Leodamas hyphalos, Blake, James A., 2017

Blake, James A., 2017, Polychaeta Orbiniidae from Antarctica, the Southern Ocean, the Abyssal Pacific Ocean, and off South America, Zootaxa 4218 (1), pp. 1-145 : 73-76

publication ID

https://doi.org/ 10.5281/zenodo.245827

publication LSID

lsid:zoobank.org:pub:9345C596-8656-4B5C-AD8C-2FACF4E9240C

DOI

https://doi.org/10.5281/zenodo.4901785

persistent identifier

https://treatment.plazi.org/id/8F2387DD-065D-0946-FF31-F94EFEE5F91F

treatment provided by

GgServerImporter

scientific name

Leodamas hyphalos
status

sp. nov.

Leodamas hyphalos View in CoL new species

Figures 33–34 View FIGURE 33 View FIGURE 34

Scoloplos (Leodamas) View in CoL spp. Hartman 1967: 108 (in part).

Material examined. Drake Passage, Eltanin Sta. 4-112, 20 Jul 1962, 56.03°S, 61.93° W, 4008 m, 13 paratypes (USNM 56456); Sta. 4-126, 29 Jul 1962, 57.20°S, 62.75°W, 3733–3806 m, holotype (USNM 1013904); and 13 paratypes (USNM 56457); Sta. 4-155, 17 Aug 62, 56.52°S, 63.25°W 3927 m, 7 paratypes (USNM 56458); R/V Polarstern, ANDEEP I, Sta. PS-61/043-2, 3958 m (1, SEM, JAB); PS-61/046-3, 2888 m (1, SEM, JAB).

Description. Majority of specimens small, incomplete; holotype 5.5 mm long and 0.7 mm wide for 29 setigers; largest paratype 9.0 mm long and 0.6 mm wide for 34 setigers. A single, much larger incomplete specimen from ANDEEP I Sta. PS-61 046-3 broken into two parts with 82 setigers, measuring 36 mm long and 3 mm wide across thorax. Color in alcohol: light brown.

Thoracic region with 16–18 setigers, inflated in first 3–4 setigers ( Fig. 33 View FIGURE 33 B), subsequent thoracic setigers depressed; transition to abdominal region gradual, with last three thoracic setigers having fewer setae ( Fig. 33 View FIGURE 33 C). Intersegmental annulations first present from setigers 8–9; these weakly developed, never prominent ( Fig. 33 View FIGURE 33 A). Branchiae from setiger 6 ( Figs. 33 View FIGURE 33 A, 34A); thoracic and anterior abdominal branchiae basally inflated ( Figs. 33 View FIGURE 33 A, 34A), subsequent abdominal branchiae expanded ( Fig. 33 View FIGURE 33 J); branchiae absent from far posterior setigers.

Prostomium triangular in outline, pointed on anterior margin ( Figs. 33 View FIGURE 33 A, 34A); eyespots absent; nuchal organs in SEM as transverse slits at border of prostomium and peristomium ( Fig 34 View FIGURE 34 A); proboscis divided into 3–4 lobes ( Fig. 34 View FIGURE 34 A). Peristomium with one short achaetous ring ( Figs. 33 View FIGURE 33 A, 34A).

Thoracic notopodia with minute postsetal lamellae on setigers 1–2, barely seen in SEM ( Fig. 33 View FIGURE 33 A), becoming larger more visible from setiger 3 ( Fig. 33 View FIGURE 33 A), short at first, then elongating, becoming unusually long, fingerlike structures ( Figs. 33 View FIGURE 33 A–C, 34A), continuing through abdominal region. Thoracic neuropodia with setae arising from elongated thickened lobes ( Figs. 33 View FIGURE 33 C, 34B); postsetal lamellae from setiger 5–11, attached to posterior border of upper one-third of setal lobe ( Figs. 33 View FIGURE 33 C, 34B); each lobe short triangular at first, then elongating in transitional region to form fingerlike lamella; a single subpodial lobe from setiger 14–15, continuing through anterior abdominal segments ( Fig. 33 View FIGURE 33 C); absent from middle and posterior abdominal segments ( Fig. 33 View FIGURE 33 J). Abdominal neuropodia elongated, with short ventral cirrus ( Fig. 33 View FIGURE 33 J).

Thoracic notopodia with fascicles of numerous crenulated capillaries and a single furcate seta; abdominal notopodia with three thin crenulated capillaries, two flail setae ( Fig. 33 View FIGURE 33 I) and 2–3 furcate setae ( Figs. 33 View FIGURE 33 G, 34E); furcate setae thin, delicate, easily broken, with unequal tynes connected by thin webbing composed of fine needles and shaft with faint annulations ( Fig. 33 View FIGURE 33 G); with SEM, furcate setae with 9–10 needles on each side with lateral ones merging with tynes; each tyne with minute apical opening ( Fig. 34 View FIGURE 34 E). Flail setae with thick, non-crenulated shaft bearing thin, crenulated tips ( Fig. 33 View FIGURE 33 I). Thoracic neuropodia with dense fascicles of blunt-tipped uncini arranged in four rows ( Fig. 33 View FIGURE 33 B–C); uncini of anterior row typically continuing ventrally below rows 2 and 3, then merging with row 4 forming a U-shape ( Fig. 33 View FIGURE 33 D); in some neuropodia, rows 2 and three also joined ventrally; uncini of anterior row sharply curved, with 3–5 transverse ridges ( Fig. 33 View FIGURE 33 E), with SEM ridges appearing irregular, angular ( Fig. 34 View FIGURE 34 C); uncini of posterior row not as sharply bent, with 9–10 transverse ridges ( Fig. 33 View FIGURE 33 F); 2–3 long crenulated capillaries present in superior position of last row of uncini ( Fig. 33 View FIGURE 33 B–C, 34B). Abdominal neurosetae including 1–2 simple, blunt-tipped acicula ( Figs. 33 View FIGURE 33 H, 34D) and 2–3 thin, simple capillaries ( Fig. 33 View FIGURE 33 J).

Etymology. hyphalos: Greek for submerged, in the deep.

Remarks. Of the six species of Leodamas encountered in this study, L. hyphalos n. sp. is the only one to bear flail setae in the abdominal notopodia. Leodamas hyphalos n. sp. is closest in morphology to L. marginatus in the nature and arrangement of the neuropodial uncini; both species have a few superior capillary setae dorsal to the posterior row of uncini. The thoracic neuropodial uncini of L. marginatus are arranged in three long vertical rows and with a short fourth row that continues ventral to the first three; in contrast, there are four long rows of uncini in L. hyphalos n. sp. with the first and last often merged ventrally and forming a U-shape. Although the majority of specimens were small, the much larger specimen from Sta. PS-61 046-3 from lower slope depths of 2888 m was similar to L. marginatus in size. The smaller specimens of L. hyphalos n. sp. all occurred at abyssal depths greater than 3600 m, suggesting that the species may be size limited in the deeper parts of its habitat, possibly due to limited or patchy organic input to the abyssal sediments. The close similarity of L. hyphalos n. sp. to L. marginatus suggests that it may be a lower slope and abyssal sibling of the widely distributed and common shelf and upper slope species.

Distribution. Known only from the Drake Passage between South America and the Antarctic Peninsula; 2888–4008 m.

Kingdom

Animalia

Phylum

Annelida

Class

Polychaeta

Family

Orbiniidae

Genus

Leodamas

Loc

Leodamas hyphalos

Blake, James A. 2017
2017
Loc

Scoloplos (Leodamas)

Hartman 1967: 108
1967
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