Description of Elthusa aquabio sp. n. (Crustacea: Isopoda: Cymothoidae), a branchial fish parasitic isopod from Indian waters Author Aneesh, Panakkool Thamban Author Helna, Ameri Kottarathil Author Raj, Smrithy Author Kumar, Appukuttannair Biju text Journal of Natural History 2023 2023-08-17 57 21 - 24 1193 1205 http://dx.doi.org/10.1080/00222933.2023.2242099 journal article 264212 10.1080/00222933.2023.2242099 d9d90eef-7b56-4196-a161-4fbdc607dddd 1464-5262 8270960

Table 1. Inter-specific characters of Elthusa aquabio sp. n., Elthusa fistularia, E. pseudorhombus, and E. uranoscopus, described from Indian waters.

				E. uranoscopus
		E. pseudorhombus	E. fistularia Aneesh,	Aneesh, Helna,
		Aneesh, Helna, Kumar	Helna, Kumar and	Kumar and Trilles,
Character	E. aquabio sp. n.	and Trilles, 2020	Trilles, 2020	2020
Cephalon	1.20 times wider than	1.7 times wider than	1.2 times wider than	1.6 times wider than
	long	long	long	long
Coxae	Coxae 2–4 very narrow,	Coxae 6 and 7 longer	Coxae 6 equal to	Coxae 6 and 7, flat,
	slightly visible in	than the pereonites,	pereonite, 7,	broad, longer than
	dorsal view, much	coxae 7 overlapping	extending	the corresponding
	shorter than	lateral margin of	beyond, coxae 6–	pereonite;
	pereonites; coxae 5–	pleonite 1–2	7 posteroventral	posteroventral
	7, flat, broad,laterally	posteroventral angles	angles broadly	margin rounded
	expanded, 5 nearly	acute	rounded
	as long as pereonite,
	6–7 longer than the
	pereonites
Antenna	With 10 articles	With 10 articles	With 9 articles	With 11 articles,
				slightly longer
				than antennula
Pleon length	~16% BL	~14% BL	~15% BL	~16% BL
Ratio of maximum	0.75	0.75	0.80	0.84
pleon width to
maximum
pereion width
Pleonites	Pleonite 3 widest	Pleonite 4 widest	Pleonite 2 widest	Pleonite 3 widest
Pleotelson	Broadly round, 2.0	Evenly rounded, 1.5	Broadly round, 1.7	Pleotelson 1.8 times
	times as wide as long	times as wide as long	times as wide as	as wide as long,
			long, lateral	lateral margins
			margins convex	convex
Rami	Endopod 1.05 times as	Endopod 0.8 times as	Endopod as long as	Endopod 1.3 times
	long as exopod	long as exopod	exopod	longer than
				exopod
Pereopod spines	Pereopods 1–3	Absent	Absent	Absent
	propodus inner-
	lateral margin with
	few robust spines