Halosydna parva Kinberg, 1856

Valencia-Soto, David, 2021, Scale-bearing beauty: Intertidal scale-worms (Polychaeta: Polynoidae) from Punta Blanca (Arequipa, Peru), Zootaxa 5032 (2), pp. 151-194 : 167-176

Halosydna parva Kinberg, 1856

Figures 9–16

Halosydna parva Kinberg 1856: 385 .

Halosydna parva Hartman 1939: 33–34 . Pl. 21, Figs 265–267. 1949: 18–19. Figs Pl. 1, Figs. 5–9 .

Halosydna parva Salazar-Silva 2013: 36–39 . Figs 17–18 .

Material examined. MUSM Nº 4647, 1 specimen, complete, Punta Blanca , Arequipa, Peru, 15°27’39.36”S 75°2’2.98”W, Station 2A, coll. from rocky shore at low tide under rocks, 14 September 2019, by D. Valencia-Soto and D. Valencia-Valencia, pharynx dissected and dissolved for complete jaw examination . MUSM Nº 4648, 2 specimens, same sampling data, pharynges dissected for jaw examination . MUSM Nº 4649 (a), 1 specimen, Punta Blanca , Arequipa, Peru, 15°27’39.36”S 75°2’2.98”W, Station 2C, same sampling data, pharynx dissected for jaw examination . MUSM Nº 4650, 2 specimens, Punta Blanca , Arequipa, Peru, 15°27’38.70”S 75°2’0.60”W, Station 3A, coll. from rocky shore at low tide under rocks, 14 September 2019, by D. Valencia-Soto and D. Valencia-Valencia, pharynges dissected for jaw examination . MUSM Nº 4665, 6 specimens, Punta Blanca , Arequipa, Peru, 15°27’38.70”S 75°2’0.60”W, Station 3C, same sampling data, pharynges dissected for jaw examination .

Four specimens ( MUSM Nº 4649b–e) fixed using absolute ethanol, for molecular studies.

Description. Based on specimen MUSM N° 4647. Individual 22.3 mm long (from tip of median antennae to tip of anal cirri) and 4.4 mm wide with chaetae (3.4 mm without chaetae). Body with 36 segments, short, slender, flattened dorsoventrally and rectangular in cross-section ( Fig. 9A–B ). Prostomium rounded, bilobed, broader than long, with three antennae antero-terminally ( Fig. 9C ). Median ceratophore stout, with dark pigment, placed in anterior notch of prostomium; lateral ceratophores as anterior projections of prostomium, with dark pigment and thinner than median ceratophore ( Fig. 9C ). Ceratostyles of all antennae with subdistal swellings and filiform tips; lateral ceratostyles shorter than median ceratostyle ( Fig. 9C ). Two pairs of dark eyes placed dorsolaterally: anterior pair slightly anterior to widest part of prostomium and posterior pair on posterior part of prostomium ( Fig. 9C ). One of two palps present, conical, smooth, with subdistal swelling and filiform tip ( Fig. 9C ). Facial tubercle rounded, with dark pigmentation.

Tentaculophores lateral to prostomium, cylindrical with two chaetae each. Tentacular cirri resemble median ceratostyle ( Fig. 9C ). Dorsal tentacular cirri longer than ventral tentacular cirri. Buccal segment with pair of inconspicuous rounded nuchal nodules; nuchal fold absent ( Fig. 9C ). Buccal cirri with same appearance of lateral antennae. Dark-pigmented bands present at base and near subdistal swelling of ceratostyles, tentacular and buccal cirri. Dorsal cirri with similar appearance of tentacular cirri ( Fig. 9A–B ). Dorsal tubercles nodular, inconspicuous ( Fig. 9A ). Dorsum with dark-pigmented transverse bands on posterior region of each segment ( Fig. 9A ).

Parapodia with small, somewhat conical notopodia placed anteriorly (except for first parapodium, where notopodium is placed posterior to neuropodium) ( Fig. 10A–D ), with indistinct chaetal lobes. Well-developed neuropodia not deeply incised dorsally and ventrally, with indistinct chaetal lobes; prechaetal lobe distally truncate, with small rounded lobe over tip of acicula; postchaetal lobe distally truncate, with similar length (except for first parapodium, where both chaetal lobes are somewhat concave distally) ( Fig. 10A–D ). Neuropodial supra-acicular process and terminal papilla absent. Both rami with aciculae penetrating epidermis ( Fig. 10A–D ). Ventral cirri of anterior parapodia slightly longer than those present in parapodia of median region of the body, with bulbous bases, filiform tips and smooth surfaces ( Fig. 10A–D ). Nephridial papillae present from 8 th segment, with blunt tips.

Notochaetae arranged in short bundles, with numerous transverse rows of spines: blunt-tipped notochaetae ( Fig. 10E ), in superior position and capillary notochaetae ( Fig. 10F ), in inferior position. Notochaetae become longer from superior to inferior positions. Neurochaetae stouter than notochaetae, falcate, subdistally thickened, with subdistal rows of spines; rows of spines larger distally than basally. First parapodium with entire-tipped neurochaetae ( Fig. 10G–H ); remaining parapodia with bidentate neurochaetae ( Fig. 10I–N ). Pygidium with two anal cirri ( Fig. 9B ).

Eighteen pairs of elytra on segments 2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 28, 30, 31, 33; covering all the body, leaving neurochaetae and dorsal cirri exposed. Last three segments non-elytrigerous, covered by last pair of elytra. First pair of elytra slightly rounded ( Fig. 12A ), second pair reniform ( Fig. 12B ), median and posterior slightly oval ( Figs 13 , 14A–B ) and last pair triangular ( Fig. 14C ). All elytra provided with marginal fringe of papillae commonly arranged on AI and AIII, white margins mainly present on AI and AII and a white spot over the elytrophore scar ( Figs 12–14 ). Remaining surfaces randomly mottled with white and dark spots ( Figs 12–14 ). Elytrophore scars oval.

All elytral surfaces are covered by rounded translucent papillae (seen from above) with narrow bases, sometimes provided with a short filiform tip ( Fig. 11E, J ), mainly on AI and AIII ( Fig. 12–14 ) and four kinds of hardwalled tubercles: (a) conical microtubercles with swollen, wrinkled tips, sometimes bifid (slightly quadrangular when seen from above) ( Fig. 11A, G ) mainly on AI, some on AII and AIII ( Figs 12–14 ); (b) conical macrotubercles with smooth and rugose tips, some with wide internal concavities ( Fig. 11B, C, H ), mainly on AI, AIII and AIV ( Figs 12–14 ); (c) truncate microtubercles ( Fig. 11D, I ) on AII, AIII and AIV ( Figs 12–14 ) and (d) flattened microtubercles ( Fig. 11F, K ) on AIII and AIV ( Figs 12–14 ). Tubercle morphology (both macro- and micro-) changes gradually depending on location, giving rise to transitional forms between zones where each tubercle type predominates.

Like shape, dimensions of both macro- and microtubercles change gradually over the elytral surface depending on location. Except for first pair of elytra, macro- and microtubercles located on AI and AIII are taller than those present on AII and AIV while macro- and microtubercles bases are slightly wider when located on AII, AIV and part of AIII. Both height and width of all macro- and microtubercles decrease gradually from anterior to posterior pairs of elytra; however, dimensions of conical macrotubercles vary regardless of this pattern ( Fig. 15 ). The translucent rounded papillae (the smallest elytral ornamentation) tend to vary in width; however, a pattern between their location over the elytral surface and their width was not observable.

Pharynx with nine pairs of anterior terminal papillae ( Fig. 16A ). Two pairs of reddish, chitinous, hollow and asymmetric jaws, posterior to papillae ( Fig. 16B–C ). Longer fangs present in dorsal right jaw and ventral left jaw ( Fig. 16B–C ). Denticles absent from jaws ( Fig. 16 ).

Variation. Collected individuals have 36 body segments and range between 13.6–22.3 mm long and 3.1–5 mm wide (including chaetae). Of all 12 examined specimens, only 3 were ovigerous. Minimum size for ovigerous specimens was 13.6 mm long; however, longer non-ovigerous individuals were observed. Significant morphological differences between non-ovigerous and ovigerous individuals were not observed.

Individuals exhibit some intraspecific variability such as: (1) a short, triangular acicular lobe in neuropodia; (2) distinct degrees of development of both neuropodial lobes and nuchal nodules and (3) presence of an inconspicuous nuchal fold. These variations could not be correlated to size since these were present regardless of this parameter.

Elytral asymmetry, which could be caused by damage/loss and replacement of elytra (A. Murray, pers. comm.), was observed in all examined individuals as well. It was restricted to the conical macrotubercles, especially those with wide internal concavities. Elytral asymmetry is here classified in three categories: (a) according to their presence (i.e., right elytron may have them while the left elytron not and vice versa); (b) according to their dimensions (i.e., height and width of conical macrotubercles can vary between left and right elytra of a single pair) and (c) according to their number (i.e., right elytron may have several conical macrotubercles while the left elytron only one, two or a few and vice versa).All elytral asymmetry categories can be present in any elytral pair, even simultaneously (except for the first kind).

Complete absence of conical macrotubercles with wide internal concavities in a whole, single pair of elytra (i.e., both left and right elytra) was observed as well, in the first pair of elytra of specimen MUSM N° 4648b. Furthermore, some individuals exhibited corrugated elytral surfaces with conspicuous elytral ornamentations (i.e. taller and wider than other specimens) but their morphology and distribution over the elytral surface remained the same.

Remarks. The specimens agree with descriptions by Hartman (1949) and Salazar-Silva (2013) based on type material of Halosydna parva Kinberg, 1856 . However, some details should be highlighted. Hartman (1949) reexamined the type specimens of Halosydna parva Kinberg, 1856 and stated this species had elytra with marginal papillae (absent in larger individuals), “large, low, chitinous cones on the posterior half of the surface” in the first twelve pairs of elytra, “minute pickles” in the remaining elytra (or smooth) and bidentate neurochaetae. Later, Salazar-Silva (2013) designated a lectotype and pointed out this species had elytra with marginal papillae (but absent in posterior ones), conical microtubercles, distally rounded macrotubercles (but absent in the first pair of elytra) and bidentate neurochaetae.

Both descriptions have some differences regarding elytral characters but these may be explained. According to Salazar-Silva (2013), the lectotype is in poor condition so absence of marginal papillae in posterior pairs of elytra may be an artifact due to poor procedures of preservation and age of the individual (A. Murray, pers. comm.). This could also be the case for larger individuals without marginal papillae referred by Hartman (1949). On the other hand, absence of conical macrotubercles in the first pair of elytra described by Salazar-Silva (2013) agrees with the elytral asymmetry recorded for the individuals herein examined. Comparison between Halosydna parva Kinberg, 1856 and other Halosydna species recorded for the Pacific Coast of South America can be found in Table 4.

Distribution. The type locality is Chincha Islands, Peru ( Kinberg 1856). Also recorded for Cañete ( Tasso et al. 2018), Lima ( Paredes et al. 1999) and Independencia Bay ( Hartman 1939), Peru; Ecuador (La Plata Island; Albemarle Island, Galapagos) ( Hartman 1939). Herein, Halosydna parva is newly recorded for Punta Blanca, Arequipa, Peru.

Ecology. Halosydna parva Kinberg, 1856 has been recorded inhabiting a range of hard bottom environments at depths between 0–22 m, in intertidal environments and coral ( Hartman 1939, Tasso et al. 2018; Paredes et al. 1999). Herein, individuals of Halosydna parva Kinberg, 1856 were found alone or accompanied by specimens of the same species. As far as was observed, neither Lepidonotus aff. crosslandi peruana Hartmann-Schröder, 1962 and Harmothoe aff. hirsuta Johnson, 1897 shared the same habitat (i.e. inferior surfaces of rocks) with Halosydna parva Kinberg, 1856 .

tized” is the description attributed to that author and means “hard-walled”.

Figures

FIGURE 5. Elytral ornamentations of Lepidonotus aff. crosslandi peruana Hartmann-Schröder, 1962 (specimen MUSM Nº 4590).A) Conical microtubercles with bifid, wrinkled tips (seen from above) from AI; B) Same, details of the tips; C) Truncate microtubercles from AII; D) Flattened, hemispherical microtubercles from AIV; E) Variation of the former, without internal canals. Illustration of each ornamentation type and designation of symbols. F) Translucent rounded papillae as tiny black circles; G) Conical microtubercles with bifid, wrinkled tips as red circles; H) Truncate microtubercles as green circles; I) Flattened, hemispherical microtubercles as yellow circles. Scale bars: 40 µm.Abbreviations: pp, translucent rounded papillae; bwt, micro-

FIGURE 6. Anterior elytra of Lepidonotus aff. crosslandi peruana Hartmann-Schröder, 1962 (specimen MUSM Nº 4590) with their respective illustration of ornamentation distribution.A) 1st right elytron; B) 2nd right elytron; C) 3rd right elytron. Scale bars: A–C) 1 mm.

FIGURE 7. Posterior elytra of Lepidonotus aff. crosslandi peruana Hartmann-Schröder, 1962 (specimen MUSM Nº 4590) with their respective illustration of ornamentation distribution. A) 10th right elytron; B) 11th right elytron; C) 12th right elytron. Scale bars: A–C) 1 mm.

FIGURE 8. Pharynx and jaws of Lepidonotus aff. crosslandi peruana Hartmann-Schröder, 1962. A) Frontal view of pharynx. B) Dorsal jaws seen from the pharyngeal lumen. C) Ventral jaws seen from the pharyngeal lumen. Scale bars: A) 1 mm; B–C) 400 µm.

FIGURE 9. Halosydna parva Kinberg, 1856. A) Dorsal view of specimen MUSM Nº 4647 after elytra detachment; B) Dorsal view of specimen MUSM Nº 4648b; C) Prostomium of specimen MUSM Nº 4647. Scale bars: A–B) 5 mm; C) 1 mm.

FIGURE 10. Parapodia and chaetae of Halosydna parva Kinberg, 1856 (Specimen MUSM Nº 4647). A) 1st parapodium; B) 2nd parapodium; C) 3rd parapodium; D) 18th parapodium; E) Superior notochaeta; F) Inferior notochaeta; G–H) Entire-tipped neurochaetae from the 1st parapodium; I) Superior neurochaeta from the 2nd parapodium; J) Inferior neurochaeta from the 2nd parapodium; K) Superior neurochaeta from the 3rd parapodium; L) Inferior neurochaeta from the 3rd parapodium; M) Superior neurochaeta from the 18th parapodium; N) Inferior neurochaeta from the 18th parapodium. Scale bars: A–D) 500 µm; E–N) 50 µm.

FIGURE 11. Elytral ornamentations of Halosydna parva Kinberg, 1856 (Specimen MUSM Nº 4647). A) Conical microtubercles with swollen, wrinkled, bifid tips (arrows); B) Conical macrotubercles with wrinkled tips; C) Same, with wide internal concavities (arrows); D) Truncate microtubercles; E) Rounded papillae with narrow bases (arrows); F) Flattened microtubercles (arrows). Illustration of ornamentations and designation of symbols. G) Conical microtubercles with swollen, wrinkled, bifid tips as green circles; H) Conical macrotubercles with narrow and wide internal concavities as red circles; I) Truncate microtubercles as blue circles; (J) Rounded papillae with narrow bases as black tiny circles; K) Flattened microtubercles as yellow circles. Scale bars: 20 µm.

FIGURE 12. Anterior elytra of Halosydna parva Kinberg, 1856 (Specimen MUSM Nº 4647) with their respective illustration of ornamentation distribution.A) 1st right elytron; B) 2nd right elytron; C) 3rd right elytron. Scale bars: A–C) 1 mm.

FIGURE 13. Median elytra of Halosydna parva Kinberg, 1856 (Specimen MUSM Nº 4647) with their respective illustration of ornamentation distribution. A) 9th right elytron; B) 10th right elytron; C) 11th right elytron. Scale bars: A–C) 1 mm.

FIGURE 14. Posterior elytra of Halosydna parva Kinberg, 1856 (Specimen MUSM Nº 4647) with their respective illustration of ornamentation distribution.A) 16th right elytron; B) 17th right elytron; C) 18th right elytron. Scale bars: A–C) 1 mm.

FIGURE 15. Distinct degrees of development of conical macrotubercles (arrows) in Halosydna parva Kinberg, 1856 (specimen MUSM Nº 4648b). A–B) 3rd pair of elytra; C–D) 16th pair of elytra; E–F) 18th pair of elytra. Scale bars: 40 µm.

FIGURE 16. Pharynx and jaws of Halosydna parva Kinberg, 1856. A) Pharyngeal papillae and jaws. B) Dorsal jaws seen from the pharyngeal lumen. C) Ventral jaws seen from the pharyngeal lumen. Scale bars: A) 1 mm; B–C) 200 µm. Arrows shows broken regions caused by accidental handling.

FIGURE 17. Harmothoe aff. hirsuta Johnson, 1897. A) Dorsal view of specimen MUSM Nº 4633 prior detachment of elytra; B) Same, after elytra detachment; C) Same, prostomium. Scale bars: A–B) 5 mm; C) 1 mm.

FIGURE 18. Parapodia and chaetae of Harmothoe aff. hirsuta Johnson, 1897 (Specimen MUSM Nº 4633). A) 1st parapodium; B) 2nd parapodium; C) 17th parapodium; D) Superior notochaeta; E) Inferior notochaeta; F) Neurochaeta of the 1st parapodium; G) Superior neurochaeta of the 2nd parapodium; H) Inferior neurochaeta of the 2nd parapodium; I) Superior neurochaeta of the 17th parapodium; J) Inferior neurochaeta of the 17th parapodium. Scale bars: A–C) 1 mm; D–J) 20 µm.