Meridionale laevis ( Hoek, 1881 )

Staples, David A., 2014, A revision of the callipallenid genus Pseudopallene Wilson, 1878 (Pycnogonida, Callipallenidae), Zootaxa 3765 (4), pp. 339-359 : 348-350

Meridionale laevis ( Hoek, 1881)

Figures 3 A–E.

Pallene laevis Hoek, 1881: 78 .

Parapallene laevis Loman, 1908: 46 .

Pallenella laevis Schimkewitsch, 1909b: 11 . Pseudopallene laevis Staples, 2005: 159 .

Material examined. Holotype: BMNH 1881.38. 1 female, Bass Strait, Challenger stn. 162, off East Moncoeur Island, Bass Strait. 38–40 fms.

Description. Lateral processes separated by less than half own basal diameter, length of lateral processes (leg 3) about twice basal width, lateral suture lines separating trunk from lateral processes not evident. Cephalon rounded dorsally, without pre-ocular, mid-dorsal mound or median suture. Abdomen erect, short, slightly constricted distally, length a little greater than half fourth lateral processes. Eyes well-developed, darkly pigmented, ocular tubercle with laid-back appearance typical of the genus, two apical papillae. Proboscis with a vague constriction at about half its length, three jaws well-developed, no distal setae present. Chela fingers less than half length of palm, pointed, moveable finger evenly curved, marginally shorter than immoveable finger, the distal two-thirds of the fingers are narrowly separated or in contact, proximal margin of immoveable finger receded and revealing a gap when closed, no conspicuous lobe along margin of either finger. Oviger claw slender, tapered, narrowly rounded distally, about half length of segment 10, both margins lined with teeth. Compound spine formula; 17:15:16:13. Legs with prominent lateral ecdysial line running the length of all segments, length of second coxa about 2.5 times length of coxa 1, tibia 2 is longest segment, coxa 2, femur and tibia 2 gently curved, tibiae with scattered spinules; tarsus with a cluster of needle-like spines on inner margin, the propodus is moderately curved, heel raised with five spines on two legs and 4 spines on the remaining legs, heel spines followed by two spines of about half size at base of sole, sole lined with field of much smaller spines that extend on to the lower lateral surfaces, about six small spines on dorsal surface and a small group of distal spines; terminal claw long, slender, reaching midway between the heel spines when folded.

Remarks. The general appearance of the specimen suggests that it may have been dehydrated at some stage and whilst every effort has been made to capture life-like images of the specimen this has not been possible due to its contorted condition and a desire not to dissect the specimen. The right chelifore scape is missing forward of the proximal constriction and the left scape is crimped and bent in the same location, very much giving the distinct impression that the scape is two-segmented. The neck region of the cephalon is bent and distorted making it impossible to capture images that depict its true shape. The longer leg segments are mostly collapsed. Membrane covering the genital pores is partially retracted and the trunk is somewhat distorted due to the withered intersegmental membrane separating the segments. Segments 5–10 of the left oviger and part of the right third leg are missing. Two detached and incomplete leg segments, a propodus (possibly off leg 3) and right oviger have been placed in micro-vials accompanying the specimen.

The specimen is now preserved in 75% ethanol. The dark, glazed appearance of the specimen may be a consequence of early fixation methods and unknown preservation medium.

Meridionale laevis is readily distinguished from M. ambigua and M. harrisi by the shape of the proboscis, the absence of a median cuticular division of the cephalon, the propodus with a well-developed heel, an inclined abdomen and the shape of the chela fingers.

Arango and Brenneis (2013: 426) described M. laevis as being big and robust; however, with a body length of 2.66mm ( Hoek, 1881) the holotype is small and considerably shorter than either M. harrisi or M. ambigua .

Meridionale inflata ( Staples, 2005) is similar to M. laevis . Both species share inflated trunk segments and a short, semi-erect abdomen. Differences are found in the much shorter trunk length of M. inflata , the presence of a conical, pre-ocular mound dissected by a cuticular segmental line, the shape of the proboscis and a wreath of setae proximal to the jaws. The propodal heel is far more prominent in M. laevis than in M. inflata . The similarities between these species are nevertheless unsettling particularly as both species are recorded from Investigator Strait, South Australia and the possibility of synonymy should be investigated in the light of any additional mature specimens.

Distribution. Eastern Bass Strait and Investigator Strait, South Australia.

Figures

FIGURE 3. Meridionale laevis; holotype, (BMNH 1881.38), 1 female, A, trunk dorsal view; B, left chela; C, leg 3; D, propodus, leg 3; E, proboscis and left chela, ventral view. Meridionale ambigua; male holotype (ZMH K 17680); F, anterior view; G, trunk, dorsal view; H, right chela (scale bar = 1 mm.).