Paradiopatra yasudai, (MAEKAWA & HAYASHI, 1989)

Budaeva, Nataliya & Fauchald, Kristian, 2011, Phylogeny of the Diopatra generic complex with a revision of Paradiopatra Ehlres, 1887 (Polychaeta: Onuphidae), Zoological Journal of the Linnean Society 163 (2), pp. 319-436 : 407-410

PARADIOPATRA YASUDAI ( MAEKAWA & HAYASHI, 1989) ( FIGS 81 AND 82)

Sarsonuphis yasudai Maekawa & Hayashi, 1989: 87–89 , fig. 15a–n.

Paradiopatra yasudai Imajima, 1999: 95–101 , figs 54 and 55. Imajima, 2003: 209–210.

Type material was unavailable for examination. The following description is based on four non-type specimens and the original description by Maekawa & Hayashi (1989).

Non-type material examined: NSMT Pol-107192, Japan, Sagami Bay , between 35.222°N, 139.568°E and 35.228°N, 139.572°E (four) .

Type locality: Pacific Ocean , Sea of Japan, Wakasa Bay, 75 m.

Diagnosis: First three pairs of parapodia with indistinctly bidentate pseudocompound falcigers with long pointed hoods; distal teeth of pseudocompund falcigers weakly developed; ventral cirri subulate on first two chaetigers; branchiae pectinate with four or five filaments, starting from chaetiger 6 and present on the 20–22 following chaetigers; subacicular hooks starting from chaetiger 8; peristomial cirri present.

Description: Three anterior ends and one complete specimen with 50 chaetigers, and regenerating posterior end of the body, were present among studied material. The widths of the specimens examined varying from 0.7 to 1.1 mm. Maekawa & Hayashi (1989) described the holotype as an incomplete specimen consisting of 26 chaetigers, 1.8 mm wide (including parapodia) and 8 mm long. All examined specimens stored in alcohol light brownish with transverse dark pigmented bands across dorsal side of anterior chaetigers.

Prostomium anteriorly rounded with paired ovoid and elongated frontal lips ( Fig. 81B ). Palps reaching chaetiger 1, lateral antennae reaching chaetiger 5, median antenna reaching chaetigers 3 or 4. Maekawa & Hayashi reported holotype with palps reaching chaetiger 2, lateral antennae reaching chaetiger 4, and median antenna reaching chaetiger 2. Ceratophores of lateral antennae with five or six rings, lacking lateral projections ( Fig. 81A, B ). Nuchal organs slightly curved and widely separated from each other. One pair of eyes present near the bases of lateral antennae. Peristomium as long as first chaetiger. Peristomial cirri present, shorter, or equal to peristomium ( Fig. 81A ).

First three pairs of parapodia modified, projecting laterally, directing slightly anteriorly ( Fig. 81B ). Prechaetal lobes rounded in all chaetigers; postchaetal lobes triangular to digitiform in first seven chaetigers, thereafter abruptly reducing. Dorsal cirri digitiform on all chaetigers. Ventral cirri subulate on first two chaetigers ( Fig. 81B, C ). Third pair of parapodia with reduced conical ventral cirri and transverse elongated glandular fields across the ventral side ( Fig. 81B, D ). Transverse elongated glandular pads starting from chaetiger 4, becoming triangular on chaetigers 8 or 9 ( Fig. 81B ).

First three pairs of parapodia with one or two dorsal simple capillary chaetae, and ventral fascicle of four pseudocompound falcigers ( Fig. 81C, D ). Falcigers with weakly developed slender bidentate distal appendages and long sharply pointed hoods ( Fig. 81H ). Simple limbate chaetae arranged in two fascicles starting from chaetiger 4 ( Fig. 81E ). Ventral fascicle of limbate chaetae replaced by paired simple bidentate subacicular hooks from chaetiger 8 ( Fig. 81F, I, J ). Pectinate chaetae with oblique distal margins and 20 or 21 teeth ( Fig. 81K ). Maekawa & Hayashi (1989) reported pectinate chaetae with 17 teeth in holotype. Neuroaciculae yellow with pointed tips, three or four per parapodium.

Branchiae pectinate, starting from chaetigers 5 or 6, and continuing to chaetigers 26–28 ( Fig. 81E– G ). First four or five pairs of branchiae single, reaching filaments 3–5 on median chaetigers, and decreasing in size and number of filaments posteriorly.

The jaw apparatus was not examined becasue of the low number of specimens available for examination. Maxillary formula according to Maekawa & Hayashi (1989) and Imajima (1999): Mx I = 1 + 1; Mx II = 5–7 + 7–9; Mx III = 6–10 + 0; Mx IV = 6–7 + 6–8; Mx V = 1 + 1.

A single known complete specimen with regenerating posterior region with pygidium bearing four very short anal cirri. Tubes absent in the material studied. Original description by Maekawa & Hayashi (1989) and later record by Imajima (1999) lack information about the shape and structure of the tubes.

Remarks: Maekawa & Hayashi (1989) reported P. yasudai as having falcate pseudocompound falcigers. Imajima (1999) re-examined the type material of P. yasudai and reported that bidentae distal appendages are present in all falcigers, but that teeth are very poorly developed and almost indistinct. We agree with Imajima in that all falcigers have bidentate appendages covered by paired long pointed hoods. Both teeth are very small but clearly separated from each other.

Paradiopatra yasudai is very close to P. quadriquspis in having two pairs of subulate ventral cirri, three pairs of parapodia with bidentate pseudocompound falcigers, and pectinate branchiae starting from chaetigers 6 or 7. It can be distinguished from the latter by the presence rather than the absence of eyes, having rather than lacking pigmented dorsal transverse bands in the anterior region, and origin of subacicular hooks strictly from chaetiger 8 rather than from chaetiger 9.

Distribution: Pacific Ocean, off Japan: Sagami Bay, Suruga Bay, Wakasa Bay, Tosa Bay, Tsushima Strait ( Fig. 82). Depth range 60–960 m ( Imajima, 1999).

Figures

Figure 81. Paradiopatra yasudai (NSMT Pol-107192): A, anterior end, dorsal view; B, anterior end, ventral view; C, parapodium of chaetiger 1, anterior view; D, parapodium of chaetiger 3, anterior view; E, parapodium of chaetiger 6, anterior view; F, parapodium of chaetiger 8, anterior view; G, parapodium of chaetiger 13, anterior view; H, bidentate pseudocompound falciger from chaetiger 1; I, subacicular hook from chaetiger 48; J, subacicular hook from chaetiger 8; K, pectinate chaeta from chaetiger 48.