Trichobranchidae Malmgren, 1866
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publication ID |
https://doi.org/ 10.5852/ejt.2021.782.1593 |
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publication LSID |
lsid:zoobank.org:pub:510DE23F-4CE5-4DDF-B1E7-CA8346AA4F5F |
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DOI |
https://doi.org/10.5281/zenodo.5784419 |
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persistent identifier |
https://treatment.plazi.org/id/03A4A269-7921-6138-1B3C-FA388A6C6409 |
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treatment provided by |
Felipe |
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scientific name |
Trichobranchidae Malmgren, 1866 |
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Family Trichobranchidae Malmgren, 1866 View in CoL
Figs 1A View Fig , 7–8 View Fig View Fig
Diagnosis (after Hutchings et al. 2021a, most important diagnostic characters highlighted in bold)
Transverse prostomium attached to dorsal surface of upper lip; basal part as thick crest, eyespots sometimes present; distal part at base of upper lip or extending along lip. Buccal tentacles of two types, uniformly cylindrical and expanded at tips, spatulate. Peristomium forming lips, sometimes also a ventral lobe, as an extension of the lower lip; lips expanded, circular upper lip, distal margin folded or convoluted; lower lip button-like, usually continuing by ventral lobe, or expanded, forming large scoop-shaped process ( Figs 7A–C View Fig , 8A, C–D View Fig ). Segment I usually short, frequently only visible ventrally; anterior margin of anterior segments with lobes as low, even-length collars covering posterior margins of preceding segments, at least ventrally; ventro-lateral or lateral lobes on anterior segments sometimes present. Anterior segments poorly glandular ventrally, smooth, discrete shields absent; midventral groove extending from posterior segments with notopodia. Two to four pairs of branchiae, beginning from SGII, each pair with single, thick and elongate, tapered or foliaceous filament, or two pairs fused in single four lobed structure originating mid-dorsally between SGII–III or II–IV ( Figs 7C View Fig , 8C–D View Fig ). Notopodia beginning from SGIII–VI, typically terminating at SGXX; short, conical notopodia, chaetae emerging from central core on top, distal lobes absent; narrowly-winged notochaetae in both rows throughout. Neuropodia beginning on same segment as notopodia or slightly posteriorly, rarely beginning before notopodia; sessile neuropodia until termination of notopodia, neurochaetae emerging directly from body wall, as rectangular to foliaceous pinnules after termination of notopodia; thoracic neurochaetae as acicular uncini ( Figs 1A View Fig , 7D View Fig , 8F View Fig ), sometimes with small hood or beard below main fang; avicular abdominal uncini, with secondary teeth in rows on top and laterally to main fang. Nephridial papillae on SGIII usually present, other papillae sometimes present on SGVI and SGVII, but reduced to inconspicuous in most taxa. Pygidium smooth to slightly crenulate, sometimes bilobed.
Remarks
In the past, the Trichobranchidae family was considered to be a subfamily of Terebellidae ( Fauvel 1927; Day 1967; Garrafoni & Lana 2004), but recent phylogenetic analyses support the hypothesis of a valid family ( Glasby et al. 2004; Nogueira et al. 2013). The family includes only three genera, i.e., Octobranchus Marion & Bobretzky, 1875 , Terebellides Sars, 1835 , and Trichobranchus Malmgren, 1866 . For Trichobranchus and Octobranchus , only three species of each occur in Europe. The genus Terebellides is very speciose and is represented in Europe by 19 species, 13 of them described in the last two years ( Lavesque et al. 2019b; Parapar et al. 2020a) ( Table 1 View Table 1 ).
Main morphological characters for European species
The number of branchiae is the best character to discriminate the different genera, with Terebellides having a single large branchia, Trichobranchus with two or three pairs of branchiae and finally Octobranchus with four pairs.
Trichobranchus species are easy to differentiate based on the number of branchiae (two vs three) ( Figs 7C View Fig , 8C View Fig ) and the absence or presence of eyespots. In Octobranchus , the species differ by the shape of the branchiae ( Fig. 8D View Fig ) and the number of secondary teeth above the main fang of the uncini. Regarding Terebellides species , recent studies highlighted that several characters are very important for identification to the species level ( Lavesque et al. 2019a; Parapar et al. 2020a, 2020b). However, as many cryptic species occur at a small geographical scale ( Nygren et al. 2018), which currently are confirmed only by molecular analyses ( Parapar et al. 2020a) much more work needs to be done to resolve all the species present.
BRANCHIAE. Even if Terebellides branchiae seem to be very similar within the genus ( Figs 7A–B View Fig , 8A–B View Fig ), several morphological characters permit the discrimination of species, such as the presence of a fifth anterior branchial lobe (e.g., T. europaea ), the degree of fusion of both upper and lower lobes (e.g.. not fused on T. ceneresi ), the presence of long terminal filaments (e.g., in T. shetlandica ) or short posterior processes ( Fig. 7B View Fig ), and finally the presence and the shape of papillae situated on the margins of the branchial lamellae ( Fig. 8B View Fig ) (e.g., T. lilasae ).
NOTOCHAETAE FROM FIRST CHAETIGER. The size of notochaetae of the first chaetiger varies between species. For most of the species, these chaetae are of a similar size compared to those of the following chaetigers. However, they can be absent or much shorter (e.g., T. ceneresi ) or much longer (e.g., T. mediterranea ).
PRESENCE OF GENICULATE CHAETAE ON ONE OR TWO CHAETIGERS. The geniculate chaetae are exclusive to members of Terebellides and they are typically present on CH 6 (SG VIII) only ( Fig. 8E View Fig ), but in some species they are present on two chaetigers, as for example in T. bigeniculatus .
UNCINI DENTICULATION. The different types of uncini follow the classifications provided by Parapar et al. (2020b) for thoracic uncini ( Fig. 8F View Fig ) and Parapar et al. (2020a) for abdominal uncini. These
classifications are based on the ratio between the length of the main fang (rostrum) and the crest of secondary teeth (capitium), and the size and number of the secondary teeth.
THORACIC CILIATED PAPILLAE. Following the recent study of Parapar et al. (2020a), the absence or the presence of thoracic ciliated papillae allow for the discrimination of Terebellides species. These papillae are situated dorsally to the thoracic notopodia (see for example Parapar et al. 2020a; Fig. 7B View Fig ).
METHYL GREEN PATTERN. The colouration of Terebellides specimens prior to identification is essential. Indeed, MG staining highlights the presence and the shape of the glandular region of the third thoracic chaetiger (e.g., undulating glandular region present and in members of T. gentili , oval for T. lilasae Fig. 7B View Fig ) and the compact/striped pattern of the ventral part of anterior chaetigers (e.g., CH 4 (SG VI) white in T. ceneresi ).
Key to European species of Trichobranchidae (after Lavesque et al. 2019a and Parapar et al. 2020a)
1. One large branchia consisting of a stem and four lobes with transverse lamellae .....5 ( Terebellides View in CoL )
– Two or three pairs of branchiae ........................................................................... 2 ( Trichobranchus View in CoL )
– Four pairs of branchiae ........................................................................................... 4 ( Octobranchus View in CoL )
2. Two pairs of branchiae ...................................................................................................................... 3
– Three pairs of branchiae, eyespots present ......................................................................................... ........................................................................................ Trichobranchus glacialis Malmgren, 1866 View in CoL
3. Eyespots absent ......................................................................... Trichobranchus roseus Malm, 1874 View in CoL
– Eyespots present ................................................................................................................................. ... Trichobranchus demontaudouini Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 View in CoL
4. Pairs of branchiae of different shapes; abdominal uncini with three rows of secondary teeth above the main fang ..................................................... Octobranchus floriceps Kingston & Mackie, 1980 View in CoL
– All pairs of branchiae similar; abdominal uncini with two rows of secondary teeth above the main fang ..................................................................................... Octobranchus lingulatus ( Grube, 1863) View in CoL
– Bases of branchiae covered by dorso-lateral lobes, abdominal uncini with two rows of secondary teeth above the main fang .............................. Octobranchus sikorskii (Leontovich & Jirkov. 2001) View in CoL
5. Geniculate acicular chaetae on CH 5 (SG VII) and CH 6 (SG VIII) .................................................... ......................................................... Terebellides bigeniculatus Parapar, Moreira & Helgason, 2011 View in CoL
– Geniculate acicular chaetae on CH 6 (SG VI) only ........................................................................... 6
6. Branchial lamellae without marginal papillae .................................................................................. 7
– Branchial lamellae with marginal papillae ..................................................................................... 15
7. Lower branchial lobes with long filaments ....................................................................................... 8
– Lower branchial lobes with or without short projections ................................................................. 9
8. Glandular region on CH 3 (SG V) present; branchial lamellae pointed; notochaetae from CH 1 longer than following ones; dorsal papillae absent ........................................................................................ ....................... Terebellides parapari Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 View in CoL
– Glandular region on CH 3 (SG V) absent; branchial lamellae rounded; all notochaetae equal-sized; dorsal papillae present ........................ Terebellides shetlandica Parapar, Moreira & O’Reilly, 2016 View in CoL
9. Ventral white band present on CH 4 (SG VI) after MG staining ..................................................... 10
– No distinct pattern on CH 4 (SG VI) after MG staining ...................................................................11
10. Large species (> 30 mm); 5 th branchial lobe present; notochaetae of CH 1 (SG III) similar to following ones; main fang of thoracic uncini straight .................................... Terebellides gracilis Malm, 1874 View in CoL
– Small species (<20 mm); 5 th branchial lobe absent; notochaetae of CH 1 (SG III) absent or shorter than following ones; main fang of thoracic uncini ‘eagle head’ (= curved) shaped ........................... ........................ Terebellides ceneresi Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 View in CoL
11. First notopodia and notochaetae longer than following ones ............................................................. .................................................................. Terebellides mediterranea Parapar, Mikac & Fiege, 2013 View in CoL
– First notopodia and notochaetae similar or shorter than following ones ........................................ 12
12. Large-sized species (> 50 mm); dorsal rounded projections on CH 1– CH 5 conspicuous ............... 13
– Small-sized species (<20 mm); dorsal rounded projections on CH 1– CH 5 absent; main fang of thoracic uncini straight ................................................................................................................... 14
13. Abdominal uncini of type 1 (length of capitium about 0.7 length of the main fang, capitium simple consisting of a few, wide denticles) .................................................................................................... ................................................ Terebellides kongsrudi Parapar, Capa, Nygren & Moreira, 2020 View in CoL and Terebellides bakkeni Parapar, Capa, Nygren & Moreira, 2020 View in CoL complex
– Abdominal uncini of type 2 (capitium of about same length as main fang, capitium complex composed of a first row of 4(5) denticles and a variable number of teeth in two more rows) ........... .......................................................................................................... Terebellides stroemii Sars, 1835 View in CoL
14. Glandular region on CH 3 (SG V) and 5 th branchial lobe both absent ................................................ ................................................................................................... Terebellides atlantis Williams, 1984 View in CoL
– Glandular region on CH 3 (SG V) and 5 th branchial lobe both present ............................................... ............................. Terebellides gralli Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 View in CoL
15. Glandular region on CH 3 (SG V) rounded or oval ......................................................................... 16
– Glandular region on CH 3 (SG V) otherwise .................................................................................. 17
16. Glandular region on CH 3 (SG V) staining in white, branchial lamellae with rounded papillae, CH 1– 3 without conspicuous dorsal projection ............................................................................................ ........................... Terebellides lilasae Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 View in CoL
– Glandular region on CH 3 (SG V) staining in blue, branchial lamellae with conical papillae, CH 1–3 with conspicuous dorsal projection .................................................................................................... ............................ Terebellides bonifi Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 View in CoL
17. Most branchial lamellae with marginal papillae ............................................................................. 18
– Only anterior branchial lamellae with marginal papillae ................................................................ 19
18. Branchial lamellae with digitiform papillae, upper lip elongated; MG staining pattern as compact bands from CH 1–5 ............................................................................................................................. ....................... Terebellides resomari Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 View in CoL
– Branchial lamellae with widely spaced, small and elongated digitiform papillae; MG staining pattern leaving white stripes from CH 1–5 ..................................................................................................... ........................... Terebellides gentili Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 View in CoL
19. Thoracic uncini type 1 (main fang vs capitium length ratio 2(3)/1; capitium with 2(3) large teeth, following ones much smaller) ............................................................................................................ ...................................................... Terebellides ronningae Parapar, Capa, Nygren & Moreira, 2020 View in CoL
– Thoracic uncini type 3 (main fang vs. capitium length ratio 1/1; capitium with 4(5) mid-sized teeth, following ones slightly smaller) ..................................................................................................... 20
20. Deep-water species, mostly found below 200 m deep ....................................................................... ....................................................... Terebellides norvegica Parapar, Capa, Nygren & Moreira, 2020 View in CoL
– Shallow-water species, mostly found above 100 m deep ................................................................... ............... Terebellides europaea Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 View in CoL and Terebellides scotica Parapar, Capa, Nygren & Moreira, 2020 View in CoL complex
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