Ampithoe Valida Class: Multicrustacea, Malacostraca, Eumalacostraca

Phylum: Arthropoda, Crustacea Ampithoe valida Class: Multicrustacea, Malacostraca, Eumalacostraca Order: Peracarida, Amphipoda, Senticaudata, A gammarid amphipod Corophiida, Corophiidira Family: Corophioidea, Ampithoidae Description Antenna 2: Size: Both illustrated specimens (from Coos Mouthparts: Lower lip with a notch be- Bay), a male and female, were 10 mm in tween the sublobes and outer lobes (Fig. 5) length. Size range up to 12.5 mm (Ampithoidae, Barnard 1965) and sublobes (Chapman 2007). are compressed. Mandible is with a large Color: Green with black chromatophores palp and an obvious rasping surface (Fig. 2). and red eyes. Pereon: General Morphology: The body of amphi- Coxae: Coxa one extended anteriorly, pod crustaceans can be divided into three particularly coxal plate one (Fig. 1) (Barnard major regions. The cephalon (head) or 1965). cephalothorax includes antennules, anten- Gnathopod 1: Male gnathopod article nae, mandibles, maxillae and maxillipeds five has a distal projection and is slightly lon- (collectively the mouthparts). Posterior to ger than article six. Article two is very setose the cephalon is the pereon (thorax) with and article six has an oblique angle to the seven pairs of pereopods attached to pere- palm (Fig. 3). The gnathopod palm in females onites followed by the pleon (abdomen) with is also oblique (not figured). six pairs of pleopods. The first three sets of Gnathopod 2: Male gnathopod articles pleopods are generally used for swimming, two and three have large rounded lobes. Ar- while the last three are simpler and surround ticle five is with a narrow hind lobe, article six the telson at the animal posterior. Am- is elongate, rectangular, with a transverse pithoid amphipods are in the suborder gam- palm and a quadrate middle bump and dactyl maridea, one of the largest groups of amphi- (article seven) is curved (Fig. 4). Female pods in marine and estuarine habitats. They gnathopod two is like female gnathopod one have smooth bodies that are only slightly (palm oblique), but stouter. compressed (Conlan and Bousfield 1982). Pereopods 3 through 7: Keys to the Ampithoidae generally refer to Pleon: male specimens, although sexual dimor- Pleonites: phism may be weaker in this group than oth- Urosomites: All three urosomites short ers (Chapman 2007). and the first two have spines (Fig. 1). Uropod Cephalon: one is with a vestigial peduncular process. Rostrum: Third uropods are with two hooks on the stout Eyes: outer ramus (Barnard 1965) and the inner ra- Antenna 1: The first and second mus is flattened, with bristles (Kozloff 1974) antennae are of equal length in males (Fig. (Fig. 6). 1), but the first antenna is slightly longer in Epimera: The second and third females. Both first and second antennae epimera are rounded, with very slight points bear a few setae, but no spines (Barnard (Barnard 1965) (Fig. 1). 1965). No accessory flagellae are present. Telson: Telson is blunt and with small knobs A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] 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. at posterior corners (Fig. 6). comes from its large pointed process or Sexual Dimorphism: Among amphipods, thumb which meets the dactyl (the sixth arti- males generally have larger eyes, antennae cle of the second gnathopod in males). Am- and gnathopods (Straude 1987). Sexual di- pithoe aptos has two enlarged lobes on the morphism in A. valida is pronounced in the apex of the teslon and the fifth article of pe- antennae and gnathopods, particularly the reopod five is less than half as long as the second gnathopods (Alonso et al. 1995), sixth. On the other hand, Ampithoe sectima- and species determination must be made nus has a telson with small knobs and the from male specimen. fifth article of pereopod five is more than half as long as the sixth. Ampithoe dalli has plu- Possible Misidentifications mose setae on the anterior edge of the se- The Ampithoidae are a family of cond article of gnathopod one (in males). gammarid amphipods characterized by Ampithoe longimana is North Atlantic spe- short third uropods and rami that possess 1 cies, introduced to southern California, and -2 distinctive and stout hooks on the outer A. ramondi is a cosmopolitan species that is ramus (Myers and Lowry 2003). They are currently not reported farther north than Point usually sexually dimorphic and males are Conception, California. Neither of these spe- easier to identify than females. They are cies are found in current local intertidal keys herbivorous and live in nests they create (Chapman 2007). amongst algal blades or within algae stipes. Ampithoe lacertosa, another common There are 10–11 local species in the genus local species found in estuaries, is very simi- Ampithoe (A. corallina is currently a ques- lar in appearance to A. valida. It differs tionable species, Chapman 2007), which chiefly in its lower lip, which gapes. The an- are generally larger than other amphipod tennae are unequal in A. lacertosa, the first genera (Kozloff 1993). See Conlan and being longer than the second. The sixth arti- Bousfield (1982) for detailed account of cle of the second gnathopod is transverse Ampithoe characters. and sinous, but lacks the central bump pre- Ampithoe simulans is also found in sent in A. valida. The fifth article of gnatho- marine intertidal habitats of Coos Bay pod one also lacks the distal projection pre- (Barnard 1965). This species has an sent in A. valda. oblique and concave article on the second gnathopod, not a transverse one. This Ecological Information article has a large sinus, and a small Range: Type locality is Long Island Sound in process on its inner margin (Barnard 1954). the North Atlantic (Alonso et al. 1995). This species is primarily found on the open Known Pacific range includes British Colum- coast and lives within Phyllospadix spp. bia to southern California and also Japan and other types of algae (Chapman 2007). (Carlton 1979) and Korea (Alonso et al. Ampithoe plumulosa, as its name suggests, 1995). Range on Atlantic coast extends from has a very setose second antenna and the New Hampshire to Chesapeake Bay (Carlton first antenna is very long. The lower lips 1979). This species is native to the Atlantic gape and are not compressed as they are coast and was introduced to the western in A. valida. This likely introduced species coast (Chapman 2007). The range of this and is often found in mussel beds species was recently extended as far south as (Chapman 2007). Ampithoe pollex does Quequen and Chubut Argentina (Alonso et al. have compressed lower lips and its name 1995). Recent genetic analysis of northeast A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Pacific A. valida populations suggests three gate embryos with water flow produced by distinct lineages that may represent three pleopod movement. Development within this cryptic species. Furthermore, these line- brood chamber is direct and individuals hatch ages suggest three separate introductions to as juveniles that resemble small adults, with the western coast of the United States (see no larval stage. The embryos of A. valida are Figs. 4–5, Pilgrim and Darling 2010). oval in shape, white to yellow in color, fe- Local Distribution: Coos Bay sites in South males produce 2–3 broods each year and the Slough (Barnard 1954), especially in the number of embryos per brood may (Alonso et Metcalf Preserve. al. 1995) or may not be (Pardal et al. 2000) Habitat: Tube dweller amongst eelgrass positively correlated with adult female body (Barnard 1975) and green and red algae size. Although many amphipod species ex- (Alonso et al. 1995), especially hibit an extended coupling period (e.g. Hyale Enteromorpha and Ulva spp. habitats. (This pugettensis, Straude 1987), where males and specimen built a tube in lab petri dish.) females are physically coupled for several Ampithoe valida is a biofouling organism, days prior to copulation, there is no such peri- and is often found on floats, pilings and od in A. valida individuals. Instead, males docks (Chapman 2007; Pilgrim and Darling and females inhabit the same nest, although 2010). males may visit the nests of many different Salinity: Collected at salinities as low as 5 females (“cruising males”, Borowsky 1983). and occurs in brackish waters. Aspects of the developmental biology of A. Temperature: valida, were described by Barrett (1966). Fe- Tidal Level: Collected at + 0.15 m MLLW male broods range in number from 3–60 and found subtidally at depths up to 30 m (average 22) eggs which are 460 µm in diam- (Chapman 2007). eter. At 8–10˚C, individuals hatch at 10 days Associates: Associates in South Slough post fertilization, but remain in the female include the introduced corophiid amphipod, brood pouch for another 4 days. This timeline Grandidierella japonica, and the sacoglos- increases at warmer temperatures (e.g. 7 and san, Aplysiopsis enteromorphae (=smithi). 4 days at 12–15˚C) (Heller 1968; Barrett Abundance: Locally common and abundant 1966). Barrett (1966) found that brood size in South Slough. In Argentina, abundance more accurately correlates to pereon length of A. valida was highest in the summer (not total body length). Reproductive charac- months with 727 individuals per 0.125 ters of the congener, A.

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