Neomysis japonica is a Mysid crustacean native to the Northwest Pacific, from central Japan to the South China Sea. Mysids are small, shrimplike crustaceans, which tend to divide their time between epibenthic habitats and the plankton. It has been introduced to San Francisco Bay, California and New South Wales, Australia. The abundance and distribution of N. japonica in San Francisco Bay is poorly known because of taxonomic confusion with N. kadakiensis. It is found in estuaries and lagoons and has been recorded within ballast water from commercial ships.
Image Credit: Julius Fürst (1861-1938), under the US public domain tag. Please note that this is a generic mysid image and not species specific.
|Bioregion||Region Name||Year||Invasion Status||Population Status|
|P090||San Francisco Bay||2004||Def||Estab|
|NEP-V||Northern California to Mid Channel Islands||2004||Def||Estab|
|P093||_CDA_P093 (San Pablo Bay)||2004||Def||Estab|
Mysids are small, shrimplike crustaceans, with a cape-like carapace which covers the head and thorax, but which is not attached to the last four thoracic segments. A pair of spherical statocysts is located at the base of the inner uropods. Adult females have a ventral brood pouch (Barnes 1983; Modlin in Carlton 2007).
Neomysis japonica has a carapace with its front edge broadly rounded, reaching slightly beyond the base of the antennules and just covering the inner part of the base of the eye-stalks. The posterior edge of the carapace is curved forward, exposing parts of thoracic segments 7 and 8. The eyes are large and about 1 2/3 X as long as broad. The abdominal segments are smooth, without furrows or folds. The antennal scale is 9 X as long as wide, with the apex sharply pointed, with a distal joint comprising about 1/5 of the total length. The 4th pleopod of the male has an elongated exopodite, with the 1st joint 6 X the length of the second. The telson is roughly triangular, about 2 1/2 X as long as its greatest width and lined with about 35-40 small spines, with two larger terminal spines at the tip, flanking a pair of median small spines. The spines are more widely spaced at the proximal end of the telson and more closely spaced. The largest individuals are about 13 mm long (Ii 1964; Modlin in Carlton 2007).
In San Francisco Bay, N. japonica was confused with N. kadiakensis. The latter is characteristic of deeper, more saline bays and inlets, whereas N. japonica is more characteristic of estuaries. Neomysis japonica is likely to co-occur with the native N. mercedis, which was formerly very abundant in upper San Francisco estuary (Ii 1964; Modlin in Carlton 2007).
The mysid Neomysis japonica is native to coastal waters and estuaries of the Northwest Pacific, from the South China Sea to the Bohai and Yellow Seas and the east and west coasts of central Japan (Ii 1964). It has been introduced to San Francisco Bay, California (Cohen et al. 2005; Modlin in Carlton 2007) and New South Wales, Australia (Hutchings et al. 1986).
Neomysis japonica was first definitively identified from the Petaluma River, California, a tributary of San Pablo Bay in 2004 (Cohen et al. 2005; Modlin in Carlton 2007). In 1996, a mysid, then identified as the native N. kadiakensis, appeared in the Sacramento-San Joaquin Delta and Suisun Bay, occurring in low abundances, roughly equal to those of the formerly dominant native N. mercedis. This was probably N. japonica, but characters for separating these species were not known at that time (Baxter and Hieb 2006). Similarly, some or even all of the 'N. kadiakensis' comprising 94-99% of the mysids caught at China Camp, San Pablo Bay in 2002-2005 (Dean et al. 2005) may have been N. japonica. At this time, the range and abundance of N. japonica in the San Francisco estuary is unknown.
Neomysis japonica was collected and found to be breeding in the Hunter River, New South Wales, Australia (Hutchings et al. 1986; Lowry and Stoddart 2003). Williams et al. (1988) found this mysid in ballast water from Japanese ships in Australian harbors. We have no further information on the occurrence of this animal in Australian waters.
Mysids are small, shrimplike crustaceans, which tend to divide their time between epibenthic habitats and the plankton, sometimes migrating diurnally, or else making brief swims between benthic habitats. Males have a pair of penes located at the junction of the thorax and abdomen, and modified pleopods used for the transfer of spermatophores, in N. americana this is pleopod 5. Adult females have a brood pouch, and give birth to juveniles, resembling miniature adults (Barnes 1983; Modlin, in Carlton 2007).
The abundance and distribution of Neomysis japonica, in San Francisco Bay, is poorly known because of taxonomic confusion with N. kadakiensis. In Japan, it is 'abundant in the brackish water along the Pacific coast of Japan and is also very common in the estuaries and lagoons'( Ii 1964). In the Chikugo River estuary, Japan, it was common between 1 and 10 PSU, but was also common in the outer estuary at 10-20+ PSU (Suzuki et al. 2009). In the Petaluma River, it was collected at 8-10 PSU (Cohen et al. 2005). This mysid is probably most abundant in low-salinity estuarine habitats in the upper San Francisco estuary. Mysids may be epibenthic feeders, suspension feeders, predators, or omnivores (Barnes 1983). Members of the genus Neomysis are omnivorous feeders (Johnson and Allen 2005).
Fishes, decapod shrimps
|General Habitat||Unstructured Bottom|
|General Habitat||Salt-brackish marsh|
|Salinity Range||Oligohaline||0.5-5 PSU|
|Salinity Range||Mesohaline||5-18 PSU|
|Salinity Range||Polyhaline||18-30 PSU|
|Salinity Range||Euhaline||30-40 PSU|
|Minimum Temperature (ºC)||8||Chikugo River estuary, Japan (Suzuki et al. 2009)|
|Maximum Temperature (ºC)||30||Chikugo River estuary, Japan (Suzuki et al. 2009)|
|Minimum Salinity (‰)||1||Chikugo River estuary, Japan (Suzuki et al. 2009)|
|Broad Temperature Range||Cold-temperate-Warm temeprate|
|Broad Salinity Range||Oligohaline-Euhaline|