Subhronil Mondal

Predation on Recent Turritelline Gastropods from the Indian Subcontinent and Comparison with a Revised Global Database

ABSTRACT Traces of predation by drilling gastropods and peeling crabs provide important insights about predator-prey interaction in ecological as well as evolutionary times. Predation on turritelline gastropods, in this context, has been frequently discussed in literature. Here, we have estimated the intensity of predation (both drilling and peeling) on Recent turritelline gastropods from the Indian subcontinent, which has been underrepresented in previous studies. Our samples include our own collections from several Indian coasts as well as a vast collection which was locked in the archive of the Zoological Survey of India (ZSI) in Kolkata for the past 150 years. It includes samples from different parts of the Indian subcontinent as well as from many other countries. Drilling frequency (DF) of Indian turritelline species is low compared to average values of global data. We suggest that this is mainly because most of the Indian species are larger (> 4 cm) than species living elsewhere. Smaller species show higher DF and lower values of peeling frequency. Size selectivity of drill holes shows both intra- and interspecific variation. Shell thickness and ornamentation appear to be antipredatory in nature. We have compared our results with a revised global database. Distribution of intensity of predation shows latitudinal variation where both drilling and peeling frequencies increase towards the tropics.

A note on exceptionally high confamilial naticid drilling frequency on Natica gualteriana from the Indian subcontinent

Although common, confamilial naticid predation intensity was not very high in the geological record. Here, we gathered modern confamilial predation data from the Indian coasts and showed that confamilial naticid predation on a naticid species, Natica gualteriana, is exceptionally high at Chandipur, one of our studied areas. We studied the different aspects of confamilial predation from the Indian coasts and showed that the predators in Chandipur were highly efficient as evident from high drilling frequency (DF), site stereotypy and low prey effectiveness. Unusually high DF on N. gualteriana may be attributed to its new arrival in Chandipur where it faced competitive elimination through predation by sympatric naticid predators. Reports of failed invasion are rare. Natica gualteriana is a small invader and therefore its invasion success is threatened by resident populations of large species that extensively drill on young individuals of N. gualteriana just to break the bottleneck of their own offspring from competition.

The Effect of Taxonomic Corrections on Phanerozoic Generic Richness Trends in Marine Bivalves with a Discussion on the Clade's Overall History

Abstract. This study uses a comprehensive, revised, and updated global bivalve dataset combining information from two major databases available to study temporal trends in Phanerozoic bivalve richness: the Sepkoski Compendium and the Paleobiology Database. This compilation results in greater taxonomic and stratigraphic coverage than possible with either of the two databases alone. However, there are challenges in directly comparing these two sources due to differences in their taxonomic designations and stratigraphic range information. Moreover, both of these datasets are fraught with a number of taxonomic errors, which can significantly bias the overall richness estimate. Additionally, a substantial number of taxonomic corrections were made before a new Phanerozoic bivalve richness curve was produced. The new generic taxonomic curve is comparablewith the trajectory of the Sepkoskismodern fauna and shows rapid and substantial diversification through the Ordovician, followed by a Paleozoic plateau, aMesozoic high, and Cenozoic diversification after a small reduction in richness associated with the K/Pg extinction. The steepCenozoic rise documented in the rawrichness curve derived fromthe new dataset is likely real, and reflects the overall robustness and completeness of the bivalve fossil record.

Repair scars on Mactra violacea from the eastern coast of India: A new classification and a model for describing shell breakage on bivalves

Non-lethal shell damage, which is preserved as repair scars on the bivalve shell, can be predatory or non-predatory in origin. When the peeling crabs are the main predatory groups, non-predatory damages are produced by impact from the saltating clasts or by wear and tear during burrowing. In both cases, these repair scars almost look alike, and it is difficult to identify which factor is causally responsible. Because survival of an individual is related to the severity of the shell-break irrespective of the cause, here, we have developed a classificatory scheme to categorize the repaired traces on the basis of intensity of the damage. Moreover, we have provided a model to analyze how the severity of scars can be effectively used to study species’ adaptation against shell breaking causes, by using Mactra violacea as a studied species. Individuals who survive shell breakage may adapt to escalated morphological traits to resist damage in the long term. Subhronil Mondal. School of Geosciences, University of South Florida, 4202 E. Fowler Ave. NES107, Tampa, FL 33620-5250, USA. subhronil.m@gmail.com Subhendu Bardhan. Department of Geological Sciences, Jadavpur University, Kolkata-700032, India. sbardhan12@gmail.com Sumanta Mallick. Department of Geological Sciences, Jadavpur University, Kolkata-700032, India. sumanta.geol87@gmail.com Arindam Roy. Department of Geological Sciences, Jadavpur University, Kolkata-700032, India. addy.geol@gmail.com

Predation on Recent Terebrid Gastropods from the Indian Subcontinent and a Spatiotemporal Reappraisal Based on a Revised Global Database

ABSTRACT Predator-prey interaction, especially drilling and shell-breaking predation pressure, caused significant evolutionary changes within these predator-prey communities. Although temporal trends are well understood in prey assemblages, studies to trace such changes within taxonspecific clades up to Recent times have been rare. Here, we studied both the drilling and shell-breaking predation on Recent terebrid gastropods from the Indian subcontinent and compared the results with a newly updated, global database. The major part of our data came from a large collection reposited in the archive of the Zoological Survey of India in Kolkata for more than 100 years. Detailed analyses of this study based on a newly raised, global database revealed the following findings: (1) Drilling frequency (DF) of Indian terebrids was low, but consistent with the DF of only available but limited data provided by Vermeij et al. (1980). In comparison, peeling frequency (PF) in Indian terebrids appeared to be highest in the world; (2) DF showed latitudinal variation, that is, higher incidence of drilling occurred in higher latitudes; no such pattern emerged from the PF data; (3) drillholes were site-stereotyped, which suggested that Recent naticid drillers were escalated; (4) shell ornaments failed to protect against durophagy; (5) shell shape and thickness had different impact against different modes of predation. While slender and thicker shells were almost immune to drilling predation, no such relation existed for peeling predation; (6) on the other hand, body size appears to have evolved as anti-predatory traits in Recent terebrids. Larger species had low DF and high PF values; (7) temporally, DF showed fluctuating pattern, with modern values showing declining trend. This was perhaps due to increase in body size and behavioural change of the terebrid gastropods. Unfortunately, no peeling frequency data for this clade was available from the fossil record.