taxonID	type	description	language	source
88206C6BFFBD0369FEFFF92FFEEDC821.taxon	type_taxon	Type species: E. curticauda Boeck, 1873.	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
88206C6BFFBD0369FEFFF92FFEEDC821.taxon	diagnosis	Generic diagnosis (modified and tightened from Gee 1994): Cletodidae. Body almost cylindrical, without clear demarcation between pro- and urosome. Segmentation welldefined, segments strongly sclerotized, in the individual species with ridges running at different transverse and longitudinal angles. Sensilla on body somites often arising from small pedestals. Rostrum fused to cphth, triangular in shape, with rounded or bifid tip. Furca of variable shape, rami of differing length, sometimes sexually dimorphic, carrying 7 setae. Females with last thoracic and first abdominal somites fused to form a genital double somite. Copulatory pore located posterior to genital slit; female P 6 with both lobes fused to clasp-like cuticular crest, with 1 – 2 small setae. Female A 1 5 - segmented, fourth segment smallest, male A 1 6 – 7 - segmented, subchirocer. A 2 with allobasis that bears 0 – 1 abexopodal seta; exopod small, 1 - segmented, with 1 lateral and 1 apical seta; endopod apically with 3 spines, 2 geniculate setae and 1 minute seta; laterally with 2 spines but lacking additional tiny seta. Md with gnathobase that bears or lacks distal seta; md palp consisting of single lobe that carries 3 – 4 setae. Mxl praecoxal arthrite with 4 – 5 apical setae / spines and 2 surface (tube) setae; coxa distinct, with 1 – 2 setae; exo- and endopod fused with basis, carrying at most 6 setae. Mx syncoxa with 2 distinct endites, each bearing 3 elements, one of which anvil-shaped in distal endite in some species; allobasis not fused with syncoxa, with 3 elements: 1 claw that is fused with allobasis and 2 slender setae; endopod represented by 2 setae that are often fused together basally. Mxp with syncoxa that bears 1 strong uni- or biplumose seta, allobasis lacking seta, endopod short, squarish, with apical claw and 1 accessory seta that varies in length. P 1 – P 4 with 3 - segmented exo-, and 2 - segmented endopods. Exp- 2 without inner seta. Apical setae of P 1 in some species brush-like. P 1 enp- 2 with only 1 apical seta (postulated autapomorphy). Male P 3 endopod sexually dimorphic or not. P 4 enp- 2 without inner seta (postulated autapomorphy). P 5 baseoendopods not fused medially, with several tube pores, exopod fused with benp or separate. Female endopodal lobe narrowed, moderately to well developed in length, with 2 – 3 setae (postulated autapomorphy); male endopodal lobe minute, with 2 setae; exopods longer than endopods in both female and male; female exopod with 2 – 4, male exopod with 2 setae, of which at most 1 located at outer margin (postulated autapomorphy).	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
88206C6BFFBE037CFEFFFC47FD4ACAF5.taxon	materials_examined	Examined material listed in Table 2.	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
88206C6BFFBE037CFEFFFC47FD4ACAF5.taxon	description	Redescription of female Habitus (Figs 2 A – C, 3 A, B) elongate, subcylindrical, slightly dorso-ventrally depressed, tapering posteriorly from the posterior edge of the cphth; length 462 – 547 µm (measured from tip of rostrum to posterior edge of FR; mean = 499 µm, n = 4). No clear distinction between pro- und urosome. Cuticle strong and thick, with segments wellarticulated by pronounced arthrodial membranes. Body often curved towards the dorsal side in lateral view. Cphth rectangular in dorsal view, tapering anteriorly towards rostrum, with 4 strong longitudinal ridges and large patches of fine setules between them. With several sensilla distributed across the surface and margins of the cphth, with sensilla on dorsal posterior margin arising from tiny protuberances; a pair of pores located centrally on the cphth in lateral view; its margins ornamented by a dense row of setules. Thoracic somites (including anterior half of GDS) with transversal groove in anterior half, most pronounced dorsally, with a single dorsal and a pair of lateral ridges spanning the groove, appearing as “ X ” under the microscope; the lateral ridges except on the anterior half of the GDS raised and not flush with the surrounding somite; transversal groove of the P 2 - bearing somite shallow. P 2 - to P 4 - bearing somites with rounded pleurites. Each thoracic somite with 1 central dorsal and a pair of lateral tube pores, all originating near the ridges spanning the transversal groove. P 2 bearing somite with 4 pairs of sensilla each arising from a small pedestal, one of the pairs distinctly finer, and a pair of sensilla without pedestals near posterior margin; P 3 - and P 4 - bearing somites with 5 pairs of sensilla arising from small pedestals, one of the pairs distinctly finer; P 5 - bearing somite with 3 pairs of sensilla arising from small pedestals; thoracic part of GDS with a pair of sensilla with pedestals and a pair without. Last thoracic and first abdominal somite completely fused, forming a GDS, transition between the somites only marked by several dense rows of setules and the sensilla of the thoracic part. Abdominal somites (including posterior half of GDS) with transversal groove in anterior half, around entire circumference, though shallow on ventral side; with a pair of dorsal and a pair of lateral ridges spanning the groove, not raised. Each abdominal somite with a pair of lateral tube pores near the posterior edge of the transversal groove and a dorsal pair near the posterior margin. Abdominal part of GDS with 4 pairs of sensilla arising from small pedestals near posterior margin, second abdominal somite with 3 pairs, and third somite without sensilla. Abdominal part of GDS with a row of fine setules at posterior edge of the transversal groove, other abdominal somites with a row of fine setules at both the anterior and posterior edge. All body somites except cphth and telson with 3 dense rows of fine setules on posterior margin; all arthrodial membranes except between cphth and P 2 - bearing somite with a single row of fine setules just before the anterior margin of the following somites, setules appearing irregularly spaced (gaps due to broken off setules?). Telson (Fig. 3 A – C) with transversal groove, most pronounced laterally, dorsally and ventrally very shallow, each edge ornamented with a row of fine setules; with a pair of lateral ridges spanning the groove. Telson bearing two pairs of lateral tube pores, one near anterior edge of transversal groove, and one originating from within a row of strong spinules located near posterior margin of the telson. Operculum semi-circular, dentate, with sensilla arising from a small pedestal on each side; ornamented at its base with a row of long and fine setules. Several rows of long and thin spinules surrounding anal opening; dorsal surface with a row of spinules leading from the sides of the operculum to each FR, splitting into two rows each along the way. Rostrum (Figs 2, 3 A, B, 4 A) fused to cphth, broadly triangular with a convexly rounded to minutely bilobed tip between the 2 apical sensilla, with short median tube pore on the ventral surface; tip ornamented with a row of fine setules, dorsal surface with small pit near the tip bearing fine setules. FR (Figs 3 C, 4 B) very long and slender, around 6 to 8 times as long as wide; ornamented with long setules distributed over its entire surface. With 2 tube pores: 1 laterally near base of the FR, and 1 originating ventrally at approximately three quarters of the length of the FR. Seta I and II arising together on the outer margin at approximately the proximal third of the FR length, unequal in size; seta III subapical on the outer margin; seta IV fused to seta V at its base, the latter arising from the posterior margin of the FR together with seta VI; seta V sparsely biplumose, about as long as the entire abdomen, telson, and FR combined; seta IV and VI about the same length; seta VII arising dorsally, slightly before the midpoint of the FR, tri-articulate, at the distal third biplumose. A 1 (Figs 4 C, D, 5 A – D) short, 5 - segmented (Fig. 5 A), covered with dense rows of small spinules on either the entire dorsal surface (segments 3 – 5) or dorsal surface near the posterior margin (segment 2) (Figs 4 C, 5 B). Segment 1 with a row of spinules and 1 biplumose seta on the anterior margin (Fig. 5 B). Segment 2 (Fig. 5 B, C) with 8 setae: 1 uniplumose, 2 biplumose and 5 bare setae. Segment 3 (Fig. 5 B, D) with 7 armature elements and an aes: 1 unipinnate spine with few, strong pinnules and 6 bare setae; aes arising from a ventral protrusion of the segment together with 2 of the bare setae, 1 of which is fused to the base of the aes. Segment 4 small, with 1 bare seta (Fig. 5 B). Segment 5 with an acrothek (2 setae and aes) and 9 further elements: 2 unipinnate spines with few, strong pinnules on the anterior margin, a seta with an apical brush near the posterior margin (Figs 4 D, 5 B), and 6 bare setae. Setal formula: 1 - 1; 2 - 8; 3 - 6 + (1 + aes); 4 - 1; 5 - 9 + acrothek. A 2 (Fig. 6 A) comprised of coxa, allobasis, 1 - segmented exp, and 1 - segmented enp. Coxa well-developed with a row of spinules. Allobasis with conspicuous partial suture and row of spinules near base of exp; proximal (basal) abexopodal seta present, unipinnate; the distal abexopodal seta completely reduced, missing. Exp well-developed, one-segmented, with 2 setae: a biplumose lateral seta and an asymmetrically bipinnate apical seta with a row of spinules at its base. Enp elongate, ornamented with 2 rows of large strong spinules on the inner margin and 2 rows of setules on the dorsal surface; with 8 elements: 2 large unipinnate spines on the inner margin, and 2 bare spines, 2 geniculated setae, and a highly modified spine with a minute seta fused to its base on the apical margin. Modified spine pinnate along the outer margin, with a few large and strong pinnules on the inner margin. Md (Fig. 6 B, C) with elongated gnathobase ending in 3 bi-cuspidate teeth; palpus 1 - segmented, carrying 3 plumose setae that correspond to the (basal) seta 2 and the (endopodal) setae 3 and 5. Mxl (Fig. 6 D) basally with 3 rows of spinules; praecoxal arthrite distally slightly damaged, only 1 seta and 3 spines detectable (other spines broken off); additionally, with 2 surface setae; coxa small, twice as long as broad, apically with 1 robust uniplumose spine; basis with 3 apical setae; endopod represented by 1 seta, exopod by 2 setae. Mx (Fig. 6 E) syncoxa with 2 rows of small spinules and 2 well-developed endites, each bearing a bipinnate spine and 2 bi-articulate setae. Allobasis with 2 rows of small spinules and 4 bare setae, 2 of which fused at the base, representing the enp. Mxp (Fig. 6 F) prehensile, syncoxa with visible partial suture, a row of spinules, and an uniplumose seta. Allobasis with a row of long spinules on both the outer and the inner margin, without armature. Enp represented by a minute segment. Endopodal claw separate, bearing a small accessory seta fused to its base, as well as a single pinnule. P 1 (Fig. 7 A, Table 3) praecoxa, coxa, and intercoxal sclerite not illustrated due to damage; praecoxa bearing a row of spinules on distal margin; coxa with 2 rows of spinules on the anterior surface and a patch of setules on the inner surface, similar to P 2 and P 3 (see below); basis ornamented with 3 rows of large spinules: 1 row in front of the articulation of the enp, and 1 row each accompanying the 2 armature elements: a biplumose outer seta and an asymmetrically bipinnate inner spine bearing strong pinnules. Exp 3 - segmented, segments 1 to 2.5 times as long as wide, each ornamented with a row of long and strong spinules on the outer margin and a row of long fine spinules on the inner margin; exp- 1 additionally with 2 rows of spinules on anterior surface and up to 3 very long and fine spinules on the proximal outer margin; exp- 1 and exp- 2 also with a small spinule on the inner distal margin; each bearing a bipinnate outer spine, exp- 3 with 4 elements: 2 bipinnate outer spines, the distal one with distinctly longer pinnules, and 2 apical biplumose setae with a long brush-tip on the outer margin. Enp 2 - segmented, with enp- 1 small, wider than long, and enp- 2 elongate, about 4 times as long as wide; enp- 1 ornamented with a row of small spinules on the distal margin; enp- 2 with a row of long slender spinules on the outer and a row of long and fine spinules on the inner margin, carrying a bipinnate outer spine with distantly spaced pinnules, a long biplumose apical seta, and a minute inner seta. P 2 – P 4 like in male (see below), except P 3 enp- 2 (Fig. 7 B) lacking apophysis, with 3 elements: a bipinnate outer spine and 2 biplumose apical setae. The setal formula of P 1 – P 4 is given in Table 3. P 5 (Fig. 7 C) not fused medially. Benp with well-developed setophore bearing a long bare seta, and with a well-developed endopodal lobe, reaching up to approximately the first quarter of the exp; ornamented with a patch of setules on the anterior surface near the setophore, a row of setules on the outer distal margin, and a row of spinules in front of the articulation of the exp; tube pore present on anterior surface near setophore. Endopodal lobe ornamented with a spinule on the inner margin, and a row of strong spinules near the distal margin; 3 armature elements present: a biplumose apical seta, a bipinnate apical spine, and a bipinnate inner spine. Exp separate, about 5 times as long as wide, covered with long setules distributed over the entire surface; ornamented with 2 rows of strong spinules originating from two steps in the distal inner margin; 1 long tube pore present, originating from the distal anterior surface; 4 armature elements: 2 outer setae, the proximal one being biplumose, a bare apical seta, and an unipinnate inner spine. GF (Fig. 7 D) with vestigial P 6, fused medially, bearing 2 bare setae of variable length on each side. Single copulatory pore mostly covered by an integumental fold. GF with a pair of pores, each with 3 tubes, arising between genital slit and copulatory pore. Description of the male Body (Fig. 8) like in female, but slenderer, slightly smaller with length approximately 455 µm (n = 1), and without GDS. Rostrum, Telson, and FR like in female. A 1 (Fig. 9) short, 6 - segmented, sub-chirocer. Segment 2 with dense rows of small spinules on dorsal surface near its distal margin; dorsal surface of segments 3 and 4 fully covered by such rows. Segment 4 with a row of long and strong spinules near the anterior (palmar) margin. Segment 1 with 5 rows of spinules and a biplumose seta on anterior face. Segment 2 with 9 elements: 2 uniplumose setae, a biplumose seta, and 6 bare setae. Segment 3 with 8 bare setae. No minute segment between segment 3 and swollen segment. Segment 4 swollen, with 13 elements and an aes: 4 unipinnate spines with few long and strong pinnules near the anterior / palmar edge and 9 bare setae, one of which is fused to the base of the aes. Segment 5 small, with a single bare seta. Segment 6 claw-shaped, with 11 elements and an aes: a seta with an apical brush near the posterior margin and 10 bare setae, one of which is fused to the base of the aes. Setal formula: 1 - 1; 2 - 9; 3 - 8; 4 - 12 + (1 + aes); 5 - 1; 6 - 10 + (1 + aes). A 2, mouthparts, and P 1 like in female. P 2 (Fig. 10 A, Table 3) praecoxa well-developed, with a row of slender spinules on distal margin. Coxa with 2 rows of long spinules on the anterior surface and a patch of setules at the inner margin; basis with a row of long spinules in front of the articulation of the enp, a row at the inner margin, and a row accompanying the biplumose outer seta. Exp 3 - segmented, segments 2 to 3 times as long as wide, ornamented like in P 1 (see above). Exp- 1 and exp- 2 with a bipinnate outer spine like in P 1, exp- 3 with 4 armature elements: 2 outer spines, the distal one with distinctly longer pinnules, and 2 biplumose apical setae. Enp 2 - segmented, with enp- 1 wider as long, and enp- 2 about 5 times longer than wide. Enp ornamented like in P 1 with the addition of 2 spinules on the inner distal margin of enp- 2. Enp- 2 bearing 2 biplumose apical setae. P 3 (Fig. 10 B, Table 3) praecoxa well-developed, triangular, with a row of slender spinules on distal margin. Coxa and basis like in P 2. Exp 3 - segmented, segments about 1.5 to 2.8 times as long as wide, ornamented like in P 1 and P 2. Exp- 1 and exp- 2 with a bipinnate outer spine, like in P 1 and P 2, exp- 3 with 5 armature elements: 2 bipinnate outer spines, the distal one with distinctly longer pinnules, 2 biplumose apical setae, and a biplumose inner seta. Exp- 2 with a pore on the anterior surface near the distal inner margin. Enp 2 - segmented, with enp- 1 small, wider than long, and enp- 2 long and slender, bearing an outer apophysis. Enp- 2 about 5 times as long as wide (excluding apophysis). Enp with the same ornamentation as P 2, except only 1 spinule on the inner distal margin of enp- 2. Armature like in P 2, with enp- 2 bearing 2 long, biplumose apical setae. P 4 (Fig. 11 A, Table 3) praecoxa small, triangular, with a row of slender spinules on distal margin. Coxa and basis like in P 2 and P 3. Exp 3 - segmented, segments 1.2 to 2.5 times as long as wide, ornamented like in P 1 – P 3. Exp armature like in P 3. Enp 2 - segmented, with enp- 1 small, wider than long, and enp- 2 slender, about 3.5 times as long as wide. Enp ornamentation like in P 3, enp- 2 bearing 3 armature elements: a bipinnate outer spine, and 2 apical setae, with the outer one biplumose and the inner one bare and minute. P 5 (Fig. 11 B) not fused medially. Benp with well-developed setophore bearing a bare seta, endopodal lobe short and square; with row of strong spinules near the distal edge of the endopodal lobe; 2 tube pores present, one located on the anterior surface near the setophore and one at the midpoint of the inner margin. Endopodal lobe with 2 apical elements: a minute, very fine bare seta, and a bipinnate spine. Exp completely fused to benp, about 3.5 times longer than wide; ornamented with long spinules distributed across the distal two thirds of the exp, and with 2 rows of strong spinules originating from 2 steps on the distal inner margin; tube pore present on the inner margin at approximately two thirds of the exp length; 2 armature elements: a bare outer seta and a bare apical seta.	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
88206C6BFFBE037CFEFFFC47FD4ACAF5.taxon	discussion	Remarks: The setae of the female P 6 appeared highly variable in length between different individuals, ranging from the length shown in Fig. 9 D up to almost twice as long. The minute seta on the male P 5 endopodal lobe (Fig. 13 B) has proven to be rather difficult to spot in several specimens, often being hidden behind the exp. While the male P 5 endopodal lobe thus seems to only bear a bipinnate spine in some cases (e. g. Folkers & George 2011), we were able to confirm the presence of the minute seta in all examined specimens. Phylogenetic analysis The phylogenetic analysis presented below was conducted with two main objectives: the attempt (i) to establish the genus Enhydrosoma as a monophylum, and (ii) to characterise the species E. sarsi on the basis of autapomorphies as an independent taxon that can be distinguished phylogenetically from the other representatives of the genus. Nonetheless, because not all species could be considered due to the limiting factors mentioned in the introduction, the result is subject to a certain degree of uncertainty.	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
88206C6BFFAB0379FEFFFE32FA8DCF11.taxon	discussion	Because the phylogenetic relationships within the Cletodidae are not yet resolved, and in order to identify possible autapomorphies of a monophylum Enhydrosoma, we selected five genera as outgroups for our analysis, whose representatives had previously been assigned to Enhydrosoma: Geehydrosoma, Kollerua, Schizacron, Spinapecruris and Strongylacron (not considered here: Acrenhydrosoma Lang, 1944, Dyacrenhydrosoma Gee, 1999, Neoacrenhydrosoma Gee & Mu, 2000, and Paracrenhydrosoma Gee, 1999). Moreover, Limnocletodes Borutzky, 1926 was added as a presumed distant relative. The comparison was based on 79 morphological characters (Table 4). Of these, 20 (about 25 %) were identified as potential convergences. In the following, the term “ character ” generally refers to the derived (apomorphic) state; if the plesiomorphic state is meant, this is explicitly stated. The possible relationships between the compared genera are shown in Figure 12. To avoid constantly repeating the mention of Table 4 and Figure 12, the indication of the clades always refers to both of them. All seven taxa could be grouped into a monophyletic taxon based on the derived states of characters 1 – 6 (clade A). It should be noted, however, that this assessment is preliminary; since our analysis did not include all Cletodidae, the seven taxa may in fact constitute a paraphyletic group. Future comprehensive analyses will have to clarify this, but for the purposes of the analysis attempted here, our finding is sufficiently conclusive. Characters 7 – 13 clearly distinguish Limnocletodes as a monophylum, with all other taxa forming a sister-group based on characters 14 – 28 (clade B). Characters 29 – 32 are found in Enhydrosoma, Geehydrosoma, Kollerua and Schizacron, which might indicate a closer relationship between these taxa. Otherwise, also Limnocletodes exhibits character 29, Limnocletodes and Spinapecruris both display character 30, and Strongylacron shows characters 31 and 32 (Table 4), which in turn may indicate a certain incongruity in the occurrence of the characters. This could point to possible convergent developments. A further comparison of characters showed that characters 33 – 39 occur in all members of clade B but not in Enhydrosoma, which exhibits the plesiomorphic state in all seven characters. Thus, as discussed in detail below, we postulate characters 29 – 32 as autapomorphies of Enhydrosoma, whilst their simultaneous occurrence in other taxa is hypothesized as convergently developed synapomorphies in Geehydrosoma and Kollerua (= clade D) and as convergently developed autapomorphies in the remaining corresponding taxa. Furthermore, we hypothesise Enhydrosoma as the potential sister-group of Geehydrosoma, Kollerua, Schizacron, Strongylacron and Spinapecruris, which form a monophylum (clade C) by means of characters 33 – 39 (with characters 33 and 35 – 38 as convergent deviations in Limnocletodes). Characters 40 – 46 proved to be very robust for establishing a sister-group relationship between Geehydrosoma and Kollerua (clade D; only exception is character 46 that also occurs convergently in Limnocletodes). Both genera can also be well characterised by their own autapomorphies. Clade D also appears to be well-justified as sister-group to a clade E formed by Schizacron, Strongylacron and Spinapecruris (characters 59 – 61). In that clade, Schizacron is the first taxon to split off from the other two genera (characters 62 – 65), while Strongylacron and Spinapecruris can be grouped together (clade F) by synapomorphies 66 – 72. Though, they can also be clearly distinguished from each other on the basis of their own derived characters (Table 4, Fig. 12). Phylogenetic comparison within Enhydrosoma In order to phylogenetically justify E. sarsi as a distinct species, the first step was to select Enhydrosoma species for comparison based on the available descriptions. As previously mentioned, not all 37 species (cf. Table 1) could be considered, but only 24. Nonetheless, during the course of the comparison, it became apparent that two further species – E. pectinatum Wells & Rao, 1987 and E. wellsi Bodin, 1968 – also had to be excluded because they do not belong to the genus Enhydrosoma. The comparison within the genus was therefore limited to 22 species.	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
88206C6BFFAE0370FEFFFB57FAC9CEBD.taxon	discussion	To characterise E. sarsi, all 22 species were compared with each other on the basis of 28 characters (Table 5, characters E 1 – E 28). Fifteen characters coincide with those in Table 4 (see Table 5, second column), but additional characters were also added. Here, the difficulties mentioned above became apparent, too. A comparison of the male antennula for example was not possible, because the male A 1 is insufficiently described or not described at all in 14 of the 22 species. We also disregarded the structure of the male P 3 because it is complex (in particular the segmentation of the endopod and the shape and ontogenetic origin of the apophysis) and not yet fully understood (cf. Gee 1994). Extensive research is required here, which must also include various copepodid stages, something that could not be achieved within the scope of this study. For all these reasons, we refrained from conducting a comprehensive analysis within the genus and limited ourselves to characterising E. sarsi on the basis of autapomorphies that are as unambiguous as possible. To this end, we carefully compared the here re-described E. sarsi with the descriptions of the other 21 species. Different characters were weighted according to their presumed original or derived state. The results showed that E. sarsi can be unequivocally established as a distinct species on the basis of six autapomorphies (Table 5, characters E 23 – E 28). For example, the antennula of both sexes has a blunt, short seta on the last segment, the tip of which ends in long pinnules (character E 23, cf. Figs 4 C, D, 5 B). Furthermore, in the female, the dorsal surface of antennular segments 2 – 5 is at least partially (character E 24) or completely densely covered with fine spinules (characters E 25 – E 27; cf. Figs 4 C, 5 B), and on the P 4 enp- 2, the inner apical seta is strongly reduced (E 28, cf. Fig. 11 A). Characters E 24 and E 27 were also described by Fiers (1996) for E. lacunae; however, we assume a convergent development.	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
88206C6BFFAE0370FEFFFB57FAC9CEBD.taxon	description	Characterisation of Enhydrosoma sarsi As can be seen in Table 5, for a large number of the 28 characters, there is no information available even for the Enhydrosoma species we compared, which makes it difficult to investigate intrageneric relationships. This number increased considerably when we examined additional characters. However, we found six characters for the characterisation of E. sarsi (Table 5, characters E 23 – E 28): Character E 23 refers to a specially constructed seta on the last segment of both the female and male antennulae. This seta ends in a blunt tip that is brush-like and armed with fine pinnules (cf. Figs 4 D, 5 B, 9 B, F). Until such seta may be documented in other species, we consider its brush-like structure to be autapomorphic for E. sarsi. Characters E 24 – E 27 relate to segments 2 – 5 of the female antennula. In E. sarsi, these are densely covered with tiny spinules on their dorsal surface (cf. Fig 4 C), which is not the case in the other compared representatives of the taxon – their antennular segments are devoid of spinules, with the exception of the second and fifth segments in E. lacunae (cf. Fiers 1996) and in Schizacron (cf. Table 4, character 64). These characters are therefore also to be regarded as autapomorphies of E. sarsi, whereby we consider the occurrence of spinules in E. lacunae (and Schizacron) to be convergent. We attribute this assumption to a presumed lack of close relationship between the two species, which can be deduced from the grouping of characters in Table 5. Character E 28, the strong reduction of the inner apical seta on P 4 enp- 2, is, like character E 23, exclusively present in E. sarsi. Thus, E. sarsi can be clearly characterised as a distinct species based on the six autapomorphies E 23 – E 28.	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
88206C6BFFA60371FEFFFC63FB81CE99.taxon	description	urn: lsid: zoobank. org: act: C 6 F 9 A 442 - 3 A 5 A- 4 E 7 C- 8542 - F 0 CFB 0166416	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
88206C6BFFA60371FEFFFC63FB81CE99.taxon	discussion	When establishing Geehydrosoma for the classification of Enhydrosoma intermedia Chislenko, 1978 (cf. Chislenko 1978), Kim et al. (2014) provided a detailed generic diagnosis, which also led them to transfer E. brevipodum Gómez, 2004 (cf. Gómez 2004), to the newly established genus. When compiling the Enhydrosoma species for the phylogenetic analysis presented here, we noted that E. pectinatum, described by Wells & Rao (1987) from the Andaman and Nicobar Islands (eastern Gulf of Bengal, Indian Ocean), almost completely corresponds to the generic diagnosis of Geehydrosoma. The most striking (derived) character is the P 5, which in E. pectinatum is basically constructed in the same way as in Geehydrosoma intermedia (Chislenko, 1978) and G. brevipodum (Gómez, 2004). However, it also resembles the two species in other characters, such as the lack of sexual dimorphism in the P 3, the structure of the mouthparts, and the formation of setae VI and VII of the P 1 exopod as brush setae. Even though at least single characters can be found in other representatives of Enhydrosoma (for instance, brush setae in P 1 exp- 3 in e. g. E. caeni, E. curticauda, E. longifurcatum) (Raibaut 1965, Bodin 1970, Gee 1994) and even in single species of other cletodoid genera (e. g. lacking sexual dimorphism in the male P 3 endopod in Cletodes limicola, C. spinulipes) (cf. Lang 1948, Por 1967, Gee 1994), their combination in the representatives of Geehydrosoma justifies the transfer of E. pectinatum to that taxon as G. pectinatum (Wells & Rao, 1987), comb. nov.	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
88206C6BFFA60370FEFFF9DFFDF9C9B1.taxon	description	urn: lsid: zoobank. org: act: A 4 D 130 D 5 - BFE 0 - 4 FA 4 - 9603 - B 36 C 858 ACDCB Bodin (1968) described Enhydrosoma wellsi Bodin, 1968 from the Gulf of Gascogne (France). He was aware that the species differed from the other known representatives of the genus at that time by possessing an inner seta on exp- 2 of P 2 – P 4 (Bodin 1968: 81), which is absent in the other representatives of the genus. However, although he himself did not rule out a similarity to Cletodes, he refrained from assigning E. wellsi to that genus because the third segments of the exopods of P 3 and P 4 are not remarkably elongated compared to the first two segments. Instead, Bodin (1968) considered that the generic diagnosis of Enhydrosoma could be expanded to include E. wellsi. Later, Bodin (1997) noted that Drzycimski (1969) suspected E. wellsi to be a synonym of Cletodes latirostris Drzycimski, 1967, which Bodin (1997) for his part rejected. However, as we were unable to find this statement in Drzycimski’s (1969) work, we felt compelled to ignore Bodin’s (1997) comment.	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
88206C6BFFA60370FEFFF9DFFDF9C9B1.taxon	discussion	Our comparison of Bodin’s (1968) description led us to conclude that E. wellsi is not an Enhydrosoma species, but in fact a representative of Cletodes. Apart from the difference noted by Bodin (1968) in (i) the armouring of the of P 2 – P 4 exps- 2 with an inner seta in E. wellsi (which is lost in all Enhydrosoma species), it exhibits a number of further (diagnostic) characters that justify its transfer to Cletodes: (ii) the A 2 exopod is tiny, knob-like and bears only one seta; (iii) the md palpus still shows the ancestral state bearing all six setae, which is part of the groundpattern of Cletodinae (George 2020) but not the case in Enhydrosoma (at least setae 1 and 4 are lost); (iv) the exp- 3 of P 3 and P 4 lacks an inner seta, whilst all Enhydrosoma species (except E. serdarsaki) still carry that element. Enhydrosoma serdarsaki, described by Sonmez et al. (2019), like E. wellsi shares the loss of the inner seta on the exp- 3 of P 2 – P 4 (character iv). Although Sonmez et al. (2019: 823) also recognised the differences between the two species based on the characters i – iii mentioned here, they refrained from transferring E. wellsi to another genus or establishing a separate genus for it. In our opinion, however, the differences in characters i – iv between E. wellsi and the other Enhydrosoma species on the one hand, while these characters coincide with Cletodes on the other, are so clear that the here undertaken transference of E. wellsi to Cletodes as C. wellsi (Bodin, 1968), comb. nov. seems to be fully justified to us thanks to Bodin’s (1968) detailed description. We further assume that the reduction of the inner seta on the exp- 3 of P 2 – P 4 (character iv) in E. serdarsaki represents an autapomorphic character complex that has evolved convergently with Cletodes.	en	Kunze, Mike, Khodami, Sahar, Ostmann, Alexandra, Packmor, Jana, George, Kai Horst (2026): Redescription of Enhydrosoma sarsi (Scott, 1905) (Copepoda, Harpacticoida, Cletodidae T. Scott) from the western Baltic Sea (Germany) and remarks on the systematics of Enhydrosoma Boeck, 1873. Zootaxa 5768 (3): 335-369, DOI: 10.11646/zootaxa.5768.3.2, URL: http://dx.doi.org/10.7717/peerj.20736
