Pycnogonum tesselatum Stock, 1968

George, Zarish, Siddiqui, Ghazala, George, Nazish & Lucena, Rudá Amorim, 2020, A new species of Achelia (Pycnogonida: Ammotheidae) and first records of intertidal sea spiders found on Zoanthus (Cnidaria: Zoantharia) from Karachi Pakistan, Zootaxa 4821 (2), pp. 371-393 : 390

Pycnogonum tesselatum Stock, 1968

( Figure 12 )

Material examined: ( CEMB, PYC– 029) 1♂, Sandspit, 26.iii.2014, on Zoanthus sansibaricus .

Remarks: This species was first described from Karachi Harbor, Pakistan, by Stock (1968) based on a single female specimen. Later, a male specimen was described from a floating buoy near Karachi Harbor ( Moazzam & Moazzam 2003). In the present study, a single female was collected from Sandspit. Our specimen differs from the description by Stock (1968) and Moazzam & Moazzam (2003) mainly with respect to the number of tubercles on the trunk, and the proportion of the articles in the legs. Four conical dorsomedian trunk tubercles are described ( Stock 1968; Moazzam & Moazzam 2003), with the last one, on the fourth article, being very small. In our specimen, this elevation is not present. This may be an individual variation. The proportion between the tubercles is also not the same as illustrated by Stock (1968), but it is equal to that described by Moazzam & Moazzam (2003). The first and second tubercles are smaller than the third, which is also the widest. All tubercles are smaller than the pigmented ocular tubercle. Stock (1968) observed that the femur is the longest article, but in the present specimen the first and second legs have a longer tibia 1 than the femur while in the third and fourth legs, the femur is longer than tibia 1. Stock (1968, fig. 22f) and Moazzam & Moazzam (2003, fig. 2b) incorrectly show the presence of gonopore on coxa 1. In our specimen, and in Stock’s (1968) description, the gonopore is located on the dorsal side of coxa 2.

Pycnogonum tesselatum and P. moolenbeeki Stock, 1992 are the only two known species for the region. They can be differentiated by the absence of dorsal tubercles on the trunk as in P. moolenbeeki and the presence of a single, mid-dorsal prominence on the proboscis, absent in P. tesselatum .

Distribution: Pakistan ( Moazzam & Moazzam 2003), Arabian Sea ( Stock 1968).

Figures

FIGURE 12. Pycnogonum tesselatum Stock, 1968, male: (A) dorsal view; (B) lateral view; (C) 3rd leg. Scale bar: (A and B) 2 mm; (C) 1 mm.