Choniosphaera indica Gnanamuthu, 1954

Choniosphaera indica Gnanamuthu, 1954 View in CoL

Host and Location. Portunus pelagicus in Khanh

Hoa, Vietnam.

Material examined and measured. All specimens (n = 5) from an ovigerous female crab (125 mm CW, 17 Mar 2016, locality Nha Trang Bay, collector L. T. K. Oanh) .

Morphological description ( Fig. 4A–C View Figure 4 ). The adult female is seed-like and ellipsoid in outline, size 800 – 1200 µm (1014 ± 67.04) × 400 – 700 µm (552 ± 119.57) (n = 5), and the posterior part projects with the caudal styles. The abdomen is fused with the cephalothorax, and the esophagus occupies most of the abdominal cavity. Choniosphaera indica body is yellow or light pink with two black eyes visible on the head. The cup-like mouth tube is surrounded by the maxillae and the maxillipeds. The mouth is at the bottom of the cup and has a membranous lip( Fig.4A View Figure 4 1 View Figure 1 ). The maxilliped is a long appendage of four unequal segments with the second one longer than the others; it has two short recurved spines and a long, comb-shaped spine on its fourth segment. Two antennas; the first antennae has five articles.The first article bears a spine, the fourth has three spines, and the terminal article carries three spines ( Fig. 4A View Figure 4 2 View Figure 2 ). The second antennae are five-segmented. The third article has a spine, and the terminal article carries two long slender spines ( Fig. 4A View Figure 4 3 View Figure 3 ). The tail forms two branches, assisting attachment to the crab egg ( Fig. 4A, B View Figure 4 ).

Infestation status: Choniosphaera indica occurred with low prevalence (0.29 %), and moderate intensity (20.90 ± 4.97), and was found strictly on the egg mass of the female crab host ( Tab. 2, Fig. 4C View Figure 4 ), no larvae of this species were found.

Remarks. Choniosphaera spp. are specific egg eating parasites on decapod crabs. Three species have so far been recorded ( Costello et al., 2001; Connolly, 2010), and among them C. indica is the most common. Choniosphaera indica was previously reported on Portunus pelagicus ( Shields, 1992; Vo et al., 2013), and considered as a significant contributor to mortality of the crab host, and affecting the host population ( Shields and Wood, 1993). Despite being one of the parasites capable of affecting the portunid host species population, no gene sequence of this species is available on GenBank for reference. The present study provides descriptions and images of this species, and also registers two gene sequences(28S rRNA and COI mtDNA) into GenBank.