Botryllophilidae Sars, 1921

Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species, Zootaxa 1, pp. 1-286 : 45-48

Family Botryllophilidae Sars, 1921

Diagnosis. Female: Body inflated, unsegmented or obscurely segmented, consisting of anterior and posterior parts, without distinct prosome-urosome division. Anterior part of body consisting of cephalosome to fifth pedigerous somites, posterior part consisting of genital somite and abdomen. Abdomen basically 4-segmented but with pattern obscured by additional annulations in some species of Bçtryllçphẚlus and Schẚzçprçctus. Caudal ramus armed with 6 armature elements (some represented by claws), or occasionally some lost. Rostrum weak or absent. Antennule short, at most 5-segmented. Antenna uniramous, 2- to 4-segmented, consisting coxa, basis, and 1- or 2-segmented endopod, and armed with up to 8 setal elements (setae or spines); coxa and basis sometimes fused to form coxobasis. Mandible variable, consisting of coxa bearing well-developed gnathobase and setiferous palp in Bçtryllçphẚlus and Schẚzçprçctus, but palp absent or consisting of 1- or 2-segmented lobe tipped with 1 or 2 armature elements in other genera. Maxillule consisting of precoxa and palp in Bçtryllçphẚlus, Schẚzçprçctus and eaplçstçmẚdes, but absent or represented by small lobe in other genera. Maxilla primitively 3-segmented, armed with up to 10 setae in Bçtryllçphẚlus and Schẚzçprçctus, but absent or reduced to 1- or 2-segmented lobe bearing 1 or 2 setae in other genera. Maxilliped 4-segmented, consisting of syncoxa, basis, and 2-segmented endopod plus terminal claw; in eaplçstçmella endopodal segments and terminal claw usually fused to form subchela. Legs 1-4 biramous with 1- or 2-segmented rami; coxa lacking inner element; basis lacking inner distal element in leg 1. Legs 1-4 of Bçtryllçphẚlus usually showing left-right asymmetry. Leg 5 variable, present as digitiform process, lamellate, or represented by small lobe, bearing up to 4 setae. Leg 6 represented by 3 spiniform elements on genital operculum.

Male: Body cyclopiform with distinct prosome-urosome division. Urosome consisting of fifth pedigerous, genital and 4 abdominal somites. Caudal ramus armed with 6 setae. Antennule 4-segmented, with numerous aesthetascs on proximal segment (antennule of eaplçstçmella 8-segmented, with few aesthetascs on proximal segment). Antenna as in female. Mandible, maxillule and maxilla absent or vestigial. Maxilliped similar to that of female. Legs 1-4 biramous typically with 3-segmented rami, but leg 1 endopod 1- to 3-segmented, with modified setation and leg 4 endopod 2- or 3-segmented. Inner coxal seta present or absent. Basis of leg 1 with or without inner distal element. Leg 5 consisting of outer protopodal seta located laterally on surface of somite and free exopodal segment bearing 2 setae. Leg 6 represented by 2 setae on genital operculum.

Type genus. Schẚzçprçctus Aurivillius, 1885.

Other included genera. Bçtryllçphẚlus Hesse, 1864, eaplçstçmẚdes Chatton & Harant, 1924, eaplçstçma Chatton & Harant, 1924, eaplçsaccus Chatton & Harant, 1924, eaplçstçmella Chatton & Harant, 1924, and maulẚllgẚa Monniot C., 1982.

Remarks. In their revision of the family Ascidicolidae, Illg & Dudley (1980) treated the Botryllophilinae as a subfamily comprising two valid genera, Bçtryllçphẚlus and Schẚzçprçctus. They classified it as a nçmen cçnservandum and attributed it to Sars (1921). Illg & Dudley (1980) took this action because they recognised that the family name Schizoproctidae Aurivillius, 1885 has priority over the Botryllophilidae Sars, 1921 , but the name Schizoproctidae had not been used in the preceding 50 years, However, no formal case was made to the International Commission on Zoological Nomenclature. In continuing to use Botryllophilidae as a conserved name, Boxshall & Halsey (2004) followed Illg & Dudley (1980) in the interests of nomenclatural stability, and we continue this usage here.

Boxshall & Halsey (2004) pointed to a number of synapomorphies between Bçtryllçphẚlus and Schẚzçprçctus and the genera eaplçstçmẚdes, eaplçstçma, eaplçsaccus, and eaplçstçmella which were placed in the subfamily Haplostominae Chatton & Harant, 1924 by Illg & Dudley (1980). Monniot (1982) subsequently added another genus, maulẚllgẚa, to the Haplostominae . Boxshall & Halsey (2004) considered that the synapomorphies, especially those exhibited by the males, constituted strong evidence of a close relationship and they did not adopt the subfamilial division, instead they recognised all seven genera as members of a single family level taxon, for which they used the name Botryllophilidae .

Genus Botryllophilus Hesse, 1864

Diagnosis (female). Body usually asymmetrical, consisting of broader anterior part and narrower posterior part. Anterior part consisting of cephalosome and first to fifth pedigerous somites. Posterior part consisting of genital somite and abdomen; abdomen comprising 4 somites in some species, or 5 to 8 annulations in others. Caudal rami short, with 4 claws and 1 or 2 setae; claws curved outwards or ventrally. Rostrum present or absent. Antennule short and broad, 4- or 5-segmented. Antenna consisting of short coxa, basis, and 1- to 3-segmented endopod (endopod mostly 2-segmented), armed with 5 to 8 setae, usually asymmetrical between right and left antennae in form and length of setae. Labrum not specialized. Mandible consisting of coxa and palp; medial margin of coxal gnathobase bearing 3 or 4 teeth distally and spinulose proximal part; palp elongate, unsegmented, typically armed with 9 setae: 3 (exopodal setae) on outer proximal region, 2 in subdistal region, and 4 distally. Maxillule consisting of precoxa with 4 to 7 setae on arthrite, and palp consisting of coxobasis and endopod; coxobasis with 2 setae on medial margin, 3 setae (exopodal setae) on outer margin, and usually with 1 small seta representing epipodite; endopod with 3 setae on distal margin. Maxilla obscurely 2- or 3-segmented, armed with up to 10 setae. Maxilliped consisting of syncoxa, basis, and small 2-segmented endopod with small terminal claw; armed with 0 to 2 setae on syncoxa, 2 setae on basis. Legs 1-4 biramous with at most 2-segmented rami, lacking inner seta on coxa, but with outer seta on basis. Exopods 1 or 2-segmented; endopods occasionally 1-segmented in leg 1, but 2-segmented in legs 2-4. Segmentation of leg rami often incomplete. Basis of leg 1 lacking inner distal element. Each pair of legs 1-4 asymmetrical between right and left sides (except symmetrical in B. macrçpus Canu, 1891). Right exopods usually armed with spines and left exopods with setae. Leg 5 lobate or digitiform, positioned dorsolaterally or laterally on somite; armed with 4 setae; left and right legs widely separated from each other.

Type species. Bçtryllçphẚlus ruber Hesse, 1864, by original designation.

Remarks. According to Schellenberg (1922), three species in the genus Bçtryllçphẚlus have symmetrical exopods of legs 1-4: B. aspẚnçsus Schellenberg, 1922, B. macrçpus Canu, 1891, and B. ruber Hesse, 1864. Of these three, B. ruber was redescribed by Ooishi (1999) and was shown to have asymmetrical legs 3 and 4. Ooishi (2014b) restudied B. aspẚnçsus and mentioned that right and left endopods of leg 4 are armed with different numbers of setae (6 and 7, respectively), which means that at least leg 4 of this species is also asymmetrical. Therefore, within the genus Bçtryllçphẚlus the only species that exhibits true symmetry in all pairs of swimming legs is B. macrçpus, as redescribed by Ooishi (1996: 179).

Lang (1948) was of the opinion that the structure and armature of the swimming legs was highly variable in Bçtryllçphẚlus species, and subsequently Stock (1970) refrained from using leg structure for distinguishing between the species he was studying. The variability Lang (1948) mentioned mainly referred to the symmetry and segmentation of legs, and we have been unable to confirm the existence of any infraspecific variability in leg setation with respect to all of the species we have examined in this account, with the exception of B. nçrvegẚcus in which the exopod of the right leg showed variation in setation. On the evidence available to us, we have found leg setation to be an extremely valuable taxonomic character for the recognition of species of Bçtryllçphẚlus.

Ooishi & Illg (1988) recognized two female morphotypes in Bçtryllçphẚlus: type A, with a 4-segmented abdomen, and type B which has an apparently 5- to 8-segmented abdomen. Huys & Boxshall (1991) suggested the latter condition was the result of secondary annulation and Boxshall & Halsey (2004) considered that the female abdomen was primitively 4-segmented but that this segmentation was obscured by secondary annulations in type B species. Subsequently, Ooishi (2000) divided morphotype A into subgroups I and II, based on leg armature patterns. However, the distinctiveness of these subgroups has been blurred due to the discovery in the present work of several new species that have leg setation patterns that deviate markedly from both of Ooishi’s patterns.

Bçtryllçphẚlus currently comprises 19 valid species ( Ooishi, 2014d). Thirteen new species are described in the present work. The numbers of armature elements on rami of the right and left legs 1-4 in Bçtryllçphẚlus species are compared in Table 2 .

*Exopod of right leg 4 of B. nçrvegẚcus is armed with 6 or 7 spines