Jassaherdmani Walker, 1893

Conlan, Kathleen E., Desiderato, Andrea & Beermann, Jan, 2021, Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus, Zootaxa 4939 (1), pp. 1-191 : 87-92

Jassaherdmani Walker, 1893

( Table 11 , Figs 48–53 )

Synonyms: see Conlan (1990).

Diagnosis.

Both sexes:

Mandibular palp: article 2, dorsal margin witha fringe of setae.

Maxilla 1: without a seta or setal cluster at the base of the palp article 1.

Gnathopod 1: basis, anterolateral margin with a few very short setae; carpus without a single or small cluster of setae at the anterodistal junction of the propodus.

Gnathopod 2: basis with a few minute setae along the anterolateral margin but without long filter setae (setal lengths <20% of the basis width); carpus and propodus, setae on the anterior margin short and simple (setal length <basis width).

Pereopods 5–7: propodus not expanded anteriorly.

Uropod 1: ventral peduncular spinous process underlying about 40% of the longest ramus.

Uropod 3: inner ramus without spines mid-dorsally (with only the single apical spine).

Telson: tip without apical setae, only the usual short setae at each dorsolateral cusp.

Thumbed male:

Antenna 2: without plumose setae on the flagellum and peduncular article 5.

Gnathopod 2: propodus, palmar defining spines absent except in small males. Thumb distally acute or squared in minor males and squared in major males. Dactyl centrally toothed in minor forms and shallowly expanded proximally in major forms.

Adult female:

Antenna 2: without plumose setae on the flagellum and peduncular article 5.

Gnathopod 2: propodus, palm concave, palmar defining angle acute, distal to but close to the defining spines.

Remarks. The neotype ( Fig. 48 ), which was erected by Conlan (1990), is a minor form male with short thumb and toothed dactyl, corresponding with “The specimen originally described as P. herdmani , taken by Professor Herdman from a Compound Ascidian off the Island of Bute...” ( Walker 1911, p. 71). Jassa herdmani naturally co-occurs with J. falcata and J. marmorata but the three species differ in microhabitat selection, life cycle, reproduction and temperature adaptation ( Beermann & Franke 2012; Beermann & Purz 2013). The identity of the three species can be easily confused, especially when small ( Sexton & Reid 1951; Conlan 1990). Conlan (1990) outlines how these can be distinguished on the basis of the antenna 2 plumosity, gnathopod 1 and 2 shape and setation and uropod 3 inner ramus spination.

Fig. 49 shows the thumb length relationships among specimens collected later by D.M. Reid from Plymouth Harbour on April 14, 1937. Although the collection was small, different morphologies of the minor and major form adult male are evident and the subadult male has a small pre-thumb before it molts into a (probably major form) thumbed male, judging by its large body length. Sexton and Reid (1951) called this pre-thumbed stage of the subadult male the “cut-across stage”. Reproductions of Sexton and Reid’s (1951) figures that are confirmed J. herdmani are shown in Figs 50 and 51 . These specimens were collected in Plymouth Harbour at various dates between 1928 and 1930 and kept in aquaria, where changes in their morphologies were recorded as they molted. The transformation of the subadult male 13D to major form thumbed male 13E (their labels) is shown in Fig. 51 . They mistook these specimens as J. falcata , calling them the ʺNarrow Form” of J. falcata . The females of the two species also differ subtly, with the palmar angle of the gnathopod 2 propodus more bulbous and farther from the defining spines in J. falcata ( Fig. 44 ) than in J. herdmani ( Figs 51 , 52 ).

The dactyl toothing appears to vary with thumb length. In the minor form with short, distal thumb ( Figs 48 and 49 ), the dactyl tooth is pronounced. In the major form with longer, more proximal thumb ( Fig. 51 , specimen 13E), the dactyl tooth is shallower and more proximal. In the large major form with a long, proximal thumb ( Figs 48 , 49 and 51 , specimen 1), the dactyl is expanded proximally, rather than more centrally toothed. One of the key features for J. herdmani is the cluster of setae on the dorsal margin of the mandibular palp article 2. This is shown in Fig. 53 .

One specimen noted in Lobo et al. (2017) as being Jassa sp. is J. herdmani (specimen examined 4 March 2019). This is likely the Jassa sp. in their Fig. 2 that matches other specimens of J. herdmani from the North Sea in their CO1-5P sequence.

The finding of a single juvenile female in coral rubble at Aqaba, Jordan by Lyons and Myers (1991) (identification confirmed) places the range of J. herdmani far outside the northeast Atlantic coast and western Mediterranean Sea where it has most often been collected ( Fig. 9 ). This suggests that J. herdmani may have a propensity for exotic dispersal similar to J. marmorata , J. slatteryi and J. morinoi . It commonly fouls offshore structures in the North Sea (oil and gas platforms, wind turbines and shipwrecks) ( Coolen et al. 2018; Luttikhuizen et al. 2019) which are thought to supply extended shallow, hard substrate and it has been collected on buoys ( Sexton and Reid 1951) and boat bottoms as far back as 1890 (NHM 1925.9.8:1602). The Suez Canal is a transportation route for many exotic species, resulting in the eastern Mediterranean having many more introductions than the western Mediterranean ( Galil et al. 2015). Lyons and Myers (1991) suggest that J. herdmani may be on the Atlantic coast of central Africa as well. This is based on literature reports that have not been confirmed by examination of specimens. Possibly these reports refer to J. marmorata or J. morinoi which are confirmed there ( Figs 1 , 2 , 5 and 6 ).

Figures

FIGURE 1. Progressive discovery of Jassa marmorata from 1850 to 1949. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 2. Progressive discovery of Jassa marmorata from 1850 to 2020. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 5. Progressive discovery of Jassa morinoi from 1850 to 1949. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 6. Progressive discovery of Jassa morinoi from 1850 to 2020. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 9. Records of Northern Hemisphere species of Jassa that were found in the eastern and/or western North Atlantic and seas, along with J. kimi in the western Pacific. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 44. Jassa falcata (Montagu, 1808). Adult male 1, major form, 11.0 mm; juvenile male 2, 7.0 mm; adult male 3, major form, 6.5 mm; juvenile male 4, 4.5 mm; and adult female, 7.0 mm. Stoer Bay, Sutherland, Scotland, 22 October 1937, D. M. Reid, coll., very abundant on the floats of coastal salmon nets (SNM). Developing new cuticle is visible inside the propodus and dactyl of the juvenile male 2 gnathopod 2, not yet at the terminal molt as the new cuticle lacks a thumb. All views medial. Scale 0.1 mm.

FIGURE 48. Jassa herdmani (Walker, 1893). Neotype, adult male, minor form, 6.0 mm, NHM 1925.9.8: 1686. Port Erin breakwater, Isle of Man, England, November 1892, A. O. Walker, coll.Adult male 1, major form, 7.9 mm, 1 m below water surface on steel frame used to hold settling plates, Langstone Harbour, Plymouth, England, 26 March 1986, R. J. Trott, coll., IZ1986-041 (CMN). Lateral view: whole body; dorsal view: telson; other views medial. Scale 0.1 mm. Illustration after Conlan (1990).

FIGURE 49. Jassa herdmani (Walker, 1893). Variation in thumb length relative to body length in males from Plymouth Sound, England, 14 April 1937, D. M. Reid, coll., from a buoy (SNM).Arrows refer to the associated gnathopod illustrations. The subadult male had a thumb visible inside the cuticle, indicating that it would molt next into a thumbed adult. Setae omitted except for those around the thumb and spines in order to landmark position changes with growth. All views lateral. Scale 0.1 mm. Linear regression assumptions failed for all plots. Illustration after Conlan (1990).

FIGURE 50. Jassa herdmani (Walker, 1893). Adaptation of illustrations in Sexton and Reid (1951), with their figure numbers indicated. Antennae 1 (1A) and 2 (1B), gnathopod 1 (1C) pereopods 3–7 (1E, F, G, H, J): Plates 6-9, Specimen 1, Narrow-Form male J.CCLXXIII, from Trinity Buoy, Plymouth Docks, 14 May 1928, E. W. Sexton and D. W. Reid, colls.

FIGURE 51. Jassa herdmani (Walker, 1893). Adaptation of illustrations in Sexton and Reid (1951), with their figure numbers indicated. Adult female gnathopod 2: Plate 10, Specimen 2, Narrow-Form female J.CXLIV (2E), dredging from a buoy at the entrance to Plymouth Docks, 23 August 1928, E. W. Sexton and D. W. Reid, colls. Juvenile male gnathopod 2: Plate 12, Specimen 7, Narrow-Form male, cut-across stage, J.5 (1): F1 of female J.CXLIV (7C). Transformation of non-thumbed (13D) to thumbed (13E) gnathopod 2: Plate 19, Specimen 13 (2), Male K. B. 11, from a scrape of a buoy moored outside the [Plymouth] Breakwater, 3 May 1930, E. W. Sexton and D. W. Reid, colls. Adult male gnathopod 2, major form: Plate 7, Specimen 1, Narrow-Form male J.CCLXXIII, from Trinity Buoy, Plymouth Docks, 14 May 1928, E. W. Sexton and D. W. Reid, colls.

FIGURE 52. Jassa herdmani (Walker, 1893). Adult female, 7.2 mm, 1 m below water surface on steel frame used to hold settling plates, Langstone Harbour, Plymouth, England, 26 March 1986, R. J. Trott, coll., IZ1986-041 (CMN). Lateral view: whole body; dorsal view: telson; other views medial. Scale 0.1 mm.

FIGURE 53. Jassa herdmani (Walker, 1893).Adult male 1, major form, 7.9 mm, 1 m below water surface on steel frame used to hold settling plates, Langstone Harbour, Plymouth, England, 26 March 1986, R. J. Trott, coll., IZ1986-041 (CMN). Mouthparts. Lateral views: maxilla 1 and maxilla 2; frontal view: upper lip; other views medial. Scale 0.1 mm.