Phylum: Arthropoda, Crustacea Nippoleucon hinumensis Class: Multicrustacea, Malacostraca, Eumalacostraca Order: Peracarida, Cumacea Family: Leuconidae Taxonomy: Nippoleucon hinumensis was lack of a free telsons and uropod endopods described as a member of the genus Hemi- that are biarticulate (Watling 2007). (For gen- leucon at the same time many other cuma- eral morphology of N. hinumensis, see also cean species were described, in the early Plate 229A, Watling 2007.) 1900s. Walting revised the Leuconidae in Cephalon: A carapace covers the cephalon 1991 and described the first new leuconid and first three thoracic somites and is expand- genera since 1907. In his manuscript, Wat- ed on either side to form a branchial chamber ling transferred two Hemileucon species (Watling 2007). (including H. hinumensis) to the newly erect- Eyes: None in either sex. ed genus Nippoleucon based on morpholog- Antennae: Antennae one are non- ical characters (e.g. male antenna two, pe- unique and short in females while antennae duncular articles, Watling 1991) (Lee and two are rudimentary (Jones 1963). In males, Lee 2003). the second antenna has a peduncle with five articles and a long flagellum (12 segments) Description that extends into the second thoracic segment Size: The illustrated males and females are (Calman 1907) (Fig. 3). both 5 mm in length (from the Columbia Riv- Mouthparts: Two pairs maxillae and er Estuary). three pairs maxillipeds. Mandibles are with Color: Descriptions of color in the Cumacea massive truncate bases, without palp and with are difficult as many species were described strong molar process, incisor process and la- based on preserved material, where the col- cinia mobilis (Fage 1951) (not figured). or fades. Carapace: Female carapace with a General Morphology: Cumaceans are eas- wide antennal notch that is pronounced into a ily recognizable by a large and inflated cara- tooth at an anterolateral angle (Fig. 1). Ante- pace and a (relatively) slender, flexible thor- rior and posterior edges are slightly serrate ax and abdomen (Kozloff 1993; Gerken and and the anterior half of the carina (ridge) is Martin 2014). Their bodies can be divided finely and irregularly serrate. (Jones 1963 into these three major regions: the cepha- found two oblique ridges on the carapace lon (head) that is covered by a carapace sides, which were not observed here.) The and includes the first five pairs of appendag- carapace in males has an anterolateral edge es (antennae, mandibles, maxillae, collec- that is not pronounced into a tooth and no se- tively the mouthparts). Posterior to the rrations on anterolateral or lower edges cephalon is the pereon (thorax), usually (Jones 1963) and no antennal notch (Calman consisting of five thoracic somites, followed 1907) (Fig. 2). by the pleon (abdomen) with consistently Rostrum: Two pseudorostral lobes six pleonites. The fifth pleonite is usually the (together called a pseudorostrum), or exten- longest and the pleonites are lacking pleo- sions of the carapace, extend anteriorly but pods in female individuals. The cumacean do not fuse in front of the head in cumaceans family Leuconidae are characterized by the 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. Nippoleucon hinumensis. 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, Charles- ton, OR. (Watling 2007). The pseudorostrum in fe- Possible Misidentifications male N. hinumensis is abruptly upturned Cumaceans are very small (range 1 (Fig. 1) and is more horizontal and truncate mm–1 cm) shrimp-like crustaceans. Their in males (Fig. 2). heads and thorax are fused to form a Pereon: Consists of five thoracic somites, carapace, the abdomen is tubular and the each with paired appendages (pereopods). uropods are slender and biramous. There Pereopods: Female pereopod ex- are 1500 species worldwide, approximately opodites on somites 1–3 (Leuconidae, 50 of which occur on the Pacific coast of the Stebbing 1913) (Fig. 1). Pereopods four United States (Watling 2007; Gerken and and five without exopodites (Fig. 5). Male Martin 2014). Cumaceans belong to the pereopod exopodites on pereopods 1–4, Malacostraca, and are characterized by a none on five (Calman 1907) (Figs. 2, 4). carapace that covers the first three or four Pleon: Consists of six segments and the thoracic somites and has an anterior fifth is longest. The telson is fused with the extension (pseudolobes), a telson that is sixth somite (Figs. 1, 2, 6). present or reduced and fused with the last Pleopods: All female cumaceans pleonite, eyes that are united dorsally, a lack pleopods and males in the genus Nip- second antenna that is without an exopod poleucon also lack pleopods. and pleopods that are absent in females and Telson: Telson not independent and fused can be absent or reduced in males (Watling with last abdominal segment (Leuconidae) 2007). (Figs. 6). The superorder Peracarida includes Uropods: Uropod peduncles longer than cumaceans, mysids, isopods, tanaids and abdominal segment six (Calman 1907) and amphipods. Cumaceans can be separated more than 2/3 as long as the rami (Stebbing from mysids by their single compound eye 1913). Uropods are slender, cylindrical, and (particularly in the males), as mysids have biramous. The endopod inner branch is large stalked eyes. Mysids have a carapace biarticulate. The first article of the endopod which covers the entire thorax, while cuma- is longer than the second, and is with nine ceans have several posterior segments ex- spines on the inner edge. The endopod is posed. Euphausiids belong to the superor- shorter than the exopod (Jones 1963) (Fig. der Eucarida (along with decapods) and are 6). The exopod (outer branch) is also biarti- pelagic and marine, but might occasionally culate (as in all Cumacea, Watling 1979), be found in estuaries. They have biramous has two unequal terminal setae (Calman thoracic appendages (cumacean pereopods 1907; Jones 1963) (Fig. 6), and a series of are uniramous, with some thoracic ex- setae on both inner and outer edges opodites). Additionally, euphausiids have (Calman 1907). The uropods are similar in strong pleopods for swimming and cuma- both sexes. cean pleopods, when present, are small. Sexual Dimorphism: Not as strong in this The four local cumacean families can species as in those in which males have be divided into those with a freely articulated eyes and pleopods. Males are more slender telson and those without, the former com- and longer than females. Males also have prise the Lampropidae (see Lamprops quad- long second antennae. A brood pouch is riplicata, this guide) and Diastylidae, while present in mature females only and is large, the latter comprise the Leuconidae and Nan- simple and transparent (not figured). nastacidae (see Cumella vulgaris, this guide) (Watling 2007). Cumacean families that lack 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] an articulated telson are consistently mono- Two genera, Eudorella and Nippoleu- phyletic on molecular phylogenies and are con, each with a single species, are currently likely derived within the Cumacea (Haye et reported from central California to Oregon al. 2004). However, morphological charac- (Watling 2007). Eudorella pacifica has a ters used to differentiate cumacean families truncate edge to the carapace, like N. (e.g. number of pleopods in males) may be hinumensis. Eudorella pacifica females, homoplasious (see Haye et al. 2004). however, have a uropod exopod that is The Leuconidae (like the Nannastac- shorter than the endopod. idae) lack the independent telson. Howev- The family Nannastacidae lack an in- er, they always have a biarticulate uropod dependent telson, the males have no pleo- endopod, not a uniramous one as in Nan- pods and the endopod of the uropod is uniar- nastacidae. Members of the Leuconidae ticulate. The Lampropidae and Diastylidae often have up to two pairs of male pleopods have a freely articulated telson and the for- (there are none in Nannastacidae) and mer family has three or more terminal setae have exopodites on all five pairs of pereo- on the telson while the latter has 0–2. The pods (rarely on three). Leuconid females Lampropidae includes six local species in the have exopodites on four (rarely on three) genera Hemilamprops and Mesolamprops pairs of pereopods (Watling 1979). Num- (each with one local species) and the Lam- bers of pereopodal exopodites in both sex- props (four local species, see L. quadriplica- es are too alike in the families Leuconidae ta, this guide). In the Diastylidae there are and Nannastacidae and may not serve as five local species in three genera including dependable characters for identification. Anchicolurus and Diastylopsis (one local One of the oldest cumacean families species each) and Diastylis (three local spe- (Watling 1991), the Leuconidae were re- cies) (Watling 2007). cently been removed from the Hemileuco- Ecological Information nidae (Given 1969). (This separation is not Range: Type locality is New Zealand, but this followed by Jones 1963, however, see be- species was introduced to west coast estuar- low.) Both families lack an independent tel- ies (e.g. San Francisco and Coos bays) from son and both have a biarticulate endopod Japan in ballast water (Castillo et al. 2000; on the uropod. In Leuconidae, however, Watling 2007). there are usually two pairs of male pleo- Local Distribution: Oregon distribution in- pods, rarely 1 or 0 pairs, while there are no cludes the Columbia River Estuary and sites male pleopods in the Hemileuconidae.