i^ IhilivhiologUi 417: 81-90. 2(KX). i: Alekseev. G.A. Wyiificiard & E D. hemiri leil.s). Adviimes in Ci>pci>Oii ioxonoiny. 
0 2000 Khmer Academic PiMishcrs. Piiiued in llie Nerhcrknuh. 
Patterns of setal numbers conserved during early development of 
swimming legs of Copepoda (Crustacea) 
Frank D. Ferrari 
Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution. Washington, 
DC 20560-0524. U.S.A. 
Kex words: copepod, swimming leg, selalion. development 
Abstract 
During swimming leg development, the number of setae present on the exopod and endopod of the bilobed bud, 
the transformed swimming leg with I-segmented rami and the swimming leg with 2-segmented rami of copepods 
is analysed. For swimming leg I, the most frequent number of setae on the presumptive rami of the bilobed 
bud is found at a higher percentage among copepod .species than the most frequent number of setae for either 
the transformed swimming leg with 1-segmented rami or the swimming leg with 2-segmented rami. However, for 
swimming legs 2-A the most frequent number of setae for the the transformed swimming leg with I -segmented rami 
is found at a higher percentage of species than that on either the bilobed bud or the swimming leg with 2-segniented 
rami. Thus, in the cases of swimming legs 2-4, species with different numbers of setae on the presumptive exopod 
and endopod of the bud bilobed bud develop the same numberof setae on the rami of the transformed swimming leg 
with 1-segmented rami. Increasing the numberof species analysed is expected to make more robust the hypothesis 
that the number of setae on the transformed swimming leg with I-segmented rami is conserved relative to the 
number of setae on the bilobed bud. 
Introduction 
Development of swimming legs 1^ of copepods 
takes place from the last naupliar stage through the 
copepodid phase of development (Ferrari, 1988; Fer- 
rari & Benforado, 1998). The number and kinds of 
changes which may take place in these appendages 
varies among different copepod species. For the spe- 
cies studied here, each pair of swimming legs begins 
development as a contralateral pair of bilobed buds 
armed with setae on the fourth (swimming leg I) or 
third (swimming legs 2-4) somite from the posterior 
somite (bearing the caudal ramus) on the copepod 
body (Ferrari, 1988. 1993). The lobes of the bud are 
the presumptive exopod, lateral or dorsal and pre- 
sumptive endopod, medial or ventral. Each bud is 
transformed during the following molt into a recogniz- 
able swimming leg united to its contralateral twin by 
a coupler attached to their coxa. The rami of the trans- 
formed swimming leg appear I-segmented. During 
the following molt, an arthrodial membrane usually 
separates a proximal and a distal .segment on both 
the exopod and the endopod. This paper examines 
the different numbers of .setae found on the rami dur- 
ing each of these three early steps in swimming leg 
development. 
Methods 
Data presented here are from an ongoing study of the 
appendage development in copepods; the initial focus 
of the study was on the Cyclopidae (Ferrari. 1998) and 
therefore the data are heavily weighted for that family 
(27 of 64 species in Tables 1 and 2). Development of 
swimming legs I and 2 begins at the last naupliar stage 
when the bilobed bud of these appendages initially ap- 
pears. Information about the last naupliar stage were 
studied for 29 copepod species (Table 1). Subsequent 
development of swimming legs 1 and 2 and the com- 
plete development of swimming legs 3 and 4, takes 
place during the six stages of the copepodid phase of 
development. Descriptions of these stages were stud- 
ied for 3,'i species more (see Table 2), giving a total of 
82 
Tiiblc I. Species for which the complete development ol" all 
swimminn lees is known 
Order Family Genus Species 
ca Clausocalanidae Pseiidocahmus ekmgatus 
ea Paracalanidae Acrocalciiius aibher 
ea Pseudodiaptoniidue Rs('tul(Hliai>fonuis Jorhsi 
ca Tenioridae Teiiioiv kmgicornis 
ca Tortanidae Torlcmiis dextriUthatiis 
cy Cyclopidae Acanthocyilaps Ciinilinitiiui.s 
cy Cyclopidae Acunlhocyclop.s rohiisltts 
cy Cyclopidae Apncyclops (limorphus 
cy Cyclopidae Apocyclops pammwnsis 
cy Cyclopidae Cyclops sciilifer 
cy Cyclopidae Diacyclops lUIVU.S 
cy Cyclopidae Dimychps Ihomosi 
cy Cyclopidae Eucyclops iigilis 
cy Cyclopidae Macrocyclops (ilhidus 
cy Cyclopidae Mcfiacyclops kitipes 
cy Cyclopidae Mesocyclop.s edax 
cy Cyclopidae Mesocyclops kmii'iseUis 
cy Cyclopidae Mkrocyctops nihclkis 
cy Cyclopidae Thermncyclops dccipiens 
cy Cyclopidae Tropocyclops jtimakensi.s 
cy Cyclopidae Twpocyclops prasiiuis 
cy Notodclphyidae Dorpy^iis sechtsiis 
cy Notodelphyidae Nolodelpliys uffiius 
cy Oithonidae Dioillioiui ociiliiki 
cy Oithonidae Linuitiilhdna lelraspbm 
h Canuellidae Coiilkiiui cwuidensis 
h Longipediidae Ltmgipnlui americaiui 
h Miraciidac Macrosetallei f;iacilis 
s Asterocheridae Scoltomyzon ^ibberum 
Ttibk' 2. Species lor which data about the hilobed bud of 
swimming legs 1 and 2 on naiiplius 6 is unknown; only the 
copepodid phase of development is known 
ca = Calanoida.  cy 
Siphonostomatoida. 
Cyclopoida.   h = Harpaclicoida, 
64 species for these stages. The results for swimming 
legs 2-4 are presented first; the results for swimming 
leg 1 are presented last because swimming leg 1 differs 
significantly from swimming legs 2-4 in the early set- 
ation of the leg bud and the setation of the transformed 
leg (Ferrari & Benforado, 1998). 
Results 
Twenty-two of 29 species (76%) bear three setae on 
the presumptive exopod and two setae on the pre- 
sumptive endopod of the bilobed bud of swimming leg 
2 which is present at last naupliar stage. Three other 
combinations are expressed among the eight other spe- 
cies studied here (Table 3). Fifty-six of 64 species 
Order Family Genus Species 
ca Acartiidae Accirlia spiruitd 
ca Aetideidae Emhhellci messinensis 
ca Centropagidae Boeckelki poopoensis 
ca Diaptomidae Skislodicipumni.s pyf^nuieiis 
ca Euehactidae Eiichaelu iiieiliii 
ca Lucicutiidae IjicicKlid i^rondis 
ca Metridinidae PU'ttronuiniiihi xiphias 
ca Phyllopidae PhyUopus heljitie 
ca Ridgcwayiidae Rkls<e\\uyki klmisnielzleri 
cy Cyclopidae Alktcxilop.s silvalicus 
cy Cyclopidae Alkicyck>ps sp. 
cy Cyclopidae Bnocychps caroli 
cy Cyclopidae Dimyckips dispinosus 
cy Cyclopidae Diacyclops eulilondis 
cy Cyclopidae Gniewrielki brehmi 
cy Cyclopidae Halicyclops (ibernms 
cy Cyclopidae Mesocyclops niiiieri 
cy Cyclopidae Mifscocyclops opercukiliis 
cy Cyclopidae Neocyclops viciniis 
cy Cyclopidae Panicyckips cbiltoni 
cy Cyclopidae Speocyclops nicovitzai 
cy Cyclopidae Slolonicyclops hef>f;ieiisis 
cy Cyclopidae Tro^locyclops Janstocki 
cy Cyclopinidae Cyclopiiui coroli 
cy Cyclopinidae Procyclopimi fciiiceini 
cy Notodelphyidae Scolecodes lunusiiumi 
cy Oithonidae Oilhoiui similis 
cy Oithonidae Oilhoiui simplex 
h Metiidae Metis sp. 
P Clausidiidae Conchyliiinis quiiUus 
P Clausidiidae Hemicyclops adherens 
P Clausidiidae Leplinoi^iiswr nuijor 
P Corycaeidae Corycaeus angelictis 
P Myicolidae Midicoki spinosiis 
ca = Calanoida.  cy = Cyclopoida. 
Poccilostomatoida. 
li = Harpaclicoida,  p 
(88%) bear seven setae on the exopod and six setae 
on the endopod of the transformed swimming leg 2 
with 1-segmented rami, which is present at copepo- 
did I. Eight species express three other combinations 
of setae on the exopod and the endopod (Table 3). 
For 36 of 64 species (56%), swimming leg 2 has a 
2-segmented exopod with one seta on the proximal 
segment and seven on the distal segment and a 2- 
segmented endopod with one .seta on the proximal 
.segment and six on the distal. The species express- 
83 
lahlc X Inriet|uenl combinations of setul niimlieis for liilobed hud. 1 -segmented ranuis and 2-segmeiitctl ramus stages of s\v imining leg 2 
3& 1 
2&2 
I & 0: 
Presumptive Re & Presumptive Ri (most frequent is 3 and 2) 
AinHyclops Llimorphiis. A. pamimensis. Micwcyclops nihclliis 
Acniciilwnts i-ihhcr. Psemlocukmiis ekmgurus, Psemlodiuplomiis Jorhsi 
MacroM'li'tUi i^mcilis 
7&5 
7&4 
6 & 5 
6&4: 
5 & 3: 
4&6: 
1-segmcnted Re & 1-segmented Ri (most frequent is 7 and 6) 
CoiilUiiw caniidensis. BryocyclDps ciirnli. Spi'ocyclop.s raaivilzxii 
Corycaeus angelicus 
Umgipedki amerkima 
Macnixelellii givcili.s 
Metis sp. 
Acarlid spiuaui 
7. 1 &7. I: 
7. I &5. I: 
7. 1 &4. I: 
7. I & 5. 0: 
6. 1 &7. I: 
6. 1 &6. I: 
6. I &4. 1: 
6, 1 & 4, 0: 
S, 1 &5, 1: 
5. I & 4. 0: 
7, 1 &8-: 
7. I & 7 -: 
7. I & fi -: 
8-&6-: 
2-segmented Re & 2-scgmcntcd Ri (most frequent is 7 distal and I proximal, 
and 6 distal and 1 proximal) 
PsemUidkipldimis forhsl. Ridgewayia kkiusnu'tzleri. Ti>ruitnis de.xirikilninis 
Gnu'lerielUi hiclimi. MiisciHytk>ps openiduliis. PnxyckipiiHi feilkeini. Dkicyckips 
t'lilitorulix, Slok>nicyck>ps heggiensis 
Bryocy<k>ps ccimli. Speocydops nwovilziii. Corycaeus iingeliens 
Scolecndes hunlsiiiiini 
Skisliidiiiploiiiiis pygnuieiis 
Cyclopinci caioli. Oiihomi siniilis 
Coulkma cwuidensis 
MiHioselelki gnicilis 
Umgiped'ui cimerii ima 
Metis sp. 
Phyllopiis lielgiie. Pleiiromamimi xiplticis. Boeikellii pi)opi)eiisis 
Liicicniia grandis. ieniora Ittngicttniis 
Pseiidmalaiuis elongutus. Euchirella messiiu-iisis 
Euchaeta media 
Acartia spiiuila 
Re = exopod; Ri = endopod; a dash indicates tliat the anhrodial membrane is not formed between proximal and distal segment. 
ing the fifteetT other combination.s are li.sted in Table 
3. These include five species in which the endopod 
remains I -segmented and the exopod of two of the five 
also remains 1-segmented. 
Thirty-three of 64 species (529!-) bear three setae 
on the presumptive exopod and two setae on the pre- 
sumptive endopod of the bilobed bud of swimming 
leg 3: this bilobed bud is present at copepodid I. The 
remaining species express six other combinations of 
setae on this bilobed bud (Table 4). Fifty-two of 64 
species (81%) bear seven setae on the exopod and 
six setae on the endopod of the transformed swim- 
ming leg 3 with 1-segmented rami which is present 
at copepodid II. Twelve species express seven other 
combinations of setae (Table 4). For 38 of 64 species 
(59%), swimming leg 3 with 2-segmented rami has 
an exopod with one seta on the proximal segment and 
seven on the distal segment and an endopod with one 
seta on the proxiinal segment and six on the distal .seg- 
ment. Species expressing the 14 other combinations 
of numbers are listed in Table 4. These species include 
eight in which the endopod remains 1-segmented and 
for two of these latter eight species the exopod also 
remains 1-segmented. Examples of swimming leg 3 
are shown in Figures 1-3. 
Twenty-nine of 64 species (45%) bear three setae 
on the presumptive exopod and two setae on the pre- 
sumptive endopod of the bilobed bud of swimming 
leg 4; this bilobed bud is present at copepodid II. The 
remaining species express six other combinations of 
setae (Table 5). Forty-six of 64 species (72%) bear 
seven setae on the exopod and six setae on the endopod 
84 
Tiihic 4.  Infrctiuciil coinbinulions ol'sclal numbers for hilobed bud. 1-scgmenled ramus and 2-segnien(ed ramus stages of swimming leg 3 
Presumptive Re & Presumptive Ri (most frequent is 3 and 2) 
3 & I: Tivpocyclops Jatiiaiccn\is, 7". prcisinus. Apocyclops [Hnuinwn.sis. A. (liinciphii.s. Gnwtt'rii'tla 
hrelimi. Corycoeii.s on^eticus 
3 & 0: Panicyclops chillimi. Spcocychips raciniizai. Dimyclops culiloialis. Slolimicyclops Iwiifiicitsis. 
Metis sp. 
2 & 2: Acmccikniiis t>ihber. Psc'iulociilaniis ehiiifialus. PseudihliapKimus foihsi 
2& I: Allmyclops sp.,Midicola spiiwxiis 
2 & 0: Allmyclops silvaticii.s, Bryocyctops caroli, Muscocyclops opi'iriilauis. Emyclops anilis. 
Ncoiyclap.', viiinii.s. Conchylinnis i/iiiiinis. Leplinoj'aster major, Scoltoinyzoii gibbenini. Hcniicyclop.', 
Mlheirits 
1 & 0: Cyclopiiiii caroli, Hulicyclops uherrcms, Troiilocyclops jimsioiki. Hcrnmmnellu saxiilomi 
7&S: 
7&2: 
6&6: 
6&5: 
6&4; 
5&4: 
4&6: 
I-segmented Re & 1-segmented Ri (most frequent is 7 and 6) 
Spt'ocyclops racinilzai. Scolcctidcs luinsliiiani. Hcrrmunnella saxidomi. Scdiinmyzon }iil>l>eriiiii 
Corycaeus anj>elicus 
Skixtodiaptomus pynmueiis. Oillioiui siniilis 
Um^ipediu umericimu 
Miicroselelhi gmcilis. Metis sp. 
CoiilUiiia (wiiideitsis 
Acarlici spinata 
2-$egmented Re & 2-segmented Ri (most frequent is 7 distal and I proximal, 
and 6 distal and 1 proximal) 
7. 1 & 7. 1: Boeckelki poopoeiisis. Ridi^e^dyia kkiiisnielz.leri. Pseiidodiapiomiis forbsi 
7, 1 & .'>, I: Bryocyctops ciiroli female. Diucyclops culitoriilis. .Sloloiiicyctops hci;i;ieiisis. 
Muscocyclops opcrcuhitiis. Ptvcychipinti feiliccira. Macroscicllo ^riicilis. Henindiim-lla saxidomi. 
Scoltomyzvii fiiblwritiii 
7. I &4, I: 
7. 1 &2, I: 
6. I & 7. I: 
6. I & 6. I: 
?"S. I &5. 1: 
-?i. I & 4. I: 
4. I & 3. I: 
7. I & 8 -: 
7. I &7-: 
8-&7-: 
6-&4-: 
5-&7 -: 
Speocyclops racovilzni 
Corycaeus aiif>eliciis 
Skislodiaptomits pyniitactis 
Oithoiia siniilis 
Lonfiipedia umericima 
Metis sp. 
Coiillami caiiadeiisis 
Phyllopiis helf;oe. Pleiinimammu xiphias. Torlaniis ilexiriliil'altis 
Liicicutia tfrandis, Eiichaetd media 
Temora longicoriiis 
Scolecodes hinitsniani 
Acarlia spinata 
Legend as for Table 3. 
of the transformed swimming leg 4 with 1-segmented 
rami. which is present at copepodid III. Eighteen spe- 
cies express twelve other combinations of setae (Table 
5). For 32 of 64 .species (50%), swimming leg 4 with 
2-segmented rami has an exopod with one seta on 
the proximal segment and nine on the distal segment 
and an endopod with one seta on the proximal seg- 
ment and six on the distal. The remaining species 
expressing combinations are listed in Table 5. These 
include seven species in which the endopod remains 
I -segmented and three of these seven species have a 
I -segmented exopod. 
Twenty-two of 29 species (76%) bear four setae 
on the presmnptive exopod and two setae on the pre- 
sumptive endopod of the biolobed bud of swimming 
leg I. This bilobed bud is present at the last naupliar 
stage. The remaining species express five other com- 
binations of setae (Table 6). Forty-one of 64 species 
85 
Tiihic 5.  Inrrcqucnl CDiiihinations Dl'sctal luirnhcrs lor hilobed hud. 1-scyniLMilccI ranuis and 2-scgrnented raiiius 
stages of swimming leg 4 
Presumptive Re & Presumptive Ri (most frequent is 3 and 2) 
3 & I: iropdcycliips januuii.'iisis. T. pnisiints, Eucyclops agilis, Micwcytiops rubcllus.Apocyclops 
ilifnorpliifs. A. piintinwnsis. ClmeWriella Ij/'chini 
3 & 0: Panuychips diilloiii. Bryocyclop.s ciimli. Dicuyclop.s ciililoiiilis. Speocyclitps nwovilziii. 
Sloloiiicyclops lieni^icnsis. Metis sp. 
2 & 2: AcnicaUiiuis fiihhcr. Psi'iulncaUiinis cl<)iif;tini.s. PseiiclocliapkiDiiis foibsi 
2 & I: AHiicycltips sp.. Miilicoki spinosiis. Saiiloniy-oii f^ibheniin 
2 & I): Nemyclop.s viciinis. Alhicyilops silvaticiis Miiscocyclops opeiviiluliis. Conchyliiinis ipiiiiliis. 
Hemicyclops iidheren.s. Leplinogcisler major. Coiillciiui ccmculensis 
I & 0: Cyclopiiw caroli. Troalocyclop.s janslocki. Hulkyclops ubcinms. Noloclelpliys (ijjiiii.s. 
Sciilecddcs hiinsimwii, Doropygus seilitsus. Heirmaimella scixidomi. Corycaeiis cmf;elici{.\ 
1-sesmented Re & 1-segmented Ri (most frequent is 7 and 6) 
7 & .>: liryocyclaps ciinill. Speocyclop.s nicovilzcii 
7 & 4: MacroseielUi i^nicilis. ScolUiiny:(in aibbcnim 
7 & 3: Hcrrnuiniu'llii snxiiioini 
6 & 6; Ncoiycbips v'uiiuis. lu'pliiiof^ii.slcr inajor. SkisUHiuipkiiinis pyj'imu'iis 
6 &. 5: Allotyrlops silvalkits. Miiscinyclop.s openiiltinis 
6 & 4: Metis sp. 
6 & I: Corycaeiis angelivus 
fi & fi: Oithoiui siiiiilis 
5 & 5: Doropy^iiis seclusus 
5 & 4: Coiillaiui caitaileiisis. Loiiaipeilici aiiiericaiiii 
4 & 6: Acarlia spiiiatii 
I & 0: ScdU'codes hi(iistiiuiiii 
2-segmented Re & 2-segmented Ri (most frequent is 9 distal and I proximal, 
and 6 distal and I proximal) 
9. 1 & 7. 1:      Acrocahmtis i^ibber. Boeckella poopoeiisis. I'hyllnpiis hcliiiie. Ridnewuyia kUnisriietzleri. 
Pseiidodiuplomiis forbsi 
9. I & 5. I:      Diacyclops eiilitonibs 
9, I & 4. I:      Scotloiiiyzoii nibberuiii 
9. I & 3. I:      Herrmannelki saxidomi 
8. I & 7. I:      Skisiodiapioiiiiis pyi;iiiaeiis 
8. 1 & 6. I:      Apocyclops diinorphus. A. ptiniimeiisis, Gruelericlki brehini, Mierixyclops nibelkis. 
Leptlnoi(tister major. Muerosetella i^riirHis 
7. I &5. 1:      AlkHyekips sp..A. sil\'aliii{S 
7. I & 4. 1:      Bryocyclops caroli male. Metis sp. 
6. I &4. I:      Muscocyckips open ukilus. Speocyclops racovitzai 
6. I & .S. I:       Loiifiipedia amcricanci 
6, 0 & 6. I:      Oithona similis 
3. I & 4. I:      CtmlUmn caiiadettsis 
9. I & 8 - :       PU'iiroiiKiiiima xiphias 
9. I & 7 - :       Halicyclops aberraiis 
9. I & 3 - :       Bryocyckips caroli female 
9, I & 2 -:       Corycaeiis aiif>eliciis 
7. I & 6 -:       Stolimkyclops beggiensis 
10 - & 7 -:        Temora loiif'icornis. Scolecodes liiiiilsiiuiiii 
6 - (St 7 -: Acarlia spiiuiia 
Legend as for Table 3. 
86 
liihk' 6.  Infrequent combinations of sotal numbers lor bilobed bud. 1 -segmented ranius and 2-segmented ramus stages of swimniing leg I 
Pri'sumptivt Re & Presumptive Ri (most frequent is 4 and 2) 
4 & 3: Torkiniis ilexliilohciltis. Temom loiifikiinus 
3 & 2: Cmilkma cimiulciisis 
2 & 3: AcrociiUuiiis I'ihher. Psi'tiildiulaini.s elcmiialiis. Psemloilkipumuis foi'hsi 
0 & 0: MucmseU'lki i;nicili.s 
1-segmented Re & 1-segmented Ri (most frequent is 8 and 7) 
8 & 6: /\lkHych>ps sp.. A. silvuikii!,. Grueleiielkt brchim. Pnicyclnpiiui k'ilicciw. Coutkma 
cuniuleiisis. Pkylkipu.s liclfiae. Liitkutia ^nmilis. Corycaeu.sangelicii.s 
5 & 5: Bryocycltips caroli. Spcocyclop.s nicorilzai. Saik'coilcs liiiiisliiKini 
7 & 7: Pxeiukuliuplonuis forhsi 
1 & &. Sldkmicyckipx hegi>iensis 
1 & 5; liiuliiri'lki iiwssiiu'if.six. Miiscocyckips openiikiliis. hiiifiipediii wnericwxi. Pseiitlocakinus 
ekmsiiilux 
6 & 7: Skistodkiptoiiuis pyiimaciis. Tortiiinis ik'xlrilohiitii.s 
ft cS: 6: Acrociiluiuts s>ihher 
ft & 5: Emhaehi iiieilki 
6 & 2: Metis sp. 
4 & 3: Macrosetella ^racilis 
2-scgmcnted Re & 2-segmented Ri (most frequent is 8 distal and 1 proximal, 
and 7 distal and 1 proximal) 
8. 1 & 6. I: Apocyckips iliniiirpliKS. A. paminwnsis. HaUiyckips ahcnwis. Neocyckips vicinii.s 
Punuyckips chilloiii. Microcycktps nihelliis. Diacyilops culiuintlis. Dioitkomi ociikitu. Oilliima simiks, 
O. sknpk'x, Umnoilkomi telnispiiw. Nounlelpkys ajjini.s, Uawpyfiiis seckisus. Cyckipiiui cumli. 
Coiuhyliiinis qiiinliix. Heniminnella saxidomi. Leplinogasler major. Miclkaki spinosus. CouUunii 
ccmademis. Bocckelki poopoensis. Pseudkiplonnis forhsi. Acartia spiniila 
8, I &5. I: Alk)c\ck>px !ip.,A. silvaliciis, Graeterielki brckmi. Procyclopkui feilkeirci. Corycacii.s 
iiiii^fkciis 
8, 1 & 4. 1: Bryotyck)ps carok 
7. I & 4. I: Miiscocyckips operciiknus. Spcocyckips wcovilzxii. Loiif^ipedki iiincricaiui 
7. I & ."i. I: Slokmicyckips keiifiiensis 
1. 0 & ."i. I:                            Acmcakiniis f^ihher 
6. 1 & 6. I: Skislodiiipumnis pyfiiiuiciis 
5. I & 2, 0: Meris sp. 
4. 0 & 2. I: Mticmselelki gracilis 
8, I & 7 -; Pkyllopiis kelffae. Teinora kini^iconiis 
8. 1 & 6 - :                               Lucicutia ^irandis 
7. I & 5 -; Scolecodes huntsmimi. Pseiuliniiloiui.s ekiiii^alus 
7. 0 & 8 - : Tortimiis dexlrikihaliis 
8 - & 5 - : Eiichirclki inessiiwnsis 
7 - & 5 - : Eiuluieta lueditt 
Legend as for fable 3. 
(64*^) bear eight setae on the exopod and seven setae pod with one seta on the proximal segment and eight 
on the endopod of the transformed swimming leg I on the distal segment and an endopod with one seta 
with I-segmented rami, which is present at copepodid on the proximal segment and .seven on the distal. Spe- 
I. Twenty-three species express five other combina- cies expressing fifteen other combinations are listed in 
tions of setae (Table 6). For 20 of 64 species (31%), Table 6. Ainong the.se are eight in which the endopod 
swimming leg 1 with 2-segmented rami has an exo- remains 1-segmented and one of these al.so has a I- 
87 
Fii>iir(' I. Thermocyclopx ilecipien.s leg 3. (A) bilobed bud al cope- 
podid I; (B) iransforinod swimming leg with I-segmented rami at 
copepodid II: (C) swimming leg with 2-segmentcd rami at cope- 
podid III. Line I for A. B and line 2 for C are O.O.'i mm. External 
setae oC the exopod eoniplete: terminal seta of the exopod with oval 
eiitoff: all other setae with wa\y line eutoff. Dotted outline within 
rami indieales exoskeleton of the following developmental stage. 
Figure 2. Eiicyclops iii>itis leg 3. (A) bilobed bud at eopepodid I 
[presumptive endopodal lobe with one seta); (B) transformed swim- 
ming leg with 1-segmented ranii at copepodid 11; (C) swimming leg 
with 2-segmented rami at copepodid III. Line I for A. B and line 2 
forC are O.O.'i mm. Rxternal setae of the exopod complete; terminal 
seta of the exopod with oval cutoff; all other setae with wavy line 
cutoff. 
segmented exopod. Examples of swimming leg I are 
shown in Fiizuies 4-6. 
Discussion 
The most tVequent combination of sctul numbers on 
the bilobed bud (3 on the exopod and 2 on the endo- 
pod). the transformed swimming leg with 1-segmented 
rami (7 on the exopod and 6 on the endopod) and the 
swimming leg with 2-segmented rami (1 proximal and 
7 distal on the exopod and I proximal and 6 distal on 
the endopod). arc identical for swimming legs 2 and 
3. However the most frequent combination for swim- 
ming leg 4 with 2-segmented rami (1 proximal and 9 
distal on the exopod and 1 proximal and 6 distal on 
the endopod) differs from swimming legs 2 and 3. Fer- 
rari & Benforado (1998) suggest that the 2-.segmented 
exopod of swimming leg 4 represents two contiguous 
steps in development of swimming legs 2 and 3. Com- 
bining these two steps results in the early allocation to 
the distal segment of the two setae which will arm the 
middle segment of the exopod of the adult. 
For swimming leg 1, the bilobed bud, the trans- 
formed swimming leg with 1-segmented rami and the 
2-segmented rami are quite different from the other 
swimming legs. Swimming leg 1 of copepods differs 
from swimming legs 2-4 because as many as four 
setae may be present on the presumptive exopod of 
the bilobed bud and as many as three setae inay be 
present on the presumptive endopod (the latter restric- 
ted to Calanoida). The iransformed switnming leg 1 
with I-segmented rami differs from swimming legs 2- 
4 because as many as eight setae may be present on 
the exopod and as many as seven setae may be present 
on the endopod. Ferrari & Benforado (1998) suggest 
that the extra setae, the eighth on the exopod and the 
seventh on the endopod of the transformed swimming 
leg 1 with I-segmented rami. will be allocated to the 
middle segment of each ramus on the adult. Setae 
serially homologous to those allocated to the tuiddle 
segment of each ramus on the adult appear later in 
development of swimming legs 2?4. 
88 
Figure J. Torkmus clextrilohatus leg 3. (A) bilobcd bud at copc- 
podid I; (B) transformed swimming leg with l-segmented rami at 
copepcxiid II: (C) swimming leg with 2-seginenled rami at copepo- 
did HI lendopod remains I-segmented]. Line 1 for A, B is 0.05 mm; 
line 2 for C is 0.1 mm. Remainini; leaend as lor Figure 2. 
h'ifliire 4. Apocycliips pwuimensis leg 1. (A) hilobed bud at naupliiis 
6; (B) transformed swimming leg with l-segmented rami at eope- 
podid I; (C) swinnning leg with 2-segmented rami at eopepodid II. 
Line 1 for (A) (B) (O is O.O.'i mm. Remaining legend as for Figure 
Bud 1 -segmented rami 2-segmented rami 
76 64 31 
76 88 56 
52 81 59 
45 72 .50 
Figure 5. Acrovahiinis gibber leg I. (A) bilobed bud at nauplius 6 I 
Ipresumplive exopodal lobe with two seta|; (B) transformed swim- 
ming leg with l-segmented rami at eopepodid I; (C) swimming leg 
with 2-segmented rami at eopepodid 11 (endopod remains l-segmen- 
ted]. Line 1 for (A) (B) and line 2 for (C) are 0.05 mm. Remaining 
legend as for Figure 2. 
Table 7. The pereeniage of the most frequent eonibinations of selal 
numbers among all species studied for the ihiee early stages in 
development of swimming legs 1^ 
Leg 
1 
2 
3 
4 
For swimming leg 1. the most frequent comhin- 
ation of setal numbers for tiie exopod and endopod 
of the bilobed bud is found in a higher percentage of 
species than the progressively decreasing percentages 
for the most frequent combination on the transformed 
swimming leg with l-segmented rami or the swim- 
ming leg with 2-segmenled rami (Table 7). This se- 
quence appears logical because the larger number of 
setae present in the later two steps of development (up 
to 15 for the 1 -segmented leg 1 and up to 19 setae for 
the 2-segmented leg 1, or up to 13 for the 1 -segmented 
leg 2 and up to 15 setae for the 2-segmented leg 2) 
should provide more opportunity for variation than the 
89 
Fii>iin' 6. Tenioni Iniif^iainiix log 1. (A) bilobccl hud at nauplius 6; 
(B) Iransrormed swimming leg wilh l-segmentcd rami at copcpodid 
1: (C) swimming leg wilh 2-scgmented rami al copepodid II jendo- 
pod remains l-segmonlcd]. Line I rur(A) (B) and line 2 lor (C) are 
0.05 mm. Rejnaining legend as lor Figure 2. 
six or seven setae present on the bilobed bud of leg 1. 
or the five setae present on the bilobed bud of leg 2. 
However, this sequence of decreasing percent- 
ages as development progresses is not expressed for 
swimming legs 2^. For these three legs, the most 
frequent combination of setal numbers on the exopod 
and endopod of the transformed swimming leg with 
l-segmentcd rami occurs in a higher percentage of 
species than the most frequent combination for either 
the bilobed bud or the swimming leg with 2-segmented 
rami (Table 7). That is, several species each with a 
different combination of setal numbers on the bilobed 
bud have the same combination of setae on the trans- 
formed swimming leg with 1-segmented rami. For 
example, Eiicyclops cigilis, Tropocyclops jaimiicensis 
and T. prasiiiiis with 3 setae on the presumptive ex- 
opod and I seta on the presumptive endopod of the 
bilobed bud of swimming leg 3, Parucyclops chiltoni 
with 3 .setae on the presumptive exopod but without a 
seta on the presumptive endopod of the bilobed bud 
of that leg and Heinicyclops adherens and Cmillaiut 
camidensis with 2 and no setae respectively (Table 
5) are transformed into a swimming leg 3 with 7 
exopodal and 6 endopodal setae on the 1-segmented 
rami. This is the most frequent combination for that 
step of development. So for swimming legs 2-4, the 
transformed swimming leg with I-segmented rami, 
rather than the bilobed bud. has setal numbers better 
conserved among these copepods. 
As noted earlier, the data analysed here are heav- 
ily weighted for species of Cyclopidae. It is reason- 
able to expect that the above results might change 
as data for more copepods are analysed. The addi- 
tion of more copepods from two orders may result in 
significant changes. The harpacticoid species presen- 
ted here, Macrosetella gracili.s. Coiillana camiden- 
sis, and Longipedia americana. usually have a lower 
number of setae on any ramus than the most fre- 
quent combination found in this study. Including more 
harpacticoids may be expected to increase the num- 
ber of different combinations for both rami so that the 
percentage of the most frequent combination among 
all included copepods will decline. Inclusion of more 
calanoids will differentially reduce the most frequent 
combination for the bilobed bud of leg 1 because 
most calanoids can be expected to have four setae 
on the presumptive exopod and three seta on the pre- 
sumptive endopod of the bilobed bud of swimming 
leg 1. These calanoid bilobed buds are expected to be 
transformed into swimming legs I with 8 exopodal and 
7 endopodal setae, which is the most frequent combin- 
ation found for that transformed swimming leg with 
I-segmented rami. 
Homologies of the setae present in these vari- 
ous combinations will be addressed in a forthcoming 
study. For combinations of relatively large numbers of 
setae on the exopod plus endopod (3 and 2, 7 and 6, or 
7 distal and 1 proximal and 6 distal and 1 proximal on 
swimming legs 2-3; 3 and 2, 7 and 6, or 4 distal and 
1 proximal and 6 distal and I proximal on swimming 
leg 4; 4 and 2-3, 8 and 7, or 8 distal and 1 proximal 
and 7 distal and 1 proximal on swimming leg 1), setae 
are homologous among species expressing the same 
combination. Problems with homology exist for some 
combinations of relatively smaller numbers of setae. 
The resolution of setal homologies should increase the 
number of combinations with relatively fewer setae 
and reduce the percentage of each combination. The 
addition of more species and the resolution of setal 
90 
homologies should make more robust the hypothesis 
that the combination of seta! numbers for the trans- 
formed swimming leg with 1-segmented rami is better 
conserved among copepods than the combination for 
the bilobed bud. 
White. Karen Wishner, Grace Wyngaard and the 
BATS study at the Bermuda Biological Station for 
Research. 
References 
Acknowledgements 
For living or preserved specimens, I would like 
to thank Bernardo Abiahy. Victor Alekseev. Ruth 
Boettger-Schnack. Edward Buskey, Paul Fofonoff. 
Audun Fosshagen, Ju-shey Ho, Arthur Humes, Teruo 
Ishida, Viatcheslav Ivanenko, 11-hoi Kim, Fran- 
coise Lescher-Moutoue, Wolfgang Janetzky, Wim 
Kimmerer, Wim Klein Breteler, Darcy Lonsdale, Guil- 
herme Lotufo. Gerald Marten, David McKinnon, 
James Orsi, Juan Cesar Paggi, Janet Reid, Carlos 
da Rocha. Klaus Ruetzler, Josefin Titelman, Susan 
FciTari. F. D.. 1988. Developmental palterii.s in numbers of ranial 
segmenis of copepod posl-maxillipedal legs. Crustaceana .'54: 
2.56-29.1. 
Ferrari. F, D.. 199.1. Exceptions to the rule ol' development thai 
anterior is older among serially homologous segments of post- 
maxillipedal legs in copepods. J. Crust. Biol. 1.1: 76,1-768. 
Ferrari. F. D.. 1998. Setal developmental patterns of the thoraeopods 
of eyclopid copepods (Cyclopoida) and their use in phylogenetie 
inlerenee. J. Crust. Biol. 18: 471^X9. 
Ferrari. F. D. & A. Benforado. 1998. Relationships between arlh- 
rodial membrane formation and addition of setae to swimming 
legs \-4 of Dioilluina ociilalii. Ritlf'i'wayia kUiiisnielzleri. Pleiir- 
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