Parasphaerosyllis indica Monro, 1937: 273, text-fig. 8.— Fauvel 1939: 298 (Annam Sea, French Indochina); Fauvel 1950: 351 (Dakar, Senegal); Fauvel 1953: 162, fig. 80c–d (Arabian coast); Rioja 1958: 246–251, figs. 21–27 (Isla Verde, Gulf of Mexico); Fauvel and Rullier 1959: 514–515 (Gorea Island, Senegal); Hartmann-Schröder 1965: 115 (Maui, Hawaii); Hartmann-Schröder 1980: 49 (Exmouth, northwest Australia); Hartmann-Schröder 1987: 32 (Victoria, Australia); Hartmann-Schröder 1991: 27 (Queensland, Australia); Rullier 1964: 165 (Cameroon); Rullier 1972: 69 (New Caledonia); Westheide 1974: 64–67, figs. 27–29 (Galapagos); Cantone 1976: 230 (Somalia); San Martín 1991: 234 (Cuba); San Martín et al. 2008: 146, figs. 19E–F, 22A–E, 24A–B (Tasman Sea and Western Australia); Liñero-Arana and Díaz-Díaz 2011: 24, figs 4.8–4.10 (Venezuela); Aguado et al. 2015: 49, figs. 5F (Lizard Island, Australia); Cañete 2017: 1070–1071, figs. 1a–g (Easter island, Chile).

Holotype incomplete posteriorly, 5 mm long, 0.4 mm wide on proventricle, 68 chaetigers. Body subcylindrical, ventrally flattened (segments 15 and 16 from anterior end remarkably wider than rest of body, perhaps due to manipulation caused by strong pressure on slide cover, because proventricle is broken and pharynx flattened). Body brown-yellowish, without pigmentation pattern. All cirriform annulated appendages deeply coiled (Fig. 1A). Prostomium pentagonal, wider than long. Four lensed eyes in trapezoidal arrangement, eyes from the anterior pair larger and more separate than posterior pair of eyes (Fig. 1A). Right anterior eye divided into two lobes, appearing to have two fused eyes. Eyespots absent. Palps stout, triangular, slightly directed towards the ventral side, similar in length to prostomium, only fused in a small part of base. Median and right antennae lost. The median antenna preserves the cirrophore and the first annulation only, which arises from posterior end of prostomium, between posterior pair of eyes (Fig. 1A). Left lateral antenna inserted on anterior margin of prostomium, longer than prostomium with 7 articles of different sizes in irregular arrangement (Fig. 1A). Peristomium shorter than subsequent segments, folding on posterior part of prostomium (Fig. 1A). Peristomium with two pairs of tentacular cirri: dorsal ones with 24 articles each, right ventral cirrus with 14 articles, left ventral cirrus incomplete, with 7 articles. First pair of dorsal cirri with 24 articles each. Dorsal cirri from chaetigers 2 to 17 with 20–24 articles, not alternating in length. Mid-body dorsal cirri with 20–22 articles and posterior cirri with 15–18 articles. The first bulbous cirrus appears on chaetiger 15 on left side, whereas on the right side appears on chaetiger 17. From chaetiger 17 backwards, dorsal cirri alternate regularly, one by one: an annulated cirri and a bulbous one. Bulbous dorsal cirri elongate, cirrophore not visible (Fig. 1B). Base of bulbous cirri thin, enlarged medium part and a small unarticulated knob at the end (Fig. 1B–E). Bulbous cirri with curved diagonal fibrous lines, being more evident on some cirri than others. Some annulated cirri broken (incomplete) or fully removed (only scars are evident). Parapodial lobes slightly wide on base, with one or two notorious acicular papillae. Ventral cirri digitiform, shorter or similar in length than parapodial lobe. Anterior parapodia with about 10 compound heterogomph chaetae (6 on chaetiger 1), number diminishes gradually through the body to 6 on posterior segments. Falcigers dorso-ventrally decreasing in length, bidentate blades with thin spines on its internal margin, shafts with small and fine distal spines. Falcigers from anterior chaetigers with blades longer and thinner than posterior ones (Fig. 1F–G). Size proportion between dorsal-most versus ventral-most blades: anterior one 2.0 to 2.1, posterior one 1.5 to 1.6. Simple acicular chaetae, dorsal or ventral, not observed. Anterior parapodia each with two slender aciculae: one straight, pointed and other distally curved, acute. Mid-body and posterior segments with one acicula per parapodium, larger and thicker than anterior ones, distally curved. Pharynx occupying the space of about seven segments, pharyngeal tooth located anteriorly, pointed, acute, yellowish. Proventricle broken, longer than pharynx, extending through 8–9 segments, with about 22 muscle cell rings, with distinct mid-dorsal line. From chaetiger 62 backwards, forming a male stolon (damaged).

Figure 1.  

Parasphaerosyllis indica Monro, 1937 (holotype BMNH1937.9.2.156.). A Anterior end, dorsal view; B Middle anterior segments, dorsal view; C Bulbous dorsal cirrus, chaetiger 24; D Bulbous dorsal cirrus, chaetiger 40; E Bulbous dorsal cirrus, chaetiger 62; F Falcigers from chaetiger 10; G Falcigers from chaetiger 60. Scale bars: A, B = 0.2 mm; C, D = 0.1 mm; F, G = 20 µm.

Figure 2.  

Line drawings of Parasphaerosyllis irregulata sp. nov. (holotype UANL 8158). A Anterior end, dorsal view; B Middle section of body, dorsal view; C Posterior bulbous and moniliform dorsal cirri, chaetiger 260; D Acicula, chaetiger 10; E Acicula, posterior chaetiger; F Ventral simple chaeta, chaetiger 302; G Dorsal simple chaeta, chaetiger 302. Scale bars: A, B = 0.5 mm; C = 0.25 mm; D–G = 20 µm.

Figure 3.  

Line drawings of Parasphaerosyllis irregulata sp. nov. (holotype UANL 8158) A Falcigers from chaetiger 10; B Falcigers from chaetiger 40; C Falcigers from chaetiger 90; D Falcigers from chaetiger 250. Scale bar: A = 20 µm.

Figure 4.  

Scanning electronic micrographs of Parasphaerosyllis irregulata sp. nov. (paratype UANL 8160). A Anterior end, dorsal view, arrows point to insertion scars of dorsal cirri; B Prostomium and first anterior segments, dorsal view; C Alternated bulbous and moniliform dorsal cirri from mid-body region; D Posterior segments showing different development stages of bulbous dorsal cirri; E Bulbous dorsal cirrus showing dorsal band of several lines of pores; F Detail of ciliate pores on bulbous dorsal cirrus. Scale bars: A, B = 0.5 mm; C, D = 50 µm; F = 5 µm.

Figure 5.  

Scanning electronic micrographs micrographs of Parasphaerosyllis irregulata sp. nov. (paratype UANL 8160). A Middle section of the body, dorsal view, square showing an enlargement of a spherical cirrus with two terminal articles; B Posterior section of the body, dorsal view, where “b" means bulbous cirrus and “m” moliniform cirrus; C Terminal end, lateral view; D Anterior parapodium with falcigers; E Falcigers from middle body; F Falcigers from posterior parapodia. Scale bars: A, B = 0.5 mm; C = 0.1 mm; D, F = 10 µm, E = 5 µm.

Palps fused at their bases. Peristomium shorter than following segments. Dorsal cirri from mid-body bulbous with a long distal end and terminal knob, alternating with long and articulate cirri in a regular pattern (one by one). Bidentate falcigers with long blades, proximal tooth shorter than distal one.

Parasphaerosyllis indica was described from the coast of Oman to 13.5 m depth. It has been reported in many localities around the world. Unfortunately, many of these reports include only a brief mention or just the name within a list of species or tables of ecological analyses and compendia, making its status unverifiable: Hartman (1954) (Eniwetok Atoll); Reish (1968) Marshall Islands); Amoreux et al. (1978) (Gulf of Aqaba and Gulf of Suez); San Martín (1991) (Cuba); Núñez et al. (1992) and Pascual and Nuñez (1999) (Canary Islands); López and San Martín (1994) (Cape Verde Islands); Bastida-Zavala (1995) (Gulf of California, Mexico); Gómez et al. (1997) (Oaxaca, Mexico); Pleijel (2006) (New Caledonia) and Hutchings et al. (2014) (Australia). Aguado et al. (2015) already suggested that the presence of P. indica may represent a complex of species at least in Australia (Western Australia, Queensland, New South Wales and Victoria), but also it may be the same case in other disjunct localities.

On the other hand, several authors have reported P. indica through the decades, providing brief diagnoses/descriptions and illustrations that allow comparison with the re-description provided here (Table 1). The characters listed in Table 1 show great variability amongst all these records, demanding a detailed examination of voucher specimens. In addition, a study of ontogenetic variability is desirable, with special emphasis on the analysis of the following features that might be informative and consequently used in the recognition of species in Parasphaerosyllis:

• insertion of median and lateral antennae;
• extension of pharynx and proventricle and its size relationship;
• presence or absence of cirrophore in bulbous dorsal cirri;
• chaetiger where bulbous dorsal cirri appear;
• presence and number of terminal articulations in bulbous dorsal cirri;
• alternation pattern of moniliform/bulbous dorsal cirri (one by one or another pattern);
• presence of pseudosimple chaetae; dentition of falcigers;
• presence and distribution pattern of glands or pores in bulbous dorsal cirri (but this feature is only revealed using SEM).

Regarding the generic features of Parasphaerosyllis, the genus was established by Monro (1937) as having fused palps, except at the extreme tip in the type species (P. indica); and dorsal cirri from the mid-region including two types: moniliform (articulated or annulated) and bulbous, both being alternating (one by one). In recent generic diagnoses provided to Parasphaerosyllis by San Martín et al. (2008) and San Martín and Aguado (2019), it is stated that the genus has palps fused only basally and dorsal cirri from mid-body being short, unarticled, lemon-like alternated with articulate cirri. Additionally, the holotype of P. indica here examined has palps fused only basally, contrary to the original description by Monro (1937). Regarding the term dorsal cirri being “lemon-like”; in our opinion, this is subjective because it does not reflect the shape of these structures in all of the four species currently valid in the genus. Lemon-shaped can be spherical (as green lemon or lime) or ovoid (as yellow lemon) or pyriform and corrugated (as other lemon varieties). For instance, the dorsal cirri, originally described and illustrated by Monro (1937) (text fig. 8b), are bulbous with a terminal knob, which agree with the re-examination of the holotype (this study, Fig. 1B–E). In P. malimalii, dorsal cirri from the mid-region are ovoid or bulbous with a terminal knob (Capa et al. 2001, figs. 1B and D; this study, Fig. 6A), in P. ezoensis, these cirri are bulbous with knobs composed of two terminal articles (Imajima and Hartman 1964, plate 28, fig. b), in P. uschakovi, the cirri are bulbous with knobs composed of 2–3 terminal articles (Chlebovitsch 1959, fig. 1b and r) and, in the new species described below (P. irregulata sp. nov.), these cirri are spherical to bulbous and knobs have 1–3 terminal articles (Fig. 2B–C and Fig. 4C–E). Besides, the report of “P. indica” in Western Australia and Tasman Sea by San Martín et al. (2008) described the cirri as lemon-shaped, but it seem more like bulbous in the sense of this contribution.

Figure 6.  

Digital photographs of Parasphaerosyllis malimalii Capa, San Martín and López, 2001 (UANL 8160). A Mid-body segments, showing bulbous and moniliform dorsal cirri; B Falcigers from chaetiger 10; C Falciger and pseudosimple chaeta from middle parapodium; D Pseudosimple chaetae from posterior parapodium. Scale bars: A = 50 µm; B–D = 20 µm.

Moreover, there is variation in the holotype of Parasphaerosyllis indica here examined versus the description by Monro (1937) (p. 274). He described the body as “slender and thread-like”, but we find that it is sub-cylindrical, widened in the first 15–16 segments to the posterior part of proventricle. The holotype is posteriorly incomplete, most of the stolon described by Monro having disappeared, perhaps due to over-handling of the specimen since other damage can be observed, such as the loss of the median and right lateral antennae.

According to the image provided by Monro (1937): fig. 8a, the insertion of the lateral antennae is located between the superior and the inferior pair of eyes, but in the holotype, lateral antennae are inserted on the distal margin of prostomium and the only visible antenna (left one) is incomplete, having only seven articles. The number of articles in the dorsal tentacular cirri varies; Monro illustrates tentacular cirri in his figure 8a with 20 articles on the left side and 21 on the right; but, the dorsal tentacular cirri in the holotype have 24 articles on both sides. Finally, Monro's figure 8b shows the bulbous cirri attached to the parapodium by a prominent cirrophore. When observing the holotype, we saw that parapodia do not have cirrophores and some cirri show different degrees of basal thinning (Fig. 1C–D).

Holotype complete, 35 mm long, 0.9 mm wide, 310 chaetigers. Body pale yellowish, without colour pattern, subcylindrical, ventrally flattened. Prostomium oval, wider than long. Two pairs of eyes in trapezoidal arrangement. Eyes of anterior pair longer than inferior pair, closer to external border of prostomium. Eyespots absent (Fig. 2A). Three annulate antennae. Median one with 26 articles, located in middle prostomium, between posterior eyes. Lateral antennae inserted in the anterior border of prostomium, with 16 articles each. All antennae longer than prostomium and palps. Palps subtriangular, slightly shorter than prostomium, free at their base (Fig. 2A). Peristomium as long as first chaetiger (Fig. 2A, Fig. 4A–B), with two pairs of tentacular cirri, dorsal ones with 24–25 moniliform articles, ventral ones with 13 articles each (Fig. 2A, Fig. 4A–B). Buccal hole with two large lateral edges and a central fissure formed by three irregular pleats. Dorsal cirri long, articulated. Articles near to cirrophore sub-rectangular, wider than long, following ones moniliform; distal article and, on occasions, subdistal ones longer than wide. First pair of dorsal cirri long, with 18 articles each. Cirri from second to sixth parapodia with 16–18 articles. After proventricle end, dorsal cirri alternating one by one (short and long), with 14–18 and 20–22 articles, respectively. In chaetiger 44 appear the first bulbous dorsal cirrus on right side only, with moniliform cirri on left side. From that region to the end of body, articulated cirri with 12–22 articles, with the exception of the last segments where it is growing and has few articles. Nearly spherical dorsal cirri in certain segments (Fig. 4C and E), while, in others, they are bulbous with distal part lengthened (Fig. 2B and Fig. 4D). The presence of spherical/bulbous cirri is irregular, not alternating one by one with moniliform cirri in all segments, but a series of up to 10 bulbous cirri can be present or 3 moniliform cirri in a row, although, sometimes, bulbous and moniliform cirri appear in the same segment forming asymmetric segments (Fig. 5A–B). Distal end of bulbous cirri with an unarticulated knob, smooth (Fig. 4C and E), although, in some cases, three or four terminal articles are present on posterior segments (Fig. 2C and Fig. 4D). Bulbous cirri with a dorsal band composed of several lines of pores (Fig. 4C–E, Fig. 5A–B and E–F), from which numerous groups of filaments or cilia are observed (Fig. 5E–F). Bulbous cirri present until before the last 20 chaetigers (Fig. 6B). Subconical parapodial lobe, truncate distally (Fig. 4D). Ventral cirri conical, distal end rounded, shorter than length of parapodial lobe. Anterior and median chaetigers with two aciculae per parapodia, one of these thicker than the other, both bent lightly in the distal end (Fig. 2D–E). Posterior parapodia with one acicula, similar in shape to the anterior ones. Anterior parapodia with 9–13 falcigers per fascicle, clearly bidentate with short blades, subequal teeth. Rate of size between dorsal-most versus ventral-most blades: 1.4 (Fig. 3A, 5D). Median parapodia with 10–13 bidentate falcigers. Blades of falcigers longer than anterior ones, secondary tooth slightly longer than apical one. Size proportion between dorsal-most versus ventral-most blades: 1.2 (Fig. 3B and Fig. 5E). Posterior parapodia with around 10 falcigers, similar of those of median parapodia, gradation dorso-ventral 1.5–1.6 (Fig. 3C). Pre-pygidial parapodia with 6–7 falcigers, larger than those of anterior parapodia, but similar in shape (Fig. 3D and Fig. 5F). Dorsal and ventral simple chaetae present on last eight chaetigers (chaetiger 303); dorsal simple chaetae thick and clearly bidentate (Fig. 2F), the ventral one very thin and slightly bidentate (Fig. 2G). Pharynx extending through 6 segments, anteriorly surrounded by 10 soft papillae, approximately 1.4 times longer than the length of proventricle, with a thin and acute mid-dorsal tooth inserted anteriorly. Proventricle extending through three segments, with 18 muscle cell rows (Fig. 2A). Three anal cirri, two lateral articulated with 13 articles and one mid-ventral smooth, very small (Fig. 5B–C).

Palps free at their bases. Peristomium as long as first chaetiger. Dorsal cirri from mid-body spherical to bulbous with a long distal end, alternate with long and articulated cirri in an irregular pattern (they are not alternating one by one, both kinds of dorsal cirri may appear on the same segment). Bulbous and spherical dorsal cirri mostly with an unarticulated knob, but those from posterior segments can have two to four distal articles. Bidentate falcigers with short, subtriangular blade, proximal tooth slightly larger than distal one.

The specific name refers to the irregular presence of bulbous and moniliform dorsal cirri.

Only known from the type locality.

The specimens were captured among biofoulers such as coralline algae, bryozoans, hydrozoans and tubes of polychaetes Spirobranchus spp., attached to pyramidal cement structures commonly used to fix coral Pocillopora spp. fragments.

Schizogamy. Formation of unique dicerous stolon.

Parasphaerosyllis irregulata sp. nov., differs from other species in the genus by having palps free at their base (P. ezoensis, P. indica, P. malimalii and P. uschakovi have palps fused basally) and the presence of an irregular alternation of bulbous and articulated dorsal cirri as follows: spherical to bulbous cirri with 1–3 terminal articulated knobs and moniliform ones, both distributed irregularly, sometimes a spherical/bulbous and moniliform cirrus may appear together within the same segment or only a spherical/bulbous cirrus may appear in several consecutive segments (not alternating one by one as occurs in the other species of the genus). Besides, its is important to emphasise the lost of bilateral symmetry of dorsal cirri in some segments: shape of dorsal cirrus from the right side of a particular segment is not always replicated in the left side as occurs in other species. Furthermore, the size and shape of falciger blades (short and subtriangular) with subequal teeth (proximal tooth slightly larger than the terminal one) is a unique feature (all other four species have falcigers with longer blades than in P. irregulata sp. nov. and proximal tooth being shorter than the terminal one).

The spherical or bulbous dorsal cirri of P. irregulata sp. nov. presumably have glands over its dorsal surface, aligned in several straight rows (Fig. 4E–F), some empty pores are visible, whereas other pores show short filaments or cilia arising from the holes. Their function is unknown, as well as their presence in P. ezoensis and P. uschakovi, but in the record of San Martín et al. (2008): figs. 19E–F, SEM, as "P. indica” from the Tasman Sea (specimen AM W30153), some pores are visible on the surface of bulbous dorsal cirri, but in the figure, it cannot be seen if the pores are aligned in rows as in P. irregulata or in a scattered pattern. Besides, the specimens from Tasman Sea and Western Australia reported by San Martín et al. (2008): fig. 22A, have bulbous dorsal cirri with dark, fibrillar inclusions forming nearly diagonal lines, as well as those illustrated by Capa et al. (2001): fig. 1D to P. malimalli and those here described in the holotype of P. indica. It is unknown if that pattern is distinctive of these three taxa or not or if these are related to pores or glands.

Parasphaerosyllis malimalii Capa, San Martín and López, 2001: 281, figs. 1–2.

The three specimens studied are incomplete posteriorly, the largest being 9.2 mm long and 0.60 mm wide. Body subcylindrical, flattened ventrally, pale yellowish, without pigmentation pattern, with 82 chaetigers. Prostomium oval, wider than long. Four eyes in a trapezoidal arrangement, the anterior pair larger than posterior one. Three articulated antennae, the middle one with approximately 50 articles, inserted in the posterior part of the prostomium between the basal pair of small eyes. Lateral antennae with 21 articles, inserted very close to the anterior edge of the prostomium. Palps short, sub-triangular, directed slightly towards ventral side, equal to or slightly smaller than the prostomium length, fused basally. No nuchal organs are observed. Peristomium slightly shorter than the first chaetiger, covering a small area of the prostomium. Two pairs of articulated tentacular cirri, the dorsal ones with some 40 articles and the ventral ones with 20. Dorsal cirri of the first chaetiger with 45–50 articles, chaetiger 2 (20–21 articles), chaetiger 3 (28–33 articles), chaetiger 4 (30–31 articles), chaetiger 5 (20–21 articles) and chaetiger 6 (37–39 articles). Alternating long and short anterior dorsal cirri with 38–40 and 23–25 articles, respectively. First bulbous cirrus appears at chaetiger 29, regularly alternating one by one with moniliform cirri (Fig. 6A). Elongated bulbous cirri with a smooth, non-articulated terminal knob. In the smallest specimen, the first bulbous dorsal cirrus appears on chaetiger 21. Moniliform dorsal cirri of the median region of the body with 20–22 articles. Parapodial lobe sub-conical, truncated, with two ligules, one anterior and one posterior. Ventral cirrus sub-triangular, inserted at the base, approximately half the length of the parapodial lobe. Anterior parapodia with 9–10 bidentate falcigers per bundle (Fig. 6B). Falcigers with dorso-ventral gradation approximately 2:1. With 5–6 chaetae per fascicle on middle parapodia. One or two pseudosimple chaetae formed by the thickening of the handle and loss of the blade in the dorsal position. Four to five bidentate falcigers with shorter and thicker blades than those of anterior parapodia (Fig. 6C). Posteriorly, the number of pseudosimple chaetae increases (3–4) (Fig. 6D) and that of falcigers decreases (1–2). With three aciculae on anterior segments, one of them with a straight tip and the other two with a slightly bent tip. Mid-body parapodia with two aciculae, both with the tip slightly bent and remaining so until the end of the incomplete specimen. Pharynx through 7–8 segments, with anterior medio-dorsal tooth. Approximately the same length as the proventricle, the latter being 32 muscle cell rings.

Palps fused basally. Peristomium slightly shorter than the first chaetiger, covering a small area of the prostomium. Dorsal cirri from mid-body bulbous with a long distal end, alternating with long and articulate cirri in an irregular pattern (alternated one by one). Falcigerous bidentate with the secondary tooth very small, with pseudosimple setae formed by the thickening of the handle and the loss of the joint in the middle and posterior chaetigers. Pharynx and proventricle nearly the same size.

Eastern Tropical Pacific, from Nayarit and Jalisco (Mexico) to Panama.

Intertidal, associated with mats of coralline algae fixed to rocks at 2 m depth.

One of the specimens has a female dicerous stolon in poor condition of which the characteristic features cannot be seen.

This constitutes the first record of Parasphaerosyllis malimalii since its establishment. It is now reported from Nayarit and Jalisco (Central Mexican Pacific). Parasphaerosyllis malimalii is the only species within the genus to have pseudosimple chaetae formed by the thickening of the handle and loss of the blade. The specimens studied here have some differences from those originally reported to the Pacific of Panama. The median antenna is larger than original description (approx. 50 articles), the alternating anterior dorsal cirri are also larger than those reported by Capa et al. (2001) (with 38–40 and short with 23–25 articles) and the number of chaetae per bundle in anterior chaetigers is also larger (9–10) than the holotype. These differences are probably due to ontogeny.