Paraergasilus curtus, El-Rashidy & Boxshall, 2001

El-Rashidy, Hoda & Boxshall, Geoffrey A., 2001, Biogeography and phylogeny of Paraergasilus Markevich, 1937 (Copepoda: Ergasilidae) with descriptions of two new species from the gills of grey mullet, Journal of Natural History 35 (12), pp. 1807-1819 : 1811-1813

Paraergasilus curtus n. sp.

(®gure 4)

Type material. Female holotype ( BMNH Reg. No. 1999.1535); four female paratypes ( BMNH Reg. Nos 1999.1536 ±1539) .

Type locality. Socotra, Yemen .

Type host. Liza macrolepis (Smith) .

Record of infected hosts. Liza macrolepis (from Socotra); Valamugil cunnesius Valenciennes (from the Philippines), V. seheli (Forsskal) (from Sri Lanka) and Mugil cephalus (from Western Australia).

Site of infection. Gill rakers.

Etymology. The speci®c name refers to the relatively short second endopodal segment of the antenna.

Description of female

Body small, cephalothorax oval-shaped, without lateral stylets: mean body length 0.33 Ô 0.02 mm, mean body width 0.18 Ô 0.01 mm (n 58). Four pedigerous somites well de®ned, decreasing in width posteriorly (®gure 4A), urosome as in P. dichotomus n. sp.

Antennule, mouthparts and legs 2±5 as for P. dichotomus n. sp. Antenna foursegmented with three curved terminal claws (®gure 4B, C). Coxobasis tapering distally, with inner seta. First endopodal segment about 2.2 times longer than average width, armed with simple spine near middle of medial margin. Second endopodal segment only just longer than wide, apparently lacking spinules on concave margin. Third endopodal segment short, well de®ned, bearing four setal elements including three claws: inner claw bi®d near tip with equal branches, median claw shortest. All claws longer than second and third endopodal segments combined. Simple spinule present at base of median claw.

Leg 1 exopod broad (®gure 4D), but less ¯attened than P. dichotomus n. sp. (®gure 3A). DiOEerences in ornamentation apparent on ®rst endopodal segment (lateral spinules ®ner than in P. dichotomus ), and lateral margins of all exopodal segments with spinule rows in P. curtus . Legs 2±4 as in P. dichotomus .

Remarks

This species is closely related to P. dichotomus n. sp., since it is the only other species that possesses a bi®d claw on the antenna. Both species share the same setation of the swimming legs and the particular shape of leg 1 (®gure 4D), and both belong to the group of species that lack posterolateral stylets on the cephalothorax. The new species diOEers from P. dichotomus n. sp. as follows: it is signi®cantly smaller with a mean body length of 0.33 Ô 0.02 mm compared to 0.47 Ô 0.03 mm in P. dichotomus , the antenna is more robust than in P. dichotomus , having a short, stout second endopodal segment, and the three antennary claws are nearly equal in length, whereas the branched claw is elongate in P. dichotomus . These diOEerences are su cient to justify the establishment of a separate species.