Two species of mysid,
The genus
Jo and Jeon (2007) firstly reported three species belonging to the genus:
All specimens were collected with a light and bait trap equipment. The specimens were preserved in 70% ethyl alcohol and illustrations prepared using a drawing tube on a compound microscope equipped with differential interference contrast (Model BX-60; Olympus, Tokyo, Japan). Body length was measured from the tip of the rostrum to the distal apex of the telson excluding the spine. The simple setae and plumage of the plumose setae on the margin of antennules, antennae, mouthparts, and uropods are omitted from the figures. Terminology for the dissection and measurement is adopted from Tattersall and Tattersall (1951). All specimens have been deposited in the Marine Arthropod Depository Bank of Korea (MADBK), Seoul National University.
Order Mysida Haworth, 1825
Family Mysidae Haworth, 1825
Subfamily Mysinae Haworth, 1825
Genus Nipponomysis Takahashi & Murano, 1986
Antennal scale (Fig. 2B) lanceolate with round apex, about 4 times as long as broad; distal suture occupying about 1/18 of whole length of antennal scale; outer margin straight, inner margin concave, entire margin with setose. Antennal peduncle 3-segmented; second segment longest, 2.5 times as long as first; third segment 1.5 times as long as first one.
Antennular peduncle (Fig. 2C) 3-segmented; first segment longest, 2 times as long as second one and bearing three plumose setae; second segment shortest, about 1/2 of third one.
Mandibular palp (Fig. 2D) 3-segmented; second segment 2.5 times as long as third
Maxilla (Fig. 2E) armed with plumose setae along margin; endopod 2-segmented, second segment 1.5 times as long as broad.
Maxillule (Fig. 2F) with outer lobe bearing 8 robust setae on distal margin.
Endopod of first and second thoracopods (Fig. 2G, I) shown no marked difference from those in other species of genus.
Endopod of third to eighth thoracopods (Figs. 2H, 3A) with 3-subsegmented carpopropodus; proximal segment longest, remaining two segments equal in length; dactylus short and robust.
Inner uropod (Fig. 3B) with 9-11 spines in ventral statocyst region; outer uropod 1.1 times longer than inner uropod.
Telson (Fig. 3C) linguiform, about 1.5 times as long as broad; proximal half of lateral margin bearing 3-5 spines and remaining margin armed with series of spines which smaller 1-4 spines grouped between larger spines, larger spines increasing in length); apex truncated, armed with 2 pairs of spines, outer spines robust, 3 times as long as inner ones.
To date, this species has been reported only from Japan, so this second description extends the geographical distribution westward. Additionally, this species is coastal form and inhabits littoral, as well as common among seaweeds (
Antennal scale (Fig. 4C) lanceolate with round apex, about 5 times as long as broad; distal suture occupying about 1/20 of whole length of antennal scale; outer margin straight, inner margin concave. Antennal peduncle 3-segmented; second segment longest, 1.5 times as long as first; third segment slightly shorter than second one.
Antennular peduncle (Fig. 4D) 3-segmented; first segment longest, 1.7 times as long as second and bearing three setae; second segment shortest, about 2/3 length of third one.
Maxilla (Fig. 4E) armed with plumose setae along margin; endopod 2-segmented, distal segment about 2 times as long as broad.
Maxillule (Fig. 4F) with outer lobe along with 11 robust setae on distal margin.
Mandibular palp (Fig. 4G) 3-segmented; second segment 1.8 times as long as third.
Endopod of first, second thoracopods (Fig. 4B, J), and exopod of third to eighth thoracopods (Fig. 4I) shown no marked difference from those in other species.
Fourth pleopod (Fig. 4H) biramous; exopod 3-segmented, first segment elongate, 4.4 times as long as second one; third segment subequal in length to second one, with 2 strong spinose setae terminally; endopod unsegmented and rudimentary
Inner uropod (Fig. 4K) with 14 spines in ventral statocyst region.
Telson (Fig. 4L) narrowly long triangular, about 2 times as long as broad; proximal 1/3 of lateral margin bearing 8-9 spines and remaining margin armed with numerous series of spines which smaller 1-7 spines grouped between larger spines, increasing in length toward apex; apex truncated and armed with 2 pairs of spines, outer spines about 2 times as long as inner ones.
Key to the species of
1. Lateral larger spines on telson subequal in size ∙∙∙∙∙∙∙∙∙∙∙∙2
- Lateral larger spines on telson gradually increasing in size toward distal end or distalmost larger spine markedly longer than the others ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙4
2. Telson linguiform, lateral margin with spineless part occupying 1/6 of its own length ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙ ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙
- Telson narrowly long triangular, lateral margin armed with spines throughout its entire length ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙3
3. In male, exopod of fourth pleopod with first and second segments armed with a pair of plumose setae, and second and third one subequal in length ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙ ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙
- In male, exopod of fourth pleopod with first segment about as long as the sum of second and third ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙ ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙
4. Telson elongate linguiform, about twice as long as broad, armed with 6-9 sets of grouped spines on lateral margin, lateral larger spines of telson subequal in size except that the distal most spine markedly longer than the other ∙∙∙∙∙∙∙ ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙
- Telson linguiform, 1.5-2 times as long as broad, armed with 4-6 sets of grouped spines on lateral margin, lateral larger spines of telson gradually increasing in size toward distal end ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙5
5. Rostral plate extending to distal end of first segment of antennular peduncle; proximal subsegment of carpopropodus of third to eighth thoracic endopods armed with setae ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙
- Rostral plate not extending beyond base of antennular peduncle; proximal subsegment of carpopropodus of third to eighth thoracic endopods armed with 4-5 spines ∙∙∙∙∙∙∙∙ ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙