Laeonereis orensanzi ( de León-González and Trovant, 2013 ) Conde-Vela, 2021

Conde-Vela, Víctor M., 2021, Revision of Laeonereis Hartman, 1945 (Annelida: Phyllodocida: Gymnonereidinae), with a review of shaft morphology in nereidids, Journal of Natural History 55 (7 - 8), pp. 381-455 : 425-428

Laeonereis orensanzi ( de León-González and Trovant, 2013) comb. nov.

( Figures 5 (c,d,j), 6, and 21(a–n))

Nicon orensanzi de León-González and Trovant 2013: 70–71 , figs 2A–G, 3A–F.

Type material

North Pacific Ocean, Ecuador. Holotype LACM-AHF Poly 4999, paratype LACM-AHF Poly 5000 and paratype UANL 7840 , Esmeraldas, Bunche , 0.650550°N 80.065278°W, intertidal, low energy beach, very fine sand, hand, 21 March 2009, Coll. B. Trovant, S. Tineo.

Description

Holotype ( LACM-AHF Poly 4999) incomplete, 16 mm long, 0.5 mm wide at chaetiger 10, 82 chaetigers ( Figure 21 (a)); paratype ( LACM-AHF Poly 5000) incomplete, 15 mm long, 0.7 mm wide at chaetiger 10, 50 chaetigers. Body pale, anterior end slightly translucent ( Figure 21 (b,c)), no pigmentation observed, some greenish and yellowish spots due to the gut content ( Figure 21 (a)).

Prostomium hexagonal, wider than long, anterior margin cleft, dorsal groove deep and reaching the anterior pair of eyes ( Figure 21 (b,c)); antennae digitiform, 0.5–0.8 times as long as dorsal groove ( Figure 21 (b,c)); eyes reddish, rounded, the two pairs subequal ( Figure 21 (b,c)). Achaetous ring as long as first chaetiger ( Figure 21 (b,c)); four pairs of anterior cirri, cirrophores inconspicuous, longest pair of cirri reaching end of chaetiger 1 ( Figure 21 (b,c)).

Pharynx dissected. Jaws brown, cutting edge completely dentate, 13–14 teeth, all teeth ensheathed ( Figure 21 (d)). Papillae in maxillary ring inconspicuous. Papillae in area VI inconspicuous, some rounded papillae observed in areas VII–VIII.

Pattern of pedal glands ( Figure 6 ). UpG elliptical and smaller than MeG in anterior chaetigers, becoming larger than MeG in middle chaetigers. LoG absent in both anterior and middle chaetigers. MeG oblong and twice larger than PoG in middle chaetigers, becoming rounded and half as large as PoG in middle chaetigers. PoG becoming larger towards middle chaetigers.

First two chaetigers with neuroaciculae only; remaining ones with both noto- and neuroaciculae. In first two chaetigers ( Figure 21 (e)), dorsal cirri linguiform. Dorsal cirri digitiform, as long as wide, twice as long as dorsal ligules, 1.2 times longer than neuroacicular ligules. Neuroacicular ligules subconical, blunt, as long as neuropodial ventral ligules; postchaetal lobes digitiform, 1.3 times longer than wide, twice as long as neuroacicular ligules; neuropodial ventral ligules digitiform, 2.2 times wider than long, twice as long as ventral cirri. Ventral cirri digitiform.

In anterior chaetigers ( Figure 21 (f)), dorsal cirri linguiform. Notopodial dorsal ligules digitiform, as long as wide, 3.5 times longer than dorsal cirri, as long as notopodial ventral ligules; prechaetal lobes rounded, small, quickly disappearing towards middle chaetigers; notopodial ventral ligules subconical, 1.2 times longer than wide, 1.5 times longer than neuroacicular ligules. Neuroacicular ligules subconical, as long as wide, subequal to postchaetal lobes, 1.6 times longer than neuropodial ventral ligules; postchaetal lobes subconical, as long as wide; neuropodial ventral ligules digitiform, 2.8 times wider than long, twice as long as ventral cirri. Ventral cirri digitiform.

In middle and posterior chaetigers ( Figure 21 (g–i)), dorsal cirri linguiform. Notopodial dorsal ligules ensiform to cirriform, 2.5 times longer than wide, 4 times longer than dorsal cirri and becoming 3.5–3 times longer than in posterior chaetigers, 2.2 times longer than notopodial ventral ligules; prechaetal lobes absent, notopodial papillae present; notopodial ventral ligules subconical, 1.6 times longer than wide, as long as neuroacicular ligules. Neuroacicular ligules subconical, as long as wide, 8 times longer than neuropodial ventral ligules; postchaetal lobes absent; neuropodial ventral ligules subconical, 8 times wider than long, tip disappearing towards posterior chaetigers, 3 times longer than ventral cirri, becoming 6–7 times longer than in posterior chaetigers. Ventral cirri digitiform.

Notochaetae homogomph spinigers. Neurochaetae homogomph spinigers in supraacicular fascicles, homogomph spinigers and falcigers in sub-acicular fascicles; subacicular homogomph falcigers appearing from about chaetiger 10.

Notopodial and neuropodial homogomph spinigers pectinate, minute teeth ( Figure 21j–l ); supra-acicular spinigers with proximal teeth slightly coarser than in remaining ones ( Figure 21j–l ). Neuropodial homogomph falcigers pectinate, minute teeth, distal tooth stout and hook-like, blades 9–10 times longer than wide in anterior chaetigers, becoming slightly longer towards posterior chaetigers ( Figure 21 (m,n)).

Pygidium unknown.

Remarks de León-González and Trovant (2013) placed this species in the genus Nicon Kinberg, 1865 , mainly because of the absence of pharyngeal ornamentation; the authors amended the available diagnosis of the genus ( Hutchings and Reid 1990), adding the presence or absence of notopodial prechaetal lobes, and the absence or presence of neuropodial sesquigomph falcigers and simple chaetae. Based on the presence of notopodial prechaetal lobes, de León-González and Trovant (2013) formed two groups, where the species having prechaetal lobes include N. aestuarensis Knox, 1951 , N. japonicus Imajima, 1972 , N. polaris Hartman, 1967 , N. rotunda Hutchings and Reid, 1990 , N. sinica Wu and Sun, 1979 and N. orensanzi . Of them, Nicon polaris has been transferred to Kainonereis ( Conde-Vela et al. 2018) based on the presence of dorsal discs in chaetigers 5–7, and N. sinica is now regarded as the atoke stage of Sinonereis heteropoda Wu and Sun, 1979 based on parapodial and chaetal features ( Conde-Vela and Wu 2019). Among these species, N. orensanzi is the only species having elongated notopodial dorsal ligules, subacicular sesquigomph falcigers, lacking supra-acicular falcigers and lacking sub-acicular heterogomph falcigers ( de León-González and Trovant 2013); the authors stated heterogomph spinigers are present in supra-acicular fascicles, but they were not found in the material examined here.

After examination of the type material of the type species of Nicon , N. pictus Kinberg, 1865 , and comparison with L. culveri , it is demonstrated, based on parapodial and chaetal features, that Nicon orensanzi is a species of Laeonereis , and the new combination Laeonereis orensanzi is proposed. Further comments about differences between Laeonereis and Nicon species are made in the Remarks for the genus, above. To observe the pharynx under the light microscope, specimens of L. orensanzi comb. nov. were stained with Shirlastain, and then with methyl green. No papillae were found in sections of the pharynx corresponding to the maxillary ring, but some rounded papillae were found in the sections corresponding to the areas VII–VIII ( Figure 5c–d ), as in the case of L. brunnea . This procedure was performed with small specimens of L. nota from Chetumal Bay, and no papillae were identified. Mazurkiewicz (1975) noted that papillae in L. culveri are visible from the 20-chaetiger stage, but neither the method for observing them nor the number of papillae and their arrangement were detailed. Because the pharynx is often not everted, and therefore papillae are difficult to observe in small specimens or absent in early stages, using the presence of papillae as the main diagnostic feature in Laeonereis is avoided, and the parapodial and chaetal features mentioned above are used instead.

Laeonereis orensanzi comb. nov. differs from the remaining Laeonereis species (excepting L. longula sp. nov.) in the following features: notopodial dorsal ligules of L. orensanzi comb. nov. are ensiform and several times longer than notopodial ventral ligules along the body, whereas in the remaining Laeonereis species they are subconical or digitiform, and notopodial dorsal ligules become subequal to or shorter than notopodial ventral ones; in L. orensanzi comb. nov., the jaws have ensheathed teeth along the cutting edge, whereas in the remaining Laeonereis species , they are not ensheathed. The size of the blades of sub-acicular homogomph falcigers is similar to that of L. brunnea , but the latter species have supra-acicular falcigers, whereas in L. orensanzi comb. nov., they are absent. The differences from the most closely related species, L. longula sp. nov., are detailed in the Remarks for that species.

Figures

Figure 5. Foregut, papillae and jaws in Laeonereis species. (a) non-type specimen of L. acuta (ECOSUR- P3102), ventral dissection; (b) non-type specimen of L. pandoensis (ECOSUR-P3103), dorsal dissection; (c) and (d) rounded papillae in area VIII from paratype of L. orensanzi comb. nov. (UANL 7840); (e) rodlike, verticillate papillae from syntype of L. culveri from area IV (USNM 541); (f) everted pharynx from paratype of L. longula sp. nov. (USNM 1490792), labels indicate papillae on the pharyngeal areas; (g) left jaw of the paratype of L. brunnea (USNM 43404), dorsal view; (h) left jaw of the syntype of L. culveri (USNM 541), dorsal view; (i) left jaw of the paratype of L. longula sp.nov. (USNM 1490792), dorsal view; (j) left jaw of L. orensanzi comb. nov. (UANL 7840), dorsal view; (k) left jaw of non-type of L. pandoensis (ECOSUR-P3103), dorsal view. Dark areas in (a) and (b) are due to remnants of Shirlastain staining; (f) is stained with methyl green. Scale bars: a, b = 0.5 mm; c–e, j = 25 µm; f–i, k = 0.1 mm. Abbreviations:Es, oesophagus; Jw, jaw; Pa, papilla; Ph, pharynx; Pp, palpophore; Ps, palpostyle.

Figure 6. Arrangement of pedal glands in Laeonereis species. Abbreviations: DoG = dorsal gland; LoG = lower distal pedal gland; MeG = medial pedal gland; PrG = proximal pedal gland; UpG = upper distal pedal gland.

Figure 21. Laeonereis orensanzi (de León-González and Trovant, 2013) comb. nov. (a–b, e–n), holotype (LACM-AHF Poly 4999); (c–d), paratype (UANL 7840) (a) whole specimen, dorsal view; (b) anterior end, dorsal view; (c) anterior end, dorsal view; (d) right jaw, dorsal view; (e) chaetiger 2, right parapodium; (f) chaetiger 13, right parapodium; (g) chaetiger 30, right parapodium; (h) chaetiger 60, right parapodium; (i) chaetiger 82, right parapodium; (j) notopodial homogomph spiniger, chaetiger 13; (k) supra-acicular homogomph spiniger, chaetiger 13; (l) sub-acicular homogomph spiniger, chaetiger 13; (m) sub-acicular homogomph falciger, chaetiger 13; (n) sub-acicular homogomph falciger, chaetiger 30. Scale bars: a = 1 mm; b–d = 0.25 mm; e–i = 50 µm; j–n = 5 µm.