Heteropsyllus spongiophilus, Novikov & Sharafutdinova, 2021

Novikov, Aleksandr & Sharafutdinova, Dayana, 2021, Two new Canthocamptidae (Copepoda, Harpacticoida) from sponges of the Kara and Laptev Seas, Zootaxa 4948 (3), pp. 336-362 : 337-347

publication ID	https://doi.org/ 10.11646/zootaxa.4948.3.2
publication LSID	lsid:zoobank.org:pub:C823F971-9ECC-4ADE-9CB0-9252D4BBFB0E
DOI	https://doi.org/10.5281/zenodo.4667589
persistent identifier	https://treatment.plazi.org/id/C170192C-44F3-416C-8206-D71A6B003DDB
taxon LSID	lsid:zoobank.org:act:C170192C-44F3-416C-8206-D71A6B003DDB
treatment provided by	Plazi
scientific name	Heteropsyllus spongiophilus
status	sp. nov.

Treatment

Heteropsyllus spongiophilus sp. nov.

http://zoobank.org/ C170192C-44F3-416C-8206-D71A6B003DDB

Etymology. The species is named so because it was found only on sponges. The specific epithet is adjective.

Type locality. Kara Sea (73.08556°N, 67.60111°E) in sample with sponges Polymastia grimaldii ( Topsent, 1913) ; Tetilla sibirica ( Fristedt, 1887) ; Semisuberites cribrosa ( Miklucho-Maclay, 1870) ; Suberites sp. Depth 55 m.

Material examined. Holotype: female, dissected and mounted on 2 slides (BP 542/1-a; 542/1 -b). Allotype, male dissected and mounted on one slide (542/2). Paratypes: one female dissected and mounted on one slide (542/3), two females and one V copepodite undissected formalin-preserved (542/4) .

Description. Female. Body short, flattened. Total body length of holotype from anterior margin of rostrum to posterior margin of caudal rami: 0.457 mm. Fixed individuals have a pink tint. Naupliar eye not discernible. Cephalothorax ( Figs. 1A,B View FIGURE 1 ) consisting of cephalosome with fused first pedigerous somite, wider as remaining somites, largest width 0.131 mm. Rostrum ( Fig. 1C View FIGURE 1 ) clearly separate from the cephalothorax, with one pair of sensilla. Posterior margin of cephalothorax and second-fourth pedigerous somites smooth; posterior margin of fifth pedigerous somite with serrulate hyaline frills.

Cephalothorax with 33 pairs of sensilla, one unpaired sensilla and 6 pairs of pores. Second pedigerous somite with 9 pairs of sensilla, one unpaired pore and with several rows of small spinules. Third pedigerous somite with 9 pairs of sensills and one dorsal row of small spinules. Fourth pedigerous somite with 8 pairs of sensilla and one pair of pores. Fifth pedigerous somite with 3 pairs of sensilla, one pair of pores, one dorsal row of small spinules and paired lateral rows of large spinules.

Abdomen ( Figs. 2 View FIGURE 2 A-C) short and wide, consisting of genital-double somite, two free abdominal somites and anal somite with caudal rami. All somites except anal somite on posterior margin with serrulate hyaline frills. Genital-double somite wider than long, flattened; with rows of small spinules, on posterior margin with lateral and dorso-lateral rows of spinules; with 7 pairs of sensilla, one pair of lateral pores and one pair of ventral large tube pores. P6 fused with somite with 3 naked setae. Genital field large laterally with sieve; copulatory pore shifted to the first urosomite, copulatory duct strongly chitinized wide and long, extending proximally to pair of labyrinthic rounded ducts.

First free abdominal somite with three pairs of sensilla, one pair of lateral and one pair of ventral pores; on posterior margin with circumsomitic transverse spinular row with gap dorsally. Second free abdominal somite on posterior margin with ventro-lateral row of spinules. Anal somite with one pair of sensilla, three pairs of lateral pores, one pair of ventral pores and row of spinules postero-laterally. Anal operculum long with lots (holotype with 18) posterior spinules.

Caudal rami ( Figs. 2 View FIGURE 2 A-C) square, length/width ratio 1, with one dorsal and two ventral pores; with one row of spinules on interior margin and row of spinules at base of setae I-III. Seta I small, located between setae II and III. Apical setae IV and V ( Fig. 1D View FIGURE 1 ) long, with spinules, length 0.137 mm and 0.321 mm respectively. Seta VII triarticulated.

Antennule ( Fig. 3A View FIGURE 3 ): short, 5-segmented. Segment 1 square, with one unipinnate seta, with two rows of spinules proximally and two rows of spinules at base of seta. Segment 2 wide, with 4 pinnate and 5 naked setae. Segment 3 with 3 free pinnate, 4 free naked setae and fused basally pinnate seta and aesthetasc. Distal segment with 2 “pineapple-setae” (sensu Hamond, 1971), 8 naked setae and acrothek consisting of aesthetasc and two setae fused basally. Armature formula: 1-[1],2-[9],3-[7+(1+ae)],4-[1],5-[10+acr].

Antenna ( Fig. 3B View FIGURE 3 ) with allobasis. Coxa with one spinular row. Allobasis with two bipinnate setae. Free endopodal segment with two lateral rows of large spinules, with one free spinulose spine and fused basally small seta and spinulose spine; distally with two rows of spinules; apically with three geniculate setae, two long spines and one small seta; outermost geniculate seta fused basally to small seta. Exopod 2-segmented; first segment with one bipinnate seta and one distal spinular row; second segment with 3 bipinnate setae.

Mandible ( Fig. 4A,B View FIGURE 4 ). Coxa with spinules proximally. Gnathobase massive, with few multicuspidate teeth, spinulose seta; pars incisiva and lacinia mobilis with 4 blunt wide teeth. Pars molaris with sharply-edged. Palp consisting of free basis, 1-segmented endopod and exopod. Basis with two rows of spinules and two pinnate setae; exopod with slender spinules and one pinnate seta; Endopod with one dorsal spinular row, one pinnate proximal seta, two distal pinnate setae and one distal naked seta.

Maxillule ( Fig. 4C View FIGURE 4 ). Praecoxa with 2 rows of slender spinules on outer edge. Praecoxal arthrite medially with 2 rows of spinules and two naked setae; distally with 7 strong spines and two setae. Coxa with row of slender spinules, coxal endite reaching middle of arthrite, with two spinulose setae. Basis with two rows of spinules and 5 pinnate setae. Endopod incorporated into basis, represented by protuberance with two pinnate setae. Exopod free, with spinules and two pinnate setae.

Maxilla ( Fig. 4D View FIGURE 4 ). Syncoxa with several rows of spinules on outer and inner edge as figured, with three endites. Proximal endite with one strong bipinnate seta, middle and distal endites with three setae. Allobasis with 3 setae, one tube pore and massive distal claw. Endopod short with one pinnate proximal seta and three distal naked setae.

Maxilliped ( Fig. 5B View FIGURE 5 ) subchelate. Syncoxa elongated with several rows of spinules as figured, distally with one small naked and one large “rat-tail” setae. Basis with one row of large inner spinules and two rows of outer slender spinules. Endopod on posterior side with one seta, on anterior side with one small seta and one small protuberance, possibly reduced seta or pore. Endopodal claw elongated, with two pairs of long slender spinules.

P1 ( Fig. 5A View FIGURE 5 ) with 3-segmented rami. Praecoxa with row of spinules. Coxa wide, with inner fold, with spinular ornamentation as figured. Intercoxal sclerite very expanded. Basis with proximal pore, medial row of spinules, rows of spinules at base of endopod and exopod, with outer naked seta and inner strong pinnate seta. All endopodal and exopodal segments with outer spinules. First and second exopodal segments with one outer spine; third exopodal segment with tree outer spine and two apical long geniculate setae. Endopod is approximately as long as exopod. First and second endopodal segments with one inner seta, third segment with two rows of spinules on posterior side, distally with outer spine and apical long geniculate seta.

P2 ( Fig. 6A View FIGURE 6 ). Praecoxa with row of spinule. Coxa with inner fold, with one lateral row of spinules and three closely spaced proximal rows of spinules. Basis with proximal pore, medial row of spinules, two rows of slender spinules on inner edge, rows of spinules at base of endopod and exopod; with outer bipinnate seta. All endopodal and exopodal segments with outer spinules. Exopod 3-segmented; first exopodal segment with outer spine, inner row of slender spinules and apically with frill; second segment with outer spine, inner seta, inner spinules and apical frill; third segment with three outer spines, two apical and one inner setae. Endopod 2-segmented; reaching about half of second exopodal segment; first segment with inner seta and pore, second segment with outer spine, two apical setae and two inner setae, on posterior side with spinular row.

P3 ( Fig. 6B View FIGURE 6 ) similar to P2. Praecoxa, intercoxal sclerite and basis as in P2. Coxa with one lateral and three proximal rows of spinules and with one pore. Exopod as in P2, but third exopodal segment P3 with two inner setae. Endopod as in P2, but reaching about 1/3 of second exopodal segment and first segment without pore.

P4 ( Fig. 6C View FIGURE 6 ) also similar to P2. Praecoxa, intercoxal sclerite, coxa and basis as in P2. Exopod as in P2, but third exopodal segment P4 with two inner setae, the distal one with strong spinules. Endopod small, reaching about 1/4 of second exopodal segment, with row of spinules on posterior side; first segment with inner seta; second segment with small naked outer spine and four bipinnate setae.

Armature of swimming legs as follows:

P5 ( Fig. 8A View FIGURE 8 ) with separate right and left baseoendopods. Baseoendopod elongated, reaching about midlength of exopodal segment; with spinular rows on inner and outer side of endopodal lobe and at base of exopod and outer seta; outer seta of basis naked. Endopodal lobe with two pores and five setae. Exopod elongated, length/width ratio 3.45; with long spinules on inner and outer side; with 5 naked setae.

Male. Total body length from tip of rostrum to posterior margin of caudal rami: 0.354 mm. Sexual dimorphism expressed in the antennule, P2–P6, genital segmentation and ornamentation. Abdomen ( Figs. 7 View FIGURE 7 A-C) narrower than female. Ornamentation and sensilla of somites 1, 3-5 as in female, but spinules larger. Somite 2 also as in female, but with on posterior margin circumsomitic transverse spinular row with gap dorsally. P6 fused with first abdominal somite, with three bare setae ( Fig. 7C View FIGURE 7 ). Anal operculum with a lot of spinules (allotype with 26). Caudal rami as in female.

Antennule ( Figs. 3C,D View FIGURE 3 ) 9-segmented, haplocer with geniculation between segments 7 and 8. “Pineapple-setae” located on 5 – 7 segments. Segment 1 with four rows of spinules. Segment 5 with large aestetasc fused at base with long unipinnate seta. Segment 7 with one modified lamellar seta one short modified seta. Segments 7 – 9 with articular surfaces. Segment 8 with three identical modified lamellar setae with thin tip. Segment 9 with acrothek consisting of small aestetasc and two setae. Armature formula: 1-[1],2-[10],3-[8],4-[2],5-[6+(1+ae)],6-[2],7-[2+2 modified],8-[1+3 modified],9-[8+acr].

P2 ( Fig. 9A View FIGURE 9 ) almost like P 2 female. Differences in shape of distal segments of endopod and exopod, in shape of intercoxal sclerite and length of endopodal setae.

P3 ( Fig. 9B View FIGURE 9 ). Praecoxa, coxa, basis, first endopodal segment and segments 1–2 of exopod as in female. Distal exopodal segment shorter, inner setae with very close bases. Distal endopodal segment modified; outer seta curve and wide, transformed into apophysis and shifted on front side. One of apical setae fused at base with segment.

P4 ( Fig. 9C View FIGURE 9 ) differs from P 4 female only in shape of distal segments of endopod, exopod and intercoxal sclerite. Also first segment of endopod without row of spinules.

P5 ( Fig. 8B View FIGURE 8 ) with left and right baseoendopods fused medially; baseoendopod with two rows of spinules, two tube pores, with one outer naked seta and three endopodal pinnate setae. Exopod short (length/width ratio 1.7) with spinules on inner, outer and distal margin; with inner pectinate seta, two apical pinnate setae and two outer naked setae.

Variability. P2 of one female without inner seta.

Ecology. Probably, like most of the other harpacticoids found in washings from sponges, H. spongiophilus sp. nov. is not an obligate inhabitant of sponges. The shape of the mouthparts and swimming legs does not have any modifications and is similar to those of other species of the genus. Sponges for this species are most likely a convenient place in terms of food and shelter. H. spongiophilus sp. nov. most likely has the same diet as H. pseudonunni Coull & Palmer, 1980 . Preferred feeding on detritus and bacteria is described for this species ( Ustach, 1982).

Remarks. Together with the new species, the genus Heteropsyllus has 16 species and subspecies. According to our and published data, representatives of the genus are typical components of the seas of the Arctic Basin ( Chertoprud et al. 2018, Garlitska et al. 2019). Within the genus, the described species are rather well distinguished. The new species has a unique combination of morphological features. Apparently, the closest species is H. coulli Kornev & Chertoprud, 2008 . In general, both species have a set of traits plesiomorphic for the genus, especially in the armament of P2-P4 endopods. However, they are brought together by the reduction of the inner seta of the distal segment of the P1 endopod; both species also have a similar structure of mouthparts and P5. They differ well in the number of setae on P2 endopod of females, where H. coulli has six setae and H. spongiophilus sp. nov. has five setae.