Research Article |
Corresponding author: Sergio I. Salazar-Vallejo ( savs551216@hotmail.com ) Academic editor: Christopher Glasby
© 2015 Sergio I. Salazar-Vallejo, Norma Emilia González, Patricia Salazar-Silva.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Salazar-Vallejo SI, González NE, Salazar-Silva P (2015) Lepidasthenia loboi sp. n. from Puerto Madryn, Argentina (Polychaeta, Polynoidae). ZooKeys 546: 21-37. https://doi.org/10.3897/zookeys.546.6175
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Among polychaetes, polynoids have the highest number of symbiotic species found living with a wide variety of marine invertebrates, including other polychaetes. Lepidasthenia Malmgren, 1867 and Lepidametria Webster, 1879 were regarded as synonyms but belong to different subfamilies, although both have species associated with thelepodid or terebellid polychaetes. In this contribution Lepidasthenia loboi sp. n. is described from several specimens associated with the thelepodid Thelepus antarcticus Kinberg, 1867, collected on a rocky shore near Puerto Madryn, Argentina. Lepidasthenia loboi sp. n. can be confused with L. esbelta Amaral & Nonato, 1982 because both live with Thelepus, are of similar sizes with similar pigmentation patterns, and have giant neurochaetae. However, in L. loboi sp. n. all eyes are of the same size, cephalic and parapodial cirri are tapered and mucronate, the second pair of elytra is larger than the third, the ventral cirri arise at the base of parapodia such that they do not reach chaetal lobe tips, and neuraciculae are tapered. On the contrary, in L. esbelta the posterior eyes are larger than anterior ones, cephalic and parapodial appendages are swollen subdistally, the second and third pairs of elytra are of the same size, the ventral cirri arise medially such that their tips reach the neurochaetal lobe tips, and the neuraciculae have falcate tips. Some comments about other genera in the Lepidastheniinae, a simplified key to its genera, and a key to Lepidasthenia species with giant neurochaetae are also included.
Thelepodidae , Terebellidae , Lepidametria , symbiosis, giant chaetae, Lepidastheniinae
The polychaete family Polynoidae has the highest number of species involved in symbiotic relationships (
There are few detailed studies on the relationships between polynoids, and their thelepodid or terebellid hosts. From a physiological perspective,
There are no world-wide keys to species of Lepidasthenia Malmgren, 1867 or Lepidametria Webster, 1879. There are some keys available (
Some authors have dealt with the delineation of what we now regard as Lepidastheniinae, either by making direct comments on some morphological attributes or by indirect indications of their relevance by including them in keys. Their ideas, especially when they are convergent, are followed in the following sections, especially those made by
In this contribution, Lepidasthenia loboi sp. n. is described from specimens collected on a rocky shore nearby Puerto Madryn, Argentina, associated with the thelepodid Thelepus antarcticus Kinberg, 1867. Remarks on other genera in the Lepidastheniinae, together with some others about morphology, a simplified key to lepidastheniin genera, and a key to Lepidasthenia species with giant neurochaetae are also included.
Field sampling. Cerro Avanzado is a large coastal mountain nearby Puerto Madryn, Argentina, and the same name applies to the nearby shore. There, a long sandy beach is bordered by rocky outgroups; rocks are mudstones which are easily bored through or broken apart. A hammer was used to crack apart larger rocks into fist-sized portions which were brought to the Centro Nacional Patagónico (CENPAT) facilities where specimens were removed from these fragments. Polychaetes were placed in tap water to relax them, then fixed in a 10% formalin solution. After 24 h they were rinsed with tap water and were preserved in 70% ethanol.
Specimens. Polynoids, thelepodids and terebellids were identified at
Type specimens deposition. Type and non-type specimens were deposited in the following institutions:
Restrictions for keys. There is one key to Lepidastheniinae genera available (
Body. The number of chaetigers can be useful but because this number changes as the animals grow, and their bodies are delicate and fragment easily, this cannot be a diagnostic feature. Likewise, pigmentation and its intensity might be size-dependent as well and vary according to how long specimens have been stored in alcohol. However, there are some interesting differences regarding pigmentation patterns involving a series of pigmented segments, their number, and the relative shape of segmental bands, although growth abnormalities or regeneration might slightly alter these patterns.
Prostomium. The shape and relative length of antennae are useful diagnostic features; antennae can be tapered or subdistally swollen. The relative size of eyes, being either of about the same size, or one pair markedly larger than the other, together with their position on the prostomial surface (variable in relation to lateral margins) are also useful. The relative length of antennae has not been used but could help to separate similar species, with caution as they can sometimes be lost or undergoing regeneration, such that observations on more than a single specimen are desirable.
First chaetiger. Some species have an anterior projection over the prostomium, and its surface and margins can be papillated or smooth. Further, in Lepidametria species there are notochaetae in the tentaculophore.
Parapodia. Parapodial cirri can be basally swollen, tapered or subdistally swollen, and the relative length and width of cirrophores versus cirrostyles are relevant as well. It is useful to note the relative size of dorsal and ventral cirri to each other, and to the tip of neurochaetal lobes. Parapodial surfaces are usually smooth in Lepidasthenia, often papillated in Lepidametria, and rugose, or markedly folded in Perolepis. The presence of parapodial papillae is used to group similar polynoid genera (
Elytra. The body can have elytra along its length, or only through to medial chaetigers (Branchipolynoe). For those having elytra along the body, their relative size as an indication of how much of dorsum is covered, or if they abut successive or other elytra along the middorsal line, are diagnostic features. In general, most elytra of Lepidasthenia are small, often markedly reduced from chaetigers 2–3, whereas in Lepidametria they can be of about the same size along the body, either touching along the middorsal line, or leaving a wide dorsal area uncovered. In the posterior region the elytra and cirri can be alternating, or elytra can be present on every three segments. Elytral pigmentation patterns are also useful since it can be solid or homogeneous, black, grayish or pale, have a pigmented spot near the junction or insertion region, or form a band from the insertion region.
Chaetae. Notochaetae are present in many Lepidametria species, at least along anterior chaetigers, but never present in Lepidasthenia species. Neurochaetae of different shapes and relative width are present in Lepidasthenia, although they are usually of decreasing length from the superior to the inferior most. They can be finely dentate with a single series of marginal teeth, or more frequently provided with a series of paired rounded stiff blades, each blade with finely denticulate margins, as originally indicated by
(incl. Nectochaeta von Marenzeller, 1892, Harmopsides Chamberlin, 1919, and Bouchiria Wesenberg-Lund, 1949).
Lepidametria commensalis Webster, 1879, by monotypy.
(modif.
Lepidasthenia and Lepidametria were regarded as synonyms by
The pattern of the presence of elytra on posterior segments in Lepidametria and Lepidasthenia made
It is unfortunate that there is no redescription for the type species of Lepidametria. The only illustrations available do not show this lepidastheniin notch; however, one figure shows that their neuropodia are not short (
Lepidasthenia Malmgren, 1867, by original designation.
(Modif.
1 | Body with elytrae continued through posterior segments; sometimes reduced in size in medial and posterior segments | 2 |
– | Body with elytra limited to anterior and medial regions | 10 |
2 | Notochaetae present | 3 |
– | Notochaetae absent; parapodial surface usually smooth | 4 |
3 | Lateral antennae with ceratophores as long as wide; dorsal cirri about three times longer than ventral ones (numerous segments, up to 90 pairs of elytra) | Lepidastheniella Monro, 1924 |
– | Lateral antennae with ceratophores twice as long as wide; dorsal cirri 6–7 times longer than ventral ones (reduced number of segments, 15 pairs of elytra) | Parahalosydna Horst, 1915 |
4 | Elytra alternate with cirri in medial and posterior regions | 5 |
– | Elytra present every third segment in medial and posterior regions | 7 |
5 | First chaetiger with a middorsal anterior projection over prostomium; neurochaetae unidentate with two subdistal teeth; elytra smooth | Showapolynoe Imajima, 1997 |
– | First chaetiger without anterior projection; elytra with microtubercles | 6 |
6 | Neurochaetae mostly bidentate with series of 10–20 lamellae; elytral microtubercles along exposed area | Hyperhalosydna Augener, 1922 |
– | Neurochaetae only unidentates with series of about 10 tiny lamellae; elytral microtubercles scattered | Benhamipolynoe Pettibone, 1970 (partim) |
7 | Elytrophores elongated, pedunculate; ventral cirri sometimes irregularly swollen | Perolepis Ehlers, 1908 |
– | Elytrophores short, not transformed into peduncles; ventral cirri tapered or subdistally swollen | 8 |
8 | Medial segments with large elytra, overlapping successive ones or approaching middorsally | 9 |
– | Medial segments with tiny, non-overlapping elytra | Lepidasthenia Malmgren, 1867 |
9 | Eyes small, on prostomial upper surface; ventral parapodial surface papillate; all neurochaetae of a single type, with about 20 series of lamellae | Telolepidasthenia Pettibone, 1970 |
– | Eyes large, on prostomial margins; ventral parapodial surface smooth; neurochaetae of three types: lamellate, denticulate and smooth | Alentiana Hartman, 1942 |
10 | Notochaetae present; parapodial surface smooth; neurochaetae with rows of large lamellae | Pseudopolynoe Day, 1962 |
– | Notochaetae absent; parapodial surface rugose; neurochaetae with rows of tiny lamellae | Benhamipolynoe Pettibone, 1970 (partim) |
Polynoe elegans Grube, 1840, by monotypy.
(modif.
There was some confusion regarding the presence of notochaetae, but in the original diagnosis for Lepidasthenia,
It must be emphasized that what can be regarded as the Lepidasthenia elytra-cirri pattern in the posterior region is shared by Perolepis and Telolepidasthenia. However, in Perolepis species the integument is usually rugose, and at least the first elytrophores are hypertrophied into distinct peduncles or stems, whereas in Lepidasthenia the integument is smooth and all elytrophores are reduced. Furthermore, in Telolepidasthenia elytrae are large, covering most of the dorsum, and all neurochaetae are unidentate, whereas in Lepidasthenia only the first elytra are large enough to touch each other and the remaining ones are reduced exposing the dorsum, and the dentition of the neurochaetal tips is variable.
Lepidasthenia esbelta:
Southwestern Atlantic, Argentina. Cerro Avanzado, 16 km southward from Puerto Madryn (42°49'S, 65°04'W), Golfo Nuevo. Holotype (
Southwestern Atlantic, Argentina. One specimen (
Holotype (
Lepidasthenia loboi sp. n., holotype (
Prostomium with eyes black, medium-sized (as wide as antennal width), central on prostomium; anterior eyes more separated than posterior ones (Fig.
Lepidasthenia loboi sp. n. A Paratype (
Elytra on segments 2, 4, 5, alternating with dorsal cirri to chaetiger 26, thereafter on every three segments but last 7 segments more irregular. First pair of elytra largest, covering prostomium and middorsal region, grayish, slightly darker around junction area, laterally with a paler, thin area. Second pair of elytra blackish, oval, less than half as large as first elytra, slightly overlapping anterior elytra, not covering middorsal region, laterally with a paler, thin area. Third pair of elytra blackish, subcircular, less than half as large as second elytra, non-overlapping with previous elytra, not covering middorsal region. Following elytra with same pigmentation, progressively reducing in size, up to chaetiger 20, about twice as large as junction area.
Parapodia sub-biramous throughout body. Notopodia reduced to a projecting, digitate lobe, reducing in size posteriorly. Neuropodia projecting lobes throughout body, neurochaetal lobes truncate or rounded. Dorsal cirri with cirrophores blackish, about as long as wide, cirrostyles tapered, with long tips, longer anteriorly, slightly reducing in length and pigmentation posteriorly, about twice as long as neuropodium. Ventral cirri small, tapered, basal-half blackish, tips mucronate, arising at base of parapodia, about as long as half neuropodial length.
Notopodia without notochaetae. Neurochaetae of different size and shape. Anterior chaetigers with about 15 neurochaetae per bundle, of similar width, smaller ventrally, each with bidentate tips, accessory tooth smaller, directed distally, and 10 or more series of subdistal lamellae (Fig.
Posterior region tapered; pygidium truncate, anus dorsal. Nephridial papillae from chaetiger 9; anterior region with papillae pale, smaller along anterior body half, progressively larger and darker in posterior body half.
Pharynx (observed in some paratypes) with marginal prismatic papillae, upper ones larger, 9 upper and 9 lower. Two pairs of dark brown jaws.
This species name honors the late José María Orensanz, in recognition of his many contributions to the study of Southwestern Atlantic and Antarctic polychaetes, of his continued support of our research dreams, and for his participation in the field trip that collected the species. The specific epithet is derived from his nickname, Lobo, and is a noun in apposition.
Cerro Avanzado rocky shore, intertidal, Puerto Madryn (42°49'S, 65°04'W), Golfo Nuevo, Argentina.
Paratypes 12–64 mm long, 2–6 mm wide, 37–99 chaetigers. Smallest specimen with transverse bands restricted to anterior region; larger specimens more heavily pigmented and showing variation in the amount of spots or darkening of paler areas between successive transverse bands. Intensity of pigmentation increased in larger specimens, and in some (including holotype), posterior region had an irregular pattern probably due to imperfect regeneration, which is rather uncommon in other errant polychaetes (
Lepidasthenia loboi sp. n. has been confused with L. esbelta Amaral & Nonato, 1982, described from southern Brazil because both live with Thelepus, have similar size and pigmentation patterns, and giant neurochaetae. However, they differ in several diagnostic features such as the size of eyes, the type of cephalic and parapodial appendages, size of anterior elytra, topology of parapodial cirri, and tips of neuraciculae. In L. loboi sp. n. eyes are of the same size, cephalic and parapodial cirri have long tapered tips, second pair of elytra is larger than third, ventral cirri arise basally to neuropodia such that they do not reach the tips of the chaetal lobe, and neuraciculae are tapered. On the contrary, in L. esbelta posterior eyes are larger than the anterior ones, cephalic and parapodial appendages are subdistally swollen, the second and third pairs of elytra are of the same size, ventral cirri are medially placed such that their tips reach the tips of the neurochaetal lobe, and the neuroaciculae have falcate tips.
Another species has been recorded from Brazil by
First, L. virens was described briefly with material from Calbuco (41°46'S, 73°08'W), Chiloé, Chile. The description and illustration indicates that elytra are large enough to touch each other along the body but while leaving the middorsal surface uncovered (
Second,
Thelepus antarcticus Kinberg, 1867 builds its tubes with a mucoid protein forming a semi-transparent matrix with attached fragments of shells or other calcareous fragments. Tubes run inside rock crevices or fractures and are difficult to track individually because they break when the rock is fragmented. There were 34 T. antarcticus specimens plus six belonging to two other terebellid species, making it the most frequent thelepodid (or terebellid) in the rocky intertidal environment. About half of L. loboi specimens remained inside Thelepus tubes, whereas the others left the tubes as the rock was broken. In total, there were 19 L. loboi specimens taken at Cerro Avanzado, and there were polynoids in only one-third of the Thelepus tubes, half the rate of association between T. crispus and H. brevisetosa found by
The specimens were found in two localities in two southern Argentina Gulfs: Cerro Avanzado, Puerto Madryn, Golfo Nuevo, and San Antonio Oeste, Golfo San Matías, but might co-occur with Thelepus antarcticus throughout its distribution.
1 | Anterior eyes larger than posterior ones | 2 |
– | Anterior eyes smaller or subequal to posterior ones | 3 |
2 | Dorsal cirri subdistally swollen; ventral cirri digitate | L. elegans (Grube, 1840), Mediterranean Sea |
– | Dorsal cirri tapered; ventral cirri basally swollen, tapered | L. ornata Treadwell, 1937, Western Mexico* |
3 | Dorsal cirri subdistally swollen; ventral cirri tapered, surpassing neurochaetal lobe tip; neuroaciculae falcate | L. esbelta Amaral & Nonato, 1982, Brazil |
– | Dorsal and ventral cirri tapered, ventral cirri short, not reaching neurochaetal lobe tip; neuraciculae tapered, straight | L. loboi sp. n., Patagonia |
* A junior synonym of L. virens (Blanchard in Gay, 1849) fide
Emilia and Sergio wholeheartedly thank Ana Parma and the late Lobo Orensanz for housing us during one month in The Monster. Conversations and meals were wonderful, especially because we had the best wine in the world: the one shared with good friends. Leslie Harris, Pat Hutchings, Ruth Barnich and Chris Glasby carefully read an earlier draft and made many recommendations helping us improve this current version. Marcelo Fukuda (