194 Palinurid phyllosoma larvae and their distribution in winter off the Pacific coast of Japan TAKU YOSHTIURA1,KENJI MORINAGAI, SHIGERU SHIRAI 2, AND HIROSHIYAMAKAWA3 SeikaiNational Fisheries Research Institute, Kokubu; Nagasaki 850-0951, Japen ([email protected]), 2Japon Sea National FisheriesResernrh Institute,Suido, Niigata 951-8121,Japan, and 3Depamnent of Aquatic Binsciences,Tokyo Universityof Fisheries,Konan Tokyo108-8477, Japan SUMMARY:Widespread ichthyoplanidonsamplings were conducted along the Pacific coast of Japan in winter 1989 to 1992 to monitor abundance of larval Pacific saury. Middle and late stage phyllosoma larvae of the Palinurldae were found among the surface net samples. Allof these larvae were caught at night, and they were distributedwidely south of the Kuroshio. They were identifiedas Form A, and were likelyto be the larvae of the Japanese spiny lobster, Panulinis japonicus, or of the 'P. longpes complex' on the basis of their morphological characteristics and the known adult distributionarea. KEY I4 RDS: phyllosoma, spiny lobster, Panulirus, larval distribution, Kuroshio examinaton of metamorphosed post-larvae. However, The larvallife of the paTmuridspiny lobsteris extremely species identification of late-stage Form A larvae that are long,ranging from a few monthsto almost2 years before not captured in summer and of younger stages is stilll the lastphyllosoma stage metamorphoses to the post-larval difficult. stage." In the Japanesespiny lobster,Panulirus japonicas We examined plankton samples caught by surface (Decapoda, Palinuridae), rearing experiments in the towing of larva nets during 4 winter seasons in a wide area laboratory have shown that metamorphosis to the off the Pacific coast of Japan. We found 11 palinuuid post larval stage occurs between 231 and 417 days after phyllosoma larvae, of which the morphological hatching.2,3,4}However, this longlarval life has not yet been characteristics matched those of Form A) Here we provedin the ocean,because the numberof capturedwild describe the morphology and distribution of middle and phyllosomalarvae around Japan is not large and serial late-stage Form A phyllosoma larvae. As the scientific growthdata on wildlarvae have notyet beenpublished names of P. Iongipes subspecies and types have not been Among 5 forms (A-E) of palinuridlarvae captured standardized,11,12 we use "P. longipes" to represent P. around Japan,) Form A is thought to be P. japonicus.6) longipes complex in this report. Although127 Form A larvae with body lengths exceeding 20 mmhave been captured hitherto,) far fewer young MATEIRIALS stages smallerthan 20 mm long have been caught, with the exception of new hatchlingss) Moreover,late-stage Researchcruise was conductedby the RV. Tenyo-mare phyllosoma of the P. japonicas group may be (1020t) in 1989and RV. Koyo-maru(2342t) from 1990 to morphologicallysimilar 6,9) and Matsuda. and Yamakawar10) 1992 to monitor the abundancesof eggs and larvaeof found no morphologicaldifferences between P. japonicas Pacific saucy. Both research vessels belonged to the and P. longipeslarvae reared in the laboratory. National FisheriesUniversity and were charteredby the In recent years, relativelylarge number of Form A Tohoku National Fisheries Research Institute.Dates of larvaehave been collectedin and aroundthe Kuroshiooff samplingwere 25 Januaryto 10 February 1989, 1 to 28 southernKyusyu, thus proving the usefulnessof oblique February1990,13 Februaryto 7 March 1991,and 13 to 28 andsurface towing atnight with relative large samplers February 1992. Three types of larva net were use&a like the Isaacs-Kickdmidwater trawl!) According to standard net (Maruchi net type A: MNA), a net for Yoshimuuaet al.7, final-stagelarvae concentratedin and high speed towing (HJN), and the new standardnet for around the Krnoshio and younger larvae are probably Pacificsaucy (NJN). The MNA has a 1.3m diametermouth, distributedin the southernarea ofthis current.The wild late 4.5 m length,and anterior2.00 mm and posterior0.33 mm and final-stageForm A larvae were identified as P. mesh Towing speed and durationwere 2.0 knots and 5 japonicas, because those were captured in mid-summer, minutes,respectively. The HJN has a 1.5m diametermouth, whichis just beforeor in the middleof themain post larval 10.0m length,and 5 steps of mesh size, fromanterior 18.0 settlementseason of P. japonicas but should not of P. mm to posterior3.5 mm. The NJN has a 1.3 m diameter longipes, adding the species confirmation.made by mouthand 5.0 m lengthwith a 0.45 mm mesh Thetowing INTRODUCTION 195 Table 2. Morghanetrics of the 1t Form A phyllosoma larvae caught during the s peedfor HJN and NJN were 5.0 and 2.0 knots, 4 reseatch and staged with the key for P.longipes.11) respectively,and the towing duration for both nets were 10 minutes.Every net was towed near the surface,and two-girdsof themouth being kept under the waterduring towing. Allthe samples were preserved in 5 % formalin,and thelobster larvae and post larvae were sorbed and observed in 1998.The type of phyllosomalarvae were identified accordingto Murano andNonaka el a1.6)Form A5) larvae of Pamulirus were staged avvording to Inoue 13) and Matsuda and Yamakawa.10) CL: Cephalie shieldlength CW: Cephalic shield width TW: Thorax width **:The size of l specimen whose body shrank and warped severely as a result of RESULTS preservation is not included. shown in Table 2. Body lengths ranged from 13.7 to 34.2 Therewere a totalof 183hauls over the 4 winters,of which mm. The cephalic shield was spindle shaped, and the ratio 144hauls were done at nightwhile the other39 at day-time of cephalic width to length ranged from 0.56 to 0.65. The (Table1). A totalof 865 phyllosomalarvae, comprising 11 cephalic width was much narrower than the thorax, and the palinuridand 854 scyllarid,and 2 nistos(post larvae)were ratio of cephalic shield width to thorax width ranged from find (Table1). The palmsid larvae were capturedin 10 0.74 to 0.86 (average = 0.80, SD = 0.05). These night-timehauls; 5 specimenswere collected by HJN and 6 characteristics matched those of Form A by NJN. The 854 scyllaridphyllosoma larvae and the 2 On the basis of the staging key used for P. longnpes,lo> nistoswere found in 78 hauls.Only 9 scyllaridlarvae were the 11 palinurid larvae were classified into 4 stages, ‡Y, ‡Z, c ured in thedaytime, in 2 hauls. ‡[, and X (Table 2, Fig. 1). Table 3 shows the The molphometricsof the 11 palinurid larvae are morphological characteristics of Form A larvae by stage. The damage to the body by net towing was generally sever, Table!. Total nmberofhaulsandlobslarvae collecxed. endopodites on pereiopods 1 to 4 were absent in all larvae, Table 3. Morphological details of each stage of Fcml A phyllosoma larvae found. The numbers of samples are the same as in Table 2. RN: Larvanetfalvghspeadtowing MNA:Maruchi net type A NJ N: Newstandm dlarva net Ad: Azueonule Ago: Antenna ed: endite its: long terminal setae st: strong tanunal spine ups:termini plumose setae fs: hanging setae Table 3. continued Fig.1 Body lengthdowbuic ibystage fortheFamAlarvae. exop: exopod ai: appendix intana 196 F1g,2 Henzantaldistnbution of Form A phyllcsomalarvae caught by surface net-towingat night-time.The shadedlines rgpresent 9c the Kuroshioaxis duringthe periodsshown. Solid cimcles show the numberof Form Alarvae per 10 minutestowing of net. and some of the natatory setae of the exopods on the not enoughto covervariations in the characteristicsof every pereiopods were lost stageof P,japonicas, and he didnot showthe analyticalkey Figure 2 shows the distribution of Form A phyllosoma for definitivestaging, the morphologicalcombinations in larvae in each cruise and the variations in axis of the our larvaewould not matchedcompletely to thoseof staged Kuroshio. The Kuroshio meandered off central Honsyu in P japonicus13).Therefore, any dainty over larval winter 1989,1990, and 1991 and flowed parallel to Honsyu stagingwould not rule out the possibilitythat the larvae in winter 1992. The larvae were widely dispersed in the were P. japonicas. These larvae were prior to stageat research area, covered lot 30•‹-34•‹N and long. 132•‹-142•‹E. metamorphosisto post larvae(with the exceptionof 1 final All of them were caught south of the Kuroshio, and none specimen)and were not capturedin the settlementseason. was caught: north of the current near the shores of Honsyu. An indirectmanner of identificationbased cal stage, capture season,and area7)cannot be appliedto them Inrecent years, DISCUSSION settlementof P, japonicas pueruli(post-larvae) in shallow coastal areas has been observed even in mid-winterat Both the morphometrics and morphology suggested the which the Kuroshiocomes close to the coast.'4Therefore, palinurid larvae examined were those of P. japonicas and P. there is a possibilitythat everypalinurid larva in thepresent longipes, as described by Inoue13) and Matsuda and study-including the final-stagelarva capturedin winter Yamakawa.10) Staging of larvae was attempted according to 1991-is P, japonicas. However,ambiguity of species the table of characteristics for each stage of P. japonicus,13) identificationstill remains between P. japonicas and P. but some larvae did not fit these characteristics completely. longipes,and larvae of some subspeciesor types of P. For example, 2 larvae did not have an exopod on the 2nd longipes have never been studied. Consequently,we maxilliped afature of stages younger than ‡[ but they concludethat the finaljudgment on whetherthe present did have bifrd pleopods-a feature of stage ‡\ larvae. palinuridlarvae were P. japonicas or P. longipesshould be Another 3 larvae had an exopod bud on the 2nd maxilliped underfiuther investigation. and 2 segments on the 5th pereiopod, and could not be Very little is known about the scale and processesof staged. Since the number of larvae examined by Inoue was transportin the ocean of P, japonicas larvae.The problem 197 lies in the ambiguity of species identification of larvae and the smallg number of wild samples collected.