Namalycastis Hartman, 1959

Conde-Vela, Víctor Manuel, 2013, Namalycastis occulta n. sp. and a new record of N. borealis (Polychaeta: Nereididae: Namanereidinae) from the Northwestern Caribbean Sea, Zootaxa 3721 (5), pp. 475-487 : 476-482

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Namalycastis Hartman, 1959


Genus Namalycastis Hartman, 1959

Type species. Lycastis abiuma Müller & Grube in Grube, 1872, by original designation (Hartman 1959).

Diagnosis (emended). Four eyes present, rarely absent; four pairs of tentacular cirri. Antennae short, subconical, eversible pharynx without papillae or paragnaths, jaws with single or bifid terminal teeth, generally teeth present along cutting edge. Parapodia sub-biramous (notoacicula ventrally displaced), dorsal cirri enlarged, foliose in posterior chaetigers. Notochaetae spinigers, usually present; neurochaetae falcigers or spinigers. Pygidium with crenulate (multi-incised) rim or tripartite. Gonochoristic or hermaphroditic. Oocytes spherical or ovoid.

Remarks. The subfamily Namanereidinae was proposed by Hartman (1959) for species with reduced or lacking structures typically used for recognizing genera and species, mainly having sub-biramous parapodia and living in fresh and brackish waters. At the same time, she proposed the genus Namalycastis that includes species with four pairs of tentacular cirri and dorsal lobes that increase their size towards the posterior end, and she explicitly designed Paranereis abiuma Müller in Grube, 1871 as the type species for the genus. After the Code (ICZN 1999), because Hartman originally designed the type species (Arts. 67.4, 67.5), this is a fixation by original designation (Art. 68.2), and not by subsequent designation as Glasby (1999) suggested.

Currently, authors have different opinions about the authorship of N. abiuma , even despite the fact that Glasby (1999) tried to clarify this point by indicating it as “(Grube, 1872)”. Some authors disagree and use “(Müller in Grube, 1871)” (Santos & Lana 2000, Salazar-Vallejo & Salazar 2008, Amaral et al. 2012) or “(Müller in Grube, 1872)” (Aungtonya et al. 2002, Lana et al. 2006) and most recently “Müller in Grube, 1871 ” without parenthesis (Magesh et al. 2012). This is incorrect because neither Müller nor Grube described the species under Namalycastis (Art. 51.3, ICZN 1999).

In order to resolve these discrepancies in authority some comments are needed. The publication year, as Glasby (1999) determined, is 1872, because in that year was published the Neunundvierzigster Jahres-Bericht der Schlesischen Gesellschaft für vaterländische Cultur (Transl. 49 th Annual Report of the activities of the Silesian Society of Patriotic Culture), that contained the annual report to 1871 and included four papers of polychaetes previously presented by Grube on January 11, April 5, July 5 and December 13 of that year.

Fritz Müller only appears in one paragraph of the first paper of January 11 (Grube 1872), where Grube indicated that he got two species of Lycastis from Desterro, Brazil, from Müller. Then, he said that Müller referred one as Lycastis littoralis , and the other as a new form of Paranereis (a genus proposed by Kinberg in 1865), P. abiuma . Finally, Grube said that he didn't find reasons to include the latter species in Paranereis , and he described both species and referred them as L. abiuma and L. littoralis . The latter suggests that Müller is the author of the names abiuma and littoralis and that Grube described them under Lycastis . Some contemporary personalities thought the same and they attributed to Müller the authorship, always citing the work of Grube, e.g. de Saint- Joseph (1901) and Gravier (1905). In the catalogue of Hartwich (1993) this species appears as Paranereis abiuma Müller in Grube, 1872, as Hartman (1959) had previously indicated when she designated this species as the type species for the genus (excepting year). However, there is no other manuscript where one can be confident that Müller described both species before Grube, or that they were described together with him. Glasby (1999) commented that maybe Grube paraphrased a letter by Müller, but if such letter exists, has not been made available.

With all this evidence I think they must be considered as co-authors of the species because both contributed to our knowledge, Müller by collecting and naming them and Grube by describing and publishing them, then the authority stays as “Müller & Grube in Grube, 1872 ” (ICZN 1999, Recomm. 51 E).

The reduced or simplified morphological features together with very few unique features in this subfamily complicate discriminating species. In Namalycastis , for example, the main distinctive features are having four pairs of tentacular cirri and the progressive enlargement of dorsal cirri, which are larger than neuropodial lobes, but frequently these are not sufficient for delimiting between species. The newly described species has special and new features for Namalycastis such that the generic diagnosis is emended and these are discussed below and in other sections.

The types of chaetae recognized in the Namanereidinae include simple (capillary chaetae in mature specimens) and compound chaetae which can be falcigers, spinigers, and a third form described for few species: pseudospinigers. This new species has chaetae that could be identified as pseudospinigers, but some comments are needed about this feature. Augener (1933) described for Lycastopsis hummelincki (now Namanereis hummelincki ) a chaetae that he considered intermediate between falciger and spiniger, to which he introduced the term “Pseudo- Grätenborste” or pseudo-spiny bristle. The term alluded to a strongly heterogomph chaetae, whose blade was a transition between falciger and spiniger forms. The blade is shorter than supra-acicular spinigers, but two or three times larger than those of falcigers. Also, the blade is as slender as those seen in spinigers, with the exception of having tapered tips which are not as pointed as in real spinigers (Augener 1933).

The use of the relative length of blades is a doubtful character to distinguish between falcigers and spinigers. Therefore, the denomination must be rather based on the shape of their tips. In the family Syllidae some confusion has occurred when using the blade length for identifying chaetal shapes. San Martín (1991) in his revision of Exogone Örsted, 1845 , proposed to divide this genus into three subgenera ( Exogone , Parexogone and Sylline ) and a brief interpretation of the evolution of shape of the compound chaetae in the genus. Chaetal shapes were differentiated by the length of blades and the degree of modification, and he used spinigers for all chaetae with long blades (San Martín 1991). Harris and Kudenov (1995) clarified that these chaetae really correspond to falcigers with long blades and used the same classification but based in the degree of modification more than length of blades.

The term pseudospiniger has been used in other syllid genera. Syllis Lamarck, 1818 , has a confusing taxonomic history, in terms of recognizing generic categories. Subgenus Ehlersia highlights because Langerhans (1879) included here species with “spinigers” and falcigers. Dorsey & Phillips (1987) noted that several authors divided Ehlersia from Typosyllis by the presence of “spinigers”, but indicated that the long blades are bidentate and therefore are not true spinigers and that the ratio of long to short is more accurate to define them. San Martín (1992), attending these authors, proposed the term pseudospiniger to describe falcigers with elongated blades, homologous to the true spinigers of other polychaetes as the nereidids. Finally, since pseudospiniger appears in species without direct relationship and the division into subgenera is practical rather than scientific, he concludes that the character should not be used to distinguish between genera or subgenera (San Martín 2003).

Some polychaete glossaries define the term spiniger (but not pseudospiniger) and agree that it refers to chaetae tapered and with a fine tip (Fauchald 1977; Glasby et al. 2000; Rouse & Pleijel 2001), the relative length of blades is not mentioned in any definition. According with them, in sensu stricto, an intermediate form as the one already recognized by Augener and later by others authors is most appropriately described as compound falcigers with long blades. In this paper only the chaetal shapes defined by the previously mentioned glossaries are recognized, and the pseudospiniger term was not used.

On the other hand, the pygidium with tripartite rim was not included in the generic diagnosis. Glasby (1999, figs. 8 b,d) revealed its relevance and included a clear illustration for the typical shape for each genus, but his extended diagnosis only referred to crenulated rim and does not include the tripartite rim that is shared by four species, even more when in the cladistic analysis indicated that the condition of having a tripartite pygidium is an autapomorphy of Namanereis . Certainly, the shape of pygidium is not used as a diagnostic feature, and its recognition has been regarded as problematic (Glasby 1999).

Namalycastis occulta n. sp. Figures 1 View FIGURE 1 and 2 View FIGURE 2 ; Table 1 View TABLE 1

Type material: Holotype. ECOSUR P-0151 and paratypes ECOSUR P-0152 (3), Bahía Chetumal, Quintana Roo, México, 7 Jul. 2011, intertidal, under rocks, in sediment with leaves litter of red mangrove ( Rhizophora mangle ) (18 ° 30 ' 30.82 " N, 88 ° 16 ' 43.61 " W), col. Víctor M. Conde Vela, Astrid E. Te Gómez.

Type locality. Chetumal Bay, Quintana Roo, Mexico, in intertidal sediments.

Additional material: ECOSUR P- 2649 (16), Bahía Chetumal, Quintana Roo, México, 7 July 2011, intertidal, under rocks, in sediment with leaves litter of red mangrove ( Rhizophora mangle ) (18 ° 30 ' 30.82 "N, 88 ° 16 ' 43.61 " O), col. VMCV, AETG; ECOSUR P- 2650 (16), Bahía Chetumal, Quintana Roo, México, 16 July 2012, intertidal, in leaves litter of red mangrove ( Rhizophora mangle ) (18 ° 29 ' 59.51 "N, 88 ° 17 ' 1.81 " O), col. VMCV, AETG.

Description. Holotype complete (ECOSUR P-0151). Body small, subcylindrical, uniform in width anteriorly, tapering over far posterior region, 18 mm long, 2 mm wide, 102 chaetigers. Dorsal side convex, ventral side slightly flattened. Colour in life yellowish, translucent, once preserved turned opaque, solid color in base of prostomium and antennae; without any other pigmentation. No sexual products observed.

Prostomium hexagonal, wider than long with widest part near posterior end, shallowly cleft anteriorly, dorsal depression shallow. Antennae subconical ( Fig. 1 View FIGURE 1 A), extending beyond tip of palpostyle. Eyes absent ( Fig. 1 View FIGURE 1 A).

Peristomium with four pairs of tentacular cirri ( Fig. 1 View FIGURE 1 A). Anterodorsal tentacular cirri 1.5 times longer than anteroventral; posterodorsal tentacular cirri 2.0 times as long as anterodorsal. Posterodorsal cirri extending posteriorly to chaetiger 3. Cirrostyles smooth, without folds; cirrophores slightly differentiable. Phranyx smooth, without paragnaths or papillae. Jaws honey colored with bifid terminal teeth, without teeth on cutting edge ( Fig. 1 View FIGURE 1 C).

Parapodia sub-biramous, notochaetae absent. Dorsal cirri cirriform, increasing greatly in length and becoming foliose posteriorly. Neuropodia well developed, postchaetal ligule subconical, tip rounded. Ventral cirri cirriform, shorter than dorsal cirri and ligule. Cirrophores indistinct ( Figs. 1 View FIGURE 1 D–F).

Neurochaetae in type D arrangement, i.e. supra-acicular chaetae include heterogomph falcigers in preacicular fascicles and sesquigomph spinigers in postacicular fascicles; sub-acicular chaetae include heterogomph falcigers or heterogomph spinigers and heterogomph falcigers in preacicular fascicles.

Supra-acicular falciger coarsely serrated, teeth length decreasing distally, 1 / 12 of length of margin edentulate, rounded tip ( Fig. 1 View FIGURE 1 G). Supra-acicular spiniger finely serrated; fine pointed tip, curved in posterior chaetigers ( Fig. 1 View FIGURE 1 K).

Sub-acicular falciger increasing in length posteriorly; coarsely serrated basally, moderately distally, long blade, tip falcate, rounded, replaced by spiniger in middle and posterior chaetigers ( Fig. 1 View FIGURE 1 I). Sub-acicular spiniger increasing in length posteriorly; coarsely serrated basally, becoming finely distally, long blade and finely pointed tip ( Fig. 1 View FIGURE 1 J). Sub-acicular falciger coarsely serrated, teeth length decreasing distally, 1 / 5 of length of margin edentulate, tip rounded ( Fig. 1 View FIGURE 1 H). Aciculae dark brown, tips slightly paler.

Pygidium with tripartite rim and two lateral lobes. Anal cirri cirriform, smooth, arising ventrolaterally, 1.5 times longer than pygidium width. Prepygidial segment without cirri or chaetae ( Fig. 1 View FIGURE 1 B).

Mature specimens (ECOSUR P- 2650), dorsally spotted with brown pigment, no modifications in parapodia or chaetae. Oocytes spherical, 250–375 µm in diameter, with abundant grains of yolk ( Fig. 2 View FIGURE 2 B); present in mid and posterior chaetigers, occupying up to half of coelomic space ( Fig. 2 View FIGURE 2 C), apparently in alternate pattern ( Fig. 2 View FIGURE 2 A).Testes or sperm not observed.

Variation. The specimens had an average length of 12.55 mm (SD ± 3.19) and a maximum width of 0.7 mm, while the average number of chaetigers was 71 (SD ± 16).

The specimens examined vary in the followings parapodial features: ratio between length of dorsal cirri and length of ligule varies from 1.25 in middle chaetigers to 2.0 in posterior chaetigers; ratio between length of ventral cirri and length of dorsal cirri was 0.5, throughout the body (except posterior chaetigers).The variation of dorsal cirri length between specimens is very small, even if the variation of number of chaetigers is appreciable. Variations in chaetae include: 1–2 heterogomph falcigers and 1–2 sesquigomph spinigers in supra-acicular fascicles; 1–2 heterogomph falcigers with long blades in anterior chaetigers or 1–2 heterogomph spinigers in middle and posterior chaetigers and 1–2 heterogomph falcigers with short blades in sub-acicular fascicles.

Mature specimens show a slight increment in the length of tentacular cirri (the longest reaching chaetigers 4 or 5) and of dorsal cirri, and tend to be larger than non-mature organisms (the largest measures 25 mm, 119 chaetigers). Also, the oocytes in mid-body chaetigers tend to be smaller than in posterior chaetigers and up to four oocytes per segment can be seen, probably in formation states, similar number of oocytes per segment has been reported for Namanereis littoralis (Müller & Grube in Grube, 1872) (Ezhova 2010).

The analysis of correlation ( Table 1 View TABLE 1 ) shows that the relationship between total body length and L 3 is low and non-significant, while the relationship between total body length and L 3, W 3 and W 10 have a slight correlation. The correlation between total body length and number of chaetigers is very strong and significant. Therefore, the width and length of the segments remains practically invariable along the body.

Habitat. This species was found initially in samples of intertidal leaf litter and later it was found in sediment under exposed rocks, at few centimeters of the surface, in the same place where the leaf litter was sampled. There are few rocks in this area and their dimensions are 20 x 30 cm approximately. The species is present in the leaves litter in June and July when the mounds reach 20 cm or more in height and not appears since August to December when the production of leaves decreases (pers. obs.), more details for remaining months are not available.

The environment in which the specimens were collected is polluted by solid waste, mainly plastic and glass bottles and plastic bags. Many studies prove organic pollution in water and sediments in the bay due to the continuous discharges of urban waste and agricultural compounds from Hondo River, which flows into the bay (Álvarez-Legorreta 2009). Moreover, much of the mangrove forest area is deforested and the coast is transformed (Sánchez-Sánchez et al. 2009).

Etymology. The specific name stems from the Latin adjective occultus, a, um, meaning hidden or in secret places, referring to the cryptic habits of this species. It indicates that the polychaete was hidden in leaves litter samples, where it was originally discovered. This species was found in very few places and in very low densities.

Remarks. Namalycastis occulta n. sp. resembles other Namalycastis species having heterogomph falcigers in all parapods and pygidium with tripartite rim, such as N. elobeyensis Glasby, 1999 and N. nicoleae Glasby, 1999 . The new species differs from N. elobeyensis in having falcigers in anterior body region replaced by spinigers in posterior region and having falcigers coarsely serrated, while the other having only one spiniger and having falcigers finely or moderately serrated, and differs from N. nicoleae in the absence of notochaetae. The new species is easily recognizable and unique because it has neither eyes nor teeth in jaws. The absence of eyes is probably an adaptation for its unlighted environments like it has also been recorded in some underground species of Namanereis (Williams 2004) .

The genus Namanereis contains species without eyes; however, all Namalycastis species have two pairs of eyes. In the cladistic analysis of Glasby (1999) the lack of eyes was regarded as an apomorphy, and the eyeless species of Namanereis form a clade: N. beroni Hartmann-Schröder & Marinov, 1977 , N. cavernicola (Solís-Weiss & Espinasa, 1991) , N. hummelincki (Augener, 1933) , N. minuta Glasby, 1999 , N. serratis Glasby, 1999 , N. stocki Glasby, 1999 and N. tiriteae (Winterbourn, 1969) . Two other species, N. araps Glasby, 1997 and N. gesae Fiege & Van Damme, 2002 , could be included in this group. All these species are cryptic living in subterranean or freshwater habitats. Excepting N. araps , N. beroni , N. gesae and N. tiriteae , the remaining species have been recorded from the Grand Caribbean region and their jaws have bifid terminal teeth, being the latter a synapomorphic feature (Glasby 1999), and almost in all of them the jaws have smooth cutting edges. Also, the falcigers with long blades (‘pseudospinigers’) apparently are restricted to preacicular position in subacicular fascicles in six Namanereis species: N. araps , N. cavernicola , N. gesae , N. hummelincki , N. minuta and N. stocki , having type D arrangement and four of them are closely related (Glasby 1999). Conversely, all Namalycastis species recorded have eyes, jaws with single terminal tooth and denticulate cutting edges.

As noted above, the new species shares several features with eyeless Namanereis group and possibly is related with. Such affinity favors the placing of the new species in Namanereis and in fact, the new species is similar to both N. stocki Glasby and N. minuta Glasby mainly by having four pairs of tentacular cirri, bifid jaws and falcigers with long blades in sub-acicular fascicles and by lacking eyes. However, Namanereis species have dorsal cirri with similar length throughout the body and the new species have dorsal cirri that increase in length and become foliose posteriorly. Also, the number of tentacular cirri, the shape of prostomium, antennae, dorsal cirri and oocytes remind more to Namalycastis than Namanereis . Being these features the most relevant to discriminate among genera (Glasby 1999), the new species was regarded as Namalycastis .

One species, Namalycastis nicoleae Glasby, 1999 , has a close affinity with the new species by having ‘pseudospinigers’, small body, posterior dorsal cirri with flattened feature weakly developed, tripartite pygidium and notably this species does not have any evident relationship with other Namalycastis species (Glasby 1999); nevertheless, those chaetae would be considered as homologues of the true spinigers (Glasby 1999) but not of the falcigers with long blades in the new species because they are in postacicular position and therefore in other arrangement (e.g. type A arrangement). In the new species, the determination of the position of falcigers with long blades is doubtful because in some occasions are postacicular position and in other preacicular; this problem was identified by Glasby (1999) in his cladistic analysis and he regarded all as preacicular for being more parsimonious than postacicular. Glasby (1999) indicated that "it is conceivable that all Namanereidinae lacking eyes form a clade whose ancestor also lacked eyes”, so that to ensure the affinity between eyeless Namanereis group and the new species requires a more detailed analysis, even with molecular evidence.

Hermaphroditism is considered a secondary reproductive condition among polychaetes. Several authors suggest that hermaphroditism is one of the adaptations for freshwater habitats and this condition is related to many factors such as body size population, density, difficult mate finding, isolated populations, habitat associations, and others (Aiyar & Subramanian 1936, Ghiselin 1969, Westheide 1984, Premoli & Sella 1995, Giangrande 1997, Puurtinen & Kaitala 2002, Prevedelli et al. 2006, for citing a few).

Hermaphroditism has been regarded as typical in the subfamily but it has been noticed for three species: Lycastis quadraticeps Blanchard in Gay, L y castopsis catarractarum Feueborn and the synonymy of Lycastis ranauensis Feueborn with Namalycastis hawaiiensis becomes to the latter as the sole hermaphroditic species in the genus (Johnson 1908, Feueborn 1931). The new species is similar to the description of Lycastis quadraticeps by Johnson (1908). Initially the spotted pattern was confused with bunches of sperm as Johnson described, but after dissection bunches only appear in epithelial layers and not in coelom. Further, in chaetigers stained with hematoxilin and eosin testes or sperm cannot be recognized, and the same negative result was obtained after methyl-green staining.

An interesting question why males could not be found? The new species would present one of two types of sequential hermaphroditism. In protandry males initially have a small body and become females after reaching a certain size; this is found in populations with clumped spatial distribution and living in mud increase the probability of this sexual strategy more than protogyny (Sella 2006). In this modality, a large body can produce more eggs than a smaller one, increasing the female fecundity and reproductive success; small males are preferred maybe for the low probability to change sex (Sella 2006). Therefore, this may explain the absence of males and why females tend to be larger than non-mature specimens. Consequently, the new species is considered gonochoric but the idea that it is hermaphrodite cannot be completely discarded.

TABLE 1. Variability of morphologic characters of Namalycastis occulta n. sp. (n = 20).

  Body length (mm) L3 (mm) L10 (mm) W3 (mm) W10 (mm) Chaetigers
Minimum 7.00 0.40 1.60 0.40 0.50 46
Maximum 19.00 0.80 2.10 0.60 0.70 104
Average 12.55 0.57 1.77 0.45 0.55 71
Standard Deviation 3.19 0.09 0.15 0.06 0.06 16
Coefficient of correlation, R2   0.4292 0.5870 0.5315 0.5315 0.9138