Shiinoa occlusa Kabata 1968

Shiinoa occlusa Kabata, 1968

Shiinoa occlusa Kabata, 1968a:497.

MATERIAL EXAMINED.—21 collections containing 41 11 from the nasal lamellae of the following hosts and localities: Grammatorcynus bicarinatus from North Celebes, Solomon Islands, Palau, Caroline Islands; Gymnosarda unicolor from Solomon Islands; Scomberomorus commerson from Mozambique, Pakistan, Gulf of Thailand, Solomon Islands, Philippines, Palau; S. guttatus from China; S. niphonius from Japan; S. queenslandicus from Papua; S. tritor from Canary Islands; Acanthocybium solandri from Kapingarmarangi Atoll.

When Kabata described this species he stated that his description was based on an immature female. The first author examined that specimen during the course of another study and compared some of the present material with it. It was concluded that Kabata's specimen was a nonovigerous female adult. We have found no differences between the specimens reported here and Kabata's description except for the presence of egg sacs on some of our specimens. We will point out the differences between this species and S. inauris rather than repeat a full description here. We have, however, provided several SEM photographs of a female S. occlusa (from Gymnosarda unicolor). Females of S. occlusa can be distinguished from S. inauris by the following: the abdomen of S. occlusa is about one-sixth of the total body length (one-third in S. inauris); the exopods of legs 1 and 2 of S. occlusa are 3-segmented (2-segmented in S. inauris). Males of the 2 species can be separated by the following characters: distal segment of the second antenna of S. occlusa with 3 clawlike terminal spines (a bifid claw in S. inauris); 3-segmented exopods of legs 1 and 2 of S. occlusa (2-segmented in S. inauris); 2 stout, but unequal, spines at tip of leg 2 exopod of S. occlusa (1 stout spine in S. inauris).

MATERIAL EXAMINED.—138 collections containing 316 and 281 from the body surface and gills of the following hosts and localities: Acanthocybium solandri from northeast coast of Malagasy Republic, Auxis species from Gulf of Guinea; Euthynnus alletteratus from Puerto Rico (Atlantic); Katsuwonus pelamis from northwest Malagasy Republic, Christmas Island (Pacific), Peru, Ecuador, east coast of United States (several localities), Puerto Rico (Atlantic), Venezuela, Brazil (north coast), Cape Verde Islands, Gulf of Guinea; Thunnus alalunga from New Jersey; Thunnus albacares from Christmas Island (Pacific), east coast of United States (several localities), Brazil, Gulf of Guinea; Thunnus atlanticus from Puerto Rico (Atlantic); Thunnus obesus from Christmas Island (Pacific), east coast of United States (several localities), Surinam, Brazil (north coast), Cape Verde Islands; Thunnus thynnus from east coast of United States (several localities).

Shiino (1959a), Pillai (1962b), and Lewis (1967) have provided good descriptions and figures for this well known species. We will restrict our consideration of this species to those characters that serve to distinguish it from the other Caligus species found on scombrid hosts.

FEMALE.—Body form as in Figure 40a. Lewis, et al. (1969:423) provided morphometric data for 36 specimens from 4 host species from the Indian Ocean. The average total length for his material was 5.57 mm. Our material from the Indian Ocean and Pacific areas did not differ significantly from this mean. The Atlantic specimens, however, tended to be larger (5.8–6.5 mm based on 10 specimens from various localities). The cephalon comprises about one-half of the total length with the genital segment and abdomen each comprising about one-fourth.

Frontal lunules widely spaced; space between lunules (1.31 mm) more than twice greatest diameter of either lunule (0.58 mm).

Genital segment slightly longer than wide (1.5 × 1.4 mm) with posterior outer corners produced somewhat beyond origin of abdomen. Abdomen 3-segmented; 1st segment constricted in posterior two-thirds giving the appearance of 2 segments, second segment shortest, third segment with 2 distal lobes separating caudal rami; segments measure 0.9, 0.3, and 0.37 mm respectively. Caudal ramus as in Figure 40b.

Postantennal spine lacking. Postoral spine wide at base, triangular. Sternal furca (Figure 40c) with short, widely divergent tines; furca with an accessory sclerotized cuticular process on each side.

Leg 1 (Figure 40d) basipod with a patch of short spinules, patches of longer hairs, a short plumose seta on inner margin, a long, very plumose, seta at outer distal corner; exopod 3 distal spines each with prominent fringes, inner 2 with accessory process; endopod reduced to a short, sclerotized process. Leg 2 endopod (Figure 40e) with patches of long spinules on outer margin of each segment. Leg 3 exopod (Figure 40f) with prominent thumblike spine on outer distal corner of first segment, each of last 2 segments with long setules on outer margin in addition to usual spines and setae. Leg 4 exopod (Figure 41a) 3-segmented, first and second segment each with a prominent fringed spine on outer distal corner; last segment with 3 fringed spines, distalmost longest, all spines with a fringe at base; spines measure 366, 236, 153, 206, and 247 μ distalmost to proximalmost respectively.

MALE.—Body form as in Figure 41b. Total length 5.3 mm. Cephalon comprises more than half total length. Appendages as in female except second antenna with accessory process on claw. Maxilliped with small sclerotized area opposite tip of claw. Sternal furca similar to female except tines not quite as divergent. Thoracic appendages as in female. Legs 5 and 6 represented by setae at the posterior corners of the genital segment.