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. 2019 Apr 10;14(4):e0214211.
doi: 10.1371/journal.pone.0214211. eCollection 2019.

Species delimitation in Amblyosyllis (Annelida, Syllidae)

María Teresa Aguado  1   2 , María Capa  3   4 , Domingo Lago-Barcia  5 , João Gil  6   7 , Fredrik Pleijel  8 , Arne Nygren  8   9
Affiliations

Species delimitation in Amblyosyllis (Annelida, Syllidae)

María Teresa Aguado et al. PLoS One. .

Abstract

Amblyosyllis is a worldwide distributed group of annelids mainly found in coastal environments. It is well known among the polychaete specialists mostly because of its notable beauty, showing bright colourful patterns and outstanding long and coiled appendices. Amblyosyllis is a monophyletic genus easy to identify due to its distinct diagnostic features; however, the species and their boundaries are, in most cases, not well defined. Herein, we provide an extensive sample of Amblyosyllis material (115 specimens) from several world geographic areas. We have studied the morphological features of each specimen and photographed them alive. Two mitochondrial DNA markers (COI and 16S) and one nuclear gene fragment (28S, D1 region) were sequenced. We performed phylogenetic analyses based on each DNA partition, as well as the combined data sets, obtaining congruent results. Species delimitation methods such as distance analyses, statistical parsimony networks and multi-rate Poisson tree processes were also applied. The combined results obtained from different methodologies and data sets are used to differentiate between, at least, 19 lineages compatible with the separately evolving meta-populations species concept. Four of these lineages are identified as nominal species, including the type species of Amblyosyllis, A. rhombeata. For three other lineages previously synonymized names are recovered, and seven lineages are described as new species. All of these species are described and supported by appropriate iconography. We recognize several morphological characters useful to identify species of Amblyosyllis, which in some cases should also be combined with molecular methods for species delineation. The genetic divergence in the genus is high, contrary to the morphological homogeneity observed. Two species show a wide geographical distribution, while the rest have a more restricted distribution. There are several examples of species with overlapping distribution patterns.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Amblyosyllis drawings from early polychaete literature.
(A) Amblyosyllis lineata, by McIntosh [7]. (B) Pterosyllis dorsigera, by Claparède [5]. (C) Nicotia lineolata, by Costa [6]. (D) Amblyosyllis speciosa, by Izuka [3].
Fig 2
Fig 2. Map with sampling localities.
Bioregions from Spalding et al. [79].
Fig 3
Fig 3. Invariable characters in Amblyosyllis.
Photo: Amblyosyllis clarae n. sp. MNCN 16.01/17994.
Fig 4
Fig 4. Interspecific variable characters in Amblyosyllis.
(A) Nuchal lappets. (B) Trepan. (C) Chaetae. (D) Chaetal teeth relative size. (E) Chaetal length. (F) Colour patterns.
Fig 5
Fig 5. Phylogenetic results and haplotypes.
On the left: Maximum Likelihood tree obtained when analysing the combined data set (COI+16S+28S). Bootstrap support values (B) above nodes. Lineages considered are those with support of 100 B and relative length of branch length. On the right: Haplotype networks from markers: COI (colours correspond to bioregions, see legend); 16S (blue) and 28S (black). Size of circles corresponds to sample size (see legend on figure). Each network represents congruent results after TCS analysis of each of the three markers. Red lines indicate different network incongruent results from at least one marker.
Fig 6
Fig 6. Summary of results obtained through different methodologies.
From the left to the right: phylogenetic analysis (ML tree from combined data set (COI+16S+28S)); morphology; distances; TCS; mPTP. On the right: taxonomic proposal and geographic localities of samples. White dots represent missing data. Bars in grey (morphogroups G, H and P) represent variability regarding some of the selected morphological characters to differentiate morphospecies.
Fig 7
Fig 7. Amblyosyllis antoni n. sp.
(A) Anterior end, live specimen, dorsal view, MNCN 16.01/18463. (B) Anterior end, preserved specimen, dorsal view, MNCN 16.01/17972. (C) Trepan. (D) Detail of the proventricle, SEM. (E) Dorsal chaeta, midbody segment. (F) Medial chaeta, midbody segment. (G) Ventral chaeta, midbody segment.
Fig 8
Fig 8. Amblyosyllis antoni n. sp. SEM.
(A) Dorsal chaeta, anterior segment. (B) Dorsal chaeta, anterior segment. (C) Medial chaeta, anterior segment (D) Ventral chaetae, anterior segment.
Fig 9
Fig 9. Amblyosyllis sp. 1.
(A) Live specimen, dorsal view, MNCN 16.01/17973. (B) Live specimen, anterior end, dorsal view, MNCN 16.01/17974. (C) Anterior chaetae, SEM. (D) Dorsal chaeta, midbody segment. (E) Medial chaeta, midbody segment. (F) Ventral chaeta, midbody segment.
Fig 10
Fig 10. Amblyosyllis sp. 2.
(A) Live specimen, dorsal view, MNCN 16.01/17975. (B) Dorsal chaeta, midbody segment. (C) Medial chaeta, midbody segment. (D) Ventral chaeta, midbody segment. (E) Dorsal chaeta, anterior segment, SEM. (F) Medial chaeta, anterior segment, SEM. (G) Ventral chaeta, anterior segment, SEM.
Fig 11
Fig 11. Amblyosyllis sp. 3.
(A) Live specimens, dorsal view, MNCN 16.01/17976. (B) Dorsal chaeta, midbody segment. (C) Medial chaeta, midbody segment. (D) Ventral chaeta, midbody segment. (E) Dorsal chaeta, anterior segment, SEM. (F) Medial chaeta, anterior segment, SEM. (G) Medial chaeta, anterior segment, SEM. (H) Ventral chaeta, anterior segment, SEM.
Fig 12
Fig 12. Amblyosyllis finmarchica.
(A) Live specimen, dorsal view, MNCN 16.01/17978. (B) Trepan tooth (nine cusps in focus). (C) trepan tooth (five cusps in focus). (D) Dorsal chaeta, midbody segment. (E) Medial chaeta, midbody segment. (F) Ventral chaeta, midbody segment. (G) Medial chaeta, anterior segment, SEM. (H) Ventral chaeta, anterior segment, SEM.
Fig 13
Fig 13. Amblyosyllis ovei n. sp.
(A–E). Live specimens with slight differences in the colour pattern, dorsal view; A: MNCN 16.01/17985, B: MNCN 16.01/17986, C: MNCN 16.01/17983, D: MNCN 16.01/17984, E: MNCN 16.01/17985. (F) Dorsal chaeta, midbody segment. (G) Medial chaeta, midbody segment. (H) Ventral chaeta, midbody segment.
Fig 14
Fig 14. Amblyosyllis ovei n. sp. SEM.
(A) Anterior end, dorsal view. (B) Anterior parapodia, dorsolateral view. (C) Dorsal chaetae, anterior segment. (D) Dorsal and medial chaetae, anterior segment. (E) Medial chaeta, anterior segment. (F) Ventral chaeta, anterior segment.
Fig 15
Fig 15. Amblyosyllis sp. 4.
(A) Live specimen, dorsal view, MNCN 16.01/17987. (B) Dorsal chaeta, midbody segment. (C) Medial chaeta, midbody segment. (D) Ventral chaeta, midbody segment. (E, F) Dorsal chaetae, anterior segment, SEM. (G) Medial chaeta, anterior segment, SEM. (H) Ventral chaeta, midbody segment, SEM.
Fig 16
Fig 16. Amblyosyllis madeirensis.
(A–F) Live specimens with slight differences in the colour pattern, dorsal view. A: MNCN 16.01/17988, B: MNCN 16.01/17991, C: MNCN 16.01/17990, D: MNCN 16.01/17993, E: MNCN 16.01/17989, F: MNCN 16.01/17992. (G) Trepan. (H) Dorsal chaeta, midbody segment. (I) Medial chaeta, midbody segment. (J) Ventral chaeta, midbody segment.
Fig 17
Fig 17. Amblyosyllis madeirensis. SEM.
(A) Anterior parapodium, ventral view. (B) Dorsal chaetae, anterior segment. (C) Medial chaetae, anterior segment. (D) Ventral chaeta, anterior segment.
Fig 18
Fig 18. Amblyosyllis clarae n. sp.
(A) Live specimen, dorsal view, MNCN 16.01/17994. (B) Trepan teeth. (C) Complete trepan. (D) Midbody chaetiger and ventral cirri. (E) Dorsal chaeta, midbody segment. (F) Medial chaeta, midbody segment. (G) Ventral chaeta, midbody segment.
Fig 19
Fig 19. Amblyosyllis clarae n. sp. SEM.
(A–C) Dorsal chaetae, anterior segment. (D) Dorsal to medial chaetae, anterior segment.
Fig 20
Fig 20. Amblyosyllis lineata.
(A–F) Live specimens with differences in the colour pattern, dorsal view; A: MNCN 16.01/18004, B: MNCN 16.01/18008, C: MNCN 16.01/18011, D: MNCN 16.01/18012, E: MNCN 16.01/18003, F: MNCN 16.01/18009. (G) Dorsal chaeta, midbody segment. (H) Medial chaeta, midbody segment. (I) Ventral chaeta, midbody segment.
Fig 21
Fig 21. Amblyosyllis lineata. SEM.
(A–C) Medial chaetae, midbody segment. (D) Medial to ventral chaeta, midbody segment.
Fig 22
Fig 22. Amblyosyllis emilioi n. sp.
(A) Live specimen, dorsal view, MNCN 16.01/18018. (B, C) Trepan, cusps difficult to discern. (D) Dorsal chaeta, midbody segment, SEM. (E) Ventral chaeta, midbody segment, SEM. F. Medial chaetae, midbody segment. (G) Medial chaeta, midbody segment. (H) Ventral chaeta, midbody segment.
Fig 23
Fig 23. Amblyosyllis rhombeata n. sp.
(A) Live specimen, dorsal view, MNCN 16.01/18023. (B) Dorsal chaeta, midbody segment, SEM. (C) Dorsal chaeta, midbody segment. (D) Medial chaeta, midbody segment. (E) Ventral chaeta, midbody segment.
Fig 24
Fig 24. Amblyosyllis hectori n. sp.
(A) Live specimen, dorsal view, MNCN 16.01/18026. (B) Dorsal chaeta, midbody segment. (C) Medial chaeta, midbody segment. (D) Ventral chaeta, midbody segment. (E–G) Chaetae, midbody segment, SEM.
Fig 25
Fig 25. Amblyosyllis anae n. sp.
(A) Live specimen, dorsal view, MNCN 16.01/18028. (B) Dorsal chaeta, midbody segment. (C) Medial chaeta, midbody segment. (D) Ventral chaeta, midbody segment. (E, F) Trepan teeth, cusps difficult to discern. (G) Dorsal chaetae, midbody segment, SEM. (H) Ventral chaetae, midbody segment, SEM.
Fig 26
Fig 26. Amblyosyllis nigrolineata.
(A) Live specimen, dorsal view, MNCN 16.01/18041. (B) Trepan. (C) Dorsal chaeta, midbody segment. (D) Medial chaeta, midbody segment. (E) Ventral chaeta, midbody segment. (F) Chaetal fascicle, midbody segment, SEM. (G, H) Medial chaetae, midbody segment, SEM. (I) Ventral chaeta, midbody segment, SEM.
Fig 27
Fig 27. Amblyosyllis plectorhyncha.
(A) Live specimen, dorsal view, MNCN 16.01/18044. (B) Dorsal chaeta, midbody segment. (C) Medial chaeta, midbody segment. (D) Ventral chaeta, midbody segment. (E) Dorsal chaeta, anterior segment, SEM. (F) Dorsal chaetae, midbody segment, SEM. (G, H) Medial chaetae, midbody segment, SEM.
Fig 28
Fig 28. Amblyosyllis idae n. sp.
(A–B) Live specimens with differences in colour patterns, dorsal view; A: MNCN 16.01/18050, B: MNCN 16.01/18049. (C) Trepan. (D) Dorsal chaeta, midbody segment. (E) Medial chaeta, midbody segment. (F) Ventral chaeta, midbody segment.
Fig 29
Fig 29. Amblyosyllis idae n. sp. SEM.
(A) Midbody fascicle, ventral view. (B) Dorsal chaeta, midbody segment. (C–E) Medial chaetae, midbody segments. (F) Ventral chaeta, midbody segment.
Fig 30
Fig 30. Amblyosyllis spectabilis.
(A–G) Live specimens with differences in the colour patterns, dorsal view; A: MNCN 16.01/18065, B: MNCN 16.01/18075, C: MNCN 16.01/18061, D: MNCN 16.01/18076, E: MNCN 16.01/18064, F: MNCN 16.01/18073, G: MNCN 16.01/18074.
Fig 31
Fig 31. Amblyosyllis spectabilis.
(A–G) Live specimens with differences in the colour patterns, dorsal view; A: MNCN 16.01/18080, B: MNCN 16.01/18052, C: MNCN 16.01/18059, D: MNCN 16.01/18060, E: MNCN 16.01/18058, F: MNCN 16.01/18057, G: MNCN 16.01/18077.
Fig 32
Fig 32. Amblyosyllis spectabilis.
(A–J) Trepans of different individuals. (K) Dorsal chaeta, midbody segment. (L) Medial chaeta, midbody segment. (M) Ventral chaeta, midbody segment.
Fig 33
Fig 33. Amblyosyllis spectabilis. SEM.
(A) Dorsal and medial chaetae, midbody segment. (B–C) Dorsal and medial chaetae, midbody segment. (D) Ventral chaeta, midbody segment.
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