Aricidea (Acmira) blakei, León-González & Díaz-Castañeda & Hernández, 2025

Aricidea (Acmira) blakei sp. nov.

urn:lsid:zoobank.org:act:346CC7E7-44C4-4A11-8C6B-ED0AB8684FB7

Figures 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4

Type material

Holotype (UANL-8171), GoogleMaps 2 paratypes (UANL-8172), Bahía de los Angeles , Baja California, Gulf of California , Mexico, Station M3-2 , November 14, 2013, N28.89534 W113.50281, 17 m depth. GoogleMaps

Additional material

12 specimens. 1 specimen, (UANL-8173), Bahía de los Angeles, Baja California, Gulf of California, Mexico, Station M2-4, November 14, 2013, N28.90032 W113.48569, 17 m depth; 1 specimen, (UANL-8174), Station M4- 2, N28.89650 W113.51538, 14 m depth; 1 specimen, (UANL-8175), Station M5-4, N28.90727 W113.52895, 16 m depth; 1 specimen, (UANL-8176), Station M8-1, N28.94241 W113.55211, 10.8 m depth; 1 specimen, (UANL-8177), Station M8-3, N28.94241 W113.55211, 10.6 m depth; 1 specimen, (UANL-8178), Station M11-1, N28.97932 W113.54205, 12.8 m depth; 3 specimens, Station M11-2, (UANL-8179), N28.97932 W113.54205, 12.9 m depth; 4 specimens, (UANL-8180), Station M11-3, N28.97932 W113.54205, 11.1 m depth; 1 specimen, (UANL-8181), Station M12-1, N28.99071 W113.54576, 11.4 m depth.

Description

Holotype complete, 11 mm long (8–11 mm in paratypes), 0.5 mm wide (0.3–0.7 mm in paratypes) with 140 chaetigers (124–140 in complete paratypes). Color in preserved worms pale yellowish. Body cylindrical and robust, branchial region thicker than pre- and postbranchial regions ( Fig. 1A View FIGURE 1 ). First three segments with a median dorsal crest (mdc) ( Figs 1A–B View FIGURE 1 , 3B View FIGURE 3 , 4A View FIGURE 4 ), in specimen prepared for SEM, crest appears as a dorsally cleft elevation, whereas in specimens examined under light microscopy, the crest is an uncleaved elevation ( Figs 3A View FIGURE 3 , 4A View FIGURE 4 ). Prostomium subtriangular, wider than long, anterior margin rounded ( Figs 1A–B View FIGURE 1 , 3A View FIGURE 3 ). Eyes absent in all specimens. With a pair of crown-like ciliary bands (clcb) inserted in postero-lateral side of prostomium. A pair of ciliary slits (cs) located anteriorly to nuchal organs, semicircular in shape ( Fig. 1B–C View FIGURE 1 ). Antenna digitiform, short, extend back to mid part of first chaetiger, with discrete swollen base and small group of cilia surrounding base ( Fig. 2A View FIGURE 2 ). A pair of nuchal organs present, as diagonal, narrow, deep, short and slanted slits placed on dorso-lateral sides of posterior prostomium; dense internal ciliation not reaching outer margin of slits ( Figs 1A–B View FIGURE 1 , 2A View FIGURE 2 ).

A dorsal ciliary band present on mid-dorsal transversal line of each pre-branchial and branchial chaetiger: that of chaetiger #1 form a complete ciliary band with short cilia, that of chaetiger #2 divided in two small bands with short cilia, those of chaetiger #3 forming almost an entire band of medium length cilia. From chaetiger #5 to end of branchial region all ciliary bands are entire with very long cilia ( Fig. 1A View FIGURE 1 ). A pair of short dorsal ciliary bands (sdcb) present just posterior to base of each branchia ( Figs 1A View FIGURE 1 , 2B View FIGURE 2 ). Intersegmental ciliary bands not present.

Branchiae numbering 20 pairs in holotype (15–24 pairs in paratypes), starting on chaetiger #4, foliaceous with wide base, tapering towards distal part and digitiform tip, slightly longer in middle branchial region, last pair of branchiae shorter than others ( Fig. 1A View FIGURE 1 ); dense ciliary bands on both sides of branchiae from the basal part to subdistal region, bare distal part ( Figs. 1A View FIGURE 1 , 2B View FIGURE 2 , 4B View FIGURE 4 ); branchiae shorter than segment width. Branchiae length/wide: 254.9 μm/110.8 μm in anterior region (chaetiger #4); 376.8 μm/110.8 μm in middle region (chaetiger #11), 221.6 μm/55.4 μm in posterior region (chaetiger #23).

Notopodial papillae absent. Notopodial postchaetal lobes present in prebranchial region; short, conical on first two chaetigers ( Figs. 1B View FIGURE 1 , 3C View FIGURE 3 ); increasing in length and becoming stout, digitiform with asymmetrical swollen base on chaetiger #3 ( Figs. 1B View FIGURE 1 , 3D View FIGURE 3 , 4A View FIGURE 4 ); in the branchial region they increase in size until penultimate pair of branchiae, cirriform and thin tips ( Figs. 3E View FIGURE 3 , 4B View FIGURE 4 ), from last pair of branchiae onwards cirri are thin and long, filiform ( Figs. 3F–G View FIGURE 3 ). Neuropodial postchaetal lobe as hemispherical tubercle present from chaetigers 1 to 32.

Lateral sense organs present on all chaetigers, located between noto- and neuropodia, closest to and slightly behind postchaetal lobe ( Fig. 1B View FIGURE 1 ), with flexible cilia distinctly protruding from opening or embedded into pore.

Three main types of chaetae present: limbate, capillary and modified neurochaetae ( Figs. 2C–E View FIGURE 2 ). First 17 chaetigers with very numerous limbate chaetae, thick basally, attenuating towards distal part. In chaetiger #18 thin capillary chaetae appear, of lesser abundance. Modified neuropodial chaetae present from chaetiger #32 (21–36 in paratypes) to the last chaetigers, absent on 2 prepygidial segments, numbering 1–3 in each neuropodium. Anterior parapodia with only one modified neurochaeta 2.8 μm wide; median parapodia with three modified neurochaeta of different widths (inferior 5.6 μm wide, middle 2.8 μm wide, superior 8.4 μm wide); posterior parapodia with modified neurochaetae also of different widths (inferior 5.6 μm, middle 8.4 μm, superior 11.2 μm wide ( Figs. 2E View FIGURE 2 , 4C View FIGURE 4 ). Modified neurochaetae accompanied by thin capillary chaetae ( Fig. 2E View FIGURE 2 ); neurochaetae as curved hooks (90° degrees towards terminal region), with strong hood, hood with numerous fibrils and encompassing curved end of shaft except for small subdistal gap ( Fig. 2C View FIGURE 2 ); with a short, thin and fragile arista arising from terminal region, in most of the specimens the arista is missing, but insertion scar of where it was implanted is visible only using SEM imaging ( Fig. 2D View FIGURE 2 ).

Pygidium with three cirri, two inserted ventro-laterally, one cirrus placed mid-ventrally, short, all digitiform with the base wider, tapering towards the distal part ( Fig. 2F View FIGURE 2 ). Pygidium surrounded by a band of cilia, much denser in the dorsal region than in the ventral region, usually each cilium emerges from a pore, in ventral region with groups of cilia emerging from a single pore. Anal cirri with clusters of cilia emerging from pores ( Fig. 2F View FIGURE 2 ).

Etymology

Specific name is in honor of James A. Blake, a great American polychaetologist whose trajectory and excellent work on the knowledge of annelid polychaetes, including paraonids, made systematics easier and inspired many generations.

Remarks

The subgenus Acmira has traditionally been used to place species easily recognized by having a variety of modified neurochaetae ( Blake, 2019), which are thick or thin curved spines, with or without hoods, filaments, teeth or accessory spines. Before this work, Aricidea (Acmira) was represented by 34 species and two subspecies after Blake (2019), Barroso et al. (2020), Erdoğan-Dereli & Çinar (2020) and Plathong et al. (2020).

Aricidea (Acmira) blakei sp. nov., is mainly characterized by having a short digitiform antenna (not exceeding chaetiger 1) with a discrete swollen base; by possessing notopodial postchaetal lobes with asymmetrical base swollen in prebranchial and branchial region, changing gradually in size and shape from the first two chaetigers to the last pair of branchiae; last pair of branchiae being shorter than the rest; and by having curved hooks with a very strong hood and a fragile arista.

Aricidea (Acmira) blakei sp. nov., A. elongata Imajima, 1973 , Aricidea eximia Imajima, 1973 , Aricidea katzmanni Erdoğan-Dereli & Çinar, 2020 and Aricidea catherinae sensu Aguirrezabalaga (2012) belong to a small group of species characterized by possessing a rather slender antenna, reaching back to the 1 st, 2 nd- 3 rd chaetigers, without inflated median region; relatively long, tapered branchiae; modified neurochaetae which gradually become thicker towards the pygidium, with a thin terminal arista that easily breaks. Aricidea (Acmira) blakei sp. nov. differ from these species in terms of the following characteristics: (1) the shape and size of antenna: digitiform, short, extends back to mid part of first chaetiger in A. (A.) blakei sp. nov.; slender, long, extends to the anterior part of third chaetiger, basally swollen in A. (A.) eximia ; slender, long, extends back to second to fourth chaetiger in A. (A.) elongata ; digitiform, with more or less swollen region above mid-region, with cilia, extends to chaetiger 2 in A. (A.) katzmanni ; thicker in the middle zone, becomes attenuated and ends in a thin point, inserted slightly in front of the middle of the prostomium, long, extends to the chaetiger 3 in A. (A.) catherinae sensu Aguirrezabalaga 2012 . (2) The shape and size of last pairs of branchiae: last pair of branchiae shorter than the anterior ones but similar in shape in A. (A.) blakei sp. nov.; last two pairs of branchiae extremely long with filamentous distal part, each branchia is about two times as long as the former in A. (A.) eximia ; posterior four pairs of branchiae are noticeably longer and slender, each is longer than the width of the segment, and ends as slender filamentous tip in A. (A.) elongata ; last two pairs of branchiae are cylindrical, smaller than the previous ones, the last pair is the smallest and thinnest in A. (A.) katzmanni and A. (A.) catherinae sensu Aguirrezabalaga 2012 . (3) The shape of first two postchaetal notopodial lobes: conical in A. (A.) blakei sp. nov.; extremely small, barely visible in A. (A.) eximia ; cirriform in A. (A.) elongata and A. (A.) katzmanni ; digitiform in A. (A.) catherinae sensu Aguirrezabalaga 2012 . (4) Shape of the postchaetal notopodial lobe base in anterior parapodia: with asymmetrical swollen bases in A. (A.) blakei sp. nov., A. (A.) eximia and A. (A.) elongata , and with symmetrical bases in A. (A.) katzmanni and A. (A.) catherinae ; (5) The presence and shape of neuropodial lobe: absent in A. (A.) eximia and A. (A.) elongata ; as short ridges on chaetigers 1–11 in A. (A.) katzmanni ; as hemispherical tubercles in postbranchial region, from chaetigers 1–29 in A. (A.) catherinae sensu Aguirrezabalaga 2012 , and from chaetigers 1–32 in A. (A.) blakei sp. nov.