Nereis confusa, Conde-Vela, Victor M. & Salazar-Vallejo, Sergio I., 2015

Conde-Vela, Victor M. & Salazar-Vallejo, Sergio I., 2015, Redescriptions of Nereisoligohalina (Rioja, 1946) and N. garwoodi Gonzalez-Escalante & Salazar-Vallejo, 2003 and description of N. confusa sp. n. (Annelida, Nereididae), ZooKeys 518, pp. 15-49 : 30-34

Taxon classification Animalia Phyllodocida Nereididae

Nereis confusa sp. n. Figures 5, 6C, F–H, N, P

Nereis (Neanthes) oligohalina Berkeley and Berkeley 1958: 402 (non Rioja, 1946).

Nereis oligohalina Berkeley and Berkeley 1960: 359 (non Rioja, 1946).

Type material.

Gulf of California, Baja California Sur. Holotype ECOSUR 0174 and paratypes ECOSUR 0175 (5), Bahía de La Paz (24°08'38.68"N, 110°20'44.40"W), March 1 2004, 70 m from shore, on wrinkled pen shell Pinna rugosa , sponges, PVC tube, and filamentous green algae, Coll. M.A. Tovar-Hernández, P. Salazar-Silva.

Additional material.

Gulf of California, Baja California. ECOSUR P2836 (16), Bahía de Los Ángeles (28°58'6.72"N, 113°32'43.24"W), Gulf of California, March 17 1985, on Atrina maura , Coll. E. Aguirre, C. Garza. Gulf of California, Sinaloa. ECOSUR P2837 (10), Estero el Yugo (23°18'8.30"N, 106°29'0.53"W), Mazatlán, February 24 2004, 50 cm depth, fine sediment, on filamentous green algae on mangrove roots, Coll. S. Rendón-Rodríguez, Nuri M., M.A. Tovar-Hernández, P. Salazar-Silva. Baja California Sur. ECOSUR P2838 (32), same data as holotype. ECOSUR P2839 (2), Bahía La Paz (24°12'6.51"N, 110°17'59.26"W), Gulf of California, March 2 2004, 1 m depth, on basalt rocks, sponges and algae, Coll. M.A. Tovar-Hernández, P. Salazar-Silva.

Etymology.

The specific name (L. confusa: confused, perplexed, troubled) indicates an earlier problematic delineation of the species; it is a noun in apposition.

Description.

Holotype complete (ECOSUR 0174), atokous female. Body tapering, 34 mm long, 1.7 mm wide, 81 chaetigers, inmature. Body yellowish, reddish brown pigmentation present dorsally on first quarter of body as three spots pattern, two lateral ones, and the other less pigmented, middorsal, forming discontinuous transverse bands up to chaetiger 10, remaining segments pale; lateral pale lines in anterior chaetigers only (Fig. 5A). Prostomium with pigmentation brown on inner margins of palps and with two oval patches (Fig. 5A); peristomium dorsally pigmented, variegated (Fig. 5A), with very short pale lines on posterior margin.

Prostomium longer than wide; antennae cirriform, extending beyond palps; eyes subequal, black, in a rectangle (Fig. 5A). Peristomium twice longer than first chaetiger; tentacular cirri with short ceratophores, dorsal cirri longer than ventral ones, posterodorsal ones reaching to chaetiger 5 (Fig. 5A).

Pharynx dissected, jaws with 8 teeth, restricted to anteromedial edge, light brown (Fig. 5I). Maxillary ring: I = 5 cones in rectangle, II = 30-30 cones in arc, III = 49 cones in an ellipse, IV = 41-36 cones and some merged, in sigmoidal. Oral ring: V = 1 cone, VI = 5-5 cones in round, VII-VIII: 42 in two irregular rows, P-bars and small cones alternating in most anterior row, pyramids and small cones in most-posterior row.

Parapodial cirri pattern: Dorsal cirri longer than upper dorsal ligules throughout body; basally inserted on anterior region, displaced medially on midbody and posterior regions. Ventral cirri as long as neuropodial ligules in a few anterior chaetigers, progressively reduced throughout body; basally inserted in anterior region, migrating ventrally throughout body.

First two chaetigers uniramous, remaining biramous. In uniramous parapodia (Fig. 5D), dorsal cirri basal, slightly longer than dorsal ligules. Dorsal ligules subconical; neuroacicular ligules subconical, subequal to dorsal ligules; neuropodial ventral ligules digitate, shorter than neuroacicular ligules. Ventral cirri subequal than neuropodial ligule; dorsal cirri slightly wider than ventral ones.

In anterior parapodia (Fig. 5E), dorsal cirri medial, as long as notopodial dorsal ligules, extending beyond them. Notopodial dorsal ligules subconical; notopodial ventral ligules globose, subequal to dorsal ones, notoacicular papillae conspicuous. Neuroacicular ligules subconical, postchaetal lobe rounded, subequal than neuroacicular ligules; neuropodial ventral ligules digitate, shorter than neuroacicular ones. Ventral cirri shorter than neuropodial ligule; dorsal cirri slightly wider than ventral ones.

In midbody and posterior parapodia (Figs 5 F–H), dorsal cirri medial, subequal to notopodial dorsal ligules. Notopodial dorsal and ventral ligules subequal, slightly enlarged in posterior parapodia, subconical, longer than wide, notoacicular papillae conspicuous in middle parapodia. Neuroacicular ligules subconical, postchaetal lobes rounded, shorter than notopodial ligules; neuropodial ventral ligules digitate, slightly shorter than neuroacicular ones. Ventral cirri shorter than neuropodial ventral ligules; dorsal cirri slightly wider than ventral ones (Fig. 5 F–H).

In anterior and midbody parapodia, notochaetae homogomph spinigers; neurochaetae homogomph spinigers and heterogomph falcigers in supra-acicular fascicles, heterogomph spinigers and falcigers in sub-acicular fascicles. In posterior parapodia, notochaetae homogomph spinigers and falcigers; neurochaetae as in anterior parapodia.

Notopodial homogomph spinigers pectinate, teeth decreasing in size distally. Notopodial homogomph falcigers pectinate, 9 teeth, distal tooth stout, incurved, fused to blade (Fig. 5C). Neuropodial homogomph spinigers basally serrate (Fig. 5J), heterogomph spinigers pectinate or serrate (Fig. 5K); both with teeth decreasing in size distally. Neuropodial heterogomph falcigers pectinate, distal tooth incurved, fused to blade, very conspicuous (Fig. 5 L–N); in posterior parapodia with short (Fig. 5M) or long (Fig. 5N) blades in both fascicles, missing in most chaetae.

Pygidium with broad margin, anus crenulated; anal cirri cirriform, as long as last 3-4 segments (Fig. 5B).

Variation.

The results of the analysis of body variation and paragnath numbers are summarized in Table 1 and 2. The arrangement and number of paragnaths is similar to that in Nereis oligohalina and Nereis garwoodi , but in Nereis confusa sp. n. paragnaths in areas III and IV are more numerous than in the other two species (Fig. 6C, F; Table 2), and cones have rounded tips; further, Nereis confusa sp. n. is the only species of the three with merged paragnaths.

All specimens examined show the same dorsal spotted pigmentation, but in some, especially the largest specimen, the middorsal spot disappears and only two discontinuous lines are visible along chaetigers 1-10; fingerprint-like or striated patterns were not observed. In mature specimens, the transformation starts in chaetiger 18 in males, 22 in females as previously noticed by Berkeley and Berkeley (1958, 1960).

Remarks.

Nereis confusa sp. n. has been recorded as Nereis oligohalina ; however, there are several differences between these two species. In Nereis confusa sp. n. the spotted pigmentation pattern extends up to chaetigers 10-14, and the jaws have 8 teeth restricted to the distal part of its inner edge, whereas in Nereis oligohalina the pale areas are replaced by fingerprint-like patterns from chaetiger 11, and its jaws have 11 teeth along its inner edge. Further, in Nereis confusa sp. n., both notopodial ligules and neuroacicular ligules are subequal to, or slightly longer than, neuropodial ventral ligules in midbody and posterior parapodia, whereas in Nereis oligohalina , they are twice as long as the neuroacicular ligules in midbody and posterior parapodia. On the other hand, Nereis confusa sp. n. has falcigers with broad blades, whereas in Nereis oligohalina they are narrower. Furthermore, in Nereis confusa sp. n. distal tooth of notopodial homogomph falciger is short and well developed, whereas in Nereis oligohalina it is longer and weakly developed.

The first records for Nereis confusa sp. n. (as Nereis oligohalina ) from the Mexican Pacific were made by Berkeley and Berkeley; first, they reported Nereis (Neanthes) oligohalina males from Hipolito Bay ( Berkeley and Berkeley 1958), and males and females from La Paz ( Berkeley and Berkeley 1960). They argued that prostomium, anterior chaetigers and arrangement of paragnaths all matched Rioja’s descriptions. In their brief comments, they indicated the start of the modified region or first epitokous parapodium (17 in males, 22 in females), and a spotted pattern of pigmentation in males. These features match with Nereis confusa sp. n. rather than Nereis oligohalina .

Rioja (1962) cited Berkeley and Berkeley (1958), and recorded Nereis confusa sp. n. (as Nereis oligohalina ) from El Mogote, Ensenada de La Paz, Baja California Sur; he mentioned a slight discrepancy in number of paragnaths in area I, and that paragnaths in the periphery of area III were larger than the rest of the group forming a borderline; also, he regarded the glandular parapodial masses as typical. Despite the fact that he did not provide more information, we regard his specimens as belonging to Nereis confusa sp. n. Other Mexican Pacific reports of Nereis pelagica occidentalis by Bastida-Zavala (1993, 1995) from nearby localities might also be conspecific.

Dean (2001) reported Nereis oligohalina from Pacific Costa Rican coasts, noticed the problems in the taxonomic history of the species, and regarded it as different from Nereis occidentalis . According to his description Costa Rican specimens differ from Nereis oligohalina in the number of paragnaths, mainly in areas I, III and IV. Also, in his specimens the longest tentacular cirri reached chaetiger 3, and the notopodial dorsal and neuropodial ventral ligules were subequal to or shorter than notopodial ventral and neuroacicular ligules throughout body, whereas in Nereis oligohalina the longest tentacular cirri reaches chaetiger 7, and their ligules are larger in midbody and posterior chaetigers. Likewise, Costa Rican specimens resemble Nereis confusa sp. n. and probably belong to the same species and this might also include the record from Cocos Island ( Dean et al. 2012). Nevertheless, these records cannot be assigned to Nereis oligohalina unequivocally until specimens are evaluated.

Habitat.

Holotype found on wrinkled penshell Pinna rugosa Sowerby, 1835, sponges and filamentous green algae; other specimens were found in sponges and green algae near the type locality. Specimens from Bahía de Los Ángeles were associated with another penshell, Atrina maura (Sowerby, 1835), and specimens from Estero El Yugo were found on filamentous green algae on mangrove roots. Bastida-Zavala (1995) found specimens on corals.

Distribution.

Gulf of California, Eastern Pacific coasts of Mexico. Probably extends to Costa Rica, in shallow water.

Reproduction patterns and dispersal in Nereis species studied.

Some authors have emphasized the utility of reproductive patterns in taxonomy for species discrimination in closely related taxa ( Smith 1958, Clark 1977). Also, strategies for larvae survival would be relevant, especially because they determine larval transport and its dispersal potential. An interesting strategy is when only males form epotikes and females remain atokous or are barely modified, as in Alitta virens (Sars, 1835) and Websterinereis glauca ( Claparède, 1870). In Alitta virens , males form epitokes but females remain atokous or present very slight changes, also females spawn into or in the opening of their burrows ( Bass and Brafield 1972). In Websterinereis glauca , female transformation is reduced, and females produce mucous tubes to deposit and incubate their eggs, while males can swarm ( Pettibone 1971).

Early studies considered that Nereis garwoodi presented a similar reproductive mode as Alitta virens or Websterinereis glauca , because the paralectotype female of Nereis garwoodi has a slight transformation; however, after further revision of additional material, a fully transformed female was found. We have no further details about its capacity for building mucous tubes or if females do not emerge to the water column or if gametes are retained in tubes.

In the material available of Nereis oligohalina , no completely transformed females were encountered, but perhaps with further sampling efforts they may appear. Another important consideration is the reduced size of males compared to females, even in the same sample; this has been noted for Hermodice diversicolor ( Bartels-Hardege and Zeeck 1990). In this case, Nereis oligohalina males can swarm while females remain inside cavities, as in Alitta virens and Websterinereis glauca ; the fact that there are many large females filled with oocytes points toward this direction.

Reproduction modes in estuarine species play a crucial role in their dispersal because the formation of planktonic larvae can determine their distribution range. Bilton et al. (2002) proposed two life-cycle models for estuarine species that have larvae: export vs retention strategies. In the former, the adults respond to physical or biological factors by releasing gametes or larvae in the lower estuary; larvae are driven out from the estuary, mainly by tides, and later juveniles or adults return to the estuary. In the retention strategy, adults release their gametes or larvae in the upper estuarine areas, then they undergo early development in middle estuary; there, larvae have vertical migrations during circadian ebb-flood tidal regimes such that larvae are not exported but retained within the estuary ( Bilton et al. 2002).

Based on the above, we hypothesize that Nereis oligohalina has an export strategy; it could disperse thanks to surface currents running parallel to the continental margin, and this would explain its presence along Gulf of Mexico estuaries. Similarly, distribution of Nereis confusa sp. n., with mainly marine habitats, could be due to current patterns along the Gulf of California.

However, sometimes the distribution patterns cannot be explained by currents and tidal dynamics. For example, De Jesús-Flores et al. (2015) determined that Laeonereis nota (Treadwell, 1941), described for Galveston, Texas, is also present in Chetumal Bay; Laeonereis nota spawn into their burrows, limiting their dispersal by currents. The explanation for this discontinuous distribution lies in passive dispersal through migratory birds, because they use nereidids as food ( De Jesús-Flores et al. 2015). Similarly Nereis garwoodi could have a classical retention strategy, but a wide, fragmented distribution caused by migratory birds.

Further considerations.

The present study demonstrates the need to encourage redescriptions of closely related and widely distributed species and, should it be necessary, the establishment of new species if there are conspicuous morphological differences.

Further, clarifying species delineation and distribution are urgent because they are essential for biogeography and phylogenetics. Reuscher and Shirley (2014) studied the distribution patterns of polychaetes from the Gulf of Mexico; a recent species list was used ( Fauchald and Solís-Weiss 2009) and current taxonomy verified in WoRMS ( Read and Fauchald 2015). They found that among all species recorded, 32% were cosmopolitan, 15% Pan-American and 9% Pan-Atlantic ( Nereis oligohalina was regarded as Pan-American, which is incorrect as shown above). They concluded: "Most polychaete families are in need of global and regional revisions. Clear species boundaries have to be established by means of taxonomic research based on morphology and genetic analyses. Geographical ranges of species should be revised in order to eliminate false conclusions about distributions of species."