Eisothistos adlateralis, Knight-Jones & Knight-Jones, 2002

Knight-Jones, E. W. & Knight-Jones, Phyllis, 2002, Four new species of Eisothistos (Anthuridea: Isopoda) from tubes of Spirorbidae (Serpuloidea: Polychaeta), Journal of Natural History 36 (12), pp. 1397-1419 : 1406-1408

Eisothistos adlateralis sp. nov.

(gure 4)

Material. Holotype and six paratypes from Protolaeospira or Paralaeospira tubes at Kaiti Beach, N. Island, New Zealand, 38ss42¾S, 178ss03.5¾E, sampled 14 March 1993. Two from 1–2 m depth, 43ss49¾S, 172ss54.3¾E, 21 February 1993, near Wainui in Akaroa Harbour. One at L.W. 41ss44.7¾S, 171ss28.4¾E, 24 February 1993, in shelter of Cape Foulwind. Two at L.W. in Island Bay near Wellington, 3 March 1993. Three in Pukerua Bay 41ss02¾S, 174ss02¾S, 8 March 1993. Four at 37ss57.5¾S, 177ss27¾E on Opape Beach near Opotiki in Bay of Plenty, 15 and 16 March 1993. Six at 36ss17¾S, 174ss48¾E in Matheson Bay near Leigh, 20 March 1993.

Description. HOLOTYPE. Post-partum female 2.1 mm long, brooding several eggs like that in gure 4D, with about ve ocelli per eye (gure 4A) and characters typical of post-partum stage, i.e. antennae 1 and 2 with no aesthetascs and few setae, pereopods without subdistal wheel-joints, tail-fan wide and body slender. Telson very like those described above, except that mid-line keel spines are not detectable, there are two small setae in the centre of the hind margin (gure 4B) and the two small dorsal setae anterior to the hind margin are in ‘adlateral’ positions, i.e. about the same distance apart as the second largest pair of marginal setae. After a year mounted in glycerol these telsons became so transparent that marginal teeth could no longer be seen (gures 4B, C were drawn before they disappeared). This transparency revealed, inside the basal article of each uropod, a pear-shaped body made up of numerous criss-cross and radiating bres, perhaps of uropod muscles.

PARATYPES from Kaiti Beach. Ovigerous female 1.7 mm long (gure 4C), with eggs (full of fat globules) con ned to pereonites 3–5, ca two eggs per segment, dorsal view of head shows basis of each antennule bearing small leaf-like anterior projection on paramedial side, aesthetascs lacking, pereopods without subdistal wheel-joints, hind telson as in holotype but with only one mid-line seta; another mated female 1.2 mm long, most pereonites nearly 0.2 mm wide, aesthetascs and wheel-joints lacking; two post-partum females, 1.2 and 1.5 long, latter giving good ventral view of fused rami of pleopod 1 (gure 4G); manca 1.2 mm long; ripe female 2.7 long, most pereonites 0.3 or 0.4 mm wide, with subdistal wheel-joints on pereopods (gure 4E) and aesthetascs on antenna I (as in gure 4F).

Other material. Two manca from Akaroa Harbour 0.7 and 0.9 mm long, subdistal aesthetascs on antennule; Cape Foulwind , post-partum female 1.5 mm long, telson with dorsal setae clearly adlateral; Island Bay , two manca; Pukerua , manca 0.7 mm, hind telson without mid-line seta; manca 0.6 mm, almost embryonic but with aesthetascs and wheel-joints; manca 1.3 mm, without ischial studs on pereopods 2 and 3; Opape Beach , post-partum female in two pieces, tail-fan 0.5 mm wide, telson like gure 4B but with only one seta in central notch, pereopod 3 of anterior piece with pointed studs, six along ventral edge of ischium, three or four on merus, perhaps one on carpus (seen more clearly in large paratype gure 4E), several eggs and embryos including one hatching (gure 4D); Matheson Bay , three manca <0.9 mm long, with aesthetasc on each of two subdistal articles of antennules (gure 4F), three females without aesthetascs or wheel-joints, one fat, 1.4 mm long, one ovigerous 2.1 mm long, pereon with ca 12 unspawned eggs, one post-partum 1.7 mm long, with long elbow seta on each pereopod ischium .

Etymology. Latin ad 5towards (or near), lateralis 5lateral, referring to pair of small dorsal setae anterior to telson’s hind margin. These are also near the telson’s side margins, as in other Paci c species described below.

Remarks. The name adlateralis refers to a character which is not generally distinctive. Many Eisothistos species have small dorsal setae in adlateral positions on the telson. Of these, Eisothistos antarcticus has a very spiny telson keel and big studs regularly arranged along ischium of pereopod 3; E. anomalus and E. neoanomalus have three pairs of plumose setae on hind telson; E. bataviae , E. besar and E. maledivensis each have many marginal teeth on hind telson, separating plumose setae of adcentral pair; E. besar and E. teri both have a remarkable re exed spine on the main fang of each uropodal exopod, whilst E. tayronae has seven plumose setae on each pleopod 1 (cf. gure 4G). These peculiarities are all lacking in this New Zealand species, which is therefore regarded as new. Its name helps to separate it from the new species described above. It seemed to be more abundant in North Island than South Island. The pattern of studs on ischium and merus of pereopods 2 and 3, seen on gure 4E, cannot usually be detected in small specimens of this comparatively small species.