Bryocamptus (Bryocamptus) minutus minutus (Claus, 1863)

Novikov, Aleksandr, Sharafutdinova, Dayana & Chertoprud, Elena, 2023, Two new species of Bryocamptus (Copepoda, Harpacticoida, Canthocamptidae) from the Russian Arctic and comparison with Bryocamptus minutus (Claus, 1863), ZooKeys 1138, pp. 89-141 : 89

Bryocamptus (Bryocamptus) minutus minutus (Claus, 1863)

Figs 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9

B. (B.) minutus vejdovskyiformis Thallwitz, 1916: 238. syn. nov.

Material examined.

Estonia • 2 ♀♀ dissected on three slides (BP 546/1-a, BP 546/1-b, BP 546/2) ; 1 ♂ on one slide (BP 546/3); 9 ♀♀ and 5 ♂♂ undissected preserved in 4% formalin (retained in the collection of the first author); Vortsjaerv Lake ; 58.180888°N, 26.089441°E; 25 Sep. 2007; E. Fefilova leg; BP 546 .

Supplementary description.

Female. Body subcylindrical. Total body length from anterior margin of rostrum to posterior margin of caudal rami: 484 µm (n = 1). Cephalothorax (Fig. 1A, B ; Appendix 1) wider than remaining somites, length 151 µm, largest width 124 µm. Naupliar eye not observed. Rostrum (Fig. 1C ) small, fused with cephalothorax, with squared end, with one pair of sensillae. Posterior margin of cephalothorax and all pedigerous somites smooth.

Cephalothorax (Fig. 1A, B ; Appendix 1) with dumbbell-shaped dorsal window, 10 pairs of pores, seven pairs of sensillae of central group (group C), 13 pairs of sensillae of marginal group (group P) and 20 pairs of ungrouped sensillae (in Table 4 and in Appendix 1 marked as L). Second pedigerous somite with lateral windows, dorsal unpaired pore, lateral pair of pores and eight pairs of sensillae. Third pedigerous somite with dorsal unpaired pore, lateral pair of pores and eight pairs of sensillae. Fourth pedigerous somite with dorsal unpaired pore, lateral pair of pores and eight pairs of sensillae. Fifth pedigerous somite with lateral pair of pores and four pairs of sensillae.

Abdomen (Fig. 2A-C ) consisting of genital-double somite, two free abdominal somites and anal somite with caudal rami. All somites except anal somite on posterior margin serrated, on surface with spinular rows. Genital-double somite consists of last thoracic somite and first abdominal somite; longer than wide; anterior part with four pairs of sensillae, dorsal unpaired pore, lateral paired pores, ventro-lateral and lateral rows of spinules; posterior part with four pairs of sensillae, pairs of ventral and lateral pores and lateral rows of spinules.

P6 (Fig. 2C ) fused with somite with one pinnate and one naked setae. Genital field (Fig. 2C ) long, laterally with eight-pore sieves; copulatory pore displaced to posterior part of somite, copulatory duct chitinised with two additional tubes, extending proximally to pair of labyrinthic rounded ducts and one chitinised unpaired duct.

Second abdominal somite with three pairs of sensillae, pair of lateral pores; on posterior margin with lateral row of large spinules. Third abdominal somite with pair of lateral pores, on posterior margin with lateral row of large spinules and ventral row of small spinules. Anal somite with one pair of sensillae, ventral pair of large pores, lateral pair of pores, dorsal dots near base of caudal rami and lateral spinules. Anal operculum semilunar, with eight long bifid spinules.

Caudal rami (Fig. 2A-E ). Length/width ratio 1.6, with three ventral pores; with rows of spinules on ventral side at base of seta IV and rows spinules at base of setae II and III. Seta I small, located near seta II. Setae IV, V and VI displaced to ventral side of caudal ramus. Apical seta IV (Fig. 2D ) unipinnate, with "helle Stelle" and massive dorsal bulb located distally "helle Stelle". Apical seta V long, bipinnate, with "helle Stelle". Seta VII triarticulated (Fig. 2B ).

Antennule (Fig. 1D ) 8-segmented. Segment 1 short, with one pinnate seta and two rows of spinules. Other segments with bare setae. Segment 4 with fused basally seta and aesthetasc. Distal segment with acrothek consisting of aesthetasc and two setae fused basally. Armature formula: 1-[1],2-[9],3-[5],4-[1+(1+ae)],5-[1],6-[3],7-[2],8-[5+acr].

Antenna (Fig. 3A ) with allobasis. Coxa with two rows of spinules. Allobasis with two naked setae and one spinular row at base of endopodal seta. Free endopodal segment with two lateral rows of big spinules, with two spinulose spines and slender seta; distally with two rows of spinules; apically with three geniculate setae, two long spines and one small accessory seta; outermost geniculate seta fused basally to small seta. Exopod two-segmented; first segment with one pinnate seta and row of spinules; second segment with three pinnate setae.

Labrum (Fig. 4A ). On outer side with row of thin setules and large proximal pore. Distal margin with lateral rows of robust spinules, rows of fused spinules into comb and three rows of small spinules. On inner side medially with four unpaired pores, three pared pores, with lateral spinular row, semicircular spinular row and groups of thin setules.

Mandible (Fig. 4B, C ). Coxa with spinules proximally. Gnathobase with pars incisiva, lacinia mobilis, complex dental battery and spinulose seta; pars incisiva two-pointed; lacinia mobilis three-pointed. Dental battery (Fig. 4C ) consisting of five fused blocks of small short teeth, inner of which fused at base with seta. Pars molaris sharply edged. Palp one-segmented, with medial spinular row and four apical setae.

Paragnaths (Fig. 4D ) with paired lateral lobes and unpaired posterior rounded lobe. Lateral lobes wrapped in distal part forming “pocket”; proximally with lateral pore (probably); on outer side with four groups of long spinules; on inner side with three-four rows of spinules; on anterior side with three medial rows of strong spinules and proximal row of spinules.

Maxillule (Fig. 3B ). Praecoxa with two rows of slender spinules on outer edge and one row of spinules on posterior side. Praecoxal arthrite medially with two rows of spinules and one proximal pore; distally with one simple strong spine, three strong spines with pectinate end, three biarticulate spines, one proximal bipinnate seta and one thin seta with long spinules. Coxa with row of spinules, coxal endite with one weakly pinnate and one spinulose geniculate setae. Basis with two subdistal setae and three distal setae, one of which spinulose and geniculate. Endopod and exopod incorporated into basis, each represented by two naked setae.

Maxilla (Fig. 3C ). Basis with several rows of spinules on outer and inner edge as figured, with two endites. Proximal endite with spinular row, one spinulose spine and two pinnate setae, distal endite with one strong pinnate seta and two thin pinnate setae. Proximal endopodal segment with two setae, outer tube pore and massive distal claw. Distal endopodal segment with three naked setae, one of which proximal and small.

Maxilliped (Fig. 5A ) subchelate. Syncoxa elongated with several rows of spinules as figured, distally with one pinnate seta. Basis with two rows of large spinules on anterior and posterior sides and three outer rows of small spinules. Endopod on posterior side with one seta, on anterior side with small protuberance, probably tube pore. Endopodal claw elongated, with row of small spinules.

Cuticular process between maxillipeds and P1 (Fig. 4E, F ) in height approximately same as in length, with long spinules, ten spinules on each side. Spinules encircle from anterior-lateral margin to posterior margin.

P1 (Fig. 5B ; Table 1 ) with three-segmented rami. Praecoxa with outer spinular row. Coxa rectangular, with seven spinular rows, four of which consisting of little spinules. Intercoxal sclerite wide, with one paired spinular rows. Basis with proximal pore, medial row of small spinules, rows of spinules at base of endopod and exopod, row of spinules at base of inner seta, inner row of spinules; with inner and outer strong spines. All endopodal and exopodal segments with outer spinules. First exopodal segment with one outer spinulose spine; second segment with inner pectinate seta and outer spinulose spine; third exopodal segment with two outer spinulose spines and two apical slender geniculate setae. Endopod longer than exopod. First endopodal segment reaching middle of second exopodal segment, with inner pectinate seta and inner spinular row; second endopodal segments with one inner pectinate seta, third segment with outer spinulose spine, apical long geniculate seta and inner small seta.

P2 (Fig. 6A ; Table 1 ). Praecoxa with row of spinules. Coxa with one lateral row of large spinules and five rows of spinules on anterior side. Intercoxal sclerite with two large spinules. Basis with proximal pore, rows of spinules at base of endopod and exopod; with outer spine. All endopodal and exopodal segments with outer spinules. Exopod three-segmented; first exopodal segment with outer naked spine, apically with frill; second segment with outer naked spine, inner pectinate seta, inner slender spinules and apical frill; third segment with pore, three outer spinulose spines, two apical setae and one inner pectinate seta. Endopod three-segmented; first and second segments with inner seta; third segment with outer spinulose spine, two apical pinnate setae and one inner pectinate seta.

P3 (Fig. 6B ; Table 1 ). Praecoxa with spinular row. Coxa with one lateral row of large spinules and five rows of spinules on anterior side. Intercoxal sclerite without spinules. Basis with outer seta, proximal pore, rows of spinules at base of endopod and exopod. Exopod three-segmented; first exopodal segment with outer naked spine, outer spinules, apically with frill; second segment with outer naked spine, outer spinules, inner pectinate seta, inner slender spinules and apical frill; third segment with pore, three outer spinulose spines, two apical setae and two inner pectinate setae. Endopod three-segmented; first and second segments with inner seta, second segment with outer spinules; third segment with outer spinules, outer spinulose spine, two apical pinnate setae and two inner pectinate setae.

P4 (Fig. 6C ; Table 1 ). Praecoxa with spinular row. Coxa with one lateral row of large spinules and five rows of spinules on anterior side. Intercoxal sclerite without spinules. Basis with outer seta, proximal pore, rows of spinules at base of endopod and exopod. Exopod three-segmented; first exopodal segment with outer naked spine, outer spinules, apically with frill; second segment with outer naked spine, outer spinules, inner pectinate seta, inner slender spinules and apical frill; third segment with pore, two outer spinulose spines, two apical setae and two inner pectinate setae. Endopod two-segmented; first segment with inner seta, second segment with outer spinules, outer spinulose spine, two apical pinnate setae and two inner pectinate setae.

P5 (Fig. 5C ) with separate right and left baseoendopods. Baseoendopod reaching ~ 1/2 of exopodal segment; with four pores, spinular row at base of outer seta; outer seta of basis pinnate, long. Endopodal lobe with four long bipinnate setae and two short bipinnate setae V and VI; with small process that may be pore between setae III and IV. Exopod with inner short pinnate seta, long apical pinnate seta, naked subapical seta and two pinnate outer setae.

Male. Sexual dimorphism expressed in the antennule, P2-P6, genital segmentation and ornamentation, shape of caudal rami. Cephalothorax and thoracic somites as in female. P6 (Fig. 7B ) two asymmetric flaps fused to the somite, with three naked setae. Differences from female in abdomen structure as follows (Fig. 7A, B ): first abdominal somite free; first to third abdominal somites with spinular row encircling somite ventrally and laterally; anal somite with ventral spinules; caudal rami with normal setae IV and V; anal operculum with nine bifid and simple spinules.

Antennule (Fig. 8A, B ) 10-segmented, haplocer with geniculation between segments 7 and 8. Segment 5 with large aestetasc fused at base with long seta, with one strong caudate seta. Segment 7 with articular plate, with one filiform seta, one small caudate seta and with two modified laminar setae. Segment 8 with proximal dentate plate and two strong modified laminar setae. Segment 10 with acrothek consisting of slender aestetasc and two setae. Armature formula: 1-[1],2-[9],3-[8],4-[2],5-[6+(1+ae)],6-[2],7-[2+2 modified],8-[2 modified],9-[1],10-[7+acr].

P2 (Fig. 9A ) as in female, except endopod. Endopod two-segmented. First segment with outer spinules and inner seta. Second segment with notch on distal outer margin, outer spinules, two apical pinnate slender setae and two inner pectinate setae.

P3 (Figs 8C, D , 9B ): praecoxa, coxa, intercoxal sclerite as in female. Basis as in female, but with inner process. Exopod as in female, but third segment with broad slit-like pore. Endopod three-segmented. First endopodal segment with strong seta. Second endopodal segment with posterior seta and long apophysis with double tip. Third segment with two small inner setae, inner pore and two apical pinnate setae.

P4 (Fig. 9C ): praecoxa, coxa, intercoxal sclerite, basis, exopod as in female. Endopod two-segmented; first segment short unarmed; second segment with outer spinules, spinulose spine, outer apical spiniform spinulose seta, inner apical bipinnate seta and inner pectinate seta.

P5 (Fig. 7C ) right and left fused medially. Baseoendopod with three pairs of pores, outer spinular row and outer long pinnate seta; endopodal lobe with two strong spinulose apical spines. Exopod with spinules on anterior surface, three naked outer setae, long apical spinulose seta, one inner spinulose seta and one long inner pectinate seta with long setules.

Variability.

We found variability in the structure of the caudal rami. Some females have an inner group of long spinules (Fig. 2E ).

Figures

Figure 1. Bryocamptus minutus, female A cephalothorax and thoracic somites, dorsal B cephalothorax and thoracic somites, lateral C rostrum D antennule. Scale bars: 50 µm (A, B); 5 µm (C); 25 µm (D).

Figure 2. Bryocamptus minutus, female A abdomen, dorsal B abdomen, lateral C abdomen, ventral D caudal setae, dorsal E abnormal caudal ramus, dorsal. Scale bar: 50 µm.

Figure 3. Bryocamptus minutus, female A antenna B maxillule C maxilla. Scale bars: 10 µm.

Figure 4. Bryocamptus minutus, female A labrum, posterior (black dots is bases of spinules) B mandible C scheme of teeth of mandibular gnathobase D paragnaths, anterior E cuticular process between maxillipeds and P 1, ventral F cuticular process between maxillipeds and P 1, lateral. Scale bars: 10 µm (A, B, D); 5 µm (C, E, F).

Figure 5. Bryocamptus minutus, female A maxilliped B P 1, anterior C P 5, anterior. Scale bars: 10 µm (A); 25 µm (B, C).

Figure 6. Bryocamptus minutus, female A P 2, anterior B P 3, anterior C P 4, anterior. Scale bar: 25 µm.

Figure 7. Bryocamptus minutus, male A abdomen, dorsal B abdomen, ventral C P 5, anterior. Scale bars: 50 µm (A, B); 10 µm (C).

Figure 8. Bryocamptus minutus, male A antennule, anterior B antennule, dorsal C P 3 endopod, anterior D P 3 endopod, inner view. Scale bars: 10 µm.

Figure 9. Bryocamptus minutus, male A P 2, anterior B P 3, anterior C P 4, anterior. Scale bar: 25 µm.