Jassa morinoi Conlan 1990
Creators: name: Conlan, Kathleen E.
name: Desiderato, Andrea
name: Beermann, Jan
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Ischyroceridae
Jassa
Jassa morinoi

description: Jassamorinoi Conlan, 1990
(Table 10, Figs 28–30)
Diagnosis.
Both sexes:
Mandibular palp: article 2, dorsal margin without a 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 short setae at the distal angle; carpus with a single or small cluster of long setae at the anterodistal junctionof the propodus (setae Ẑ50% the length of the anterior margin length andslightly medial).
Gnathopod 2: basis with about 5–10 widely spaced, short setae along the anterolateral margin (length of most setae <40% 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 1/3 of the longest ramus.
Uropod 3: inner ramus without spines mid-dorsally (with only the single apical spine).
Telson: tip with apical setae in addition to 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 pronounced and produced on a ledge in large minor form males. Palmar defining spines absent in major form males. Thumb distally acute in both minor and major males and sinuous in major males. The dactyl is proximally expanded but not centrally toothed in minor forms.
Adult female:
Antenna 2: without plumose setae on the flagellum and peduncular article 5.
Gnathopod 2: propodus, palm concave, palmar defining angle acute.
Remarks. Jassa morinoi, J. valida and J. monodon are unique among the species of Jassa in having a seta or group of setae at the tip of the telson which extend between the third uropods as a horizontal extension of the body. This apical seta or setae can be most easily seen when the third uropods are held downward. The apical setae should not be confused with the usual upright seta or setae that accompany each telson knob on each lateral edge in every species of Jassa. The three species can be told apart by the length (if present) or absence of the diagnostic seta or cluster of setae at the anterodistal junction of the carpus and propodus of gnathopod 1. This seta or setal cluster is slightly medial in J. morinoi and J. valida and absent in J. monodon. Care must be taken to twist the gnathopod 1 to check for this seta on the medial face of the propodus as it may lay flat against the propodus and therefore be obscured from view. This seta or setal cluster is long in J. morinoi (length as great as the width of the gnathopod 1 basis) but much shorter in J. valida, to the extent that it may not be visible at low magnification (length << the width of the gnathopod 1 basis).
Jassa morinoi can also be confused with J. slatteryi as both can co-occur in collections and both have the long seta(e) at the anterodistal junction of the carpus and propodus of gnathopod 1. The key character separating these species at any age or sex is the presence of the apical seta or setae on the telson in J. morinoi and absence in J. slatteryi.
Jassa morinoi has been found widely, dating as far back as 1885 in the Mediterranean Sea (Table 3). An illustration of two specimens of Jassa (named “ J. falcata ”) by Ledoyer (1986), collected from Madagascar (Thomassin st. 270, microatolls of Sarodrano, 23°30′30ʺS, 43°44′00ʺE) and Thomassin st. 263, microatolls of Songoritelo, 23°14ʹS, 43°37ʹE) shows key features that suggest that the specimens are J. morinoi (telson tip with long setae, gnathopod 2 basis with sparse setae, male antenna 2 flagellum not plumose). However, the long seta(e) at the junction of carpus and propodus of gnathopod 1 is not shown or described, leaving the identification suggestive but not certain. Jassa morinoi is known from neighbouring South Africa.
The earliest collection record for J. morinoi on the coast of Pacific North America is 1909 near the (then) remote village of Ucluelet on British Columbia’s exposed outer coast of Vancouver Island. It may be indigenous on the Pacific North American coast because it has been found frequently on exposed coasts away from harbours. For this study, it is known from 38 Pacific North American collections, ranging from Athlone Island, British Columbia (52°N) to Santa Catalina Island, California (33°N). Some “ J. slatteryi ” listed in Conlan (1990), from Pacific North America were found to be mis-identified and were actually J. morinoi. However, re-examination of the entire NMNS/CMN collection of “ J. slatteryi ” found that J. slatteryi does indeed occur on this coast and the two species can be found mixed together in aggregate collections. The re-examination of the NMNS/CMN collection also revealed that some of the major form males previously thought to be J. slatteryi were actually J. morinoi. Illustrations of some of these newly found major forms have been added to Fig. 28 along with the minor form male previously thought to be a major form in Conlan (1990). Therefore, like most of the other species of Jassa, the major form of J. morinoi can lose its palmar defining spines, although this does not always happen, as shown in Fig. 28.
Afirst discovery of “ J. morinoi ” in the southwestern Gulf of Mexico by Winfield et al. (2021) is questionable as it is more likely J. valida (Supplementary Data File S1). It is apparent from their identification criteria that they were not aware of the key character that separates the species (setal length at the anterodistal junction of carpus and propodus). Winfield et al. (2021) were also identifying relatively small specimens (3.03 ± 0.46 mm body length, n = 3) which may have been difficult to manipulate in order to view this seta. It was not possible to borrow the specimens to confirm the identification as the museum collections were closed due to the COVID-19 pandemic.
Specimens of J. morinoi noted in Conlan (1990) as lent by Dr. H. Morino, Ibaraki University, Japan, have been recently transferred to the National Museum of Nature and Science, Tsukuba, Japan. This includes the type specimens (Morino 2019).
description: Published as part of Conlan, Kathleen E., Desiderato, Andrea & Beermann, Jan, 2021, Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus, pp. 1-191 in Zootaxa 4939 (1) on pages 60-64, DOI: 10.11646/zootaxa.4939.1.1, http://zenodo.org/record/4580622