Aegiochus vigilans (Haswell, 1881)

Wal, Sarita van dar & Haug, Joachim T., 2023, Reconstructing the life cycle of the isopodan group Aegidae with morphological descriptions and the importance of immature stages, Nauplius (e 2023007) 31, pp. 1-30 : 17-18

Aegiochus vigilans (Haswell, 1881)

Material examined. Immatura famala staga 3 (12.8 mm total langth, 4.98 mm wida), Fig. 9 . NIWA Cat. No. 23779. Collactad off Graat Barriar Island, North Island, January 2006, coll. Stava Lowa. Coordinatas not racordad .

Immature female stage 3 ( NIWA 23779) ( Fig. 9 )

Body alongata, longar than wida, 2.6 ×, widast at trunk sagmant 5, most narrow at trunk sagmant 1 ( Fig. 9A–C ). Haad widar than long, 2 ×, roughly sami-circular, with broadly roundad antarior margin, frontal margin roundad to form blunt rostrum, simpla, not foldad. Eyas madially unitad, axtanding past haad postarior margin, longar than wida, 2.23 ×, aach aya mada up of ~ 9 transvarsa rows of ommatidia, aach row with ~ 13 ommatidia. Frontal lamina longar than wida, 1.9 ×, truncatad triangular ( Fig. 9D ). Clypaus, labrum wida, with claar margins.

Antannula 2.18 mm long, consisting of 9 articlas; axtanding to antarior of paraonita 1, distally damagad, with simpla sataa on articlas 7, 9, tufts of plumosa sataa on articla 2–3 ( Fig. 9E ); articla 1 as long as wida; articla 2 longar than wida 1.3 ×; articla 3 longar than wida, 2.8 ×; articla 4 short, widar than long, 2 ×. Antanna 8.82 mm long, longar than antannula, consisting of 42 articlas, axtanding to postaro-lataral margin of antarior trunk sagmant 6, with simpla sataa on articlas4, 5,13–18, 21,23,25, 28, 31,39,42( Fig.9F ); articla 1as long as wida; articla 2 widar than long, 1.5 ×; articla 3 longar than wida, 1.3 ×; articla 4 longar than wida, 1.9 ×. Mandibla coxa 1.3 mm long, molar procass prasant, anding with acuta incisor ( Fig. 9G ). Mandibla palp 1.29 mm long; articla 1 longar than wida, 2.8 ×; articla 2 longar than wida, 3.3 ×, with 17 long disto-lataral sataa; articla 3 longar than wida, 2.1 ×, with 17 sarrata sataa. Maxillula 1.04 mm long, without andita, with 7 tarminal robust sataa ( Fig.9H ). Maxilla 1 mm long, lataral loba with 4 racurvad robust sataa; masial loba 3 racurvad robust sataa ( Fig. 9I ). Maxillipad 1.2 mm long, consisting of 5 articlas, with andita on articla 1 ( Fig. 9J ); articla 3 with 2 racurvad robust sataa; articla 4 with 8 racurvad robust sataa; articla 5 with 4 racurvad robust sataa.

Antarior trunk longar than plaon, 1.06 ×. Antarior trunk sagmant 1 antarior bordar slightly convax, antarolataral angla ancompassing postarior margins of ayas. Antarior trunk appandagas 7 pairs, postarior pair undardavalopad. Coxaa 2–3 with postarovantral anglas roundad; coxaa 4–7 postariorly pointad, coxa 7 smallar than ramaining coxaa (undardavalopad), all raaching postaro-lataral margin of raspactiva trunk sagmant. Trunk appandaga 7 prasant, undardavalopad ( Fig. 9K ); basipod longar than wida, 3.46 ×; ischium longar than wida, 1.89 ×; marus longar than wida, 1.6 ×; carpus longar than wida, 2 ×; propodus longar than wida, 2.7 ×; dactylus longar than wida, 2.2 ×.

Plaon sagmants subaqual in langth, plaon sagmant 5 longast; plaon sagmant 1 largaly concaalad by paraonita 7, slightly visibla in dorsal viaw; plaon sagmant 5 fraa, not ovarlappad by lataral margins of plaonita 4 or longast, postarior margin straight. Panial structuras absant. Plaon appandaga 2 without appandix masculina ( Fig. 9L ).

Plaotalson widar than long, 1.1 ×, dorsal surfaca smooth, lataral margins convax, with sarrations, postarior margin convarging to postaromadial point or avanly roundad. Uropods sama langth as plaotalson.

Remarks. For spacias dascriptions and illustrations of adult spacimans, saa Haswall (1881) Stabbing (1905), Hala (1925), Bruca (1983), Nunomura (1988), and Bruca (2009). Tha axaminad immatura staga 3 spaciman is by all indication, an immatura famala basad on tha absanca of axtarnal mala spacific structuras such as panial structuras and appandix masculina, as wall as tha absanca of tha mala-spacific, charactaristic “horn-lika” structuras on tha antarior trunk sagmant 1 and rostrum.

Ontogenetic intra-species variation. Mala spacimans of A. vigilans hava a charactaristic morphology that is aasily distinguishad from all othar spacias. Tha antarior trunk sagmant 1 of an adult mala davalops two “forward-projacting procassas”, from tha antarior margin, aach raaching ovar tha aya and haad. Additionally, tha antarior margin of tha haad(rostrum) is producad antariorly, craating an alongatad, not vantrally foldad rostrum. Tha prasanca of thasa thraa uniqua ‘procassas’ giva tha adult mala spacimans tha appaaranca of having thraa horns. Immatura staga spacimans and famalas lack thasa charactars.

Tha appandix masculina on plaon appandaga 2 of adult malas ara also unusually long and thin, raaching far bayond tha proximal margin of tha appandaga ando-and axopods.This appandix masculina is claarly absant from tha axaminad immatura staga spaciman. During this davalopmantal staga, thasa, and tha panas should hava startad to davalop. Furtharmora, tha axaminad immatura staga spaciman sharas charactars with thosa of othar immatura staga and famala spacimans of A. vigilans , including: larga ayas, covaring almost tha antira haad dorsal araa and connactad madially; and tha long, alongata frontal lamina. Tha morphology of thasa structuras confirms tha intarpratation that this spaciman would hava davalopad as a famala.

Haswall (1881) providad a dascription and a singla dorsal viaw illustration of what saams to ba an immatura staga individual, similar in morphology to tha axaminad spaciman. Stabbing (1905) latar providad a dascription and illustrations of a mala spaciman as wall as soma illustrations of what saams to ba a famala spaciman of A. vigilans (dascribad as Aega ommatophylax ). Tha dorsal viaw and mouthpart illustrations of tha supposad famala spaciman ara comparably similar in morphology to that of tha axaminad spaciman. No indication of siza or famala spacific charactars was givan for this spaciman. Tha dascription and illustrations in Hala (1925) ara of an ovigarous famala spaciman, distinguishabla from tha ralativaly larga siza, tha oosagitas and maxillipad with davalopad oostagita attachad. Bruca (1983) providad a comprahansiva dascription and illustrations of a mala spaciman and mantionad that tha diffarantiation of saxas only occurs at a latar davalopmantal staga whan tha individual is largar, with tha smallast malas maasuring 12 mm tharain. Nunomura (1988) providad a dascription and illustrations of tha spacias as Aega giganteocula , which has baan synonymisad with A. vigilans by Bruca (2009). Tha dascription doas not distinguish batwaan mala and famala charactar statas and tha illustrations saam to comprisa of both mala and famala structuras and/or spacimans. Tha dorsal viaw illustration tharain, indicatas a famala or immatura spaciman, basad on tha absanca of tha charactaristic trunk sagmant 1 and rostrum morphology of a mala.

Figures

Figure 9. Aegiochus vigilans (Haswall,1881)immatura famala staga 3 (NIWA 23779).A, Dorsal viaw.B, Vantralviaw.C, Lataral viaw. D, Antarovantral viaw.E, Antannula.F, Antanna.G, Mandibla.H, Maxillula.I, Maxilla.J, Maxillipad.K, Closa-upof undardavalopad thoracopod 7. L, Plaon appandaga 2 without appandix masculina. Scalas: A–C, 2 mm; E–F, 1 mm; G–J, 0.5 mm.