Heterospio indica Parapar, Vijapure, Moreira & Sukumaran, 2016

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 : 58-60

Heterospio indica Parapar, Vijapure, Moreira & Sukumaran, 2016

Figure 29

Heterospio indica Parapar, Vijapure, Moreira & Sukumaran, 2016: 4–14 , figs. 1–8.

Heterospio longissima: Rosenfeldt 1989: 231 , fig. 7. Not Ehlers, 1874, 1875. Fide Parapar et al. (2016).

Heterospio longissima: Hartman 1974a: 232 ; 1974b: 625; Wehe & Fiege 2002: 60; Not Ehlers, 1874, 1875.

Material examined. (2 specimens) Indian Ocean , International Indian Ocean Expedition , R / V Anton Bruun , Cruise 4B, Arabian Sea , Off Pakistan, S of Karachi, off mouth of Indus River , Sta. 230B, coll. 15 Nov 1963, John Ryther , Menzies Trawl, 23.517ºN, 66.917ºE, 88 m, sand, green clay, mud, (1, LACM-AHF Poly 13286).— R / V Anton Bruun, Cruise 4B, Arabian Sea off Madhavpur, India, Sta. 210A, coll. 16 Nov. 1963, John Ryther, Gulf of Mexico shrimp trawl, 21.117°N, 69.8°E to 21.15°N, 69.8°E, 34–37 m, (1, LACM-AHF Poly 13287) .

Description. Both specimens incomplete, each with 12 setigers. Body long, narrow, with evidence of tearing at posterior end; without longitudinal grooves or ridges along dorsal and ventral surfaces. Segmental boundaries denoted entirely by location of parapodia and setal fascicles. Body with nine anterior thoracic setigers with first eight crowded, each about five times wider than long ( Fig. 29A–B ), followed by an elongated setiger 9 about three times longer than each of first eight setigers. Following three abdominal segments each about as long as entire thoracic region. Largest specimen (LACM-AHF Poly 13286) 25 mm long and 1.1 mm wide across setiger 6; second specimen (LACM-AHF Poly 13287) smaller, 8.3 mm long and 0.5 mm wide. Color in alcohol opaque white; pigment entirely absent.

Pre-setiger region triangular in shape, about as long as first three thoracic setigers ( Fig. 29A–B ). Prostomium conical, wide basally, tapering to broadly rounded tip ( Fig. 29A–B ); eyespots absent, nuchal organs narrow slits along posterior-lateral margin. Peristomium with two rings, separated by groove extending across ventral surface ( Fig. 29B ), interrupted dorsally by dorsal crest extending from prostomium to setiger 1 ( Fig. 29A ); no dorsal tentacles present, but scars evident in medial notch in dorsal groove between peristomial rings. Mouth arising on first peristomial ring, located between two large lateral lobes and a single posterior lobe or lip ( Fig. 29B ); proboscis not emergent on either specimen.

Branchiae present on setigers 2–9 on both specimens ( Fig. 29A ); most reduced to scars or stubs, but when present, branchiae long, thin, rounded in cross section, tapering to rounded tip; branchiae with narrow ciliated groove; internal blood vessel extending along entire length.

All parapodia biramous with setal fascicles arising from near anterior edge of each segment.All thoracic setigers slightly flattened dorsally with parapodia weakly inflated dorsally and bearing setal fascicles in tight bundles. Neuropodia with prominent digitate postsetal lobe on all nine thoracic setigers ( Fig. 29B ). Abdominal setigers round in cross section and bearing setae in two transverse rows encircling anterior border of each segment. Abdominal parapodia from setiger 10 as narrow transverse and elongate lobes, encircling anterior margin of setigers 10–12; noto- and neuropodia with distinct dorsal and ventral gaps between setal fascicles; lateral gaps between noto- and neuropodia narrower.

All thoracic notopodia of setigers 1–9 with 50–75 long capillaries in dense spreading fascicles; neuropodia with similar numbers of capillaries in dense fascicles. Noto- and neuropodia of setiger 10 with thin capillaries arranged in two transverse rows with distinct dorsal and lateral gaps ( Fig. 29A–B ). Setigers 11–12 with anterior row containing thick spinous setae and posterior row with thin capillaries; spinous setae all with thick shaft, tapering to long, aristalike tip ( Fig. 29C–F ); these resembling different forms of subuluncini and aristate spines rather than capillaries as stated in Parapar et al. (2016). The few simple acicular spines present may be ones where tip has broken off.

Posterior region not present among fragments.

Methyl Green staining. Body staining uniformly; most of prostomium not staining, otherwise no pattern.

Remarks. The present specimens from shallow water in the Arabian Sea were originally referred to H. longissima by Hartman (1974a –b) and are here redescribed and referred to the recently described H. indica by Parapar et al. (2016) from the west coast of India.Although not mentioned by Parapar et al. (2016), a distinct dorsal peristomial crest and prominent neuropodial postsetal lamellae on thoracic setigers 1–9 were illustrated by these authors and occur in the present specimens. The only other species to have such prominent postsetal lamellae is H. aruba n. sp. described from shallow water in the Caribbean Sea (see above). The two species differ in that H. indica has both peristomial rings prominent on the ventral surface and the small oval mouth opening is surrounded by two large lateral lobes and a single posterior lobe; in contrast, H. aruba n. sp. has a smooth ventral surface lacking peristomial rings and the mouth is a simple transverse slit not surrounded by prominent oral lobes. In addition, H. aruba n. sp. lacks a dorsal peristomial crest instead of having one. Heterospio aruba n. sp. has branchiae on setigers 1–8 instead of 1–9; however, these specimens are smaller than recorded for H. indica and it is possible an additional branchia might develop with further growth. Although few specimens are available, it appears as if the neuropodial postsetal lamellae of H. aruba n. sp. are short over the first 1–3 setigers and then become longer over setigers 4–8 and then short again on setiger 9. In contrast, the neuropodial postsetal lamellae of H. indica are of a similar length over all nine setigers.

Parapar et al. (2016) described the spinous setae as different types of capillaries; however our interpretation is that these setae resemble the different kinds of subuluncini and aristate spines reported from species of Heterospio here and elsewhere.

Distribution. Arabian Sea, off Pakistan and W India 34–88 m (this study); W India 2.5–22 m ( Parapar et al. 2016).

Figures

FIGURE 29. Heterospio indica Parapar et al. 2016 (LACM-AHF Poly 13286). A, anterior end, dorsal view; B, anterior end, ventral view; C–F, spinous neurosetae from setiger 12.