Chone megalova, Gotto & Leahy, 1988

Boxshall, Geoff A., O’Reilly, Myles, Sikorski, Andrey & Summerfield, Rebecca, 2019, Mesoparasitic copepods (Copepoda: Cyclopoida) associated with polychaete worms in European seas, Zootaxa 4579 (1), pp. 1-69 : 31-32

Cyclorhiza megalova Gotto & Leahy, 1988

Norwegian material examined: 49♀♀ from 34 specimens of Eteone cf. longa / flava, 4909 Helgeland, Havbruk, Stn 1 (69.9202°N, 12.24907°E), depth 115 m, 12 November 2007; collected by A. Sikorski. 3♀♀ from 2 specimens

of Eteone cf. longa / flava, Sandnessjøen, Stn LÅ1 (66.2301°N, 12.32355°E), depth 48 m, 0 3 January 2007; collected by A. Sikorski. 1♀ from Eteone cf. longa , 5769 Brattholmen, Stn S2-B (65.9106°N, 12.22213°E), depth 115 m, 18 January 2001; collected by A. Sikorski. 1♀ from Eteone cf. longa / flava, 5161 Korsfjord, Stn D5 (70.2347°N, 23.35317°E), depth 131 m, 27 September 2010; collected by A. Sikorski. 1♀ from Eteone cf. longa / flava, Huldra, Stn 6-1 (60.853°N, 02.640619°E), depth 123 m; 0 5 June 1999; collected by A. Sikorski. 1♀ from Eteone cf. longa / flava, Huldra, Stn 13-1 (60.8572°N, 02.646196°E), depth 123 m; 0 5 June 1999; collected by A. Sikorski. 6♀♀ Eteone cf. longa / flava, 7734 Bjørnsvik 2015, Stn 3B (67.53188°N, 15.38787°E), depth 247 m, 0 3 June 2015; collected by A. Sikorski. 1♀ Eteone cf. longa / flava, 7734 Bjørnsvik 2015, Stn 2B (67.5325°N, 15.38732°E), depth 211 m, 0 3 June 2015; collected by A. Sikorski. 1♀ Eteone cf. longa / flava, 8190 Hammer ASC, Stn C5-2 (67.96118°N, 15.16742°E), depth 68 m, 31 March 2016; collected by A. Sikorski. NHMUK Reg. Nos 2016.527-536 .

British material examined: 1 mature ♀ from E. longa , Shetland Mainland, Vidlin Voe, Stn 50B, depth unknown, 25 April 2000; collected by P. R. Garwood. 2 mature ♀♀, 5 immature ♀♀ from 4 specimens of Eteone longa (Fabricius, 1780) , North Sea , Dockhead A; depth unknown, 2006 ; collected by P. R. Garwood. 1 mature ♀ from E. longa , ( Unico. 43242), Survey MARCOD08, Codling Bank, Stn 16a, 18 September 2008 , collected David Hall. 1 ovigerous ♀ from E. longa, Irish Sea , Cork , depth unknown, 26 October 2011 ; collected by P. R. Garwood. 4 ovigerous ♀♀, 1 mature ♀, from 4 specimens of E. longa, Cairn Ryan, Loch Ryan , 13 March 2012, collected by David Hall. 1 ovigerous ♀, 3 mature ♀♀, 2 immature ♀♀ from 5 specimens of E. longa, Loch Ryan , SEPA Stn West of Drummuckloch , Cairn Ryan (54° 57.216’N, 05° 01.299’W), depth 10 m, 11 July 2013 ; collected by Jeni Boyle. 3 mature ♀, 3 juvenile ♀ from single E. longa , Orkney, Veantrow , SEPA Stn 200mS (59° 04.401’N, 02° 52.178’W), depth 10 m, 14 June 2016 . 2 mature ♀♀ on E. longa , Shetland, Hascosay Sound , Bow of Hascosay Fish Farm , SEPA Stn 100mN (60° 36.80’N, 01° 00.34’W), depth 11 m, found by Jeni Boyle, 0 3 June 2017 . 1 ovigerous ♀ on E. longa , Shetland Mainland , Setterness West Fish Farm , SEPA Stn 100mNW (60° 25.26’N, 01° 00.09’W), depth 55 m, found by Jeni Boyle, 13 June 2017 . NHMUK Reg. Nos 2018.143-152 .

Differential diagnosis. Adult female body comprising elongate ectosoma connected to endosoma via short stalk. Ectosoma of mature female with mean length 1.22 mm, range 0.84 mm to 1.65 mm (based on 12 ovigerous specimens), and mean maximum width of 0.31 mm, range 0.23 to 0.40 mm. Ectosoma variable in shape, typically tapering posteriorly ( Fig. 13A, B ), but blunt ended in developing females ( Fig. 13D ) and in adult females prior to oviposition ( Fig. 13C ). Ectosoma bearing antennules, antennae and maxillipeds ( Figs. 13 G-I) typical for genus; lacking any vestige of trunk limbs and caudal rami. Anus lacking. Genital apertures paired, located anteriorly on underside of ectosoma ( Fig. 13F ). Egg sacs elongate, up to 4.83 mm long (in female of body length 1.38 mm), egg arrangement typically multiseriate with 2 or 3 irregular longitudinal rows visible in any view ( Fig. 13B ). Eggs ovoid: mean dimensions 122 µm (long axis) by 93 µm (short axis). Stalk short and broad, connecting to endosoma within host. Endosoma comprising two elongate rootlets, penetrating body cavity of host.

Remarks. We agree with the interpretation of Gotto & Leahy (1988) that the form of the endosoma described for this species by Heegaard (1942) was inaccurate due to damage. The endosoma comprises two elongate rootlets. More than 20 ovigerous females were examined and all but one possessed multiseriate egg sacs up to 4.83 mm in length, although the egg sacs were often broken. The single exception was a female of ectosoma length 0.96 mm which carried an egg sac in the form of an axial filament with eggs attached along its length ( Fig. 13A ), described as a “bunch of grapes” by Gotto & Leahy (1988). A similar form of egg sacs was illustrated for Phyllodicola petiti by Delamare Deboutteville & Laubier (1960). These eggs were ovoid and of the same dimensions as those measured in multiseriate sacs (i.e. about 122 by 93 µm). The average of these measurements (108 µm) corresponds closely to the single dimension for egg size (110 µm) given by Gotto & Leahy (1988) and this character was used by Gotto (1993) to distinguish between the two congeners, since the eggs are markedly smaller in C. eteonicola (92 µm). In addition, the multiseriate egg sacs of C. megalova typically display 2 or 3 longitudinal rows of eggs within the sac ( Fig. 13B ), whereas in C. eteonicola the egg sacs display about 5 longitudinal rows ( Fig. 12 ). There were no significant differences in limb structure between C. megalova and C. eteonicola .

Some of the hosts are reported here as Eteone cf. longa /flava as the polychaete material from Norwegian waters was not assigned to species level. The depth range of this parasite in Norwegian waters is 48 to 247 m. O’Reilly (2000) recorded C. megalova on E. longa caught in Orkney, Loch Craignish (Argyll) and the Firth of Clyde in Scotland, and from the same host in the Irish Sea.

Figures

FIGURE 12. Cyclorhiza eteonicola Heegaard, 1942. Micro-CT rendering of ovigerous female attached to host, Eteone spetsbergensis. Scale bar: 2 mm.

FIGURE 13. Cyclorhiza megalova Gotto & Leahy, 1988, female. A, spent adult female with single egg string attached, ventral view showing egg string comprising central axis and large developing eggs plus empty egg membranes (arrowed); B, adult female showing length of intact egg sac relative to ectosoma length; C, adult female with ectosoma full of developing eggs; D, developing ectosoma; E, early stage female, lateral view showing paired limbs, genital apertures and finely striated dorsal surface integument; F, detail of developing female anterior end, showing spinules (arrowed) located lateral and medial to genital aperture; G, antennule; H, antenna; I, maxilliped. Scale bars A, C–D, 200 µm, B, 1 mm, E, 50 µm, F, 100 µm, G–I, 25 µm.