Phylum: Arthropoda, Crustacea Megalorchestia pugettensis Class: Malacostraca Order: Amphipoda, Gammaridea A beach hopper Family: Talitridae Taxonomy: Some species of the genus coastal beaches, particularly at night Megalorchestia, including M. pugettensis, (Bousfield 2007). Megalorchestia species are were originally described as members of characterized by a short and stocky body, Orchestoidea (e.g. O. pugettensis) (Bousfield small eyes and short antennae (for key see 2007). These talitrid sand hoppers were Bousfield 1982). divided into two groups: 4-dentate species Cephalon: from the southern hemisphere (Orchestoidea) Rostrum: Rostrum rounded and and 5-dentate species from the northern simple. hemisphere (Megalorchestia) by Brandt in Eyes: Eyes large and oval in shape 1851 (Bousfield 1982). Megalorchestia (Fig. 1). species-level designations are currently in Antenna 1: Short and slightly shorter need of further study as M. columbiana and than the third article of second antenna, M. pugettensis likely contain at least three especially in males (Fig. 1) (Barnard 1975). species each (Bousfield 1982). Antenna 2: Massive peduncle of three articles that are, together, longer than Description the flagellum, especially in males (Fig. 1) Size: Individuals up to 18 mm in length, (Barnard 1975). Flagellum of about 20 excluding antennae (Bowers 1964). The articles. illustrated specimen (from Coos Bay) is 17 Mouthparts: Mandible without palp mm in length. (Talitridae) and maxilliped article four not well Color: White, usually with three spots on last developed. (Mouthparts not figured, see three coxae. The color pattern is particularly Traskorchestia traskiana in this guide). useful in Megalorchestia species identification Pereon: (see Fig. 3, Bowers 1963). In particular, there Coxae: The coxae, or first pereopod are distinctive antero-posterior markings on article, has first plate ½ as large as second the last three thoracic segments in M. plate (Fig. 1). pugettensis (see Fig. 4B, Bowers 1963). Gnathopod 1: In both sexes, the first General Morphology: The body of gnathopod is simple and not subchelate. The amphipod crustaceans can be divided into strong dactyl is adapted for digging (Fig. 2) three major regions. The cephalon (head) or (Barnard 1975). Translucent processes cephalothorax includes antennules, antennae, (“blisters”) are present on articles three and mandibles, maxillae and maxillipeds six. (collectively the mouthparts). Posterior to Gnathopod 2: Large and subchelate the cephalon is the pereon (thorax) with in males (Figs. 1, 3) and simple in females seven pairs of pereopods attached to (not figured, more like gnathopod one). pereonites followed by the pleon (abdomen) Pereopods 3 through 7: Pereopod with six pairs of pleopods. The first three sets six longer than seven (Fig. 1). of pleopods are generally used for swimming, Pleon: while the last three are simpler and surround Pleonites: Pleonites five and six the telson at the animal posterior. Talitrid separate, not fused (Talitridae). Anteroventral amphipods are in the suborder Gammaridea, margin of pleonite one is with 1–7 spines (Fig. one of the largest groups of amphipods in 1). Three biramous pleopods (with small marine and estuarine habitats. They have breathing organs within pleosome) and the smooth bodies that are only slightly third pleopod is about equal in size to first and compressed, are commonly called beach second (not figured). hoppers and can be highly abundant on Hiebert, T.C. 2015. Megalorchestia pugettensis. 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. A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12722 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Urosomites: Three pairs of uropods: and the pleopod rami are short. Sexual 1) outer branch with marginal spines (Fig. 4) dimorphism is strong in M. californiana and and no interramal spine (not figured) and males have enlarged second gnathopods inner branch with double row of spines; 2) and elongated antennae with peduncle that outer branch without spines on inner is orange to red in color (Iyengar and Starks margin(Figs. 5, 6); 3) one branch (Talitridae) 2008). Megalorchestia californiana is often and ramus broad distally and about as long found with the smaller congener, M. as peduncle (Fig. 6) (Barnard 1975). benedicti (Bousfield 2007). Megalorchestia Epimera: benedicti is a small species (9–13 mm), and Telson: Telson spinose, notched at is found on fine sand beaches. Its pleonites posterior-most tip (Figs. 1, 6, 7) and is often have 1–5 spines on their posterior margins, lost in collecting. making it potentially confused with M. Sexual Dimorphism: Second gnathopods pugettensis. Its telson is notched, however, very large and powerful in males, but simple and it lacks the characteristic translucent in females and young. blister on the sixth article of the male gnathopod of M. pugettensis. Possible Misidentifications Megalorchestia corniculata, another large The Talitridae are a family of gammarid species, is found on short stretches of amphipods called beach hoppers and are coarse sand beaches with lots of protection ubiquitous in damp sands, where they live (Bowers 1963), seaweed and a steep slope. within clumps of seaweed. They survive well It has short second antennal flagella and in air. Talitridae are characterized by a single spineless inner margins on the outer rami of branched third uropod (Figs. 1, 4) and a its second uropods, like M. pugettensis. mandible without a palp (not figured, see However, it has an entire, not a notched, Traskorchestia traskiana in this guide). Nine telson, and no spines on the margin on its local talitrid species are currently reported first pleonites. Megalorchestia columbiana, (Bousfield 2007) including six Megalorchestia, found on coarse sand beaches with little two Traskorchestia and one Transorchestia seaweed, has long second antennal flagella species. Some authors differentiate and no spines on the margins of its Megalorchestia species as sand hoppers pleonites. Unlike M. californiana, it has no (intertidal on sandy beaches), while translucent process on female gnathopod Traskorchestia species as beach fleas one and its pleopod rami are ½ to ¾ the (intertidal in coastal leaf-litter) (Bousfield length of the peduncle. It can be as long as 1982; Pelletier et al. 2011). 22 mm (Bowers 1964). Finally, M. minor is a The genus Megalorchestia are found primarily southern species with distribution on exposed beaches and are usually larger that is rarely north of San Simeon near Point than Traskorchestia. Species in the latter Conception. Individuals are found on surf- genus have subchelate first gnathopods, not exposed sandy beaches and are up to 15 simple ones, and slender first gnathopod mm in length (Bousfield 1982, 2007). dactyls, not heavy ones. The seventh pereopods are also longer than the sixth, Ecological Information while the reverse is true in Megalorchestia. Range: Information on the range of M. The third uropods narrows and branches in pugettensis is unknown outside the west Traskorchestia, but is not broad. coast of North America (e.g. central California Megalorchestia californiana, is the to Alaska, Bousfield 1982, 2007). largest species in the Puget Sound area and Local Distribution: Coos Bay distribution in (Kozloff 1974) is found on long stretches several locations along the South Slough and beaches with fine sand, high in the intertidal open coastal beaches. (Bowers 1963). It has a second antenna Habitat: Under debris on coarse sand with a long flagellum (males), spines on the beaches with little seaweed (Barnard 1975). inner margin of the outer rami of the second Sand hoppers (Megalorchestia species) are uropod. The females have a translucent differentiated from beach fleas process on article five of the first gnathopod (Traskorchestia species) in that the former Hiebert, T.C. 2015. Megalorchestia pugettensis. 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. group tend to modify their habitat substrate, Food: Scavenges detritus from beach debris. while the latter does not (Bousfield 1982). The closely related M. californiana and M. Salinity: corniculata are omnivorous, macrophzgrous, Temperature: and partial to seaweed (e.g. Macrocystis and Tidal Level: Above tide level, likes Saccorhiza, Lastra et al. 2008), wet dampness, but avoids complete immersion in cardboard and the bodies of other arthropods. seawater. However, individuals avoid putrefied matter. Associates: Rhabditid nematodes are found Predators: Shorebirds and other birds (e.g. under the dorsal pereonites in M. californiana Varied Thrushes, Ixoreus naevius, Egger and M. corniculata (Rigby 1996). Talitrid 1979). Talitrid amphipods are prey for a amphipods also host and transport mites of variety of intertidal and terrestrial predators Uropodina, Dermanyssina and Acaridida and it has been suggested that they represent (Pugh et al. 1997). a trophic link between the detritus of beach Abundance: Not as common as wrack and terrestrial ecosystems (via Pacific Traskorchestia traskiana in Coos Bay. herring,