Spongiopsyllus intermedius, Borges & Farias & Mácola & Neves & Son, 2021

Borges, Camila, Farias, Amilcar, Mácola, Rosa, Neves, Elizabeth G. & Son, Rodrigo Johns-, 2021, A new Entomolepididae genus and a new species of Spongiopsyllus Johnsson, 2000 (Copepoda, Siphonostomatoida) and their association with Aplysina Nardo, 1834 (Porifera, Demospongiae) in Todos-os-Santos Bay, Bahia, Brazil, Zootaxa 4981 (2), pp. 301-316 : 307-312

Spongiopsyllus intermedius sp. nov.

( Figs 4–6 )

lsid:zoobank.org:act: 5B344D20-F69F-4202-96B1-45B275CF5379

Material examined. Holotype female ( UFBA 3185 ) and paratype female ( UFBA 3186 ) associated with Aplysina solangeae , at 3 m depth at Porto da Barra Beach , Salvador, Bahia, Brazil, collected by C. Borges, R. Johnsson and E. G. Neves in 9th October, 2014.

Description of female.

Mean body length (excluding caudal setae) 1065 µm and mean body width 775 µm. Body shield flattened ( Fig. 4a ), with radiating bands along outer margin. Pedigerous somites 2–4 free. Urosome ( Fig. 4b ) four-segmented. Genital double-somite fused with fifth pedigerous somite, 237 × 147 µm; length: width ratio 1.6:1. Genital openings near insertion of leg 5. All three postgenital somites wider than long, 52 × 65, 23 × 58 and 42 × 54 µm, respectively. Length prosome: urosome ratio = 1.4:1. Caudal rami elongate, 115 µm long, armed with 6 plumose setae distally.

Antennule ( Fig. 4c ) slender, 257 µm long (not including setae), and 16-segmented. Length of segments: 58, 23, 27, 8, 11, 15, 12, 10, 10, 12, 10, 10, 12, 12, 10 and 17 µm, respectively. Segmental homologies and setation as follows: 1(I)–2; 2(II– III)–2; 3(IV–VI)–6; 4(VII)–2; 5(VIII)–2; 6(IX–XIII)–5; 7(XIV)–2; 8(XV)–2; 9(XVI)–2; 10(XVII)–2; 11(XVIII)–2; 12(XIX)–2; 13(XX)–2; 14(XXI)–2+ae; 15(XXII)–2; 16(XXIII–XXVIII)–6. Aesthetasc 107 µm long.Antenna ( Fig. 4d ) 187 µm long (including distal claw); basis 67 µm long. Exopod 1-segmented, 48 µm long, and with two unequal, sub-distal setae and five small setules along lateral margin. Endopod 2-segmented; first segment 52 µm long, with six setules on inner margin; second segment 20 µm long, ornamented with row of long setules along outer margin, and armed with 2 naked setae and terminal narrow claw, slightly curved distally.

Oral cone 956 µm long, reaching anal somite. Mandible ( Fig. 5a ) comprising stylet and slender 2-segmented palp measuring 48 and 57 µm long, respectively. Stylet slender, tapering distally. Palp with second segment ornamented with setules along outer margin and armed with two apical, unequal setae.

Maxillule ( Fig. 5b ) bilobed. Inner lobe 67 µm long, armed with two long apical setae. Outer lobe 46 µm long, ornamented with setules along outer margin and armed with three apical setae. Maxilla ( Fig. 5c ) with syncoxa measuring 174 µm long and curved claw with 137 µm long, armed with minute setule on mid-inner margin.Maxilliped ( Fig. 5d ) 5-segmented, 287 µm long (excluding claw); syncoxa and basis 94 and 110 µm long, respectively, both unarmed. Endopod 3-segmented, 34, 22, 27 µm long, respectively, and bearing single seta on each segment plus curved claw measuring 46 µm long. All setae naked.

NEW NEW Legs 1 to 3 ( Figs. 6a–c ) biramous, with 3-segmented rami. Leg 4 ( Fig. 6d ) with exopod 3-segmented and endopod absent. Armature formula of legs 1 to 4 as follows:

Basis of leg 1 with tooth-like projection on outer margin close to outer seta. Second and third endopodal segments of leg 1 ( Fig. 6a ) prolonged distally into sharp tooth-like process, therefore distal setae of third segment located sub-distally on inner margin. Exopodal spines of leg 1 stout proximally. Second and third endopodal segments of legs 2 and 3 ( Figs. 6 b-c) showing similar prolonged process but reduced in size in comparison with leg 1 and not occupying distal position as in third segment of leg 1. Leg 3 with first endopodal segment with outer margin humpshaped middistally; first and second exopodal segments showing small tooth-like projections close to elements. Basis of leg 4 with projection on outer lateral margin.

Free exopodal segment of leg 5 ( Fig. 4b ) elongated, medially curved, 170 µm long, reaching beyond distal margin of genital double-somite, and armed with 3 plumose setae, 2 distal ones and single seta medially on outer margin.

Male. Unknown.

Etymology. The specific name ‘ intermedius’ means intermediate in Latin, referring to the existence of 16 segments of antennule in the new species. This number of segments is intermediary when compared with the 17-segmented S. adventicius Johnsson, 2000 and the 15-segmented S. redactus Canário et al. 2012 .

Remarks

Spongiopsyllus intermedius sp. nov. has all the characters of the genus Spongiopsyllus such as a body shield covering the urosome, except for the tip of the caudal rami, three postgenital somites, and reduction in the female leg setation ( Johnsson 2000).

The new species has a 16-segmented antennule, differing from S. adventicius , S. redactus and S. atypicus which have 17, 15 and 14 segments, respectively ( Canário et al. 2012, 2019, Johnsson 2000). Consequently, the segmental homologies are different in the three species:

Spongiopsyllus intermedius sp. nov. has the ancestral segments XXII free and, XXIII-XXVIII fused, S. redactus has XXII-XXVIII fused, S. atypicus has XXII-XXIII and XXIV-XXVIII fused, and S. adventicius has XXII and XXIII free, XXIV-XXVIII fused. Also, the new species shows the homologies of the basal segments of the antennule as II-III, IV-VI, VII, IX-XIII as in S. redactus , which is different from S. adventicius that has II, III-V, VI, VII- VIII, IX-XII and S. atypicus that has II, III-VIII, IX-XIII. ( Canário et al. 2012, 2019, Johnsson 2000). Antennule segmentation patterns are built based on model proposed by Huys & Boxshall (1994). The number of setae and key segments such as the one with the aesthetasc provide the cues to trace the homologies and becomes strong characters used in diagnosis of genera and families, not only in Entomolepididae ( Kim 2004, McKinnon 1988) but also in other families such as Asterocheridae ( Conradi & Bandera 2011, Kim 2013) and Artotrogidae ( Eiselt 1965, Kim 2016).

S. intermedius sp. nov. has the endopod of the antenna 2-segmented, as in S. redactus and S. atypicus however differing from S. adventicius , that is 3-segmented ( Canário et al. 2012, 2019; Johnsson 2000). Nevertheless, in the new species the distal endopodal segment shows 2 setae and row of setules along the outer margin while S. adventicius and S. redactus have 3 setae and a naked outer margin, and S atypicus has 4 setae and a margin ornamented with long setules ( Canário et al. 2012, 2019; Johnsson 2000). The exopod of the antenna has 2 unequal apical setae in S. intermedius sp. nov. as in S. redactus , unlike S. adventicius that has 2 equal apical setae and S. atypicus that has a smooth distal seta and seven setules laterally ( Canário et al. 2012, 2019; Johnsson 2000).

The stylet in the new species tapers distally, similarly to S. adventicius but different from S. redactus that has subapical denticulated margin ( Canário et al. 2012, Johnsson 2000). The inner lobe of the maxillule of S. intermeNEW dius sp. nov. is armed with 2 setae, instead of 3 as in S. adventicius and S. redactus , and 4 in S. atypicus ( Canário et al. 2012, 2019; Johnsson 2000). The new species has the endopod of the maxilliped with armature formula 1,1,1, different from S. adventicius , S. atypicus and S. redactus that have 0,2,1; 2,0,1; and 2,1,1, respectively ( Canário et al. 2012, 2019; Johnsson 2000).

Spongiopsyllus intermedius sp. nov. also shows differences in the armature formula of the swimming legs. Coxa of leg 1 has no seta as in S. atypicus and unlike its other congeners that have an inner seta ( Canário et al. 2012, 2019; Johnsson 2000). Basis of legs 3 and 4 with 1-0, while its congeners have no seta, except S. atypicus that has 1-0 on the basis of leg 4 ( Canário et al. 2012, 2019; Johnsson 2000). Third endopodal segment of leg 1 with 6 setae altogether as in S. redactus , unlike S. adventicius and S. atypicus that has 5 setae ( Canário et al. 2012, 2019; Johnsson 2000).

The maxilla is armed with a small setule on inner margin of the claw, the third endopodal segment of leg 2 with seta and spine distally (1, 1+I, 2), the third exopodal segment of leg 3 with distal seta medially (III, 1, 4), and the small tooth-like projections close to the spines of the first and second exopodal segments of P3 are all characters not observed in any of its congeners ( Canário et al. 2012, 2019; Johnsson 2000).

Figures

FIG. 4. Spongiopsyllus intermedius sp. nov., female (UFBA 3144). a) Body in dorsal view; b) urosome; c) antennule; d) antenna. Scale bars: a = 200 µm; b = 100 µm; c–d = 50 µm.

FIG. 5. Spongiopsyllus intermedius sp. nov., female (UFBA 3144). a) Mandible; b) maxillule; c) maxilla; d) detail from the maxilla; e) maxilliped; Scale bars: a–e = 50 µm.

FIG. 6. Spongiopsyllus intermedius sp. nov., female (UFBA 3144). a) P1; b) P2; c) P3; d) P4. Scale bars: a–d = 50 µm.