Bioacoustics of Lernanthropus elegans

Remarks: The new species was found on Atractoscion aequidens , a member of the family Sciaenidae , and this family serves as host to about 20 species of Lernanthropus in total ( Table 3 ). Most of the species listed in Table 3 are exclusively parasitic on sciaenid hosts, but a few, such as L. gisleri and L. leidyi have occasionally been reported from non-sciaenids. In addition, L. pomatomi , L. pupa and L. paenulatus were all originally described from nonsciaenid hosts but each has been reported on a single occasion from a sciaenid host. Detailed comparison of the new species with all of these other species found on sciaenid hosts reveals some significant differences as well as shared character states. The new species, L. elegans sp. nov. , can be readily distinguished from L. huamani Luque & Farfán, 1990 , L. longipes Wilson, 1932 , L. pacificus Oliva & Durán, 1982 , and L. paralonchuri Luque, Bruno & Covarrubias, 1989 , by the length of the lobes of leg 4, which are shorter than the body in the new species but markedly longer than the entire body in these four species. Another very distinctive species is L. grassei . This is an elongate, slender species which has very unequal lobes on leg 4: the exopodal lobe is almost twice the length of the endopodal lobe. This contrasts with the more-or-less equal lobes of the new species. The South American species L. cynoscicola has an unusually short dorsal trunk plate so that the tip of the abdomen and the entire length of the caudal rami are visible in dorsal view, whereas in L. elegans sp. nov. the dorsal trunk plate is more extensive, concealing the entire urosome and all but the tips of the caudal rami. Lernanthropus barnardi Capart, 1959 and L. nunesi Capart, 1959 are both known only from their inadequate original descriptions in Capart (1959) . However, the former can be distinguished by the relatively short lanceolate lobes of leg 4 which extend beyond the posterior margin of the dorsal trunk plate only by about 30% of their total length, whereas in the new species about 70% of the length of these lobes is visible in dorsal view. The latter species, L. nunesi , has elongate fourth leg lobes but differs from the new species in having a very reduced leg 5 compared to the large lobate leg 5 of the new species. The original description of L. leidyi was also inadequate, but both sexes of this species were redescribed by Luque & Paraguassú (2003) . Comparing the new species with this redescription of L. leidyi allows us to distinguish between them by the length of dorsal trunk plate, which is longer than the anterior part of the trunk in the new species but distinctly shorter in L. leidyi , and by the fifth leg which is elongate in the new species but short and subcylindrical in L. leidyi , according to Luque & Paraguassú (2003) . The fifth legs of L. pagodus Krøyer, 1863 appear to be reduced or absent, since Krøyer (1863 : Tab VIII, Fig. 2c ) does not figure them in his ventral habitus drawing. This species also differs in having a broad dorsal trunk plate (about 2.0 times wider than the cephalothorax) with a median indentation in its posterior margin, whereas L. elegans sp. nov. has a more slender dorsal trunk plate (only about 1.5 times wider than the cephalothorax) with an evenly convex posterior margin. The new species shares a distinctive set of character states with the remaining eight species from Table 2 , including the widely distributed L. gisleri . This character set includes: 7-segmented antennule with the segment bearing the subapical aesthetasc separate from the apical segment (these segments are fused in many Lernanthropus species); the proximal segment of the antennule is fused to a swelling on the surface of the cephalothorax and both the segment and swelling are densely ornamented with long setules; the maxilla bears a curved process on the basis just proximal to the base of the apical claw; the protopod of leg 1 is densely ornamented with long setules; leg 3 forms a large, (postero-) laterally directed lamella; the rami of leg 4 are both elongate; leg 5 forms an elongate process; and the caudal rami are elongate. Detailed comparisons are required to separate L. elegans sp. nov. from these eight species: L. gisleri , L. capistroides Olivier & van Niekerk, 1995 , L. cruciatus Pillai, 1962 , L. francai Nuñes-Ruivo, 1962 , L. indefinitus Koyuncu, Castro-Romero & Karaytug, 2012 , L. otolithi Pillai, 1963 , L. pami Tripathi, 1962 , and L. sciaenae Gnanamuthu, 1947 . Lernanthropus pami is included in this group but, unfortunately, only limited comparisons are possible because this species is very poorly known and its original description contains major mistakes (cf. Pillai, 1985 ). The information available from Tripathi (1962) indicates that the fifth legs (erroneously interpreted as a third lobe of a “trifoliate” leg 4) are elongate but extend only to about the mid-level of the caudal rami. In contrast, L. elegans sp. nov. has lanceolate fifth legs that extend well beyond the distal tips of the caudal rami. Additionally, the tips of the caudal rami only just reach the posterior margin of the dorsal trunk plate in L. pami but extend well beyond this margin in the new species. Tripathi (1962) remarked that L. pami was similar to L. sciaenae described by Gnanamuthu (1947) , probably because Gnanamuthu had also misinterpreted leg 4 as trifoliate. His figure of the antennule of L. sciaenae shows the setular ornamentation on the proximal segment, even though the description is lacking in other details. Lernanthropus sciaenae resembles L. pami in the proportional lengths of the fifth legs and caudal rami, and in the extent of the caudal rami relative to the margin of the dorsal trunk plate, and differs from L. elegans sp. nov. in these features. We propose to treat L. pami as a species inquirendum , but it is also possible that L. pami is a junior synonym of L. sciaenae . The original description of L. capistroides was supported only by scanning electron micrographs ( Olivier & van Niekerk, 1995 ). These images provide considerable detail of the appendages: for example, the maxilla of the female carries a curved claw (canna in Olivier & van Niekerk, 1995 ) on the inner margin of the basis plus a thinwalled process (clavus in Olivier & van Niekerk, 1995 ) on the base of the terminal claw (calamus in Olivier & van Niekerk, 1995 ). This armature is shared with L. elegans sp. nov. However, Olivier & van Niekerk (1995) did not provide an illustration of the habitus, which renders comparisons with older descriptions problematic. The most readily observable difference between L. capistroides and the new species is the caudal rami, which do not reach the posterior margin of the dorsal trunk plate in the former but extend well beyond this margin in the latter. The mean body length of L. capistroides is given as 7.2 mm by Olivier & van Niekerk (1995) , of which the dorsal cephalic shield comprised 1.3 mm and the dorsal trunk plate 3.2 mm . We can calculate that the mean length of the anterior trunk was therefore 2.7 mm . This is about 2.1 times longer than the cephalothorax which differs from the new species, in which the anterior trunk is only 1.6 times longer than the cephalothorax. Lernanthropus francai was first described from off the coast of Angola ( Nuñes-Ruivo, 1962 ) and has only been reported once since, in a list of copepods found on Vietnamese fishes ( Kazachenko et al ., 2014 ). It is known only from the female which exhibits many detailed similarities to L. elegans sp. nov. For example, both species have a densely setulose outer expansion of the protopodal part of leg 1 and the endopod of this leg bears a single apical seta that is about as long as the ramus. Both also have the setulose, posteriorly-directed proximal lobe on the maxillule. The key difference between these species is the extent of the caudal rami, the tips of which do not reach the posterior margin of the dorsal trunk plate in L. francai , but extend beyond it in L. elegans sp. nov. They can also be distinguished by the relative lengths of the lanceolate rami of leg 4 relative to the dorsal trunk plate: in L. francai these rami extend beyond the posterior margin of the plate by slightly more than half of their entire length whereas in the new species about 75% of their length is visible in dorsal view, extending beyond the margin. The Indian species L. cruciatus has a body length of over 16 mm ( Pillai, 1985 ) and is instantly recognizable by its enormous third legs, which are laterally directed and about equal in length to the cephalothorax and anterior trunk combined. The dorsal trunk plate of L. cruciatus is also very well developed, comprising just over half (53%) of the entire body length. In contrast, L. elegans sp. nov . has third legs that are slightly shorter than the anterior trunk region alone, and its dorsal trunk plate comprises only 42% of body length. The slender body shape of the female of L. elegans sp. nov. contrasts with the rather robust body form of L. otolithi . The latter has an almost circular dorsal trunk plate which is slightly wider than long whereas in the former the plate is about 1.3 times longer than wide and has tapering linear lateral margins that expand posteriorly. The ventrally-produced lateral margins of the dorsal cephalic shield of L. otolithi project anteriorly generating a trilobate frontal margin whereas the frontal margin is straight with rounded corners in L. elegans sp. nov . The original description of L. indefinitus ( Koyuncu et al ., 2012 ) combines some excellent illustrations of particular limbs (such as the antennule and legs 1 and 2) with inadequate illustrations which fail to show important features (such as the caudal rami, from which most of the caudal setae are missing). In female L. indefinitus the fifth leg lobes do not reach the tips of the caudal rami whereas in L. elegans sp. nov . they extend well beyond the tips of the rami. The caudal rami themselves are about 3 times longer than wide in L. indefinitus compared to about 5 times longer than wide in the new species. Finally, the new species can be differentiated from L. gisleri by the length of the caudal rami and fifth legs relative to the free posterior margin of the dorsal trunk plate: in L. gisleri the caudal rami are completely concealed in dorsal view, hidden beneath the dorsal trunk plate while the fifth legs reach to the posterior margin of the dorsal trunk plate and the tips may be visible dorsally in some specimens. In contrast, in L. elegans sp. nov. the tips of the caudal rami and the distal 25% of the fifth legs extend beyond the margin of the plate and are visible in dorsal view. The structure and armature of the limbs are very similar in these two species. The antennules are 7-segmented in both and the setation is almost identical. The absence of setular ornamentation on segment 1 in Kabata’s figure (1979b: fig. 1058) is significant since it is very conspicuous in L. elegans sp. nov. and would not be easy to overlook. Both species possess a hirsute posterior swelling at the base of the maxillule. Legs 1 and 2 are also very similar in the two species. The only difference in leg 1 is the extent of the setular ornamentation, which is much more extensive in L. elegans sp. nov. In leg 2 both rami are ornamented with surface spinules in the new species but, according to Kabata (1979b) , only the endopod carries any spinules in L. gisleri . Lernanthropus species Host Locality Reference L. barnardi Capart, 1959 Umbrina canariensis Valenciennes, 1843 South Atlantic off coast of An- Capart, 1959 L. capistroides Olivier & van Niekerk , (as Umbrina valida ) Otolithes ruber (Bloch & Schneider, 1801) gola (12°54’S 11°52’E) St Lucia estuary, South Africa Olivier & van Niekerk, 1995 1995 L. cruciatus Pillai, 1962 “sciaenid” Kerala, India Pillai, 1962 L. cynoscicola Timi & Etchegoin, 1996 Cynoscion striatus (Cuvier, 1829) Argentina Timi & Etchegoin, 1996 Cynoscion guatucupa (Cuvier, 1830) Argentina & Uruguay; Brazil Timi, 2003 ; Sabas & Luque, 2003 L. elegans sp. nov . Atractoscion acquidens (Cuvier, 1830) Coffs Harbour, New South present account L. francai Nuñes-Ruivo, 1962 Umbrina ronchus Valenciennes, 1843 Wales; Australia Angola Nuñes-Ruivo, 1962 Larimichthys crocea (Richardson, 1846) Vietnam Kazachenko et al ., 2014 L. gisleri van Beneden, 1852 * Argyrosomus regius (Asso, 1801) as Sciaena aquila Belgium; French coast of North van Beneden, 1852 ; Hesse, 1877 ; Delamare Argyrosomus regius (Asso, 1801) Sea; Senegal Scotland Deboutteville & Nuñes-Ruivo, 1954 Kabata, 1979b Umbrina cirrosa (Linnaeus, 1758) Adriatic Sea; Ligurian Sea Heider, 1879 ; Brian, 1906 Sciaena umbra Linnaeus, 1758 (as Corvina nigra ) Adriatic Sea; Ligurian Sea Heider, 1879 ; Brian, 1906 Argyrosomus japonicus (Temminck & Schlegel, 1843) Port Willunga, Australia, Kabata, 1979a (as Sciaena antarctica ) Argyrosomus japonicus (Temminck & Schlegel, 1843) Port river, South Australia present account Sciaena umbra Linnaeus, 1758 (as Corvina nigra ) Senegal Delamare Deboutteville & Nuñes-Ruivo, Umbrina steindachneri Cadenat, 1951 Senegal 1954 Delamare Deboutteville & Nuñes-Ruivo, Umbrina canariensis Valenciennes, 1843 Senegal 1954 Diebakate & Raibaut, 1996 Umbrina canariensis Valenciennes, 1843 off West Africa Capart, 1959 (as Umbrina valida ) Cynoscion nebulosus (Cuvier, 1830) Gulf of Mexico; Texas (USA) Bere, 1936 ; Pearse, 1952 Argyrosomus hololepidotus (Lacepède, 1801) off West Africa Kabata & Gusev, 1966 (as Johnius hololepidotus ) Pseudotolithus moorii (Günther, 1865) off West Africa Capart, 1959 (as Corvina cameronesis ) Sciaena sp. Japan Yamaguti, 1936 , 1963 ......continued on the next page Lernanthropus species Host Locality Reference Johnius dussumieri (Cuvier, 1830) China Song & Chen, 1976 L. grassei Delamare Deboutteville & Nu- (as Sciaena dussumieri ) Pseudotolithus senegallus (Cuvier, 1830) Senegal Delamare Deboutteville & Nuñes-Ruivo, ñes-Ruivo, 1954 L. huamani Luque & Farfán, 1990 (as Otolithus ( Johnius ) brachygnathus Menticirrhus ophicephalus (Jenyns, 1840) Peru 1954 Luque & Farfán, 1990 Sciaena deliciosa (Tschudi, 1846) Peru Stellifer minor (Tschudi, 1846) Peru L. indefinitus Koyuncu, Castro-Romero & Argyrosomus regius (Asso, 1801) Mediterranean Sea Koyuncu et al ., 2012 Karaytug, 2012 L. leidyi Wilson, 1922 ** Bairdiella chrysoura (Lacepède, 1802) North Carolina, Florida (USA) Wilson, 1922 ; Pearse, 1952 , Causey, 1955 Umbrina canosai Berg, 1895 Brazil Luque & Paraguassú, 2003 L. longipes Wilson, 1932 Pogonias cromis (Linnaeus, 1766) Woods Hole, USA Wilson, 1932 Sciaenops ocellatus (Linnaeus, 1766) North Carolina, Texas, USA Pearse, 1947 ; 1952 Larimus fasciatus Holbrook, 1855 Gulf of Mexico Bere, 1936 L. nunesi Capart, 1959 Pentheroscion mbizi (Poll, 1950) (as Sciaena mbizi ) South Atlantic off coast of Zaire Capart, 1959 L. otolithi Pillai, 1963 Otolithes ruber (Bloch & Schneider, 1801) (05°56’S, 12°0’E) Trivandrum, India Pillai, 1963 , 1985 (as Otolithus argenteus Cuvier ) Pennahia pawak (Lin, 1940) Taiwan Ho et al ., 2008 Pterotolithus maculatus (Cuvier, 1830) India Pillai, 1985 (as Otolithus maculatus ) Johnius carouna (Cuvier, 1830) Vietnam Kazachenko et al ., 2014 Daysciaena albida (Cuvier, 1830) S.E. coast of India Raja et al ., 2018 L. pacificus Oliva & Durán, 1982 Cilus gilberti (Abbott, 1899) (as Sciaena gilberti ) Peru Oliva & Durán, 1982 [as L. guacoldae Villalba & Fernandez , Sciaena deliciosa (Tschudi, 1846) Concepción Bay, Chile Villalba & Fernandez, 1984 1984 ***] L. pagodus Krøyer, 1863 Equetus lanceolatus (Linnaeus, 1758) Brazil Krøyer, 1863 L. pami Tripathi, 1962 (as Equetus balteatus ) Otolithoides pama (Hamilton, 1822) (as Pama pama ) India Tripathi, 1962 ; Pillai, 1985 L. paracruciatus sp. nov. Protonibea diacanthus ( Lacepède, 1802 ) Northern Territory, Australia present account L. paralonchuri Luque, Bruno & Covarru- Paralonchurus peruanus (Steindachner, 1875) Peru Luque et al ., 1989 bias, 1989 ......continued on the next page Lernanthropus species Host Locality Reference Cycnoscion analis (Jenyns, 1842) Peru Iannacone, 2005 L. sciaenae Gnanamuthu, 1947 Johnius glaucus (Day, 1876) (as Sciaena glaucus ) Madras, Kerala (India) Gnanamuthu, 1947 ; Pillai, 1985 Misidentified species L. seriolii Shishido, 1898 Sciaenops ocellatus (Linnaeus, 1766) Louisiana, USA Causey, 1953 [as L. paenulatus Wilson, 1922 ]+ L. polynemi Richiardi, 1881 Otolithes ruber (Bloch & Schneider, 1801) Gulf of Arabia Bannai, 2002 [as L. trithfoliatus ]++ L. pomatomi Rathbun, 1887 +++ Cynoscion nebulosus (Cuvier, 1830) Louisiana, USA Causey, 1953 L. pupa Burmeister, 1833 ++++ Cynoscion nebulosus (Cuvier, 1830) Louisiana, USA Causey, 1953 * L. gisleri has also been reported from a number of non-sciaenid hosts, including Selenotoca multifasciata (Scatophagidae) (as Scatophagus multifasciatus ) by Kabata (1979a) , Centropomus unidecimalis (Bloch, 1792) (Centropomidae) by Bere (1936) , Pearse (1952) , and Tavares & Luque (2004) , Polydactylus quadrifils (Cuvier, 1829) (Polynemidae) by Capart (1959) and Paralichthys sp. ( Paralichthyidae ) by Causey (1953) . The L. gisleri r ecorded from Lichia amia Linnaeus (Carangidae) by Brian (1906) was misidentified, it is L. micropterygis (see text). ** L. leidyi has also been reported from a non-sciaenid host, Morone americana (Gmelin, 1789) (Moronidae) , by Wilson (1922) . *** Luque & Farfán (1990) considered L. guacoldae Villalba & Fernandez, 1984 to be a junior synonym of L. pacificus Oliva & Durán, 1982 . + Lernanthropus seriolii is typically a parasite of carangids of the genus Seriola Cuvier ; we consider that the report (as L. paenulatus Wilson, 1922 ) from Sciaenops ocellatus by Causey (1953) is probably a misidentification. ++ Lernanthropus polynemi Richiardi, 1881 is the senior subjective synonym of L. trifoliatus Bassett-Smith, 1898 (see Piasecki & Hayward, 2002 ). The type host of L. polynemi is Eleutheronema tetradactylum (Shaw, 1804) and it has been recorded from various other polynemids including, Polydactylus plebius (Broussonet, 1782) , P. sextarius (Bloch & Schneider, 1801) and Filimanus heptadactyla (Cuvier, 1829) plus two carangids although these are probably misidentifications (see Table 2). Under the name of its junior synonym (misspelt as Lernanthropus trithfoliatus ), L. polynemi was reported from the sciaenid Otolithes ruber by Bannai (2002) . It is probable that this is a misidentification. +++The type host of L. pomatomi is Pomatomus saltatrix (Linnaeus, 1766) (Pomatomidae) but it was also recorded from a serranid ( Mycteroperca sp.) by Causey (1955) and from the sciaenid Cynoscion nebulosus by Causey (1953) . ++++ Lernanthropus pupa Burmeister, 1833 is typically a parasite of Chaetodipterus faber (Broussonet, 1782) (Ephippidae) but was reported from the sciaenid Cynoscion nebulosus by Causey (1953) . This report is doubtful. The four Lernanthropus females from Sciaena sp. identified by Yamaguti (1936) as L. gisleri are misidentified, as already noted by Koyuncu et al . (2012) . Although not described in full by Yamaguti (1936) , this material appears to belong to the new species, L. elegans sp. nov . , and it seems possible that the material of L. gisleri listed, but not illustrated by Song and Chen (1976) from Johnius dussumieri (Cuvier, 1830) (as Sciaena dussumieri ) caught in China , might also be attributed to the new species. Although not parasitic on a sciaenid host, L. antofagastensis Castro-Romero & Baeza-Kuroki, 1985 is included in our comparisons. This species is parasitic on a haemulid, Anisotremus scapularis (Tschudi, 1846) , found in Chilean coastal waters and it shares many character states with L. elegans sp. nov. including: the swollen proximal segment of the antennule with a dense ornamentation of setules, the swollen and densely setulose base of the parabasal flagellum, the armature on the basis of the maxilla, the long cylindrical fifth legs and the elongate caudal rami. However, these two species can be distinguished by the relative lengths of the fifth legs which extend well beyond the tips of the caudal rami in L. elegans sp. nov . , but only to the base of the caudal rami in L. antofagastensis .