Deutella venenosa Mayer, 1890

GUERRA-GARCÍA, J. M., 2003, Revision of the genus Deutella (Crustacea: Amphipoda: Caprellidea) with description of a new species, redescription of Deutella venenosa Mayer, 1890 and a key to the species of Deutella, Journal of Natural History 37 (9), pp. 1059-1084 : 1072-1080

Deutella venenosa Mayer, 1890

(figures 11–15)

Deutella venenosa Mayer, 1890: 28 , pl. 1, figures 5–9; pl. 3, figures 7–14; pl. 5, figures 19–21; pl. 6, figures 11–24.

Material examined. Two hundred and four males, 73 premature females, 257 mature females, 73 juveniles, 0–5 m depth, November to December 2000, Coquimbo, Chile. Male ‘a’, female ‘b’ and several other specimens have been deposited in the Museo Nacional de Historia Natural de Santiago de Chile, MNHN AMPH No. 11312 .

Distribution. Only known from the type locality, Coquimbo, Chile.

Ecology. Attached to buoys of seaweed cultures, mainly on hydroids, and bryozoans such as Bugula neritina (Linnaeus, 1758) . Also under rocks in the intertidal zone clinging to the hydroid Obelia dichotoma (Linnaeus, 1758) .

Redescription

Male ‘a’

Colour of live specimen. Light brown with dark spots.

Body length. 5.71 mm.

Lateral view (figure 11A). Head provided with a dorsal, anteriorly directed acute projection. Pereonite 1 with a projection medially. Pereonite 2 with three dorsal projections, one small anteriorly, one acute at the middle and a large rounded one posteriorly; a pair of lateral acute projections anteriorly directed. Pereonites 3–7 dorsally smooth, except pereonites 3 and 4 with humps. Side plates of pereonites 3, 4 and 5 projecting ventrolaterally, with margins distinctly crenulate.

Gills (figure 11A). Oval, length about twice width.

Mouthparts. Upper lip (figure 12D) symmetrically bilobed, smooth. Mandibles (figure 12A, B) with three-articulate palp; distal article of the palp with a setal formula 1-x-1x being = 4; penultimate article carrying three setae; mandibular molar process strong, bordered by robust teeth; left mandible with incisor and lacinia mobilis five-toothed, followed by a row of three serrate spines; right mandible with incisor five-dentate and lacinia mobilis deeply serrate followed by a row of two serrate spines; molar flake present, rectangular and setose distally. Lower lip (figure 12E) with small inner lobes, although well demarcated; outer lobes slender, provided with short setae apically. Maxilla 1 (figure 12F) outer lobe carrying six spine-like setae; distal article of the palp with five distal robust setae and one strong seta medially. Maxilla 2 (figure 12G) outer lobe oval, with four setae distally; inner lobe rectangular, two-thirds of outer lobe in length, carrying five setae. Maxilliped (figure 12C) inner plate small and elongate with one tooth and three single setae; outer plate about three times as long as inner plate, with five setae; penultimate article of the palp with a distal projection; dactylus with setulae distally and with a fine seta subdistally.

Antennae. Antenna 1 (figure 13A) about half of body length; peduncle densely setose; flagellum 11-articulate. Antenna 2 (figure 13B) as long as the first two articles of peduncle of antenna 1; proximal article of peduncle provided with an acute projection; the remaining articles of peduncle profusely setose; flagellum two-articulate.

Gnathopods. Gnathopod 1 (figure 13C) basis as long as ischium to carpus combined; propodus triangular with a proximal grasping spine; grasping margin of propodus palm and dactylus minutely serrate. Gnathopod 2 (figure 13D) inserted on the anterior half of pereonite 2; basis as long as pereonite 2; ischium short and rectangular; merus acute ventrally; carpus short and triangular; propodus about twice as long as basis, setose dorsally and ventrally; palm provided with a rectangular projection proximally provided with a small tooth and a distal knotch; dactylus large, curved medially, carrying short setae ventrally on the distal half.

Pereopods. Pereopods 3 and 4 consisting of one article. Pereopod 3 (figure 14A) with nine single long setae apically and one short plumose seta subdistally. Pereopod 4 (figure 14B) with seven single setae and one plumose seta. Pereopods 5–7 (figure 14C–E) similar, increasing in length, respectively; palm of propodus with a proximal row of three, four and seven short spines on pereopods 5, 6 and 7, respectively; merus to propodus setose; dactylus smooth, about half as long as propodus.

Penes (figure 14F). Penes triangular, laterally placed.

Abdomen (figure 14F). Abdomen with a pair of appendages, a pair of lateral lobes and a single dorsal lobe. Appendages serrate distally. Lateral lobes very setose. Dorsal lobe carrying a pair of short plumose setae.

Female ‘b’

Body length 4.82 mm. Pereonite 1 smooth. The lateral acute projections on pereonite 2, present in male, are lacking in female (figure 11B). Flagellum of antenna 1 with seven articles (figure 11B). Propodus of gnathopod 2 (figure 13E) shorter and wider than in male, without rectangular projection proximally; dorsal surface scarcely setose; dactylus shorter than in male and not curved medially. First pair of oostegites scarcely setose; second pair smooth (figure 11B). Abdomen (figure 14G) without appendages; a pair of lateral setose lobes and a single dorsal lobe carrying two simple setae.

Intraspecific variation

The antennae and body projections are very constant in mature specimens. In connection with the mouthparts, the setal formula of the apical article of mandible palp is 1-4-1 or 1-5-1; the presence of six setae on the outer lobe in maxilla 1 and one tooth on the inner plate of maxilliped is very constant. The structure of the mandibles is also constant in all specimens; left mandible with five-toothed incisor, five-toothed lacinia and three spines; right mandible with five-toothed incisor, serrate lacinia, two spines and molar flake present.

Ontogenetic development

The acute projection on the head is already present in the juvenile stages, although other dorsal and lateral projections appear through development (figure 15). Although the grasping spine on the palm of gnathopod 2 propodus is present in the first stages, the rectangular projection becomes more evident in final phases. With development, the ratio length/width of the gnathopod 2 propodus increases, the number of dorsal and ventral setae of gnathopod 2 also increases and the proximal projection on the propodus palm becomes constricted, being more elongate near the carpus; the dactylus increases in length during development and becomes curved and setose only in the final stages.

Remarks

Deutella venenosa Mayer, 1890 was described by Mayer (1890) based on the specimens collected from Coquimbo, Chile, during the ‘Siboga Expedition’. A century later, the presence of Deutella venenosa in Chilean waters is confirmed. The present description is in good agreement with the sparse description and figures of Mayer (1890), except for the structure of pereopods 3 and 4 which are two-articulate in specimens described by Mayer (1890) versus one-articulate in the recently collected and herein redescribed material. The feature of gnathopod 2 and the body ornamentation of this species allow Deutella venenosa to be differentiated from the remaining species of Deutella .