Monticellina anterobranchiata, Magalhães, Wagner F. & Bailey-Brock, Julie H., 2013
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publication ID |
https://doi.org/ 10.11646/zootaxa.3630.1.3 |
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publication LSID |
lsid:zoobank.org:pub:4D83BB98-9426-4138-B945-22B99034E791 |
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DOI |
https://doi.org/10.5281/zenodo.5632877 |
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persistent identifier |
https://treatment.plazi.org/id/9C12A93D-FFCB-980B-FF2C-9D30D8D3ECF2 |
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treatment provided by |
Plazi |
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scientific name |
Monticellina anterobranchiata |
| status |
sp. nov. |
Monticellina anterobranchiata View in CoL sp. nov.
Figures 15 View FIGURE 15 A–F, 16 A–F
Material examined. Holotype: Mamala Bay, south shore of Oahu Island, Hawaii, underneath threadfin mariculture cages, Sta. ER2, 21°17ʹ16ʺ N, 158°00ʹ30ʺ W, 30 m, Feb. 2003 (USNM 1195164). Paratypes: same locality as holotype (1, USNM 1195165); Sta. FWR2, 21°17ʹ16ʺ N, 158°00ʹ30ʺ W, 30 m, Jan. 2002 (2, USNM 1195166); 21°17ʹ16ʺ N, 158°00ʹ30ʺ W, 30 m, Sta. FWR2, Sep. 2004 (1, BPBM R3649); Mamala Bay, Sand Island outfall, south shore of Oahu Island, Hawaii, Sta. C1AR2, 21°17ʹ39ʺ N, 157°55ʹ27.9ʺ W, 18.9 m, Aug. 2009 (1 on stub, USNM 1195167).
Description. Holotype 6.0 mm long, 0.3 mm wide with 63 chaetigers. Paratypes 3.0– 4.5 mm long, 0.1–0.2 wide for 47–54 chaetigers. Body dorsally rounded and ventrally flattened. Thoracic chaetigers indistinct from abdominal ones; abdominal segments tapering posteriorly towards pygidium ( Figs 15 View FIGURE 15 C, 16D). Color in alcohol white to pale yellow.
Prostomium short, conical, rounded distally, nuchal organs postero-lateral, rounded; peristomium with three sub-equal annulations, elongate dorsal crest terminating at anterior border of chaetiger 1 ( Figs 15 View FIGURE 15 A, B, 16A). First pair of branchiae antero-lateral to dorsal tentacles on posterior border of third annulation ( Fig. 16 View FIGURE 16 B). Dorsal tentacles arising at level of first chaetiger, with second pair of branchiae lateral to dorsal tentacles on chaetiger 1 ( Fig. 16 View FIGURE 16 B).
Chaetae all capillaries of two types; thoracic chaetigers with 8–10 simple capillaries per fascicle ( Fig. 16 View FIGURE 16 C), reducing to 5–6 capillaries per fascicle in abdominal segments. Short capillaries with basally expanded blades and sawtooth edge from anterior abdominal neuropodia (chaetigers 13–16) and from far posterior abdominal notopodia (chaetigers 40–44), completely replacing simple capillaries posteriorly ( Figs 15 View FIGURE 15 D, 16E, F); barbs easily seen at 400×.
MGSP. The prostomium and peristomium stain intensely with the exception of an unstained ocular area; staining pattern similar to A. petersenae Blake, 1996 b ( Fig. 15 View FIGURE 15 E). Transverse ventral bands present on posterior margin of thoracic segments, extending dorsally and forming complete rings ( Fig. 15 View FIGURE 15 F).
Remarks. This new species is unique among Monticellina species due to the presence of the first pair of branchial filaments anterior to the dorsal tentacles. Other species commonly have the first pair of branchiae either lateral or postero-lateral to the dorsal tentacles ( Table 4 View TABLE 4 ). The MGSP of this new species leaves an unstained ocular area on the prostomium, very similar to Aphelochaeta petersenae which is distinct from the former by the larger size (35 mm), position of dorsal tentacles and first pair of branchial filaments and absence of short barbed capillaries on posterior end. The MGSP is also very similar to that of some species of Aphelochaeta with ventral bands on thoracic segments. However, this species is placed in the genus Monticellina due to the nature of the posterior capillary chaetae, with distinct lateral barbs seen at 400× in addition to the normal fibrils along the capillary edge. Table 4 View TABLE 4 summarizes relevant morphological characters for Monticellina species closely related to M. anterobranchiata sp. nov.
Etymology. The Latin name of this species refers to the anterior position of the first pair of branchiae in relation to the dorsal tentacles.
Biology/Ecology. Sampled from sandy bottoms adjacent to sewage outfalls at 18 m and sandy bottoms underneath threadfin mariculture cages at 30 m.
Distribution. Mamala Bay, south shore of Oahu Island, Hawaii, USA.
Species First appearance of spines Nature of spines Posterior end (max. number of spines)
T. acutus Webster & Absent on notopodia Short or long, irregular knob-tipped, Expanded laterally, simple
Benedict, 1887 100 neuropodia (1–3) thickened on convex side conical pygidium Material examined. Hanauma Bay, southeast shore of Oahu Island, Hawaii. Holotype: Olive Beach, 21°16ʹ6.52ʺ N, 157°41ʹ47.35ʺ W, 18 Apr. 2000, coll. R. Brock (USNM 1195168). Paratypes: same locality, date and collector as holotype (4, USNM 1195169; 2 on stub, USNM 1195170; 3, BPBM R3650). Additional material: Sand Island outfall, south shore of Oahu Island, Hawaii: Sta. E3R3, 21°16ʹ43.4ʺ N, 157°54ʹ39.1ʺ W, 101.2 m, Aug. 2011 (16).
Description. Holotype 11 mm long, 0.4 mm wide in thoracic segments, 0.3 mm wide in abdominal segments for about 97 chaetigers. Paratypes 4–10 mm long, 0.2–0.5 mm wide, for about 60–88 chaetigers. Body divided into three parts ( Fig. 17 View FIGURE 17 E): thoracic chaetigers distinct but not crowded, not expanded, rounded dorsally and slightly flattened ventrally ( Fig. 17 View FIGURE 17 A); abdominal segments apparently longer than wide, never moniliform ( Fig. 17 View FIGURE 17 E); posterior end slightly expanded, chaetigers distinct, rounded dorsally, flattened ventrally, without ventral and dorsal grooves ( Fig. 17 View FIGURE 17 C). Body color in preserved specimens light to dark brown; anterior and posterior ends darker than mid-body chaetigers ( Fig. 17 View FIGURE 17 E). Pygidium with simple dorsal lobe above anal aperture ( Fig. 17 View FIGURE 17 C).
Prostomium conical, rounded anteriorly, without eyes and with a pair of postero-lateral nuchal organs ( Figs 17 View FIGURE 17 A, B, 18A, B). Peristomium elongate, as long as 5–6 anterior chaetigers, without distinct annulations ( Figs 17 View FIGURE 17 A, B, 18A, B). Dorsal tentacles arising between peristomium and chaetiger 1 ( Fig. 18 View FIGURE 18 B); first branchiae postero-lateral to dorsal tentacles on chaetiger 1 and present throughout; branchiae from abdominal chaetigers 2–3 times thicker than thoracic branchiae and directed anteriorly ( Fig. 17 View FIGURE 17 A, D).
Chaetae all capillaries of two types; thoracic chaetigers with 8–10 simple capillaries per fascicle ( Fig. 18 View FIGURE 18 D); short capillaries slightly expanded basally with very fine dentition not seen under light microscopes, beginning after chaetiger 30–35 in neuropodia and from far posterior abdominal notopodia, 2–4 capillary chaetae per fascicle ( Fig. 18 View FIGURE 18 C).
MGSP. Body stains light green throughout, thoracic ventral bands present in inter-segmental areas only from about chaetigers 4–12 ( Fig. 17 View FIGURE 17 D).
Remarks. Monticellina hanaumaensis sp. nov., appears to be a unique species because specimens were removed from coral rubbles by dissolution of the coral skeletons with a solution of nitric acid as described in Brock & Brock (1977). The dark coloration of preserved specimens is uncommon among Monticellina . It shows similarities with Monticellina tesselata (Hartman, 1960) in the nature of the modified chaetae with very fine denticles, peristomium with indistinct annulations and posterior end with expanded segments but differs most notably by the presence of a mid-dorsal thoracic ridge and presence of conspicuous lateral processes formed from adhering mucus in the tubes of M. tesselata .
This new species may easily be misidentified as belonging to Aphelochaeta due to the presence of very fine dentition in the modified chaetae. For instance, it shows some similarities with Aphelochaeta elongata Blake, 1996 and Aphelochaeta multifilis (Moore, 1909) in which the prostomium is merged with the peristomium forming a head with indistinct annulations. However, A. elongata has a narrow posterior end, while M. hanaumaensis sp. nov., and A. multifilis have an expanded posterior end and the latter differs from M. hanaumaensis sp. nov., by having a ventral groove.
Etymology. This species is named after its type locality Hanauma Bay in Oahu Island, Hawaii.
Biology/Ecology. Specimens were recovered from acid dissolved samples and may be residents of burrows made by other organisms as observed in Cirratulus balaenophilus which live in fresh whale bones but do not appear to bore into them (Taboada et al. 2012).
Distribution. Hanauma and Mamala bays, south shore of Oahu Island, Hawaii, USA.
TABLE 4. Synoptic table of morphological characteristics of five closely related species of Tharyx including the new species from Hawaii, compared to the type species Tharyx acutus Webster & Benedict, 1887.
| Species | Prostomium | Number of peristomial annulations | Position of first pair of branchiae | Abdominal segments |
|---|---|---|---|---|
| T. acutus Webster & Benedict, 1887 | Elongate, pointed | 2–3 | Posterior to dorsal tentacles; on peristomium | Narrow? |
| T. kirkegaardi Blake, 1991 | Acutely pointed | 1–2 | Postero-lateral to dorsal tentacles; on peristomium | Longer than thoracic, beadlike in juveniles |
| T. longisetosa (Hutchings & Murray, 1984) | Short, conical | 3 | Postero-lateral to dorsal tentacles; on peristomium | Dorso-ventrally flattened |
| T. retusiseta (Hutchings & Murray, 1984) | Short, conical | 3 | Postero-lateral to dorsal tentacles; on peristomium | Dorso-ventrally flattened |
| T. parvus Berkeley, 1929 | Short, pointed | 1 | Postero-lateral to dorsal tentacles; on chaetiger 1 | Longer than thoracic, never moniliform |
| T. tumulosa sp. nov. | Elongate, pointed | 3 | Postero-lateral to dorsal tentacles; on chaetiger 1 | Rounded to moniliform |
| continued. |
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