Archaeomysis Grebnitzkii Subphylum: Crustacea Class: Malacostraca a Mysid Or Opossum Shrimp Order: Mysida Family: Mysidae

Phylum: Arthropoda Archaeomysis grebnitzkii Subphylum: Crustacea Class: Malacostraca A mysid or opossum shrimp Order: Mysida Family: Mysidae

Taxonomy: Archaeomysis grebnitzkii was biramous, antennae have a long scale (or described from a specimen collected from cod squama), pleopods are often reduced, gut contents by Czerniavksy in 1882. Later, thoracic legs bear swimming exopodites and Holmes described the same species under a uropods are lamellar and form tail fan. different name, Callomysis maculata, which Mysids are easily distinguished from other was collected from a sandy beach (Holmquist Peracardia by the presence of a statocyst on 1975). In 1932, Tattersall transferred C. the uropod endopods (see Plate 220, Moldin maculata to A. maculata and Holmquist 2007; Vicente et al. 2014; Fig. 1, Meland et al. (1975) synonymized Archaeomysis maculata 2015). and Callomysis maculata as A. grebnitzkii, a Cephalon: (see also Figs. 3–4, Hanamura species which exhibited a wide North Pacific 1997). range (Hanamura 1997; Moldin 2007). These Carapace: Attached to first two or species were previously differentiated by three thoracic segments and free dorsally at subtle variation in morphological characters posterior edge (Banner 1948) (Figs. 1, 1a). that were deemed to be intraspecific (e.g. Posterior margin with rounded lateral lobes rostrum shape, third pleopod exopod (Archaeomysis, Banner 1948) and no fringe segments, telson length, Hamanura 1997). or ornamentation. Carapace pronounced anteriorly into a short rostrum (Fig. 2). Description Rostrum: Rostrum length shorter Size: Male body length ranges from 9–15 than eyestalk (Fig. 2) and can be grooved, mm, and females 13–22 mm (Holmquist bent down slightly, or rounded (Holmquist 1975; Hanamura 1997). The illustrated 1975). ''Shortly produced”, according to specimens (from Columbia River) are 4.5 mm original genus description (Archaeomysis, (male, Fig. 1a) and 17 mm (female, Fig. 1). Holmquist 1975). Color: Transparent, with stellar Eyes: Large, movable, stalked, with melanophores (“maculate”) (see Fig. 265, black corneas and somewhat pear shaped. Kozloff 1993). Some mysids can change Eye and eyestalk less than twice as long as color to blend with their background broad (Fig. 2). Visual pigment absorbances (Tattersall and Tattersall 1951). were measured for A. grebnitzkii at 496 nm, General Morphology: Mysids are shrimp- which phylogenetically placed this species like crustaceans that are occasionally called within a shorter-wavelength spectral opossum shrimp due to the female sensitivities species clade (Porter et al. 2007). marsupium or brood pouch, which is Antennae: Almost as long as body composed of oostegites. Like other and with slender multi-articulate flagellum Peracarida (e.g. cumaceans, isopods, (Fig. 1). The peduncle has three joints and is amphipods, tanaids), their bodies are longer than its antennal scale, but shorter elongated and composed of an anterior than the antennular peduncle (Fig. 2). cephalon and pereon (thorax, covered by a Antennule peduncle with first joint about equal carapace), and a pleon (abdomen). At the in length to remaining joints combined. The posterior end, they have a telson and second joint is with two spines on the outer uropods. Among the Mysidacea specifically, margin (Tattersall 1951) (Fig. 2). the carapace is attached to the thorax by Antennae Scale: (= squama) anterior segments only and the posterior Extends to distal end of second penducular dorsal edge is free (Banner 1948) (Fig. 1). joint and is 3½ times as long as broad. Sclae Mysid eyes are stalked, antennules are with straight outer margin, without setae

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12692 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] (Archaeomysis, Banner 1948), with strong Hanamura 1997). The first pleopod is with an terminal spine, and weak or absent distal elongate protopodite, with basal and distal suture. On anterior and inner margins, scale tufts of long setae, the endopod is longer than is setose only (no spines) (Kozloff 1974) (Fig. the exopod, and more than ½ as long as 2). protopodite (Fig. 6). The second pleopods Mouthparts: For general mouthpart are with short protopodite and exopod, and a morphology for the Mysida see Fig. 3, Meland longer endopod (Fig. 7). The third, fourth and et al. 2015. Labrum longer than broad fifth female pleopods are like the second, but (Tattersall and Tattersall 1951) and with with shorter endopods. strong frontal spiniform process Telson: Telson with distinct apical cleft (Archaeomysis, Banner 1948). (Mauchline 1980) and margins of cleft are Pereon: denticulate (Banner 1948) (Fig. 8). Total Pereopods: Pereopods without well- length is 2½ times as long as broad (at base). developed gills (Mysida, Banner 1948). First Eight to nine spines are present on each leg with exopodite, second leg without a lobe- margin, the last two spines are long, strong, like process on merus. Pereopod 3–8 with and close together (Fig. 8) (See Fig. 7, carpopropodus (carpus and propodus fused) Meland et al. 2015; see Fig. 5, Hanamura of endopod that is divided into many 1997). subjoints: 9–11 in females (Fig. 3), 7–9 in Uropods: Uropods biramous, with neither males (not figured). Exopods in both male branch articulate (Banner 1948). Both rami and female legs 3–8 has a basal joint with an with setae on the distal margin acute outer distal corner (Fig. 3). No (Archaeomysis, Banner 1948). The endopod branchiae are present on thoracic legs is longer than the exopod, with statocyst near (Mauchline 1980). base, and two basal spines (Fig. 8). Six Pleon: Fifth pleonite with a small medial spines are present on the inner edge in projection and sixth with corresponding ridge males, seven in females (Banner 1948). The (Fig. 5). In females, the lateral pleura on the exopod is truncate, without suture (Mauchline first somites help form the brood pouch (Fig. 1980), with 14 (male) to 17 (female) lateral 1). Inconspicuous pleura are present on spines on outer margin (more than 10, somites 3–5, none on six (Banner 1948). Archaeomysis). No setae on the outer Pleopods: Male pleopods variable exopod margin (Banner 1948). (Mysida, Mauchline 1980) and all are Statocyst: Light and balance organ on biramous. The first is with a uniarticulate endopod of uropod (Fig. 8). It is found in all endopod and multi-articulate exopod (Banner neritic and in common oceanic mysids 1948) of 7–9 articles (Holmquist 1975) and (Banner 1948) and distinguishes mysids from the third is with elongate exopod larval decapods (Green 1968). (Archaeomysis, Banner 1948) (Fig. 1a, 4). Sexual Dimorphism: Pleopod morphology The second pleopod with endopod of 4–7 varies between males and females. Mature articles, exopod of 8–9 articles, the third is females are also recognizable by the with elongate copulatory exopod of 8–10 presence of oostegites that form a thoracic articles, endopod of 5 articles (Holmquist brood pouch with two pairs of lamellae 1975) (Fig. 4), and the fourth is with exopod (Mauchline 1980). These oostegites arise of 5–9 articles (Holmquist 1975). The from the seventh and eighth pereopods illustrated fourth male pleopod has 7 articles (Mauchline 1980) to form marsupium (Fig. 1). (Fig. 5), endopod a simple plate, the fifth pleopod is like the fourth, but shorter, and Possible Misidentifications with 4–8 exopod articles (Holmquist 1975) Mysidacea and Euphausiacea, being (see also Fig. 4, Hanamura 1997). superficially similar in appearance, are often Female pleopods are ''usually treated together (e.g. Banner 1948; degenerate"' (i.e. reduced) (Mysida, Mauchline 1980). (They were formerly Mauchline 1980) and all are biramous combined as the Schizopoda.) Both are (Archaeomysis, Mauchline 1980) with each orders of the class Malacostraca, but ramus of one small article (see also Fig. 3, euphausiids are in the group (i.e.

Hiebert, T.C. 2015. Archaeomysis grebnitzkii. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Species, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR. superorder) Eucarida with the Decapoda Archaeomysis (each with a single species (Martin 2007). Like the mysids, euphausiids represented locally) (Moldin 2007). differ from decapods in having biramous Alienacanthomysis macropsis is thoracic legs (Kasaoka 1974). Unlike the recognizable by elongated eyestalks and mysids, euphausiids have a carapace that is Deltamysis holmquistae has spines on the fused dorsally with all the thoracic lateral telson margins, but only distally, segments. The mysid carapace is attached where other species have spines all over only to the first two or three thoracic the telson margins or in proximal groups. segments. Furthermore, mysid females Alienacanthomysis macropsis, has a have oostegites, but euphausiids do not. broadly triangular rostrum with long acute Other orders of Peracarida include lateral carapace spines and its telson has a lsopoda, Tanaidacea, and Amphipoda, fringe of small spines. It is abundant in San which are all fairly easily distinguished from Francisco Bay and becomes rarer farther Mysidacea. One order that might be north (Holmquist 1979). It has been confused is Cumacea, small crustaceans of reported from Yaquina Bay to lower up to ½ inch long, with an inflated, shrimp- Columbia River and in Puget Sound in bays like carapace (see Cumella vulgaris, this amongst Ulva and in plankton (Kozloff guide), a single compound recessed eye 1974a). (except for some eyeless females of some Archaeomysis japonica was described species), and a flexible, tubular abdomen. in 1996 by Hanamura et al. and was Mysids characteristically have large, previously considered A. grebnitzkii. stalked, movable eyes, and well developed However, the two species differ in the exopodites on their thoracic legs. Mature endopod of the third pleopod, which is females have oostegites forming a segmented in A. japonica (males, marsupium. Additionally, northeast Pacific Hanamura et al. 1996). mysids lack thoracic gills, have reduced Archaeomysis grebnitzkii has spines pleopods in females (and sometimes in along the lateral margins of uropod males). They also have a statocyst on the exopods, which is not seen in other species. inner ramus of the uropod. Of the species without lateral exopod Mysicadea is divided into two suborders, spines, Hippacanthomysis platypoda has a the Mysida and Lophogastrida. The former flattened exopod of fourth pleopod (males). suborder comprises coastal and intertidal Holmesimysis costata and E. davisi have species while the latter includes mostly distinctly segmented pleonites, the former large, pelagic and deep sea mysids. These has a broadly triangular telson while the suborders are easily differentiable by the latter has a telson that is sharply triangular. presence of branchial gills, biramous Holmesimysis was extracted from pleopods and the lack of statocysts in Acanthomysis (Holmquist 1979). Its Lophogastrida (branchia are absent, members have fourth male pleopods with pleopods are reduced and statocysts are only two segments and on the tip are two conspicuous in the Mysida) (Moldin 2007). spiny peg-like structures (Mauchline 1980). Archaeomysis grebnitzkii belongs to the Holmesimysis costata, the type species for Mysida, lacking gills or branchiae on the the genus, has a short, bluntly rounded thoracic legs (Fig. 3) and having rather antennal scale. reduced female pleopods. Columbiaemysis, Acanthomysis, Within the Mysicadea locally, there are Neomysis and Hyperacanthomysis species 15 species comprising the following genera: have pleonites that are smooth and without Acanthomysis and Neomysis (comprising distinct folds or segments. Neomysis three species and four species, species have a pointed distal tip of the respectively), and Hyperacanthomysis, antennal scale (see Fig. 3, Neomysis Alienacanthomysis, Columbiaemysis, mercedis, this guide) and members of the Deltamysis, Exacanthomysis, remaining genera have a distal antennal Hippacanthomysis, Holmesimysis, and scale tip that is rounded. There are several Pacific species of the genus Neomysis (all

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12692 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] with pointed apex on the antennal scale, Oregon) as well as intertidally and at low two pairs of female oostegites, statocyst on water on ocean beaches. Juveniles may be the uropod endopod, and male fourth more common higher in the intertidal, while pleopods biramous). For differentiating larger individuals (i.e. adults) can be found in Neomysis species, see N. mercedis (this deeper habitats, offshore (Llewellyn et al. guide). Columbiaemysis ignota has been 1981; Takahashi and Kawaguchi 1995). described from female specimens only, and Associates: only from British Columbia. Its antennal Abundance: The most common mysid of the scale is long, setose all around, and has a northeastern Pacific, followed by Neomysis suture. Its telson is tongue shaped, with mercedis (see this guide) (Holmquist 1975). spines becoming dense at the tip, and two The most abundant and common species long spines at the rounded apex. There are collected in hyperbenthic sledge samples at four spines on the lower edge of the Bastendorff Beach, Charlsteson, Oregon with statocyst. approximately 3200 individuals per square meter (Marin Jarrin and Shanks 2011). Ecological Information Range: Type locality is Bering and Life-History Information Commandor Islands in the Bering Sea Reproduction: All development takes place (Hanamura 1997). Known range in northern within the female marsupium and is Pacific (Holmquist 1975) from Urup Island and lecithotrophic and proceeds through three northern Sakhalin to southwest Alaska and distinct stages: 1) the embryonic stage; 2) the Bering Sea, to Washington, Oregon, and the first nauplioid stage (eyeless larva); and northern California (see Fig. 25, Hanamura 3) the post-naplioid (eyed larva) stage to a 1997). juvenile (see Figs. 38.1–38.2, Vicente et al. Local Distribution: Locally present in 2014). Copulation in A. grebnitzkii occurs at estuaries of Coos Bay, Yaquina Bay, lower- night and lasts only a few seconds (Mauchline Columbia River and also along the open 1980). Sperm is shed into female brood coast. pouch and the female then lays eggs, which Habitat: Primarily littoral, buried in sand with are immediately fertilized (Mauchline 1980) a mixture of pebbles and boulders on both and 510 x 480 µm (a 13 mm long female, open ocean coast and in inland waters. In Hanamura 1997). Early embryos are mud and with the alga Zostera as well as with spherical or sub-spherical. Young develop to Phyllospadix and kelp intermixed (Holmquist a subadult stage in the brood pouch, and 1975). Burrows in bottom substratum, and emerge from external genital openings of rises to surface of water at night, especially oviducts near the bases of the sixth thoracic during the breeding season (Mauchline 1980; legs (Mauchline 1980). The number of eggs Tattersall and Tattersall 1951). Individuals depends on size of female and embryos and very sensitive to oxygen reduction (Green in temperate and high latitudes on season, 1968; Jawed 1973). but not on temperature (Mauchline 1980). Salinity: Quite variable, from fresh water to Brood size in the closely related genus salinities of 34 (Holmquist 1975). However, Gastrosaccus, can vary seasonally, with salinity figures could refer to surface, and the largest broods produced in early summer and species is an inhabitant of the saltier, bottom a female G. vulgaris, of similar in size to A. water (Holmquist 1975). grebnitzkii (17 mm long), had 100 embryos Temperature: A wide temperature tolerance, per brood (Mauchline 1980). Numbers of ranging from 8.5 °C or lower to 24 °C. broods/year is not definitely known for A. (Holmquist 1975). grebnitzkii, but the most shallow-living neritic Tidal Level: Predominantly intertidal and and littoral mysid species usually have three also found in shallow waters close to shore broods year, including the closely related (Holmquist 1975). Moves up and down with Gastrosaccus at a comparable latitude the rising and falling tide. Occurs at extreme (Japan, Mauchline 1980). Chromosome low tide level (Puget Sound, Washington, counts for A. grebnitzkii were 2n=10, plus an Banner 1948) and subtidal (Coos Bay, extra small chromosome (Holmquist 1975).

Hiebert, T.C. 2015. Archaeomysis grebnitzkii. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Species, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR. Sex ratios vary within populations, but food for filtering, mysids will balance, head females frequently outnumber males down, on antennal scales and inner flagella of (Mauchline 1980). antennulae, and create currents with thoracic Larva: The first nauplioid stage has exopods. They can also "plow" the bottom appendages that resemble the typical with their scales and flagellae (Cannon and nauplius larva (see Balanus glandula, this Manton 1927 in Mauchline 1980). South guide), but lacks an eye or swimming setae. African Gastrosaccus species feeds most The next post-nauplioid stage has all adult often at night (Mauchline 1980). appendages, carapace and eyes. Both Predators: Fish are the most common and stages are non-motile and lecithotrophic. most important predators (Tattersall and Ultimately, the post-nauplioid molts into a Tattersall 1951; Haertel and Osterberg 1967) free-living juvenile (Vicente et al. 2014). as well birds (e.g. eider duck in Aleutians), Larval development time depends on shrimp, ctenophores, squid, and possibly temperature. In G. vulgaris, developmental cetaceans and seals. This species is also duration is 10.9–25 days (Matsudaira et al. in eaten by humans or used as fish bait in some Mauchline 1980). parts of the world (e.g. India, Tattersall and Juvenile: Juveniles are simply miniature Tattersall 1951). Archaeomysis grebnitzkii adults at post-emergence molt, when they are was the dominant prey of the bay shrimp, usually 1.5–3.0 mm long (Mauchline 1980). Lissocrangon stylirostris (see description in Longevity: Mysids will probably live 12 –18 this guide) at night (Marin Jarrin and Shanks months in temperate water and over two 2008, 2011). years in the Arctic (Tattersall and Tattersall Behavior: Locomotion is by exopods of 1951). No longevity rates known for A. thoracic legs as pleopods are often reduced, grebnitzkii. In overwintering generations, and not locomotory. Motion is rotary and most individuals are born in autumn, a few in unceasing. An "escape mechanism” is also summer, and fewer in winter. Spring breeding observed in A. grebnitzkii, where a sudden is intensive and females may produce two downward flex of abdomen and tail fan broods. Spring generations reproduce in the causes the individual to spring backward and summer (possibly twice), and usually die by even leap out of water (Tattersall and autumn (Mauchline 1980). Tattersall 1951) or through mud (Mauchline Growth Rate: Growth among isopods occurs 1980). While this has not been shown in A. in conjunction with molting where the grebnitzkii, females of some mysid species exoskeleton is shed and replaced. Post-molt will recapture escaped larvae and return them individuals will have soft shells as the cuticle to their marsupium (Mauchline 1980). Larvae gradually hardens. During a molt, arthropods can belong to other individuals or to other have the ability to regenerate limbs that were species. Males will eat escaped larvae previously autonomized (Kuris et al. 2007). (Mauchline 1980). Mysids avoid bright light Mysids generally take about one year to attain (Tattersall and Tattersall 1951), but are full growth and are sexually mature in attracted to weak light sources and fishing considerably less time (Tattersall and lures (Mauchline 1980). Archaeomysis Tattersall 1951). Females usually grow larger grebnitzkii did not respond to atmospheric than males (Mauchline 1980) and the number pressure changes of 0.1 atm (Mauchline of instars is fewer than for most crustaceans. 1980). Other burrowers (e.g. Gastrosaccus) The first and second occur in the marsupium, have pronounced diel vertical migration where and 10 or more occur after the release of individuals remain within the substrate during young (Mauchline 1980). the day and are pelagic at night. Burrowing Food: Feeds either on living or dead material mysids are reotaxtic and face into water that is picked up by thoracic endopods, or current. They may move offshore to avoid (more commonly) on fine suspended matter breaking waves and waves can also wash filtered by thoracic exopods. Danish them out of their burrows (Mauchline 1980). Gastrosaccus species, also bottom dwellers, eat detritus, algae, copepods and amphipods (Tattersall and Tattersall 1951). To stir up

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12692 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Bibliography Washington, and British Columbia. University of Washington Press, 1. BANNER, A. H. 1948. A taxonomic Seattle. study of the Mysidacea and 11. KURIS, A. M., P. S. SADEGHIAN, J. Euphausiacea (Crustacea) of the T. CARLTON, and E. CAMPOS. 2007. northeastern Pacific. Part I. Decapoda, p. 632-656. In: The Light Mysidacea, from family and Smith manual: intertidal Lophogastridae through tribe invertebrates from central California to Erythropini. Transactions of the Royal Oregon. J. T. Carlton (ed.). University Canadian Institute. 26. of California Press, Berkeley, CA. 2. GREEN, J. 1968. The biology of 12. LLEWELLYN, J., D. L. HIGLEY, and estuarine animals. University of R. L. HOLTON. 1981. The life history Washington Press, Seattle. of the beach dwelling mysid 3. HAERTEL, L., and C. OSTERBERG. Archaeomysis grebnitzkii. Estuaries. 1967. Ecology of zooplankton, 4:281-281. benthos and fishes in the Columbia 13. MARIN JARRIN, J. R., and A. L. River estuary. Ecology. 48:459-472. SHANKS. 2008. Ecology of a 4. HANAMURA, Y. 1997. Review of the population of Lissocrangon stylirostris taxonomy and biogeography of (Caridea: Crangonidae), with notes on shallow-water mysids of the genus the occurrence and biology of its Archaeomysis (Crustacea: Mysidacea) parasite, Argeia pugettensis (Isopoda: in the North Pacific Ocean. Journal of Bopyridae). Journal of Crustacean Natural History. 31:669-711. Biology. 28:613-621. 5. HANAMURA, Y., S. G. JO, and M. 14. —. 2011. Spatio-temporal dynamics of MURANO. 1996. A new species of the surf-zone faunal assemblages at a Archaeomysis from coastal waters of southern Oregon sandy beach. Marine Japan (Mysidacea, Gastrosaccinae). Ecology. 32:232-242. Crustaceana. 69:553-566. 15. MARTIN, J. W. 2007. Arthropoda, p. 6. HOLMQUIST, C. 1975. A revision of 411-414. In: The Light and Smith the species Archaeomysis grebnitzkii manual intertidal invertebrates from Czernaivsky (sic) and A. maculata Central California to Oregon. J. T. (Holmes) (Crustacea, Mysidacea). Carlton (ed.). University of California Zoologische Jahrbücher. Abteilung für Press, Berkeley. Systematik, Ökologie und Geographie 16. MAUCHLINE, J. 1980. The biology of der Tiere. 102:51-71. mysids and euphausiids. Advances in 7. JAWED, M. 1973. Effects of marine biology. 18:1-681. environmental factors and body size 17. MELAND, K., J. MEES, M. PORTER, on rates of oxygen consumption in and K. J. WITTMANN. 2015. Archaeomysis grebnitzkii and Taxonomic review of the orders Neomysis awatschensis (Crustacea, Mysida and Stygiomysida (Crustacea, Mysidae). Marine Biology. 21:173-179. Peracarida). Plos One. 10. 8. KASAOKA, L. D. 1974. The male 18. MOLDIN, R. F. 2007. Mysidacea, p. genital system in two species of mysid 489-495. In: The Light and Smith crustacea. Journal of Morphology. manual: intertidal invertebrates from 143:259-283. Central California to Oregon. J. T. 9. KOZLOFF, E. N. 1974. Keys to the Carlton (ed.). University of California marine invertebrates of Puget Sound, Press, Berkeley, CA. the San Juan Archipelago, and 19. PORTER, M. L., T. W. CRONIN, D. A. adjacent regions. University of MCCLELLAN, and K. A. CRANDALL. Washington Press, Seattle. 2007. Molecular characterization of 10. —. 1993. Seashore life of the northern crustacean visual pigments and the Pacific coast: an illustrated guide to evolution of pancrustacean opsins. northern California, Oregon,

and Iiella ohshimai, in Otsuchi Bay, northeastern Japan. Marine Ecology Progress Series. 116:75-84. 21. TATTERSALL, W. M. 1951. The Mysidacea of the United States National Museum. Bulletin of the United States National Museum:1-292. 22. TATTERSALL, W. M., and O. S. TATTERSALL. 1951. The British Mysidacea. Ray Society, London. 23. VICENTE, C. S., G. GUERAO, and J. OLESEN. 2014. Lophogastrida and

Mysida, p. 200-205. In: Atlas of crustacean larvae. M. J.W., J. Olesen, and J. T. Høeg (eds.). Johns Hopkins University Press, Baltimore.