Heterospio paulolanai, Blake & Maciolek, 2023

Blake, James A. & Maciolek, Nancy J., 2023, New species and records of Heterospio (Annelida, Longosomatidae) from continental shelf, slope and abyssal depths of the Atlantic Ocean, Pacific Ocean, Indian Ocean and adjacent seas, Zootaxa 5260 (1), pp. 1-74 : 32-34

Heterospio paulolanai new species

Figure 13

urn:lsid:zoobank.org:act:9D2C1C8E-4088-4EA7-B564-EAFB7B64AA2E

Material examined. South Atlantic Ocean, Brazil, offshore São Paulo, Súeste IV, Sta. 6672, coll. 14 Nov 1985, 24.735°S, 45.917°W, 69 m, mud and shell gravel, holotype ( MZUSP 5588 ) .

Description. Holotype (MZUSP 5588) only specimen, incomplete with 12 setigers, long, narrow, 27 mm long, 1.0 mm wide across thoracic setigers, 0.8 mm wide across abdominal segments. Specimen with some segments (setigers 1, 9, and 11) damaged, partially dissected by a previous worker. Thoracic region with nine setigers, 1–8 short, 9 transitional, about 2.5 times as long as setiger 8 ( Fig. 13A ). Thoracic segments with defined dorso-lateral setal fascicles transitioning to abdominal segments with setae arising from broad cincture-like fascicles with rows of setae mostly surrounding anterior margin of each segment, but with wide dorsal and ventral gaps. Abdominal segments 10–12 very long, each longer than entire thoracic region. Color in alcohol brown.

Pre-setiger region triangular in shape, about as long as first two thoracic setigers ( Fig. 13A–B ). Prostomium rhomboid-shaped, tapering to rounded tip ( Fig. 13A ); eyespots absent, nuchal organs narrow slits laterally at posterior junction of prostomium and peristomium ( Fig. 13A ). Peristomium with two dorsolateral rings apparent dorsally and laterally, separated by groove from which dorsal tentacles arise medially; no tentacles present, but scars evident in grooves. Peristomium incomplete dorsally, interrupted by posterior extension of prostomium merging with dorsal surface, dorsal crest lacking. Ventral surface of peristomium broad a single broad surface, anteriorly encompassing mouth, merging posteriorly with broad ventral surface of thoracic segments ( Fig. 13B ). Mouth a transverse slit consisting of simple opening between two large lateral lobes and simple anterior and posterior lips ( Fig. 13B ).

Branchiae or their stubs present on setigers 2–8 ( Fig. 13A ), not observed on setiger 9 possibly due to damage from an earlier dissection; most branchiae when present long, thin, rounded in cross section, tapering to rounded tip; branchiae with narrow ciliated groove; internal blood vessel extends along entire length.

All parapodia biramous with setae emerging from near anterior edge of each segment ( Fig. 13A–B ). Thoracic setigers with notches from which dense setal fascicles in dorsolateral locations arise on each segment; postsetal lamellae not observed, but short elevated ridge present on posterior margin of notch from which thoracic neurosetae arise; thoracic notosetae with numerous capillaries (25+) in dense fascicle with distinct rows not defined; neurosetae similarly arranged with capillaries even more numerous (~60+). Abdominal setigers from setiger 10 with setae arranged in long double rows nearly surrounding body, with relatively wide dorsal and ventral gaps. Setiger 10 with all capillaries arranged in two rows; setiger 11 with anterior row of aristate spines ( Fig. 13C ) and posterior row consisting of thickened capillaries ( Fig. 13D ); setiger 12 with anterior row of acicular spines ( Fig. 13E ) and posterior row of thick, curved, pointed subuluncini ( Fig. 13F ).

Posterior region not present.

Methyl Green staining. Methyl Green producing prominent pattern on pre-setiger and anterior thoracic segments. Stain concentrates on posterior and lateral margins of prostomium and both peristomial rings on dorsal and lateral surfaces. Stain also concentrates laterally on setigers 1–5 producing dark-green parapodia. Rest of body lacking distinct pattern.

Remarks. Heterospio paulolanai n. sp. belongs to a group of Heterospio having a narrow conical prostomium, two peristomial rings, 7–8 pairs of branchiae, and setiger 9 as the first elongate segment about 2–3 times longer than setiger 8. Of these, H. paulolanai n. sp. is most similar to H. aruba n. sp., H. guiana n. sp., and H. sinica in having all capillaries on setiger 10 and following setigers with at least a few aristate spines. However, H. aruba n. sp. and H. paulolanai n. sp. also have acicular spines that are lacking in H. guiana n. sp. and H. sinica . Heterospio aruba n. sp. differs from H. paulolanai n. sp. in having prominent postsetal lamellae on thoracic neuropodia, an oral opening that is a narrow transverse slit with no obvious lobes or surrounding papillae, and a distinct ventral ridge that extends from the mouth posteriorly over the peristomium and first seven setigers. In contrast, H. paulolanai n. sp. has no obvious thoracic neuropodial lamellae, an oral opening bordered by two large lateral lobes, and no ventral ridge.

Etymology. This species is named for the late Professor Paulo da Cunha Lana, prominent Brazilian authority on annelids. Prof. Lana was host of the sixth International Polychaete Conference held in Curitiba, Brazil (Aug 2–7, 1998) and later elected the ninth President of the International Polychaetology Association (2010–2013).

Distribution. Off southeastern Brazil, 69 m.

Figures

FIGURE 13. Heterospio paulolanai n. sp. Holotype (MZUSP 5588):A, anterior end (setiger 1–10), dorsal view; B, anterior end (setiger 1–5), ventral view; C, neuropodial aristate spines, setiger 11; D, neuropodial capillary seta, setiger 11; E, neuropodial acicular spine, setiger 12; F, neuropodial subuluncinus, setiger 12.