On Some Gas trocoty line (Monogenoidean) Parasites of Indian Clupeoid Fishes ? 
Including Three New Genera 
R. VlSWANATHAN UNNITHAN 1 
ABSTRACT: Seven species of monogenetic trematodes, including the two geno- 
types, Engraulicola forcepopenis George, 1961 and Engraults cohtna thru socles 
(Tripathi, 1959), are recorded. All seven of these atypical gastrocotylines belong 
to the subfamily Gastrocotylinae s.s. and are parasitic on clupeoid fishes. Four 
species in the present collection, viz., Engraulicola micropbaryngella sp. n., 
Engraulixenus malabaricus gen. et sp. n., Engrauliphila grex gen. et sp. n., and 
Engraults cobina triaptella sp. n., were collected from fishes of the family En- 
graulidae, while an entirely new type, Pellonicola elongata gen. et sp. n., was 
obtained from Clupeidae. The tendency to unilateral inhibition of the clamp rows 
is incomplete in all these atypical gastrocotylines, and all are characterised primarily 
by their clamp structure. Diagnostic characters, with special reference to the hap tor 
(its adhesive units or clamps and anchors), the male terminalia, vaginal complex, 
and other salient features which appear 
for each species. 
Some gastrocotylib worms have been found 
on the gills of clupeoid fishes at Mandapam 
Camp. Their clamp structure shows them to 
be allied to Gastrocotyle and Pseudaxine . The 
tendency to develop a unilateral haptor is 
another common feature. But of the 32 known 
species of Gastrocotylidae, and 8 new species 
described by me (in press), all 40 are parasitic 
on scombroid fishes (including Carangidae). 
Indeed, it is usual to find these more highly 
evolved Monogenoidea on the more highly 
evolved fishes, while the simpler clupeoids are 
typically parasitized by Mazocraeidae. The oc- 
casional excursions across the phylogenetic 
trees of the hosts for each of these families of 
parasites have been discussed by Sproston (in 
press). The present collection adds support to 
her hypothesis, since it contains four new forms 
from Engraulidae and one entirely new type 
from Clupeidae. Collection and treatment of 
specimens was performed as described in a 
previous paper (Unnithan, 1957:28-29). 
1 Indian Ocean Biological Centre, Ernakulam-6, 
India. Formerly research student in the Marine Bio- 
logical Laboratory of the University of Kerala, Tri- 
vandrum, and at the Central Marine Fisheries Re- 
search Institute, Mandapam Camp, where most of 
this work was done. Manuscript received March 8, 
1966 . 
to be taxonomically important, are given 
All of these atypical clupeoid parasites 
belong to the subfamily Gastrocotylinae sensu 
stricto , hitherto containing only Gastrocotyle 
v. Ben. et Hesse, 1863, Chauhanea Ramalin- 
gam, 1953, and Y amaguticotyla Price, 1959= 
They are characterized primarily by their damp 
structure (Unnithan, 1961b). There are paired 
braces in the posterior region of the clamp 
capsule, as in all Gastrocotyloldea (as distinct 
from Microcotyloidea), but the clamps them- 
selves are bilaterally symmetrical; and, unlike 
the subfamily Priceinae, for instance, to which 
Pseudaxine belongs, there are no complex dorsal 
shields to other sclerites developed in the dorsal 
wall of the capsule in association with the 
median spring, nor are there riblike thickenings 
in the capsule walls. While in Gastrocotyle spp. 
the ventral arm of the spring is often doubly 
bifid, its ends sometimes form articulated stmts 
to the jaw rami. This condition is not found in 
the other genera. In all of them (with the 
doubtful exception of Chauhanea and Y amagu- 
ticotyla), the dorsal arm of the spring bears a 
forked appendix associated with noncuticula- 
rized ligaments, presumably a transitional condi- 
tion to that in Priceinae. 
The tendency to unilateral inhibition of the 
clamp rows is complete in Gastrocotyle spp. 
(also in Pseudaxine in Priceinae and in some 
210 
