Botachus cylindratus Thorell, 1859

(Figs. 101, 102)

Material examined. 9 ♀♀, 4 ♂♂ (MNHN-IU-2018- 1823) from Ascidia mentula M̹ller, 1776, Brest, France; 5 ♀♀ A. mentula (MNHN-IU-2018-1824), Brest; 20 ♀♀, 1 ♂ (MNHN-IU-2018-1825) from A. mentula, Porto Vecchio, Corsica; 2 ♀♀, 3 ♂♂ (MNHN-IU-2018-1826) from A. mentula, Glénan, France; 1 ♀, 2 ♂♂ (MNHN-IU-2018-1827) from A. mentula, Adriatic; 4 ♀♀ (MNHN-IU-2018-1828) from A. mentula, Kristineberg, Sweden; 1 ♀ (MNHN-IU-2018-1829) from A. mentula, Bergen; 2 ♀♀, 1 ♂ (MNHN-IU-2018-1830) from A. mentula, Canaries; 8 ♀♀ (MNHN-IU-2018-1918) from A. mentula, Le Havre, Port Antifer, Breton coll., November 2008; 9 ♀♀, 2 ♂♂ (MNHN-IU-2017-2161) and dissected 1 ♀, 1 ♂from A. mentula, Corsica, MEDITS 2016 Stn M16-3 (41°50.74 Ń 09° 27.53 É), depth 72 m; 11 ♀♀, 2 ♂♂ (MNHN-IU-2017-2164) from A. mentula, Corsica (42°10.70 Ń 09°36.22 É), MEDITS 2016 Stn M16-1.

1 ♀ (MNHN-IU-2018-1831) and 1 dissected ♀ from A. muricata Heller, 1874, Porto Vecchio, Corsica, depth 3 m.

3 ♀♀ (MNHN-IU-2018-1832) from Phallusia fumigata (Grube, 1864), Porto Vecchio, Corsica.

Supplementary description of female associated with Ascidia mentula from Corsica:

Body (Fig. 101A) slender, depressed, 1.51 mmlong. Prosome gradually broadening distally. Fourth pedigerous somite forming brood pouch, longer than anterior part of prosome; fifth pedigerous somite completely fused with fourth. Freeurosome cylindrical, 5-segmented, directed ventrally. Anal somite with spinulose, highly sclerotized ventrodistal protuberance. Caudalramus (Fig. 101B) about 2.4 timeslongerthan wide (59×25 μm), extended posteroventrally, armed with 2 claws and 4 naked setae and ornamented with several rows of minute spinules; 2 claws subequal in length and thickness, thicker claw 46 μm long and thin claw 43 μm long; posteroventral naked seta wrinkled, smallest seta inserted into basal part of thick claw.

Rostrum longerthan wide, narrowing distally towards rounded apical margin. Antennule, antenna, and mouthparts as described and illustrated by Illg & Dudley (1965).

Leg 1 (Fig. 101C) with 3-segmented exopod and 2- segmented endopod; compound distal endopodal segment subdividedbyindistinct suture line. Innercoxalsetaabsent inlegs 1–4. Legs 2–4 (Fig. 101 D–F) with 3-segmented rami; first and second exopodal segments lacking inner seta; first and second endopodal segments also lacking inner setae; setae stiff, with short setules distally. Leg 4 lacking outer seta on basis. Armature formula for legs 1–4 as follows:

Leg 5 (Fig. 101G) small, consistingof digitiform protopod and rectangular free exopod; protopod tipped with long, naked seta; exopodal segment about 2.2 times longer than wide, also tipped with 1 naked seta (shorter than protopodal seta) and ornamented with spinules on inner margin.

Supplementary description of female associated with A. mentula from Le Havre (Atlantic).

Morphological features as in above female from Corsica in the Mediterranean, except for leg armature and segmentation of leg 1 endopod, as follows:

Supplementary description of female associated with Ascidia muricata from Corsica.

Morphological features as in female associated with A. mentula from Corsica, except for leg armature and segmentation, as follows:

Supplementary description of male associated with A. mentula from Corsica.

Body(Fig.102A) slender, 0.85mmlong.Prosomestrongly depressed. Urosome 6-segmented; fifth pedigerous somite free. First abdominal somite ornamented with 10 small tubercles on ventral surface (Fig. 102B).Anal somite (Fig. 102C, D) short, without ventral protuberance. Caudal ramus (Fig. 102C, D) about 2.1 times longer than wide (34×16 μm), bearing tapering posteroventral process; armed with 2 claws and 4 setae; 2 claws almost equal in length, 40 and 39 μm, but unequal in thickness; setae naked, smallest seta inserted into basal part of thicker claw.

Rostrum, antennule, antenna, and mouthparts as in female.

Leg 1 (Fig. 102E) basis bearing inner distal seta and small, naked outer seta: endopod 3-segmented, but articulation indistinct between second and third segments. Leg 2 (Fig. 102F) exopod and endopod each bearing inner seta on first segment; third endopodal segment with 2 spines and 3 setae. Leg 3 (Fig. 102G) exopod with inner seta on second segment; endopod armed as in leg 2. Leg 4 (Fig. 102H) lacking outer seta on basis, as in female; exopod as in leg 3; endopod with inner seta on first segment and 1 spine and 3 setae on third segment. Armature formula for legs 1–4 as follows:

Leg 5 (Fig. 102B) protopod short, notarticulated from ventral surface of somite, with naked seta on tip of short outer distal process; exopod rectangular, 10×6 μm, with rows of fine spinules distally; armed with 2 setae of equal length, inner seta feebly pinnate, outer seta naked. Leg 6 (Fig. 102B) represented by 3 naked distal setaeon genital operculum, middle seta longest, inner shortest.

Remarks. As described above and by Illg & Dudley (1965), B. cylindratus exhibits extreme variability in the segmentation and setation of the biramous swimming legs (see Table 1). The nature of this variability requires further morphological study and analysis of a sufficient number of samples from different hosts and localities in order to determine whether there is any discernible pattern related to either host usage or geographical distribution.