(Figs 8, 15–17, 20)
Saemundssonia (Saemundssonia) sp.; Palma 1999: 381.
Saemundssonia (Saemundssonia) sp.; Murray, Palma & Pilgrim 2006: 1965. Saemundssonia sp. M; Palma 2010: 409.
Type host. Gygis alba candida (Gmelin, 1789), the white tern.
Type locality. Peka Peka Beach, Kapiti Coast, North Island, New Zealand.
Holotype: 3 in MONZ.
Diagnosis. Male: habitus as in Fig. 16. Clypeal signature as in Fig. 8. Genitalia as in Fig. 15. Six long submarginal metanotal setae on each side (occasionally 7 on one side).
Female: habitus as in Fig. 17. Clypeal signature as in Fig. 8. Ventral pigmented plates of the last abdominal segments as in Fig. 20. Six long submarginal metanotal setae on each side (occasionally 7 or 8 on one side). Measurements of both sexes as in Table 1.
Etymology. The species epithet gygisa is a noun in apposition referring to the generic name of the host.
Material examined. Types. Ex Gygis alba candida (Gmelin, 1789): Holotype 3, Peka Peka Beach, Kapiti Coast, North Island, N.Z., 23 Apr. 1988, R. Powlesland (MONZ, AI.024057). Paratypes: 13, 3 Ƥ, same data as for holotype (MONZ, AI.018931); 33, 7 Ƥ, Atiu, southern Cook Islands, 24 Aug. 1977, A. Black (MONZ, AI.018929); 13, 2 Ƥ, Raoul I., Kermadec Islands, N.Z., 10 Jul. 1983, A.W. Blundell (MONZ, AI.018930); 1 Ƥ, Muriwai Beach, Auckland, N.Z., 6 May 1990, N. Rothwell (MONZ, AI.018932).
Remarks. As expected from its host association, Saemundssonia (Saemundssonia) gygisa is morphologically close to a group of about a dozen species (see Price et al. 2003 a: 290–293) parasitic on members of the bird family Sternidae (Checklist Committee 2010: 230), sometimes referred to as Sterninae, a subfamily of the Laridae (Dickinson 2003: 149). The closest morphological species to S. (S.) gygisa are: S. (S.) lobaticeps (Giebel, 1874), S. (S.) hopkinsi Clay, 1949, and S. (S.) melanocephalus. (Burmeister, 1838).
The male genitalia of Saemundssonia (Saemundssonia) gygisa are extremely different from those of S. (S.) melanocephalus, but similar to those of S. (S.) lobaticeps and S. (S.) hopkinsi. However, males of S. (S.) gygisa can be distinguished from S. (S.) lobaticeps and S. (S.) hopkinsi by the configuration of the genitalia (Fig. 15) with wider, shorter parameres, and differences in the mesosome and endomeres (compare Fig. 15 with figs 20–21, 30 – 31 in Clay 1949). In addition, the shape and proportions of the head (Fig. 16) and the clypeal signature (Fig. 8) may assist in the identification of males. As with most species of Saemundssonia (see Discussion below) females are more difficult to separate, but S. (S.) gygisa can be identified by the following combination of characters: shape and proportions of the head (Fig. 17) and clypeal signature (Fig. 8); configuration of the ventral pigmented plates of the last abdominal segments (Fig. 20); and the shape of thoracic sternal plates. However, females of S. (S.)
gygisa are very similar to those of S. (S.) lobaticeps, S. (S.) hopkinsi, and S. (S.) melanocephalus in most features, and can only be separated by subtle details in the shape of the ventral plates of the last abdominal segments.
The key to species of Saemundssonia from the Sternidae in Clay (1949: 4) includes six species only, and therefore it is not relevant to attempt placing S. (S.) gygisa in it. However, in the key to species by Ward (1955: 84), males of S. (S.) gygisa key out to couplet 2 by having a “Basal plate with distal sclerotized crossbar”. That couplet includes S. (S.) lobaticeps (Giebel, 1874) and S. (S.) hopkinsi Clay, 1949, which can be distinguished from S. (S.) gygisa by features of the genitalia. Unfortunately, the first character used by Ward (1955: 85) in his key to females is ambiguous and unreliable, making this key not particularly useful.
Saemundssonia (Saemundssonia) gygisa is the second louse species recorded from all subspecies of Gygis alba (Sparrman, 1786), and the first in the suborder Ischnocera (Price et al. 2003 a: 290). The subspecies of Gygis alba breed within the tropical belt of the Pacific, Indian and Atlantic Oceans (Dickinson 2003: 153). In particular, G. alba candida breeds on tropical islands of the Indian and Pacific Oceans, straggling south to the New Zealand region, with several records dating from 1883 until 2002 (Checklist Committee 2010: 234).