Amakusanthura camiguinensis Shiraki and Kakui, 2025

Amakusanthura camiguinensis Shiraki and Kakui sp. n.

( Figures 2–7 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 )

Material examined

Holotype. NMCR 99224 (12 slides and 1 vial), female lacking oostegites, 7.66 mm, coral rubble covered algae, 1–2 m depth, Brgy. Liong ( 9.078806°N, 124.766306°E), Guinsiliban , Camiguin Island, Philippines, 10 March 2024 GoogleMaps . Holotype: ICHUM9013 View Materials (6 slides and 1 vial), female lacking oostegites, collection data same as for holotype; NMCR 99221 (4 slides and 1 vial), female lacking oostegites, collection data same as for holotype; ICHUM9014 View Materials (1 vial), female lacking oostegites, 8.91 mm, intertidally, same sampling site and date as holotype; NMCR 99222 (3 slides and 1 vial), manca, collection data same as for holotype GoogleMaps .

Diagnosis

Body with brown dotted pigmentation dorsally. Telson with several (4–11) long simple setae on

Article 2 of mandibular palp with one to three simple setae and article 3 of that with two to three Description of female based on holotype

Body ( Figures 2 View Figure 2 and 3A–E View Figure 3 ) slender, 11.48 times longer than wide, pale and with several dorsal spots from head through pleonites. Head ( Figure 3A View Figure 3 ) length 1.22 times head width; rostrum not reaching anterolateral lobes; eyes dorsolateral, brown, length 0.16 times head length. Pereonites ( Figure 3A–C, E View Figure 3 ) with length ratio 1.39:1.43:1.19:1.50:1.46:1.28:0.90 relative to head length. Pleonites ( Figure 3D View Figure 3 ) together slightly longer than wide, length 1.18 times width, pleonites 1–3 free and

4 and 5 fused dorsally. Pleonite 6 distinct from telson dorsally, concave on mid-posterior edge. ( Figure 5H View Figure 5 ) linguiform, with length (from basal narrowest point to apical tip) 1.80 times width,

at apical edge, with two plumose sensory setae on apical tip; three, two, and two pairs of long setae on surface, on posterolateral margin, and on apical tip, respectively, and 45 short simple proximal part with two statocysts.

Antennula ( Figure 3F View Figure 3 ) with three peduncular and three flagellar articles. Peduncular article 1 longest five plumose sensory setae and three outer simple setae; article 2 with three distal plumose sensory and five outer long simple setae; article 3 with three distal long simple setae and four distal short setae. Flagellar article 1 with simple seta; article 2 with distal simple seta; article 3 with three aesthetascs four distal simple setae.

Antenna ( Figure 3G View Figure 3 ) with five peduncular articles and four flagellar articles. Peduncular article 1

with simple seta; article 2 with seven simple setae; article 3 with three inner simple setae; article 4 with plumose sensory seta and four simple setae; article 5 with three distal plumose sensory setae and six setae. Flagellar articles 1–4 with numerous simple setae.

Mandible ( Figure 3H View Figure 3 ) with 3-articulate palp. Palp article 1 with simple seta; article 2 longest, simple setae; article 3 with four membrane-like processes and two distal spiniform setae. Incisor cusps. Lamina dentata with four denticulations. Molar round.

Maxilla ( Figure 3I View Figure 3 ) slender, with seven teeth.

Maxilliped ( Figure 3J View Figure 3 ) with 3-articulate palp. Palp article 1 trapezoidal, with inner simple seta; longest, with six inner and one outer simple setae; article 3 oblique, with five inner simple setae tapering, slightly exceeding distal margin of palp article 1. Epipod lost during dissection.

HISTORY

(B) pereonites 2 and 3 in dorsal view; (C) pereonites 4–7 in dorsal view; (D) pleon in dorsal view; (E) lateral view antennula; (G) left antenna; (H) left mandible; (I) right maxilla; (J) left maxilliped. Scale bars: A–E = 1 mm; F–J =

ventral simple setae. Palm weakly stepped, with 11 simple setae. Dactylus with ventrodistal spiniform and one ventral, three ventrodistal, and four inner distal simple setae. Unguis nearly as long as naked.

Pereopod 2 ( Figure 4B View Figure 4 ) narrower than pereopod 1. Basis with three dorsal plumose sensory setae simple setae. Ischium with two dorsal and two ventrodistal long simple setae and 12 short simple Merus with four dorsal long, one outer short, and 12 ventral simple setae. Carpus triangular, with short spiniform seta and four ventral simple setae. Propodus with ventrodistal membrane-like ventrodistal spiniform seta with sensory bristle sensu Negoescu (1994), ventral short spiniform seta distal plumose sensory seta, and 15 dorsal, one mid-outer distal, and 17 ventral simple setae. Dactylus one ventral, two ventrodistal, and five inner distal simple setae. Unguis about two-fifths dactylus naked.

Pereopod 3 ( Figure 4C View Figure 4 ) similar to pereopod 2 except in numbers of membrane-like processes spiniform setae, and simple setae. Dactylus with ventrodistal spiniform seta.

Pereopod 4 ( Figure 4D View Figure 4 ) slightly narrower than pereopods 2 and 3. Basis with two dorsal plumose setae, five simple setae, and seta (tip broken). Ischium with two dorsal and four ventral long simple

10 short simple setae. Merus with three dorsal and six ventral long, and one dorsal and nine ventral simple setae. Carpus trapezoidal, with ventrodistal spiniform seta, dorsal plumose sensory seta, dorsal and 11 ventral simple setae. Propodus with ventrodistal spiniform seta, dorsodistal plumose seta, and eight dorsal and 17 ventral simple setae. Dactylus with ventrodistal spiniform seta and one two ventrodistal, three outer, and six outer distal simple setae. Unguis about one-third dactylus naked.

Pereopods 5–7 ( Figure 4E–G View Figure 4 ) similar to pereopod 4 except in number of spiniform setae, plumose setae, and simple setae. Pereopod 6 ( Figure 4F View Figure 4 ) with two ventral membrane-like processes on Pereopod 7 ( Figure 4G View Figure 4 ) with 15 ventral and 22 membrane-like processes on propodus and respectively, and two ventrodistal spiniform setae additional to ventrodistal spiniform seta with bristle on propodus.

Pleopod 1 ( Figure 5A View Figure 5 ) with protopod bearing outer plumose seta and inner hook. Exopod with 37 distal plumose setae (possibly 38; one pore observed) and 31 short simple setae on surface. with seven plumose setae.

Pleopods 2–5 ( Figure 5B–E View Figure 5 ) similar. Protopods with two inner hooks, zero or one outer plumose zero or one outer simple seta. Exopod 2 with slit in middle. Exopods 2 and 4 with 15 distal plumose two and one outer simple setae, respectively. Exopods 3 and 5 lost during dissection. Endopods 2 eight, nine, seven, and seven distal plumose setae, respectively.

Uropod ( Figure 5F, G View Figure 5 ) protopod triangular-prism-shaped, with 11 outer and six inner plumose six simple setae. Exopod ( Figure 5F View Figure 5 ) sinuate, dorsodistally deeply concave (angle 90°), 1.89 times longer wide, with 63 plumose setae and 78 simple setae. Endopod ( Figure 5G View Figure 5 ) oval, with distal plumose sensory and 67 simple setae.

Variation

All specimens possess the dorsally brown-dotted pigmentation pattern but there is a variation in the of spots, especially on the head ( Figure 6 View Figure 6 ); there were no brown spots in pereonites 3 and 4 for NMCR ( Figure 6G, H View Figure 6 ). The numbers of long simple setae on the surface of the telson ranged from four (two

11 ( Figures 5H View Figure 5 , 7F, G View Figure 7 ), and the number of pairs of long simple setae on the apical tip varied from two With respect to the mandibular palp, the numbers of simple setae on article 1, those on article 2, numbers of spiniform setae on article 3 were one, one to three, and two to three, respectively (Figures

E). The number of simple setae on article 3 of the maxillipedal palp was stable (five) in four specimens. The maxillipedal endites were slightly or moderately exceeding the distal margin of article the maxillipedal palp. The angles of the step on the pereopod-1 palmar margin were obtuse but varied were nearly 90° in some pereopods 1 ( Figure 7A–C View Figure 7 ). The angle of dorsodistal concave portion on exopod was stable (90°) in four dissected specimens.

HISTORY

HISTORY in ethanol. (A–C) female lacking oostegites ( holotype); (D–F) female lacking oostegites ( paratype ICHUM9013 View Materials ); (G, H lacking oostegites ( paratype NMCR 99221 ); (I, J) manca ( paratype NMCR 99222 ). Abbreviations: H, head; P1–7,

1–7. Scale bars: 1 mm.

GenBank accession numbers

LC864040 View Materials for 18S (2501 bp) and LC864041 View Materials for 28S (2475 bp), both from the holotype specimen .

Remarks

Amakusanthura camiguinensis resembles Amakusanthura dubia ( Barnard, 1914) and Amakusanthura formis Müller, 1992 in having the brown-dotted pigmentation pattern on the body ( Figures 2 View Figure 2 , 3 View Figure 3 Barnard 1914; Müller 1992), but differs from them in terms of the pereopod-1 palmar shape: weakly in A. camiguinensis ; strongly projected in A. dubia ; straight, not stepped in A. vermiformis .

Among the 45 congeners not sharing the body pigmentation-pattern with it, A. camiguinensis phologically similar to Amakusanthura geminsula ( Kensley, 1982) , Amakusanthura hibbertia Poore Ton, 1988 , Amakusanthura libyana ( Negoescu, 1980) , and Amakusanthura magnifica (Menzies Frankenberg, 1966) in sharing the maxillipedal endite reaching the distal margin of the palp article the uropodal exopod dorsodistally deeply concave (the angle 90°). However, our species differs from species in having one to three simple setae on article 2 of the mandibular palp (zero in A. magnifica seven in A. hibbertia ; Menzies and Frankenberg 1966; Poore and Lew Ton 1988), several (4–11) long setae on the surface of the telson (absent in A. libyana ; Negoescu 1980), and a straight ventral margin carpus of pereopod 1 (sinuate in A. geminsula ; Kensley 1982), in addition to the dorsal pigmentation

(from the carpus to the unguis) from holotype female lacking oostegites, paratype female lacking oostegites (ICHUM and manca ( paratype NMCR 99222), respectively (simple setae on dactylus and carpus omitted); (D) left mandibular from paratype female lacking oostegites (ICHUM9014); (E) right mandibular palp from manca ( paratype NMCR 99222 telsons from paratype female lacking oostegites (ICHUM9014) and manca ( paratype NMCR 99222), respectively,

simple setae on the surface are shown. Scale bars: 100 µm.

Island near Mindanao; and Stygocyathura filipinica ( Botosaneanu and Sket, 1999) , known a freshwater cave in Bohol Island in Visayas. Additionally, one Sauranthura (Poore & Kensley species was collected from Lianga, Surigao del Sur, Mindanao, which will be named in Shiraki (in press). This study represents the first report of Amakusanthura isopods from the Philippines