Leitoscoloplos fragilis (Verrill, 1873)

Blake, James A., 2021, New species and records of Orbiniidae (Annelida, Polychaeta) from continental shelf and slope depths of the Western North Atlantic Ocean, Zootaxa 4930 (1), pp. 1-123: 15-19

publication ID

https://doi.org/10.11646/zootaxa.4930.1.1

publication LSID

lsid:zoobank.org:pub:97110C21-173C-4552-96AC-4B5DC987FF1C

DOI

http://doi.org/10.5281/zenodo.4677360

persistent identifier

http://treatment.plazi.org/id/03C9912C-FFDC-FFA5-01A7-1320FB1DFD4C

treatment provided by

Plazi

scientific name

Leitoscoloplos fragilis (Verrill, 1873)
status

 

Leitoscoloplos fragilis (Verrill, 1873)  

Figures 4–5 View FIGURE 4 View FIGURE 5

Anthostoma fragile Verrill, 1873: 598–599   .

Scoloplos fragilis: Verrill 1881: 301   ; Hartman 1942: 60–61, figs. 113-115; Brown 1982: 213–227.

Scoloplos (Scoloplos) fragilis: Pettibone 1963: 290–292   , fig. 76a–f.

Haploscoloplos fragilis: Hartman 1944: 340   , pl. 14, fig. 5, pl. 18, fig. 6; 1945: 30, pl. 6, fig. 5; 1951: 76–78, pl. 21, figs. 1–3; 1957: 271–272, p. 25, figs. 1–3; Trott 2004: 280.

Leitoscoloplos fragilis: Taylor 1984   : 1.19–1.21, fig. 1.18a–g; Mackie 1987: 15–16, fig. 16; Blake et al. 2001: Appendix, 9-1; Fauchald, Granados-Barba & Solís-Weiss 2009: 763; Blake 2017: 18.

Material examined. (1,239 specimens) Northeastern USA, Maine, Damariscotta River Estuary, Upper Dodge Cove , coll. V. Walker, 05 Aug 1966, 43°59.658′N, 69°33.255′W, intertidal (18, MCZ 161580 View Materials ) GoogleMaps   .— Massachusetts, Woods Hole , coll. G. Sene Silva, 08 Aug 2005, intertidal (1, MCZ 161581 View Materials )   .— Massachusetts, New Bedford Harbor, Long-term Monitoring Program, 1999 September-October Survey : ( Upper Harbor ): Sta. 105-1, 14 Sep 1999, 41°36.407′N, 70°53.983′W, 6.4 m (1, MCZ 161540 View Materials ) GoogleMaps   ; Sta. 108-3, 06 Oct 1999, 41°40.496′N, 70°54.955′W, 1 m (3, MCZ 161541 View Materials ) GoogleMaps   ; Sta. 111-1, 05 Oct 1999, 41°40.42′N, 70°54.9′W, 1 m (1, MCZ 161542 View Materials ) GoogleMaps   ; Sta. 120-1, 18 Nov 1999, 41°13′N, 70°55.08′W, 1 m (5, MCZ 161543 View Materials ) GoogleMaps   ; Sta. 121-3, 18 Nov 1999, 41°40.154′N, 70°55.003′W, 1.4 m (5, MCZ 161544 View Materials ) GoogleMaps   ; Sta. 125-3, 29 Sep 1999, 41°40.01′N, 70°55.098′W, 3 m (2, MCZ 161545 View Materials ) GoogleMaps   ; Sta. 130-3, 01 Oct 1999, 41°39.848′N, 70°55.086′W, 1.8 m (2, MCZ 161546 View Materials ) GoogleMaps   ; Sta. 134-1, 01 Oct 1999, 41°39.756′N, 70°55.032′W, 2.3 m (46, MCZ 161547 View Materials ) GoogleMaps   ; Sta. 135-3, 01 Oct 1999, 41°39.753′N, 70°54.936′W, 1.7 m (40, MCZ 161548 View Materials ) GoogleMaps   ; Sta. 139-1, 29 Sep 1999, 41°39.675′N, 70°55.104′W, 1.4 m (71, MCZ 161549 View Materials ) GoogleMaps   ; Sta. 140-3, 01 Oct 1999, 41°39.685′N, 70°54.977′W, 3.3 m (30, MCZ 161550 View Materials ) GoogleMaps   ; Sta. 147, 28 Sep 1999, 41°39.594′N, 70°54.91′W, 1.7 m (2, MCZ 161551 View Materials ) GoogleMaps   ; Sta. 150-3, 28 Sep 1999, 41°39.513′N, 70°55.087′W, 3.4 m (13, MCZ 161552 View Materials ) GoogleMaps   ; Sta. 154-2, 28 Sep 1999, 41°39.415′N, 70°55.050′W, 3.4 m (3, MCZ 161553 View Materials ). ( Lower Harbor ) GoogleMaps   : Sta. 202-1, 06 Oct 1999, 41°39.323′N, 70°55.032′W, 4.7 m (30, MCZ 161554 View Materials ) GoogleMaps   ; Sta. 207-1, 22 Sep 1999, 41°38.984′N, 70°55.270′W, 1.7 m (147, MCZ 161555 View Materials ) GoogleMaps   ; Sta. 208-2, 23 Sep 1999, 41°38.981′N, 70°55.022′W, 1.3 m (35, MCZ 161556 View Materials ) GoogleMaps   ; Sta. 212-2, 24 Sep. 1999, 41°38,826′N, 70°4.906′W, 3.3 m (2, MCZ 161557 View Materials ) GoogleMaps   ; Sta. 216-2, 22 Sep 1999, 41°38.660′N, 70°55.023′W, 2.2 m (10, MCZ 161558 View Materials ) GoogleMaps   ; Sta. 218-1, 27 Oct 1999, 41°38.663′N, 70°54.527′W, 9.5 m (26, MCZ 161559 View Materials ) GoogleMaps   ; Sta. 220-2, 22 Sep 1999, 41°38.507′N, 70°55.141′W, 11.1 m (31, MCZ 161560 View Materials ) GoogleMaps   ; Sta. 222-1, 23 Sep 1999, 41°38.501′N, 70°54.641′W, 3.1 m (79, MCZ 161561 View Materials ) GoogleMaps   ; Sta. 224-3, 22 Sep 1999, 41°38.338′N, 70°55.269′W, 10 m (37, MCZ 161562 View Materials ) GoogleMaps   ; Sta. 226-1, 21 Sep 1999, 41°38.336′N, 70°54.809′W, 3.5 m (39, MCZ 161563 View Materials ) GoogleMaps   ; Sta. 227-3, 21 Sep 1999, 41°38.330′N, 70°54.537′W, 3 m (71, MCZ 161564 View Materials ) GoogleMaps   ; Sta. 231-1, 21 Sep 1999, 41°38.166′N, 70°54.874′W, 4.1 m (21, MCZ 161565 View Materials ) GoogleMaps   ; Sta. 235-3, 20 Sep 1999, 41°38.011′N, 70°55.035′W, 8.8 m (17, MCZ 161566 View Materials ) GoogleMaps   ; Sta. 237-1, 24 Sep 1999, 41°38.006′N, 70°54.541′W, 6 m (1, MCZ 161567 View Materials ) GoogleMaps   ; Sta. 240-3, 20 Sep 1999, 41°37.873′N, 70°54.91′W, 10 m (28, MCZ 161568 View Materials ) GoogleMaps   ; Sta. 242, 20 Sep 1999, 41°37.67′N, 70°54.416’′W, 5.8 m (9, MCZ 161569 View Materials )   ; Sta. 245-3, 19 Sep 1999, 41°37.67′N, 70°54.780′W, 3.4 m (43, MCZ 161570 View Materials ) GoogleMaps   ; Sta. 249-1, 19 Sep 1999, 41°37.52′N, 70°54.67′W, 2.4 m (17, MCZ 161571 View Materials ) GoogleMaps   ; Sta. 250- 3, 19 Sep 1999, 41°37.51′N, 70°54.42′W, 8.5 m (10, MCZ 161572 View Materials ). (Outer Harbor) GoogleMaps   : Sta. 306-3, 14 Sep 1999, 41°37.15′N, 70°52.237′W, 2.8 m (12, MCZ 161573 View Materials ) GoogleMaps   ; Sta. 310-1, 14 Sep 1999, 41°36.407′N, 70°53.983′W, 6.4 m (1, MCZ 161574 View Materials ) GoogleMaps   .— Connecticut, Noank , coll. J.A. Blake, 3 May 1966, 41°19.48′N, 71°59.05′W, intertidal (1, MCZ 161582 View Materials ) GoogleMaps   ; Mystic , coll. J.A. Blake, 21 Dec 1965, 41°20.8′N, 71°58.29′W, intertidal (1, MCZ 161579 View Materials ) GoogleMaps   .— New York, Long Island Sound, off Eastchester , Sta. IG 25, coll. P.L. Neubert, 28 Oct 1999, 40°52.45′N, 73°45.15′W, 23 m (18, MCZ 161585 View Materials ) GoogleMaps   ; Sta. IG 26, 28 Oct 1999, 40°52.20′N, 73°45.66′W, 13 m (115, MCZ 161586 View Materials ) GoogleMaps   ; off Throgs Neck , Sta. TN 6A, coll. P.L. Neubert, 40°48.6848′N, 73°48.6204′W, 4 m (150, MCZ 161583 View Materials ) GoogleMaps   ; Sta. TN12A, 40°48.7949′N, 73°47.1572′W, 16 m (45, MCZ 161584 View Materials ) GoogleMaps   .

Description. Specimen from New Bedford Harbor (NBH) (MCZ 161559) complete, 3.5 cm long, 1.0 mm wide across thorax with 145 setigers, similar to largest specimens reported by Mackie (1987) from Nantucket, Massachusetts, of 3.9 cm long, 1.9 mm wide across thorax with 150 setigers. Pettibone (1963) reports larger specimens up 15

cm long, 3 mm wide, and with up to 250 setigers. Body elongate, with thoracic segments short, dorsoventrally flattened, about 4.5 times as wide as long ( Fig. 4A View FIGURE 4 ). Thoracic segments of largest specimens with low transverse ridge across dorsum and venter between parapodia. Anterior abdominal segments becoming longer, about 1.5 times as wide as long in anterior segments; middle and posterior abdominal segments crowded, very short. Larger specimens with shallow mid-ventral groove present from middle abdominal segments to near posterior end. Color in alcohol light tan.

Pre-setiger region triangular, elongate, as long as first two setigers ( Fig. 4 View FIGURE 4 A–B). Prostomium conical, tapering to pointed tip; nuchal organs curved slits on posterior lateral margin; eyespots absent (but see juvenile morphology below). Peristomium a single smooth achaetous ring dorsally, ventrally encompassing mouth with upper lip formed of two large lobes and lower lip with curved row of eight or more narrow elongate lobes ( Fig. 4B View FIGURE 4 ). Proboscis not observed but recorded as a multilobed sac when everted (Pettibone 1963).

Thorax with 14–16 setigers (13–16 recorded by Mackie 1987) with abrupt transition to abdominal segments with elongation of neuropodia and decrease in number of neurosetae. Thoracic notopodial postsetal lobes short, triangular in shape along most of thorax ( Fig. 4C View FIGURE 4 ), becoming longer in last 1–2 thoracic setigers ( Fig. 4D View FIGURE 4 ); all notopodial postsetal lamellae arising directly from body wall. Thoracic neuropodial postsetal lobes short, papillate, arising from broadly rounded base ( Fig. 4C View FIGURE 4 ); last 1–3 thoracic neuropodia with extra postsetal lobe and 1–2 short subpodial papillae resulting in last 1–3 thoracic setigers with three short lobes ( Fig. 4D View FIGURE 4 ). Abdominal notopodia becoming longer, fingerlike in middle and posterior segments ( Fig. 4 View FIGURE 4 E–F). Abdominal neuropodia longer and thickened in middle and posterior segments each narrowing to long narrow apical lobe with a short subterminal lateral cirrus; extra subpodial papillae retained only on first 3–4 abdominal neuropodia ( Fig. 4E View FIGURE 4 ), papillae then merging with subpodial flange and continuing over middle and posterior abdominal setigers as large, subpodial flange with 2–3 distinct lobes ( Fig. 4F View FIGURE 4 ). Prominent fingerlike interramal cirrus present on last 1–2 thoracic setigers ( Fig. 4D View FIGURE 4 ), continuing on anterior and middle abdominal setigers ( Fig. 4E View FIGURE 4 ), reduced to low interramal mound or process in posterior neuropodia ( Fig. 4F View FIGURE 4 ).

Branchiae from setiger 14 or posterior thoracic segment on Connecticut specimens and larger specimens from New Bedford Harbor, but recorded from abdominal segments by Pettibone (1963) and Mackie (1987); first branchiae on Connecticut and NBH specimens minute, papilliform, becoming full size by about setigers 25–27 or anterior abdominal segments. Anterior branchiae triangular, tapering to rounded apex ( Fig. 4D View FIGURE 4 ); branchiae of middle and posterior abdominal segments becoming longer and narrow apex more pointed ( Fig. 4 View FIGURE 4 E–F); all branchiae with transverse folds and cilia on inner and outer margins.

Notosetae all camerated capillaries; furcate and flail setae not observed; capillaries of thoracic segments numbering about 40 in 3–4 irregular rows in thoracic notopodia, reduced to about 15–20 in abdominal segments. Thoracic neurosetae all camerated capillaries with about 50 in 3–4 rows; abdominal neurosetae including 3–7 long stiff capillaries with barbs along one edge and 1–2 imbedded aciculae, none observed protruding.

Pygidium with two thin lateral anal cirri ( Fig. 5 View FIGURE 5 B–C).

Variability. The adult specimens encountered here differ from the accounts by Pettibone (1963) and Mackie (1987) in having branchiae from the last one or two thoracic setigers instead of the first abdominal setiger. In addition, the interramal cirrus is typically first present on posterior thoracic segments together with extra subpodial lobes. The interramal cirri are best observed by staining with Shirlastain A; they are more-or-less limited to the last thoracic and middle abdominal setigers. The cirri are reduced to a short, rounded process on small specimens and difficult to see.

Juvenile morphology. Juveniles were present in samples from the Throgs Neck (TN) (MCZ 161583) and NBH (MCZ 161564) collections. Several of these specimens were examined in an effort to determine at what size the characters that distinguish L. fragilis   from local congeners were present. However, unlike the 300-µm-mesh sieve used to collect the L. acutus   juveniles from Massachusetts Bay, the sieve size used to separate the fauna from the TN and NBH sediment was 500-µm mesh. As a result, there were fewer juveniles in these samples. However, the smallest sizes observed of L. fragilis   were similar to those of L. acutus   .

All juveniles have an acutely pointed prostomium; body segments are crowded, especially in posterior setigers. A 28-setiger juvenile from TN is 2.1 mm long with nine thoracic setigers and branchiae from setiger 10 ( Fig. 5A View FIGURE 5 ). Low interramal processes are present on anterior abdominal setigers; these are the anlage of interramal cirri. At this stage, the prostomium is short and triangular. A 32-setiger NBH juvenile is 2.9 mm long with 11 thoracic setigers with branchiae from setiger 12 ( Fig. 5B, E View FIGURE 5 ). At this stage, the prostomium has elongated. The characteristic interramal cirri are observed on a few anterior abdominal setigers as low mounds; in middle and posterior neuropodia short subpodial flanges are irregular in shape due to weakly developed subpodial lobes; posterior setigers are crowded and the characteristic lobed subpodial flange is evident ( Fig. 5E View FIGURE 5 ). A 40-setiger NBH juvenile is 3.27 mm long with 12 thoracic setigers and branchiae from setiger 13 ( Fig. 5C View FIGURE 5 ). A few interramal cirri were observed in middle thoracic setigers ( Fig. 5D View FIGURE 5 ) and the neuropodia of the same segments were observed to have an irregular subpodial flange due to the presence of a superior subpodial papilla and medial notch. The prostomium has become longer and more pointed. Interestingly, a pair of eyespots was observed on the prostomium of the latter specimen and others of the same size ( Fig. 5F View FIGURE 5 ). Such eyespots were not observed on adults. The pygidium of all juveniles consisted two lobes each bearing a long anal cirrus ( Fig. 5B, F View FIGURE 5 ). Only camerated capillaries were observed in the noto- and neuropodia of these juveniles.

Remarks. Leitoscoloplos fragilis   is most similar to L. robustus   with which it sometimes occurs. The bilobed subpodial flanges of abdominal segments differ from those of L. robustus   , which has relatively smooth subpodial flanges (see comments below for L. robustus   ).

The juveniles and adults reported here indicate that the fewest number of thoracic setigers observed is nine on a 28-setiger specimen with branchiae from 10; the largest juvenile reported is a 40-setiger specimen with 12 thoracic setigers and branchiae from setiger 13. The larger adults reported here are up to 150 setigers, 12 cm long and with a thorax of 14–16 setigers and branchiae from the posteriormost thoracic setigers. The characteristic interramal cirri were present, if only rudimentary, on the smallest juveniles collected and the lobed appearance of the subpodial flange was obvious on the 40-setiger juvenile. These results indicate that the most important characters required to identify L. fragilis   are evident early in development.

Biology. Brown (1982) described some aspects of the distribution and biology of L. fragilis   on a tidal flat in Delaware, USA. The species lives in the upper 15 cm of sediments having sand-size particles (1.36–1.44 mean phi Ø). Salinity at the site ranged from 28–30 PSU and a wide range of water temperatures from 2.0°C in December to 28°C in August. At the study site, a wave-swept sand bar, the species occurred on slopes, ridges, and troughs with the highest densities on slopes. At least three age classes were found, with reproductive maturity occurring after two years; the smallest specimens occurred in the August or mid-summer samples. Gametogenesis and reproductive biology were not investigated; egg diameters were not provided and cocoons with eggs or larvae were not observed.

In New Bedford Harbor, Massachusetts, the highest densities of L. fragilis   occurred in lower portions of the Upper Harbor and throughout the Lower Harbor at stations having high sand and gravel content of 50% or greater ( Blake et al. 2001)   .

Distribution. Eastern Canada to Florida; Gulf of Mexico; intertidal to shallow subtidal.

Kingdom

Animalia

Phylum

Annelida

Class

Polychaeta

Family

Orbiniidae

Genus

Leitoscoloplos

Loc

Leitoscoloplos fragilis (Verrill, 1873)

Blake, James A. 2021
2021
Loc

Haploscoloplos fragilis:

Hartman, O. 1944: 340
1944
Loc

Scoloplos fragilis:

Brown, B. 1982: 213
Hartman, O. 1942: 60
1942