Laeonereis watsoni de León-González, Méndez and Navedo, 2017

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 : 434-438

Laeonereis watsoni de León-González, Méndez and Navedo, 2017

( Figures 6 , 25 (a–o))

Laeonereis watsoni de León-González et al. 2017: 2–3 , figs 1A–I, 2A–E.

Type material

North Pacific Ocean, Mexico. Paratype UANL 7844 , Estero de Urias, Mazatlan, Sinaloa, 5 October 2014, Coll . Orlando Obeso . Paratypes LACM-AHF Poly 9314 (5), pond 18, acuicola Don Jorge shrimp farm, Estero de Urias , Mazatlan , Sinaloa, 23.151389°N 106.289722°W, 0.5 m, Coll . N . Mendez, J.G . Navedo , 5 October 2014 .

Additional material

UANL 8117 (21), Estero de Urias, Mazatlan , Sinaloa, 5 October 2014, Coll . Orlando Obeso .

Description

Paratype (UANL 7844) complete, 12 mm long, 0.7 mm wide at chaetiger 10, 75 chaetigers ( Figure 25 (a)). Body pale, brown pigment present in prostomium, palpophores and anterior chaetigers, disappearing towards middle chaetigers, some brown spots on dorsal surface of posterior chaetiger and in the margin of pygidium ( Figure 25 (a–e)).

Prostomium hexagonal, as long as wide, anterior margin shallowly cleft, dorsal groove wide and reaching the anterior pair of eyes ( Figure 25 (b,c)); antennae digitiform, 0.5–0.8 times as long as dorsal groove ( Figure 25 (b,c)); eyes black, rounded, the two pairs subequal ( Figure 25 (b,c)). Achaetous ring as long as first chaetigers ( Figure 25 (b,c)); four pairs of anterior cirri, cirrophores conspicuous, longest pair reaching chaetiger 3 ( Figure 25 (b,c)).

Pharynx dissected. Maxillary ring: I = 1–1 tuft of verticillate rod-like papillae; II = 1–1 tuft of verticillate rod-like papillae; III = 3 tufts of verticillate rod-like papillae; IV = 1–1 tuft of verticillate rod-like papillae. Oral ring: V = 0; VI = 1–1 triangular papilla; VII–VIII = one ridge row with 5 rounded papillae, 1 papilla on each A–C region.

Pattern of pedal glands. UpG elliptical and smaller than MeG in anterior chaetigers, becoming subequal in middle chaetigers. LoG elliptical and several times larger than UpG in anterior chaetigers, becoming smaller in middle chaetigers. MeG rounded and slightly larger than PoG in anterior chaetigers, becoming subequal in middle chaetigers. PoG subequal in anterior and middle chaetigers.

First two chaetigers with neuroaciculae only; remaining ones with both noto- and neuroaciculae. In first two chaetigers ( Figure 25 (l)), dorsal cirri subconical. Dorsal ligules subconical, blunt, as long as wide, 5 times longer than dorsal cirri, twice as long as neuroacicular ligules. Neuroacicular ligules digitiform, 1.6 times wider than long; postchaetal lobes digitiform, 1.5 times longer than wide, twice as long as neuroacicular ligules, 1.3 times longer than dorsal ligules, 1.2 times longer than neuropodial ventral ligules; neuropodial ventral ligules digitiform, 2.5 times wider than long, 2.7 times longer than ventral cirri. Ventral cirri subconical.

In anterior chaetigers ( Figure 25 (m)), dorsal cirri linguiform. Notopodial dorsal ligules subconical, 1.8 times wider than long, 3.5 times longer than dorsal cirri; prechaetal lobes digitiform, as long as wide, 1.2 times longer than notopodial dorsal ligules; notopodial ventral ligules subconical, blunt, 1.2 times longer than wide, 1.6 times longer than prechaetal lobes. Neuroacicular ligules subconical, 1.2 times wider than long; postchaetal lobes digitiform, as long as wide, 1.3 times longer than neuroacicular ligules, 1.5 times longer than neuropodial ventral ligules; neuropodial ventral ligules subconical, blunt, 2.5 times wider than long, 4 times longer than ventral cirri. Ventral cirri subconical.

In middle chaetigers ( Figure 25 (n)), dorsal cirri linguiform. Notopodial dorsal ligules subconical, twice as wide as long, 3.6 times longer than dorsal cirri; prechaetal lobes absent; notopodial ventral ligules subconical, 1.4 times longer than wide, 1.5 times longer than notopodial dorsal ligules. Neuroacicular ligules subconical, 1.2 times wider than long, 1.2 times longer than notopodial ventral ligules; postchaetal lobes absent; neuropodial ventral ligules digitiform, 4 times wider than long, 7 times longer than ventral cirri. Ventral cirri subconical.

In posterior chaetigers ( Figure 25 (o)), dorsal cirri linguiform. Notopodial dorsal ligules subconical, 1.2 times wider than long, 3 times longer than dorsal cirri, as long as notopodial ventral ligules, becoming shorter than towards posteriormost chaetigers; prechaetal lobes absent; notopodial ventral ligules subconical, twice as long as wide, 3 times longer than neuroacicular ligules. Neuroacicular ligules subconical, 1.3 times longer than wide, 3.2 times longer than neuropodial ventral ligules; postchaetal lobes absent; neuropodial ventral ligules subconical, 7.3 times wider than long, 7–8 times longer than ventral cirri. Ventral cirri subconical.

Notochaetae homogomph spinigers. Neurochaetae homogomph spinigers in supraacicular fascicles, homogomph spinigers and falcigers in sub-acicular fascicles; subacicular homogomph falcigers absent in anterior chaetigers.

Notopodial and neuropodial spinigers pectinate, minute teeth, teeth decreasing in size towards distal end ( Figure 25 (f–h)). Neuropodial homogomph falcigers pectinate, minute teeth, distal tooth stout and hook-like, 12 times longer than wide, length of blades similar along body ( Figure 25 (i–k)).

Pygidium funnel-shaped, margin crenulated ( Figure 25 (d,e)); anal cirri cirriform, 3 times longer than width of pygidium ( Figure 25 (d,e).

Remarks

The original and current descriptions agree well; however, some additional features are added to improve the original description and standardise it with the current ones. The authors argued that L. watsoni can be separated from L. brunnea , another species from the Pacific Ocean, by the following features: anterior margin cleft in L. watsoni and entire in L. brunnea ; dorsal cirri 2.5 times longer than ventral ones in posterior chaetigers in L watsoni and twice as long as in L. brunnea ; blades of falcigers 9 times longer than wide in L. watsoni and 5–6 times longer than wide in L. brunnea ; pygidium brown-pigmented in L. watsoni and pale in L. brunnea . The examination of the available type materials showed that the anterior margin of the prostomium is shallowly cleft in L. brunnea as in L. watsoni ; we cannot confirm whether pigmentation is absent in the pygidium of L. brunnea because the specimens we examined are posteriorly incomplete, but Hartmann-Schröder (1959) described the ventral side of the pygidium as ‘ gleichmässig gefärbt ’ (translation: evenly coloured). Also, de León-González et al. (2017) highlighted differences in the number of papillae in areas I, II and IV, and the number of teeth in jaws of these species; the number of papillae in L. brunnea cannot be corroborated based on the difficulty of observing the papillae in the examined specimens, but the number of teeth in the jaws agrees with the number found in the paratypes ( Figure 5 (g)).

Additional differences between Laeonereis watsoni and L. brunnea are as follows: anterior chaetigers of L. brunnea have neuropodial supra-acicular falcigers, whereas in L. watsoni they are absent; in anterior chaetigers of L. watsoni , the notopodial prechaetal lobes are 1.2 times longer than notopodial dorsal ligules, whereas in L. brunnea they are half as long; in middle chaetigers of L. watsoni , the notopodial ventral ligules are 1.5 times longer than the notopodial dorsal ones, whereas in L. brunnea they are half as long; in posterior chaetigers of L. watsoni , the notopodial dorsal ligules are 3 times longer than dorsal cirri, whereas in L. brunnea they are 2.4 times longer; in L. watsoni , the neuropodial supra-acicular homogomph falcigers are absent, whereas in L. brunnea they are present. Laeonereis watsoni can be easily distinguished from the third species from the Pacific Ocean, L. orensanzi comb. nov.: in L. watsoni , the notopodial dorsal ligules are subconical and shorter than notopodial ventral ligules along the body, whereas in L. orensanzi comb. nov. they are ensiform and several times longer than along the body; additional differences are that in L. orensanzi comb. nov. the teeth of the jaws are ensheathed and the neuropodial homogomph falcigers are 9–10 times longer than wide, whereas in L. watsoni the teeth are uncovered and falcigers are 12 times longer than wide.

Key to species of Laeonereis Hartman, 1945

1. Medial chaetigers with notopodial dorsal ligules as long as or longer than notopodial ventral ligules ............................................................................................................................................ 2

- Medial chaetigers with notopodial dorsal ligules shorter than notopodial ventral ligules 5

2. Medial chaetigers with notopodial dorsal ligules wider than long .......................................... 3

- Medial chaetigers with notopodial dorsal ligules longer than wide ....................................... 4

3. Medial chaetigers sub-acicular falcigers with blades 10–11 times longer than wide; anterior chaetigers sometimes with neuropodial supra-acicular falcigers ............................ ......................................................... L. brunnea Hartmann-Schröder 1959 (La Paz, El Salvador)

- Medial chaetigers’ sub-acicular falcigers with blades 13–14 times longer than wide; anterior chaetigers without neuropodial supra-acicular falcigers ............................................. ..................................................................................... L. culveri ( Webster 1879) (New Jersey, USA)

4. Medial chaetigers’ sub-acicular falcigers with blades 9–10 times longer than wide; jaws with teeth ensheathed ............................................................................................................................................................ ........... L. orensanzi ( de León-González and Trovant 2013) comb. nov. (Esmeraldas, Ecuador)

- Medial chaetigers’ sub-acicular falcigers with blades 14–15 times longer than wide; jaws with teeth uncovered .................................................. L. longula sp. nov. ( Georgia, USA)

5. Medial chaetigers with notopodial dorsal ligules longer than neuroacicular ligules .. 6

- Medial chaetigers with notopodial dorsal ligules shorter than neuroacicular ligules .... 7

6. Prostomial dorsal groove shallow, 1.5 times wider than antennal bases; medial chaetigers with neuropodial ventral ligules 4.0–4.5 times longer than ventral cirri ...................... ......................................................................... L. pandoensis ( Monro 1937) (Canelones, Uruguay)

- Prostomial dorsal groove deep, half as wide as antennal bases; medial chaetigers with neuropodial ventral ligules 5–6 times longer than ventral cirri ................................................. ........................................................................................... L. acuta ( Treadwell 1923) (Santos, Brazil)

7. Anterior chaetigers with notopodial prechaetal lobes 1.2 times longer than notopodial dorsal ligules .............. .............. L. watsoni de León-González et al. 2017 (Sinaloa, Mexico)

- Anterior chaetigers with notopodial dorsal ligules twice as long as notopodial prechaetal lobes ............................................. ............................................. L. nota ( Treadwell 1941) (Texas, USA).

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 25. Laeonereis watsoni de León-González et al. 2017. (a–b, e–o), paratypes (UANL 7844); (c), paratype (LACM-AHF Poly 9314); (d), non-type (UANL 8117). (a) whole specimen, dorsal view; (b) anterior end, dorsal view; (c) anterior end, dorsal view; (d) posterior end, dorsal view, (e) posterior end, dorsal view; (f), notopodial homogomph spiniger, chaetiger 11; (g) supra-acicular homogomph spiniger, chaetiger 11; (h), sub-acicular homogomph spiniger, chaetiger 11; (i) sub-acicular homogomph falciger, chaetiger 11; (j) sub-acicular homogomph falciger, chaetiger 26; (k) sub-acicular homogomph falciger, chaetiger 63; (l) chaetiger 2, right parapodium; (m) chaetiger 11, right parapodium; (n) chaetiger 26, right parapodium; (o) chaetiger 63, right parapodium. Scale bars: a– d = 0.5 mm; e = 0.25 mm; f–k = 10 µm; l–o = 0.1 mm.