Paradella Harrison & Holdich, 1982

Wetzer, Regina & Bruce, Niel L., 2007, A new species of Paradella Harrison & Holdich, 1982 (Crustacea: Isopoda: Sphaeromatidae) from Baja California, Mexico, with a key to East Pacific species, Zootaxa 1512, pp. 39-49 : 39-41

Paradella Harrison & Holdich, 1982

Paradella Harrison & Holdich, 1982: 99 .– Harrison, 1984: 386.– Harrison & Ellis, 1991: 943.— Kensley & Schotte, 1989: 223.— Storey, 2002: 139.— Bruce & Wetzer, 2004: 2 .

Type species: Paradella octaphymata Harrison & Holdich, 1982 , by original designation.

Diagnosis. Body vaulted, dorsal surfaces smooth or with nodular ornamentation, without setae or with sparse setae; with ability to conglobate; strongly sexually dimorphic. Pleon consisting of 4 visible segments (as determined by lateral sutures); pleonite 1 entire; sutures (except first) running to posterior margin, merging, short; dorsal surface without process, with 2 or more pairs of tubercles; posterior margin even, with 'keys'. Pleotelson anteriorly as wide as pleon, without dorsal process; posterior margin with subapical Y-shaped foramen connected to posterior by narrow slit, with ventral thickened rim; lateral margins forming ridge. Epistome anteriorly narrow, without median constriction. Penial processes basally fused, long (extending to pleopod 1 rami). Pleopod 1 rami not operculate; exopod lamellar. Pleopod 2 endopod about as long as exopod; appendix masculina inserted basally, on short proximal lobe of endopod. Uropod rami broad, lamellar.

Description. Head with rostral point present, simple, separating antennular bases; anterior margin simple, without paired incisions in front of eyes, lateral margins not laterally extended to body outline (antennules more or less ventral). Pereonite 1 lateral margins not anteriorly produced, not laterally enclosing head; pereonites 2–7 or 5–7 with posterior margin raised, forming narrow transverse ridge (usually on pereonites 5–7); anteriorly without keys. Sternite 1 without cuticular mesial extensions. Pereonite 6 simple, dorsally without bosses, processes or marginal extensions. Pereonite 7 as wide as pereonite 6, forming part of body outline, dorsally without bosses, processes or marginal extensions or with bifid posteriorly directed process. Coxae distally wide, those of pereonites 2–7 overlapping the one behind, coxae without ventral 'lock and key' processes, without grooved articulation; those of pereonite 6 not large, not overlapping those of pereonite 7. Pleon posterior margin even, as wide as pleotelson; pleonal sternite narrow; pleotelson vaulted, weakly bidomed.

Antennule peduncle with basal articles mesially not in contact, peduncle articles 1 and 2 robust, article 3 slender; article 1 not produced; article 2 approximately 0.5 as long as article 1; with articles 2 and 3 colinear, article 3 longer than article 2; flagellum shorter than peduncle, longer than peduncular article 3. Antenna peduncle articles all colinear, of similar thickness, less robust than peduncle articles of antennule.

Epistome anteriorly not prominently extended, elongate, posteriorly enclosing labrum.

Mandible incisor wide, multicuspid; lacinia mobilis present; spine row normal, molar process gnathal surface with transverse ridges, rounded. Maxillule lateral lobe with RS, some or all serrate, mesial lobe with 4 major heavily RS. Maxilla with nodular setae on middle and lateral lobes nodular. Maxilliped palp articles 2–4 mesial margins lobate, article 2 not expanded; endite distal margin truncate, with clubbed RS, anteromesial (upper) marginal ridge without long curved serrate RS.

Pereopod 1 ambulatory; dactylus secondary unguis simple; setae on merus and propodus short. Pereopod 1 (or 1–3), inferior margins of merus, carpus and propodus without conspicuous RS. Pereopod 2 similar in proportion to pereopod 3, dactylus with secondary unguis simple, short and stout. Pereopods 3–7 dactylus with secondary unguis simple. Pereopods with inferior margins of ischium to carpus bearing dense setulose fringe; ischium superior margin with sinuate acute RS, pereopods 1–3 (or 1–4) ischium superior margin without long stiff slender setae.

Penes tapering smoothly from midlength, apex acute.

Pleopod 1 exopod with longitudinal axis weakly oblique, distally subtruncate or truncate; endopod of similar proportions to exopod, mesial margin lamellar, distally angular, endopod proximomesial heel present. Pleopods 1 and 2 exopod distal margins not deeply serrate. Appendix masculina with straight margins, longer than and extending beyond endopod, distally acute. Pleopod 3 exopod transverse suture present, endopod transverse ridges absent, endopod of similar proportions to exopod. Pleopod 4 rami without PMS; exopod with thickened transverse ridges present, transverse suture absent, lateral margin not thickened, with short simple marginal setae; endopod with thickened transverse ridges present; mesial margin with deep distal notch, proximomesial lobe present. Pleopod 5 exopod with thickened transverse ridges present, transverse suture present, incomplete, lateral margin with short simple setae, not thickened, distally usually with 3 discrete scale patches forming protruding lobes; endopod with thickened transverse ridges present, with proximomesial lobe.

Uropod rami not strongly flattened, not forming part of continuous body outline; exopod (of adult male) similar in length to endopod, lamellar, lateral margin simple, finely serrate or smooth, distally broadly rounded or narrowly rounded or distally acute; endopod lamellar, distally broadly rounded.

Female. Mouthparts of female not metamorphosed. Marsupium formed from 4 pairs of oostegites, anterior pocket absent, posterior pocket absent, oostegites not overlapping at mid-line. Ornamentation of pereonites, pleon and pleotelson less developed than in male; uropod rami of similar proportions, lateral margin of exopod not upturned.

Species included: P. a c u t i t e l s o n ( Menzies & Glynn, 1968), Puerto Rico; P. bakeri ( Menzies, 1962b) , Chile; P. dianae ( Menzies, 1962a) , Baja California, Mexico (now widely translocated by international shipping, e.g. Bey et al., 2001, Hass & Knott, 1998); P. garsonorum sp. nov., Baja California, Mexico; P. harrisoni Müller, 1995 ; Kenya; P. heptaphymata Shoukr, Mona & Rizk, 1987 , Suez Canal, Egypt; P. octaphymata Harrison & Holdich, 1982 , type species, Great Barrier Reef, Queensland and Vietnam, South China Sea ( Kussakin & Malyutina, 1993); P. plicatura ( Glynn, 1970) , Venezuela; P. quadripunctata ( Menzies & Glynn, 1968) , Puerto Rico; P. setosa (Glynn, 1968) , Pacific Panama; P. t o m l e - klek Storey, 2002, Phuket, Thailand; P. tuberculata Müller, 1991 , Society Islands (Tahiti); P. t u m i d i c a u d a ( Glynn, 1970), Venezuela; P. tiffany Bruce & Wetzer, 2004 , Baja California, Mexico.

Known undescribed species: Paradella sp. Baja California, Mexico, from mangrove prop-roots.

Remarks. Current generic diagnoses in the Sphaeromatidae are more restrictive than previously. A critical revision of those species placed in Dynamenella Hansen, 1905 (see Harrison & Holdich 1982), would likely see transfer of some of those species and some of the numerous incertae sedis species into Paradella , notably those species with merging Yshaped pleonal sutures and a long appendix masculina.

Paradella can best be identified by males having a distinct dorsally-directed, Y-shaped and posteriorly closed pleotelson foramen, long, tapering and basally fused penial processes, a long and basally narrow appendix masculina that usually extends beyond the distal margin of the endopod, both sexes with two fused Y-shaped pleonal sutures, entirely lamellar pleopod 1 rami and pereopod dactyli with a simple secondary unguis.

Distribution. Widespread in shallow-water habitats in temperate and tropical regions of the Pacific Ocean, Indian Ocean and tropical western Atlantic; probably world wide, but not recorded from the eastern Atlantic or Mediterranean, nor from temperate northwestern Pacific ( Japan, Korea).