Lepidonotus aff. crosslandi, Monro, 1928

Valencia-Soto, David, 2021, Scale-bearing beauty: Intertidal scale-worms (Polychaeta: Polynoidae) from Punta Blanca (Arequipa, Peru), Zootaxa 5032 (2), pp. 151-194 : 155-166

Lepidonotus aff. crosslandi peruana Hartmann-Schröder, 1962

Figures 3–8

Lepidonotus sp. Valencia 2020: 23–29 , Figs 8–13 .

Material examined. MUSM Nº 4590, 1 specimen, complete, Punta Blanca , Arequipa, Peru, 15°27’38.70”S 75°2’0.60”W, Station 3B, 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 jaw complete examination . MUSM Nº 4591, 6 specimens, same sampling data, specimens with non-everted pharynges dissected for superficial jaw examination . MUSM Nº 4635, 5 specimens, Punta Blanca , Arequipa, Peru, 15°27’37.46”S 75°2’12.24”W, Station 1A, coll. from rocky shore at low tide under rocks in water canals, 14 September 2019, by D. Valencia-Soto and D. Valencia- Valencia, specimens with non-everted pharynges dissected for superficial jaw examination . MUSM Nº 4636, 2 specimens, Punta Blanca , Arequipa, Peru, 15°27’37.46”S 75°2’12.24”W, Station 1B, same sampling data and procedure . MUSM Nº 4637, 1 specimen, 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, dissected for superficial jaw examination . MUSM Nº 4638, 2 specimens, Punta Blanca , Arequipa, Peru, 15°27’39.36”S 75°2’2.98”W, Station 2B, same sampling data and procedure . MUSM N° 4639 (a), 1 specimen, Punta Blanca , Arequipa, Peru, 15°27’39.36”S 75°2’2.98”W, Station 2C, same sampling data and procedure . MUSM Nº 4640, 9 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, specimens with non-everted pharynges dissected for superficial jaw examination . MUSM Nº 4641, 7 specimens, Punta Blanca , Arequipa, Peru, 15°27’38.70”S 75°2’0.60”W, Station 3C, same sampling data and procedure .

Four specimens ( MUSM N° 4639b–d) fixed with absolute ethanol, for molecular studies.

Description. Based on specimen MUSM Nº 4590. Individual 17.9 mm long (from tip of median antennae to tip of anal cirri) and 4.9 mm wide with chaetae (4.3 mm without chaetae). Body with 26 segments, short, flattened dorsoventrally, rectangular in cross-section ( Fig. 3A–B ). Prostomium rounded, bilobed, as long as wide, with three antennae placed antero-terminally ( Fig. 3C ). Median ceratophore stout, placed in anterior notch of the prostomium and lateral ceratophores slightly thinner, as anterior projections of the prostomium ( Fig. 3C ). Ceratostyles of all antennae with subdistal swellings and filiform tips: lateral ceratostyles shorter than median ceratostyle. Brownish pigmented bands present at base of all ceratostyles and median ceratophore. 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. 3C ). One pair of stout, conical, smooth palps with abrupt, tapering tips ( Fig. 3C ) and narrow dark pigmented bands along 2/3 of their length. Facial tubercle rounded, with faint dark pigmentation.

Tentaculophores lateral to prostomium, cylindrical with one chaeta each. Tentacular cirri with same appearance as median ceratostyle: with subdistal swelling, filiform tips and dark-pigmented bases. Dorsal and ventral tentacular cirri of similar length. Buccal segment with pair of rounded, nuchal nodules; nuchal fold absent ( Fig. 3C ). Buccal cirri with same appearance of antennae and tentacular cirri but unpigmented. Dorsal cirri with similar appearance of antennae and tentacular cirri, with remnants of pigmented bands ( Fig. 3A–B ). Dorsal tubercles nodular ( Fig. 3B ).

Parapodia with small, somewhat conical notopodia placed anteriorly ( Fig. 4A–C ), with indistinct chaetal lobes. Well-developed neuropodia not deeply incised dorsally and ventrally; prechaetal lobe with subtriangular acicular lobe and postchaetal lobe slightly shorter, distally subtriangular. Neuropodial supra-acicular process and terminal papilla absent ( Fig. 4A–C ). Both rami with aciculae penetrating epidermis ( Fig. 4A–C ). Ventral cirri long in anterior parapodia and shorter in parapodia of the median region of the body, with bulbous bases, filiform tips and smooth surfaces ( Fig. 4A–C ). Nephridial papillae present from 7 th segment, with blunt ends.

Notochaetae arranged in short bundles, with numerous transverse rows of spines: blunt-tipped notochaetae ( Fig. 4D ), in superior and middle positions and capillary notochaetae ( Fig. 4E ), 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. Second parapodium with superior, long, bidentate neurochaetae ( Fig. 4F ) and inferior, shorter, entire-tipped neurochaetae ( Fig. 4G ); third parapodium with long superior, and shorter inferior, bidentate neurochaetae ( Fig. 4H–I ); parapodia from the middle part of the body with superior, long bidentate neurochaetae ( Fig. 4J ) and inferior, shorter entire-tipped neurochaetae ( Fig. 4K ). Pygidium with two anal cirri ( Fig. 3B ).

Twelve pairs of elytra on segments 2, 4, 5, 7, alternating to 23; usually 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. 6A ), second and third pairs, reniform ( Fig. 6B–C ) and remaining elytra, ovoid ( Fig. 7A–B ), except for last pair which are slightly triangular ( Fig. 7C ). All elytra brown with white margins, a characteristic white S-shaped spot ( Figs 3 , 6 ) and marginal fringe of papillae arranged on AI and AIII ( Figs 6 , 7 ). Elytrophore scars oval to reniform ( Fig. 6 , 7 ).

All elytral surfaces are covered by rounded translucent papillae (seen from above) ( Fig. 5B, E, F ) and three kinds of hard-walled microtubercles with rounded/oval bases and internal concavities: (a) conical microtubercles with slightly bifid, wrinkled tips (somewhat quadrangular when seen from above) ( Fig. 5A, B, G ) mainly on AI, some on margin of AII and AIII ( Figs 6 , 7 ); (b) truncate microtubercles ( Fig. 5C, H ) mainly on AI and AII, some on AIII and margin of AIV ( Figs 6 , 7 ) and (c) flattened, hemispherical microtubercles ( Fig. 5D, E, I ) mainly on AIII and AIV, some on AI and AII ( Figs 6 , 7 ). Microtubercle morphology changes gradually depending on location, giving rise to transitional forms between zones where each tubercle type predominates (i.e conical tubercles with truncate, wrinkled tips; flattened, slightly wrinkled tubercles and flattened, slightly truncate tubercles).

Like shape, dimensions of microtubercles change gradually over elytral surface depending on location. Except for first pair of elytra, tubercles located on AI and AIII are taller than those present on AII and AIV while tubercle bases are wider when located at AIII, AIV and part of AI. Both height and width of all microtubercle kinds decrease gradually from anterior to posterior pairs of elytra. Size of rounded translucent papillae remain unchanged regardless of location, being the smallest elytral ornamentation.

Pharynx with nine pairs of anterior terminal papillae ( Fig. 8A ). Two pairs of reddish, chitinous, hollow and asymmetric jaws ( Fig. 8B–C ), posterior to papillae. Longer fangs present in dorsal right jaw and ventral left jaw ( Fig. 8B–C ). Denticles absent from jaws ( Fig. 8 ).

Variation. Collected individuals have 26 body segments and range between 7.6–23.4 mm long and 1.9–6.8 mm wide (including chaetae). Of the 34 examined specimens, 13 were ovigerous. Minimum size for ovigerous specimens was 12.1 mm long; however, longer non-ovigerous individuals were observed. Significant morphological differences between non-ovigerous and ovigerous specimens were not observed

Specimens exhibit a few morphological variations: (1) intensity of elytral colour (usually anterior pairs are darker than posterior pairs); (2) length of the entire-tipped neurochaetae present in the second parapodia (usually these are shorter than the bidentate neurochaetae but some individuals have longer entire-tipped neurochaetae); (3) presence of a small notch near the tips of entire-tipped neurochaetae in the second parapodia (usually absent but few individuals, regardless of their length, exhibit it); (4) flattened, hemispherical microtubercles with nearly polygonal bases on AIV (usually rounded) and narrow —or lacking— internal concavities (see Fig. 5E ). None of the variations described above could be correlated to size since these were present regardless of this parameter.

Remarks. The resemblance between collected individuals and L. crosslandi peruana Hartmann-Schröder, 1962 is notable; however, they exhibit a few differences worth mentioning. Specimens differ from the nominal species mainly by the presence of bidentate-tipped neurochaetae in third parapodia, and jaws without denticles. Lack of denticles is persistent in all specimens examined, including individuals smaller than those examined by Hartmann- Schröder (1962a). Presence of some elytral ornamentations (i.e rounded translucent papillae, conical microtubercles with bifid wrinkled tips and truncate microtubercles) appears to be another difference between the two but due to the fact that elytral ornamentations of L. crosslandi peruana Hartmann-Schröder, 1962 were not originally described in detail (see Hartman 1939; Hartmann-Schröder 1962a), it would be necessary to examine the type specimen of L. crosslandi peruana Hartmann-Schröder, 1962 for an adequate assessment.

tubercles with bifid, wrinkled tips.

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Until such time as this is possible, individuals are here considered as a “toothless” variation of L. crosslandi peruana Hartmann-Schröder, 1962 . Comparison between Lepidonotus aff. crosslandi peruana Hartmann-Schröder, 1962 and other Lepidonotus species recorded for the Pacific Coast of South America can be found in Table 3.

Distribution. Lepidonotus aff. crosslandi peruana Hartmann-Schröder, 1962 is here recorded for Punta Blanca (Arequipa, Peru). Lepidonotus crosslandi peruana Hartmann-Schröder, 1962 has previously been recorded from Callao (type locality), Independencia Bay ( Hartman 1939, as Lepidonotus crosslandi Monro ), Cañete ( Tasso et al. 2018), Lima ( Paredes et al. 1999) and Pisco ( Paredes et al. 1988), Peru.

Ecology. Found along with individuals of Harmothoe aff. hirsuta Johnson, 1897 (described below). As far as was observed, specimens of both species did not exhibit aggressive behaviours to each other.

Figures

FIGURE 3. Lepidonotus aff. crosslandi peruana Hartmann-Schröder, 1962. A) Dorsal view of the body with elytra (specimen MUSM Nº 4591a); B) Dorsal view of the body, without elytra (specimen MUSM Nº 4590); C) Anterior region of specimen MUSM Nº 4590. Scale bars: A–B) 5mm; C) 1 mm.

FIGURE 4. Parapodia, notochaetae and neurochaetae of Lepidonotus aff. crosslandi peruana Hartmann-Schröder, 1962 (specimen MUSM Nº 4590). A) 2nd left parapodium; B) 3rd left parapodium; C) 13th left parapodium; D) Superior notochaeta; E) Inferior notochaeta; F) Superior neurochaeta from the 2nd left parapodium; G) Inferior neurochaeta from the 2nd left parapodium; H) Superior neurochaeta from the 3rd left parapodium; I) Inferior neurochaeta from the 3rd left parapodium; J) Superior neurochaeta from the 13th left parapodium; K) Inferior neurochaeta from the 13th left parapodium. Scale bars: A–C) 1 mm; D–K) 20 µm.

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.