Lepeophtheirus robertae, Boxshall, 2018

Boxshall, Geoff, 2018, The sea lice (Copepoda: Caligidae) of Moreton Bay (Queensland, Australia), with descriptions of thirteen new species, Zootaxa 4398 (1), pp. 1-172 : 146-153

Lepeophtheirus robertae sp. nov.

( Figs. 69–71 )

Type material. Holotype ♀, allotype ♂ from Scarus ghobban Forsskål, 1775 (TC 16968) 11 January 2016, QM Reg. Nos Holotype ♀ W53125, allotype ♂ W53126.

Type Host. Scarus ghobban Forsskål, 1775 .

Site on host. Body surface.

Etymology. The new species is named for my wife, Roberta, in recognition of her support and her skills as an illustrator of copepods (e.g. in Boxshall & Montú, 1998).

Description. Holotype adult female ( Fig. 69A ) body length including caudal rami 2.71 mm. Cephalothorax subcircular (length 2.18 x width 2.20 mm), comprising about 80% of total body length. Free margin of thoracic portion of dorsal cephalothoracic shield extending posteriorly well beyond rear margins of lateral portions and overlapping anterior half of genital complex. Frontal plates without lunules. Genital complex incorporating fused fourth pedigerous somite; extremely broad (1.07 mm) but short (0.50 mm); with rounded anterolateral corners, convex lateral margins and linear posterior margin bearing prominent spiniform fifth legs ( Fig. 69B ) extending beyond tips of caudal rami. Copulatory pores located near midline, oviduct openings marked by swellings. Genital complex about 2.5 times longer than abdomen. Abdomen 1-segmented; about 1.3 times wider than long (0.21 x 0.17 mm) in ventral view ( Fig. 69B ); carrying paired caudal rami distally; anal slit terminal. Caudal rami with parallel sides, about 2.3 times longer than wide (153 µm x 67 µm). Each ramus armed with short hirsute seta at inner distal angle, two short hirsute setae at outer distal angle, and 3 long plumose setae on distal margin.

Antennule ( Fig. 69C ) 2-segmented; large proximal segment with 25 plumose setae arrayed along anteroventral surface and 2 setae located dorsally; distal segment bearing 12 elements (10 setae plus 2 aesthetascs) around apex, plus isolated seta on posterior margin. Antenna ( Fig. 69D ) comprising proximal segment bearing spatulate posteriorly-directed spinous process; middle segment subrectangular, tapering slightly distally, unarmed; terminal segment forming recurved claw bearing weak swelling proximally, and slender seta near anterior margin. Postantennal process robust, weakly curved; ornamented with 2 multisensillate papillae on basal part and single similar multisensillate papilla on adjacent ventral cephalothoracic surface.

Mandible of typical stylet-like structure, with 12 marginal teeth. Maxillule ( Fig. 69D ) comprising anterior papilla bearing 3 unequal, tiny naked setae and bifid posterior process, inner tine more slender than outer. Maxilla 2-segmented, comprising elongate syncoxa and basis: syncoxa unarmed; basis ( Fig. 70A ) bearing membranous flabellum on anterior margin, and terminating in 2 claw-like elements (calamus and canna). Calamus longer than canna, both ornamented with strips of serrated membrane. Maxilliped subchelate ( Fig. 70B ); proximal segment with small rounded process on myxal surface; distal subchela short, with apical claw separated from proximal segmental part by incomplete suture; armed with slender seta on concave margin.

Sternal furca ( Fig. 70C ) with short, broad divergent tines, with bluntly rounded tips.

First swimming leg pair ( Fig. 70D ) with joined by slender intercoxal sclerite; sympod with inner and outer plumose setae derived from basis; endopod represented by unarmed process on posterior margin of basis. Exopod 2-segmented; directed laterally and forming main axis of leg; first segment armed with small outer (anterior) spine and ornamented with row of setules along middle section of posterior margin; second segment armed with 3 short plumose setae along posterior margin and 4 distal elements along distal margin. Distal elements as follows: spine 1 (anterior-most) robust and slightly curved with minute serrations along concave margin, longer than spine 2; spine 2 markedly longer than spine 3, each with accessory process and with strip of serrated membrane distally; seta 4 shorter than spine 3, naked, and shorter than segment.

Second leg ( Fig. 70E ) biramous, with flattened protopodal segments and 3-segmented rami. Coxae of leg pair joined by transversely elongate intercoxal sclerite bearing marginal membrane posteriorly. Coxa with plumose seta and surface sensilla. Basis armed with outer naked seta; ornamented with surface sensilla, marginal membrane posteriorly, and flap of membrane anteriorly, reflexed back over dorsal surface of segment. Exopodal segment 1 with bilaterally serrate outer spine and inner plumose seta, ornamented with flap of membrane anteriorly reflexed back across dorsal surface of ramus; segment 2 with outer spine and inner seta; segment 3 with bilaterally serrate proximal spine and curved distal spine ornamented with membrane laterally; apical spine with marginal membrane laterally and pinnules medially, and 5 inner plumose setae. First and second endopodal segments armed with 1 and 2 inner plumose setae, respectively; segment 3 with 6 plumose setae; outer margins of all endopodal segments ornamented with fine setules.

Third leg pair ( Fig. 70F ) forming large flattened plate closing posterior part of cephalothoracic sucker. Protopodal part flattened joined by plate-like, intercoxal sclerite forming apron, ornamented with marginal membrane posteriorly and along lateral margin anterior to exopod; bearing inner plumose seta at junction with intercoxal plate, and outer plumose seta dorsally near base of exopod; sensillae located adjacent to inner coxal seta and adjacent to origin of endopod; rami originating close together. Exopod 2-segmented; first segment ( Fig. 70H ) almost circular, armed with short claw directed over ventral surface of ramus; outer distal margin of segment ornamented with strip of membrane and 2 long sensillae present on ventral surface of segment; compound distal segment ( Fig. 70I ), with partial suture marking plane of fusion of former segments; armed with 4 spines and single plumose seta along outer margin. Endopod 2-segmented ( Fig. 70G ); first segment with weakly expanded lateral margin, forming rudimentary velum ornamented with spinules along free margin, armed with inner plumose seta; distal segment with 4 plumose setae.

Fourth leg ( Fig. 71A ) 4-segmented, comprising slender protopodal segment and elongate 3-segmented exopod: protopodal segment with smooth outer margin armed with plumose seta distally; first exopodal segment armed with slender minute outer distal spine with pecten at base; second segment with curved outer distal spine with pecten at base; third with 2 long apical spines ornamented with membrane plus shorter curved subapical spine; all spines with pecten at base.

Fifth legs developed as conspicuous tapering posterior processes originating posterolaterally on genital complex ( Fig. 69B ); each fifth leg comprising anterior seta located on surface of genital complex just lateral to base of tapering process; process representing exopod about 0.45 mm long, armed with long apical plumose seta and 2 subapical setae.

Allotype male ( Fig. 71B ) body length 1.85 mm including caudal rami. Cephalothorax subcircular as in female (length 1.59 mm x width 1.53 mm). Fourth pedigerous somite incompletely fused to genital complex and concealed in dorsal view beneath thoracic zone of dorsal cephalothoracic shield. Genital complex about 1.3 times wider than long (0.34 x 0.26 mm), measured along mid-line; with parallel lateral margins. Abdomen short, 1-segmented, separated from genital complex dorsally but fused ventrally ( Fig. 71C ); carrying paired caudal rami distally; anal slit terminal. Caudal rami broad, with convex distal margin twice as wide as base; armed with short plumose seta at inner distal angle, 2 short plumose setae at outer distal angle, and 3 longer plumose setae on distal margin.

Antennule, mandible, maxillule and maxilla as in female. Antenna modified ( Fig. 71D ); first segment elongate; second segment reflexed, swollen proximally with surface forming corrugated adhesion pads ventrally, plus dorsal pad in distal part; distal segment forming short powerful apical claw, plus accessory claw and armed with 2 setae proximally.

Maxilliped ( Fig. 71E ) with rounded myxal process on proximal segment; distal subchela longer relative to syncoxa than in female.

Legs 5 and 6 ( Fig. 71C ) each forming paired conical processes on posterior margin of genital complex. Each leg 5 represented by posterolateral process armed with 1 plumose seta at base, 1 long plumose seta on apex, and 2 subapically. Each leg 6 represented by oblique operculum closing off paired genital aperture and terminating in process armed with 3 short naked setae around apex.

Not clear from description of Kirtisinghe (1937).

Remarks. The extreme development of the fifth leg of the female is shared with a cluster of seven species within Lepeophtheirus , most of which were formerly placed in a separate genus, Dentigryps (see Lewis, 1964b). However, Dentigryps is no longer regarded as valid (see Dojiri & Ho (2013) for a summary of the taxonomic history of this genus) so these seven species are now considered as belonging to Lepeophtheirus as: L. bifurcatus (Lewis, 1964) , L. curtus ( Wilson, 1913) , L. lichiae Barnard, 1948 , L. litus (Lewis, 1964) , L. longicauda (Cressey, 1966) , L. spinifer Kirtisinghe, 1937 , and L. ulua (Lewis, 1964) . Only two of these, L. litus and L. ulua , have previously been reported from Australian waters (Kabata, 1965a; Ho & Dojiri, 1977). Characteristics of these seven species, together with the new species, are summarised in Table 8.

A dichotomous key to females can be constructed using these character states ( Table 8) plus a few supplementary features:

1 Genital complex less than 1.5 times wider than long; genital complex with posterolateral lobes carrying fifth legs......... 2

- Genital complex more than 1.8 times wider than long; posterolateral lobes usually absent, sometimes present (in L. longi- cauda) .............................................................................................. 4

2 Adult body length about 4.0 mm; genital complex 1.4 times wider than long................................ L. spinifer

- Adult body length about 6.0 to 7.5 mm; genital complex 1.1 times wider than long.................................. 3

3 Abdomen 2-segmented; tip of fifth legs not reaching distal margin of caudal rami............................ L. lichiae

- Abdomen 1-segmented; tip of fifth legs extending well beyond distal margin of caudal rami..................... L. ulua

4 Genital complex with posterolateral lobes carrying fifth legs; caudal rami about 4.0 times longer than wide.... L. longicauda

- Genital complex without posterolateral lobes; caudal rami less than 2.5 times longer than wide........................ 5

5 Leg 3 with 3-segmented exopod with setal formula I-0; I-1; III,4....................................... L. bifurcatus

- Leg 3 with 2-segmented exopod (ancestral second and third segments fused) with IV spines plus either 1 or 5 setae on com- pound distal segment.................................................................................. 6

6 Compound distal segment of leg 3 with 5 setae.............................................................. 7

- Compound distal segment of leg 3 with 1 seta................................................ L. robertae sp. nov.

7 Proximal (protopodal) segment of leg 4 with spiniform process near middle of outer margin..................... L. litus

- Proximal (protopodal) segment of leg 4 without process on outer margin.................................... L. curtus

The new species shares a number of fine scale features with L. longicauda ; for example, both species are ornamented with 2 conspicuous sensillae on the surface of the first exopodal segment of leg 3. Both have reduced setation on the compound distal segment of the exopod of leg 3, however, L. longicauda has a total of 4 spines and 3 setae (Cressey, 1966), whereas the new species has 4 spines but only a single seta ( Fig. 70I ). The endopod of leg 3 is reduced to a single unarmed segment in L. longicauda whereas it is 2-segmented and has 0-1, 4 setation in the new species. This species brings to 12 the total number of species of Lepeophtheirus known from Australian waters.

Figures

FIGURE 69. Lepeophtheirus robertae sp. nov., holotype female. A, habitus, dorsal; B, genital complex, incorporating fourth pedigerous somite, and abdomen, ventral; C, antennule; D, antenna, post-antennal process and maxillule drawn in situ. Scale bars:1.0 mm on A, 0.5mm on B,100 µm on C, D.

FIGURE 70. Lepeophtheirus robertae sp. nov., holotype female. A, brachium of maxilla; B, maxilliped; C, sternal furca; D, leg 1, ventral; E, leg 2, ventral; F, leg 3, ventral; G, endopod of leg 3; H, first exopodal segment of leg 3, I, second exopodal segment of leg 3. Scale bars:200 µm on A–F, 100 µm on G–I.

FIGURE 71. Lepeophtheirus robertae sp. nov., holotype female. A, leg 4. Allotype male, B. habitus, dorsal; C, fourth pedigerous somite, genital complex and abdomen, ventral; D, antenna; E, maxilliped. Scale bars: 200 µm on A, C, E, 1.0 mm on B, 100 µm on D.