-cell rows. Westheidesyllis heterocirrata has relatively thicker spines on the falciger blades, proventricle extending for about two segments, with 14 muscle-cell rows, and does not have transversal ciliary bands on the segments. However, the identification of ciliation patterns can be difficult without proper fixation methods and examination under SEM ( San Martín & Aguado 2012), an issue particularly important in genera for which this character is important, such as Westheidesyllis . For instance, ciliation in some paratypes of W. gesae could not be visualized properly under optical microscopy, except at the bases of dorsal cirri (MVF pers. obs.), and the transverse ciliary bands might not be present in some specimens of this species from the Mexican Pacific ( Salcedo-Oropeza et al. 2016). Additionally, although the original description of W. heterocirrata does not mention this character, tufts of cilia could be observed at the bases of the dorsal cirri of the holotype (MVF pers. obs.). Moreover, W. gesae was described from Florida and with reports from the Atlantic coast of the United States, the Gulf of Mexico and the Caribbean, while W. heterocirrata was described from and only known to occur in El Salvador, in the Pacific Ocean ( Read & Fauchald 2023b). Thus, the Isthmus of Panama is the geographic barrier between the two species, and that should be considered in the revision of this genus, that preferably should use SEM.

Although W. gesae had been recorded in Brazilian waters, specifically in the Rocas Atoll ( Paiva et al. 2007, as Pionosyllis gesae ), no description or information about deposited material was provided. In this study, we describe a new species from the Rocas Atoll , Westheidesyllis splendida sp. nov., which is the first species of the genus described as presenting glands. This character led us to amend the genus, to accommodate this new observation.

Identification key to species of Westheidesyllis San Martín, López & Aguado, 2009

Adapted from San Martín et al. (2009).

1. Eyes absent, but anterior eyespots may be present ........................................................................... 2

– Eyes and eyespots present ................................................................................................................ 3

2. Without eyespots; parapodial glands present; aciculae distally hollow, with tips protruding from parapodial lobes ................................................................................................ W. splendida sp. nov.

– With eyespots; parapodial glands absent; aciculae distally knobbed, not protruding from parapodial lobes .................................................................................. W. coralicolla ( Ding & Westheide, 1997)

3. Transversal ciliated bands on prostomium, peristomium and segments; blades of falcigers with long and thin spines ............................................................................................ W. gesae ( Perkins, 1981)

– Transversal ciliated bands absent, or not as above; blades of falcigers with spines coarser than above ........................................................................... W. heterocirrata ( Hartmann-Schröder, 1959)