Parasphaerosyllis indica Monro, 1937

Gongora-Garza, Gerardo, Tovar-Hernandez, Maria Ana & de Leon-Gonzalez, Jesus Angel, 2024, Re-description of Parasphaerosyllis indica Monro, 1937 (Annelida, Syllidae), with the establishment of a new species from western Mexico, Biodiversity Data Journal 12, pp. 116082-116082 : 116082

Parasphaerosyllis indica Monro, 1937

Parasphaerosyllis indica 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).

Materials

Type status: Holotype. Occurrence : occurrenceID: 5F89365A-89A3-5353-9EBC-8135225D86BE; Location : higherGeographyID: Western Indian Ocean; higherGeography: Arabian Sea; country: Oman; verbatimDepth: 13.5 m; decimalLatitude: 19.3767; decimalLongitude: 57.8833; Event: eventDate: 02-11-1933 -11-02; year: 1933; month: 11; day: 2; Record Level: language: English; institutionID: BMNH; collectionID: BMNH; datasetID: BMNH 1937.9.2.156; collectionCode: Invertebrates; datasetName: BMNH

Description

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. 1 A). 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. 1 A). 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. 1 A). Left lateral antenna inserted on anterior margin of prostomium, longer than prostomium with 7 articles of different sizes in irregular arrangement (Fig. 1 A). Peristomium shorter than subsequent segments, folding on posterior part of prostomium (Fig. 1 A). 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. 1 B). Base of bulbous cirri thin, enlarged medium part and a small unarticulated knob at the end (Fig. 1 B-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. 1 F-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).

Diagnosis

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.

Distribution

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).

Taxon discussion

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. 1 B-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. 6 A), 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. 2 B-C and Fig. 4 C-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.

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. 1 C-D).

Figures

Figure 1. Parasphaerosyllis indica Monro, 1937 (holotype BMNH 1937.9.2.156.). 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 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 6. Digital photographs of Parasphaerosyllis malimalii Capa, San Martin and Lopez, 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.