COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI (COPEPODA, CALANOIDA) AND THE RELATIONSHIP OF PSEUDOCYCLOPIDAE TO OTHER CALANOIDS

Transcription

1 COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI (COPEPODA, CALANOIDA) AND THE RELATIONSHIP OF PSEUDOCYCLOPIDAE TO OTHER CALANOIDS FRANK D. FERRARI 1 ), SUPAWADEE CHULLASORN 2 ) and HANS-UWE DAHMS 3,4 ) 1 ) IZ/MSC; MRC-534, National Museum of Natural History, Smithsonian Institution, 4210 Silver Hill Rd., Suitland, MD 20746, U.S.A. 2 ) Department of Biology, Faculty of Science, Ramkhamhaeng University, Bangkapi, Bangkok 10240, Thailand 3 ) Green Life Science Department, Sangmyung University, 7 Hongij-dong, Jongno-gu, Seoul , South Korea ABSTRACT Five immature copepodid stages of Pseudocyclops schminkei are described. The adult prosome is completed during the molt to copepodid III; the adult urosome during the molt of the last immature stage to CVI. Thoracic somites 5 and 6, bearing swimming legs 4 and 5, are transformed from narrow somites of the urosome of copepodids I and II into broad somites of the prosome during the molts to copepodid II and III, respectively. The exopod of antenna 2 is patterned during the copepodid phase of development. The basis of the maxilliped of copepodids includes two well-developed endites. Buds of swimming legs 3 and 4 do not have apical setae but rather attenuations [cf. spiniform outgrowths] of the bud, in number corresponding to the setae of many calanoids. Transformed limbs of swimming legs 1-4 bear the maximum number of setae reported for these limbs among copepods. Sexual dimorphism is evident at copepodid IV in the morphology and armature of leg 5. The endopod of the male swimming leg 5 does not articulate with the basis at copepodids IV and V. Von Vaupel Klein s Organ, an apomorphy for calanoids, is assumed to have been present on the ancestral pseudocyclopid and is secondarily lost on its extant species. An analysis of several of these characters suggests that Pseudocyclopidae is the oldest extant calanoid family. RÉSUMÉ Cinq stades copépoditiques de Pseudocyclops schminkei sont décrits ici. Le prosome adulte est mis en place au cours de la mue donnant le copépodite III et l urosome adulte lors de la mue du dernier stade immature (CV) au stade CVI (adulte). Les somites thoraciques 5 et 6, qui portent les pattes natatoires 4 et 5 sont transformés à partir des somites étroits de l urosome des copépodites I et II en larges somites du prosome au cours des mues donnant les copépodites 4 ) hansdahms@smu.ac.kr Koninklijke Brill NV, Leiden, 2011 Studies on Freshwater Copepoda:

2 150 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA II et III, respectivement. L exopodite de l antenne se forme peu à peu au cours des stades copépoditiques (phase copépoditique du développement). Le basipodite du maxillipède des copépodites possède deux endites bien développées. Les ébauches des pattes natatoires 3 et 4 ne portent pas de soies apicales mais plutôt des prolongements tissulaires (ou excroissances spiniformes) en nombre correspondant aux soies de nombreux calanoïdes. Les appendices correspondant aux pattes natatoires 1 à 4 portent le nombre maximal de soies connues sur ces appendices chez les copépodes. Le dimorphisme sexuel est évident dès le stade copépodite IV par la morphologie et l armature de la P5. L endopodite de la patte natatoire P5 du mâle ne présente pas d articulation avec le basipodite chez les copépodites IV et V. L organe de Von Vaupel Klein, une apomorphie chez les calanoïdes, est supposé avoir été présent chez le pseudocyclopide ancestral puis secondairement perdu chez les espèces actuelles. Une analyse de plusieurs de ces caractères suggère que les Pseudocyclopidae constitueraient la plus ancienne famille des Calanoïdes actuels. ZUSAMMENFASSUNG Alle fünf Jugendstadien (= Copepodit Stadien) von Pseudocyclops schminkei werden beschrieben. Der Erwachsenenzustand des Prosoma ist mit der Häutung zum Copepodit III erreicht; der des Urosoma nach der Häutung des Copepodit V zum Copepodit VI. Die Thoracomere 5 und 6, die die Schwimmbeine 4 und 5 tragen, transformieren von schmalen Somiten des Urosoma von Copepodit I und II zu breiten Somiten des Prosoma nach den Häutungen zu den Copepoditen II bzw. III. Der Aussenast der Antenna 2 wird während der Copepoditenentwicklung ausgebildet. Die Basis des Maxillipeden aller Copepoditstadien trägt 2 starke Endite. Die Anlagen der Schwimmbeine 3 und 4 tragen noch keine abgegrenzten distalen Borsten, sondern Auswüchse, die in der Anzahl den Borsten älterer Stadien gleichen. Transformierte Extremitäten der Schwimmbeine 1 bis 4 tragen die höchste Anzahl von Borsten die von Copepoden bekannt sind. Geschlechtsdimorphismus wird ab dem Copepoditen IV in Gestalt und Bewehrung der Extremität 5 erkennbar. Der Innenast der männlichen Extremität 5 ist noch nicht frei beweglich an der Basis bei den Copepoditen IV and V. Die Autoren nehmen an, daß Von Vaupel Klein s Organ, eine Apomorphie der Calanoida, bei ursprünglichen Vertretern der Pseudocyclopidae vorhanden war, aber bei den gegenwärtig bekannten Vertretern sekundär verloren gegangen ist. Die nähere Untersuchung von mehreren phylogenetisch informativen Merkmalen legt die Annahme nahe, dass das Taxon Pseudocyclopidae die älteste rezente Familie der Calanoida darstellt. INTRODUCTION For organisms with larval development, different developmental stages may have a divergent biology and ecology, providing challenges for ecological and evolutionary studies. In phylogenetic studies, larval stages may provide an important source of characters (Dahms, 2004a, b) that often are overlooked in analyses restricted to the adult stage. Evidence from larval development may complement those gained from adult characters if larvae provide a significantly different source of morphological, behavioral, and ecological characters. Larval characters can be used as species-specific character patterns in evolutionary

3 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 151 scenarios (Dahms, 1991), or as plesio-/apomorphies in cladistic analyses. Gradients of character states, i.e., morphoclines, can be traced from larval character states, providing useful insights into homologies of complex characters. Gradients also may provide a polarity criterion for the direction of transformation of character states during evolution (Dahms, 2000). Even more valuable in this respect are gradients of character states that recapitulate former character states in the course of ontogeny. The post-embryonic development of copepods is divided into two larval phases, a naupliar phase and a post-naupliar or copepodid phase (Ferrari & Dahms, 2007). During the copepodid phase, copepods develop through six copepodid stages (Dahms, 1993). Thoracic and abdominal somites usually articulate anteriorly and posteriorly on the copepodid stages, post-mandibular appendages have been transformed, and the naupliar arthrite on the coxa of the antenna does not develop (Ferrari & Dahms, 2007). The first copepodid bears up to nine transformed appendages: three remain from the naupliar phase: antennule, antenna, mandible; and six that have been transformed during the molt to the first copepodid: maxillulle, maxilla, maxilliped, swimming legs 1 and 2, and the caudal ramus. An interpodal bar, a constitutive character of the Copepoda (cf. Claus, 1863) until the discovery of remipedes (Yager, 1981), bridges the contralateral pair of swimming legs 1 and 2; swimming leg 3 is a simple, untransformed setose bud. During the copepodid phase of development, somite number increases one per molt, and size increases; limbs are added to new thoracic somites, initially as setose buds, one stage later than their somite is added to the body, and segment elements are also added to antenna 1 and most thoracic limbs. The first copepodid stage has been hypothesized as the phylotypic stage of the Copepoda (cf. Ferrari, 2003) because several aspects of its architecture are conserved in all podoplean and gymnoplean copepods: the body includes a cephalothorax comprised of five cephalic limbs plus the anterior thoracic somite with its limb, thoracic somites 2-5, which usually articulate anteriorly and posteriorly, the posterior abdominal, or anal, somite, which usually articulates anteriorly. Among the appendages, swimming legs 1 and 2 are always transformed limbs with unarticulated rami, and swimming leg 3 is a setose bud; the posterior abdominal somite bears a transformed caudal ramus (Ferrari & Dahms, 2007). During the copepodid phase of development, the body is patterned from a growth zone located in the posterior abdominal, or anal, somite (Giesbrecht, 1913; Hulsemann, 1991). New somites are formed anteriad and are initially

4 152 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA presented adjacent to the anal somite as one new somite at each new copepodid stage. Segment elements of copepod appendages are added from three points during the copepodid development: the protopod is patterned from the point at which the limb meets the body wall so that developmentally older segments and endites of the protopod are always distad, and the basis is the oldest protopodal segment. In addition, each of the two rami may be patterned from at least one source segment with new segmental elements, including setae and arthrodial membranes, added either proximally or distally to the source segment (Ferrari & Dahms, 2007). In the present study, we describe the copepodid stages of Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, a presumed basal calanoid copepod (development of the naupliar stages of P. schminkei will be presented in a separate study). We also analyse several character states and developmental patterns that prove useful in understanding the phylogenetic relationships of this species to other calanoids and to other copepods. MATERIAL AND METHODS Copepodids of Pseudocyclops schminkei were collected with sediment that was removed from an aquarium at Kerama Pearl Ltd., a pearl fishery on Zamami Island, Okinawa, Japan ( N E) on 5 January 2007 and on 15 May The aquarium is used to culture juvenile pearl oysters that are collected locally and maintained in local seawater that is passed through a sand filter before entering the aquarium. In addition to any naturally occurring zooplankton, juvenile pearl oysters are fed a diet of dried artificial food, but this dried food is not considered a source for the copepod ( s from N. Iwasaki, 17 and 21 May 2008). For these reasons, P. schminkei is considered endemic to the area of Zamami Island. The sample with P. schminkei was fixed in ca. 5% neutralized formalin immediately after capture, transferred to 70% ethanol, and subsequently transferred into glycerol for slide preparation. Copepodids were mounted whole or dissected with broken glass-fibres being added to prevent compression by the coverslip and to facilitate rolling so that specimens can be observed from different sides. Line drawings were made with a camera lucida of whole or dissected specimens in glycerol with bright-field or differential interference optics. Body lengths were measured from the anterior to the posterior end of the anal somite; body width is given as the widest part of the cephalosome. Somites are numbered according to their relative developmental age following Hulsemann (1991). The oldest of

5 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 153 these, the thoracic and abdominal somites increase anteriorly from the anal somite during development. Descriptive terms generally follow Ferrari (1995) and Ferrari & Dahms (2007); interpretations of the maxillule, maxilla, and maxilliped follow Ferrari & Ivanenko (2008). The phrase transformed limb is used for the step in limb development immediately after the bud (Ferrari & Dahms, 2007). It was a strictly utilitarian decision that we began with the description of CV and worked back to CI since one can save words by describing stages from oldest to youngest, rather than describing stages from youngest to oldest. Abbreviations are: A1, antenna 1; A2, antenna 2; Abd1-4, abdominal somite 1-4; Ae, aesthetasc; CI CVI, 1 st to 6 th copepodid stages; Cph, cephalosome; CR, caudal ramus; Md, mandible; Mx1, maxilla 1; Mx2, maxilla 2; Mxp, maxilliped; Th1-7, thoracic somites 1-7; Abd, abdominal somites. Ramal segments of swimming legs 1-4 (thoracopods 2-5) are proximal, middle, and distal. Setules are epicuticular extensions of a seta; denticles are epicuticular extensions of an appendage segment. Spiniform outgrowths of limb buds are called attenuations. In order to maintain continuity among descriptive publications, tables of setae and spines on swimming legs 1-4 generally follow the formula introduced by Lang (1934); a semicolon separates ramal segments and an asterisk indicates that the segment has not formed; Roman numerals indicate spines and Arabic numerals are setae; numerals to the left of a comma or dash indicate lateral elements; numerals between two commas are terminal elements, and numerals to the right of a comma or dash are medial elements. Homologous setae cannot be compared from these tables because setae of the presumptive proximal and middle segments of the rami of swimming legs initially appear on the distal segment complex (Illg, 1949; Ferrari & Dahms, 2007). Specimens of all five immature copepodid stages of Pseudocyclops schminkei are deposited with the Smithsonian Institution s National Museum of Natural History. Additional specimens also have been retained by one of us (SC). DESCRIPTIVE PART Order CALANOIDA G. O. Sars, 1903 Family PSEUDOCYCLOPIDAE Giesbrecht, 1893 Genus Pseudocyclops Brady, 1872

6 154 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010 (figs. 1-12) Specimens examined. Ten CV, 10 CIV, 5 CIII, 5 CII, 5 CI separated from aquarium sediments at Kerama Pearl Ltd., a pearl fishery on Zamami Island ( N E), Okinawa, Japan, on 5 January 2007 and on 15 May CVI female and CVI male: see Chullasorn et al. (2010). CV female. Differs from CVI female as follows: Body length range mm; ratio of length of prosome to length of urosome 2.5 :1 (based on 5 specimens). Prosome (fig. 1): 5 parts Cph plus Th1 fused, Th2-4 articulating, Th 5-6 fused. Urosome (fig. 1): 4 parts; Th7, Abd2, 3, 1 articulating. Th7 without copulatory pores or oviducal openings. A1 (fig. 2): 17 articulating segments with 1: 14s + 3a; 2: 2s; 3: 2s; 4: 2s; 5: 2s; 6: 2s; 7: 2s; 8: 2s; 9: 2s; 10: 2s; 11: 2s; 12: 2s; 13: 2s; 14: 2s; 15: 4s; 16: 2s; 17: 6s + 1a. A2 (fig. 3): coxa unarmed; basis with distomedial seta. Endopod 3- segmented, proximal segment with 1 medial seta at midlength; middle segment with 4 setae along medial margin and 4 distomedial setae, and lateral denticles; distal segment with 7 terminal setae, and lateral denticles. Exopod 5-segmented; proximal segment with 1 medial seta; next segment with 2 medial setae and 2 setae distomedially; antepenultimate segment with 2 setae; penultimate segment with 2 medial setae, mid-length and distally; distal segment with a crown of 3 setae. Md (fig. 4): coxal gnathobase with thick proximal seta and 6 teeth-like attenuations [= spiniform outgrowths]; basis with 2 medial setae. Endopod 2-segmented, proximal segment with 3 distomedial setae, distal segment with 8 terminal setae. Exopod 5-segmented, distal segment with 3 setae, remaining segments each with 1 medial seta. Mx1 (fig. 5): praecoxal endite extending distally with 5 thick and 3 thin ventral setae, 1 anterior seta and 4 posterior setae; coxal exite with 4 setae, coxal endite with 3 setae; basal exite with 1 seta, proximal endite welldeveloped with 3 [2 thick, 1 thin] setae, distal endite not extended ventrally, with 3 setae; exopod lobate with 4 lateral and 6 terminal setae; endopod 2- segmented, proximal segment with groups of 4 mid-ventral and 3 distoventral setae; distal segment with 6 terminal setae. Mx2 (fig. 6): praecoxal endite of syncoxa with 5 setae, coxal endite with 3 setae; proximal and distal basal endites with 3 setae each. Endopod 3-

7 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 155 Fig. 1. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, CI CV, habitus, left lateral.

8 156 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA Fig. 2. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, antenna 1, CI CV.

9 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 157 Fig. 3. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, antenna 2, CI CV. segmented; quadrate ventral lobe of proximal segment with 3 setae, middle segment with 1 proximomedial seta and 2 distolateral setae, distal segment with 5 setae.

10 158 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA Fig. 4. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, mandible, CI CV. Mxp (fig. 7) syncoxa with 1, 1, 3 setae on proximal, middle, and distal praecoxal endites, respectively, and 2 setae on coxal endite; proximal endite of basis pronounced, with 3 setae, distal endite small, with 2 setae; endopod 5-segmented with 2 medial, 2 medial, 2 medial, 2 (1 medial, 1 lateral), 4 (1 medial, 2 terminal, 1 lateral) setae. P1-4 (figs. 8-11): Exopod and endopod 3-segmented. Setal and spine formula as in table I. P5 (fig. 12): coxa without setae; basis attenuate distomedially without setae. Proximal exopodal segment with 1 lateral seta; distal complex with 1 lateral

11 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 159 Fig. 5. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, maxilla 1, CI CV.

12 160 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA Fig. 6. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, maxilla 2, CI CV; endopod of CV detached to show setation of middle and distal segments. seta and a crown of 3 setae. Endopod a 1-segmented complex, with a crown of 2 terminal setae. CR: 1 dorsal, 1 lateral seta and 4 terminal.

13 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 161 Fig. 7. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, maxilliped, CI CV. CV male. Differs from CV female as follows: Body length range mm; ratio of length of prosome to length of urosome 2.7 :1 (based on 5 specimens). P5 (fig. 12): intercoxal plate simple. Coxa fused to basis on both limbs. Right exopod 2-segmented; proximal segment with 1 lateral seta, distal with 1 lateral and a crown of 3 setae. Right endopod continuous with basis, with crown of 2 setae. Left exopod 1-segmented, quadrate with 1 lateral seta and

14 162 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA Fig. 8. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, swimming leg 1, CI CV.

15 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 163 Fig. 9. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, swimming leg 2, CI CV.

16 164 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA Fig. 10. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, swimming leg 3, CI CV.

17 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 165 Fig. 11. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, swimming leg 4, CII CV.

18 166 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA TABLE I Spines and setae on swimming legs 1-4 of Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, CV Coxa Basis Exopod Endopod 2 nd 3 rd 1 st 2 nd 3 rd 1 st Leg I-0 I-1, I-1, II-I-4 0-1, 0-2, Leg I-0 I-1, I-1, II-I-5 0-1, 0-2, Leg I-0 I-1, I-1, III-I-5 0-1, 0-2, Leg I-1, I-1, III-I-5 0-1, 0-2, Fig. 12. Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, 2010, leg 5, anterior, CIII CV.

19 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 167 a crown of 2 setae in middle of broad distal margin. Left endopod continuous with basis, with a crown of 2 setae. CIV female. Differs from CV female as follows: Body length range mm; ratio of length of prosome to length of urosome 2.9 :1 (based on 5 specimens). Urosome (fig. 1): 3 parts; Th7, Abd2, 1 articulating. A1 (fig. 2): 15 articulating segments with 1: 8s + 2a; 2: 2s; 3: 2s; 4: 2s; 5: 2s; 6: 2s; 7: 2s; 8: 2s; 9: 2s; 10: 2s; 11: 2s; 12: 6s; 13: 4s; 14: 2s; 15: 6s + 1a. A2 (fig. 3): endopod, middle segment with 3 setae along medial margin and 7 setae in total. Exopodal segment adjacent to proximal segment with 2 setae distomedially. Md (fig. 4): same as in CV. Mx1 (fig. 5): exopod with 5 terminal setae; distal endopodal segment with 5 terminal setae. Mx2 (fig. 6): distal endopodal segment with 4 setae. Mxp: same as in CV. P1-4 (figs. 8-11): exopod and endopod 2-segmented. Setal and spine formula as in table II. P5 (fig. 12): coxa and basis simple, without setae. Exopod 1-segmented with 1 lateral seta and a crown of 3 setae. Endopod 1-segmented with a crown of 2 setae. CIV male. Differs from CIV female as follows: Body length mm; ratio of length of prosome to length of urosome 3.0 :1 (based on 5 specimens). P5 (fig. 12): left exopod with a ventral knob-like protrusion; absent on right exopod. Endopod is fused to basis. CIII. Differs from CIV female as follows: Body length mm; ratio of length of prosome to length of urosome 2.9 :1 (based on 5 specimens). TABLE II Spines and setae on swimming legs 1-4 of Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, CIV Coxa Basis Exopod Endopod 2 nd 3 rd 1 st 2 nd 3 rd 1 st Leg I-0 I-1, III-I-4 0-1, Leg I-0 I-1, III-I-5 0-1, Leg I-0 I-1, III-I-5 0-1, Leg I-0, III-I-5 0-1, 2-2-3

20 168 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA Urosome (fig. 1): 2 parts; Th7 and Abd1 articulating. A1 (fig. 2): 12 articulating segments with 1: 6s + 2a; 2: 2s; 3: 2s; 4: 2s; 5: 2s; 6: 2s; 7: 2s; 8: 2s; 9: 2s; 10: 4s; 11: 2s; 12: 5s + 1a. A2 (fig. 3): middle endopodal segment with 5 setae. Exopod 4-segmented; proximal segment with 4 medial setae. Md (fig. 4): proximal endopodal segment with 1 seta; distal segment with 6 setae. Mx1 (fig. 5): praecoxal endite with 3 posterior and 7 ventral setae, without an anterior seta; distal endite of basis with 2 setae; exopod with 3 lateral and 4 terminal setae; proximal endopodal segment with groups of 3 mid-ventral and 2 distoventral setae; distal endopodal segment with 4 setae. Mx2 (fig. 6): same as in CIV. Mxp (fig. 7): endopod indistinctly 4-segmented with 1 medial, 1 medial, 2 (1 medial, 1 lateral), 4 (1 medial, 2 terminal, 1 lateral) setae. P1-4 (figs. 8-11): swimming legs 1-3 with 2-segmented rami, swimming leg 4 with 1-segmented rami. Setal and spine formula as in table III. P5 (fig. 12): bilobed bud; each lobe with 2 short, distal attenuations. CII. Differs from CIII as follows: Body length range mm; ratio of length of prosome to length of urosome 2.7 :1 (based on 5 specimens). Prosome (fig. 1): 5 parts; 1 st a complex of 5 cephalic somites plus Th1; Th2, Th 3, Th 4, and Th5 articulating. Urosome (fig. 1): 2 parts; Th6 and Abd1 articulating. A1 (fig. 2): 8 articulating segments with 1: 4s + 2a; 2: 1s; 3: 1s; 4: 1s; 5: 3s; 6: 3s; 7: 2s; 8: 5s + 1a. A2 (fig. 3): middle endopodal segment with 4 setae. Proximal exopodal segment with 3 medial setae. Md (fig. 4): distal endopodal segment with 5 setae. TABLE III Spines and setae on swimming legs 1-4 of Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, CIII Coxa Basis Exopod Endopod 2 nd 3 rd 1 st 2 nd 3 rd 1 st Leg I-0 I-1, III-I-4 0-1, Leg I-0 I-1, III-I-5 0-1, Leg I-0 I-0, II-I-4 0-1, Leg III-I

21 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 169 Mx1 (fig. 5): praecoxal endite with 2 posterior setae. Proximal endopodal segment with groups of 1 mid-ventral and 2 distoventral setae; distal segment with 4 setae. Mx2 (fig. 6): praecoxal endite of syncoxa with 3 setae; coxal endite with 2 setae. Mxp (fig. 7): distal endite of syncoxa with 2 setae, coxal endite with 1 seta. Endopod indistinctly 3-segmented with 1 medial, 2 (1 medial, 1 lateral), 4 (1 medial, 2 terminal, 1 lateral) setae. P1-3 (figs. 8-10): swimming legs 1 and 2 with 2-segmented rami, swimming leg 3 with 1-segmented rami. Spine and setal formula as in table IV. P4 (fig. 11): bilobed bud; presumptive exopod with 3 short, distal attenuations, presumptive endopod with 2 short, distal attenuations. P5: absent. CI. Differs from copepodid stage II as follows: Body length range mm; ratio of length of prosome to length of urosome 2.5 :1 (based on 5 specimens). Prosome (fig. 1): 4 articulating parts; 1 st a complex of 5 cephalic somites plus Th1; Th2, Th 3, and Th4 articulating. Urosome (fig. 1): 2 parts; Th5 and Abd1 articulating. Antenna 1 (fig. 2): 6 articulating segments with 1: 4s + 1a; 2: 1s; 3: 2s; 4: 3s; 5: 2s; 6: 5s + 1a. Antenna 2 (fig. 3): middle endopodal segment with 4 setae. Proximal exopodal segment with 2 medial setae. Mandible (fig. 4): same as in CII. Mx1 (fig. 5): praecoxal endite with 2 posterior and 6 apical setae; proximal endopodal segment with 1 mid-ventral and 1 distoventral setae; distal segment with 3 setae. Mx2 (fig. 6): same as in CII. TABLE IV Spines and setae on swimming legs 1-3 of Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, CII Coxa Basis Exopod Endopod 2 nd 3 rd 1 st 2 nd 3 rd 1 st Leg I-0 I-0, III-I-4 0-1, Leg I-0 I-0, II-I-4 0-1, Leg III-I

22 170 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA TABLE V Spines and setae on swimming legs 1-2 of Pseudocyclops schminkei Chullasorn, Ferrari & Dahms, CI Coxa Basis Exopod Endopod 2 nd 3 rd 1 st 2 nd 3 rd 1 st Leg I-0 IV-I Leg I-0 III-I Mxp (fig. 7): proximal praecoxal endite of syncoxa unarmed, distal praecoxal endite with 1 seta. Endopod indistinctly 2-segmented, with 4 (1 medial, 2 terminal, 1 lateral) setae. P1-2 (figs. 8-9): with 1-segmented rami. Spine and setal formula as in table V. P3 (fig. 10): a bilobed bud; presumptive exopod with 3 short, distal attenuations, presumptive endopod with 2 short, distal attenuations. P4: absent. CR (fig. 1): inner terminal seta longest. REMARKS AND DISCUSSION There are five immature copepodid stages of Pseudocyclops schminkei separated by four molts. A fifth molt results in the terminal adult stage. One somite is added to the body at each molt including the molt to the adult CVI. Swimming legs 3 and 4, and leg 5 initially appear as a bud during the first three molts, and one stage later than the initial appearance of the somite upon which the limb originates. These limb buds bear distal attenuations [cf. spiniform outgrowths], rather than setae as they do for most copepods (Ferrari, 2000). The number of distal attenuations on swimming legs 3 and 4 corresponds to the maximum number of setae on the presumptive exopod (3 setae) and presumptive endopod (2 setae) of these limb buds. The transformed limb of swimming legs 1-4 bears the maximum number of setae reported for these limbs among copepods (Ferrari, 2000): 8 exopodal and 7 endopodal for swimming leg 1; 7 exopodal and 6 endopodal for swimming legs 2-4. The addition of arthrodial membranes to the rami follows the common pattern of development (Ferrari, 1988); the adult configuration of the rami of swimming legs 1-4 is reached at CV. CI of P. schminkei expresses the phylotypic architecture of podoplean and gymnoplean copepods: cephalon with five appendages; five thoracic somites,

23 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 171 the first united with the cephalon, the fifth without a limb; limbs of thoracic somites 1-3, viz., maxilliped and swimming legs 1-2, as transformed limbs; rami of swimming legs 1-2 an unarticulated segment complex; leg 3 as a limb bud; posterior abdominal somite with caudal ramus. At this stage, the body is divided between a broader prosome and narrower urosome although these are not homologous to the prosome and urosome of adults. Instead, the adult prosome is attained at CIII, as it is for other gymnoplean copepods (Ferrari & Dahms, 2007). In addition to fusion of all cephalic somites with the first thoracic somite at CI, and the fifth and sixth thoracic somites at CII in both sexes, the seventh thoracic somite is fused to the anterior abdominal somite of females at CVI so that the number of somites, as defined by arthrodial membranes, appears unchanged during the molt from CV to CVI. The adult prosome is complete at copepodid III. Thoracic somites 5 and 6, bearing swimming legs 4 and 5, begin development as narrow somites on the urosome of copepodids I and II but are transformed into broad somites of the eventual adult prosome during the molts to copepodids II and III, respectively. Sexual dimorphism is evident at CIV in segmentation and armature of leg 5. Patterning of antenna 1 is unclear from observations presented here. However, the following are inferred: the proximal segment of CII has 6 setae in three groups (1s + 1a, 2s, 1s + 1a); at CIII there are 8 setae in three groups (2s + 1a, 2s, 2s + 1a), and at CIV there are 10 setae in three groups (3s + 1a, 2s, 3s + 1a). At CV the proximal segment has 14 setae in four groups (3s + 1a, 2s, 3s + 1a, 3s + 1). Segment 12 of CIV with 6 setae will be subdivided by 2 arthrodial membranes to become segments of CV, each with 2 setae. Patterning the maxilliped is clearer. The number of endopodal segments of the maxilliped of P. schminkei increases from 2 at CI to 5 at CIV, as is the case for most calanoids (Ferrari & Dahms, 1998). However, the addition of setae is terminated at CIV rather than continuing through CVI, as for other basal calanoids like representatives of the family Ridgewayiidae (cf. Ferrari, 1995). Antenna 2 of most copepods is patterned during the naupliar phase of development and the molt to CI (Ferrari & Dahms, 2007). Patterning may include an increase in the number of arthrodial membranes and/or setae during the naupliar phase, and an increase or decrease in these numbers during the molt to CI. Antenna 2 is not known to be patterned during the copepodid phase of development, even for presumed basal calanoids like ridgwayiids (Ferrari, 1995). In contrast to other copepods, the antenna 2 of P. schminkei and P. umbraticus Giesbrecht, 1893 is patterned during copepodid

24 172 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA development (here, and see Costanzo et al., 2004). In the case of P. schminkei, patterning includes the addition of one arthrodial membrane and three setae; P. umbraticus adds five arthrodial membranes but no setae during its copepodid phase, as well as one arthrodial membrane and four setae during its naupliar phase (Costanzo et al., 2004). The basis of the copepodid maxilliped of P. schminkei includes two endites. The small, distal endite is armed with 1 seta at CI and adds a second seta at CII, a pattern shared with other calanoids (Ferrari & Dahms, 1998). The large, proximal endite is armed with 2 setae at CI and adds a third seta at CIII. No other calanoid, including species of the Platycopioida, has a well-developed proximal endite although many have the three corresponding setae, and these originate directly on the basis (Ferrari & Ivanenko, 2008). Both proximal and distal endites also are found on the maxilliped of the mystacocaridan Derocheilocaris typicus Pennak & Zinn, 1943 (see Hessler & Sanders, 1966); the proximal endite has four setae and the distal two setae (pers. obs., FDF) on this close relative of the copepods. Many basal podopleans also possess a well-developed endite on the basis, e.g., Longipedia americana Wells, 1980 [Polyarthra] (see Ferrari & Dahms, 1998; Dahms, 2004a, b), Speleophria scottodicarloi Boxshall & Iliffe, 1980 [Misophrioida] (see Huys & Boxshall, 1991), and Cyclopina caroli Lotufo, 1994 [Cyclopoida] (see Ferrari & Ivanenko, 2001). This endite corresponds to the proximal endite of calanoids and mystacocaridans because three setae have been found on basal Podoplea like Speleophria scottodicarloi, while the distal endite of the Calanoida and the Mystacocarida never bears more than 2 setae. Copepods usually bear apical setae on the presumptive exopod and endopod of the bud of swimming legs 1-4; these are the crown setae of the rami (Ferrari, 2000). No setae are present on the bud of swimming legs 3 and 4 of P. schminkei. Instead, there are distal attenuations in number corresponding to the setae of many calanoids. The buds of swimming legs 1 and 2 are present on the last nauplius of an unidentified species of Pseudocyclops from the Shedd Aquarium, and the bud of these limbs also has attenuations rather than setae (pers. obs., FDF). The situation is not clear for P. umbraticus although the bud of swimming leg 4 is illustrated with attenuations (Costanzo et al., 2004). The number of attenuations on these buds corresponds to the maximum number of setae found on the buds of other calanoids (Ferrari, 2000), and although the crown setae are absent from the limb buds of P. schminkei, the transformed limbs also bear the maximum number of setae reported among copepods (Ferrari, 2000). Some of these setae on swimming leg 1 will be allocated to

25 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 173 the proximal and middle segment, and distal complex of both rami; setae on swimming legs 2-4 will be allocated only to the proximal segment and distal complex of both rami. Swimming leg 1 of all copepodid stages of P. schminkei lacks both a modified distal seta on its basis that is curved or recurved over the endopod, and a modified proximal endopodal segment that includes denticles or pores (Ferrari & Dahms, 2007). These modifications make up Von Vaupel Klein s Organ (VVKO), which is present on most calanoids and which has been proposed as a synapomorphy for Calanoida (cf. Ferrari & Dahms, 2007). The modified distal seta is derived from a seta that is simple, short and immediately adjacent to the unmodified endopod, as it is found in many podopleans. VVKO has not been reported on any species of Pseudocylops. However,a simple medial seta has been reported on the basis of swimming leg 1 of P. kulai Othman & Greenwood, 1989, P. lepidotus Barr & Ohtsuka, 1989, P. ornaticauda Ohtsuka, Fosshagen & Putchakarn, 1999, and P. ensiger Ohtsuka, Fosshagen & Putchakarn, VVKO is considered secondarily lost if the distal seta is present but originates secondarily on the medial face of the basis, as it does on the four species of Pseudocyclops listed above, as well as Nanocopia minuta Fosshagen, 1988, a Platycopioida, Placocalanus inermis Ohtsuka, Fosshagen & Soh, 1996, a ridgewayiid, or the seta is associated with a modification of the basis, like the anterior pore of the Lucicutiidae, or if both distal seta and modifications of the proximal endopodal segment are absent, e.g., Antrisocopia prehensilis Fosshagen, 1985 and many other species of Pseudocylops. The endopod of swimming leg 5 of males does not articulate with the basis at CIV and CV of P. schminkei and P. umbraticus. This unusual configuration is shared with basal podopleans although among the basal podopleans the configuration is retained at CVI, e.g., like both sexes of the polyarthran Longipedia americana (see Onbé, 1984), males of Benthomisophria palliata Sars, 1909 (see Huys & Boxshall, 1991), and many harpacticoid copepods (Seifried, 2003). Consideration of some of the above characters suggests that Pseudocyclopidae is the oldest extant calanoid family. Pseudocyclopidae is a monophyletic lineage that currently can be diagnosed by two apomorphies of its species: exopod of antenna 2 patterned during the copepodid phase of development; buds of swimming legs 1-4 without setae. Species of Pseudocyclopidae share an unarticulated endopod on leg 5 at CIV and CV with a more inclusive lineage that includes basal podopleans, and a well-developed proximal endite

26 174 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA on the basis of the maxilliped, with a more inclusive lineage that includes basal Podoplea and Mystacocarida. The states of these characters are derived in all other calanoids. Among the remaining basal calanoid families, species of Platycopioida, Epacteriscidae, and Boholinidae share: a basis of the maxilliped without the proximal endite; an endopod of male leg 5 which articulates with the basis at CIV and CV. Thus, Pseudocyclopidae is the oldest extant calanoid family. This hypothesis does not support the conclusion of Andronov (2007) that all species belonging to the superfamilies Pseudocyclopoidea and Epacteriscoidea should be placed in the family Pseudocyclopidae. Nor does it support the opinion of Boxshall & Halsey (2004) that species belonging to Pseudocyclopidae and Boholinidae comprise a superfamily Pseudocyclopoidea. ACKNOWLEDGEMENTS Mr. Yoji Ichimura and Mr. Hirofumi Kurosaki of Kerama Pearl Ltd., and Dr. Shuichi Sakamoto of Oriental Yeast Co., Ltd. collected the specimens of Pseudocyclops schminkei in January 2007; these were made available to us by Dr. Nozomu Iwasaki of Kochi University. Dr. Nozomu Iwasaki collected specimens in May Mark Schick of the Shedd Aquarium in Chicago donated unidentified specimens of Pseudocyclops sp. from an aquarium there. Thanks are due to Dr. Chang-tai Shih (National Taiwan Ocean University, Keelung) for helpful advice on the literature. Dr. Elena L. Markhaseva (Zoological Institute, Russian Academy of Science, St. Petersburg) translated parts of Andronov (2007). REFERENCES ANDRONOV, V. N., Novye rod i vid veslonogikh rakov (Crustacea, Calanoida) iz tsentral no-vostochnoi atlantiki i problemy makrotaksonomii nadsemeistv Pseudocyclopoidea i Epacteriscoidea. [New genus and species of copepods (Crustacea, Calanoida) from the central-eastern Atlantic and problems of classification of the superfamilies Pseudocyclopoidea and Epacteriscoidea]. Zoologicheskii Zhurnal, 86: [In Russian, with English abstract.] BOXSHALL, G.A.&S.H.HALSEY, An introduction to copepod diversity, 1-2: (The Ray Society, London). CHULLASORN, S.,F.D.FERRARI &H.-U.DAHMS, Pseudocyclops schminkei (Copepoda, Calanoida, Pseudocyclopidae): a new species from Okinawa. Helgoland Marine Research, 64: CLAUS, C., Die frei lebenden Copepoden mit besonderer Berücksichtigung der Fauna Deutschlands, der Nordsee und des Mittelmeeres: 1-230, pls (Verlag von Wilhelm Engelmann, Leipzig).

27 Ferrari et al., COPEPODIDS OF PSEUDOCYCLOPS SCHMINKEI 175 COSTANZO, G., N. CRESCENTI & G. ZAGAMI, Postembryonic development of Pseudocyclops umbraticus Giesbrecht, 1893 (Copepoda, Calanoida) from coastal waters of Sicily. Crustaceana, 77: DAHMS, H.-U., Copepodid development in Harpacticoida (Crustacea, Copepoda). Microfauna Marina, 8: , Phylogenetic implications of the crustacean nauplius. In: V. ALEKSEEV, G. A. WYNGAARD & F. D. FERRARI (eds.), Advances in copepod taxonomy A tribute to Ulrich Einsle. Hydrobiologia, 417 (Spec. Iss.): , 2004a. Postembryonic apomorphies proving the monophyletic status of the Copepoda. Zoological Studies, 43: , 2004b. Exclusion of the Polyarthra from Harpacticoida and its reallocation as an underived branch of the Copepoda (Arthropoda, Crustacea). Invertebrate Zoology, 1 (1): FERRARI, F. D., Developmental patterns in numbers of ramal segments of copepod postmaxillipedal legs. Crustaceana, 54: , Six copepodid stages of Ridgewayia klausruetzleri, a new species of calanoid copepod (Ridgewayiidae) from the barrier reef in Belize, with comments on appendage development. Proceedings of the Biological Society of Washington, 108: , Patterns of setal numbers conserved during early development of swimming legs of copepods (Crustacea). In: V. ALEKSEEV, G. A. WYNGAARD & F. D. FERRARI (eds.), Advances in copepod taxonomy A tribute to Ulrich Einsle. Hydrobiologia, 417 (Spec. Iss.): , Review of: The Copepodologist s Cabinet: A Biographical and Bibliographical History, Volume One, Aristotle to Alexander von Nordmann (330 B.C. to A.D. 1832) by David M. Damkaer. Journal of Crustacean Biology, 23: FERRARI, F. D.& H.-U. DAHMS, Segmental homologies of the maxilliped of some copepods as inferred by comparing setal numbers during copepodid development. Journal of Crustacean Biology, 18: &, Post-embryonic development of the Copepoda. Crustaceana Monographs, 8: i-vi, FERRARI, F. D.& V. N. IVANENKO, Interpreting segment homologies of the maxilliped of cyclopoid copepods by comparing stage-specific changes during development. Organisms, Diversity and Evolution, 1: &, Identity of protopodal segments and the ramus of maxilla 2 of copepods (Copepoda). Crustaceana, 81: GIESBRECHT, W., Crustacea. In: A. LANG (ed.), Handbuch der Morphologie der wirbellosen Tiere, 4, Arthropoda: 9-252, figs HESSLER, R. R.& H. L. SANDERS, Derocheilocaris typicus revisited. Crustaceana, 11: HULSEMANN, K., Tracing homologies in appendages during ontogenetic development of calanoid copepods. Bulletin of Plankton Society of Japan, (Special Volume): HUYS, R. & G. A. BOXSHALL, Copepod evolution: (The Ray Society, London). ILLG, P. L., A review of the copepod genus Paranthessius Claus. Proceedings of the United States National Museum, 99 (3245): LANG, K., Marine Harpacticiden von der Campbell-Insel und einigen anderen südlichen Inseln. Kungliga Fysiografiska Saellskapets i Lund Handlingar, (n. F.) 45: ONBÉ, T., The developmental stages of Longipedia americana (Copepoda: Harpacticoida) reared in the laboratory. Journal of Crustacean Biology, 4:

28 176 CRM 016 Defaye et al. (eds.), STUDIES ON FRESHWATER COPEPODA SEIFRIED, S., Phylogeny of Harpacticoida (Copepoda): Revision of Maxillipedasphalea and Exanechentera: (Cuvillier Verlag, Göttingen). YAGER, J., Remipedia, a new class of Crustacea from a marine cave in the Bahamas. Journal of Crustacean Biology, 1: First received 30 December Final version accepted 9 April 2010.