Phylum: Arthropoda, Crustacea Class: Multicrustacea, Malacostraca, Eumalacostraca Caprella drepanochir Order: Peracarida, Amphipoda, Senticaudata, A skeleton shrimp, or caprellid amphipod Corophiida, Caprelldira Family: Caprelloidea, Caprellidae, Caprellinae Taxonomy: The Caprellidae are a very dis- the telson at the animal posterior. Caprellid tinctive family of amphipods. They were pre- amphipods differ from the rest of amphipoda viously a separate amphipod suborder, but in that the abdomen is greatly reduced, espe- were recently found to be polyphyletic, aris- cially the last three abdominal segments ing at least twice from different gammarid (urosome) and associated appendages amphipod lineages (Laubitz 1993; Takeychi (uropods). Their body is also elongated ra- 1993; Watling and Carlton 2007). Current ther than laterally compressed (compare to research places them as highly modified gammarid amphipods, e.g. Eogammarus con- members of the suborder Corophiidea fervicolus) (Kozloff 1993; Watling and Carlton (Myers and Lowry 2003; Watling and Carlton 2007). 2007), a taxon divided into two infraorders Cephalon: Round cephalon with no dorsal (Caprellida, Corophiida) each with different spines or tubercles (Fig. 1) (Laubitz 1976), evolutionary feeding strategies and associat- however body spination is a highly variable ed morphology (Myers and Lowry 2003). trait among individuals (Watling and Carlton 2007). Head partially fused with the first Description pereonite (segment of pereon) and the first Size: The illustrated specimens (from Coos pair of gnathopods (Fig. 1). Pereonite one not Bay) include a 13 mm long male (Fig. 1) and more than twice as long as head in male an 8 mm long female (Fig. 2) (Measured (Laubitz 1970) and shorter in female (Laubitz from anterior (head) to posterior (abdomen), 1970) (Fig. 2). Laubitz 1970). Males collected in Japan Rostrum: Cephalon without rostrum were 13 mm (Arimoto et al. 1976; Utinomi (Laubitz 1976). 1943) while those from Alaska were 12.4 Eyes: Small (Laubitz 1976) (Fig. 1). mm in length (Laubitz 1970). Antenna 1: Less than half total body Color: White, with brown chromatophores. length (Laubitz 1970). In males, the first an- The illustrated female is darker than the tenna is approximately equal to the cephalon male specimen. combined with pereonite two (Laubitz 1970) General Morphology: The body of amphi- (Fig. 1). Articles 2–3 of peduncle are setose pod crustaceans can be divided into three while the flagellum is shorter than peduncular major regions. The cephalon (head) or articles one and two, and bears 13 articles cephalothorax includes antennules, anten- (Laubitz 1970) (Fig. 1). In the illustrated fe- nae, mandibles, maxillae and maxillipeds male, antenna one is a little longer than ce- (collectively the mouthparts). Posterior to phalon and pereonite one and the flagellum the cephalon is the pereon (thorax) with has 10 articles (Fig. 2). seven pairs of pereopods attached to pere- Antenna 2: Antenna two in the illus- onites followed by the pleon (abdomen) with trated specimens is longer than the peduncle six pairs of pleopods. The first three sets of of antenna one and has flagellum with short pleopods are generally used for swimming, setae (Laubitz 1970) (Figs. 1, 2). while the last three are simpler and surround 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. Caprella drepanochir. 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. Mouthparts: Mandible with molar tal to poison spine and separated by cleft. (McCain 1975) and without palp (McCain There are no anterodorsal projections on pro- 1975). Left ‘lacinia mobilis' with five teeth podus in this species (Laubitz 1970) (Fig. 1). (Fig. 5) and right ‘lacinia mobilis' denticulate The dactyl is heavy, slightly curved, with inner but not five-toothed (McCain 1975) (not figu- margin slightly denticulate and not setose. red). The gnathopod is attached just posterior to Pereon: Pereon with only six segments (not middle of pereonite two (in male) and at- seven as in other amphipods) and no pereo- tached near the middle of pereonite two, but pods on pereonites three or four not at its anterior end (in female) (Laubitz (Caprellidae, McCain 1975; Laubitz 1976). 1970) (Fig. 2). The palm of propodus has a Pereonites cylindrical and longer than deep proximal grasping spine and an accessory (Laubitz 1976). Pereonites in this species spine, and a minute distal poison spine (Fig. are without dorsal spines or tubercules, but 3). Ventral spines between insertions of are covered with fine hairs (Fig. 1). Male second gnathopods are lacking in this species pereonite one is not more than twice the (Fig. 1a). Female gnathopods are much length of the head while female pereonite smaller than those of males. one is shorter than the head (Laubitz 1970) Pereopods 3 through 7: Pereopods 5 (Fig. 2). Gills on pereonites three and four –7 prehensile (for grasping) and increase in only. Round in shape and fleshy (Caprella, size posteriorly (Fig. 1). Propodus on all Mayer 1890; Watling and Carlton 2007) pereopods rather stout, with a concave inner (Figs.1, 2). Gills in male individuals are edge and a proximal tooth with a pair of more circular and females are broadly grasping spines (Fig. 1c). Female pereopods rounded (Watling and Carlton 2007). more slender than those of males (Laubitz Oostegites (marsupium) present on 1970) (Fig. 2). pereonites 3–4 in females only. The Pleon: The pleon or seventh pereonite is re- marsupium consists of two pairs of fo- duced and often unsegmented in caprellids liaceous plates called oostegites (McCain 1975). Female individuals with one (Caprellidae, Laubitz 1976) that grow from pair of lobes, but no single-articled appendag- gill bases (Fig. 2) (Arimoto et al. 1976; Wa- es above these lobes (Figs. 2, 4) (Caprella, tling and Carlton 2007). McCain 1975). Coxae: Pleonites: Gnathopod 1: Male gnathopod one Urosomites: is small and the propodus and dactyl have Epimera: serrate grasping margins (Fig. 1) while the Telson: female gnathopod is small, setose (Fig. 2). Sexual Dimorphism: Males much larger and Gnathopod 2: Male gnathopod two is more elongate than females, with a longer very large, especially the propodus, width first pereonite and an exaggerated second being less than half overall length. The gnathopod. Females when brooding have gnathopod is setose, except the dactyl and conspicuous oostegites (see pereon) and distal part of propodus (Laubitz 1970). The lack mandible palps (Watling and Carlton basis is small, with no lateral spines at the 2007). base (Figs. 1, 1b). The propodus is Possible Misidentifications tuberculate anterodistally and palm is with In contrast to the more familiar Gam- small proximal grasping-spine, large distal maroidea, the bodies of caprellid amphipods poison spine, large triangular projection dis- 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] are elongate and cylindrical, their pereonites anteriorly pointed body spines and short are very long and their three pairs of pereo- spines on the stout flagellum of its second pods are prehensile. Caprellids have 2–3 antennae. This species can display ''intersex" pairs of gills on the middle pereonites and features (Laubitz 1970), making males and lack the abdominal pleopods of gammarid females difficult to distinguish. Tritella amphipods. Members of three subfamilies pilimana has laterally pointed body spines and (family Caprellidae) occur locally including, its second antennal setae are long on a Caprellinae, Paracercopinae and Phtisici- slender flagellum. It is more euryhaline than nae. The caprellid family Cyamidae are par- T. laevis and is found from Alaska to asitic on cetacean mammals. They are very California (Martin 1977). Tritella tenuissima is short bodied, dorso-ventrally flattened (like a deep water species, known off shore in isopods), and have third and fourth pereon- southern California. It lacks swimming setae ites especially adapted for hanging on to on antenna two and (some believe) should be their host. transferred to the genus Triliropus (McCain Phtisicinae have three pairs of gills, 1975). not two (unlike Caprellinae). In addition, The genus Metacaprella was they have no molar surface on the mandible. characterized by a pair of appendages above The Phtisicinae have rudimentary pereo- the usual lobes on the female abdomen pods on pereonites three and four (Laubitz (McCain 1975) where Caprella spp. have only 1970). Of this family, Perotripus brevis has the one pair of lobes (Fig. 4). Caprella been reported from California (McCain 1975; anomala and C. kenneryli were formally Watling and Carlton 2007). It, as well as members of this genus (M. anomala and M. Cercops compactus (Laubitz, 1970), occurs kenneryli). Both have a small pair of sharp in Puget Sound. Caprella compactus has spines on the heads and are reported from also been reported from the outer coast of California and from Puget Sound, Washington Oregon, at Cape Arago (Laubitz 1970; Mar- (Keith 1971; McCain 1975; Martin 1977). tin 1977) and is in the only representative of The genus Caprella is characterized by the subfamily Paracercopinae locally. Cer- the presence of gills on pereonites 3–4, cops compactus does not have an elongate oostegites and mandibles without palps body as other caprellids do, its abdomen (females) (Watling and Cartlon 2007). has five segments, and pereonites five and Caprella greenleyi has been reported living on six are short and stout (Watling and Carlton hydroids and algae and on the sea star Henri- 2007). cia spp. both in Oregon and in California The subfamily Caprellinae is the most (McCain 1969, 1975; Martin 1977).