Sigambra Mueller , 1858

Salazar-Vallejo, Sergio I., Rizzo, Alexandra E., Leon-Gonzalez, J. Angel de & Brauko, Kalina M., 2019, Four new Caribbean Sigambra species (Annelida, Pilargidae), and clarifications of three other Sigambra species, ZooKeys 893, pp. 21-50 : 21

Sigambra Mueller, 1858

Sigambra Müller, 1858: 214; Pettibone 1966: 179 (reinstated); Licher and Westheide 1997: 2 (key to species); Nishi et al. 2007: 65 (table with characters of all species).

Type species.

Sigambra grubii Müller, 1858, by monotypy.

Diagnosis.

Pilarginae with body depressed, usually obconic. Prostomium with three antennae, longer than palps; palps biarticulate. Tentacular cirri as long as half width of tentacular segment. Parapodia biramous. Dorsal and ventral cirri foliose to tapered, dorsal ones usually longer than ventral ones. Notopodia include dorsal hooks along many segments, sometimes with accessory capillaries. Neuropodia with shorter pectinates, medium-sized denticulates, and longer finely denticulate capillaries, often twisted distally.

Remarks.

Sigambra species were reviewed by Licher and Westheide (1997), and they modified the orthography for the type species, using grubei instead of grubii , as originally introduced, and included a key to species. However, Sigambra grubii does not need an orthographic modification. As was customary in the times, Müller (1858) did not include etymologies for his new taxa. Licher and Westheide (1997: 4) referred to article 31a of the code ( ICZN 1985: 61, 1999: 37) in an aim to change the orthography for the specific epithet to grubei . This was incorrect because of three reasons: First, they apparently misunderstood the corresponding examples for the same section in the code, especially the last one (reiterated in the most recent edition): 'Cuvier, if Latinized to Cuvierius, gives cuvierii.' Second, the original epithet was not modified by either De Quatrefages (1866: 89), nor Pettibone (1966: 182), both had a good knowledge of Latin, and Licher and Westheide (1997: 3) referred to these publications. And third, Licher and Westheide overlooked the proposals of two other species using the same epithet ( Onuphis grubii von Marenzeller, 1866, and Arenicola grubii Claparède, 1869), which would underline the fact that the original orthography was correctly formed once the last German name was Latinized. Consequently, the original orthography must be retained.

Sigambra Müller, 1858 resembles Ancistrosyllis McIntosh, 1879 by having dorsal hooks above the dorsal cirri ( Salazar-Vallejo and Rizzo 2009: 431). They differ by the relative size of the antennae, tentacular and dorsal cirri, and body papillation. In Sigambra these appendages are long, foliose to tapered, usually antennae are longer than palps, and the integument is mostly smooth, whereas in Ancistrosyllis appendages are short, usually digitate, palps are longer than antennae, and integument is mostly papillate.

Diagnostic features for all the then known species were tabulated by Nishi et al. (2007). Specific diagnostic features are included below in the key to species. Anterior end features include the relative length of median antennae, the length of tentacular segment and presence of modifications along its anterior margin, the presence of ventral cirri on chaetiger 2, and of a constriction on anterior chaetigers. Parapodial features include the relative size of dorsal and ventral cirri, the start of dorsal hooks and their presence along body, and the type of neurochaetae. For the pharynx, the number of marginal papillae is especially useful. There are two patterns regarding the start of dorsal hooks. In the first, their start tends to be more or less stable, with a very small variation (2-4 chaetigers) disregarding variations in total size or number of chaetigers. In the other pattern, notohooks start at an earlier chaetiger in smaller specimens, and they are apparently displaced posteriorly during ontogeny, such that larger specimens will have dorsal hooks from a more posterior chaetiger. Further, notohooks along a few anterior chaetigers are often embedded in the notopodial bases, such that it is necessary to observe the specimen under a compound microscope to precise on which chaetiger notohooks arise. This implies that a series of specimens of different size, collected from the same date, and from similar depths, and sediment types, should be analyzed before deciding which alternative to follow in the key below. If available, size ranges were included in parenthesis to help guide decisions in the key, following Nishi et al. (2007).

There are four other potentially useful characters. First, the prostomial dorsal surface between the palps (interpalpal region) can be characterized by its anterior margin as blunt or depressed, and by the lateral depressions being widened posteriorly, or rectangular if the lateral depressions are more or less parallel. Second, in some species there is a deep antennal furrow for each lateral antenna; they can be easily noted if distinct, or as indistinct if they are difficult to see; further, antennal furrows are often narrower medially, and then they can diverge slightly, being almost parallel, or markedly divergent. Third, in some species, the ventral cirri can be short, not reaching neuropodial lobes tips, whereas in other species, ventral cirri can reach and even surpass neurochaetal lobes in medial or posterior parapodia. Fourth, the number of posterior chaetigers without hooks: in posterior chaetigers the dorsal hooks tend to be more exposed and are usually larger than those present in medial chaetigers or larger than parapodial lobes.