Kainonereis peltifera, Conde-Vela & Wu & Salazar-Vallejo, 2018

Conde-Vela, Víctor Manuel, Wu, Xuwen & Salazar-Vallejo, Sergio Ignacio, 2018, Elisesione imajimai Jimi & amp; Eibye-Jacobsen & amp; Salazar-Vallejo 2018, sp. nov., Zoological Studies (Zool. Stud.) 57 (6), pp. 1-24 : 14-16

Kainonereis peltifera sp. n.

( Figs. 2 G-H; 6A-N)

urn:lsid:zoobank.org:act:AC77BBDB-F6B4-4F3A-886E-FC130054D350

Type material: Pacific Ocean, Mexico. Holotype LACM-AHF 7400 h male, paratypes LACM-AHF 7400 p male (1) and LACM-AHF 7400 p (2) females, R/ V Velero III, Sta. 748-37 (21°52'20"N, 105°51'30"W), Isla Isabel, Nayarit, Gulf of California , anchorage, 2 April 1937, collecting gear electric light, Coll. Allan Hancock Foundation.

Type locality: Isla Isabel, Gulf of California, Mexico.

Etymology: Named after the Latin word peltifer, - a, - um, meaning ‘carrying a pelta’, referring to the chaetigers 5-7 bearing flat, rounded discs. Also, pelta (Gr. πέλτη, a thin, rounded shield) is the stem of the Latin word peltatus (peltate), used to refer to a type of insertion of the petiole in the lamina of some leaves (e.g. in species of Nelumbo Adanson, 1763 or Umbilicus de Candolle, 1801 ); the central insertion of the stalk at the lower surface of the disc matches this kind of insertion.

Description: Holotype ( LACM-AHF 7400h) complete, male epitoke, anal cirri missing, 10 mm long, 0.6 wide, 55 chaetigers. Paratypes ( LACM-AHF 7400p) complete, male and females epitokes, anal cirri missing. Dissected paratype female, complete, 8 mm long, 0.5 mm wide at chaetiger 10, 50 chaetigers, few oocytes in coelom; dissected paratype male 10 mm long, 0.6 mm wide, 54 chaetigers, few whitish bundles of sperm in coelom. One paratype female with pharynx everted ( Fig. 6C ). Body off-white in males, yellowish in females, tapering posteriorly, no pigmentation pattern observed.

Prostomium wider than long, pentagonal, anterior margin entire, medial shallow groove present; one pair of antennae, not articulated; eyes black, ovate to reniform, anterior eyes slightly larger than posterior ones ( Figs. 6A, C ). Achaetous ring as long as first chaetiger; anterior cirri with distinct cirrophores, cirrostyles articulated, longest one reaching chaetigers 3-4 ( Fig. 6A ). Pharynx smooth ( Fig. 6C ); jaws dentate, cutting edge with nine teeth visible ( Fig. 6C ).

Body divided into two regions: 1) pre-natatory regions include chaetigers 1-14, sub-divided into three regions; 2) natatory region from chaetiger 15 to end of body.

First two chaetigers with neuroaciculae only, remaining with noto- and neuroaciculae. In chaetigers 1 and 2 ( Fig. 6D ), cirrophore of dorsal cirrus swollen basally, ovate, cirrostyle narrow, digitate, distinctly separated from base. Dorsal ligule as long as neuropodial postchaetal one, digitate. Acicular neuropodial ligule subconical, postchaetal lobe digitate, twice longer than acicular ligule; neuropodial ventral ligule digitate slightly longer than postchaetal lobe. Ventral cirrus pyriform, cirrostyle slightly distinct.

Notopodial dorsal ligules present from chaetiger 3 in females, from chaetiger 4 in males ( Fig. 6E ), as long as notopodial ventral ones; remaining structures similar as in first two chaetigers in both sexes.

In chaetigers 5-7 ( Fig. 6F ), dorsal discs elytriform, cirrostyle short, distinctly separated. Notopodial dorsal ligule as long as notopodial ventral one; both ligules tapering and separated by a short, rounded prechaetal lobe. Acicular neuropodial ligule subconical, as long as postchaetal lobe; neuropodial ventral ligule tapering, slightly longer than acicular neuropodial lobe. Ventral cirrus cirriform, shorter than neuropodial ventral ligule.

In chaetigers 8-14 ( Figs. 2G ; 6G ), dorsal and ventral cirri slender, cirriform; dorsal cirrus as long as notopodial dorsal ligule, ventral cirrus half as long as neuropodial ventral ligule. Notopodial and neuropodial lobes similar to those present in chaetigers 5-7.

Parapodia from 15 to end of body similarly modified throughout ( Figs. 2H ; 6H, I ). Dorsal cirrus smooth, slender, as long as notopodial dorsal ligule. Cirrophores of dorsal cirrus with two small basal, lateral lamellae, upper lamella longer than lower one; and one large, dorsal lamella, division between it and upper lamella sometimes inconspicuous. Both notopodial dorsal and ventral ligules digitate, subequal; both notopodial ligules separated by a large, rounded prechaetal lobe. Acicular neuropodial ligule enlarged, digitate; postchaetal lobe becoming into a lamella, longer than, to subequal as, and as wide as acicular neuropodial ligule; neuropodial ventral ligule digitate, medially inserted to acicular neuropodial ligule, shorter than it. Ventral cirrus cirriform, as long as acicular neuropodial ligule, with two basal, lateral lamellae.

Notochaetae homogomph spinigers; homogomph falcigers in chaetigers 3-7 in males, absent in females. Neurochaetae homogomph spinigers and heterogomph falcigers in supra-acicular fascicles; heterogomph spinigers and falcigers in sub-acicular fascicles.

Notopodial homogomph spinigers pectinate, teeth decreasing in size towards tips. Notopodial homogomph falcigers with falcate tips, teeth minute ( Fig. 6J ). Neuropodial heterogomph spinigers pectinate, teeth fine, decreasing towards tips ( Fig. 6L ). Neuropodial heterogomph falcigers pectinate, teeth minute, distal tooth stout, incurved and fused to blade ( Figs. 6K , M-N), sometimes inconspicuous; supra- and sub-acicular falcigers similar, both decreasing in size slightly towards posterior chaetigers.

Pygidium not modified (males or females), with two lobes; anal cirri lost.

Remarks: Hernández-Alcántara and Solís-Weiss (1991:254) likely recorded this as K. alata in the Gulf of California, because one of us ( SISV) confirmed its generic affinities in the early 1980s; but their material is lost, preventing its confirmation (Solís-Weiss pers. comm.). The type material for this new species was originally identified as ‘Nereid’ by Olga Hartman, and later as Nicon moniloceras by Kristian Fauchald (Leslie H. Harris pers. comm.), likely after the bare pharynx and number of ligules.

This is the only species for which both sexes are known, allowing for direct comparison of their morphology. Chamberlin (1919:197) thought that dorsal discs were only present in males because his specimens were all males; however, elytriform structures are also present in females of K. peltifera sp. n. Other typical sex-related differences are missing as the dissimilar number of chaetigers in non-natatory region, or presence of crenulated dorsal cirri and anal papillae in males. The main differences between sexes is that males have notopodial homogomph falcigers in chaetigers 3-7, and lack notopodial dorsal ligules in chaetiger 3, whereas in females there are no homogomph falcigers, but they have notopodial dorsal ligules in chaetiger 3. The species Typhlonereis gracilis Hansen, 1879 is similar to Kainonereis species in that it lacks notopodial dorsal ligules in first chaetigers, but in T. gracilis notopodial dorsal ligules and notochaetae are absent in first four chaetigers and if it is a sex-specific feature could not be determined ( Bakken 2003).

Specimens belonging to this species are quickly recognizable by the flat, rounded, delicate discs in chaetigers 5-7 in both sexes. Males of this species differ from those of K. alata and K. elytrocirra comb. n.: K. peltifera sp. n. has a distinct, falcate distal tooth in notopodial falcigers, and their postchaetal lamellae are longer than acicular neuropodial ligules; whilst in K. alata and K. elytrocirra comb. n., notopodial falcigers have almost blunt distal ends, and postchaetal lobes are shorter to subequal than acicular neuropodial ligules. Moreover, K. peltifera sp. n. has an enlarged anterior end, resembling K. alata and K. chamberlini sp. n., but K. peltifera sp. n. differs clearly from K. alata in having separate antennae and from the K. chamberlini sp. n. in the shape of dorsal discs.

Figures

Fig. 2. Drawings from parapodia of Kainonereis species. K. alata A, B (USNM 19386); K. chamberlini sp. n. C (UMML 22.1126), D (USNM 1422199); K. elytrocirra comb. n. E, F (MBMCAS A-44); K. peltifera sp. n. G, H (LACM-AHF 7400p); K. polaris comb. n. I, J (USNM 55514). (A) parapodium 11, anterior view; (B) parapodium 40, anterior view; (C) parapodium 11, anterior view; (D) parapodium 25, anterior view; (E) parapodium 12, anterior view; (F) parapodium 20, anterior view; (G) parapodium10, anterior view; (H) parapodium 22, anterior view; (I) parapodium 13, posterior view; (J) parapodium 30, posterior view. Scale bars: A, B = 50 µm; C-H = 0.1 mm; I-J = 0.2 mm. E redrawn from Wu and Sun (1979:109). All chaetae omitted.

Fig. 6. Kainonereis peltifera sp. n. A, B, holotype male (POLY-AHF 7400h); E, J-L, paratype male (POLY-AHF 7400p); C, D, F-I, M, N, paratype females (POLY-AHF 7400p). (A) anterior end, dorsal view; (B) close-up of chaetigers 5-7, dorsal view; (C) close-up of anterior end, dorsal view; (D) parapodium 1, anterior view; (E) parapodium 3, anterior view; (F) parapodium 6, anterior view; (G) parapodium 10, anterior view; (H) parapodium 22, anterior view; (I) parapodium 45, anterior view; (J) notopodial homogomph falciger, parapodium 3; (K) neuropodial sub-acicular falciger, parapodium 3; (L) neuropodial sub-acicular spiniger, parapodium 3; (M) neuropodial supra-acicular falciger, parapodium 10; (N) neuropodial sub-acicular falciger, parapodium 10. Scale bars: A, B, = 0.5 mm; C-I = 0.1 mm; J-N = 10 µm.