Paralaophonte Lang 1944, sp. n.

Key to the species of Paralaophonte Lang, 1948 Included species: Paralaophonte pallaresae, sp. n.

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The genus-group name Paralaophonte was first published by Lang (1944) who subdivided the genus in four species-groups and designated a type species for three of them: (1) brevirostris -group (no type designated), (2) perplexa -group (type: Laophonte perplexa T. Scott, 1899), (3) gracilipes -group (type: Laophonte gracilipes Brady, 1910), and (4) karmensis -group (type: Laophonte karmensis Sars, 1911). The artificiality of this system was subsequently exposed by the discovery of “transitionary” species which blurred the boundaries of some of the species groups (e.g. Vervoort 1962); consequently, Lang’s (1944, 1948) subdivision was finally disposed off by Wells (2007). Vervoort (1964) remarked that Paralaophonte Lang, 1944 is an unavailable generic name which was subsequently validated by Lang (1948) by the indication of a type species (Cleta brevirostris Claus, 1863) and the provision of an accompanying generic diagnosis. The authorship and date of this genus should, therefore, be attributed as Paralaophonte Lang, 1948 (Huys 2009b).

According to the latest checklist (Wells 2007), the genus Paralaophonte currently includes 33 valid species and one species incertae sedis (Laophonte lamellipes Nicholls, 1944). Various authors (e.g. Willey 1935; Nicholls 1945; Yeatman 1970; Hamond 1973; Wells and Rao 1987; Wells 2007) have commented on the difficulties in separating the two most widely distributed species, P. brevirostris (Claus, 1863) and P. congenera (Sars, 1908b), and some of them have casted doubt on the validity of this separation. Both species have also been reported to display a great deal of variability in the rostrum, antennule, leg 5 and caudal rami (e.g. Wells and Rao 1987) but it is unclear to what degree this pertains to genuine intra- or interpopulation variability or whether this is a reflection of allopatric or sympatric closely related species (as hinted at by Mielke 1981). The further subdivision of both species in subspecies has also led to taxonomic confusion. For example, Willey’s (1935) variety “ fissirostris ” of P. brevirostris was upgraded to subspecies level by Lang (1965) (and accepted by most subsequent authorities: e.g. Wells et al. 1982; Wells 2007) but allegedly differs from the nominotypical subspecies only in the shape of the rostrum. Given the reported variability in this structure in other species it seems impractical to maintain Willey’s (1935) subspecies at present and hence they are here formally declared invalid. Similarly, P. congenera mediterranea Lang, 1948 appears to be more closely related to P. lacerdai Jakobi, 1953 than to its nominotypical subspecies P. congenera congenera. In fact both taxa can only be separated by subtle differences in the caudal ramus, length of endopodal setae in the female P5 and shape of the endopodal margin in the male P5. Likewise, Paralaophonte pacifica galapagoensis Mielke, 1981 is more similar to P. brevirostris than to its nominotypical subspecies P. pacifica pacifica Lang, 1965 (see also Wells 2007); the first two taxa differ primarily in details of the female antennule, P4 endopod and the male P3 exopod. Mielke’s (1981) subspecies is here upgraded to full species rank since it differs sufficiently from Lang’s (1965) population to warrant such status: (a) second antennulary segment with blunt protuberance instead of spinous projection; (b) P1 enp-1 10 times instead 8 times as long as wide; (c) P2–P3 exopods ♀ distinctly shorter; (d) P3 exp-3 ♁ inner distinctly longer instead of shorter than outer distal spine; (e) baseoendopod P5 ♁ with strongly developed seta instead of tiny reduced seta; and (f) caudal ramus 1.3 times as long as maximum width instead of quadratic.

Brady’s (1910) original description of P. gracilipes (as Laophonte gracilipes) from the Kerguelen Islands (Grande Terre, Baie de l’Observatoire) is fragmentary and lacking in detail. Lang (1936) redescribed the species based on material from the Falklands and Pallares (1968) did the same using material from Puerta Deseado (Santa Cruz, Argentina). Howev- er, both redescriptions differ significantly in the number of inner setae on P3–P4 exp-3, the morphology of the female P5, the size of P1 exopod (relative to the endopod) and the length of the apophysis on the male P3, strongly suggesting that the Falklandian and Argentinian populations belong to different species. Wells et al. (1982) and Wells (2007) adopted Lang’s (1936) swimming leg armature pattern in their respective identification keys, however, both incorrectly stated that the male P5 endopodal lobe lacked setae. Although Lang (1936) showed an endopodal seta, their error presumably stemmed from a misinterpretation of Brady’s (1910) original figure of the male P5 which also shows the endopodal seta but not the typical outer basal one. Although the supporting evidence is admittedly slim (morphometric differences in P1 exopod and P2 endopod ♁) we have elected to attribute the Falklandian material to P. gracilipes and to propose a new species, P. pallaresae, sp. n., for the specimens illustrated by Pallares (1968). It should be noted that Pallares figured the female antennule as 8-segmented but stated in the text that it consists of only 7 segments (which is conceivably the correct number). Paralaophonte obscura Vervoort, 1962 from New Caledonia appears to be most closely related to P. pallaresae, sp. n. but differs from the latter in the female by the presence of a small conical protuberance on the second antennulary segment and the semicircular P5 exopod in which the inner distal seta is only slightly longer than proximal inner one, and in the male by the presence of only 4 elements on the P5 exopod. Paralaophonte pallaresae, sp. n. can be characterized by the following differential diagnosis:

Paralaophonte. Abdominal somites without a middorsal spinous process. Caudal rami cylindrical, about 1.5 times as long as maximum width; with seta V elongate. Antennule ♀ 7-segmented; segment 2 without horn, spinous process or protuberance. P1 exopod 3-segmented. P3–P4 exp-3 with 1 inner seta. P3 enp- 2 ♀ with 5 elements. P3 endopod ♁ 3-segmented with apophysis on enp-2 and 4 elements on enp-3; apophysis distinctly longer than endopodal segments combined. P4 enp-2 with 4 elements. P5 exopod ♀ longer than wide, inner distal seta twice the length of proximal inner one; baeoendopod with 4 elements. P5 exopod ♁ with 5 elements; longest seta at most 2.5 times the length of segment; endopodal margin with 1 long seta. Body length: 590–670 µm (♀), 500–510 µm (♁).

The original material collected by Dr Rosa Pallares is no longer available for re-examination (Dr S. Ménu-Marque, Universidad de Buenos Aires, pers. commn). In accordance with ICZN Arts 16.4 and 72.5.6 the male specimen illustrated by Pallares (1968: 87) in her plate XXXII (Figs 1, 5, 9, 12, 15) is here fixed as the holotype of P. pallaresae, sp. n. Type locality: Puerto Deseado, Santa Cruz Province (Argentina), plankton.

Jakobi (1953) proposed the genus Loureirophonte for two new species from Southern Brazil, L. catharinensis (type by original designation) and L. paranaensis and claimed a close relationship with the inopinata -group of Laophonte. Both Vervoort (1964) – who favoured a relationship with the inornata -group of Laophonte – and Lang (1965) questioned the accuracy of Jakobi’s illustrations and generic diagnosis and doubted the validity of Loureirophonte until Mielke (1981) confirmed its separate identity by providing a detailed description of a third species, L. isabelensis Mielke, 1981. This course of action was corroborated by Fiers (1993) in his revision of the genus which saw the addition of five new species and another two which were transferred from other genera (Laophonte caesarea Por, 1964; Paralaophonte subterranea Lang, 1965). With the recent addition of L. psammophila Mielke, 2001 and L. minutum Gómez & Boyko, 2006 the genus now includes 12 species (Mielke 2001; Gómez and Boyko 2006) (Table 3) although it is known that other as yet undescribed species occur in the Galapagos (Mielke 1981). Fiers (1993) provided a key to species which was recently updated by Gómez and Boyko (2006). Fiers was also the first to claim a sistergroup relationship between Paralaophonte and Loureirophonte based on the sexual dimorphism of the P2 endopod, the presence of 5 setae on the P5 exopod of both sexes, and the presence of 4 setae and one seta on the P5 endopodal lobe in females and males, respectively. He also listed a suite of characters that serves to distinguish Loureirophonte from its sistertaxon: (a) P2 enp- 2 ♀ with 1 distal and 2 inner setae (0.210); (b) bulbous appearance of the sexually dimorphic distal inner seta of P2 enp-2 (with a lamellar structure in the distal third); and (c) 1-segmented P4 endopod. Characters (a) and (c) are autapomorphies of Loureirophonte (although Fiers (1993) did report specimens of L. mediterranea that displayed a 2-segmented P4 endopod) supporting the monophyly of the genus. Both Paralaophonte and Loureirophonte display a homologous sexual dimorphism on the P2 endopod, involving the modification of the distal inner seta on enp-2. In the former genus the seta has attained a further derived state of modification (as described under character (b) above), raising the suspicion that Loureirophonte is merely nested within Paralaophonte. Indeed, at present there is not a single apomorphy supporting the monophyly of Paralaophonte, potentially rendering the latter paraphyletic exclusive of Loureirophonte. In addition, the dichotomy between the two genera that was traditionally based on different types of P2 endopod sexual dimorphism appears to be false since it is neither jointly exhaustive nor mutually exclusive. The evolutionary transition between both genera is best demonstrated by the modification in male Paralaophonte macera Sars, 1908b and P. asellopsiformis Lang, 1965 which is virtually identical to the Loureirophonte condition and, similarly, the state of the inner distal seta in male L. furcata Fiers, 1993 which resembles the Paralaophonte condition (Sars 1908b; Fiers 1993). Although the presence of such intermediate taxa casts further doubt on the validity of the basal split between Loureirophonte and Paralophonte we have refrained from synonyzing these genera pending a thorough phylogenetic analysis at species level.

Five species have been added to the genus Paralaophonte since Wells’ (2007) checklist: P. lamellipes (Nicholls, 1944), comb. n., P. galapagoensis Mielke, 1981, grad. n.,

a Wells and Rao (1987) also recorded specimens with a 7-segmented antennule in the female and without a spur on the second segment; Hamond (1972) also observed the 7-segmented condition while Petkovski (1964) recorded a female with a 6-segmented antennule without a spur on the second segment. According to Wells and Rao (1987) the shape and size of the rostrum and the cephalothorax remains as the only reliable criterion to distinguish P. brevirostris from P. congenera. Pending a re-examination of topotype material, Willey’s (1935) variety fissirostris, which was upgraded to subspecific level by Lang (1965), is no longer recognized as valid.

b Sars’ (1908b) original description of the male shows 2 setae on the P5 baseoendopod; re-examination of the type material revealed that the short inner element represents a tube-pore. Both Hamond (1972, 1973) and Wells and Rao (1987) pointed out the difficulties in discriminating P. congenera and P. brevirostris. Hamond’s (1969) male shows a spur on the second segment of the antennule [also present in the North Carolina material examined by Hamond (1973)] and a distinctly pitted cephalothorax; Sars (1908b) did not observe these characters in the Norwegian material. Yoo and Lee’s (1995) record from the Yellow Sea displaying only 4 setae on P5 exopod ♁, appears to represent a different species; Wells (2007) pointed out that their illustration of the P 4 in reality refers to the P2.

c Monard’s (1935) report of an 8-segmented antennule in this species is considered unlikely (cf. Lee and Huys 1999). The species was originally described from Salammbô (Tunisia) and has not been recorded again until recently when Nurul Huda and Zaleha (2005) found it in Peninsular Malaysia; their record (and that of Zaleha et al. 2006) which gives only the armature formula of P2–P4 requires confirmation. Goddard’s (2006) claim that his material from Robinson Crusoe Island (Juan Fernández Archipelago, Chile) may be attributed to P. octavia cannot be substantiated because it displays only one inner seta on P3–P4 exp-3; the only other known species which displays the same reduced formula is P. zimmeri but this species has a 6-segmented antennule in the female and a small spinous process on its second segment [8-segmented (?) and without such process in Goddard’s material].

d Both Gurney (1927) and Sewell (1940) erroneously illustrated the female antennule as 8-segmented (cf. Lee and Huys 1999: 324).

e Kornev and Chertoprud’s (2008) swimming leg armature formula for this species is radically different from that mentioned in previous descriptions (Sars, 1909; Mielke, 1974): P2 (exp: 0.1.123; enp: 1.120), P3 (exp: 0.1.223; enp: 0.221), P4 (exp: 0.0.023; enp: 0.121). The reported absence of the spur on the second antennulary segment requires confirmation.

f Vervoort (1964) reported a very long inner seta on P3 enp- 2 in the male but re-examination of the holotype has proven this to be erroneous (Huys and Lee 2000). g Kornev and Chertoprud (2008) confirmed the presence of a small spur on the second antennulary segment of the female [overlooked in Sars’ (1908b) original description and Chislenko’s (1967) redescription]; their swimming leg armature given on p. 311 contradicts the illustrations of P2 and P4.

h Although Hamond (1973) showed no hesitation in placing P. sculpta in the gracilipes -group of Paralaophonte, its generic assignment remains doubtful because of the absence of males.

i Chislenko (1977) did not figure the male P3 or P4, suggesting there is no sexual dimorphism in these legs; if this proves to be correct P. innae is sufficiently different from P. perplexa to warrant distinct species status, however, females of these two species may be extremely difficult to separate.

j Chislenko’s (1967) specimens from the White Sea differ from Sars’ (1911) type population in several aspects and may represent a distinct species: (1) second antennulary segment ♀ without a spur; (2) P5 exopod ♀ with 5 elements instead of 4; (3) P2 enp-2 ♁ distinctly longer; (4) P3 exp-1 ♁ outer spine much larger; (5) P3 exp-3 ♁ with only 1 inner seta instead of 2; and (6) P5 exopod ♁ and its middle element distinctly longer. Unfortunately, Kornev and Chertoprud’s (2008) report on P. karmensis from the White Sea did not resolve the issue but instead added to the confusion surrounding it. They confirmed the presence of the antennulary spur but presented a radically divergent armature formula for P1 (exopod 3-segmented), P3 (exp: 0.1.123; enp: 0.121) and P4 (exp: 0.0.123) and considered the number of setae on the P5 exopod ♀ variable (4 or 5).

k There is considerable confusion over the segmentation pattern of the female antennule. Brian (1921) described it as 5-segmented with segments 1–2 partially fused; Brian (1917) and Pesta (1959) as 6-segmented; and Lang (1948) as indistinctly 7-segmented with segments 5–6 incompletely separated (based on Monard’s (1928) redescription).

l Apostolov (2008) shows 2 inner and 2 distal setae on P3 enp-2 ♁ (formula 220); the 2-segmented condition and absence of an apophysis suggest that the outer spine is lacking in the female (as in e.g. P. innae); the number of inner setae expressed in P. kolarovi females may be 2 or 3 (in the latter case one seta is typically lost in male Paralaophonte).

m Nicholls (1944) stated that the P1 exp is 2-segmented, the distal two segments being fused with only 3 terminal setae (in reality the distal segment bears 5 elements); Huys and Lee (2000: 81) confirmed the true nature of the modified male P2 endopod and suggested a relationship with Paralaophonte; Wells (2007: 64) placed it as species incertae sedis in this genus; it is here formally transferred to Paralaophonte as Paralaophonte lamellipes (Nicholls, 1944) comb. nov. Lee and Huys (1999: 324) also confirmed that the female antennule is 7-segmented instead of 8-segmented.

n The modified inner distal seta resembles more the condition in Paralaophonte (Fiers 1993: Fig. 2c).

o Setal formula as reinterpreted by Fiers (1993).

p Fiers (1993) doubted the presence of an outer seta on P3 enp-2 and P4 endopod; these “elements” are here reinterpreted as ornamental spinules.

q Fiers (1993) also reported specimens with a 2-segmented P4 endopod (formula 0.010).

r The inner setae of P2 enp-2 are displaced towards the apical margin of the segment creating the impression that there are 1 inner and 2 distal setae instead of 2 inner and 1 distal setae; taking into account the observed variability Lang (1965) erroneously tabulated the setal formula as 0.(0–1)20; Fiers’ (1993) formula [0.(1–2)20] is equally incorrect (his Table 1).

P. harpagone Gheerardyn, Fiers, Vincx & De Troch, 2006, P. kolarovi (Apostolov, 2008), comb. n. and P. pallaresae, sp. n. Although Wells (2007) listed Laophonte royi Jakubisiak, 1932 only as a species incertae sedis in the Laophontidae it is here included as a valid species of Paralophonte, being very closely related to P. majae Petkovski, 1964. The 39 species currently recognized as valid in the genus Paralaophonte can be identified with the key below.

1. Caudal rami broadly lamellar, close together, with seta V very short........... 2

– Caudal rami usually cylindrical, with seta V elongate.................................. 3

2. P1 exopod 2-segmented; P3 exp-3 with 1 inner seta; P4 exp-3 with 7 setae/spines; P3 exopod ♁ 2-segmented; P5 exopod ♁ with 4 spines......... P. aenigmaticum

– P1 exopod 3-segmented; P3 exp-3 with 2 inner setae; P4 exp-3 with 4 setae/spines; P3 exopod ♁ 3-segmented; P5 exopod ♁ with 5 setae........... P. asellopsiformis

3. P1 exopod 2-segmented, with 4 setae on exp-2; maxillipeds very large and specialized................................................................................ P. harpagone

– P1 exopod 3-segmented with 4 setae on exp-3, or 2-segmented with 5 setae on exp-2..................................................................................................... 4

4. P3 exp-3 with 1 inner seta.......................................................................... 5

– P3 exp-3 with 2 inner setae....................................................................... 15

5. P4 enp-2 with 3 elements (formula 120)..................................................... 6

– P4 enp-2 with 4 elements (formula 121)..................................................... 7

6. Caudal ramus about 1.5 times as long as wide............................. P. kolarovi

– Caudal ramus at least twice as long as wide.............................. P. livingstoni

7. P1 exopod 2-segmented.............................................................................. 8

– P1 exopod 3-segmented............................................................................ 12

8. Caudal ramus conical and about 3 times as long as wide; P5 endopodal lobe ♀ with 3 setae.............................................................................. P. longipes

– Caudal ramus cylindrical and not more than twice as long as wide; P5 endopodal lobe ♀ with 4 setae........................................................................ 9

9. P5 exopod ♀ with 4 setae; P3 exp-3 ♁ with 7 setae/spines........ P. karmensis

– P5 exopod ♀ with 5 setae; P3 exp-3 ♁ with at most 6 setae/spines........... 10

10. First and second abdominal somites with dorsal bilobate lappets; second antennulary segment ♀ without protuberance; P5 ♁ with 5 setae on exopod and 1 on endopodal lobe............................................................... P. lunata

– First and second abdominal somites without dorsal bilobate lappets; second antennulary segment ♀ with small conical protuberance; P5 ♁ with different armature................................................................................................... 11

11. Caudal ramus 1.5 times as long as wide; P5 ♁ with 5 setae on exopod and none on endopodal lobe..................................................... P. spitzbergensis

– Caudal ramus twice as long as wide; P5 ♁ with 4 setae on exopod and 1 on endopodal lobe............................................................................... P. tenera

12. Abdominal somites with a middorsal spinous process; P3 enp- 2 ♀ with 4 elements; P3 endopod ♁ 2-segmented................................... P. quaterspinata