Journal of the Oceanographical Society Vol.24, No.4, pp.173 to 177, August

On the Nauplius of Undinula vulgaris(DANA), (Copepoda, )*

Fumihiro KOGA**

Abstract: Three nauplius stages of Undinula vulgaris, the first, the third and the fifth stages, were studied. The nauplius is oval in out-line in early stages, becoming more elongate with each successive stage. The dorso-ventral flexure in the posterior portion of body curves vent- rally. The nauplius of U. vulgaris can be distinguished from those of other species of the family by the structure of appendages in the respective stages.

from the carapace produces posteriorly. On the 1. Introduction posterior portion of the body, there is a dorso- Undinula vulgaris is one of the common ventral flexure which is provided with the caudal surface-living in Japanese waters, and armature of type, and it curves ventrally. appears abundantly during summer and early There is a small dark-red eyespot near the frontal autumn in the warm sea area, especially in the margin of the head. The thick oval labrum is Tsushima region, off the coast of northwestern beset with small poor spines. The antennule is Kyushu, where the warm Tsushima Current 3-jointed and oar-like. In nauplius stage the cutt- prevails. At this season the species is the most ing edge of the gnathobase does not appear on the important planktonic in this region. The coxa of antenna. The gnathobase of mandible nauplii of the following species belonging to the which begins as a prominent bulge in early family Calanidae have been described by several nauplius stages becomes a long curving process authors: , C. helgolandicus furnished with 3 teeth. and C. hyperboreus by LEBOUR (1916), MAR- Nauplius stage I SHALL and ORR (1955), and SƒÓMME (1934) ; Fig. 1-1. C. plumchrus by CAMPBELL (1934). The body Length, about 0.15 mm. Body broadly oval, of these nauplii is ovoid or pyriform in shape, rounded at anterior end, and tapers slightly and has no strong median spine on the posterior towards posterior portion which is furnished with end of body. The antennule is 3-jointed. The a pair of slender end feelers as caudal armature. most of the nauplii of this family are characterized A conspicuous labrum produces ventrally and is by the dorsoventral flexure which is divided from surrounded by 3 pair of appendages, antennules, the carapace and flexed ventrally. antennae and mandibles. A slight indication of The egg of U. vulgaris measured 0.16mm in the rostrum is seen in the anterior region of the diameter. The egg laid in the night of September body. 9th, hatched out in the next night and changed Antennule (Fig. 2-1) is 3-segmented, uniramous, into nauplius stage I, and on September 11th it elongated and apically rounded. There are 3 developed to stage III. The temperature ranged terminal setae in the distal segment. from 20.0 to 24.0•Ž. Antenna (Fig. 2-4) consists of coxa, basipodite, unsegmented endopodite and segmented exopodite; 2. Description of the nauplius characters coxa and basipodite lack the armature; coxa The nauplius is oval in outline in early stages, convexly rounded on inner margin; endopodite but in later stages the abdomen which is divided bears 2 long terminal setae; exopodite consists of * Received May 24, 1968 5 visible segments; the 1st segment has no seta, ** Fukuoka Prefectural Fisheries Experimental Station, the 2nd to the 4th segment are furnished with a Fukuoka, Japan long seta respectively, and the 5th with 3 setae .

(27) 174 Jour. Oceanogr. Soc. Japan, Vol.24, No.4 (1968)

Fig. 1.Three nauplii of Undinula vulgaris.

1, Stage-I (•~130); 2, Stage-III (•~100); 3. Stage-V (•~65); 4, Caudal armature of Stage-V (•~130).

Fig. 2. The appendages of three nauplii of U. vulgarise

1, 2, 3, Antennules of Stage-I, III, V ; 4, 5, 6, Antennae of Stage-I, III, V ;

7, 8, 9, Mandibles of Stage-I, III, V; 10, Maxillule of Stage-V.

(1, 4, 7-•~260; 2, 5, 8- •~200; 3, 6, 9, 10-•~130).

Mandible (Fig. 2-7) consists of coxa, basi- smaller ventral hooks and curved rows of very podite, endopodite and broad exopodite; exopodite small spines which occur at the base of smooth consists of 4 segments; the 1st to the 3rd segment end hooks. There are rows of small spines on each with a seta and the 4th with 2 setae. both sides of the abdomen. Nauplius stage III Antennule (Fig. 2-2): The 1st segment Fig. 1-2. unarmed. The 2nd segment divided into 3 parts, Length, about 0.27mm. Posterior portion of each lobe with a seta, the most distal seta is dorsoventral flexure is armed with 2 terminal coarer than the others and extends to the end of feelers, a pair of smooth end hooks, a pair of terminal segment. In the terminal segment

(28) On the Nauplius of Undinula vulgaris (DANA), (Copepoda, Calanoida) 175 ventral margin is armed with a short fine seta exopodite of 8 segments, the 1st segment with no on distal border, and there are 2,lightly longer seta, the 2nd segmen with 2 small and a long fine setae on convexed dorsal margin in addition setae, the 3rd to the 7th each with a long seta to 4 terminal setae. on inner margin, terminal segment which is Antenna (Fig. 2-5): Coxa with 2 smooth smaller than the other segments is furnished with blade-like masticatory processes and a slender seta 3 setae. on inner margin ; proximal portion of basipodite Mandible (Fig. 2-9): Coxa broader including with a long and 2 shorter setae, the distal the gnathobase which becomes a long curving portion of basipodite with a seta; endopodite with masticatory process bearing a seta and ending 3 2 fine setae on inner margin and 4 terminal teeth; basipodite with 4 setae on inner margin; setae; exopodite definitely 7-segmented, the 1st endopodite as in stage III; exopodite as in stage segment with no seta, the 2nd segment which is III. imperfectly divided from the 1st and is a large Maxillule (Fig. 2-10) : A 2-lobed flap with quadrate in shape with 2 setae on inner margin, setae; coxa with 2 slender setae on inner margin, the 3rd to the 6th segment with a coarse seta imperfectly divided from basipodite which is each, terminal segment with 2 apical long plumose furnished with 2 setae as in coxa; endopodite setae and an additional fine seta. with 2 setae on inner margin and 4 setae on Mandible (Fig. 2-8) : Coxa with a fine seta, terminal margin; exopodite with 6 setae im- and basipodite with 3 equal small setae on convex perfectly separated from endopodite. inner margin of segment; endopodite shows slight, indication of division into two parts and 3. Key to the nauplius of the family Calanidae the rounded elevation inner margin of proximal (1) Key to stage portion, this portion with 4 slender setae, the I . The antennule with 3 terminal setae distal portion with 2 slender equal setae on inner Stage-I . border and 4 terminal setae; exopodite consists II. The antennule with 4 terminal setae. of 4 segments as in stage I, the 2nd and the 3rd 1. The terminal segment of antennule with no segment with a seta each, and the 1st and seta on the ventral and dorsal border terminal segment with 2 setae respectively. Stage-II . Nauplius stage V 2. The terminal segment of antennule with a Fig. 1-3. ventral and 2 dorsal setae•c•cStage-III. The larva was described with a natural specimen 3. The terminal segment of antennule with 3 obtained by net haul. Length about 0.44mm. ventral and 4 dorsal setae•c•cStage-IV. Dorsoventral flexure pronounced; armature of 4. The terminal segment of antennule with 4 posterior end consists of 2 pair of ventral hooks, ventral and 6 dorsal setae•c•cStage-V. 2 pair of denticulated end hooks, 3 pair of lateral 5. The terminal segment of antennule with 5 hooks which are smaller than end or ventral ventral and 8 dorsal setae•c•cStage-VI. hooks, and curved rows of fine spines at bases of lateral hooks (Fig. 1-4). Maxillule evidents as (2) Key to species small bilobed structures. Stage-I

Antennule (Fig. 2-3) : The 1st and the 2nd I. The endopodite of antenna and mandible with segment as in stage III, ventral border of terminal 2 terminal setae. segment with 4 setae, dorsal border with 6 setae, 1a. The coxa and the basipodite of antenna is and terminal border with 4 setae. devoid of the seta Calanus plumchrus. Antenna (Fig. 2-6) : Coxa with 2 blade-like 2a. The coxa or basipodite of antenna with a few spines and a slender seta on inner margin; setae. proximal portion of basipodite as in stage III, 1. The body is 0.18-0.24mm in length distal portion of basipodite with 2 setae; endo- Calanus finmarchicus, podite with 2 setae and a shorter seta on inner C. helgolandicus. margin, and with 5 setae on terminal margin; 2. The body is 0.25-0.29mm in length

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Calanus hyperboreus. setae, the carapace is 0.34-0.45mm in length II. The endopodite of antenna with 2 terminal Calanus hyperboreus. setae, the endopodite of mandible is devoid 2. The endopodite of antenna with 5 terminal of seta•c•cUndinula vulgaris. setae, the carapace is 0.38-0.44mm in length Stage-II Calanus finmarchicus, I. The 1st segment of endopodite of mandible C. helgolandicus. with 2 setae and the segment of endopodite 2a. The basipodite of antenna with 3 setae on of mandible with a lateral and 2 terminal the distal part•c•cCalanus plumchrus. setae•c•cCalanus plumchrus.

II. The 1st segment of endopodite of mandible Stage-VI with 3 setae. I. The endopodite of antenna with 3 lateral 1a.The body is 0.18-0.24mm in length setae•c•cCalanus plumchrus. Calanus finmarchicus, II. The endopodite of antenna with 4 lateral C. helgolandicus. setae. 2a. The body is 0.25-0.29mm in length 1a. The basipodite of antenna devoid of seta on Calanus hyperboreus. the dorsal margin,thecarapace is 0.37-0.45 mm in length•c•cCalanus finmarchicus, Stage-III C. helgolandicus. I. The basipodite of antenna with a seta on the 2a. The basipodite of antenna with a seta on the distal part. dorsal margin, the carapace is 0.46-0.54mm 1a. The endopodite of antenna with 2 lateral setae in lengthCalanus hyperboreus. Undinula vulgaris. 2a. The endopodite of antenna with 3 lateral setae. 4. Conclusions 1. The carapace is 0.21-0.27mm in length There is no an evident specific character in Calanus finmarchicus, the nauplii of Calanidae. The character does C. helgolandicus. not appear in the segmentation and setation 2. The carapace is 0.28-0.34mm in length of appendages, caudal armatures etc, but Calanus hyperboreus. appears only in the body length. For II. The basipodite of antenna with 2 setae on example, there is sharp distinction between the distal part•c•cCalanus plumchrus. Calanus finmarchicus and C. helgolandicus in the eggs and in the adult stages, but the

Stage-IV nauplius of C. finmarchicus is not distin- I. The basipodite of antenna with 2 setae on guishable from that of C. helgolandicus. the distal part. It may be attributed to the fact that the 1a.The carapace is 0.27-0.34mm in length specific character of the nauplii is simple and Calanus finmarehicus, is less distinguishable than those in the adult. C. helgolandicus. Acknowledgment 2a. The carapace is 0.34-0.39mm in length Calanus hyperboreus. It is a pleasure to record here a debt of II. The basipodite of antenna with 3 setae on gratitude to Dr. O. TANAKA for his kindness in the distal part•cCalanus plumehrus. reading the original manuscript.

References Stage-V CAMPBELL, M. H. (1934): The life history and post I. The 1st segment of endopodite of mandible embryonic development of the copepods, Calanus with 4 setae•c•cUndinula vulgaris. tonsus BRADY and Euchaeta japonica MARUICAWA. II. The 1st segment of mandible with 5 setae. J. Biol. Bd. Can.. 1 (1). 1-65. 1a. The basipodite of antenna with 2 setae on LEBOUR, M. V. (1916): Stages in the life history of the distal part. Calanus finmarchicus (GUNNERUS), experiment- 1. The endopodite of antenna with 4 terminal ally reared by Mr. L. R. CRAWSHAY in the

(30) On the Nauplius of Undinula vulgaris (DANA), (Copepoda, Calanoida) 177

Plymouth laboratory. J. Mar. Biol. Ass. U. K., London. 188pp.

11 (1), 1-17. SOMME, J. (1934): Animal plankton of the Norwegian MARSHALL, S. M. and A. P. ORR (1955): The coast waters and the open sea. 1. Fiskeridir.

biology of a marine . OLIVER & BOYD. Skr. HavundersƒÓk, 4 (9), 1-163.

Undinula vulgaris (DANA), (Copepoda, Calanoida) の nauplius

に つ い て

古 賀 文 洋

要 旨 九 州 北 西 海 域 に お い て 夏 か ら秋 に 多 数 出 現 す る 暖 期 で は こ のfeelersの 外,end, lateralとventral hooks,

水 系 種 のU,vulgarisの3期 のnaupliusを え た.こ れ や 又 多 く の 微 細 な と げ を 持 つdorsoventral flexureを 持 ら のnaupliusがLEBOUR(1916), MARSHALL & ORR つCalanus typeを 示 し た.U. vulgarisのnauplius

(1955),とSφMME(1934)等 が 記 載 し たC. finmar- 期 の 特 徴 は 他 のCalanus typeのnauplius同 様,第1 chicus, C. helgolandicusとC.hyperboreus,そ し て 触 角 の 末 節 の 刺 毛 の 数 に よ っ て 決 定 さ れ る.又 各 期 に お

CAMPBELL (1934)が 記 載 し たC. plumchrusと 同 様, け るU. vulgarisの 特 徴 に つ い て は 本 論 の 中 で 述 べ,上

Fig.1に 示 す よ う に 初 期 で は1対 のfeelersを 持 ち,後 記 の 種 と 共 にkeyを 与 え た.

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