Caprella dilatata Kroyer 1843
Creators: name: Masunari, Setuko
name: Takeuchi, Ichiro
Publisher: name: Zenodo
Year: 2006
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Caprellidae
Caprella
Caprella dilatata

description: Caprella dilatata Krøyer, 1843
(Figs 1–4)
Caprella dilatata: Krøyer, 1843, 585–590, pl. 8 figs. 1–9; McCain, 1968, p. 38; Krapp­Schickel, 1993, p. 779, fig. 532; Guerra­García & Takeuchi, 2002, p. 683.
Material examined
20 males, 20 females and 20 juveniles obtained from a mussel longline, in Itapocoroi Bay, Penha County, Santa Catarina State, southern Brazil (26°58'S ­ 48°35'W); 22 June 2002. Four males and two females obtained from red algae, intertidal zone of rocky shore, Mar del Cobo, Argentina (37°46'S ­ 57°27'W); 4 April 1998; coll. Dr. Eduardo Spivak. Five males obtained from green algae of fouling community, Mar del Plata Harbour, Argentina (38°03'S ­ 57°31'W); 16 June 2004; coll. Dr. Eduardo Spivak.
Description
Male
Body length. 10.0 mm (largest male).
Dorsal view (Fig. 1 A). Body stout and covered with numerous delicate ornamental sets that are composed of a small nodule and a very fine and short seta, which are visible only under high magnification (Fig. 1 A’). Pereonite 1 short; pereonites 2, 3 and 4 subequal in length; pereonites 5–7 gradually shortening towards posterior end. Pereonites 3 and 4 provided with a pair of well­developed auricular pleuras. Pereonite 5 with a pair of dorsolateral projections.
Lateral view (Fig. 1 B). Head with a well­developed rostrum. Pereonites 5–7 dorsally elevated.
Gills. Large and rounded.
Antennae. Antenna 1 (Fig. 2 A) about the same length as head plus pereonites 1–2, with ten setose articles in the flagellum; the first and second peduncular articles inflated, the first one provided with scarce setae and covered with dense ornamental sets while the second one, only by scarce setae. Antenna 2 (Fig. 2 B) about 1/3 shorter than antenna 1; peduncular article 2 provided with a short seta and four long setae, gradually shortening towards ventro­proximal angle; peduncular articles 3 and 4 with dorsal surface covered with ornamental sets and ventral margin provided with 13 sets of setae each one; these sets are composed of a pair of long serrated setae and a pair of medium sized setae; article 3 carrying a long seta on halfway and another distally in the dorsal margin; article 4 with scarce short setae on dorsal surface; flagellum two­articulate, the first one with short setae and scarce ornamental sets on dorsal surface and eight sets of setae, similar to peduncular article 4, in the ventral margin; the distal article very short and setose subterminally and terminally.
Mouthparts. Upper lip symmetrically bilobed, completely pubescent but more densely in the upper half where the setae are semi­upright; a crown of short upright setae subapically (Fig. 3 B). Lower lip with inner and outer lobes round and pubescent apically (Fig. 3 C). Mandibular process strong and provided with two almost straight cutting edges in the left one; both mandibles with five­toothed incisor and lacinia mobilis. Right mandible provided with a row of two pectinated setae (Fig. 3 E), the left one with three (Fig. 3 G). Maxilla 1 outer lobe provided with seven serrated spines in the distal edge; article 2 of palp with five apical robust setae, eight slender setae in the inner margin, and 19 slender lateral setae on its distal two­third (Fig. 3 F). Maxilla 2 with inner lobe ovate and outer one rectangular: their distal margins form a contiguous line that bears setae of varied lengths (Fig. 3 D). Maxilliped inner plate provided with 17 long plumose setae and three spines, outer plate carrying 25 long plumose setae, 13 of them in outer surface, and seven teeth; palp four­articulate, articles 2 with 33 long plumose setae on inner and apical area, article 3 with 36 long plumose setae almost all on inner surface (Fig. 3 A); article 4 provided with rows of setulae on its grasping area (Fig. 3 A’).
Gnathopods. Gnathopod 1 with ornamental sets on outer surface of propodus, merus, ischium and basis; basis to propodus provided with numerous ventral setae; propodus with a pair of proximal grasping spines, palm almost straight, inner margin of propodus and dactylus serrate (Fig. 2 C); inner surface of propodus covered with short setae and provided with a row of 17 long setae parallel to dorsal margin (Fig. 2 C’). Gnathopod 2 inserted in the middle of ventro­lateral line of pereonite 2, and covered with ornamental sets, except carpus and dactylus; basis 1/3 length of pereonite 2, with a lateral expansion; ischium round with a seta in the middle of posterior margin; merus 2.0 times ischium, with a projection and five setae in its antero­ventral angle; carpus short; propodus a little longer than pereonite 2, length ca. 1.6 times width, proximal margin of palm round and without any poison tooth and remaining area of palm densely setose and provided with an acute projection halfway and a rectangular process subdistally; dactylus with inner margin serrate and almost straight, provided with small setae in outer and inner margin area (Fig. 2 E).
Pereopods (Figs 4 A, 4B, 4C). Pereopods 5, 6 and 7 increasing in length, basis, ischium and merus only partially covered with ornamental sets, but on whole outer surface of carpus and propodus; basis and ischium with six and four setae at ventro­distal angle, respectively; merus and carpus with a varied number of setae in both margins; palm of propodus slightly concave provided with two proximal grasping spines; dactylus curved.
Abdomen. With a pair of two­articulate appendages, a pair of median lobes, and a single dorsal lobe; articles of each appendage rounded, the apical one about half length of proximal one that is provided with nine setae on ventral surface; median lobes with 4 setae in the postero­proximal angle and 2 setae in the postero­distal one; single dorsal lobe with a pair of plumose setae on dorsal surface. Penes median, oval, length ca. two times width (Fig. 4 D).
Female
Body length: 6.8 mm (Fig. 1 C). Smallest ovigerous female 3.8 mm. Body and most appendages covered with ornamental sets. Pereonites 3 and 4 provided with a pair of pleura: the first overlapping the second one. Gills ovate. First and second peduncular articles of antenna 1 not inflated. Gnathopod 2 (Fig. 2 D) inserted near antero­lateral angle of pereonite 2; propodus with proximal poison tooth, palm almost straight, length ca. 1.8 times width. Abdomen with a pair of lateral lobes and a dorsal lobe with a pair of plumose setae (Fig. 4 E).
Immature Male
Body length: 5.7 mm (Fig. 1 D). Body and most appendages covered with ornamental sets. Pereonites 3 and 4 provided with a pair of small pleura. Gills round. Propodus of gnathopod 2 provided with proximal poison tooth (Fig. 1 D’).
Variation
Propodus palm of male gnathopod 2 in the analyzed specimen is naked in the proximal area, but setae cover the entire palm in many individuals.
Type locality
Rio de Janeiro, Brazil (Krøyer 1843).
Distribution
Mediterranean Sea. Spain, France, Italy (Tyrrhenian Sea, Genova, Napoli), Egypt (Port Said, Alexandria), Algeria and Ceuta (McCain & Steinberg 1970; Krapp­Schickel 1993; Guerra­Garcίa & Takeuchi 2002). Atlantic Ocean. North Sea, Spitzbergen, France and Spain (McCain & Steinberg 1970), Lázaro Beach, Ubatuba, São Paulo State (Jacobucci et al. 2002), and Itapocoroi Bay, municipality of Penha, Santa Catarina State, Brazil and Mar del Cobo and Mar del Plata Harbour, Argentina (present paper).
Ecology
At 10m depth, over surface of ropes connecting the boat and the anchor in the Harbour of Rio de Janeiro (Krøyer 1843); in shallow water, amongst algae (Fischetti 1973 apud Krapp­Schickel 1993); in the infralittoral of sheltered hard bottom area, at 10–20m depth, dominated by algae, anthozoans and echinoderms (Guerra­Garcίa 2001); in the infralittoral fringe of moderately exposed hard bottom dominated by the brown seaweed Sargassum cymosum, at 4m depth (Jacobucci et al. 2002). In Itapocoroi Bay, Santa Catarina State, Brazil, C. dilatata specimens occur in high density over surface of mussel shells, bissus attached to longlines of mussel farming, and in associated bryozoons and sponges or directly on the surface of float or ropes that hold longlines at 1–6m depth (present paper). In summer months they become so numerous that it might cause irritations to farmers’ skin.
description: Published as part of Masunari, Setuko & Takeuchi, Ichiro, 2006, Redescription of Caprella dilatata Krøyer, 1843 (Caprellidae: Amphipoda: Crustacea) from Brazil, with note on its biogeographical distribution in South America, pp. 49-60 in Zootaxa 1298 on pages 50-57, DOI: 10.5281/zenodo.173575