Kainonereis alata Chamberlin, 1919

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 : 6-9

publication ID	https://doi.org/ 10.6620/ZS.2018.57-06
persistent identifier	https://treatment.plazi.org/id/03BA684C-FFF0-FFCF-23FE-F605FBB0DC67
treatment provided by	Felipe
scientific name	Kainonereis alata Chamberlin, 1919
status

Treatment

Kainonereis alata Chamberlin, 1919 View in CoL

( Figs. 2 View Fig A-B; 3A-K)

Kainonereis alata Chamberlin 1919:197-202 View in CoL , Pl. 28, Figs. 6-8 View Fig View Fig View Fig , Pl. 29, Figs. 1-8 View Fig View Fig View Fig View Fig View Fig View Fig View Fig View Fig .

Type material: Pacific Ocean, Kiribati. Holotype USNM 19388 About USNM and paratypes USNM 19386 About USNM (5), all males, R/ V Albatross, Sta. H 3964 (25°49'43"N, 171°43'37"W), off Apaiang, Gilbert Islands, Kiribati, 3 January 1900, Coll. United States Fish Commission. GoogleMaps

Type locality: Off Abaiang (Apaiang), Kiribati, at surface.

Description: Holotype ( USNM 19388) complete, male epitoke, 8.5 mm long, 0.8 mm wide at chaetiger 10, 50 chaetigers; delicate, bent backwards, several parapodia previously removed. Paratypes ( USNM 19386) complete, male epitokes, 6-8 mm long, 1 mm wide at chaetiger 10, 50-54 chaetigers ( Fig. 3A View Fig ), presence of sperm in coelom. Body yellowish, tapering posteriorly ( Fig. 3A View Fig ), no staining pattern observed with green-methyl.

Prostomium as long as wide, pentagonal, anterior margin absent, medial shallow groove present; palps directed ventrally ( Figs. 3B, C View Fig ); eyes reddish, nearly rounded, anterior and posterior pairs overlapped, sometimes pigments faded off ( Fig. 3B View Fig ). Antennae basally fused in a faintly annulated stem with two distal smooth articles, half as long as the stem ( Figs. 3C, D View Fig ). Achaetous ring as long as first chaetiger; anterior cirri with distinct cirrophores, cirrostyles articulated, longest one reaching chaetiger 4 ( Fig. 3B View Fig ). Pharynx not everted; jaws enlarged, cutting edge with eight to nine teeth, faintly developed.

Body divided into two regions: 1) pre-natatory region 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 chaetigers with noto- and neuroaciculae. In chaetigers 1 and 2 ( Fig. 3E View Fig ), dorsal cirri swollen basally, tip narrow, digitate, distinctly separated from cirrophore. Dorsal ligule as long as neuropodial postchaetal one, digitate. Acicular neuropodial ligule rounded, postchaetal lobe digitate, twice longer than acicular ligule; neuropodial ventral ligule digitate, slightly longer than postchaetal lobe. Ventral cirrus pyriform, cirrostyle barely distinct.

Notopodial dorsal ligules absent in chaetiger 3 ( Fig. 3H View Fig ), present from chaetiger 4, as long as notopodial ventral ligule; remaining structures similar as in first two chaetigers.

In chaetigers 5-7 ( Fig. 3F View Fig ), dorsal disc petal-like, discs progressively larger, third one surpassing following segment; cirrostyle short, indistinctly separated from bases. Notopodial dorsal ligule as long as notopodial ventral one; both ligules tapering and separated by a short, digitate prechaetal lobe. Acicular neuropodial ligule subconical, as long as postchaetal lobe; neuropodial ventral ligule tapering, as long as acicular neuropodial lobe. Ventral cirrus cirriform, shorter than neuropodial ventral ligule.

In chaetigers 8-14 ( Figs. 2A View Fig ; 3G View Fig ), dorsal cirrus digitate, as long as notopodial dorsal ligule. Both notopodial dorsal and ventral ligules digitate, subequal; both notopodial ligules separated by a large, rounded prechaetal lobe. Acicular neuropodial ligule subconical, slightly shorter than notopodial ventral ligule; postchaetal lobe rounded, half as long as acicular neuropodial ligule; neuropodial ventral ligule digitate, slightly swollen basally, as long as acicular neuropodial ligule. Ventral cirrus digitate, shorter than neuropodial ventral ligule.

Parapodia from 15 to end of body similarly modified throughout ( Figs. 2B View Fig ; 3I View Fig ). Dorsal cirrus smooth, slender, as long as notopodial dorsal ligule. Basal portion of dorsal cirrus with two small basal lamellae, upper lamella slightly longer than lower one; and one large, dorsal lamella, division between it and upper lamella conspicuous. 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 enlarged into a lamella, longer and wider than acicular neuropodial ligule; neuropodial ventral ligule digitate, medially inserted to acicular neuropodial ligule, shorter than it. Ventral cirrus cirriform, shorter than acicular neuropodial ligule, with two basal lamellae.

Notochaetae homogomph spinigers; homogomph falcigers in chaetigers 3- 7. 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 tip. Notopodial homogomph falcigers with minute falcate tips, teeth minute ( Fig. 3J View Fig ). Neuropodial heterogomph spinigers pectinate, teeth fine, decreasing towards tip. Heterogomph falcigers pectinate, teeth minute, distal tooth stout, incurved, fused to blade; supra- and sub-acicular falcigers similar.

Pygidium not modified, with two lobes ( Fig. 3K View Fig ); anal cirri as long as last four chaetigers, lost in most specimens ( Fig. 3K View Fig ).

Remarks: The original description is long, detailed and accurate, but additional features have been included herein for improvement. There are, however, some differences to the original description: first, two chaetigers are not “biacicular”, but only have neuroaciculae; achaetous ring is dorsally as long as first chaetiger (only longer than it ventrally); the original illustration of the fourth chaetiger ( Chamberlin 1919, Pl. 29, Fig. 1 View Fig ) is inverted; the parapodia in chaetigers 8-14 do not resemble those present in most-anterior ones, they differ in the shape of ligules and cirri; the natatory region begins at chaetiger 15, instead of 12; the color of the notopodial homogomph falcigers are not black or dark brown, but lighter as remaining chaetae.

Kainonereis alata View in CoL is easily separated from remaining species because it has antennae with a ringed stem and bifurcated tips, and palps markedly directed downwards as is the case in some Platynereis species ( Read 2007). The antennae of K. alata View in CoL are markedly modified by being fused basally, such that the superficially annulated prolongation corresponds with the fused ceratophores, whereas the terminal, diverging appendages correspond to ceratostyles. Because of this, these antennae are herein referred to as basally fused antennae ( Figs. 3C, D View Fig ). This is a unique structure, as Chamberlin (1919:194) highlighted in his key (and we did in ours), but being restricted to a single species, this feature is herein regarded as a specific feature. The basally fused antennae likely are male-specific, but, as females were not found, this cannot be corroborated.

As in all males examined, the notopodial dorsal ligules appear from chaetiger 4 instead of chaetiger 3. This has been previously reported in some species, like Sinonereis heteropoda Wu and Sun, 1979 View in CoL and Typhlonereis gracilis Hansen, 1879 View in CoL ( Wu and Sun 1979, Bakken 2003), but without sex distinctions; here, however, it is regarded as a male sexual feature in Kainonereis View in CoL . The notopodial homogomph falcigers in males of K. alata View in CoL are wider and shorter than those present in the males of K. elytrocirra View in CoL comb. n. and K. peltifera View in CoL sp. n. The shape of the dorsal discs of K. alata View in CoL is similar to K. polaris View in CoL comb. n., but they are shorter in K. alata View in CoL than in K. polaris View in CoL comb. n. Further differences are included under the remarks sections of the remaining species.