Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata) Author Kim, Il-Hoi 0000-0002-7332-0043 Korea Institute of Coastal Ecology, Inc., 802 - ho, 302 - dong, 397 Seokcheon-ro, Ojeong-gu, Bucheon, Gyeonggi-do 14449, Republic of Korea ® ihkim @ gwnu. ac. kr; https: // orcid. org / 0000 - 0002 - 7332 - 0043 ihkim@gwnu.ac.kr Author Boxshall, Geoff A. 0000-0002-7332-0043 Korea Institute of Coastal Ecology, Inc., 802 - ho, 302 - dong, 397 Seokcheon-ro, Ojeong-gu, Bucheon, Gyeonggi-do 14449, Republic of Korea ® ihkim @ gwnu. ac. kr; https: // orcid. org / 0000 - 0002 - 7332 - 0043 ihkim@gwnu.ac.kr text Megataxa 2020 2020-12-24 4 1 1 6 http://zoobank.org/3fdd970e-62f1-4f67-8cce-10870bdb3c01 journal article 54097 10.11646/megataxa.4.1.1 7c9bc39d-9910-46f1-9558-c0647b9cbbdb 2703-3090 4591138 Notodelphys reducta Illg & Dudley, 1961 ( Fig. 18 ) Material examined . 25 ♀♀ (MNHN-IU-2018-1769) from Molgula helleri Drasche, 1884 , Tarente (= Taranto, Italy ); 7 ♀♀ (MNHN-IU-2018-1770) and dissected 1 ♀ , 1 ♂from Molgula occulta Kupffer, 1875 , Montpellier, Mediterranean coast of France ; 2 ♀♀ (MNHN-IU-2018- 1771) and 1 dissected ♀ from Molgula appendiculata Heller, 1877 , Palombaggia, Corsica ; 1 ♀ (MNHN-IU- 2017-2170) from M . appendiculata , MEDITS 2015 Stn T 70, ( 42°08.5 Ń , 3°11.45 É ), depth 41 m . Diagnostic characters of female . Body ( Fig. 18A ) of dissected specimen 2.33 mm long. Caudal ramus ( Fig. 18B, C ) about 3.3 times longer than wide (144×44 μm) and about 1.3 timeslongerthan anal somite (112×139 μm) ( Fig 18B ), ornamented with setules on outer margin; outer lateral seta located at 62% of ramus length. Rostrum tapering, as long as wide, with weakly bilobed apex. Antennule 15-segmented, but articulation betweensecondand thirdsegments incomplete.Antennary exopod represented by 2 large pinnate setae of subequal lengths; compound distal endopodal segment about 4 timeslongerthan wide. Labrumwithprominent posterolateral protuberances; posteromedian lobe broad, setulose on both sides and with several spinules in middle. Mandibular endopod with 4 and 9 setae on first and second segments, respectively ( Fig. 18D ). Maxillule ( Fig. 18E ) with 10 setae on precoxal arthrite; endopod with trace of articulation, armed with total of 5 setae (2 distal seta longer and naked). Maxilla ( Fig. 18F ) 5-segmented; syncoxa with 3 setae and 1 minute setule on first endite; endopod with 1, 1, and 4 setae on first to third segments, respectively. Maxilliped 3-segmented and armed with 10, 1, and 3 setae on first to third segments, respectively. Exopods of legs 2–4 armed only with setae; setae on outer margins of exopods bluntly tipped. Leg 5 ( Fig. 18G ) protopod smooth, not defined from ventral surface of somite; outer protopodal process shorter than exopod; freeexopodalsegment quadrate 27×29 μm, with 2 unequal setae. Male . Body 1.73 mmlong. Urosome 6-segmented: anal somite with several wart-like tubercles distally on dorsal and ventral surfaces. Caudal ramus about 3.2 times longer than wide, setulose on outer margin, with several wart-like tubercles in distal third of ventral surface. Antennule 10-segmented, geniculate between eighth and ninth segments; terminal segment with blunt tip. Leg 6 represented by 2 setae and 1 inner subdistal setule on genital operculum. Remarks . Notodelphys reducta was first described by Illg & Dudley (1961) from the French Mediterranean coast. Subsequently, this copepod was reported also from Naples, Italy ( Illg & Dudley, 1965 ). In both cases the host was Molgula appendiculata (as Ctenicella appendiculata ) and N . reducta is the only known copepod associate of this ascidian. The ascidians M. helleri and M. occulta are reported here for the first time and constitute new host records for N. reducta . Illg & Dudley (1961) mentioned that this species differed from every known species of Notodelphys in the reduction of the protopod of leg 5. We infer that this description refers to the lack of a basal articulation between the protopod of leg 5 and the somite, as observed in our specimens, as well as the relatively small size of the outer protopodal process bearing the outer basal seta.