Holotype: (MABIK CR00240685) female dissected and mounted on five slides. Allotype: (MABIK CR00240686) male dissected and mounted on five slides; from the same locality as the holotype. Paratypes: Four females partly dissected on one slide (MABIK CR00240687) and in 3 vials (MABIKCR00235359–MABIKCR00235361); from the same locality as the holotype. Four males partly dissected on one slide (MABIK CR00240688) and in 2 vials (MABIKCR00235362, MABIKCR00235363); from the same locality as for holotype.

Wando, South Korea (North West Pacific), 34°31.02'N, 128°33.11'E, mud-sandy bottom at a depth of 41 m.

The specific name is derived from Latin canalicula, meaning a groove and refers to the conspicuous groove formed on the distal margin of the male antennule.

Female (with oostegites). Body (Fig. 1A), dorsoventrally flattened, holotype 2.4 mm long, 4.3 times as long as wide. Cephalothorax 20.6 % of body length, slightly wider than long, gradually widening posteriorly, proximal margin with conspicuous extended rostrum with or without small protrusions. Eyes well developed, without pigmentation. Pereonites each with different shape. Pleonites each with pointed epimera. Pleotelson gradually tapered.

Pereon (Fig. 1A): 53 % of body length. Pereonite 1 not fused to cephalothorax, 0.6 times as long as cephalothorax, half as long as wide, posterolateral margins rounded and distally extended. Pereonite 2 medially swollen, slightly shorter than pereonite 1, 0.4 times as long as wide. Pereonite 3 subequal length of pereonite 2, half as long as wide, anterolateral margin with apophysis (arrowed), mid-lateral margin swollen. Pereonite 4 subtrapezoidal, as long as pereonite 2, 0.6 times as long as wide, mid to posterolateral margin gradually widening. Pereonite 5 as long as pereonite 4, half as long as wide, posterolateral margin rounded and slightly extended. Pereonite 6 shortest, 0.4 times as long as wide, posterolateral margin rounded and extended.

Pleon (Fig. 1A, B): 20.2 % of body length, 1.1 times as long as wide, pleonites each with pointed epimera, of which pleonite 5 is largest (arrowed) and rounded ventral hyposphenium (arrowed in Fig. 1B). Pleotelson (Fig. 1A–C): distally tapered, 6.6 % of total length, distally with two broom setae and two simple setae of almost equal length (Fig. 1C).

Antennule (Fig. 1D): Peduncle article 1 robust, 57 % of total length, 2.9 times as long as wide, with three simple setae on inner margin and five simple setae and five broom setae on outer margin. Article 2 0.3 times as long as article1, 1.5 times as long as wide, with two simple setae and one broom seta each on outer and inner distal margin. Article 3 0.3 times as long as article 2, with one simple inner distal seta. Article 4 slightly shorter than article 3, with one simple inner distal seta. Inner flagellum biarticulate: article 1 with one distal simple seta and article 2 with four distal simple setae. Outer flagellum 3-articulate, each article gradually shortened: article 1 with one aesthetasc; article 2 with one aesthetasc and; article 3 shortest, with six distal simple setae.

Antenna (Fig. 1E): 8-articulate, slender and shorter than antennule. Article 1 distally wider and covered with scale-like ornamentations. Articles 2, 3 and 5 naked. Article 4 longest, outer margin each with one broom seta medially and distally, inner margin with one medial and two distal broom setae and one distal simple seta. Article 6 with two distal simple setae. Article 7 with one distal simple seta. Article 8 as long as article 3, with three distal simple setae. Proportional lengths of articles 16.8: 18.0: 5.1: 27.9: 8.4: 11.3: 7.6: 4.9.

Labrum (Fig. 2A): Sub-rectangular, distal margin covered with numerous setules.

Left mandible (Fig. 2B): Incisor with six prominent denticles distally; lacinia mobilis with four distal denticles; setal row with six setulose spiniform setae; molar distally tapered, with sharp, spinose distal edge and eight long setulose setae (arrowed). Right mandible (Fig. 2C) incisor with three irregular distal denticles; setal row with one tripartite seta, which is substantially larger than others and three setulose spiniform setae; lacinia mobilis absent; molar similar to that of left mandible. Palp absent.

Labium (Fig. 2D): Lobe with setulate spines and microtrichia along outer margin and ornamented with setules along inner margin. Palp covered with setules and one distal spine (arrowed).

Maxillule (Fig. 2E): Inner endite with four setulose setae on distal margin; outer margin ornamented with somewhat long setules. Outer endite with nine distal spiniform setae, two subdistal setulose spiniform setae and setules. Palp uniarticulate (arrowed), with one subterminal and one terminal simple setae.

Maxilla (Fig. 3A): Outer lobe of movable endite with four setulose setae. Inner lobe of movable endite with six setulose setae. Outer lobe of fixed endite with six setulose spiniform setae and four setulose tripartite spiniform setae. Inner lobe of fixed endite with four setulose spiniform setae on distal margin and 20 simple bifid tipped setae.

Maxilliped (Fig. 3B, C): Coxa naked. Basis with three curved robust spines on outer proximal margin (arrowed). Palp article 1 with one short seta on outer distal margin and one subdistal setulose seta on medial margin. Article 2 longer than wide, with one distal setulose seta on outer margin and five subdistal setae on inner margin. Article 3 with seven setulose setae along inner margin. Article 4 with seven distal setulose setae. Endite (Fig. 3C) with four stout setulose spiniform setae on inner margin, two coupling hooks on outer margin, six setulose spiniform setae on distal margin, two setulose spiniform setae on subdistal margin and several microtrichia. Epignath (Fig. 3D) rounded, with long distally setulose and wrinkled seta on distal margin (arrowed).

Cheliped (Fig. 3E–G): Basis rounded and with dorsomedial protrusion (arrowed), 1.9 times as long as wide, with one ventrodistal simple seta; exopod 3-articulate, with four plumose setae on distal margin (Fig. 3F). Merus ventrally rounded, shorter than basis, with ventromedial simple seta. Carpus sub-rectangular, with three simple setae on ventral margin and one subdistal simple seta on dorsal margin. Propodus longer than basis, merus and carpus, with two simple setae and two setulose spiniform setae near insertion of dactylus. Fixed finger with ten blunt denticles along cutting edge, one setulose seta (arrowed in Fig. 3G) and two simple setae on inner margin and two simple setae on ventral margin. Dactylus with three simple setae on inner medial margin, cutting edge smooth.

Pereopod 1 (Fig. 4A): Larger than pereopods 2–6, spiniform setae ornamented with small setules bilaterally. Coxa with two dorsodistal simple setae. Basis robust, three times as long as wide, with two short simple setae on ventrodistally. Exopod 3-articulate, distal article with four distal plumose setae. Ischium compact, with one simple ventrodistal seta. Merus 0.6 times as long as basis, 3.3 times as long as wide, with five ventral simple setae and one ventrodistal spiniform seta and two dorsodistal simple setae. Carpus 0.8 times as long as merus, 2.3 times as long as wide, ventral margin with four slender simple setae and two setulose spiniform setae and dorsally with seven simple slender setae and one setulose spiniform seta. Propodus with four strong spiniform setae on ventral margin, one short subdistal simple seta and two distal spiniform setae and three simple setae along dorsal margin. Dactylus and unguis combined subequal to propodus. Dactylus stout, with four pointed denticles along ventral margin and one simple slender seta on subproximal margin; unguis 0.3 times as long as dactylus.

Pereopod 2 (Fig. 4B): Basis 4.8 times as long as wide, with two ventral short simple setae and one dorsal broom seta. Ischium with one ventrodistal simple seta. Merus with three simple ventral setae and one subdistal simple seta. Carpus slightly shorter than merus, with six simple setae and one spiniform seta on ventral margin and six simple setae along dorsal margin. Propodus slightly shorter than merus, with four spiniform setae and one distal simple seta along ventral margin and four simple setae along dorsal margin. Dactylus and unguis combined 0.8 times as long as propodus, with one dorsoproximal simple seta and one ventrodistal simple seta. Unguis 0.4 times as long as dactylus.

Pereopod 3 (Fig. 4C): Basis shorter than that of pereopod 2, 4.8 times as long as wide, with one ventrodistal simple seta. Ischium with one ventrodistal simple seta. Merus 0.3 times as long as basis, with one ventro-subdistal simple seta. Carpus 1.2 times as long as merus, with three simple setae and two spiniform setae of unequal length on ventral margin and three simple setae along dorsal margin. Propodus as long as merus, with two simple setae on dorsodistal margin and three spiniform setae and one distal simple seta on ventral margin. Dactylus and unguis combined 1.2 times as long as propodus. Unguis 0.4 times as long as dactylus.

Pereopod 4 (Fig. 5A): Basis subequal length of pereopod 2, 5.5 times as long as wide, with one simple ventrodistal seta. Ischium with one simple ventrodistal seta. Merus 0.2 times as long as basis, 1.6 times as long as wide, with one simple seta on ventro-subdistal margin. Carpus 1.6 times as long as merus, 2.7 times as long as wide, with one midventral simple seta and three distal simple setae. Propodus 0.8 times as long as carpus, with one setulose spiniform seta on midventral margin and twelve serrated setae on distal margin. Dactylus and unguis combined 1.3 times as long as propodus. Unguis 0.4 times as long as dactylus.

Pereopod 5 (Fig. 5B): Basis shorter than that of pereopod 2, 5.6 times as long as wide. Ischium similar to that of pereopod 4. Merus as long as pereopod 4, 0.3 times as long as basis, 1.8 times as long as wide, with one distal simple seta each on ventral and dorsal margin. Carpus 1.5 times as long as merus, 3.6 times as long as wide, with three simple setae on distal and subdistal margins. Propodus 0.8 times as long as carpus, 3.6 times as long as wide, with four simple setae on distal margin. Dactylus and unguis subequal length of propodus. Unguis similar to that of pereopod 4.

Pereopod 6 (Fig. 5C): Basis 4.4 times as long as wide. Ischium like that of pereopod 5. Merus 0.3 times as long as basis, 1.8 times as long as wide, with three subdistal setae. Carpus 1.3 times as long as merus, with three simple setae subdistally and one simple seta medially. Propodus 0.9 times as long as carpus, with four simple setae on distal margin. Dactylus and unguis 1.2 times as long as propodus. Unguis 0.3 times as long as dactylus.

Pleopods 1–5 (Fig. 5D): Alike. Biramous. Basal article 1.9 times as long as wide, with one plumose seta on inner distal margin. Endopod shorter than exopod, with one plumose seta on inner medial margin and seven distal and outer plumose setae. Endopod biarticulate, article 1 with one outer distal plumose seta; article 2 with seven distal plumose setae.

Uropod (Fig. 2F): Basal article 1.5 times as long as wide, with simple seta on distal margin. Exopod 3-articulate, article 3 1.7 times as long as articles 1 and 2 combined, with two plumose setae on tip of article 3. Endopod 10-articulate, distal article with four simple setae and two broom setae.

Male. Body (Fig. 6A), dorsoventrally flattened, 2.4 mm long, 4.7 times as long as wide, pereonites each with different shape. Cephalothorax 20.5 % of body length, as long as wide, anterior margin with conspicuous elongate, rounded rostrum. Eyes well developed, without pigmentation.

Pereon (Fig. 6A): Wider than long, 50.3 % of body length. Pereonite 1 0.4 times as long as cephalothorax, 0.4 times as long as wide, lateral margin rounded and posteriorly extended. Pereonite 2 laterally rounded, 1.15 times as long as pereonite 1, half as long as wide. Pereonite 3 slightly longer than pereonite 2, 0.6 times as long as wide, anterolateral margin with pointed apophysis. Pereonite 4 subequal length of pereonite 3, 0.7 times as long as wide. Pereonite 5 0.8 times as long as pereonite 4, half as long as wide, posterolateral margin rounded and posterior margin extended. Pereonite 6 shortest of all pereonites, half as long as wide.

Pleon (Fig. 6A–D): 22 % of body length. Pleonites subequal in length, each with anteriorly pointed and posteriorly rounded ventral hyposphenium (arrowed in Fig. 6B). Epimera pointed and gradually becoming larger posteriorly, with one simple seta (arrowed in Fig. 6C). Pleotelson (Fig. 6A, B, D): 7 % of body length, as long as pereonite 6, with two simple setae on lateral margin, two broom setae and two long simple setae of unequal length on posterior margin.

Antennule (Fig. 6E): Peduncle article 1 longer and more robust than other articles, outer distal margin with projection having row of rough denticles (arrowed) and mid to distal surface with deep groove between projection and smooth margin (marked by inverted triangle), 47 % of total length, 1.7 times as long as wide, with eight broom setae and three simple setae on outer margin and two simple setae on inner margin. Article 2 about 0.4 times as long as article 1, with two simple setae on inner margin. Article 3 about 0.4 times as long as article 2, 0.6 times as long as wide, with one inner distal simple seta. Article 4 shorter than article 3, naked. Inner flagellum biarticulate: article 1 with inner distal simple seta and article 2 with three distal simple setae. Outer flagellum 5-articulate: articles 1 and 2 wider than long, with fringes of aesthetascs distally; article 3 with one aesthetasc; article 4 longest, with one aesthetasc; article 5 shortest, with three simple setae.

Antenna (Fig. 6F): Similar to those of female. Proportional lengths of articles 15.7: 19.3: 4.2: 26.6: 9.1: 14.6: 6.3: 4.2.

Labrum and labium almost equal to those of female.

Left mandible (Fig. 7B): Incisor terminally pointed, with small denticles. Lacinia mobilis distally pointed. Setal row with four small setae (arrowed). Molar subtriangular and reduced compared to female. Right mandible (Fig. 7A): incisor with distal denticles. Setal row with vertical row of denticles and one pointed seta. Molar similar to that of left mandible.

Maxillule (Fig. 7C): Reduced and simplified compared to that of female. Inner endite with four short simple spiniform setae. Outer endite with eight distal simple spiniform setae. Palp with one subdistal and one distal simple setae.

Maxilla (Fig. 7D): Movable endite with microtrichia on surface: outer lobe with four simple setae; inner lobe with six short simple setae. Fixed endite reduced and simplified: outer lobe with seven short simple setae; inner lobe very reduced, with two short simple setae.

Maxilliped (Fig. 8A, B): Palp articles similar to those of female. Endite (Fig. 8B) simplified: distal and subdistal margins with six short simple spiniform setae, inner margin with two coupling hooks and outer margin with several spines. Epignath (Fig. 7E): Smaller than that of female, distal seta longer than lobe.

Cheliped (Fig. 8C, C’, D): Basis rounded, 1.5 times as long as wide, with one ventrodistal seta; exopodite similar to that of female. Merus with one simple seta and three processes on midventral margin (enlarged in Fig. 8C’). Carpus similar to that of female. Propodus 2.5 times as long as carpus, setation equal to that of female. Fixed finger with one ventral and one medial simple setae, cutting edge with three simple setae and several denticles and blunt processes. Dactylus as long as fixed finger, with three simple setae on inner medial margin and several blunt processes and denticles along cutting edge.

Pereopod 1 (Fig. 9A): Basis 2.7 times as long as wide, with one ventrodistal simple seta. Ischium with one ventrodistal simple seta. Merus 0.7 times as long as basis, 2.3 times as long as wide, with two dorsodistal simple setae, one ventrodistal spiniform seta and four ventral simple setae. Carpus 0.7 times as long as merus, 2.3 times as long as wide, with two ventrodistal spiniform setae, three ventral simple setae, one dorsodistal spiniform seta and seven dorsal simple setae. Propodus 0.7 times as long as carpus, 1.8 times as long as wide, with four ventral spiniform setae, two ventral simple setae near insertion of dactylus, two dorsodistal spiniform setae and four dorsal simple setae. Dactylus and unguis combined 1.3 times as long as propodus. Dactylus with three short setae along ventral margin and one sub-proximal seta on dorsal margin. Unguis third length of dactylus.

Pereopod 2 (Fig. 9B): Basis 5.2 times as long as wide, with one ventrodistal simple seta on ventral margin and one dorsomedial broom seta. Ischium compact, with one ventrodistal simple seta. Merus half as long as basis, 3.2 times as long as wide, with two ventral simple setae. Carpus slightly shorter than merus, with five ventral simple setae and four dorsal simple setae. Propodus as long as carpus, with three spiniform setae and one distal simple seta on ventral margin and three simple setae and one broom seta on dorsal margin. Dactylus and unguis combined 1.2 times as long as propodus. Dactylus similar to that of female. Unguis half as long as dactylus.

Pereopod 3 (Fig. 9C): Basis shorter than that of pereopod 2, with two broom setae each on dorsal and ventral margin and one ventrodistal simple seta. Ischium similar to that of pereopod 2. Merus 0.4 times as long as basis, with three ventral simple setae. Carpus as long as merus, with four ventral simple setae and three dorsal simple setae. Propodus slightly shorter than carpus, with two ventral spiniform setae, one ventrodistal simple seta and two dorsodistal simple setae and one dorsal broom seta. Dactylus and unguis combined 1.3 times as long as propodus. Unguis 0.3 times as long as dactylus.

Pereopod 4 (Fig. 9D, E): Basis almost as long as that of pereopod 2, 5.9 times as long as wide, with one ventrodistal simple seta and one ventromedial broom seta. Ischium similar to that of pereopod 3. Merus 0.2 times as long as basis, with two ventrodistal simple setae. Carpus 1.7 times as long as merus, three times as long as wide, with two ventromedial simple setae and three distal simple setae. Propodus 0.8 times as long as carpus, 2.8 times as long as wide, with one ventromedial spiniform seta and eleven distal serrated spiniform setae. Dactylus and unguis combined 1.3 times as long as propodus. Unguis half as long as dactylus.

Pereopod 5 (Fig. 9F, G): Basis longer than that of pereopod 4, 5.8 times as long as wide, with one ventrodistal simple seta and one dorsomedial broom seta. Ischium similar to that of pereopod 4. Merus 0.2 times as long as basis, twice as long as wide, with two distal simple setae. Carpus 1.4 times as long as merus, 3.6 times as long as wide, with two distal simple setae. Propodus slightly shorter than carpus, 3.6 times as long as wide, with four distal simple setae. Dactylus and unguis combined 1.1 times as long as propodus. Unguis half as long as dactylus.

Pereopod 6 (Fig. 9H): Basis shorter than that of pereopod 5, 6.4 times as long as wide, with five broom setae and one ventrodistal simple seta. Merus 0.3 times as long as basis, with two ventral and two dorsal setae distally. Carpus 1.3 times as long as merus, 3.1 times as long as wide, with one ventral and one dorsal seta distally. Propodus subequal length of carpus, 4.3 times as long as wide, with three distal simple setae. Dactylus and unguis combined as long as propodus. Unguis half as long as dactylus.

Pleopod (Fig. 5E): Similar to that of female.

Uropod (Fig. 6G): Basal article 1.7 times as long as wide, with simple seta on distal margin. Exopod 3-articulate, article 3 twice as long as articles 1 and 2 combined, with two plumose setae on tip of article 3. Endopod 10-articulate, distal article with nine simple setae.

To check the morphological variation with size, ten specimens (1.64–2.73 mm) were partly dissected and the cheliped, the pereopod 1 and a ventral hyposphenium of pleonite were examined for different sizes and some variations were found: 1) in the cheliped, the dactylus and fixed finger of the males were modified in size: in the cheliped of the large sized males (over 2 mm), the cutting edge of the dactylus is extended and strongly curved and the processes on the proximal margin are prominently developed; 2) the number and size of setae on the pereopod 1 propodus increased with size; 3) a ventral hyposphenium of the male pleonite is modified from a rounded shape to a subrectangular shape, with body length reaching over 2 mm.