Ampithoe Valida Class: Malacostraca Order: Amphipoda, Gammaridea a Gammarid Amphipod Family: Ampithoidae

Phylum: Arthropoda, Crustacea Ampithoe valida Class: Malacostraca Order: Amphipoda, Gammaridea A gammarid amphipod Family: Ampithoidae Description Coxae: Coxa one extended Size: Both illustrated specimens (from Coos anteriorly, particularly coxal plate one (Fig. 1) Bay), a male and female, were 10 mm in (Barnard 1965). length. Size range up to 12.5 mm (Chapman Gnathopod 1: Male gnathopod article 2007). five has a distal projection and is slightly Color: Green with black chromatophores and longer than article six. Article two is very red eyes. setose and article six has an oblique angle to General Morphology: The body of the palm (Fig. 3). The gnathopod palm in amphipod crustaceans can be divided into females is also oblique (not figured). three major regions. The cephalon (head) or Gnathopod 2: Male gnathopod cephalothorax includes antennules, antennae, articles two and three have large rounded mandibles, maxillae and maxillipeds lobes. Article five is with a narrow hind lobe, (collectively the mouthparts). Posterior to article six is elongate, rectangular, with a the cephalon is the pereon (thorax) with transverse palm and a quadrate middle bump seven pairs of pereopods attached to and dactyl (article seven) is curved (Fig. 4). pereonites followed by the pleon (abdomen) Female gnathopod two is like female with six pairs of pleopods. The first three sets gnathopod one (palm oblique), but stouter. of pleopods are generally used for swimming, Pereopods 3 through 7: while the last three are simpler and surround Pleon: the telson at the animal posterior. Ampithoid Pleonites: amphipods are in the suborder gammaridea, Urosomites: All three urosomites one of the largest groups of amphipods in short and the first two have spines (Fig. 1). marine and estuarine habitats. They have Uropod one is with a vestigial peduncular smooth bodies that are only slightly process. Third uropods are with two hooks compressed (Conlan and Bousfield 1982). on the stout outer ramus (Barnard 1965) and Keys to the Ampithoidae generally refer to the inner ramus is flattened, with bristles male specimens, although sexual dimorphism (Kozloff 1974) (Fig. 6). may be weaker in this group than others Epimera: The second and third (Chapman 2007). epimera are rounded, with very slight points Cephalon: (Barnard 1965) (Fig. 1). Rostrum: Telson: Telson is blunt and with small knobs Eyes: at posterior corners (Fig. 6). Antenna 1: The first and second Sexual Dimorphism: Among amphipods, antennae are of equal length in males (Fig. males generally have larger eyes, antennae 1), but the first antenna is slightly longer in and gnathopods (Straude 1987). Sexual females. Both first and second antennae dimorphism in A. valida is pronounced in the bear a few setae, but no spines (Barnard antennae and gnathopods, particularly the 1965). No accessory flagellae are present. second gnathopods (Alonso et al. 1995), and Antenna 2: species determination must be made from Mouthparts: Lower lip with a notch male specimen. between the sublobes and outer lobes (Fig. 5) (Ampithoidae, Barnard 1965) and sublobes Possible Misidentifications are compressed. Mandible is with a large The Ampithoidae are a family of gammarid palp and an obvious rasping surface (Fig. 2). amphipods characterized by short third Pereon: uropods and rami that possess 1–2 Hiebert, T.C. 2015. Ampithoe valida. 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/1794/12691 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] distinctive and stout hooks on the outer differs chiefly in its lower lip, which gapes. ramus (Myers and Lowry 2003). They are The antennae are unequal in A. lacertosa, usually sexually dimorphic and males are the first being longer than the second. The easier to identify than females. They are sixth article of the second gnathopod is herbivorous and live in nests they create transverse and sinous, but lacks the central amongst algal blades or within algae stipes. bump present in A. valida. The fifth article There are 10–11 local species in the genus of gnathopod one also lacks the distal Ampithoe (A. corallina is currently a projection present in A. valda. questionable species, Chapman 2007), which are generally larger than other Ecological Information amphipod genera (Kozloff 1993). See Range: Type locality is Long Island Sound in Conlan and Bousfield (1982) for detailed the North Atlantic (Alonso et al. 1995). account of Ampithoe characters. Known Pacific range includes British Ampithoe simulans is also found in Columbia to southern California and also marine intertidal habitats of Coos Bay Japan (Carlton 1979) and Korea (Alonso et al. (Barnard 1965). This species has an oblique 1995). Range on Atlantic coast extends from and concave article on the second New Hampshire to Chesapeake Bay (Carlton gnathopod, not a transverse one. This 1979). This species is native to the Atlantic article has a large sinus, and a small coast and was introduced to the western process on its inner margin (Barnard 1954). coast (Chapman 2007). The range of this This species is primarily found on the open species was recently extended as far south coast and lives within Phyllospadix spp. and as Quequen and Chubut Argentina (Alonso et other types of algae (Chapman 2007). al. 1995). Recent genetic analysis of Ampithoe plumulosa, as its name suggests, northeast Pacific A. valida populations has a very setose second antenna and the suggests three distinct lineages that may first antenna is very long. The lower lips represent three cryptic species. Furthermore, gape and are not compressed as they are in these lineages suggest three separate A. valida. This likely introduced species and introductions to the western coast of the is often found in mussel beds (Chapman United States (see Figs. 4–5, Pilgrim and 2007). Ampithoe pollex does have Darling 2010). compressed lower lips and its name comes Local Distribution: Coos Bay sites in South from its large pointed process or thumb Slough (Barnard 1954), especially in the which meets the dactyl (the sixth article of Metcalf Preserve. the second gnathopod in males). Ampithoe Habitat: Tube dweller amongst eelgrass aptos has two enlarged lobes on the apex of (Barnard 1975) and green and red algae the teslon and the fifth article of pereopod (Alonso et al. 1995), especially Enteromorpha five is less than half as long as the sixth. and Ulva spp. habitats. (This specimen built a On the other hand, Ampithoe sectimanus tube in lab petri dish.) Ampithoe valida is a has a telson with small knobs and the fifth biofouling organism, and is often found on article of pereopod five is more than half as floats, pilings and docks (Chapman 2007; long as the sixth. Ampithoe dalli has Pilgrim and Darling 2010). plumose setae on the anterior edge of the Salinity: Collected at salinities as low as 5 second article of gnathopod one (in males). and occurs in brackish waters. Ampithoe longimana is North Atlantic Temperature: species, introduced to southern California, Tidal Level: Collected at + 0.15 m MLLW and A. ramondi is a cosmopolitan species and found subtidally at depths up to 30 m that is currently not reported farther north (Chapman 2007). than Point Conception, California. Neither Associates: Associates in South Slough of these species are found in current local include the introduced corophiid amphipod, intertidal keys (Chapman 2007). Grandidierella japonica, and the sacoglossan, Ampithoe lacertosa, another Aplysiopsis enteromorphae (=smithi). common local species found in estuaries, is Abundance: Locally common and abundant very similar in appearance to A. valida. It in South Slough. In Argentina, abundance of Hiebert, T.C. 2015. Ampithoe valida. 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. valida was highest in the summer months days post fertilization, but remain in the with 727 individuals per 0.125 square meter female brood pouch for another 19 days size (Alonso et al. 1995). In Portugal, A. valida (Heller 1968). densities showed a direct and positive Larva: Since most amphipods are direct correlation with areas of nutrient enrichment, developing, they lack a definite larval stage. where abundances were up to 2026 Instead this young developmental stage individuals per square meter in areas of high resembles small adults (e.g. Fig. 39.1, Wolff eutrophication (Pardal et al. 2000). 2014). Juvenile: Immature females can be Life-History Information differentiated from mature females by the Reproduction: Most amphipods have presence of a brood pouch and associated separate sexes with some sex determination setae for securing embryos (Alonso et al. correlated with environmental conditions 1995). Males reach sexual maturity earlier (Straude 1987). Females brood embryos in than females (compare 24–44 days with 28– an external thoracic brood chamber and 61 days, Pardal et al. 2000). irrigate embryos with water flow produced by Longevity: Range from 191–242 days pleopod movement. Development within this (Pardal et al. 2000). brood chamber is direct and individuals hatch Growth Rate: Amphipod growth occurs in as juveniles that resemble small adults, with conjunction with molting where the no larval stage. The embryos of A. valida are exoskeleton is shed and replaced. Post-molt oval in shape, white to yellow in color, individuals will have soft shells as the cuticle females produce 2–3 broods each year and gradually hardens (Ruppert et al. 2004). the number of embryos per brood may Ampithoe valida grows at a rate of 1 mm per (Alonso et al.

Load more