Laophontodes typicus T. Scott, 1894

George, Kai Horst, 2018, Laophontodes typicus T. Scott (Copepoda, Harpacticoida, Laophontodinae) - discovering a species complex by morphology, European Journal of Taxonomy 439, pp. 1-43 : 4-12

Redescription of Laophontodes typicus T. Scott, 1894

Figs 2–6

Locus typicus

UNITED KINGDOM: Scottish Firth of Forth, “Vicinity of Inchkeith” ( T. Scott 1894: 250).

Type material

Not available anymore.

Material examined (no types)

UNITED KINGDOM: 35 ♀♀, 11 ♂♂, Sussex coast (eastern English Channel), Whirlpool Hole, 50°41.40′ N, 00°48.85′ W, 19.6 m depth, 7 Sep. 1997, Dr David Ventham leg., preserved in ethanol ( BMNH 2015.1144–1153 ) (for detailed sampling data see Ventham 2011: 35).

For the redescription, 2 ♀♀ were dissected and distributed over 4 and 5 slides, respectively, embedded in glycerol. Additionally, 2 ♂♂ were each mounted on 1 slide, but subsequently returned into ethanol.

Description

Female

HABITUS ( Fig. 2A–B ). Cylindrical, tapering distally, body length (R to end of FR) 388 µm. Cphth slightly longer than broad, representing 25% of body length. R ( Figs 2A , 3A ) small, fused to cphth, with 2 sensilla on apical margin. Body somites clearly distinct. Posterior margins of thoracic somites serrated dorsally, with sensilla arising from small socles and with 1 tube pore centrally; P2–P4-bearing somites additionally with fine ripples running anteriorly. Last thoracic and first abdominal somites fused to form genital double somite, juncture detectable by dorsal serration and constricted outer margins. Abdominal part of GDS and following two abdominal somites dorsally strongly serrated. Penultimate somite without sensilla but with pair of tube pores. Telson slightly smaller than preceding somite, with FR widely separated proximally. Anal operculum with spinules of moderate length on apical margin.

FURCAL RAMI ( Fig. 2A–C ). Slender, about 6 times longer than its broadest part, proximally with tube pore and with 7 bare setae: I and II of almost same length, arising centrally from outer margin; III subapical on dorsal side; IV and V apical, IV very narrow and less than half of the length of V; VI apical on inner margin, as long as I–III; VII slightly longer than IV, dorsal, arising from pedestal, tri-articulated at base.

ANTENNULE ( Fig. 3A –A’). 5-segmented. First segment ( Fig. 3A ) carrying 1 bipinnate seta and a row of spinules around apical edge; second segment (marked with * in Fig. 3A –A’) with spinulose bump at posterior margin and 9 bare setae; third segment as long as second, with 7 bare setae and 1 aes; fourth segment smallest, partially overlapped by preceding segment, with 1 bare seta; fifth segment with 9 bare setae, 6 of which bi-articulated at base; apically with small aes and 2 additional setae forming a trithek.

SETAL FORMULA. 1-1/2-9/3-7+aes/4-1/5-11+aes.

ANTENNA ( Fig. 3B ). Allobasis lacking abexopodal seta but with abexopodal row of spinules. Exp represented by 1 bare seta. Enp shorter than allobasis, with row of subapical spinules, row of anterior spinules, 2 bipinnate anterior setae and 5 bare apical setae, of which 4 geniculated.

MANDIBLE ( Fig. 4A ). With slender gnathobase bearing 5 teeth; palp 1-segmented, with 4 lateral setae (1 bipinnate) and 1 bipinnate terminal seta.

MAXILLULE ( Fig. 4B ). Praecoxal arthrite distinct, with 7 strong bare spines, of which two bi-articulated, 1 subapical seta and 2 additional surface setae. Coxa without spinules, 2 bare setae terminally. Basis without spinules, 3 bare setae terminally, and 1 bare seta medially between the enp and the basal endite. Exp and enp represented by 1 and 2 bare setae, respectively.

MAXILLA ( Fig. 4C ). Damaged; all setae broken. Syncoxa bearing 3 rows of spinules and 2 endites. Proximal endite with 2 bare setae (broken in Fig. 3C ); setation of distal endite not discernible. Basis distinct, produced into strong claw (?), with 1 seta (broken in Fig. 3C ). Enp small; with 2 bare setae (both broken in Fig. 3C ).

MAXILLIPED ( Fig. 4D ). Prehensile; syncoxa slightly shorter than basis, with spinules and 1 bipinnate seta distally. Basis with long spinules along inner margin and subapically. Enp transformed into claw, nearly same length as basis; if accompanying minute seta present, not discernible.

SWIMMING LEGS. P1 (Fig. 5A) with square coxa; basis slightly longer than coxa, with 1 bipinnate outer seta and 1 uniplumose seta displaced to anterior surface. Enp 2-segmented, enp-1 strong and elongated, with row of spinules on outer and inner margins; enp-2 small, ⅓ length of enp-1, apically with 1 claw and 1 slender geniculated bare seta, subapically with 1 small seta. Exp 3-segmented, reaching more than half the length of enp-1. Exp-1 with 1 uniplumose outer seta; exp-2 with outer row of spinules and 1 bare geniculated outer seta; exp-3 apically with 4 long bare geniculated setae. P2–P4 (Fig. 5B–D) with transversely elongated bases, 3-segmented exopods and 2-segmented endopods. Exp-3 longest segment, all segments with row of spinules on outer margins. Exp-1 and exp-2 without inner seta but with 1 bipinnate outer spine; Exp-3 with 1 bare inner seta and 3 outer spines; P2 exp-3 apically with 1 biplumose outer seta and 1 bare inner seta; P3 and P4 exp-3 with 2 biplumose apical setae. P2–P4 enp-1 small, without setae. P2 enp-2 elongated, with 2 biplumose apical setae; P3 and P4 enp-2 as in P2 with additional bare inner seta, which is comparatively small in P4. P5 ( Fig. 4E ) benp represented by 2 setae, one biplumose and one of fish-bone aspect, accompanied by 2 tube pores. Benp on outer apical margin with long setophore surrounded by long spinules, bearing 1 bare seta. Exp fused to benp, slender, with 2 outer setae, one of which bare, the other biplumose, 1 biplumose subapical and 2 apical setae, one bare, the other biplumose.

GENITAL FIELD ( Fig. 3C ). With single gonopore; P6 strongly reduced, limbs fused as small single plate, with pair of small bare spines.

Male

The male differs from the female in the following characters: body size, A1, P3 endopod, P5.

HABITUS ( Fig. 6A ). As in female, but slightly smaller and narrower (body length of described specimen from rostral tip to end of FR: 337 µm); no GDS.

ANTENNULE ( Fig. 6B –B’). 6-segmented, chirocer. First segment as broad as long, apically with row of spinules and 1 bipinnate seta; second segment with spinulose bump along posterior margin, several spinules on inner proximal part and 8 bare setae; third segment small, with 4 bare setae; fourth segment smallest, with 1 seta; fifth segment slightly swollen, with 6 bare setae and 1 cuspidate spine on its ventral

Fig. 5. Laophontodes typicus T. Scott, 1894 , ♀ (BMNH 2015.1144–1153-1). A. P1. B. P2. C. P3. D. P4. Scale bar = 50 µm.

surface (Fig. 5B’), and apically with 2 long bare setae and 1 aes accompanied by 1 bare seta on pedestal (Fig. 5B’); sixth segment with 9 bare setae (1 seta broken in Fig. 6B ), and 1 aes arising together with 2 bare setae to form an apical trithek.

SETAL FORMULA. 1-1/2-8/3-4/4-1/5-10+aes/6-11+aes.

SWIMMING LEGS. P3 ( Fig. 6C ) exp as in female. Enp 3-segmented: Enp-1 small and unarmed; enp-2 longest, without setae but with thorn-like, slightly curved apophysis on inner apical margin; enp-3 not reaching end of enp-2 apophysis, with 2 biplumose apical setae. P5 ( Fig. 4F ) small, benp and exp fused. Benp with outer basal seta arising from setophore. Endopodal lobe represented by 1 biplumose seta. Exp short, with 1 bipinnate outer seta and 2 bipinnate apical setae; no tube pores discernible.

Figures

Fig. 2. Laophontodes typicus T. Scott, 1894. A–C. Habitus ♀ (BMNH 2015.1144–1153-1). A. Dorsal view. B. Lateral view. C. Left furcal ramus, dorsal view. Scale bars: A–B = 100 µm, C = 50 µm.

Fig. 3. Laophontodes typicus T. Scott, 1894, ♀ (A–B: BMNH 2015.1144–1153-1; A', C: BMNH 2015.1144–1153-3). A. Rostrum, first and second segment of A1. A’. Second to fifth segments of A1. Asterisk (*) showing second segment. B. A2. C. Genital double somite with genital field and P6. Scale bar = 50 µm.

Fig. 4. Laophontodes typicus T. Scott, 1894, A–E. ♀ (A–D: BMNH 2015.1144–1153-1; E: BMNH 2015.1144–1153-3). A. Md B. Mxl. C. Mx. D. Mxp. E. P5. F. ♂ (BMNH 2015.1144–1153-2), P5. Scale bar = 50 µm.

Fig. 6. Laophontodes typicus T. Scott, 1894, ♂ (A: BMNH 2015.1144–1153-2; B–C: BMNH 2015.1144– 1153-4). A. Habitus, dorsal view. B. A1. B’. Fifth segment of A1 showing setation. C. P3 enp. Scale bar: A = 100 µm, B–C = 50 µm.