Parabrachiella supplicans (Barnard, 1955)

Lebepe, Modjadji C. & Dippenaar, Susan M., 2016, Barnard’s Brachiella sp., Parabrachiella supplicans (Barnard, 1955) and Eubrachiella sublobulata (Barnard, 1955) (Copepoda: Siphonostomatoida: Lernaeopodidae) deposited in the Iziko South African Museum, Zootaxa 4061 (1), pp. 51-60 : 52-56

Parabrachiella supplicans (Barnard, 1955)

( Figs 1 –7)

Syn. Parabrachiella genypteri (Capart)

Neobrachiella supplicans (Castro & Baeza 1987)

Material examined. Nine females (2 dissected) and 2 detached males (S.A.M A12592 ) from the gill filaments of the cape kingklip G. capensis (Smith) off Table Bay deposited in the Iziko South African Museum.

Description of adult female. Body length including posterior processes, excluding egg sacs about 5 mm ( Fig. 1 A) and 6 mm ( Fig. 1 B). Cephalothorax ( Figs 1 A, B) about 1.8 mm and 2.1 mm, respectively; cylindrical, slightly shorter than trunk (about 1.9 mm and 2.4 mm, respectively), expanded anteriorly to form head covered by longer than wide dorsal shield; shallow constriction near base of maxillae separates cephalothorax from trunk; latter longer than wide, narrower anteriorly, armed with pair of unilobed posterior processes posteroventrally and a pair of bilobed process posterolaterally (1.3 mm ( Fig. 1 A) and 1.5 mm ( Fig. 1 B)) respectively; each bilobed posterior processes and each unilobed process enclosed in its own cuticular sheath. Genital process ( Fig. 1 B) short, cylindrical, not observed in other females ( Fig. 1 A); egg sacs ( Fig. 1 A) (1.3mm) with multiseriate egg arrangement.

Antennule ( Fig. 1 C) indistinctly 4-segmented; basal segment inflated, unarmed; segment 2 with whip; segment 3 unarmed, solus absent; segment 4 with 3 setae and 3 conical tubercles; digitiform seta 4 elongate, setae 5 and 6 elongate (see Kabata 1979). Antenna ( Fig. 1 D) with 2-segmented endopod and 1-segmented exopod; exopod bulbous, with numerous apical denticles and 2 prominent spines sub-apically; endopod segment 1 unarmed, segment 2 short, armed with hook 1, slender seta 2, tubercles 3 and 5 short, conical, process 4 rounded and denticulated (see Kabata 1979). Mandible ( Fig. 1 E) with dental formula P1, S1, P1, S1, P1, S1, B4; basal teeth decreasing in size towards base. Maxillule ( Fig. 1 F) bilobed; palp (outer lobe) small, tipped with 2 short setae; endite (inner lobe) larger; terminally armed with 2 large papillae, each apically bearing seta and 1 small seta at base of papillae. Maxilla ( Figs 1 G, H) as long as trunk, united at bulla; one female with arms completely fused, enclosed in a cuticular sheath ( Fig. 1 G) and one with arms completely separated with each enclosed in its own cuticular sheath ( Fig. 1 H); bulla ( Fig. 1 I) with short manubrium and short anchor narrowing towards tip. Maxilliped ( Fig. 1 J) 2-segmented; corpus broad, robust; myxal area inflated with two denticulated patches; short seta between patches; subchela elongate, with stout seta proximally; distomedially armed with densely packed denticles along raised margin; barb slender, about half length of terminal claw; latter tapering, slightly curved with rounded tip, armed with auxiliary tooth on basal half.

Description of adult male. Body ( Figs 2 A, B) (1.4 mm and 1.8 mm, respectively) with distinctive constriction separating cephalothorax and trunk. Cephalothorax ( Figs 2 A, B), both 0.7 mm, slightly shorter than trunk (0.8 mm and 1.1 mm, respectively), posteriorly extended. Trunk indistinctly segmented ( Fig. 2 B); caudal rami ( Figs 2 C, D) short, bilobed apically. Antennule ( Fig. 2 E) indistinctly 3-segmented, whip not observed, distal segment with 3 long setae and 3 short tubercles. Antenna ( Fig. 2 F) endopod larger than exopod; exopod with apical denticles and 2 prominent spines; endopod 2-segmented; segment 1 elongate, unarmed; segment 2 with dorsal hook 1 slightly curved with slender, spiniform seta 2, prominent seta 3 elongate, process 4 armed with prominent denticles along medial margin, process 5 absent. Mandible not observed. Maxillule ( Fig. 2 G) similar to female. Maxilla ( Fig. 2 H) 2-segmented; corpus bulbous, with myxa raised to meet claw on medial margin; subchela short, with robust base, claw slightly bent with no secondary armature. Maxilliped ( Fig. 2 I) 2-segmented; corpus elongate, with prominent myxa meeting claw on medial margin; subchela short, with short seta on lateral margin; claw slightly curved.

Remarks. Parabrachiella supplicans was described from the gills of G. capensis captured in Table Bay, South Africa. Oldewage (1992) reported P. supplicans collected from the gills of Merluccius capensis Castelnau ; Merluccius paradoxus Franca, and Chelidonichthys queketti (Regan) off the south coast of South Africa with no subsequent reports for the last 23 years. Both males and females of the examined specimens exhibit variations in external morphology. Three females have a larger general body size, possess a small genital process and completely fused maxillae ( Figs 1 B, G) while the other six females have maxillae completely separated with each arm enclosed in its own cuticular sheath and no genital process ( Figs 1 A, H). Similarly, one male is larger in size, with an indistinctly 3-segmented trunk and caudal rami ornamented with rows of short spines ( Figs 2 B, D) while the other male has a trunk that is indistinctly 2-segmented and caudal rami without ornamentation ( Figs 2 A, C).

Parabrachiella species are divided into three groups based on the number of posterior processes they possess (Castro & Baeza 1987). Group I has two pairs of posterior processes, Group II has one pair of posterior processes and Group III has more than two pairs of posterior processes. Castro & Baeza (1987) placed P. supplicans in Group I, but Piasecki et al. (2010) omitted P. supplicans from Group I. The described specimens have more than two pairs of posterior processes (bilobed process counts as one pair), and thus P. supplicans should be placed in Group III. Group III is the smallest within the genus with only five valid species, namely P. triglae (Claus) ; P. robusta (Wilson) ; P. septicauda (Shiino) ; P. genypteri (Capart) and P. exilis (Shiino) (Castro & Baeza 1987) . The structure of the appendages of species in Group III is similar and the difference among the species is in the general habitus of the males and females, especially with the proportions of the posterior processes. Parabrachiella supplicans and P. genypteri can be distinguished from the other three species by possessing elongate, well developed, bilobed posterolateral processes which are the same length as the unilobed posteroventral processes while the posterior processes are shorter in the other three species.

Parabrachiella genypteri was first described as Brachiella genypteri from the branchial cavity of G. capensis off Fort Rock Point, Namibia and transferred to Neobrachiella (Castro & Baeza 1987) and later to Parabrachiella (Piasecki et al. 2010) . This species bears close resemblance to P. supplicans , described from the same host off Table Bay. However, despite the incomplete information on the structure and armature of the appendages, P. genypteri was accepted as a valid species (Castro & Baeza 1987; Piasecki et al. 2010). A comparison of the description and illustrations of P. genypteri with the current description indicates that P. supplicans and P. genypteri are conspecific and should therefore be synonymized.

The existing groupings of these species, based on the number of posterior processes, is impractical as there are contradicting reports for some specific Parabrachiella species possessing different numbers of posterior processes while most species have reported morphological variations (Kabata 1979; Knoff et al. 1994). This is evident in P. insidiosa (Heller) , reported to have one pair of posterior processes by Kabata (1970) and two pairs of posterior processes by Kabata (1979) and Barnard (1955a) while P. b e r a has four pairs of posterior processes in Japan (Yamaguti 1939) and one pair of posterior processes in Korea (Moon 2014). The fused or unfused appearance of the arms of the maxillae is also variable with P. supplicans the only species reported herein to show both conditions. ( Figs 1 G, H).

According to Piasecki et al. (2010) there are currently 67 valid species in the genus Parabrachiella . However, P. appendiculata (Krøyer) ; P. malabarica (Pillai, Prabha & Balaraman) ; P. pillaii (Kabata & Tareen) ; P. ramosa (Richiardi) ; P. trichiuri (Gnanamuthu) and P. upenaei (Pillai) were omitted while P. elegans (Richiardi) was included. Parabrachiella elegans was however previously assigned to a new genus Eobrachiella (Ho & Do 1984) due to the morphology and armature of the male which seems to be intermediate between Brachiella and Neobrachiella males (Ho & Do 1984), while P. seriolae was synonymized with E. elegans (Ho & Do 1984). Parabrachiella indica (Tripathi) , P. lutiani (Pillai) and P. pillaii (Kabata & Tareen) are three names referring to the same species collected from Lutianus sp. from India and Sparidentex hasta (Valenciennes) in Kuwait (Pillai 1968; Kabata & Tareen 1987). Similarly, Parabrachiella upenaei (Pillai) and P. malabarica (Pillai, Prabha & Balaraman) were transferred to Neobrachiella (Kabata 1979; Castro & Baeza 1987) and thus seem to be valid species of Parabrachiella with no reason to be excluded from the list. Boxshall & Walter (2015) list both P. trichiuri (Yamaguti) and P. trichiuri (Gnanamuthu) as valid species. Ho & Do (1984) examined both P. trichiuri (Yamaguti) collected off Japan and P. trichiuri (Gnanamuthu) collected off India and concluded that they are the same species with small geographical variation. Therefore P. trichiuri (Yamaguti) is the valid species (Ho & Do 1984). Parabrachiella supplicans and P. genypteri as well as P. exilis and P. mugilis are herein synonymized, while P. ramosa (Richiardi) and P. appendiculata (Kroyer) await verification. Therefore the revised total number of valid Parabrachiella species, excluding P. ramosa and P. appendiculata , is 61, namely P. albida (Rangnekar) ; P. amphipacifica (Ho) ; P. anisotremi (Castro & Baeza) ; P. bispinosa (Nordmann) ; P. brevicapita (Kabata) ; P. chavesi (Van Beneden) ; P. chevreuxii (Van Beneden) ; P. chloropthalmi (Kabata) ; P. cirrata (Heegaard) ; P. cirrocauda (Heegaard) ; P. dispar (Castro & Baeza) ; P. exigua (Brian) ; P. exilis ; P. gulosa (Wilson) ; P. gymnofimbriata (Kabata) ; P. hoplognathi (Yamaguti) ; P. incurva Shiino ; P. indica ; P. insidiosa ; P. intermedia (Bere) ; P. kabatai (Luque & Farfan) ; P. merluccii (Bassett-Smith) ; P. microdigitata (Kabata) ; P. m i r i f i c a (Kabata); P. mitrata (Wilson) ; P. multifrimbriata (Bassett-Smith) ; P. nitida (Wilson) ; P. paralicthyos (Castro & Baeza) ; P. regia (Lewis) ; P. robusta (Wilson) ; P. rostrata (Krøyer) ; P. sciaenae (Brian) ; P. septicauda (Shiino) ; P. sihama Song & Chen; P. spinicephala Ringuelet ; P. stellifera (Heegaard) ; P. anserina (Wilson) ; P. auriculata (Castro & Baeza) ; P. bera (Yamaguti) ; P. brevibrachiata (Kabata) ; P. fasciata (Castro & Baeza) ; P. gracilis (Wilson) ; P. hoi (Piasecki) ; P. hostilis (Heller) ; P. hugu (Yamaguti) ; P. jarai Piasecki, Mlynarczyk & Hayward ; P. johnii (Yamaguti) ; P. lata (Song & Chen); P. malabarica ; P. oralis (Castro & Baeza); P. otolithi (Pillai) ; P. pinguis (Wilson) ; P. robusta (Wilson) ; P. rotunda (Pearse) ; P. superba (Leigh-Sharpe) ; P. trichiuri ; P. triglae (Claus) ; P. yongxingensis (Song & Chen); P. annulata (Markewitsch) ; P. menticirrhi (Luque & Farfan) and P. richiardi (Ben Hassine & Raibaut) .

Figures

FIGURE 1. Parabrachiella supplicans (Barnard) adult female. A. Habitus (specimen 1), lateral view; B. Habitus (specimen 2), lateral view; C. Antennule; D. Antenna; E. Mandible; F. Maxillule; G. Maxilla (specimen 2); H. Maxilla (specimen 1); I. Bulla; J. Maxilliped. Scale bars: A, B, G, H 0.5 mm; C, D, E, F, J 10 µm; I 100 µm.

FIGURE 2. Parabrachiella supplicans (Barnard) adult male. A. Habitus (specimen 1), lateral view; B. Habitus (specimen 2), lateral view; C. Caudal Ramus (specimen 1); D. Caudal Ramus (specimen 2). E. Antennule; F. Antenna; G. Maxillule; H. Maxilla; I. Maxilliped. Scale bars: A, B, E, F 100 µm; C, D, G, H, I 50 µm.