Abstract
Specimens of a new species of Rhadinorhynchus Lühe, 1911 are described from the chub mackerel Scomber japonicus (Scombridae) and the Chilean Jack mackerel Trachurus murphyi (Carangidae) (possibly a subspecies of Trachurus symmetricus) from the Pacific Ocean off the Peruvian coast at the Port of Chicama, La Libertad. Specimens of Rhadinorhynchus oligospinosus n. sp. are somewhat small having 11–14 rows of alternating proboscis hooks with 20–22 hooks each with posteriormost hooks in a continuous ring. Ventral hooks are robust with prominent roots but dorsal hooks are slender and shorter with discoid roots. Trunk spines are in two zones separated by a non-spiny region. Anterior trunk spines are in 2–3 complete circles but posterior spines are only ventral and lateral, and do not extend posterior to the level of the posterior end of the proboscis receptacle in both sexes. The new species is closest to Rhadinorhynchus seriolae (Yamaguti, 1963) Golvan, 1969 found in Japanese and Australian waters, but not as close to 19 other species found in the same Pacific waters off Australia, Japan, and Vietnam. In R. seriolae, posterior trunk spines extend well past the receptacle in females, among other diagnostic differences. Proboscis hooks of the new species were analyzed for chemical elements using X-ray in conjunction with EDAX (energy-dispersive analysis for X-ray) software; sulfur had a higher concentration at the edge than the middle of cut hooks.
Highlights
An increasing number of research publications on the acanthocephalan parasites of marine fishes in the east Pacific Ocean off the coast of Peru have made their appearance in the past few years
Oliva et al [29] reported on the ecology of metazoan parasites of Stellifer minor (Tschudi), Tantaleán et al [38] surveyed the acanthocephalans of Peru, and Amin et al [3] redescribed Rhadinorhynchus ornatus Van Cleave, 1918 from skipjack tuna, Katsuwonus pelamis (Linn.) with special reference to the presence of microtriches on its trunk, Cruces et al [8] reported on the parasites of the chub mackerel, Scomber japonicus Houttuyn off Peru, and Minaya et al [24] discussed the community of parasites of the Peruvian weakfish, Cynoscion analis (Jenyns) from the Peruvian Pacific
Trachurus murphyi has been identified in the South Pacific off the coasts of Chile, Ecuador, and Peru, and around New Zealand and South Australia [1, 7, 39]
Summary
An increasing number of research publications on the acanthocephalan parasites of marine fishes in the east Pacific Ocean off the coast of Peru have made their appearance in the past few years. The parasitic fauna of Trachurus murphyi Nichols or Trachurus symmetricus murphyi Nichols is rarely reported; see Oliva [27, 28] who reported no Rhadinorhynchus in Peruvian or Chilean waters and George-Nascimento [12] who reported Rhadinorhynchus trachuri Harada, 1935 off Chile. Our studies from S. japonicus and the Chilean Jack Mackerel Trachurus murphyi Nichols in the Peruvian Pacific revealed the presence of a new species of Rhadinorhynchus. The latter fish species is considered a subspecies of Trachurus symmetricus Ayres by many [9, 10, 31]. Re-examination of the Acanthocephala of S. japonicus and T. murphyi with the aim of correcting previous records would be highly desirable
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