Botachus Thorell, 1859

Kim, Il-Hoi & Boxshall, Geoff A., 2020, Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata), Megataxa 4 (1), pp. 1-6 : 154-155

Genus Botachus Thorell, 1859

Diagnosis: Body consisting of cephalosome and first to fourth pedigerous somites, with fourth somite completely fused to fifth and forming elongate brood pouch, as long as anterior part of prosome, plus 5-segmented free urosome. Anal somite with paired posteroventral protuberances densely ornamented with minute spinules. Caudal rami armed with 2 claws and 4 setae. Antennule 7- or 8-segmented. Antenna 4-segmented; basiswith large pinnate seta and smallseta (representing exopod); compound distal endopodal segment armed with 9 setae plus terminal claw. Mandible with 4 teeth and 1 proximal setaon coxal gnathobase; basis with 1 seta; exopod 2- segmented and armed with 3 and 2 setae on first and second segments, respectively; endopod unsegmented, armedwith 12 setae. Maxillulewith 8 setaeon arthrite, 1 setaon coxal endite, 2 setae on epipodite, 3 unequal setae on medial margin of basis; exopod with 4 distal setae; endopod smaller than exopod, with 3 distal setae. Maxilla 5-segmented; syncoxawith 3, 1, 2, and 3 setae on first to fourth endites, respectively; basis with 3 setae; first to third endopodal segments with 1, 1, and 4 setae, respectively. Maxilliped lobate with 10 setae (8 medial and 2 apical). Legs 1–4 with 3-segmented exopods and 2- or 3-segmented endopods. Inner coxal seta lacking in legs 1–4. Inner distal spine present on basis of leg 1. Armature formula variable:

Leg 5 consisting of digitiform protopod and free exopodal segment bearing 2 setae.

Type Species: Botachus cylindratus Thorell, 1859 , by original monotypy.

Remarks. This genus is treated as effectively monotypic. Two species described and named by Hesse (1869), B. fulvus Hesse, 1869 and B. macroone Hesse, 1869 , were regarded as indeterminable by Illg (1958) and are not considered here. Stock (1967) proposed to recognize Goniodelphys Buchholz, 1869 as a junior synonym of Botachus and transferred its type species, Goniodelphys trigona Buchholz, 1869 , and he also included Notopterophoroides malacodermatus Schellenberg, 1922 in Botachus . However, this proposal was rejected by Ooishi & Illg (1973) because it would result in an expanded generic concept for Botachus that would be “meaningless taxonomically”. Ooishi & Illg (1973) continued to recognize Goniodelphys as valid and to consider N. malacodermatus as a species of Notopterophoroides .

The most important differences between Botachus and related genera such as Goniodelphys seem to be the possession of 4 setae on the exopod and 3 setae on the endopod of the maxillule. The absence of the inner spine on the basis of leg 1 in B. cylindratus was regarded as a significant difference between Botachus and Goniodelphys , but this spine is present in the male and in the new species described below. The genera related to Botachus can be distinguished using the following key.

Key to genera of “ Botachus group”

1. Maxillule with 4 setae on exopod and 3 setae on endopod. ............................................................................. Botachus Maxillule with 3 setae on exopod and 4 setae on endopod .......................................................................................... 2

2. First outer element of third exopodal segment of leg 1 is a seta.................................................................................... 3 First outer element of third exopodal segment of leg 1 is a spine.................................................................................. 4

3. Caudal ramus with 3 spines and 3 setae; mandibular exopod with 4 setae ......................................... Notopterophoroides Caudal ramus with 6 setae; mandibular exopod with 4 setae .................................................. Ooishillgia gen. nov.

4. Maxillule as simple lobe........................................ Microra Maxillule segmented and biramous.................................. 5

5. First endopodal segment of mandible armed with 2 setae; legs 1–4 usually with 2-segmented endopod.... Periproctia Firstendopodal segment of mandible armed with 4 or 5 setae; legs 1–4 with 3-segmented endopod ........................ ...................................................................... Goniodelphys